AF 447 Thread No. 5

[PJ2]

I would like to add to the discussion on "Why the pitch up?" by quoting from and otherwise referencing from two sources - HtBJ by Davies, (1rst & 3rd ed, discussion on the "super-stall"), and from one of the papers to which I provided links a while back on this thread, entitled, "The Effect of High Altitude and Center of Gravity on the Handling Characteristics of Swept-wing Commercial Airplanes (http://www.boeing.com/commercial/aeromagazine/aero_03/xtras/about/index.html)" published in the "Flight Operations" [FO] section in the April, 1998 issue of Boeing's AERO magazine.

The goal here is "continuing education" if you will, because the serious discussion on stalling heavy transport aircraft has become necessary as have some points regarding high altitude, high Mach number flight. There are some worthwhile papers which discuss this in great detail but are really tough sledding and the mathematics will be beyond most! I can't lead the discussion as HN39, gums and others might but I do wish to rejuvenate the discussion on the two items which continue to interest us all: Why the initial pitch up?, and the behaviour of a heavy transport aircraft in approach to, and in, the stall. Specifically, I am wondering if the low-damping forces of high altitude flight had anything to do with the eventual loss of control. - PJ2

First, from the Boeing document:

"Maneuvering Stability
"Maneuvering stability, like static stability, is influenced by CG location. However, when the CG is aft and near the neutral point, then altitude also has a significant effect. Since air density has a notable impact on the damping moment of the horizontal tail, higher pitch rates will result for the same elevator deflections as altitude increases. From the flight crew's perspective, as altitude increases, a pull force will result in a larger change in pitch angle, which translates into an increasing angle of attack and g. While a well-designed flight control system, either mechanical or electronic, will reduce the variation of stick force with CG and altitude, it is very difficult to completely eliminate the variation due to design limitations.

"For example, for the same control surface movement at constant airspeed, an airplane at 35,000 ft (10,670 m) experiences a higher pitch rate than an airplane at 5,000 ft (1,524 m) because there is less aerodynamic damping. The pitch rate is higher, but the resulting change in flight path is not. Therefore, the change in angle of attack is greater, creating more lift and more g. If the control system is designed to provide a fixed ratio of control column force to elevator deflection, it will take less column force to generate the same g as altitude increases.

"This principle is the essence of high-altitude handling characteristics for RSS airplanes. Unless an RSS airplane has an augmentation system to compensate its maneuvering stability, lighter column forces are required for maneuvering at altitude. Longitudinal maneuvering requires a pitch rate, and the atmosphere provides pitch rate damping. As air density decreases, the pitch rate damping decreases, resulting in decreased maneuvering stability (see figure 2 and "Maneuvering Stability" below (http://boeing.com/commercial/aeromagazine/aero_02/textonly/fo01txt.html#Fig2)).

"An additional effect is that for a given attitude change, the change in rate of climb is proportional to the true airspeed. Thus, for an attitude change for 500 ft per minute (fpm) at 290 knots indicated air speed (kias) at sea level, the same change in attitude at 290 kias (490 knots true air speed) at 35,000 ft would be almost 900 fpm. This characteristic is essentially true for small attitude changes, such as the kind used to hold altitude. It is also why smooth and small control inputs are required at high altitude, particularly when disconnecting the autopilot.

Summary
"The use of wing sweep and stability augmentation on modern commercial airplanes makes them more fuel efficient. However, flight crews must understand the effects of CG and altitude on performance and handling qualities. For example, operating at an aft CG improves cruise performance, but moving the CG aft reduces static longitudinal and maneuvering stability. Many modern commercial airplanes employ some form of stability augmentation to compensate for relaxed stability.

"However, as long as the CG is in the allowable range, the handling qualities will be adequate with or without augmentation. An understanding of static and maneuvering longitudinal stability is an essential element of flight crew training." (my bold/underlining).

. . . .

"Static Longitudinal Stability and Speed Stability
"STATIC LONGITUDINAL STABILITY
"The term "static longitudinal stability" is the name of the stability coefficient (Cm-alpha) for the pitching moment due to a change in angle of attack. In a stable, conventional airplane, the CG is forward of the neutral point of the airplane (wing plus tail). An increase in angle of attack from trim increases the amount of lift generated by the wing and results in an increasing pitch-down moment. This drives the airplane back toward its original angle of attack. If the CG is aft of the neutral point, increasing the angle of attack causes the airplane to pitch up, away from its original trimmed condition."



Next, from Davies; (NOTE 1: We have seen some of these illustrations from Davies before, posted by others during discussions on AoA, the stall and so on. I am providing pages 121 through 128. By referencing the so-called "deep stall", I am not implying that we have such here in AF 447 - I don't have the background to determine that. What I wish to provide is Davies' discussion on the broader elements of the deep stall, a discussion which I think is relevant to the behaviour of a heavy transport, regardless of kind of AFS installed. NOTE 2: "Cm" is referenced in the last paragraph of the Boeing document, above.

*Handling the Big Jets, D.P.Davies. 3rd ed. 1971. Civil Aviation Authority, London (OP)

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[Shadoko]

Hi,
Numerous issues are raised, including simulator training and management, but nowhere in the article does the word "securitie" in the safety sense get a mention.

The word is not there, but the idea is: the "audit" about security has NOT been published (contrary to promises, imho). There were some comments (in French, and I am not sufficiently fluent in English to translate them):
- SÉCURITÉ - Ce rapport qui pointe les failles d'Air France - Le Point (http://www.lepoint.fr/societe/securite-ce-rapport-qui-pointe-les-failles-d-air-france-26-01-2011-131935_23.php)
- L'audit sur la scurit des vols d'Air France serait "trs critique" - LExpansion.com (http://lexpansion.lexpress.fr/entreprise/l-audit-sur-la-securite-des-vols-d-air-france-serait-tres-critique_247566.html)

[ChristiaanJ]

PJ2,
Thanks.
Can't find my own copy of Davies's HtBJ to cross-check. Is he discussing T-tails in that section you posted?

[ChristiaanJ]

jcjeant, mm43,
The 'La Dépèche' article seems to have been written by somebody who's either followed the PPRuNe threads on the subject..... or similar ones on French forums.
Nothing new there, and just the same speculations we've seen before.
I wouldn't pay too much attention to it.

[RetiredF4]

Excellent post and reference , PJ2.

It´s basically what i learned in the aerodynamics-course in UPT 35 years ago, also in view of flying fighter jets. I didn´t learn anything in my ATPL course concerning this matter, but maybe i was not attentive enough.

I had some argument via PM with some posters here about how much the nose would have to be lowered to break the stall at an AOA of 60° and posted some concern to the effectiveness of the THS. This reference states that it is not enough to lower the nose somewhat, and that it would lead to high sink rates and a difficult pullout if altitude would be sufficient. Posters calculated altitude loss to some 5.000 feet. Please, go back and read this reference from PJ2 and reconsider your calculation.

I get the impression that this new generation of engineers and pilots are forgetting, that computers dont change aerodynamic fundamentals, they only can help in manage the equipment being used in a different way. But its still used in the same old environment from years ago, when your nice reference was written down, and even before, when the fathers of flying conquered the skies.

Aerodynamics is unchanged, any aircraft can stall, can be stalled, and any aircraft can end in an unrecoverable mode of stall or spin. Know before, when it could happen and under what conditions it can happen, and dont get near such an situation. If you fail and find yourself approaching a stall, try to get out of it as fast and efficient as possible. There might be only this one chance.

[DozyWannabe]

Protect the integrity of Airbus Industries and make Air France and its employees the "sacrificial lamb" is my read on this Irène Perrin article.

Why would you say that? Airbus acknowledged the pitot issue and released a service bulletin to the airlines months before the accident and simultaneously issued "workaround" instructions to pilots at the same time, while the issue was being fixed. What more could they reasonably have done?

I really don't get this "BEA protecting/covering up for Airbus/AF" meme that seems to have seeped in around the edges. The fact is (as I've said before) that not only has the BEA become a very different organisation than it was in the late '80s, but also that Airbus has been very quick to put its hand up to mistakes and fix them. Neither major manufacturer acquitted themselves particuarly well in the '80s and '90s - it took definitive proof that the 737 rudder hardovers had a technical cause before Boeing stopped pushing the angle that UA535 and USAir427 could have been pilot error, and it took the loss of Nick Warner to make Airbus look long and hard at their interface design. Both companies have since behaved considerably better in that regard.

We could be on the verge of a serious self-examination on the part of the airline industry as regards training, particularly with regard to making sure that pilots be properly-versed in the aspects of the aircraft they are expected to fly - which I gather from many posts on here people think is something long overdue, and yet it would appear that some people still think that finding the design of the aircraft (over and above the pitot issue) at fault in the face of the evidence would be a better outcome?

@CJ - yes, I'm pretty sure that sectoin of the book refers to deep stall in T-tail designs, but the thrust of the description is still very useful.

[PJ2]

Hello, CJ;

Yes, that's the section he's discussing: - T-tails and the "super-stall" and the section I have quoted comes right after that specific discussion, (pgs 115 - 120).

I understood his discussion on "the complete picture" at the beginning of page 121 to be relevant to all heavy transport types and not specific to the T-tail configuration, which is why I considered it pointing to what constitutes a "good education for pilots new to high altitude, high Mach number flight", if nothing else.

I'm no longer confident:
a) that this knowledge is taught either on the way to the ATPL or to new-hire pilots on the assumption that they already know it all and,
b) that the "assumption" is correct.

Edit: Thanks Retired F4 - confirms my sense of what's being taught and what is being assumed.

I get the strong sense that Davies' approach to matters of aviation and in particular heavy transport flight, is unfamiliar today, not because today's pilots are less keen and less interested in their profession but because bean-counting airline executives believe that "all today's airplanes are automatic" and so teaching things aeronautical as opposed to teaching the minimum "NTK", (need-to-know) to operate the airplane and pass the FAA/TC/JAR (haven't included Australia here, yet), rides has contributed to the present state of affairs and pilots, as a group, have let management get away with this brand of thinking and haven't taken the bull by the horns because many don't know what they don't know about flying airplanes. Just because one can manipulate the controls and land the thing doesn't mean one "knows stuff". The First Officer of the Colgan Q400 is sadly, tragically, one example. The poor soul was never taught about the business she was in or bread-and-butter aerodynamics, just the NTK about how to work the airplane.

[jcjeant]

Hi,

mid-'90s and the 777 has suffered only a single hull-loss, as has the A340 in service).To remind that the loss of BA 777 (in England) was (as far know) due to a technical problem .. and the loss of AF A340 (in Canada) was (as far know) a pilot error.

[jcjeant]

Hi,

jcjeant, mm43,
The 'La Dépèche' article seems to have been written by somebody who's either followed the PPRuNe threads on the subject..... or similar ones on French forums.
Nothing new there, and just the same speculations we've seen before.
I wouldn't pay too much attention to it.

Can we qualify the famous "audit report" as speculations ?SÉCURITÉ - Ce rapport qui pointe les failles d'Air France - Le Point (http://www.lepoint.fr/societe/securite-ce-rapport-qui-pointe-les-failles-d-air-france-26-01-2011-131935_23.php)

As far we know .. BEA not issued a grounding of all the A330 after all those days of investigations
We can conclude that at today the A330 is not technically implicated in any ways in the loss of the AF447
So with this knowledge .. we can conclude that the BEA final report will show that the actions of the pilots where not adequate for the situation the plane was.
It's maybe not name the responsibles .. but it's indicate a way to investigate more ....
Wonder what will be the final recommandations (to Airbus-AF and responsible bodies .. DGAC .. etc ...)

[john_tullamarine]

If ice is the trigger for a fault in the function of static ports, what sort of evidence does that leave behind?

I can't recall any event where static icing was implicated and would be surprised to see icing problems at the static location if that be on the aircraft keel surface. As to evidence, like most icing, the evidence of a single event melts with the ice ...

The 737 proved that it wasn't as longitudinally stable as the 727 (unlike the 727 you couldn't rescue a fast approach by throwing the gear out early)

Saved more than a few hot/high approaches (don't we all love ATC track shortening ?) by reconfiguring early - if necessary back to final approach configuration well out to improve the descent angle to something better than a mile a thousand. Or have I missed your point here ?

[DozyWannabe]

To remind that the loss of BA 777 (in England) was (as far know) due to a technical problem .. and the loss of AF A340 (in Canada) was (as far know) a pilot error.

I wasn't going to make that distinction, as it's not important to the point I was making (early-life crashes that highlight airframe "quirks" are often written up as pilot error), but if you want to make that call, then go ahead.

Saved more than a few hot/high approaches (don't we all love ATC track shortening ?) by reconfiguring early - if necessary back to final approach configuration well out to improve the descent angle to something better than a mile a thousand. Or have I missed your point here ?

I was referring to a document I read on 737 handling back when I had time to muck around with sims (the document referred to the real 737 however) - from memory it said something about some pilots trying some of the tricks they'd used on the 727 getting a nasty (albeit recoverable) surprise when they tried them on its little sister. I'm pretty sure "throwing out everything except an anchor" was one of those tricks...

[ChristiaanJ]

Hi,
Can we qualify the famous "audit report" as speculations ?SÉCURITÉ - Ce rapport qui pointe les failles d'Air France - Le Point (http://www.lepoint.fr/societe/securite-ce-rapport-qui-pointe-les-failles-d-air-france-26-01-2011-131935_23.php)Since your link dates from January 2011 and since we have seen no serious trace of that 'audit report' since... I don't quite understand what we are supposed to make of it.

[john_tullamarine]

I'm pretty sure "throwing out everything except an anchor" was one of those tricks...

All my jet time is 727/737 and I can't say that I recall any problems in this arena save that the 737 required more planning due to its useless speedbrakes - the 727 was a much more readily versatile aeroplane ..

[mm43]

DozyWannabeWhy would you say that? Airbus acknowledged the pitot issue and released a service bulletin to the airlines months before the accident and simultaneously issued "workaround" instructions to pilots at the same time, while the issue was being fixed. What more could they reasonably have done?Did I say anything derogatory of Airbus, or imply a BEA cover-up? I can't see where I did. My comment was that the article in question had singled out Air France and the crew as being responsible before the BEA has released its final report - a long way off (time wise) methinks.

So don't get me wrong DW, I am not bashing Airbus and never have. My comments were reflecting the content of the article.

CJ - Agree.

[Machinbird]

I had some argument via PM with some posters here about how much the nose would have to be lowered to break the stall at an AOA of 60° and posted some concern to the effectiveness of the THS. This reference states that it is not enough to lower the nose somewhat, and that it would lead to high sink rates and a difficult pullout if altitude would be sufficient. Posters calculated altitude loss to some 5.000 feet. Please, go back and read this reference from PJ2 and reconsider your calculation. Retired F-4, as a fellow Phantom Pflyer, I think we both appreciate that it would likely take 10, 000 feet and more to recover AF447 from its deep stall. Until the AOA was reduced, it would not accelerate, and it would take a bit of time to run the trim down far enough to recover. If the recovery took more than 20,000 feet, it would be because the nose was left down too long after it began flying. Availability of airspeed in the recovery would be very beneficial (since there is no AOA gauge .)

PJ2, AF447 may have been a bit 'goosey' at altitude but to actually get and keep the nose well in the air as AF447 did implies more a lack of awareness (scan or instrument problem) than a control difficulty based on the limited information released. (There seems to be no indication of a dynamic departure from controlled flight for example.). There seems to have been adequate control authority to put the aircraft in a level attitude.

More like PF expecting the aircraft to take care of pitch attitude without the need to scan while attention is diverted elsewhere. Of course, this is just my personal opinion, and I await the BEA interim report to shed more light on what is presently poorly understood by those of us on the outside.

[grity]

A33Zab

In Flight:

The FMGC uses the weight and center of gravity from the FCMC (Fuel Computer) when available.
The GW and CG computed by the FE part are used:
– as back-up in case of dual FCMC failure.
– to trigger the aft CG caution and warning signals (independently of the FCMC).
FE Weight computation (back up)
– When the aircraft is below 14625 feet and 255 knots :
GW = f(α, CAS, N1/EPR actual, CG from FE part, altitude)
– When the aircraft is above 14625 feet or 255 knots :
GW = TOGW − WFU
TOGW: takeoff gross weight
WFU: weight fuel used acquired from FADECs.
FE Center of gravity computation (back up/aft cg computation)
The CG is computed from the position of the horizontal stabilizer and is
function of the N1/EPR, Vc, ALT, MACH and GW from FE part.
thank you for detailed explanation A33Z

so in case of wrong CAS, MACH or ALT datas, what may be the result or the following aktion for the the FE Weight or Ceneter of gravity computation ??? in which direction will he put the wrong datas in his calculation? will he start pumping more fuel back or forward if the bird fly in level 350 with a (mayby) wrongly indicated CAS <255 ?

[PJ2]

Machinbird;

Thanks, I don't disagree frankly. I'm just trying to find something outside the box to figure out why someone would point an A330 15deg NU and keep it there at FL350+ and these papers got me thinking. I've flown the aircraft at altitude and I must say it was pretty responsive in pitch and roll in Normal Law. I've always doubted the notion that the airplane was slow and 'slushy' to respond to the stick at altitude and that a bit of PIO or inadvertent backstick while controlling roll resulted in an "accidental" climb that continued to 38,000ft but I'm outa ideas!

[Machinbird]

.......and that a bit of PIO or inadvertent backstick while controlling roll resulted in an "accidental" climb that continued to 38,000ft but I'm outa ideas!Me too PJ2! I hope BEA is able to get to the crux of the problem. The CVR will be key in this.

[A33Zab]

so in case of wrong CAS, MACH or ALT datas, what may be the result or the following aktion for the the FE Weight or Ceneter of gravity computation ??? in which direction will he put the wrong datas in his calculation? will he start pumping more fuel back or forward if the bird fly in level 350 with a (mayby) wrongly indicated CAS <255 ?


Transfer CG control is another question, pls read the first sentences:


In Flight:

The FMGC uses the weight and center of gravity from the FCMC (Fuel Computer) when available.
The GW and CG computed by the FE part are used:
– as back-up in case of dual FCMC failure.



TRIM TRANSFER CONTROL

Before each flight, the crew inputs the A/C Zero Fuel Center of Gravity
(ZFCG) and Zero Fuel Weight (ZFW) data into the Flight Management
Guidance and Envelope Computers (FMGECs) via the MCDU.
The two FMGECs independently transmit this data to the FCMCs.
Each FCMC uses the ZFW from the FMGECs and the tanks fuel weight
to calculate the A/C Gross Weight (GW).
This GW is output to the ECAM FUEL page, and is used, in the FCMCs, to
obtain the target CG from the memorized CG versus percentage of Mean
Aerodynamic Chord (MAC) CG table.
In the same time, the FCMCs calculate the fuel weight CG using the FQI,
the pitch, roll and acceleration data from the Air Data Inertial Reference
Units (ADIRUs) 1 and 2, and the THS position from the Flight Control
Data Concentrators (FCDCs).
Then, with the ZFWCG transmitted by the FMGECs and the fuel weight
CG, the FCMCs calculate the Gross Weight Center of Gravity (GWCG).
This GWCG is output to the ECAM FUEL page.
The FCMCs, in their transfer logic part, compare the GWCG with
the target CG to determine if a FWD transfer or an aft transfer is needed.

CG control during automatic operation:
The master FCMC has full control of the A/C CG when the A/C is above
FL255, until the A/C descends below FL245.
The FMGEC independently monitors the CG of the A/C.
If it detects that the A/C CG is too far aft, it sends a signal ''CG target FWD'' to the FCMCs.
The master FCMC moves the target CG forward 2.0% MAC.
This is latched until the end of the flight.
If the FMGEC detects that the CG is still aft of the new target CG, it
sends a signal to the FCMCs.
The FCMCs then move the target CG forward 0.5% MAC for 10 minutes.
After 10 minutes the system goes back to normal operation.
This procedure can occur twice more until the target CG is first 4.0%
then 6.0% MAC forward of the initial position.
If the error is detected again, the FCMC stops the CG control and shows
an ECAM warning to the crew.
The crew then manually sets a forward transfer.

FCOM figure Posted earlier by Takata: LINK (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-21.html#post6577222)
http://takata1940.free.fr/fcms7.jpg

[DozyWannabe]

So don't get me wrong DW, I am not bashing Airbus and never have. My comments were reflecting the content of the article.

My apologies - as I have said many times, the man or woman who invents a "tone-of-voice" reader for internet forums will make themselves a fortune...

[airtren]

Thanks for posting several articles that provide very useful information about flying an A/C of this kind.


...I've always doubted the notion that the airplane was slow and 'slushy' to respond to the stick at altitude and that a bit of PIO or inadvertent backstick while controlling roll resulted in an "accidental" climb that continued to 38,000ft but I'm outa ideas!

PJ2
One element that drew my attention in the last article you've posted was the mentioning that the A/C reaction to pitch and roll commands is amplified at high altitude.
...

Regarding the climb from FL350 to FL380, there are several elements in the BEA text (marked in italic, and/or color) that attracted my attention, and perhaps are worth mentioning:

Sometime between 1:59:32 and 2:01:46, the PF said, “…turbulence that you just saw…. We’re in the cloud layer unfortunately we can’t climb much… because the temperature is falling more slowly than forecast… and the logon with Dakar failed”.

The text marked in blue can be considered as implying that going to a higher flight level, above FL350, was considered as a possible solution, had the air temperature and the Dakar logon been OK.

At 2:08:07 PNF said “you can maybe go… to the left” airplane …. change ….about 12 degrees possibly because the increasing turbulence …. The level of turbulence increased … the crew reduce the speed to about Mach 0.8.

At the moment the A/P and A/THR disconnected, at 2:10:05, the A/C needed a correction command, and I think it is also possible that the PF thought, that it is worth trying to go at a higher flight level - we don't know if the air temperature may have decreased?

The BEA text indicates that the A/C climbed (from FL 350 and speed 275 kt) while rolling left and right between 12 and 10 degrees to FL 375, at which time the speed on the Left indicator increased (came back) to 215 kt, Mach 0.68, and the AoA was of 4 degrees (with stall warning stopped).

Based on the vertical speed of 7000ft/min mentioned by the BEA's text, the A/C climbed the 2500 ft to FL 375 in about 20 seconds, which left about another 20 seconds of flying approximately at this FL375 and A0A of 4 degrees, before the stall warning was triggered again at 2:10:51.

Note the left speed indicator seems to have been back OK right before the stall warning was triggered again at 2:10:51.

Did the PF, at this moment of stall warning again, decide to go a bit further up, as gaining altitude seemed to him to help with the turbulence, but also be a help with the coming back of the speed indicator? We don't know what he saw through the windshield - ice? - that may have been another contributor to the decision.

....

Recently, on a cross continental flight, as passenger, during the heavy storm season, at about ½ way into the flight, at cruise altitude, and clouds way bellow, out of nowhere, the A/C entered a high altitude cloud, and hit heavy turbulence. After a couple of seconds in the cloud and turbulence, the plane climbed, and I could tell, as soon as it came out of the cloud, after not too long, that it was at least several hundred feet higher.

[airtren]

Why would you say that? Airbus acknowledged the pitot issue and released a service bulletin to the airlines months before the accident and simultaneously issued "workaround" instructions to pilots at the same time, while the issue was being fixed. What more could they reasonably have done?

Your reasonably can be interpreted as having the thought that other things could be done.

Based on elements pointed out on the AF 447 threads, there could be for instance:

a) provide a "better redundancy" of the sensors, as at the moment, they are all of the same kind, and positioned quite closely to each other, and thus providing a high probability of sharing the same failure fate, in similar conditions.

b) resolving the "lack of", or "confusing information" provided by the "A/C to Pilot Information Interface", by diversifying the parameters used to calculate certain extreme dangerous/fatal conditions, like Stall, and provide a separate and distinct "approach to Stall", and a "A/C is Stalled" Warnings.


The fact is (as I've said before) that not only has the BEA become a very different organisation...

We could be on the verge of a serious self-examination on the part of the airline industry as regards training,....

The important resources dedicated by the French Government, Airbus, Air France, and others for two years... .to find and recover all what was left of AF 447, for a good understanding of what happened, and what caused it, seem to show the commitment and determination in adopting a wide range of solutions to avoid a repetition of an AF 447 type accident in the future.

[Dehaene]

ChristiaanJ :Since your link dates from January 2011 and since we have seen no serious trace of that 'audit report' since... I don't quite understand what we are supposed to make of it.
For those interested the report has leaked here:
http://jonathan2.blog.lemonde.fr/files/2011/06/Mission-dExpertise-Externe.pdf

Regards

[Lonewolf_50]

airtren, I am puzzled at one of your suggestions.

I am also intrigued by your trying to follow a reasoning process based on what we know, the idea that the PF was keen to change altitude.
Hadn't considered that line of thought previously.
At the moment the A/P and A/THR disconnected, at 2:10:05, the A/C needed a correction command, and I think it is also possible that the PF thought, that it is worth trying to go at a higher flight level - we don't know if the air temperature may have decreased?
But wouldn't he have added power with his pitch up input if it was his intention to climb two or three thousand feet? :confused:
The BEA text indicates that the A/C climbed (from FL 350 and speed 275 kt) while rolling left and right between 12 and 10 degrees to FL 375, at which time the speed on the Left indicator increased (came back) to 215 kt, Mach 0.68, and the AoA was of 4 degrees (with stall warning stopped).

Based on the vertical speed of 7000ft/min mentioned by the BEA's text, the A/C climbed the 2500 ft to FL 375 in about 20 seconds, which left about another 20 seconds of flying approximately at this FL375 and A0A of 4 degrees, before the stall warning was triggered again at 2:10:51.

Note the left speed indicator seems to have been back OK right before the stall warning was triggered again at 2:10:51.

Did the PF, at this moment of stall warning again, decide to go a bit further up, as gaining altitude seemed to him to help with the turbulence, but also be a help with the coming back of the speed indicator? We don't know what he saw through the windshield - ice? - that may have been another contributor to the decision.
But wouldn't he have added power to climb in the first place? Cruise climbs typically are a change in both power and attitude. Is there evidence that he assumed A/T would follow his stick input (nose up) and that he noticed (late?) that the A/T had not followed his nose up for a climb command? I cannot recall that having been covered in the BEA report. Is that another reason that the pilots noted "Alternate Law?" If so, why not comment on what the auto throttle was, or wasn't, doing?

OK, then answer me this: why was TOGA applied when it was applied? See the timeline a few pages back?

Also, if I get a stall warning, is my first thought "I need to climb a bit to avoid ice?"
Recently, on a cross continental flight, as passenger, during the heavy storm season, at about ½ way into the flight, at cruise altitude, and clouds way bellow, out of nowhere, the A/C entered a high altitude cloud, and hit heavy turbulence. After a couple of seconds in the cloud and turbulence, the plane climbed, and I could tell, as soon as it came out of the cloud, after not too long, that it was at least several hundred feet higher.
You are able, in pax mode, to measure/sense at cruise altitude a change in a few hundred feet of altitude? :confused:

[jcjeant]

Hi,

seem to show the commitment and determination in adopting a wide range of solutions to avoid a repetition of an AF 447 type accident in the future. Seem's AF adopted already a measure
Some time after AF447 event AF made a general recall of the pilots for simulator training for such situation as AF447 was involved
So .. one can ask if it was refresh trainings or a completely new training ?
Again .. I suggest to read the external audit report for better comprehension ....
http://jonathan2.blog.lemonde.fr/files/2011/06/Mission-dExpertise-Externe.pdf

[bearfoil]

lonewolf

The initial NU I take to be PF directed. The Left Roll command as well. So does BEA. So the a/c was ND, Rolling Right at the switch? Logical?

As to the Rolling (L,R, between 12 and ten degrees). It would be interesting to know which direction the Rolls were. If one was consistently of different input than the other, one could infer an asym configuration of some kind.

On the other hand, it may have been an attempt to slow down, due drag.

Also BEA are not clear about the timing of "Continued ND inputs". When were these? After entering this climb? As written, the Stall is linked to the climb, initiated (?) by the Pilot.

The Stall could have easily been the result of the PF trying to recover the a/c from the climb.

The PF knew what was going on. The BEA know what was going on.

WE don't know what was going on. I am trying to come up with a way to understand what happened, by entertaining possibilities. BEA knows. BEA is not giving it up (at their discretion, no problem).

I am not trying to predict the Truth, I am trying to keep as wide as possible the discussion. Not least to keep and encourage an open mind.

Mostly, after expression of surprise and disgust at the "reported" conditions, the opinion here is too often too harsh and too conclusive (!) re: the PF performance.

Fine aircraft, fine Pilots. Always my starting point. What happened?

I do not know the motive of BEA with their note. Their distinct challenge if being devious with it, is to continue to withold data except the bare minimum to support a finding that is suitable. Cynical? Yes.

[airtren]

airtren, I am puzzled at one of your suggestions.

I am also intrigued by your trying to follow a reasoning process based on what we know, the idea that the PF was keen to change altitude.
Hadn't considered that line of thought previously.

1) at least subliminally, the PF words indicate what he may have or would consider, 2) BEA's mentioning of those words, among a quite careful and succinct "selection" of "word exchanges" between pilots, must have a significance.
....

Also, if I get a stall warning, is my first thought "I need to climb a bit to avoid ice?"
I think both pilots understood the relationship between the cloud/turbulence, possibly ice in contact with the windshield, and the loss of speed, and considered the first Stall Warning at FL 350 in light of that, and possible the one following at approx FL375, as only the left speed was showing a reasonable speed, as the ISIS came back in sync with the left speed indicator only a minute and some 10 seconds or so later.

Note: this is within the limits of the interpretation of the correspondence between actions/events and time scale in the BEA text,


You are able, in pax mode, to measure/sense at cruise altitude a change in a few hundred feet of altitude? :confused:Measure? SURE NOT, I didn't have on me any measuring device.

Sense? Yes, of course.

It was not only the clear sense that the plane was climbing, during its short climbing, but also the clear difference of the level of clouds with many holes, which was bellow the flight level before, and after the exit of the short presence in the high cloud, heavy turbulence.

[ChristiaanJ]

Dehaene, jcjeant,
Many thanks for the link to the report.
Haven't quite finished reading it yet, especially since it needs an awful amount of "reading between the lines".

[Lonewolf_50]

airtren: ah, visual cues. :cool:
I think both pilots understood the relationship between the cloud/turbulence, possibly ice in contact with the windshield, and the loss of speed, and considered the first Stall Warning at FL 350 in light of that,
and possible the one following at approx FL375, as only the left speed was showing a reasonable speed, as the ISIS came back in sync with the left speed indicator only a minute and some 10 seconds or so later.
OK ... but ... if the intent is to climb, where in the sequence is the initial power and pitch change to climb from 350 to 370/375?
Consider: they had recently slowed down to turb air penetration speed. (I presume by using A/P functions).

That is why I asked: do you believe that the nose was used to climb on the assumption that auto throttle would pitch in on time and allow the aircraft to climb at appropriate airspeed/Mach/energy state, rather than by trading airspeed for altitude? :confused:

bear:
The initial NU I take to be PF directed. The Left Roll command as well. So does BEA. So the a/c was ND, Rolling Right at the switch? Logical?
Maybe, but if there was a roll/nose drop at AP disconnect, would not the FDR give BEA a hint of that?
As to the Rolling (L,R, between 12 and ten degrees). It would be interesting to know which direction the Rolls were.
If one was consistently of different input than the other, one could infer an asym configuration of some kind.
Configuration asym ... such as ... what control surface(es)?
On the other hand, it may have been an attempt to slow down, due drag.
What? Use wing roll to slow down?
They have a throttle quadrant.
They have nose attitude control.
I don't see rolling as a deliberate "slow down" maneuver, no.
The BEA know what was going on.
I wonder. They are trying to piece it back together.
BEA knows.
As above, not sure what they know, and what they've been able to infer to fill in the holes where facts are not available.
BEA is not giving it up.
Yet.

[ChristiaanJ]

"Corporate Culture" at AF hasn't changed, audit or no audit.
CC on strike the coming weekend, pilots the weekend after.

Holiday departure/return weekends especially for France.
Classic ploy.

[takata]

Since your link dates from January 2011 and since we have seen no serious trace of that 'audit report' since... I don't quite understand what we are supposed to make of it.
For those interested the report has leaked here:
http://jonathan2.blog.lemonde.fr/fil...se-Externe.pdf (http://jonathan2.blog.lemonde.fr/files/2011/06/Mission-dExpertise-Externe.pdf)

This isn't related to the famous AF "internal audit";

[Edit:] Sorry, disregard my above statement (I had too many open windows and messed up with another report) , this one is related with AF "external audit", not with the other one I'm talking below which is another report from "Judicial Experts":
See report (in French) here: rapport d'expertise Rio-Paris (http://www.scribd.com/doc/56400906/rapport-d-expertise-Rio-Paris)

this "expertise report" (linked) is from the Justice inquiry which is in charge of the procedure. Anyway, they interwieved 22 crews from 9 flights belonging to Air France about those previous UAS events - and that's what I was trying to translate in English. Too bad, all annexes are lacking in this linked report.

Flights:
#01 10-05-2008 A340 AF675 PPT-LAX F-xxxx Papeete -> Los Angeles
#02 14-07-2008 A340 AF279 NRT-CDG F-xxxx Tokyo -> Paris
#03 16-08-2008 A340 AF908 CDG-TNR F-GNIH Paris -> Tananarive
#04 20-08-2008 A340 AF101 CAN-CDG F-xxxx Guangzhou -> Paris
#05 10-09-2008 A340 AF488 CDG-SXM F-xxxx Paris -> St Maarten
#06 31-10-2008 A340 AF012 CDG-JFK F-GLZN Paris -> New York
#07 30-03-2009 A330 AF459 GRU-CDG F-GZCB Sao Paulo -> Paris
#08 07-08-2008 A340 AF422 CDG-BOG F-xxxx Paris -> Bogota
#09 30-03-2009 A340 AF607 CAY-ORY F-GLZH Cayenne -> Paris

[xcitation]

@PJ2

Thanks, I don't disagree frankly. I'm just trying to find something outside the box to figure out why someone would point an A330 15deg NU and keep it there at FL350+ and these papers got me thinking. I've flown the aircraft at altitude and I must say it was pretty responsive in pitch and roll in Normal Law. I've always doubted the notion that the airplane was slow and 'slushy' to respond to the stick at altitude and that a bit of PIO or inadvertent backstick while controlling roll resulted in an "accidental" climb that continued to 38,000ft but I'm outa ideas!


Would you pick any of these?

The list was in reference to the stick backs during the stall rather than in the flying zoom climb earlier. The stick back during the stall is harder to explain IMHO. The zoom climb could be explained by many reasons e.g. PF wishing to climb out of the warm air he spoke of in the BEA report.

Reasons Why "Generally" Stick Back for Final Mintues?

Failure to recognize stall condition (PF responded correctly to the first stall but not subsequent stall).
Correcting for perceived overspeed/dive.
Ignored flight attitude data.
THS trim interferance?
Pilots executed wrong stall recovery procedure although they did it right the first time ???
Failed flight attitude data on PFDs, no backup steam guage style AI instrument installed. [A330 ADIRU failures: 21 May 2009 Miami-Sao Paulo TAM Flight 8091 registered as PT-MVB and on a 23 June 2009 Hong Kong-Tokyo Northwest Airlines Flight 8 registered as N805NW]
Sidestick input fault with nose up bias. Failure to diagnose and overide.

[PJ2]

CJ;
...especially since it needs an awful amount of "reading between the lines".Having seen this kind of report before, I think that this kind of writing is well within what is usually done.

If I may comment generally...- a 'reading between the lines' here isn't intended to diffuse or obscure meaning, (I know you know this...I'm writing generally).

Rather, the Report is expressed in terms that clearly indicate that it is not intended to be specifically linked with any accident. This team did not do a "safety audit" and left large areas of AF unexamined. A safety audit is quite a different thing than an operational safety review.

I think the report accomplishes what it sets out to do, which is to honestly, bluntly, examine areas that work and areas that need change, some "quickly". To me the report's language only appears "soft" - it most certainly isn't but it does not "criticize" either. It is substantively "frank".

The group is a blue-ribbon panel of experts on flight safety processes and I trust their work in this Report. This is a courageous piece of work on the part of Air France when it didn't have to be done. I am completely familiar with many of the organizational issues which the report discusses including "siloing" of departments, lack of respect for others' capabilities, complexity of processes, inability to effectively assess, highlight, communicate and use safety and risk information gathered through programs such as FDM, and so on.

These issues are not unique to Air France and the caution from the authors not to link the report with any one accident is wise and appropriate.

In fact, connecting parts of the Report or linking the Report to one accident would be the same as linking, say, one runway or a specific route, to an accident and concluding that, "we shouldn't use that runway, or fly that route anymore". The Report is far broader than this.

Edited to add:
Corporate culture takes almost a generation to change, unless done with a heavy hand informed by an unusual ability to comprehend the issues and go beyond mere commercial priorities. I know about the issues between management and union having lived with them for 35 years and won't comment further in public except to say that only one can lead and that "soft" responses to safety matters do no one any favours in the long run, but getting there can be extremely difficult depending upon the cultural milieu in which the organization functions. It is easier in Singapore to get something done "quickly" than it is, say, in France, Canada, Italy or even the US, but what is given up in the exchange?

[PJ2]

xcitation;
No, I wouldn't pick any of those, not because they may or may not apply but because there is no single "cause" and we can't stop at answer a, b, or c yet.

In these discussions about climbing, there is something that has been missed in airtren's and others' here of "climbing out of warm air", etc etc.

An aircraft on a routing which has been flight planned is not just climbed out of one altitude for another. One needs an ATC clearance to do so, as one needs an ATC clearance to deviate off course. It is not mentioned in the BEA Update that the crew obtained a clearance either to deviate from course or later, to climb out of FL350. You simply don't deviate from your flight planned routing and altitude without an ATC clearance unless it is a dire emergency, which, given all available information including the loss of airspeed information, this was not an emergency.

This relates to my earlier point about SOPs. While we do not have all the information, the BEA Update does not indicate any standard communications with ATC took place (for the climb), nor does the Update indicate that the crew followed SOPs for an Abnormal or Emergency event. The PF just started the climb, essentially on his own without coordination with the PNF, and the PNF appeared to just follow along. Now this may not be the case at all but it is what the BEA Update either says or leaves out from which we must draw interim notions. One simply never, ever "launches" into an abnormal or emergency drill on one's own, period. I have discussed this at length elsewhere.

The discussion between the two/three crew members about altitudes and temperatures is pretty ordinary stuff for flight crews and, if I may, I think airtren and others may be reading far too much into the communication/discussion...they're parsing it far too finely and perhaps looking for justifications of the pitch-up and climb where there are none. I've had such discussions many times and while an operational decision (to climb or not), it isn't unusual, ominous or even significant that they decided not to climb at that moment.

True, the ICAO Flight Plan (available in the Appendices of the First BEA Interim Report and reproduced below), indicates that after NTL the routing was UN873 INTOL/M0.82 @ FL350, then SALPU at which a climb to FL370 was flight planned, with the Mach remaining at M0.82, (see the ICAO Flt Pln below).

Standard procedure is to cross the waypoint at which the higher altitude is planned, AT the higher altitude (vice beginning the climb at the waypoint).

They were relatively heavy (not "too" heavy...the discussion was a recognition that it was a bit too warm to climb even though I suspect they could have...I've done it sometimes, when it's close but still operationally doable because if one doesn't take the higher altitude one may not get it for the balance of the trip - it's as much a judgement call as it is an operational one).

Their clearance at that moment was to maintain FL350 and they would not climb to/maintain FL370 without ATC clearance to do so even if the Flight Plan indicated such - one simply doesn't climb without a clearance unless it is a dire emergency when communication with ATC is not possible in the time available. Again, this was not the case at this point in the flight, (prior to SALPU). That climbing to FL370 was on their minds was obvious but there was nothing unusual in that - it was on the flight plan and they were assessing the need for the climb and, at that point, were content to stay at FL350, with a possible request to climb to FL370 a bit later than flight planned.

My sense of their discussion is, therefore, that it was about managing the flight, not about any concern about altitude and weather or temperature. I think things were "ordinary" in the sense that there was weather around and they were doing what everyone else was likely doing - discussing it, and deviating where necessary and monitoring temperature for their climbs.

PJ2


ICAO Flight Plan from the 1rst BEA Report:

LFPGYEYX SBGLYOYX SBGLAFRK
(FPL-AFR447-IS

-A332/H-SPRIJWYG/SD

-SBGL2200

-N0481F350 DCT AWAKE UZ10 FLIRT/M082F350 UZ10 NTL UN873
INTOL/M082F350 UN873 SALPU/M082F370 UN873 ORARO/M082F370
UN873 ISOKA/N0471F370 UN873 LIMAL/N0466F390 UN873 SAMAR/N0468F380 UN873 BAROK/N0465F400 DCT PORTA UN873 MOKOR UN741 NTS/N0484F280 UN741 KEPER UT182 ROMLO/N0483F270 DCT

-LFPG1034 LFPO

-EET/SBBS0028 SBRE0050 SBAO0302 GOOO0349 GVSC0512 GCCC0606
LIMAL0643 GMMM0731 LPPC0816 LECM0851 LFRR0930 LFFF1004 RIF/ZMR UN976 DGO UL176 SSN UP181 ENSAC SOLSO DIRAX LFBD REG/FGZCP SEL/CPHQ DAT/SV DOF/090531)

[takata]

Hi xcitation,

1. Failure to recognize stall condition (PF responded correctly to the first stall but not subsequent stall).
[...]
5. Pilots executed wrong stall recovery procedure although they did it right the first time ???


PF responded correctly?
Do you mean that climbing at 7,000 ft/mn could have been a correct answer to stall warnings at FL350? A correct reaction seems to me to descent to lower flight level, not a try to out climb the weather.

There is no certaincy about the reason causing the stall warnings to sound due to BEA narrative style (was it at 0210:05 or slightly later?); Consequently, there is only two possibilities:
1. Caused by switch to Alternate Law and subsequent change of Stall Warnings threshold.
2. Pull up by the pilot => g-load induced warning by his first sidestick order.

Any subsequent sidestick nose down order was only applied between 0210:16 and 0210:49. Moreover, not enough ND was applied to stop the climb as she climbed again 500 ft after this point. Hence, this is hard to believe that it would be a reaction to those previous stall warnings, and it seems to be confirmed by the second reaction.

[bearfoil]

Lonewolf

Asym config. At first blush, a jammed or unstowed spoiler. Consistent with a RL input at handoff. Or an hung aileron. Rudder issue?

Isn't it possible? Also, BEA do not state much of anything re: aspect at handoff. There is perhaps nothing of note to report, or there is, and it remains unreported. Nodata. "No soup for you........"

The Path shows a chronic right biased descent, and BEA in first Interim state a "rotation right" at impact. I think it is early to foreclose on all mechanical issues.

If PF input "SLOW" (turbulence pen speed) to auto pilot, it would be in NORMAL LAW. As such, at a/p drop, He would be in NORMAL LAW. As such, if he input NURL, he HAS Protections in PITCH and ROLL. In ROLL to 30 degrees, and Pitch to STALL nibble. The approved recovery from CFIT is full BACK and full ROLL (And full THROTTLE). Not suggesting CFIT, only to demonstrate the LAW in effect at a/p LOSS. If I was expecting STALL protection with my Pitch UP, the dual chirp of STALLSTALL would be more reassuring than worrying.......Remember, at this point NORMAL LAW.

It is here, during the last ten seconds of a/p, and the first ten seconds of Hand flight, I believe the a/c was lost.

BEA state the a/c did not begin to climb until she was passing through ten degrees NU. (PITCH). So there was a lag in response to PF's "First Input".

Did he become impatient, and just as she started to rotate, input everything the Stick had left? The elevator responds faster than THS, did he have too little back stick with his first input? As the THS caught up, she "overrotated"? Is there a STALL WRN on the THS? Because this climb wants to tell us that ND (at least 'effectively'), was unavailable for the time she was zoomed?

[takata]

Failed flight attitude data on PFDs, no backup steam guage style AI instrument installed. [A330 ADIRU failures: 21 May 2009 Miami-Sao Paulo TAM Flight 8091 registered as PT-MVB and on a 23 June 2009 Hong Kong-Tokyo Northwest Airlines Flight 8 registered as N805NW]
Please, could we have a quote from those flight reports showing an Attitude data failed on PFDs?
Where did you get that? Those are UAS reports, no trace of IR faults.
No backup steam gauge? Well there is an ISIS, which is the 4th source of Attitude indication! (considering that the backup ADIRU3 may be displayed in either PFD in case of 1 or 2 IR channel failure)
http://takata1940.free.fr/isis0.jpg
http://takata1940.free.fr/isis1.jpg
http://takata1940.free.fr/isis2.jpg

[takata]

If PF input "SLOW" (turbulence pen speed) to auto pilot, it would be in NORMAL LAW. As such, at a/p drop, He would be in NORMAL LAW. As such, if he input NURL, he HAS Protections in PITCH and ROLL. In ROLL to 30 degrees, and Pitch to STALL nibble. The approved recovery from CFIT is full BACK and full ROLL (And full THROTTLE). Not suggesting CFIT, only to demonstrate the LAW in effect at a/p LOSS. If I was expecting STALL protection with my Pitch UP, the dual chirp of STALLSTALL would be more reassuring than worrying.......Remember, at this point NORMAL LAW.
You could save the bold for something sensical, it's so embarrassing.
Quite simply, AP would not go OFF while EFCS would stay in NORMAL law.
When AP kicked off, it was ALTERNATE 2. Before, it was NORMAL, right?

Hence, when the pilot entered Mach 0.80, this was between 0208:07 and 0210:04... so, call it before event (NORMAL) with autopilot ON... while at 0210:05, it was ALTERNATE 2, after event, with autopilot OFF!
Get it?

Event = UAS.

In Normal law, if something happened (attitude, speed) protections will kick in and EFCS will set itself in "protected" law (high Alpha, High Speed, bank angle, pitch attitude...) without any need of pilot imputs, the aircraft will recover automatically. They won't be "STALL STALL" sounding if entering the high Alpha mode (Alpha-lock) because the aircraft would not go as far by itself (pilot needs to help up to Alpha_Max, where it doesn't sound either).

After EFCS dropped NORMAL for ALTERNATE 2, anything could happen as protections won't kick, and everything would have to be done manually.


It is here, during the last ten seconds of a/p, and the first ten seconds of Hand flight, I believe the a/c was lost.
It looks like a motto!
BEA is covering up that, at 0210:05, she was at 90° bank angle, while "starting" to roll to its right... or was at -90° pitch down while "starting" to climb at 7000 ft/mn!

[jcjeant]

Hi,

More and more I read this BEA"note"(french or english language) and more and more it make non sens for me (for many reasons and principally a erratic chronology and a syntax of bad first grade student)
Best is to stay stick with the two first interim reports and wait the FDR (I don't think the CVR is crucial)
Unfortunately I think (personnal feeling) the next interim report will not include any FDR parts ... :uhoh:

[bearfoil]

takata. Thank you for the data. I appreciate that you respond, and your response is important. The invective and attitude is wasteful, though. I am old enough to have learned to smile instead of frown. No offense taken, but save your upset, it must be unpleasant for you. It isn't to me!

:ok:

[barry54]

Hi folks, first post. I've been following PPRuNe for a couple of years now, Spanair , Colgan 3407, and AF447. Not a pilot but I am an interested frequent flyer. Thank you to all pilots and aviation people for the many contributions to these forums. Better training for pilots and having a clearly visible AOA indicator do seem like common sense improvements.
I do have an idea, a plan maybe, that I have not heard anyone discuss. It is this ---- Provide a shield system for the pitot tubes in potential icing conditions----. How do you do that ? The speed sensors on modern big jets are state of the art . If a more advanced design were available it would be used. Someday scientists may create a new material called unobtanium . It will be immune to ice buildup at all speeds and conditions. That would be great but that day is not here yet. In the meantime what planes need is an Apollo 13 type of a solution.

One way this could be done is to design small aerodynamic bullet shaped shields for all 3 pitot tubes. The two part shields would normally be left in an open retracted position along the sides of the pitot tubes. When a plane is about to enter bad weather one or maybe two of the shields would be moved forward and together protecting the speed sensors from ice buildup. There are a lot of different ways a shield system could be engineered. When flying through an area like the ITCZ one shield could be left open and one shield closed , that pitot tube being held in reserve , and one shield could cycle open for a few seconds, just long enough to get an accurate reading and then closed for maybe 7 seconds It would be better to get intermittent but accurate readings then none at all. You could also add a smaller diameter 4th pitot tube with no shield. It would be designed to fail in half the normal time in icing conditions and would serve as an early warning system for the pilots and computers that all speed indications and the AP may soon be lost.

Sometimes bad weather can't be avoided. If airlines are going to fly people across the ocean at night in stormy weather then the speed sensors need better protection from icing , pilots should get an AOA display like the military guys have, and some kind of real practice in hand flying at high altitude in difficult circumstances. I am waiting to see what the BEA will recommend.

[henra]

Dehaene, jcjeant,
Many thanks for the link to the report.
Haven't quite finished reading it yet, especially since it needs an awful amount of "reading between the lines".

I find the report quite telling. Working in a bigger company myself I háve the feeling I don't need too much reading between the lines to get an idea of the general 'culture'.

Surely it does not explain the AF447 accident in any direct way.
On the other hand it conveys a slight sense of a relatively strong hierarchy within an 'elitist' group and certain mistrust in other's abilities.
Statements coming from Pilots about Captains being 'immune' to their line managers implicitely point to a rather steep hierarchy in the cockpit.
In general such a spirit does not help a good workload sharing in case of high workload/stress.
Also mentioned is a slight tendency to 'Not go by the books', cut corners, etc.
All this doesn't explain any of the direct actions of the PF of AF447.
It might however be related indirectly to a potentially sub- optimal workshare during the crisis and maybe even reluctance to openly express any discomfort with the actions of the colleague or different impressions of the actual situation. This would especially apply if the PF was the more experienced of the two F/O's.
Knowing who actually was PF could indicate if this might have been a factor or rather not.

Edit: As a hint that CRM seems to be a very important topic in this report: They have added Sub- Items to go more into the detail for that and used up most of the alphabet in doing so. The only other items where they also chose to go a bit into details was Instruction/Training and Flight Data Montitoring, albeit to a lesser extent.
Take that for what it's worth....

[Lonewolf_50]

barry54, that is an Interesting idea.

If you look at the discussions in the three earlier AF 447 threads, and posts that address the improved Goodrich pitot tubes, the "build a better pitot" approach seems to have in part succeeded. That this hull had not yet gotten the new probes is an unfortunate factor in this crash. The new design looks to have been begun after some years of the industry reporting issues with various pitot tube malfunctions.

From the FAA airworthiness E9-21368 of 02 September 2009:
Federal Aviation Administration, 14 CFR Part 39, [Docket No. FAA-2009-0781; Directorate Identifier 2009-NM-111-AD; Amendment 39-16004; AD 2009-18-08] RIN 2120-AA64// Airworthiness Directives; Airbus Model A330-200 and -300 Series Airplanes, Model A340-200 and -300 Series Airplanes, and Model A340-541 and -642 Airplanes
The EASA PAD also states that a new Thales Avionics pitot probe having part number (P/N) C16195BA has been designed, which improves the airspeed indication behavior in heavy rain conditions on Model A320
airplanes. This same pitot probe standard has been made available as an
optional installation on Model A330 and A340 airplanes, and although
this has shown to be an improvement over the previous Thales Avionics
pitot probe, P/N C16195AA standard, it has not yet demonstrated the
same level of robustness to withstand high-altitude ice crystals as
Goodrich pitot probes having P/N 0851HL. We are issuing this AD to prevent airspeed discrepancies, which could lead to disconnection of the autopilot and/or auto-thrust functions, and reversion to flight control alternate law and consequent increased pilot workload. Depending on the prevailing airplane altitude and weather, this condition, if not corrected, could result in reduced control of the airplane.
A shortcoming I see in the "shielding" solution is that if you get it slightly wrong, you interfere with airflow around the pitot tube and thus interfere with its normal function. (A fix worse than the problem makes the engineer a sad fella ... as he has to do it again and now gets funny looks due to the budget overrun ... )
Note also, from the same document:
On February 4, 2004, we issued AD 2004-03-33, Amendment 39-13477 (69 FR 9936, March 3, 2004), for certain Airbus Model A300 B2 and B4 series airplanes; Model A300 B4-600, A300 B4-600R, and A300 F4-600R
series airplanes (collectively called A300-600); Model A310 series airplanes; Model A319, A320, and A321 series airplanes; Model A330-301, -321, -322, -341, and -342 airplanes; and Model A340 series airplanes. Paragraphs (g)(1) and (h)(1) of that AD require, for some Model A330 and A340 airplanes, replacement of certain pitot probes with Goodrich pitot probes having P/N 0851HL. For other Model A330 and A340 airplanes, paragraphs (g)(2) and (h)(2) of that AD require replacement of certain pitot probes with Thales Avionics pitot probe having P/N C16195AA.

[jcjeant]

Hi,

In the meantime what planes need is an Apollo 13 type of a solution. But ..
A shortcoming I see in the "shielding" solution is that if you get it slightly wrong, you interfere with airflow around the pitot tube and thus interfere with its normal function. (A fix worse than the problem makes the engineer a sad fella ... as he has to do it again and now gets funny looks due to the budget overrun ... )
Note also, from the same document:So .. this system worked for Apollo 13 but can't for Airbus ?
If I understand well .. the "Apollo 13" pitot type .. is NOT working (not in the measures loop) when shielded .. so it's not interference at all as the shielded pitot tube is neutralized.... IMHO

[barry54]

Lonewolf 50 -- The Goodrich pitot tubes are somewhat of an improvement, but they can still fail like the Thales tubes. Any shielding device would clearly need to be several inches behind the pitot tube opening when in the retracted position.
You are right about possible problems. If a shield system was not well engineered and thought out it could cause problems of its own. It would need to be as simple and foolproof as possible.
jcjeant -- I was not referring to the Apollo 13 pitot tubes . There was a problem during the mission with the ships air supply .The carbon dioxide scrubbers were inoperable because of loss of power in the main module .The astronauts could not wait for a perfect solution .They needed an immediate fix. It it involved duct tape and cardboard, but it worked

[xcitation]

@Takata

Thanks for the superb graphic. Do you recall the posts that AF did not install all of the available backup steam guages option on this a/c?

The report does not explicitly state attitude failure. However it does not state that attitude indactions were all displayed faithfully. FDR did not record speed on right PFD, so maybe not the attitude.

The BEA report does show errors on both ADIRU and ISIS. Having read some other incidents I recall that Airbus can give bogus stall warnings and PFD degradation under certain ADIRU failures (those 2 Airbus incidents near the Australian radar station?). IMHO the scant BEA reports do not eliminate the possibility of a degraded attitude indicator on the right PFD.

The list of 7 reasons are purely speculative. Probably a better title is "possible contributing factors to a general nose up/stick back". I was struggling with imagining the crew spending nearly 4 minutes looking at the +15 deg pitch and giving it generally stick back - sometimes to the stops. Which scenario(s) would you envisage to explain this?

I am trying to get a list of all factors either likely or not. Add any new ones that are missing. Identify any that are false (e.g. attitude indicator).

[PJ2]

xcitation;

There is no evidence either in the ACARS series or any of the BEA Reports and Update that failure(s) of the attitude display(s) occurred.

Initially, (before the pitch-up), this was a simple loss of airspeed data, from which all messages from 02:10:05 until the apogee of the climb may ultimately be traced. In other words, there are no ACARS messages which indicate failure of the IRUs, which supply all attitude information, before the pitch-up.

The ADIRU to which takata's schematic shows is a dual "ADR"/"IRU" installation. As shown in the schematics below, the ADR part may be separated and otherwise shut off separately from its IRU, (as per standard fault actions set out in the FCOM or on the ECAM).

At the time you claim the "possible" effect (of loss of attitude information) to have occurred (which "causes" the pitch-up), the 3 IRUs remained unaffected by the pitot failure/airspeed loss and would have continued to display correct attitude information after the pitch-up. A change in altitude information would require that the Static ports were affected which would in turn affect both the ADR and the IRU incoming data. By all indications, this did not occur.

Therefore the "original cause" that is claimed to have caused the PF to pitch the aircraft up, is not present.

By the time the IR1 & IR2 FLR messages appear in the ACARS series, the aircraft is seriously stalled and descending at > 10,000fpm.

In different words, if IRU #1 or IRU #2 or both were functioning (we have no messages before the pitch-up that they weren't), and DMC #1 or DMC #2 or both, were functioning (again, no messages, no comments in the BEA Reports), then attitude information would be displayed normally, very likely on all three indicators.

From this, there is no basis for believing or even positing that any attitude indicator failed, causing the PF to pitch the aircraft up.

Merely saying that it is possible has no relation to whether it actually occurred or not, but the statements above show that normal attitude indications were very likely available.

I'm not dismissing your ideas outright here. I am demonstrating the way an investigative process might function.

A claim that any or all attitude indications were lost requires that the above statements be refuted.


PJ2

Here are the schematics:


ADIRS Control Panel:

http://www.smugmug.com/photos/i-Gzm5qvg/0/XL/i-Gzm5qvg-XL.jpg



ADIRS Schematic - information flow:

http://www.smugmug.com/photos/i-hLzBLCJ/0/L/i-hLzBLCJ-L.jpg


For comparison to the ADIRS schematic - the Pitot-Static ADM/ADIRU system. Pitot-static data is fed to the ADIRS for use by both the IRU (baro altitude, and rate of baro altitude change) and the ADR:

http://www.smugmug.com/photos/i-Sp8P439/0/L/i-Sp8P439-L.jpg

[airtren]

airtren: ah, visual cues. :cool:

What's this supposed to mean?


OK ... but ... if the intent is to climb, where in the sequence is the initial power and pitch change to climb from 350 to 370/375?
Consider: they had recently slowed down to turb air penetration speed. (I presume by using A/P functions).

That is why I asked: do you believe that the nose was used to climb on the assumption that auto throttle would pitch in on time and allow the aircraft to climb at appropriate airspeed/Mach/energy state, rather than by trading airspeed for altitude? :confused:
Based on the BEA text, the A/THR was OFF at the time of the climb.

The BEA text does not mention manual power/throttle changes during the climb time interval from FL350 to FL375. So, that makes the climb unintentional?

A kinetic versus potential energy conservation calculation shows that the BEA indicated height delta (2500 ft from FL350 tgo FL375) checks against the BEA indicated delta speed of 60 knots (from 275 to 215 knots). Same is true for FL380, and 185 knots.

dEk = Ek (275knots) - Ek(215knots) = dEp (2500ft)


... One needs an ATC clearance to do so, as one needs an ATC clearance to deviate off course. It is not mentioned in the BEA Update that the crew obtained a clearance either to deviate from course or later, to climb out of FL350.
That's clear. Thanks for the detailed explanation.

But the connecting to Dakar failed, and the contact with the previous ATC was no longer active, so there was no online ATC control/contact at the time.

A deviation of 12 degrees to the left started already prior to to the A/P disconnect, without ATC approval, which would seem to indicate that the PF (and PNF) were already in ATC bypass mode when the climb started...

[PJ2]

Hello airtren;
A deviation of 12 degrees to the left started already prior to to the A/P disconnect, without ATC approval, which would seem to indicate that the PF (and PNF) were already in ATC bypass mode when the climb started...
I'm not clear on what is meant by "ATC bypass mode". Can you help me out? - I've never heard of it.

Just to review, from the First BEA Report, (all reports found here (http://www.bea.aero/en/enquetes/flight.af.447/flight.af.447.php)), the crew had established contact with ATLANTICO on HF and had acknowledged a successful receipt of their SELCAL by the ATLANTICO aeradio operator, (ATLANTICO and all radio stations contacted on HF are not ATC controllers, remember - they relay messages from overseas flights to ATC controllers who then provide clearances/instructions to be relayed back to the flight. This often takes a lot of time so one has to anticipate needs early).

A deviation off course requires an ATC clearance. As I've stated, an aircraft cannot just be taken off course without such clearance unless an emergency diversion is required, (I've done it once, on the Pacific - one lights up the aircraft, broadcasts intentions on 123.45 and if necessary on 121.5 and one might climb a few hundred feet 'just in case'). The CPDLC is a direct link to ATC but it had not successully logged on. (I have my theories on why) but communications were established and a clearance to deviate or climb is required unless, as described, an emergency exists.

[airtren]

Perhaps I am posting under a misunderstanding on my part: the PF & PNF had no radio communications from the time when the event started, all the way to FL 0.

They deviated to the left at FL 350, and climbed from FL350 to FL375 and then FL380 without any radio communications and thus ATC permission/approval - if I understand correctly.

[JD-EE]

One has to wonder at the wisdom of starting with an aircraft concept which is naturally longitudinally speed stable, and design ALT LAW handling characteristics which allow the aircraft to be flown (with UAS), to stalling Alpha and beyond in a trimmed condition.

In most situations roughly analogous to AF447 the crews have visual clues of one sort or another. That means the plane leaves it to the pilots to discern "too fast" from "too slow" from those clues.

Um, that brings up a probably silly question. Might the pilots be better able to guess AoA from simply turning on the landing lights or watching wing tip lights to see if they can get any hints from the variations in the clouds through which they are flying?

it might be that he had learnd this (wrongly-) skill......

There were two of them who apparently learned it wrong.

--

I love PJ2's pages from Davies. Even I understood most of it. And it explains a lot. Thanks.

Now I have a question:
From 2 h 10 min 05.... The airplane began to roll to the right and the PF made a left nose-up input.
At around 2 h 11 min 40 .... The PF made an input on the sidestick to the left and nose-up stops, which lasted about 30 seconds.

The plane turned to the right despite NU-L inputs on the stick. Did we ever hash this out? (If so, excuse me please. I somehow missed it.) Did the pilot fixate on the plane not being able to turn back to a straight course and forgot about stall? And why did the plane apparently never respond to the left part of the inputs?

Rolling the plane to the left with up elevator is, I believe, a left turn input. If I'm right why'd the plane go into a fairly tight right turn?

bearfoil, you should have mentioned aside from one set of alternating roll inputs all inputs were either neutral roll or left roll to make your point better. I don't suggest a reason. I simply ask "why?" Then you launched into what seems to me to be silliness.

PJ2 - in message 515 of http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-26.html#post6582663 you suggest you're out of ideas. Does the notion of turning right with left stick inputs key any ideas?

[bearfoil]

There are several sources of data to support these last ponderings. As above, PNF would alert by radio as to the deviation, and also the climb, and if it was inadvertent, it may have been accompanied by a M'aider.

Simply because communication is problematic, the crew would follow procedure and make the calls. The CVR, depending on ambient sound level, will support this, so I am not worried.........

The inference that could be made if notification to local traffic of a climb was not made, would mean that the PF's original input will not have been intended as a 'climb', per se, but a recapture of FL350 if low.....

For about two years, various protestations of a/c fidelity and reliability have been made by quoting design considerations.

When it comes to actual BEA data "PF input RLNU.....at PITCH +10 the a/c began to climb", the immediate response is the PF commanded an absurd ascent which led to the loss of a/c. Various adjectives are selected out of thin air to savage his training, and hold in suspicion his competence.

I find that outrageous. Is there another way to see these slanders here?


JD-EE I have no opinion on what you consider silly. If you think I made a compelling statement, acknowledge and leave the gossip in the computer. I have been hammering on the initial ten seconds for months, actually from the beginning...........

What part of airframe/EFCS failure do you seem reluctant to address? A fall off of the a/c to the right is noted by BEA, as you state. It happens again, and BEA states same. Rolls and reversals are stated on the way up the climb. The a/c is behaving unusually, notwithstanding the absurd climb.

Rudder for Roll. Rudder issues. If Left Rudder was unavailable, any out of trim excursion to the right would be un reversed, and additive. Likewise if Right Rudder was in, and not corrected (or correctable).

[mm43]

airtrenPerhaps I am posting under a misunderstanding on my part - the PF & PNF had no radio communications at the time when the event started, and they deviated by 12 degrees to the left, without any permission/approval.They were on UN873, an unidirectional northbound airway, and even though there is comment in the BEA Note that they hadn't managed to logon to DAKAR via ADS-CPDL, they were still (12 mins) inside the ATLANTICO FIR. There are currently no known records of them attempting to call either ATLANTICO (which had their guard) or DAKAR on HF.

There were a number of "off track" deviations made that night by other aircraft passing through the ITCZ, and it is not clear how many requested clearance, or how many just deviated.

Adjacent parallel airways are spaced at 90 NM.

[DozyWannabe]

When it comes to actual BEA data "PF input RLNU.....at PITCH +10 the a/c began to climb", the immediate response is the PF commanded an absurd ascent which led to the loss of a/c. Various adjectives are selected out of thin air to savage his training, and hold in suspicion his competence.

I find that outrageous. Is there another way to see these slanders here?

Bear, I honestly don't see that being either implied or said outright anywhere - in fact the only person to say words to that effect throughout the running threads has been you!

Even elite pilots make mistakes - sometimes fatal ones. *If* the PF in this case made a mistake, then there may have been extenuating circumstances. *If* his training was part of the cause through being substandard, then it must be corrected. This is not about blame or slander, it's about trying to make sure that it doesn't happen again.

[bearfoil]

I agree since you state such, that you do not see an imbalance of invective. Much of it has become tacit, part of the Thread Line Culture.

Part urban myth, at this point. The time just before a/p unlatch is not well addressed by BEA. Therefore Not mentioned=Cannot have happened? The part that is disclosed is parsed such that we look for faults in the Pilotage, and accept the a/c "AS DESIGNED". "The aircraft won't do that". "What was the pilot Up to".

Doze: Do "Elite Aircraft" make mistakes?

[PJ2]

Hi airtren;
Perhaps I am posting under a misunderstanding on my part: the PF & PNF had no radio communications from the time when the event started, all the way to FL 0.

They deviated to the left at FL 350, and climbed from FL350 to FL375 and then FL380 without any radio communications and thus ATC permission/approval - if I understand correctly.
I'm just going by your post #519 where you say:

"Sometime between 1:59:32 and 2:01:46, the PF said, “…turbulence that you just saw…. We’re in the cloud layer unfortunately we can’t climb much… because the temperature is falling more slowly than forecast… and the logon with Dakar failed”.

The text marked in blue can be considered as implying that going to a higher flight level, above FL350, was considered as a possible solution, had the air temperature and the Dakar logon been OK.

At 2:08:07 PNF said “you can maybe go… to the left” airplane …. change ….about 12 degrees possibly because the increasing turbulence …. The level of turbulence increased … the crew reduce the speed to about Mach 0.8.

At the moment the A/P and A/THR disconnected, at 2:10:05, the A/C needed a correction command, and I think it is also possible that the PF thought, that it is worth trying to go at a higher flight level - we don't know if the air temperature may have decreased? "
Perhaps we're talking past one another! :)

For the record, it is stated in the BEA Update that the pitch-up was the result of an aft movement of a sidestick.

To your point, all I'm saying is, you can't just "decide" to climb, or descend to a new altitude or deviate off course for weather or anything else, without an ATC clearance unless there is an emergency.

They didn't get a clearance to climb but just pitched the aircraft upwards.

Therefore we have to conclude that the PFs intention, unchallenged by the PNF, was not to just climb to a higher altitude and level off.

Therefore his reasons for the pitch up lie elsewhere and that is what we need to find out.

And to drive a point home which I have been stating for some time now, when one loses the airspeed indications, one does NOT change pitch or power. As soon as one does that, one loses the pitch and power settings in which the aircraft was stable immediately prior to the loss of airspeed indications and very quickly loses situational awareness.

Without careful attention to attitude and power, loss of control can quickly result. A pitch-up of 15degrees in a transport aircraft operating at FL350, if held and not reduced, is, for all intents and purposes, a loss of control.

Whether the PNF knew about and understood what the PF was doing is not known and not discussed in the BEA Update. We will know, I hope, in the upcoming Report.

Does this help?

[A33Zab]

Asym config. At first blush, a jammed or unstowed spoiler. Consistent with a RL input at handoff. Or an hung aileron. Rudder issue?

All A330 Flight Controls servos are individually monitored, including spoiler servo jacks.
If one 'refuse' to act as commanded the FCPC/FCSC will take corrective
actions to prevent such an asymmetry; e.g. remove symmetric hydr.
pressure to aerodynamically stow the spoilers and at the same time
locking the extend movement (excl. 4 & 6 for roll support) to prevent
floating spoilers.

This will be notified to crew by an appropriate ECAM message:
"F/CTL SPLR FAULT"
or in case of aileron fault:
"F/CTL L (R) OUTR (INR) AIL FAULT"

Both faults were NOT present at the time.

I did mention it before, could MLA be any factor?

Manoevres Load Allevation.

The purpose of MLA is to distribute the lift over the wing to relieve
structural load on the outer wing surfaces (bending moment).
The demanded load factor is maintained.
MLA utilises spoilers 4,5 & 6 and the ailerons.
The MLA becomes active when the side stick is pulled more than 8°,
and the load factor is more than 2g, in which case:
- The ailerons are deflected symmetrically upwards:
Max 11° added to Roll demand, if any.
-Spoiler 4,5 & 6 are symmetrically deflected:
Max 9° added to Roll demand, if any.
- Deflection is proportional to load factor in excess of 2g.

An elevator demand is simultaneously applied to compensate for the
pitching moment induced by spoilers and ailerons.

The load allevation is only available:
CAS > 250 Kts
FLAP LVR = 0 position
In NORMAL or ALTERNATE LAW.

MLA has priority over the speedbrakes.

[DozyWannabe]

Much of it has become tacit, part of the Thread Line Culture.

I disagree - this is and has always been a technical discussion regarding systems design and the man/machine interface, any attempt to deviate from that has generally been avoided.

Part urban myth, at this point. The time just before a/p unlatch is not well addressed by BEA. Therefore Not mentioned=Cannot have happened?

Well, there's two likely reasons for that:

1) Everything appeared relatively normal up until that point, so mentioning events during that time period were unnecessary
2) They didn't know exactly what was going on during that time period, so could not put anything conclusive in the note

The part that is disclosed is parsed such that we look for faults in the Pilotage, and accept the a/c "AS DESIGNED". "The aircraft won't do that". "What was the pilot Up to".

Not at all - that is how you seem to be choosing to interpret it. Coming at it with no preconceptions it reads as a very dry statement of events that happened at specific points in time without any implication of anything, as you would expect of what was essentially a press release to get the more lurid speculation out of the way so they could do their job.

With all due respect, you seem to choose to be very definite on occasion and then swing wildly into evasiveness and conjecture if anyone asks anything of you directly, so I'm going to ask you directly and see what - or if - you answer:

Do you believe in a conspiracy on the part of the BEA and Airbus to blame the pilots in the case of AF447?

Either way I think you're too emotionally involved with this, and I suspect a few days away from the thread might do you some good and get you some perspective - it certainly did me good a few weeks back!

[bearfoil]

A33Zab

Thanks. If aerodynamically stowed, and absent hydraulic pressure, can they flutter?

Also, RTLU. Is Rudder centered before limit is ennabled? Any chance of (R) Rudder staying with the a/c all the way, without annunciated ECAM or ACARS rpt? If jammed at (Right) would there be any ECAM, since the Rudder has (limited) authority anyway? Would the deflection be accepted as an input, not an anomaly?

Hi Dozy. Conspiracy is defined as an effort to collude with others to effect an outcome, generally for ulterior motives. A "Surprise Birthday Party" is also a conspiracy, a good one! Few people have left an ability to accept that sometimes motives are unconscious, or inadvertent. That means we can say bias instead of conspiracy. With bias, it is even more difficult to pin down, since it frequently lacks acknowledgmwent among 'buds'.

The silence of the lost pilots is a sort of vacuum. Nature abhors a vacuum, and the firstest with the mostest will fill it up. Yes, there is an element of 'blame the crew'. I think it does not rise to the definition of criminal, but merely to an excusable 'birds of a feather' sort of interdisciplinary sort of thing. I take your recommendation seriously, I have once again become too passionate, and will take your advice.

[DozyWannabe]

With all due respect, you seem to choose to be very definite on occasion and then swing wildly into evasiveness and conjecture if anyone asks anything of you directly...

Do you believe in a conspiracy on the part of the BEA and Airbus to blame the pilots in the case of AF447?

Conspiracy is defined as an effort to collude with others to effect an outcome, generally for ulterior motives. A "Surprise Birthday Party" is also a conspiracy, a good one! Few people have left an ability to accept that sometimes motives are unconscious, or inadvertent. That means we can say bias instead of conspiracy. With bias, it is even more difficult to pin down, since it frequently lacks acknowledgmwent among 'buds'.

*le sigh*...

The silence of the lost pilots is a sort of vacuum. Nature abhors a vacuum, and the firstest with the mostest will fill it up.

Or the CVR that is now in the hands of the BEA - the "lost" pilots are silent no more!

Yes, there is an element of 'blame the crew'.

I'd like to see precise examples of where you're getting this idea from.

I take your recommendation seriously, I have once again become too passionate, and will take your advice.


See you when you come back!

[KBPsen]

BEA state the a/c did not begin to climb until she was passing through ten degrees NU.
"PF input RLNU.....at PITCH +10 the a/c began to climb"

HazelNuts39's post (#30), after which even a PPL would understand the impossibility of what the rewriting of BEA's words is claiming, should have laid this one to rest.

Parsing and out of thin air indeed.

[Turbine D]

Hi PJ2,

There was a post, #2062 by SaturnV on the R&N AF447 thread regarding the deviation ("Can you maybe go to the left?"). He posted a satellite weather overlay where this turn to the northwest occurred that was posted earlier by MM43. If this is at all somewhat accurate, it would appear they recognized the weather ahead (perhaps a little late) and were using their radar to shoot the gap between two CB's, the one on the right being slightly more significant than the one on the left. And as they did so, the turbulence increased and they reduced speed to MACH .80. They probably had no time to ask for a deviation at this point in time and it wouldn't appear they needed to deviate for very long.

Just some thoughts.

[PJ2]

Hello Turbine D;
And as they did so, the turbulence increased and they reduced speed to MACH .80. They probably had no time to ask for a deviation at this point in time and it wouldn't appear they needed to deviate for very long.

Just some thoughts.


Entirely plausible, TD - Absence of communications for an ATC clearance to deviate for weather does have other explanations. As I mentioned, I've had to do it just once - SFO HF was terrible, (noisy and crowded), there was no such thing as "CPDLC" and we HAD to start the turn in the next ten miles. Rare, but it happens. Normally it's accompanied by a broadcast in-the-blind on 123.45 and possibly 121.5 but maybe it got really rough quickly - the need to bring back the Mach doesn't occur very often. The pitch-up may have a similar, plausible explanation, before it got out of hand, that turns out to be entirely different than what has been posited thus far. We'll know soon enough I hope.

[3holelover]

I'm disappointed I didn't get any response from pilots to my last question, but that isn't going to hold me back from saying I think some of you (Bearfoil) are appearing to be frighteningly closed to the notion that the airplane may well have been just fine, but the PF screwed the pooch.

Good grief man, from what we "know" so far, it's the most logical solution to all questions.

Now, why he might have done so leaves all sorts of questions to answer, but all of this mind numbingly tedious examination and re-examination of every nitty gritty detail of the aircraft and suppositions of failures can surely wait until the rest of the data is shown to us all?

[airtren]

Hi airtren;

Perhaps we're talking past one another! :)

Are we?http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif

... you can't just "decide" to climb, or descend to a new altitude or deviate off course for weather or anything else, without an ATC clearance unless there is an emergency.

They didn't get a clearance to climb but just pitched the aircraft upwards.

Therefore we have to conclude that the PFs intention, unchallenged by the PNF, was not to just climb to a higher altitude and level off.

Therefore his reasons for the pitch up lie elsewhere and that is what we need to find out.

And to drive a point home which I have been stating for some time now, when one loses the airspeed indications, one does NOT change pitch or power. As soon as one does that, one loses the pitch and power settings in which the aircraft was stable immediately prior to the loss of airspeed indications and very quickly loses situational awareness.

Without careful attention to attitude and power, loss of control can quickly result. A pitch-up of 15degrees in a transport aircraft operating at FL350, if held and not reduced, is, for all intents and purposes, a loss of control.

Whether the PNF knew about and understood what the PF was doing is not known and not discussed in the BEA Update. We will know, I hope, in the upcoming Report.

Does this help?


Yes it does.

You seem to feel very strongly about "not following a procedure/rule" being a reason of not being an "intentional" climb.

Yours, and the reason posted by Lonewoolf - no additional throttle during the climb - and above all - perhaps not a surprise to you - the energy conservation calculation showing that the kinetic energy at FL350 and FL375, based on the BEA text are matching the climb potential energy, showing that no additional power was applied, are convincing.

With the risk of repeating what was perhaps already said, the implication of the calculation results is that while it shows that no additional power/throttle was applied during the climb, it also shows that no additional energy came from outside the A/C, like from the air turbulence providing additional lift.

However, what the calculation cannot show, is weather the air turbulence had a downward gradient, adding a downward force to the A/C weight, and thus delaying the A/C pitch-up response to the NU command, in spite of the correct response of the control surfaces.

The effect of this can be that the PF entered a gradually more forceful NU command, proportional with the delay of the A/C response, which resulted at the time of the change of air turbulence gradient into a sudden, much more aggressive pitch than intended, and a more aggressive climb at 7000ft/min.

A factor of surprise for such a sudden response may have been the cause of the delay to the ND command, slowing the climbing vertical speed from 7000ft/min to 700ft/min.

[PJ2]

You seem to feel very strongly about "not following a procedure/rule" being a reason of not being an "intentional" climb.
Yes I do, and there is one simple reason: an airline pilot lives by SOPs and "flies by the book." There are no "individual actions" anymore, in the cockpit of a transport aircraft. Cockpit discipline and crew coordination and communication in normal and abnormal circumstances is what keeps everyone safe when something bad happens. Remove that and the flight is at risk. It is no more complicated than that.

I am aware that there may be "energy for the climb without pushing the thrust levers up a bit", but that misses the point entirely. No matter how it was done, any pitch-up at all is absolutely the wrong thing to have happen and the expectation is that it would be resisted with all necessary force on the stick to maintain level flight with the thrust unchanged.
Yours, and the reason posted by Lonewoolf - no additional throttle during the climb - and above all - perhaps not a surprise to you - the energy conservation calculation showing that the kinetic energy at FL350 and FL375, based on the BEA text are matching the climb potential energy, showing that no additional power was applied, are convincing.

With the risk of repeating what was perhaps already said, the implication of the calculation results is that while it shows that no additional power/throttle was applied during the climb, it also shows that no additional energy came from outside the A/C, like from the air turbulence providing additional lift.

However, what the calculation cannot show, is weather the air turbulence had a downward gradient, adding a downward force to the A/C weight, and thus delaying the A/C pitch-up response to the NU command, in spite of the correct response of the control surfaces.

The effect of this can be that the PF entered a gradually more forceful NU command, proportional with the delay of the A/C response, which resulted at the time of the change of air turbulence gradient into a sudden, much more aggressive pitch than intended, and a more aggressive climb at 7000ft/min.Sorry airtren, I may be mis-reading your post but according to these paragraphs it appears that you believe that the pitch up itself was a necessary manoeuvre, and I cannot think of a single good reason why aft sidestick would be applied within seconds of the autopilot and autothrust disconnect. Assuming the event occurred in stable, level flight, it is unquestioningly the wrong response to a loss of airspeed information and a disconnection of the autopilot.

And while it is quite possible that the BEA Update did not include all communications between the PF and the PNF on a timeline, it appears to me that this pitch-up action took place unilaterally, without the PF announcing what he was doing, what the drill to be actioned was, an what the PNF was to do.

I am of the view, supported by the BEA Update that the aircraft was pitched up past 10 degrees attitude at FL350 and kept there with aft sidestick, instead of pushing the stick full forward and keeping it there as is the SOP for stall recovery.

Perhaps, as I have said, there are other reasons for the pitch up which were initially unintentional and beyond the immediate control of the PF. However, the BEA Update makes it clear that sidestick input was aft with a few momentary exceptions, commanding up elevator, from which the THS slowly followed up upon, as it was designed to do and the stick was held back during the approach to the stall and in the stall.

I think it is this initial pitch-up, and then the aft sidestick position at the entry into the stall and held during the stalled descent, with a momentary relaxation, that needs to be explained.

[takata]

@Takata
Do you recall the posts that AF did not install all of the available backup steam guages option on this a/c?
As far as I can remember, this was all about the optional BUSS (Back Up Speed System) not installed on AF fleet. Hence, this is not related to inertial references or standby gauges. In this regard, AF opted for optional ISIS as a backup instrument display.


The report does not explicitly state attitude failure. However it does not state that attitude indactions were all displayed faithfully. FDR did not record speed on right PFD, so maybe not the attitude.
Actually, the BEA report #2 explicitly ruled out attitude failure:
Fact/findings: None of the messages present in the CFR indicate loss of displays or inertial information (attitudes)
This fact was not challenged by further findings, including CVR and DFDR readings. What the BEA is stating in the last note as being the current pitch angle, at certain time, is comming directly from the same source used by the pilots. Even if ADIRU 2 (F/O's source) is not recorded, the way the system monitors the attitude sources (IR references) is ruling out that it could be at any time in error with the other sources recorded (ADIRU 1 & 3).


The BEA report does show errors on both ADIRU and ISIS. Having read some other incidents I recall that Airbus can give bogus stall warnings and PFD degradation under certain ADIRU failures (those 2 Airbus incidents near the Australian radar station?). IMHO the scant BEA reports do not eliminate the possibility of a degraded attitude indicator on the right PFD.
The BEA reports, as well as the fault sequence analysis, is showing that no attitude degradation of the PFD and ISIS ever occured during this flight.
PFD and ISIS are displaying a lot of informations, each linked with various functions. The faulty functions recorded in the ACARS CFRs (current flight report) is showing faults unrelated with aircraft attitude.
- ISIS failure: what faulted was the Speed/Mach function; specifically (now with further avail. data), it is showing that static pressure was at one point higher than total pressure (pitot/static probe 3 related fault); this happened between 0211:00 and 0211:59 (at this point, aircraft had already reached its top climb, 38,000 ft, and was certainly stalling).
- ADRIRs failure: the one reported by IR parts of the 3 ADIRUS is also related to probe issues: it is pointing that either values of pressure altitude, barometric vertical speed and true airspeed were invalid on the three ADRs (possibly all three cited values were wrong). As above, this happened between 0211:00 and 0211:59, same remarks.

Beside, Quantas issues with a faulty ADIRU was also unrelated to IR faults.


The list of 7 reasons are purely speculative.
Right, but basic speculations should be based on the whole dataset, not discarding a single information or pushing wilde interpretations of automatized systems which are basically highly predictibles (because they have been built to behave like that, this is a very deterministic process, unlike crew actions).


Probably a better title is "possible contributing factors to a general nose up/stick back". I was struggling with imagining the crew spending nearly 4 minutes looking at the +15 deg pitch and giving it generally stick back - sometimes to the stops. Which scenario(s) would you envisage to explain this?
When one reads many other reports (in whatever context) about human behavior in stressful circumstances, this is not very hard to catch up that a wrong initial analysis may surely lead one to sustained wrong acts. Here "the Crew" is a too strong term as for explaining the first sequence until reaching max altitude. This lasted no more than 40-50 seconds, Captain was in his bunk and PNF was certainly very busy with systems checks rather than monitoring exactly what the PF was actually doing, not even talking about him making some cool headed instrument scans.

[Dont Hang Up]

Yours, and the reason posted by Lonewoolf - no additional throttle during the climb - and above all - perhaps not a surprise to you - the energy conservation calculation showing that the kinetic energy at FL350 and FL375, based on the BEA text are matching the climb potential energy, showing that no additional power was applied, are convincing.


Really?

A simple conservation of energy calculation would show that a 3000ft climb requires a loss of 260 Knots of true airspeed.

gH = 1/2 x (V^2) where V is the speed change and H is the height change
So in metric units V=SQRT(2 x 9.8 x 914)
V=133 metres per second (approx 260 Knots decrease)

And that assumes a 100% efficient energy transfer - not usually provided by an aerofoil heading deep into the back of the drag curve.

So I would not be so sure that there was not a significant input of lift from the surrounding environment.

[Linktrained]

TAKATA #565

So for a few seconds PNF was busy - doing what ever was necessary.
And PF was flying by SS, using those instruments without warning flags etc.
No one had the spare ability to scan, for this short time, or to notice that the THS ( which we never touch - we let it do its own thing...) has trimmed in only one direction, not cycling as usual -- a little NU followed by a little ND.

So PF was busy, too.

[Alison747]

I think we have been around this one before. Hazlenuts39 has made a detailed analysis of airspeed in one of the previous threads.

I am mere SLF, but my maths says that kinetic energy would be based on TAS (kinetic energy does not know, or need to know, about air density).
A quick calculation on this basis would have the resulting speeds drop by about 20% for a ~900m climb - or about 260 knots (IAS) down to about 210. I believe this is consistent with the BEA report at the point that speeds returned?

[A33Zab]

If aerodynamically stowed, and absent hydraulic pressure, can they flutter?


Not as advertised, it is kept stowed by hydraulic lock internally.
Of course after degradation internal leakage could be introduced but this
was youngest A330 in AF fleet (MSN 660 age:4years 3 months).
It's position remains monitored even if locked by FCPC/FCSC command.


Also, RTLU. Is Rudder centered before limit is ennabled?

In AP mode rudder trim is deactivated. as last step after Eng. startup any rudder trim should be zeroed.


– RUD TRIM ............................................................ ............................................................ ......ZERO
If RUD TRIM position indication not at zero, press the RESET pushbutton.


RTLU and subsequent PTLU are active in all modes incl. AP, therefore deflection can never be more than RTLU will allow.

Any chance of (R) Rudder staying with the a/c all the way, without annunciated ECAM or ACARS rpt?

Not - by any change - for sure Rudder didn't departed while still in the air.

http://i474.photobucket.com/albums/rr101/Zab999/Rudder.jpg

Absence of any other Rudder / Hydraulic / HF message would be proof VS was still attached before impact.
Besides that, the THS actuator (taking the loads) is attached to frames that came with the VS.
If VS departed early, THS would be gone too!

Frames 86 and 87: failure of the horizontal stabiliser actuator supports

http://i474.photobucket.com/albums/rr101/Zab999/THSlugs.jpg



If jammed at (Right) would there be any ECAM, since the Rudder has (limited) authority anyway? Would the deflection be accepted as an input, not an anomaly?

In C(abled) rudder there is a "F/CTL RUD G(B)(Y) SERVO JAM" if any faulted.

[takata]

TAKATA #565
So for a few seconds PNF was busy - doing what ever was necessary.
And PF was flying by SS, using those instruments without warning flags etc.
No one had the spare ability to scan, for this short time, or to notice that the THS ( which we never touch - we let it do its own thing...) has trimmed in only one direction, not cycling as usual -- a little NU followed by a little ND.
So PF was busy, too.
Understand me well.
a) I'm addressing here the initial climb (pitch up) sequence => from 0210:05 to 0210:50 (45 seconds, during which altitude went from FL350 to FL375).

b) PF was flying by sidestick, but recieved from the start all the relevant PFD flags about his airspeed/flight law situation (he was not blind flying).

c) THS did nothing during this sequence, if adjusted, it would be by tenths of degree, not 10° (this happened during the stall sequence, much later).

d) PF was certainly fully busy at flying the aircraft : his roll (over)correction seems to have induced an oscillation which lasted until the top by rolling right and left, up to 10-12 degrees (left-right); there was at least a pitch up order, then later, insufficient ND orders to correct the pitch angle and climb trajectory (it continued until FL380).

e) I don't know more about respective actions taken by PF and PNF.

[Lonewolf_50]

airtrenWhat's this supposed to mean?
It means I better understand what you were telling me about how you experienced the altitude change. :\

The BEA text does not mention manual power/throttle changes during the climb time interval from FL350 to FL375. So, that makes the climb unintentional?

That would be my assessment.
Typically, when you undertake a climb, you change both power and attitude. (Or is that now taught differently? It's how I used to teach a climb ...)

Caveat: some have suggested that the PF thought he had an overspeed, based on display anomalies, so perhaps he thought to trade airspeed for altitude. Hard to say.

I don't think a type rated pilot at that altitude would (given the small window of suitable speeds) purposefully bleed off his airspeed to climb 3000 feet. I am of the opinion that a rated pilot would do as pilots are trained to do from day one: he'd use power and pitch attitude to perform a climb. Note, he'd been intending to climb earlier, as evidenced by their discussing why they could not climb yet due the temperatures not being suitable for an altitude change.

So yes, airtren, I am of the opinion that he climbed unintentionally. Granted, if his gauges showed a high airspeed, and an altitude less than FL 350, assigned altitude, you could argue that a stick only altitude correction (and airspeed correction) would be the response. (But wait, if you are in bumpy/turbulent air, you usually hold an attitude, you don't chase airspeed, nor altitude.)

Back to my old question: what did he see?
JD Rolling the plane to the left with up elevator is, I believe, a left turn input. If I'm right why'd the plane go into a fairly tight right turn?

Or, left wing up, nose up, is a correction to a right wing down, nose low, attitude. Whence that attidude? Not sure, but I find A33zab's post of interest.
A33zab
The MLA becomes active when the side stick is pulled more than 8°, and the load factor is more than 2g, in which case:

- The ailerons are deflected symmetrically upwards:
Max 11° added to Roll demand, if any.
-Spoiler 4,5 & 6 are symmetrically deflected:
Max 9° added to Roll demand, if any.
- Deflection is proportional to load factor in excess of 2g.
With the above in mind, is there a good reason to believe that AF 447 experienced a g load > 2g? (Does this take us to intermittent and substantial updrafts and down drafts? They did expect to hit some turbulence,)

To follow that thought, are you suggeting a possible malfunction or degradation of the MLA function you spelled out? :confused:
(Hence, PF having to correct a roll in Alt Law ...)

If this happened, might it have left no audit trail in ACARS or FDR?

[grity]

So I would not be so sure that there was not a significant input of lift from the surrounding environment.
you calculate with stopped turbines, (correct, a stone need a start speed of vertical 134 m/s to reach a delta-high of 914m against gravity...... he need 13,6 sec.)

but with decreasing speed during climb no longer every energie of the turbines is required against air drag, so they provide more energie into the kinetic system....

[Lonewolf_50]

In case anyone missed 3holelover's question
Q for Pilots:
This question I address to the pilots among you:

Assume you're in IMC cruise, at night, and expecting some turbulence... Your instruments start "acting up", your AP drops, your ECAM/EICAS starts showing a cascade of failures, your PFD is showing various flags and missing data, and what data is displayed looks wrong to you..... among the various messages are intermittent stall warnings, but your airspeed has already been notably erroneous or absent...

.... you start to feel light in your seat. ... you soon see altitude displays that appear as if you are indeed falling fast. ... ... ... If you were still experiencing something less than 1g, would you believe your aircraft is diving, or stalled?

Well, if I believed my attitude indicator ...

If my nose attitude was nose low, I'd believe diving.
If my nose attitude was nose up, I'd believe stalled.

If I didn't believe my attitude indicator, you ask a very good question, and I am not sure what my reaction would be.

Your question doesn't include any reference to my primary scan instrument.

Was that intentional? :confused:

and what data is displayed looks wrong to you

By the way, what's my back up Attitude indicator showing?

What is my copilot's attitude indicator showing?
I'd sure as hell ask him.

A few threads back, I discussed the problems of a spin on instruments. Not easy.

This scenario looks equally difficult.

Go back to the first thread on this crash.
One of the common answers provided then was "fly pitch and power"

[grity]

PJ2 True, the ICAO Flight Plan......... SALPU at which a climb to FL370 was flight planned, with the Mach remaining at M0.82,

UN873 SALPU/M082F370 beside the missing ATC clearance to deviat.... if you follow the plan and do the climb from F350 to F370, with how much pitch would you normal do the climb?



and at what place behind SALPU did they start their climb?
http://cimss.ssec.wisc.edu/goes/blog/wp-content/uploads/2009/06/090601_met9_ir_zoom_anim.gif

[Linktrained]

Takata

Thank you for making clear to me the lack of movement of the THS in this, the initial phase.

I made no suggestion about " blind flying" but I assumed that some at least of the relevant flags on the PDF about the relevant airspeed law situation had not appeared much prior to the pitch-up.

( An earlier generation accident report to a very different aircraft, had pointed out that a good ILS procedure had been done but with the ILS switched off... That was why they had had the accident. The pilot had been so used to seeing the OFF flag that, for him, it was "normal".)

[3holelover]

Thanks Lonewolf.

Was that intentional?

Yes. Partly because we don't know what he saw, and partly because his actions (the one's we've been told about so far) lend credence to the notion he either had no attitude display, or he may not have believed what he saw... and the only tidbits of conversation we know of express doubt: "we have no indications", "je ne comprend rien".

So if that primary display is either absent or doubted, there's my question. -if he did indeed see 40-60 degrees nose up, it would appear from his actions that he wasn't buying that. - and I can well imagine he was looking at a number of rather confusing things - including flagged or absent displays - that could have caused doubt...

Having only had ab-initio instrument flight training myself, I am aware, at least, that one needs to disregard what one "feels" the a/c is doing, and trust your instruments.... But when your confidence in those instruments has been shattered, I can see someone resorting to actions based on what their body tells them.
So, I wonder what most pilots would conclude from that feeling?

Hopefully the CVR will enlighten us as to any further talk of their displays...?

[Graybeard]

The BEA reports on 447 remind me of the US Constitution. The Constitution is sufficiently vague that we have a Supreme Court that continues to interpret its meaning 222 years later.

[CONF iture]

How come BEA didn't know the takeoff cg was 23% at time of first report? Why didn't they do your math?
23% is actually mentioned on P18 in the first interim report.
To be honest, I didn’t do any math, just practical observation. Maybe our BEA Experts will comment on how their estimated CG was that far …


it probably already is due to modified UAS procedures promulgated
Hopefully guys on the flight decks are discussing the event, but on the procedure side, nothing has changed. The very same confused UAS procedure remains … and remains ...

In our AF447 case, with a triple ADR fault, those protections are lost as well, and it seems very bad as they could have prevented this crash.
Where do you get that certainty of a triple ADR fault from ?
To the contrary, Low and High Speed Stabilities may well have been available.


I still believe that a BEA hastily release of raw data would have caused more harm than good. Many things really need to be checked and cross-checked before reporting them to the public. Without expert analysis, it may be very harmful to everybody. Any inquiry needs time, patience and in depth processing in order to avoid mistakes and wrong conclusions.
Conclusions, whatever they are, whenever they come, belong to the BEA, but thinking has to belong to everyone.
Right now, the real ones to suffer are the victim's families , and especially the pilot's families, thanks to the last BEA note ...
Forget about the public, forget about us, we're not suffering we're just technically captivated, victim's families are ... and it appears they are also the ones to request the data.

[Lonewolf_50]

the only tidbits of conversation we know of express doubt:
"we have no indications", "je ne comprend rien".
That, and the call for the Captain to return to the cockpit. That's an SOS call, as I see it.

But when your confidence in those instruments has been shattered, I can see someone resorting to actions based on what their body tells them.

If I am IMC, and I don't believe any of my instruments, the thought that comes to mind is "I am well and truly :mad: ed." I then try to make small control movements to get something to move, or change, that makes more sense than what I am seeing, or not seeing, at the moment, and I try to figure out "how do I get to VFR conditions, and how soon can I do that?"
So, I wonder what most pilots would conclude from that feeling?

Try anything that might work, as what's going on now isn't working?
Task the PNF to:
Reset a few circuit breakers to get something to work again?
Cycle some switches on and off so that an instrument may work again.
What I need is:
Attitude reference
Altitude reference
Power reference
Airspeed (but I can work around that if I can get an attitude reference)
VSI
Turn and Slip

Give me what you can, PNF, that's why you are there.

But of course, maybe before we start turning things on and off ...

If your instruments are working, you take the controls, and I'll back you up.

That may be what finally happened somewhere near 10,000 feet on a dark and stormy night. :(

[henra]

A kinetic versus potential energy conservation calculation shows that the BEA indicated height delta (2500 ft from FL350 tgo FL375) checks against the BEA indicated delta speed of 60 knots (from 275 to 215 knots). Same is true for FL380, and 185 knots.

dEk = Ek (275knots) - Ek(215knots) = dEp (2500ft)



Not wanting to nitpick, just for the sake of correctness, it has to be noted that the 275kts and 215kts were IAS.
For any kind of energy calculation you have to take TAS.
In this case that would be approx. 495kts and 390kts, repectively.

Edit:
This corresponds to ~4200ft but is still very well explicable by the increased drag of the maneuvers. So I don't contradict the statement that the kinetic energy figures are plausible.

[PJ2]

Hello 3holelover;

Didn't mean to ignore your question! I sometimes struggle with hypotheticals because I wasn't there.

That acknowledged...

I think Lonewolf_50's last line says it all - fly pitch and power.

That is the drill for a UAS abnormal and that is what will keep the airplane stable while the problem gets sorted out. I think that every other response will likely destabilize the aircraft and make things much more difficult to recover from.

To your question regarding "what would one do?", faced with the losses you mention, I don't for one second pretend to know because I've never been faced with the problem. So hypothetically from my armchair, obviously given the views I have expressed in the past I would do nothing except maintain pitch and power and call for the UAS checklist. The memorized portion of the UAS drill requires that one "level off and troubleshoot" and "doing nothing" (except maintaining control) is being done.

If I began feeling "light in the seat" I would ask what other crew members were feeling while checking the aircraft attitude on the displays I had and try to maintain level flight. Reading the standby in turbulence is a real challenge by the way - the thickness of the little airplane symbol (on the steam instruments) is about 2deg of pitch...a lot when one needs to fine-tune pitch! The job of maintaining stable flight is challenging in turbulence anyway but it must be done.

For the following discussion, we need to understand the layout of the A330 cockpit to see where the following panels are. Here is a rough diagram:


http://www.smugmug.com/photos/i-FXRLjPR/0/L/i-FXRLjPR-L.jpg


In terms of available attitude information, if the artificial horizons (all 3) are failed it means that IRUs 1 and 2 have failed so, (if I had the presence of mind...again, from the comfort of my armchair), I would ask the PNF to switch the source of the attitude information to the #3 IRU, (ATT HDG, Capt or F/O ON 3), (see diagram below).

It would be unlikely that all 3 IRUs would fail, and there are no ACARS messages that indicate any IRU failures.




http://www.smugmug.com/photos/i-ZZdf7Db/0/L/i-ZZdf7Db-L.jpg



But let us continue the hypothetical case.

If a PFD display had failed, (mine), I would transfer control to the PNF if he had an attitude display that agreed with the Standby and call out pitch and bank information to help him maintain level flight while we got the QRH out for pitch-power settings.

I would leave the ECAM messages alone until control was assured and stable flight established - which means, when the QRH UAS drill and checklist are completed.

In the A330, one can switch data sources to another DMC (Display Monitor Computer - see schematic below).

So, if one, two or all of the IRUs were working but one's own DMC had failed, one can switch DMCs using the EFIS DMC Control Panel to select either the opposite side display or the #3 display.

One can even toggle one's own PFD information so that the PFD and ND exchange displays in case one's own actual CRT display has failed.

Again, it is unlikely that all 3 DMCs would fail. Here is the DMC switching panels which are located on the far left and right ends of the glareshield. the top knob has 3 selections: "NORM" for one's own DMC, #1 or #2 for the opposite side DMC, and #3 for the backup DMC.




http://www.smugmug.com/photos/i-CMgBstQ/0/M/i-CMgBstQ-M.jpg




In brief, for all attitude information to have been lost to the crew, all 3 IRUs would have to have failed, or all 3 DMCs would have to have failed or all 4 screens would have to have failed (PFD & ND information cannot be displayed on the ECAM and SD displays). To see how all this fits together, here is a schematic of the entire EFIS control and display system:




http://www.smugmug.com/photos/i-qhQgWwf/0/L/i-qhQgWwf-L.jpg


Once the attitude information had been regained, maintaining wings-level is paramount then maintaining about 2.5deg pitch attitude is next.

After all this trying, if one still doesn't have attitude information, it is a very bad day and very likely a loss of control, probably a spiral dive, would follow. I think it is reasonable to say that one cannot maintain level cruise flight in an airliner solely by the seat-of-the-pants.

I say a spiral dive and not a stall because maintaining wings completely level without any attitude information (external or internal) is far more challenging in the short term, than maintaining a level pitch attitude. A small amount of bank will start a turn, and also cause the nose to drop and the spiral begins, and quickly develops and tightens because the A330 is so clean and "slippery".

Even in general aviation it is well understood that if a pilot with little or no instrument training loses visual reference with the horizon a spiral dive is the most common outcome. The most well-known event of this kind was John Kennedy Jr's accident some years ago. That was the reason for the introduction decades ago of the requirement for some instrument instruction even at the private pilot level. So loss of attitude information without visual reference to a horizon almost guarantees loss-of-control of some kind, whether a high-speed spiral dive (very likely) or a stall, (less likely, for reasons given).

The BEA Update doesn't state that the #2 PFD attitude information is not recorded. However, the Update does clearly provide information on the bank and pitch attitudes throughout the report and this information had to come from somewhere. I think it is reasonable to assume that if the data was available on the SSFDR, for the reasons given above regarding failures of redundant systems, it was displayed on one/both PFD(s) and ISIS. There are no ACARS messages indicating failures which would prevent such display.

I think to claim that the pitch-up was the result of the PF reacting to a display that was different than the PNFs or the ISIS is not reasonable for two reasons: a) system redundancy and absence of failure messages, and b) the PNF would either have the same "wrong" display or would react and call out his own display showing something different. Also, at what time would such a failure have occurred? There is no connection between the pitot failures and a failures of attitude displays.

I fully realize that I am inferring a great deal here but I am also trying to think about your hypothetical scenario logically. If we are to think hypothetically, at least the hypothesis must be internally consistent - we can't just say this and that is "possible" without accounting for the design of the aircraft and its systems which preclude some scenarios.

I'm completely open to alternate explanations of the pitch-up but the explanations have to make sense and withstand reasonable objections.

At some point there has to be a rational explanation that makes "if-then" connections, ideally all the way back to the originating event at 02:10:05 even if some of those connections may be tenuous.

I know that isn't possible at the moment because we all have the same bit of information from the BEA Update. But some things may be inferred, (admittedly, some more "loosely" inferred than others).

I'm not stuck on the notion that the initial aft-movement of a sidestick was intentional. But at some point, first the initial pitch-up, then the continuing aft-backstick must both be explained.

I hope this is of some use 3holelover...as I say, it's all armchair work but those guys had to do it for real. As I have said many times, discussing crew actions is not "blaming the crew". In investigative work there are no "off-limits" areas however, and that can come across as "blaming". For reasons we're all familiar with, that unfortunately seems to be a way our culture thinks about these things.

Lonewolf_50;
Task the PNF to:
Reset a few circuit breakers to get something to work again?
Cycle some switches on and off so that an instrument may work again.Yes, exactly. Although there are no circuit breakers that would accomplish this purpose in the cockpit, (the FMGEC cb's are on the overhead but they wouldn't help), the switching capabilities that I discuss above would be of immense help in any attitude failures, so long as there is attitude information available from an IRU.

[henra]

gH = 1/2 x (V^2) where V is the speed change and H is the height change
So in metric units V=SQRT(2 x 9.8 x 914)
V=133 metres per second (approx 260 Knots decrease)


Hmm, I'm afraid you've got a little quirk in your calc.

Energy loss is 1/2 (V1^2 - v2^2) which is quite a different thing from 1/2 (v1 - v2)^2.

You might want to recalculate with the adapted formula and will then come to the conclusion which has been accepted here that the energy transformation matched quite OK.

[takata]

Hi CONFiture,
Where do you get that certainty of a triple ADR fault from ?
To the contrary, Low and High Speed Stabilities may well have been available.
Quite simply if, at any point, you've got 3 valid ADRs and a failure makes those 3 ADRs to be rejected by all PRIMs and Autoflight System (AFS)... it will certainly be called a triple ADR fault. That is what happened starting at 0210:05, in all certaincy (this is also stated as a fact from the 1st BEA report).

This relevant fault was: PROBE-PITOT 1X2 / 2X3 / 1X3 (9DA).
Its meaning is quite clear: total pressure was out of boundaries and different at each probe-pitot source (9DA1, 9DA2, 9DA3) and the following consequences are well known on ADRs output channels as well as with other systems (A/FLT, F/CTL, NAV) using those values.

Hence, from this point, ALT2 without valid airspeed/Mach and SPEED LIMIT FLAG on PFD make it quite certain that Low and High Speed Stabilities were NOT available.

However, you do need to experience complete AC electrical failure to get there.
Of course, you are right about that (batteries). The above quote sumarizes precisely what I meant by "complete [AC] electrical failure".

[Lonewolf_50]

henra:

This corresponds to ~4200ft but is still very well explicable by the increased drag of the maneuvers. So I don't contradict the statement that the kinetic energy figures are plausible.

If they are flying in a column of air that was moving somewhere betwen 1-2000 down (a down draft) you might get to about 3000 feet up with your figure there. ;) Just a thought.

[A33Zab]

Quite simply if, at any point, you've got 3 valid ADRs and a failure makes those 3 ADRs to be rejected by all PRIMs and Autoflight System (AFS)... it will certainly be called a triple ADR fault. That is what happened starting at 0210:05, in all certaincy (this is also stated as a fact from the 1st BEA report).

I will disagree with the statement "a failure makes those 3 ADRs to be rejected"
Out of 3 sources FCPC can reject only 1 outlier ADR, but the other 2 remain because FCPC is not able to determine which one or even both are delivering wrong information.
If both keep on delivering different information for more than 10s the NAV ADR DISAGREE message is triggerd. This message was not present @ 02:10:16 or subsequent seconds but ca. 2 minutes later.
The first UAS was only transient, ADR 1 lasted only few seconds, ISIS (ADR 3) was absent for nearly 1 minute.

The NAV IAS DISCREPANCY message, triggered when there is a difference in ADR1 (LH PFD) & ADR 2 (RH PFD) was not present.
ADR 2 therefore must have been (+ or - 30Kts) with ADR 1 at that time and was - like ADR 1 - only absent for few seconds (9s or less).

As said the NAV ADR DISAGREE message is presented because crew has to make a decision to elaborate the ADR in error by switching off this (or multiple ADRs) so it will not be available for the FCPC also.


This relevant fault was: PROBE-PITOT 1X2 / 2X3 / 1X3 (9DA)
Its meaning is quite clear: total pressure was out of boundaries and different at each probe-pitot source (9DA1, 9DA2, 9DA3) and the following consequences are well known on ADRs output channels as well as with other systems (A/FLT, F/CTL, NAV) using those values.



Same for this failure message, in fact you should read: PROBE-PITOT 1+2 or 2+3 or 1+3 (9DA?).
Meaning there are 2 or more PITOT-PROBES affected but BITE/CMC can't determine which 2 (or more) are faulted.
This fault is indeed correlated with the first UAS event but same message would have been correlated to the second UAS event @ 02:12 however only the first occurance will be recorded en transmitted to CMC/CFR/PFR.

[takata]

Hi A33Zab,
for this failure message, in fact you should read: PROBE-PITOT 1+2 or 2+3 or 1+3 (9DA?). Meaning there are 2 or more PITOT-PROBES affected but BITE/CMC can't determine which 2 (or more) are faulted.

Which is also exactly my reading of the fault:
total pressure was out of boundaries [meaning that ADRs polled airspeed value dropped by 30 kts in one second or less] but was different at each probe-pitot source (9DA1, 9DA2, 9DA3)

Then, your explanation is the same than mine : the system can't dertermine which source (pitot-probe) faulted, because all 3 values were at first valid and coherent (condition for triggering this fault and monitoring), then diverged without remaining consistant with each others, hence, there was NOT an ADR DISAGREE message that could be triggered at this point (0210:05). The system was not able to eliminate the outlier ADR during the speed monitoring sequence (DISAGREE condition false: elimination of 1 ADR and other two ADR imputs different). Consequently, all three ADR output would be rejected both at PRIMs (FCPC1 & 2) and AFS level (no matter if one ADR output could have been valid).

Also IAS DISCREPANCY would be triggered if PFD 1 & 2 readings were showing a difference of at least 16 kt during some time. This condition may not have lasted long enough for doing so, hence no ACARS if such fault would be sent (not sure) after consolidation (2-3 seconds). It doesn't mean that this ECAM wasn't displayed at all in the cockpit, but it could have been intermitent during a very short duration. Also, there is nothing in BEA narrative telling us that the crew noticed something before AP disconnected. In many other cases, crews were alerted by experiencing airspeed fluctuations; it seems not to be the case here: it was brutal.

Consequently from those conditions, I'm deducing that ADR2 was also faulty and could have been the very first to drop. This is fully coherent with an environmental fault affecting the same probes, the same way, in a very short time interval.

The first UAS was only transient, ADR 1 lasted only few seconds, ISIS (ADR 3) was absent for nearly 1 minute.
Your conclusion doesn't match with the data:

In BEA last note :
1) The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS).

2) The inconsistency between the speeds displayed on the left side [ADR1] and on the ISIS [ADR3] lasted a little less than one minute
From the BEA narrative:
- 0210:05 -> ADR1 followed by ADR3 sharp fall;
- 0211:06 -> ADR1 & ADR3 speeds coherent and "valid" again => 1 minute error;
- 0211:40+ few seconds -> [I]all of the recorded speeds became invalid again (1). Note 1: When the measured speeds are below 60 kt, the measured angle of attack values are considered invalid and are not taken into account by the systems. When they are below 30 kt, the speed values themselves are considered invalid.

Consequently, the ADR DISAGREE message triggered (0212 => 0211:40+) is due to this second (or later) speed/alpha issues with ADRs, at which time conditions were different as 1 ADR would have been rejected at FCPCs level.

Your above conclusion doesn't match also with the first BEA report (see p.54-55) about this fault explanation:
"The presence of the F/CTL RUD TRV LIM FAULT message indicates that EFCS monitoring had been activated and that the alternate law had been maintained."
Hence, it was already obvious from all the systems declared INOP that the first probe fault was NOT transient and it was confirmed by the DFDR showing that the inconsistency lasted about 1 minute on both ADR1 & ADR3 (more than enough for a triple ADR fault condition).

You should also keep in mind that this sequence is not from a PFR (Post Flight Report) but a CFR/ACARS, hence, everything is not sent by this mean (e.g. no cockpit Stall, overspeed warnings). Failures are labelled following their logical compilation order and could have covered various system messages having the same ATA header => 341.

You may want to list every ATA 341 fault at FCPC and AFS level and see what they could have been during this 1 mn correlation window opened.

Also, AIRBUS acknowledged this PROBE-PITOT fault as being possibly part of an UAS signature, even if not the more frequent:

TELEX - OPERATORS INFORMATION TELEX
TO: A330/A340/A340-500/A340-600 Operators
SUBJECT: ATA 34 - REQUEST FOR INFORMATION CONCERNING IN-FLIGHT UNRELIABLE AIRSPEED
OUR REF: SE 999.0049/09/VHR dated 09 JUN 2009
[...]
2/ TYPICAL SIGNATURE OF UNRELIABLE AIRSPEED
To be sure that Unreliable airspeed events are correctly identified, please report events corresponding to the criteria as follows:
- Crew report indicates loss or discrepant IAS (Indicated Airspeed) on CAPT and/or F/O PFD and/or Standby Airspeed indicator (ISIS).
- Typical ECAM Warnings were seen:

NAV ADR DISAGREE
NAV IAS DISCREPANCY
F/CTL ALTN LAW
F/CTL RUD TRV LIM 1(2) FAULT
AUTO FLT AP OFF
AUTO FLT A/THR OFF
STALL WARNING (audio call-out)
AUTO FLT REAC W/S DET FAULT

- Fault Message "PROBE-PITOT 1+2/2+3/1+3" was possibly also seen.
- Maintenance report indicates that event was NOT due to a system failure.


The TBS (see below) mention about this fault "Disagree of the Pitot Probe Data in the FCPCs" that if the fault was transient, F/CTL ALTN LAW, would have been displayed only few seconds in the cockpit (then return to NORMAL, while an acknowledgement from the crew is also stamped 0210:16)- Beside, there would be no subsequent ECAM warnings and flags on PFDs.

34-11-15 EFCS2 :
TASK 27-91-00-810-822
Disagree of the Pitot Probe Data in the FCPCs
1. Possible Causes
...pitot probe
2. Job Set-up Information
...A. Referenced Information
.........AMM 34-11-15-000-801 Removal of the Pitot Probe (9DA1, 9DA2, 9DA3)
.........AMM 34-11-15-200-801 Inspection/Check of the Pitot Probe (9DA1, 9DA2, 9DA3)
.........AMM 34-11-15-400-801 Installation of the Pitot Probe (9DA1, 9DA2, 9DA3)
3. Fault Confirmation
...A. Test
........(1)Not applicable, you cannot confirm this fault on the ground.
4. Fault Isolation
...A. If the crew made a report that the F/CTL ALTN LAW or F/CTL DIRECT LAW warning was shown on the EWD for some seconds only:
.........- no trouble shooting is necessary.
...B. If the F/CTL ALTN LAW or F/CTL DIRECT LAW warning is shown and stays on during the flight:
.........(1)Do the inspection of the pitot probe (9DA1, 9DA2, 9DA3)
.........AMM TASK 34-11-15-200-801
.........replace the defective pitot probe (9DA1 or 9DA2 or 9DA3)
.........AMM TASK 34-11-15-000-801 and AMM TASK 34-11-15-400-801

[bearfoil]

A gracious good morning, takata.

Thank you for such specific and important data.

You mention that BEA do not state any "recognition" (by pilots) of noticeable a/s problems prior to a/p loss. You also mention that many prior cases of UAS did have such recognition by pilots. You call it 'brutal'. Can you explain?

It underscores the suddenness of the auto loss to the crew. I cannot recall a discussion of events probable at a/p drop before. Your fine tuning of the FCS' reactions and mitigations are enlightening.

[Ian W]

@3holelover
but that isn't going to hold me back from saying I think some of you (Bearfoil) are appearing to be frighteningly closed to the notion that the airplane may well have been just fine, but the PF screwed the pooch.

Good grief man, from what we "know" so far, it's the most logical solution to all questions.

I do believe you have just proven one of Bear's previous points. :hmm:


Perhaps what you meant to say that the PF/PNF were put into cognitive overload by the system failures, sequence of error messages, failed indications and aircraft behaviors and changes of laws.

You might do well to read the seminal paper by Reason on the swiss cheese model of error propagation. There plenty of slices of holey cheese to pass around in most aircraft accidents and incidents.


(Google "Reason Swiss Cheese Model" there are lots of hits to read)

Edit:
As an example read the prescient introductory paras in this wiki entry - Organizational models of accidents - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/Organizational_models_of_accidents)

[HazelNuts39]

In many other cases, crews were alerted by experiencing airspeed fluctuations;Is this your reference? -
BEA Interim #2, 1.16.3 Study of losses of or temporary anomalies in indicated speeds:
The recordings of total or static temperatures(9) show increases of ten to twenty degrees during the event, which sometimes began before noticing any speed anomalies, except in a case where the increase was lower;

[takata]

Hi Bearfoil,
You mention that BEA do not state any "recognition" (by pilots) of noticeable a/s problems prior to a/p loss. You also mention that many prior cases of UAS did have such recognition by pilots. You call it 'brutal'. Can you explain?
In many UAS events, (but not all), the attention of pilots was at first attracted by either airspeed fluctuations on PFDs, either autothrust changes before autopilot disconnected. In one case, it is mentioned that CAS made several yo-yos on both PFDs. In those recorded cases with fluctuations, this NAV IAS DISCREPANCY message would tilt on ECAM. It means that airspeeds displayed on each PFDs are outside a certain range, which is constantly monitored by the system, while certified instrument possible variations at cruise, depending on source, altitude and speed are below Mach 0.009 (=3-4 kt above FL350).

In fact, I noticed an incoherence about this NAV_ADR_DISAGREE message: In the documentation, like A33Zab mentioned it above, it is stated that in case of 2 or 3 ADR fault, this ECAM would be displayed, while I believe this is only true in the first case (2 ADRs) because it is contradictory with NAV_ADR_DISAGREE condition which needs first an ADR to be rejected by the PRIMs (this rejection of the "outlier" is discrete). Hence, in case of triple ADR fault happening in a very short time, without a single ADR drifting earlier from the other two, this condition won't be true.

Our case signature of this first ADR fault (0210) is a triple one. Beside, it is much more logical with the Probe-Pitot fault which is also a triple one, the system being unable to determine which one of the three has faulted. How could the system "eliminate" the first ADR by itself?

Hence, this is why I'm saying it was brutal as there was a fast ice build-up, a sharp speed drop, without erratic speed readings, affecting all the probes in few seconds that caught the crew by surprise. No warnings due to autothrottle behavior or IAS DISCREPANCY tilting on ECAM display.

But please, Bear, don't rebounce on my posting in order to advance your usual "structural" failures fantastic theories, as this was a genuine ADR fault due to severe probe icing in all certaincy.

Their huge problem was that when the first ADR fault self-cleared at 0211, a second followed at 0211:40 (invalid parameters), then possibly a third one at 0212 (ADR DISAGREE)...

Hi HN39,
reference?
See the Expertise Judicial report link I posted few pages back. (here it is: rapport d'expertise Rio-Paris (http://www.scribd.com/doc/56400906/rapport-d-expertise-Rio-Paris))

[bearfoil]

Not really fantastic, at least in the case of 'superbe', no?

At last I believe I am tracking you, and surprised at how much we agree.
That three probes would block simultaneously, in rate as well as time frame, seems fantastic to me. How quickly does a/p respond to declining a/s's, and for how long is it "allowed" to? I am starting to suss the Law, so thanks to you, I have some actual data to consider, phrased in language I get.

[takata]

How quickly does a/p respond to declining a/s's
What is monitored is CAS value, by two independant systems working in parallel: actually -> 0.45 second at autoflight level (1) and 1 second at FCPC level (2).
1) Fluctuation fo CAS resulting of 20 kt change in 0.45 seconds will cause A/P to disconnect, and further A/FLT systems if confirmed.
2) Fluctuation of CAS resulting of 30 kt change in 1 second will cause ALTERNATE LAW 2 to trigger, and further F/CTL if confirmed.

The next step is a 10 seconds monitoring test which retains the last valid CAS (median value of 3 ADRs) for comparison with CAS value at the end of this time window.

[bearfoil]

Ahhh.... So the a/c flies for ten seconds on one read? Is that the ten second interval I suss @ 2:10:16 "so.....we've lost the speeds, Alternate Law?" (PNF?).

Am I close? If the a/c was ten seconds into flight calculated on one airspeed, what could the PF/PNF be seeing when the reads update?

Do they? Is PITCH and POWER any more difficult to acquire if the a/c has degraded in assiete, during "monitoring"?

thanks takata :ok:

[takata]

Ahhh.... So the a/c flies for ten seconds on one read? Is that the ten second interval I suss @ 2:10:16 "so.....we've lost the speeds, Alternate Law?" (PNF?).

Am I close? If the a/c was ten seconds into flight calculated on one airspeed, what could the PF/PNF be seeing when the reads update?
NO again, you are far!
Autopilot disengages and ALT2 is triggered immediately without waiting for 10 seconds confirmation.
CAS_System is used by aircraft avionics systems (autoflight, flight controls); it is NOT displayed on PFDs.
* Captain's PFD: CAS1 = ADR1 = real value displayed if > 30 kt.
* F/O's PFD: CAS2 = ADR2 = real value displayed if > 30 kt.
* Standby: CAS3 = ADR3 (not displayed, in replacement for CAS1 or 2)
* ISIS: CAS3bis = same probes as ADR3, but analogical values (no ADMs computation) = real value displayed if > 30 kt.

Consequently, if Captain's Probe-Pitot becomes clogged and ADR1 airspeed drops immediately from 275 kt to 60 kt, Captain's PFD will actually display 60 kt even if the system CAS will retain the last valid value of 275 kt for monitoring all ADRs output during 10 seconds following the fall of ADR1. Same for F/O, ISIS with their respective ADRs.
That's how RTLU would retain the last valid airspeed if the 10 seconds airspeed test failed but, if the test is passed, it will function normally.

[JD-EE]

bearfoil, the definitions of conspiracy follow:

conspiracy (plural conspiracies (http://en.wiktionary.org/wiki/conspiracies#English))


The act of two or more persons, called conspirators (http://en.wiktionary.org/wiki/conspirator), working secretly (http://en.wiktionary.org/wiki/secretly) to obtain some goal, usually understood with negative connotations (http://en.wiktionary.org/wiki/connotation).
(law) An agreement (http://en.wiktionary.org/wiki/agreement) between two or more persons (http://en.wiktionary.org/wiki/person) to break the law at some time in the future.
A group of ravens (http://en.wiktionary.org/wiki/raven).


Now, in the sense of the second definition do you believe there is a conspiracy involved in BEA?

I also personally wonder if you are still insisting things fell off the plane or quit working without any evidence in the ACARS messages, do you?

[JD-EE]

The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb.

A factor of surprise for such a sudden response may have been the cause of the delay to the ND command, slowing the climbing vertical speed from 7000ft/min to 700ft/min.

More like, could a lack of response to an initial smaller NU response have led to continued NU application until the sudden response happened. They were in turblence, or chaotically moving air. Suppose that air movement was enough to momentarily negate the response of the aircraft to the pitch change. That might have altered the PF's response.

So he rather rapidly climbed and then reduced the climb rate. Pitots cleared. At least PNF got airspeed and both received a stall warning. And it all balled up at that moment with the PF response.

As an aside I'll be interested when the report comes out of PNF was kept abreast of what PF was doing as he did it, "I'm climbing for a little more altitude to (whatever)." If such statements as he was acting were not made that suggests to me a potential cultural problem for the team environment in the cockpit.

[JD-EE]

Lonewolf_50, re A33zab's remarks note the bit about speed > 250 kts.
The load allevation is only available:
CAS > 250 Kts
FLAP LVR = 0 position
In NORMAL or ALTERNATE LAW.With speed lost could MLA function at all?

[JD-EE]

but with decreasing speed during climb no longer every energie of the turbines is required against air drag, so they provide more energie into the kinetic system....

That is why my initial calculation was based on zero speed with a delta. I used the fact that the plane was in a stable state with respect to power and drag. Then I calculated an energy tradeoff for the change in altitude. Admittedly this is at best a first approximation. Nonetheless, that was not accepted around here. Either calculation has a reasonable chance as a first approximation to what happened. The plane was in heavy turbulence moving through chaotic winds.

Above I mentioned it may have received stick up in response to a down draft, the plane then moving into a strong updraft and surprised PF. The chaotic winds they were going through may preclude a really accurate assessment of the energy tradeoff. It is suspicious that the number comes out so close to what was apparently observed.

[bearfoil]

I am flattered you seem so intrigued by my possible bias. My bias is in opposition to:

Lack of complete disclosure, something I anticipate; for now, no harm no foul.

Cossetted product: "show your work"......

An anal retention of data, for as yet "historically ill-defined purpose"...

Secrecy, which implies a mistrust: of the Public, the industry, or themselves.

Evidently, an anti-mission "blunder", (the note) that was used by the public to assign blame, via urban myth, counter to BEA's charge not to assign it.

This "blame by public proxy" is despicable, not a mistake, and advantages a Party to lawsuit and potential criminal prosecution. As such, it is anti social, and anti democratic.

I am all too aware of the standard issue "support structure" in rapt attendance to an authority that has methods that are outdated, parochial, and serve not the best interest of the Public Safety.

Denial is not a river in Egypt.

what are your thoughts?


aside: As to: MLA. Airbus would not exempt the final protection (load) simply because of a faux CAS. Give credit where due.

[JD-EE]

henra, grity mentioned the aircraft's thrust. That's a stable system. So the real answer is probably between the two calculations you give. I'd suspect it is closer to the square of the delta velocity. (In fact I did a long ways back.)

[JD-EE]

Complete, 100%, disclosure is neither needed nor proper. Some things the public does not need to know and in the interest if the families involved should not be disclosed publicly. (Much of that data should be disclosed to the individual family if they wish.) This data is not needed to further the investigation to assign a cause not a blame.

It is neither BEA's job nor intent to assign blame. Therefore assigning blame with an incomplete data set and no serious knowledge of what caused the accident is certainly counter-productive and highly improper.

We have enough data to conjecture about cause. It's pretty obvious that the crash happened because (cause) the plane reached a full stall condition all the way to FL0. Then we ask, "what caused it to enter that stall condition?" We walk up the branching chain of possible events pruning out any potentially possible events that don't match the data on hand. This is what BEA is doing with a fuller deck of cards to play with. (I get giggles imagining one of the investigators reading this thread knowing things we don't and admiring the flights of fancy on all our parts.)

I see no legal definition conspiracy taking place. So far I see a remarkably open BEA providing enough data to the public for two serious purposes, to put down speculation and let the public know the level of data BEA is working with as reassurance they're on the job. We're taking this a whole lot further than BEA. And out of our discussions may come some valid criticisms of cockpit culture, training, system design, and hardware. (That's more or less my current sense of probability of serious criticisms. I'm biased, of course.)

Your postings seem to indicate you do see a conspiracy in the legal sense of the term. And you seem to presume things can fall off the plane in flight with no indications to the crew that get recorded in flight recorders or the ACARS message stream. This was amusing at first. It's gotten tedious.

I also see you being all over the map with an intent, conscious or subconscious, of someday being able to say, "See, I predicted the answer." I'm sorry I do not see the level of serious regard you may be giving the problem, if I am inaccurate here.

You asked. I answered as honestly as I can.

[CONF iture]

Much of that data should be disclosed to the individual family if they wish.
They wish.

[bearfoil]

And it is not forthcoming. fwiw.

JD-EE

Many folks here and elsewhere, know (approximately) what happened. Absent the exact details, an upset and LOC. Stall, leading to ocean impact. The precise daisy chain is and will be, fascinating. I am not trying to be facetious, the answer has been posted. Keep looking, it has everything to do with Physics, Electrons, and Mother Nature. A remotely possible confluence of poor fortune, poor performance (relative), and expectations. On the day 447 died, 1,000 people died in automobile accidents, and two thousand of smoking related illness, in America alone. It always produces snooty reactions when framed this way, for those who die in the air (or water), are somehow special.

Why? because for some reason how people die is seductive to humankind. I am full of grief for each soul who passes, every one. What galls me, is not the actual fact, but the residue of less than noble motives responsible for more than one would expect in the way of "death by airborn conveyance".

For each mechanic who wants to eat lunch and doesn't secure his forklift bearing a partially installed engine, there is a deliberate attempt in the boardroom to mitigate what are considered 'allowable' loss of life in the name of shareholder and pension, not to mention golden parachute.

For nuts, bolts, and sliderule types, you should make more money. Be more careful. See to it the line raises prices to reflect what an amazing and exciting endeavour is flight.

Success breeds competition. Grand success can breed ruinous competition, then the quality and safety of your travel starts to look like your meal, a hastily thrown together mystery meat casserole. We all deserve better.


TD: Do you expect an industry altering surprise? I don't. The Airbus has millions of hours, and was flown by highly qualified men.

Some hitherto unknown quirk of alchemy? Perhaps "Unknown aspects of fuel performance in Icing"? An unbelievably remote taptap freeze up?

I know that you are an engineer, and I value and admire your approach.
I hope to learn some of it here. Both of us are inquisitive, one of us perhaps a bit more suspicious of Humans than the other. I've been in marketing, Politics, Research, and many other pursuits. No one has ever gone broke underestimating the gullibility of the masses. Me included.

Trust is fickle, and once lost, a very arduous trek 'back'.

(modified my post, is it better?)

[hetfield]

BTW,

watch this, from another thread, starting 03:00

&#x202a;Boeing 727 Prototype-"First Flights"-1963/64&#x202c;&rlm; - YouTube

[Turbine D]

Read your last post, noticed one sentence:

Many folks here know what happened.

Thought you left two words out: "Many folks think they know what happened."

In reality, few would bet their life, life savings, the ranch or their next paycheck on knowing for sure at the moment...

[Poit]

Hi PJ2,

Your reply to 3holelover was a very comprehensive and well written one. Both from a pilot-response point of view (which is common practice: power + pitch), and multiple systems and redundancies available for attitude indication in a large airliner (which was enlightening to me as well).

Your post very cleanly and succinctly draws the reader to the burning questions that are confusing most people with flying experience (myself included):

- Why the initial NU input; and
- Why the maintained NU input.

You were very diplomatic in not offering answers to those questions, and I don't think any of us can do until the final report is released.

Thank you sir!

[jcjeant]

Hi,

JD-EE
"what caused it to enter that stall condition?" Only two causes are possible
1 The pilots made error
2 A defect of the plane
This is debated from ages on this forum
So far .. after reading the BEA preliminary reports and the note (and taken not in account all the speculations and technical stuff posted on this forum) .. the answer (until proved false) is item 1
All between 1 and 2 is armchair stuff
Like it or not ... but that's the life...

[gums]

This accident/crash will be one that lives in the books for a long time - many lessons-learned. And the "cause" will not be a simple pilot error or airplane problem.

Without posting 1,000 words, I can not believe that a modern FBW system does not employ a "standby gains" feature that uses air data from 2 seconds ago when the air data system becomes "suspect" by HAL or the humans in the cockpit. Hell, you could even provide a switch/button to revert to "standby gains" if you, the human, thought something was awry.

"HAL, I think we just froze up the pitot tubes, and remember that incident a few months ago?"

"Yeah, Gums, let's use some generic air data quantities while we figure this out"., and "don't worry about overspeed warnings and such while we work the problem, Gums, we ain't gonna die in ten seconds if you just hold current power and attitude"


That is not what happened, folks.

I am not convinced that a feature of one of the "laws" commanded an AoA or pitch that was not commanded by the pilot. After that, well, the pilot could have made things worse.

I am not convinced that aircrew training emphasizes the "don't just do something, just sit there", take a second or two and sort things out. In my little jet, we had less than a second to "do something", but it was the nature of the mission and what the jet was designed to do. The big heavies don't/can't move at 20 or 30 degrees per second in roll or pitch, but mine did. Those heavies have fairly benign aero characteristics, and with full control inputs you can't come close to the rates and such I dealt with.

IMHO, human factors will play a large role in the ultimate findings. Some will be training deficiencies, and some will be related to conflicting "warnings" and having a crew trying to figure out what "protections" they had versus simply flying a decently-designed jet with a basic control law to hang their hat on.

[Poit]

JD-EE

This is what BEA is doing with a fuller deck of cards to play with. (I get giggles imagining one of the investigators reading this thread knowing things we don't and admiring the flights of fancy on all our parts.)

I see no legal definition conspiracy taking place. So far I see a remarkably open BEA providing enough data to the public for two serious purposes, to put down speculation and let the public know the level of data BEA is working with as reassurance they're on the job. We're taking this a whole lot further than BEA. And out of our discussions may come some valid criticisms of cockpit culture, training, system design, and hardware. (That's more or less my current sense of probability of serious criticisms. I'm biased, of course.)

Hats off to you too mate. As with P2J, you're applying some much-needed logic and sense to what is (largely) for me a very interesting and informative discussion, marred by questionable contributions of a few.

I agree that the BEA have provided as much as they can at this point. Imagine the litigation(s) that would ensue if they published something that caused 'red herring' conclusions in the public domain. They have been as generous with information as they can afford to be at such an early stage, and I'm sure as much as is necessary will appear in the final report.

I'm also curious as to what a BEA investigator would think if he/she was reading this. For 'impartiality' reasons, I'm not sure they could, or would be allowed to. I think there are some valid theories here (with info available), but some of the more extreme makes me cringe...not giggle!

[PJ2]

Poit;
You were very diplomatic in not offering answers to those questions, and I don't think any of us can do until the final report is released.
Thank you - I often wonder how such work is taken because there is so little response. I would not only never draw the conclusions regarding the crew, I can't because we don't have all the information.

Initially, I did posit the notion that the pitch up was a result of a response to the UAS memorized drill and checklist. Perhaps so, perhaps not, but that certainly wouldn't be "crew error" and could never be left to stand as such as a "single cause".

gums is right in stating "And the "cause" will not be a simple pilot error or airplane problem." There is no such thing as "pinpointing THE cause", and then being satisfied that one has "found out what happened". Such an outcome would be wholly incomplete and not true to the investigative process.

As I posted to Turbine D a few pages ago, there are indeed alternate plausible explanations to the pitch up, indeed I am aware of such explanations and cannot refute them. My post was more of an approach to the argument that a loss of attitude information "caused" the pitch-up which I doubt that very much for the reasons given. Each theory has to be explored, and whatever one can infer, logically, can be brought into the discussion with the understanding that it is merely a theory. Perhaps the data and cvr will resolve the matter, perhaps it won't. I think it will.

In any case, with comments done until then, I'm awaiting the next interim report.

[Poit]

No problem P2J, I too await the answer to the question. I recall you offering that theory (a 'pilot training/expectation' response), and as with other theories, it is quite plausible (if not concerning in the greater scheme of things).

As I said, the way you hypothetically approached the situation, (from the armchair, I acknowledge...I'm sitting in mine too),was methodical, logical, involved crew interaction about important initial actions, and crucial actions in the situation given.

As a frequent flyer (customer of airlines), I would expect a line-pilot, regardless of met conditions and given the situation, to apply the same. Wouldn't you?

I agree also that it can't be put purely down to either pilot, aircraft, or systemic failures. I was always taught that an accident was a serious in a chain, and as Air Force pilot trainees we were encouraged to break the chain created by other factors (ie be the human factor that didn't fail). Not always easy or possible.

Cheers

[henra]

henra, grity mentioned the aircraft's thrust. That's a stable system. So the real answer is probably between the two calculations you give. I'd suspect it is closer to the square of the delta velocity. (In fact I did a long ways back.)

In fact if you want to be exact, grity is right. The equilibrium of drag and thrust is only valid for one speed. So when the AC slows down in the climb, the 1g drag decreases. Therefore the thrust of the engines will add some energy to the equation.
However, this Delta of energy is negligable compared to the Deltas in energy state we are talking here. The effects of increased drag by maneuvering and changing bank angles will by far exceed the Excess thrust due to the speed decrease.

Between the two calculations I compared there is no doubt about which one is the physically correct one:
it is 1/2(m) v1^2 (Kinetic Energy before the climb) minus 1/2 (m) v2^2 (Kinetic Energy after the climb).

[JD-EE]

I think you guys might might not have seen this NASA toy before. The picture, A Flight of Helios (http://apod.nasa.gov/apod/ap110724.html), is rather nice and quite large. This propeller driven plane has made it to FL914, aka 30,000 meters on solar power only. Warning - it is a large picture.

(If it's too far off topic, John, please delete it.)

[JD-EE]

quoth bearfoil, "And it is not forthcoming. fwiw."

Rightly so.

The investigation is not over. Once it is over then there's time to prepare packets for the survivors with what is known about their particular victim or victims. I'm not sure I'd want to see pictures of a loved one after a couple years underneath the ocean and subsequent retrieval. There are levels of gruesome that bother me.

[JD-EE]

Turbine D said, "Thought you left two words out: "Many folks think they know what happened.""

In very broad terms I think we all know what happened. The plane took off from Brazil and the flight ended improperly slightly North of the Equator in the Atlantic Ocean.

Actually we know a good more detail than that. What we don't know for sure is what matters - what has to be done or what can be done to prevent this happening again?

[JD-EE]

jcjeant, I hope you know "the pilots made error" is not a good "cause".

Why did the pilot make the error? Can we determine this if that is the proximate cause. Is the real cause is faulty training and we stop at "the pilot make a booboo" the investigation served no purpose for the general public. And in that case I'd prefer the lower ticket prices had this investigation never taken place. If the data in BEA hands can lead to one or more aspects of training, manuals, instrument presentation, cockpit culture, or anything else that needs fixing, then fix 'em to the extent it's feasible.

Just don't stop at "the pilots made an error" or there was a "defect in the plane".

[JD-EE]

OK, I'll post a me2. PJ2, you have my complete respect here. You are one of the real adults in the room. (And I'm a Chatty Cathy....)

[3holelover]

PJ2,
Thanks for your well considered response... I agree with Poit.

I think there may be more than a few readers here who took me to be 'blaming' the crew for this.... Truth is that I've simply accepted the BEA's statement that there was not a problem with the aircraft (beyond the iced pitot probes), and I've started trying to imagine what causes may exist for the crew to misread their situation and provide incorrect responses. When I say the answer that best fits what we know so far is that the PF "screwed the pooch", I'm using an age old vernacular that I thought all who fly would understand... It doesn't necessarily imply that Ace McCool himself wouldn't have made the same incorrect assessment of the situation.

My original question was simply trying to find good reasons for the errors made. ...and I still think the answer may have had everything to do with what they saw and what they felt. ...and undoubtedly the sequence of same.

As an AME I'm well aware of the multiple contributing factors involved in any accident, and I know very well that blame can never be assigned to a single source. There are always other contributions along a chain of happenings. However, there is always the first line of an answer, such as: "Aircraft XXX fell out of the sky because the wing fell off." ...or, "The aircraft failed to stop on the runway because the wheels fell off." etc... Each and every case would have much more to the tale of course, with many important details, but the first line is not something that can be avoided.

In this case I've taken the BEA's releases at face value and have read the first line as saying, 'The pitot tubes iced, giving erroneous AS readings and the pilots failed to respond appropriately.' ....and now we need to find out why, yes?

In that, I can well imagine, given the situation they found themselves in, that many pilots might have made the same errors. I think in the seconds they had to deal with their multitude of puzzles and mixed messages, even Ace may have wound up in the drink.

[bearfoil]

3holelover

In reading your last, I am concerned. BEA have not concluded "There is no problem with the plane, save the iced pitots."

You repeat this in your second to last line.

I submit, with your position especially, that you may be adding to myth, to an incorrect interpretation, and to continued misunderstanding of the process.

You are heading in a direction opposite mine. Some may find that reassuring, I do not. It is better that the public know nothing, than to sheep the "consensus" of a thread with an anonymous population.

In an old, and odd sort of way, I support the mission of BEA. I take the release of the PR note as most destructive of an honored goal.

Agreement (assent) is a cultural artifact. It means nothing in the long term. It supports compromise, rather than the Truth. The best work is done by those who have passion first, and acceptance down the list. In this format, it is the adversary who will move you, not the ally.

In agreement alone, is second best.

[A33Zab]

Hi Takata:

Just found out why the NAV IAS DISCREAPANCY message might be suspressed.
(Not completely sure, because we don't know the exact ECAM software status but this one is dated 08/NOV/06, so could be valid at that date)

1// The NAV IAS DISCREAPANCY can be triggered by a ADR 1 or ADR 2 IAS FAULT FOR PRIM status (as detected by FCDC1 or 2).
ADR 3 status comes only into view when ADR 3 data switch is out of the normal position)
2// The NAV IAS DISCREAPANCY can be triggered by a FROZEN PITOT Status (as detected by FCDC1 or 2).

But both 1// or 2// conditions to trigger the NAV IAS DISCREAPANCY message can be suspressed by certain system conditions being TRUE.

a/ any Dual or Triple ADR Failures (NAV ADR x+y(+z) FAIL messages not mentioned)
b/ All ADRs INOP [Switched Off] (not mentioned)
c/ NAV ADR DISAGREE present (not before ca. 02:12:00)

d1/ ADR CAS 1 or CAS 2 or CAS 3 NCD(or INValid) for reference 1//: IAS Fault for Prim status

d2/ Any DUAL CAS NCD(or INV) for reference 2//: Frozen pitot status

With this information I need to rethink what I posted before, maybe you could find some justification in your point of view.


http://i474.photobucket.com/albums/rr101/Zab999/IAS_DISCR-1.jpg

[ChristiaanJ]

...NASA toy "Flight of Helios".....Sincere thanks for the pic and the link, JD.

OT, yes. But I think John will leave it in place.

[airtren]

henra,

I should clarify that my post #546 was only indicating an initial symbolic notation of the Kinetic energy as a function of speed, with the speeds, which are easy reference points to the BEA text, which mentions the two IAS values 275 and 211. That was a correct notation, and a correct equation. Further calculations based on that equation are correct, as long as as the expansion of the functions include the correct speeds.



dEk = Ek (275knots) - Ek(215knots) = dEp (2500ft)

Not wanting to nitpick, just for the sake of correctness, it has to be noted that the 275kts and 215kts were IAS.
For any kind of energy calculation you have to take TAS.



But what attracts my attention more in your post, is the TAS values.

I am not sure what considerations you've made in calculating, or getting the TAS. Can you elaborate?

One of the AF 447 BEA reports indicates a TAS of 461 knots at FL350, while yours is 495 knots.

Even further, and more importantly, you're indicating a calculated "delta h" based on the two TAS of 495 and 390, of 4200 ft, and you're reasoning that the larger "height" value (of 4200ft versus 2500ft, a difference of 1700ft) is explicable by the increased drag during the ascent/climb.


In this case that would be approx. 495kts and 390kts, repectively.

Edit:
This corresponds to ~4200ft but is still very well explicable by the increased drag of the maneuvers. So I don't contradict the statement that the kinetic energy figures are plausible.


You expend further on that in your reply to JD_EE.

JD_EE is pointing out an element that I interpret as being in line with my further explanation bellow. He is also up to something, further in the second 1/2 of his post, :D but without elaborating....:)



henra, grity mentioned the aircraft's thrust. That's a stable system. So the real answer is probably between the two calculations you give. I'd suspect it is closer to the square of the delta velocity. (In fact I did a long ways back.)

In fact if you want to be exact, grity is right. The equilibrium of drag and thrust is only valid for one speed. So when the AC slows down in the climb, the 1g drag decreases. Therefore the thrust of the engines will add some energy to the equation.
However, this Delta of energy is negligable compared to the Deltas in energy state we are talking here. The effects of increased drag by maneuvering and changing bank angles will by far exceed the Excess thrust due to the speed decrease.


It's right that the Thrust and Drag are valid for one speed.

But here is further:

Based on the BEA text, we know 275 knots (FL350), and 211 knots (FL375), were speeds that resulted from Real Time measurements (and/or calculations based on Real Time measurements).

Thus they implicitly include the Real Time AF 447 Thrust and Drag, in Real Time conditions, at FL350, FL375, and the climb/ascent in between. And so should be the TAS.

Also based on the BEA text, we know the delta height of 2500ft, which is also a Real Time measured element, and thus it includes the Thrust and Drag that were present in getting to that height.

Pointing out, or explaining that a calculated approx 4200 ft height's discrepancy of 1700ft is due to Drag, or Thrust, means including Drag or Thrust a second time in the equation. That does not seem to be correct. :=

So, I think there is a need for a different explanation....

....
The equation bellow, which is a next step from the one I've posted, is correct.

This is to say that the earlier posted warning that

v1^2 - v2^2 is not equal to (v1-v2)^2

was absolutely correct.


Between the two calculations I compared there is no doubt about which one is the physically correct one:
it is 1/2(m) v1^2 (Kinetic Energy before the climb) minus 1/2 (m) v2^2 (Kinetic Energy after the climb).

[ChristiaanJ]

A33Zab,
What are those >> shaped symbols?
Are they 'modern' OR gate symbols?
Question from an ancient, who sees these for the first time.

[bearfoil]

airtren

How are the altitudes and "AS" derived by BEA? Inertial? Certainly from the DFDR? How accurate is the "start" Alt.? With great respect, no possibility of gigo?

Perhaps germane is the 'ability' of BEA (or any retrospective) to suss solid data from an airframe that may not have supplied it to the only people who matter? If this is so, and ATF boffins can determine data that would have saved the day, perhaps we should wonder why? No offense intended.

Inherent in any device that can "unwind" a puzzle, is the implied chasm between "best practice" and "Failsafe"? In there also is the "acceptable" risk?

Internist: Knows everything, does nothing
Surgeon: Knows nothing, does everything
Pathologist: Knows everything, does everything, but too late.

[grity]

airtren, henra,
the question if the BEA speeds are CAS or TAS are not realy clear for me, up to now I tought CAS

I was not on the search for negligable faktors, just trying to re-calculate the energie for my self (fighting with non metric units as before....)

I think they flow with mach 0.82 at F350 and planed to climb to F375 (flightplan) and in the same moment wanted to reduce the speed to mach 0.80 (turbulence) so they start the climb without more trust....... and then start the UAS event...........



if v2=0 then

v1^2 - v2^2 is equal to (v1-v2)^2 ..... so "dont hang up" uses the second formula just for argumenting how high maximal you can climb before you stand still (V2=0) with given v1....

[takata]

Pointing that Thrust needs to be considered, or explaining that your calculated approx 4200 ft height's discrepancy of 1700ft is due to Drag, or Thrust, means including Drag or Thrust a second time in the equation.
That's not correct.
Nevertheless, henra seems correct to me also.
Beside speed, altitude is not the only parameter changing during the climb, the flight equilibrum is also changed (thrust/drag ratio).
If no additional power is applied for an altitude change, the aircraft needs more lift; alpha will be increased and airframe will produce more drag. A lesser factor is the loss of thrust at same RPM due to increased flight level.

Consequently, no matter if the calculation is based on IAS or TAS, energy state change is not only due to a single altitude parameter changing while your estimation is only factoring altitude on it.

[Linktrained]

From my age and name you can see that I probably lack any special knowledge of modern techniques or -ologies. However..

A Royal Flying Corps pilot was told " not to fly too high or too fast" and he would have seen the effects of flying too low or too slow on the airfield.
Most or many accidents were put down to " Pilot Error" (" No one will ever know...")

By page 31 of David Beaty's "The Human Cost of Aircraft Accidents" ( 1969) he had described three different Pitot/Static accidents - not always the " fault" of the aircraft. He goes on to look at a number of failings of the many humans who then were involved in making the safety of Air Transport even better. Humans are STILL relevant... ( Don't tell HAL.)

Some airlines only had Captains who never made mistakes, were called Sir, and from their Accident Reports, were all rated "Above Average".

Most of the many hundreds of crew members with whom I flew, I would guess, aspired to be just Average, and stay out of the Accident Reports. First names or nicknames were used. It was thought easier to say, "Watch it, Joe.." Rather than " Sir, you are about to hit the sea wall.."

In the crew room of one fleet, built by B., it was joked that Emergency Drills should be done quickly, much more so, than accurately and appropriate. Another fleet, made by a different B. was told that their new aircraft had been so designed that you should sit on you hands and count up to ten before you do anything.

In September 1947 C54 "Robert E. Lee" flew from Newfoundland to Brize Norton, fully automatically. Probably not to today's safety standards, I would guess.

[A33Zab]

What are those >> shaped symbols


Couldn't copy original logic schematic since it's input signals are coded.

In this schematic they stand indeed for OR gates.
Excuses, but didn't find any -OR gate symbol - in my office version.
Will do some edit to mention that.

[wallybird7]

What went wrong?
There is no group more concerned about what happened, or what went wrong with this accident, than the pilot community. They need to glean any lesson that can be learned to avoid it from happening again.
They can't wait for the completion of the up to 2 year period of the formal investigation. They have to continue flying the next day.
The one trigger to all of the following events is entry into a towering cumulo nimbus that reached up to 60,000 feet.
Trying to hand fly an aircraft in turbulent air at altitude for the first time is a difficult task. If not impossible.
The simple remedy until it is all fleshed out is simply avoid the potential trouble spot. And deviate well clear.

[DJ77]

Please wallybird7 do you really think we need another lecture about CBs ?

It may surprise you but be assured that just as every airman AF crews know that you don't venture into the big bad wolf's mouth.

[gums]

With all due respect, Wally, all of us, as pilots and SLF's, have flown thru bad weather. Sometimes we didn't have a choice due to the mission, and I feel most of us avoided obvious bad weather.

Over the past 50 years we learned a lot about weather effects that extend miles and miles from the obvious CB towering cumulus. We learned about mountain waves and CAT and rotor clouds. What a wonderful world it would be to have CAVU every day. Well, I personally like those fair weather cumulus, heh heh. Kinda adds "ambience" to the experience.

There is no doubt that "weather" will play some role in the tragedy. However, the biggest role will be freezing up the air data probes for a system that depends upon them for many functions and "nice to have" features of the jet.

It is interesting to note that several other jets flew thru the same general area and their pitot-static systems didn't go "tits up".

The BEA reports do not indicate severe flight conditions that we pilots would be concerned with. Instead, we have a loss of air data to a sophisticated system, and the subsequent warnings and change of "laws" seem to have played a large role in the pilot reactions.

In short, Wally, I ain't gonna blame flying near some storms over the ocean, or efforts by the crew to "ease the pain" going thru a line of them. In my experience, the storms over the Pacific were nothing compared to the ones over Kansas. I even re-fueled behind a KC-135 a few times in the middle of some of those suckers and it was nothing I would have attempted over Topeka in the summertime.

[JD-EE]

airtren, let's see if I can be more rigorous without getting into details. That is to say, I'll wave my hands a bit. Hopefully somebody with numbers will then step in.
What really needs to be accounted for is the energy imparted by the engines and the energy removed by drag. In that calculation you use the difference of squares rather than square of differences. Then you add in the energy from the continued thrust Et and subtract the energy lost in drag Ed. In level flight. At FL350 these two figures were roughly balanced. So somebody who knows the engine thrust at FL350 can figure a "static" value for Et and Ed. That allows a modified Ed for the duration of the climb to be estimated. Then we can really figure out of something was holding that plane down or not.

(I played on the back of an envelope and have a suspicion that the plane was indeed in a wind with a downward component of some sort. But it's such a swag I'm not going to publish it. I was pulling numbers out of the air and Wikipoodle.)

[jcjeant]

Hi,

Some interesting documentations (PDF French language!)

AF Simulation décrochage
SIMDecrochage.pdf (http://www.mediafire.com/?5836j9rwkk65s00)
A330 Domaine de vol
Domaine-de-vol-A330.pdf (http://www.mediafire.com/?n2xw5vmn41glxy4)

[wallybird7]

Please wallybird7 do you really think we need another lecture about CBs ?
It may surprise you but be assured that just as every airman AF crews know that you don't venture into the big bad wolf's mouth.


Apparently this crew didn't.

[henra]

One of the AF 447 BEA reports indicates a TAS of 461 knots at FL350, while yours is 495 knots.


I used the factor of 1,8 (1,798) for standard ISA conditions at 35kft.
Differences to that standard factor may result from temperature differences.
Please note: the BEA value was GS. The calculated one would be speed through the air corrected by density effect. Therefore also a headwind could be a possible explanation for the difference.


Even further, and more importantly, you're indicating a calculated "delta h" based on the two TAS of 495 and 390, of 4200 ft, and you're reasoning that the larger "height" value (of 4200ft versus 2500ft, a difference of 1700ft) is explicable by the increased drag during the ascent/climb.

Maybe I was unclear or maybe I#m misunderstanding where you are coming from.
What I was trying to point out is the fact that any additonal maneuvering (pulling g, thereby increasing induced drag and worse cl/cd of the wing or rolling, thereby increasing drag coefficient due to moving surfaces and induced drag due to resulting g load) will consume kinetic energy thereby reducing the amount which can be converted into altitude for a given speed.

On the other hand flying at 250kts IAS will require less thrust for 1g level flight than 275kts. So after slowing down and leveling off the engines have some excess thrust which would contribute positively to the energy available.

As takata has pointed out that is only partly true as below a certain speed the drag will rise again due to ending up in a less good cl/cd area (higher Alpha) of the wing polar. So at the end you can probably leave excess thrust largely out of the equation.


Based on the BEA text, we know 275 knots (FL350), and 211 knots (FL375), were speeds that resulted from Real Time measurements (and/or calculations based on Real Time measurements).

For an exact determination of TAS we would need the Air temperature as well.

Pointing out, or explaining that a calculated approx 4200 ft height's discrepancy of 1700ft is due to Drag, or Thrust, means including Drag or Thrust a second time in the equation. That does not seem to be correct. :=



What I was trying to explain is that I estimate that additional drag resulting from maneuvering (pulling g, rolling) could be sufficient to consume the 1700 ft worth of energy.
There are two effects impacting on the drag: even infinte wings used for calculating airfoil qualities have their best cl/cd usually at low AoA. Increasing AoA will deteriorate this ratio. On top of that increasing g will addiotionally increase the induced drag.
Unfortuantely without exact cl/cd curves for the A330 wing it will not be really possible to calculate the net energy loss due to the initial pull up.

[Dutch M]

Pardon me for jumping in. Initially, I also thought the PF
screwed up. Though following the discussion and matching the
background of physics to these items, I more or less changed
my mind. The general suggestion is: PF should have initiated
a pitch&power approach. It very well could be he did, with this
as a result.

I did write these articles the last 3-4 weeks, though didn't post,
given my lack of time to keep up with the current thread. Some
of the subjects have been touched in recent posts, though I
keep my writing included, to take care for a complete line of view.
I neither did have time to match all of the raised items with
the actual AF447 figures. Maybe somebody wants to do this.
My apologies about this.

In the, up to now 5 threads, some physics came along. Physics, which are
sometimes so far off, that conclusions drawn on that are totally off. As such I
do give some thoughts how to approach those items.


1. Usage of TAS to calculate Kinetic Energie exchange for height.
====================================

- Since Kinetic Energy is non linear in speed, it's not an option
to consider the change in TAS a suitable parameter for change in
Kinetic Energy. For a zero speed based start to calculate the speed
of a dropping item as function of it's height, that's ok.
Since the Kinetic Energy is the SQR of the speed, the Kinetic
Energy of different perpendicular axis are independent.

- For general exchange of speed into another direction or height
(Potential Energy), the actual inertial speed has to be used,
so at least the ground speed and not TAS. I would even say, groundspeed
corrected with the earths' rotational speed (roughly 1800 m/s). Due
to lack of time, I didn't have the time to think this through for
100%, though I do expect this to be relevant.

This can be understood from the following thought-experiments:
= Assume the windspeed suddenly becomes zero. Will the effective
Kinetic Energy of the airplane change ? Nop.
(The airplane will show reactions after the change, though that's because
the force-field does change).
= Assume with the airplain flies with constant speed, the earth rotation
is suddenly stopped (that would give a mess on the ground, though it's
only a thought experiment). Would the effective Kinetic Energy of
the airplane change ? Nop. When an airplane lifts off, the airplane
starts with a speed related to the ground plus a TAS to generate
sufficient lift to lift off.

- So the Kinetic Energy will be 0.5 * M * SQR (| TAS + WINDSPEED + Vrotation |).
Of course everything in 3D vector calculations. M is the airplane mass. The
bars "| |" represent the calculation of the length of a vector.

- To get an impression how much the effect is. The example assumes
for ease of calculation, all vectors have the same direction. In general,
this is not the real situation:

Kinetic Energy presumed to be "released" from an object bleeding of a 250 m/s TAS back to zero:
0.5 * M * 62500 = 31750 M

Kinetic Energy released from an object bleeding of (TAS) 250 + (Windspeed) 50 +
(V-earth-rotation) 1800 m/s to a TAS of zero (with the same wind/earth-rotational speed):
0.5 * M * 4410000 - 0.5 * M * 4202500 = 103750 * M

So when doing the Ekin calculations properly, around 3 times more Energy
becomes available for height gain. Note: Speeds only intended for example
purposes, these aren't the actual AF447 figures.

Usage of TAS to calculate the energy exchange gave a "suitable" fit
for the AF447 case. Why is the difference so big ? I'll get to that a
little further in this article.

Only vertical speed vs. high, the normal Energy constant formula can be used.


2. Effect FL38 turn on TAS and as such on Stall warning reactivation.
=======================================
Nobody mentioned the potential effect of the 180+ degree turn at FL38 on
the return of the stall warning. Such a turn would have a significant
effect on the experienced windspeed and as such on the TAS.
Once at FL38, the airplanes' Inertial Kinetic Energy would be
reasonable constant during the time it takes for the turn. The TAS
however changes a lot. Depending on the wind direction, up to
twice the windspeed.
Maybe somebody might want to match this aspect with the actual AF447 data.


3. The presumed HS stalled status on the way down.
=====================================
Once the airplane got a reasonable downward vertical speed component,
I don't think the AF447 HS is stalled at all (on the contrary, has super-lift),

Why: Typical aspect with a stall is: release of the boundary layer over
the airfoil AND a sudden increase of the speed vector component opposite
of the intended lift force. On the main wings, both components do influence
each other increase both values after initial upset, significantly.
A situation, with an AoA getting higher than the main wing can handle, starts
very fast.

Now to the HS: The intended "lift" for the A330 HS is downward. The speed vector
of the AF447 HS on it's path down to earth, is also downward. The pressure gradient
is actually pushing the air towards the airfoil. So no reason
at all for boundary separation. More the contrary: Because the downward speed vector
"pushes" the airflow on the airfoil, the tendency to boundary separation will be less.

Another aspect relevant in this, is: The HS airfoil does have to curved surfaces,
bottom side a lot, the upper side just little bit. So both sides of the HS generate
lift, where the downward lift force is significantly higher.

Now back to the AF447 HS on it's downward trajectory. The downward speed
is so high that the upper side of the HS airfoil will have (nearly) complete boundary
layer separation, so the upper airfoil surface is completely stalled. The net effect
is an even greater downward lift vector on the HS.

Or so to say: Because of the huge HS downward lift force, the normally nose heavy
airplane doesn't topple over to a nose down situation.

Because of the high downward HS lift, this airfoil is (together with the VS) perfectly
able to stabilize the aircraft on it's way down and prevent a spin or even a roll.

The above can also be argued from the opposite side. The BEA has reported
the airplane went down in a stable state. This can only be reached when a
configuration with airfoils with sufficient "lift" are present. Since the main wings
are definitely stalled, the stable factor must come from the HS/VS span.

Another reasoning from the other side: The A330 is layed out nose heavy
and with stalled main wings the residual main wing lift vector has moved
aft. Despite that, the aircraft didn't topple over it's nose down. So there MUST
be a force to compensate this nose down tendency. This can only be the
downward lift force of the HS.


4. The correlation between Stall (-warning) and AoA
=====================================
This item has been raised, including the statement, a stall (-warning)
is only a function of AoA. On first glance, this is true. However,
there are more aspects very important for this AF447 situation.

For a buzzer type C152+ stall warning device, the warning goes
of when the AoA approaches the max actual value for that
particular configuration of the aircraft. The buzzer "measures"
the actual critical value itself.

For the stall warning principle on the AF447, the AoA is measured
to calculate the Stall situation based on several assumed aerodynamic
values of the airplane and it's surroundings. As long as these assumptions
are valid, the stall warning is calculated properly. If these base
properties do change, the stall warning calculation fails. I also do
expect these stall warning calculations taking into account aspects
as temperature, actual air pressure, configuration and maybe also the actual speed,
simply because with decreasing air pressure, the stall AoA decreases.

Further in this article why this assumption is important for the AF447 situation.

Pure from the physics, I also do expect this stall warning calculation
to be non-linear, though this is not relevant for this article.

The implications of the above, is that, in case the aerodynamics is
different as expected, the airplane can be stalled, without the
stall warning being triggered.



5. Icing type, super cooled water vs huge "clouds" of ice-xtals.
=======================================
Given the pitot tubes are by far the hottest parts of the airplanes'
outside surface (ok, ok, the engines are hotter), the pitot tubes
did clog up completely and there is no reference at all about icing build
up at the outside of the airplane, it's pretty likely the pitots did
absorb a lot of ice-xtals and not super cooled water freezing up
in the pitots. If the AF447 would have encountered super cooled
water, there would have been a lot of ice accumulated on the airframe.
So much, the windshield would have been covered and probably the aerodynamic
properties of the airplane would have been effected significantly. I
did not see any evidence for this.

Another reason to assume, AF447 went into a cloud of ice-xtals, is
the simpel fact that the air temperature at FL350 is around -55 C and
the lowest possible temperature of super cooled water is around -40 C.

Another reason to assume this is an ice-xtals case, is the mention of the huge
amount of noise in the cockpit. A serious indication the pointy end
got bombarded by ice-xtals.

So in summary the AF447 went into a huge and pretty dense cloud of ice-xtals.



6. Effect of ice-xtal on wing stall.
====================================
The first approximation of ice-xtal polluted air, would be to consider
this type of air as "thick" air. And thicker air gives more lift, so
an increase of lift.

However, there is, pure from the physics, probably another effect. Having
a rough airfoil surface, the boundary layer gets disturbed and lets go
much easier with reduced lift as a consequence.

In the AF447 situation, there is not reason to assume, the wings did get
rough. However, the air is polluted with a huge amount of tiny but solid
and dense particles. So much, that from a pure physics side of the matter,
the boundary layer gets disturbed. And a disturbed boundary layer loosens
up. Simply resulting in slightly reduced lift. A wild guess would be
some 5% maybe 10% maybe even 20% reduction in lift.

Why did AF447 not drop out of the air because of this ?
For these speeds, another aspect might become relevant: The floating
of the wings over the polluted air. However the float based
lifting force is significantly lower then the Airfoil shape based Lift.
And not only significantly lower lifting force, though also creating
significantly more drag, also because of the higher angle of incident
required to get that lifting force. Let me call this aspect a "float-stall".



Some more thought-work in progress about:
- THS run away as result of main wing stall after minimal disturbance.
- Double control loop with run away inside loop.

Just let me know if you guys are interested in this.

And yes, every now and then, physics shows unexpected
behavior, so strange, it's difficult to belief......

Again, my apologies for the rough edges in this writing, I
simply do not have the time to polish this up.

[JD-EE]

wallybird7 said, "Apparently this crew didn't."

That is an assertion not in evidence. How do you know the storm showed on their radar? Was their radar working? Was it employed properly?

By the time the problem appeared on their radar any escape from the storm would have required extreme deviations from their flight plan with no communications to DAKAR.

They did note it at that time and made a deviation towards an area that appeared less risky than plowing on straight ahead.

Now, one might argue that they should have called Atlantico about this. But apparently this happens so often the pilots simply noted the fact and plowed onwards. I wonder what would have happened had they tried to check in at the follow-on control site after DAKAR since their flight plan was not properly forwarded.

But the pesky detail stands - moving aside from the storm at the time they saw it would have required some serious course deviations. At the time they hit it the storm was a very wide solid band.

[jcjeant]

Hi,

Was their radar working? Was it employed properly?Again we return to the basic questions and answers ..
Radar working .. plane defect ?
Employed properly .. crew error ?
Again .. nothing between ...

[bubbers44]

The acars message said the pitot system failed causing AP and AT to disengage probably because of their recurring icing problem. Any speculation about weather other than icing taking the plane down needs to be proven. So far there is no evidence of that being the problem since none of the other flights with normal deviations had a problem.

Those who insist it was turbulence and flying into a thunderstorm that caused the accident have absolutely no proof and are speculating. We know BEA knows exactly why they crashed by now. When they write the report we will know too. Be patient.

[Linktrained]

When sitting my F/Nav. examination, one of the questions was " You are the Chief Navigator of a Trans Atlantic Airline. What radio equipment would you require and why?"
I specified pretty well everything...
I asked another candidate what he had replied. He said that he had written " I have been in this position myself. I would require 2 ADFs. Two for reliabilty. With them I could get time checks for Astro. I have flown across the Atlantic 90 times with just this equipment and am quite satisfied with it." ( He had held this position with a South American airline. This would have been pre Weather radar being around.)

It might be helpful to look at what had happened to some of the other airlines' experiences with loss of airspeed. NWA, near Tokyo were some 25 miles from a Cb which was off to one side and went into some cirrus. It was daylight. I think that they lost their Pitot etc on two occasions in quick succession, both recovered in a few minutes. TAM was over the Caribbean, at night. Again the ASI came back after a few minutes. Both of the flights were prior to AF. Jetstars episode came after AF.

More details must be available of these (and others ?) from places other than my armchair.

What went right ? ( for them)

[Machinbird]

Dutch M
So when doing the Ekin calculations properly, around 3 times more Energy
becomes available for height gain. Note: Speeds only intended for example
purposes, these aren't the actual AF447 figures.Hi,
I don't really want to discourage an ambitious attack on the AF447 energy question, but let me add a few additional questions to your approach for an answer.

Have you added in the Earth's velocity vector around the Sun? How about the velocity of the solar system around the Milky Way galaxy? The answer should be that it is not necessary, these are negligible factors. For the same reasons, the rotation of the earth does not need to be included (unless you are flying ballistic like an ICBM). It exerts a force on the aircraft all right. We call it Coriolis force, but that too is negligible for our purposes.

There is no absolute inertial frame of reference then, is there? The height gain only reflects the change in position relative to the Earth's center of mass.

Will an aircraft flying 100 knots into a 100 knot head wind be able to convert some of that velocity into altitude gain? Of course it can. (Assuming it can fly slower than 100 knots)

[Machinbird]

Dutch M
The implications of the above, is that, in case the aerodynamics is
different as expected, the airplane can be stalled, without the
stall warning being triggered.HN39 has done an energy matching simulation (segment by segment) combined with aerodynamic assumptions. (Believe it was in the prior Tech thread.) His conclusion was that the final climb from FL375 to FL 380 was ballistic, i.e. the aircraft started upward on the last dregs of its lift and decelerated below actual level flight stall speed in the climb. This would allow the aircraft to fly below actual level flight stall speed and continue trimming nose up because the AOA had not yet become high enough to shut down the automatic pitch trimming. When gravity caught up with the aircraft and it began to fall, it then went rapidly well past the stall AOA and shut down the automatic pitch trim at 13 degrees ANU.

HN39 is very good with this type of thing, and we Physics duffers should respect his knowledge.

HN39, if I have gilded the Lilly too badly please correct me.:}

[CONF iture]

Hence, from this point, ALT2 without valid airspeed/Mach and SPEED LIMIT FLAG on PFD make it quite certain that Low and High Speed Stabilities were NOT available.
Do we read a different version of the first interim report ?
Note: the alternate 2 control law is a load factor law for pitch and a direct law for roll. Only the load factor protection remains available. In certain cases, the high and low speed stabilities may also be lost.
But what's the point after all, still have to work with ACARS messages + BEA note when actually all FDR data have been retrieved ...

[grity]

Dutch M The A330 is layed out nose heavy
and with stalled main wings the residual main wing lift vector has moved
aft. up to AoA 45 deg the move is very low,
even with AoA 60 deg it has moved not to much aft.....

look at the curve of the pitching moment (Cm) against angle of incidence posted by machinbird

http://www.pprune.org/tech-log/395105-af-447-search-resume-25.html#post5569978

[Machinbird]

Hi Grity,
That was posted well over a year ago, and is mostly a regurgitation of Davies excellent book. That pitching moment curve Davies provided was no doubt derived from a T-tailed aircraft and had a "sticking spot" that kept the aircraft from pitching back down after a deep stall. Probably the more recent pitching moment curves from the FAA generic airliner stall study are more appropriate to AF447.

[grity]

hi Machinbird, as time goes by......exist a link? for a Cm and AoA up to high deg (90)

[Dutch M]

>>Have you added in the Earth's velocity vector around the Sun? How about the velocity of the solar system around the Milky Way galaxy?

No, I didn't add this, though I did consider and is the reason I did add the phrase "Due to lack of time, I didn't have the time to think this through for 100%, though I do expect this to be relevant."

And indeed at first glance those aspects do have to be taken into account, though I -think- this is not relevant because the airplane is not acting in the sun's gravitational field. The earth is, but the airplane isn't (because of its low mass).

[Dutch M]

>>up to AoA 45 deg the move is very low, even with AoA 60 deg it has moved not to much aft.....

>>look at the curve of the pitching moment (Cm) against angle of incidence posted by machinbird

Yes with a higher AoA it'll become less, though still the same effect.

And on this plane the tail is not in the main wing shadow/wash.

[Dutch M]

>>HN39 has done an energy matching simulation (segment by segment) combined with aerodynamic assumptions. (Believe it was in the prior Tech thread.) His conclusion was that the final climb from FL375 to FL 380 was ballistic, i.e. the aircraft started upward on the last dregs of its lift and decelerated below actual level flight stall speed in the climb. This would allow the aircraft to fly below actual level flight stall speed and continue trimming nose up because the AOA had not yet become high enough to shut down the automatic pitch trimming. When gravity caught up with the aircraft and it began to fall, it then went rapidly well past the stall AOA and shut down the automatic pitch trim at 13 degrees ANU.

>>HN39 is very good with this type of thing, and we Physics duffers should respect his knowledge.

>>HN39, if I have gilded the Lilly too badly please correct me.http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/badteeth.gif

Yes, I've read that and as explained, those calculations is missing something. As such I started my article. Only for vertical movements, the trade-off in energy can be applied without further side conditions. When changing a horizontal speed into height, other aspects start to act up. If you want more explanation, let me know. I'm aware it's written down pretty condensed.

Maybe I should have mentioned before: I'm not a pilot, though do have a degree in Applied Physics (which includes Control systems behavior at the University I went - some years ago- ).

And: My description also suggests why there are around 10 reported similar upsets. Unexplained upsets without any plausible technical cause. And no, no conspiracies .....

[cwatters]

Dutch M..

Now to the HS: The intended "lift" for the A330 HS is downward. The speed vector of the AF447 HS on it's path down to earth, is also downward. The pressure gradient is actually pushing the air towards the airfoil. So no reason
at all for boundary separation. More the contrary: Because the downward speed vector "pushes" the airflow on the airfoil, the tendency to boundary separation will be less.

Another aspect relevant in this, is: The HS airfoil does have to curved surfaces,
bottom side a lot, the upper side just little bit. So both sides of the HS generate
lift, where the downward lift force is significantly higher.

Now back to the AF447 HS on it's downward trajectory. The downward speed
is so high that the upper side of the HS airfoil will have (nearly) complete boundary layer separation, so the upper airfoil surface is completely stalled. The net effect is an even greater downward lift vector on the HS.

That sounds very unlikely to me. You are suggesting that the HS is producing lift in the downward (negative) direction despite being at a severe POSITIVE angle of attack.

Imagine your explanation applied to a wing.. You're suggesting that a wing flown at a severe negative angle of attack (so severe that the lower surface is stalled) can still produce positive lift. I'm aware most cambered sections have a zero lift angle of attack that is slightly negative but your suggestion goes way beyond that.

[dinbangkok]

communiqu 25 juillet 2011 (http://www.bea.aero/fr/enquetes/vol.af.447/com25juillet2011.fr.php)

Press release only in French (at the time of writing)... the third report will be published this Friday (29th July), with press conference at 14.30 local time.

"Ce rapport présente les circonstances exactes de l'accident avec des premiers points d'analyse et de nouveaux faits établis à partir de l'exploitation des données des enregistreurs de vol."

The report will present new information established from the flight recorders...

[sensor_validation]

@Dutch M

1. Usage of TAS to calculate Kinetic Energie exchange for height.
====================================I politely suggest you go a read the Wikipedia article on Kinetic Energy. It is correct to use the airmass as reference and airspeed to calculate the KE relative to the axes (its not an absolute quantity). Newton's 2nd law is all about momentum, and momentum is linear in velocity (for constant mass). The equation for Kinetic Energy comes from integrating the momentum from one velocity to another. You do not have to take in account the KE of the system relative to the earth, sun, milkway etc - just use the same axes set before and after. So IMHO it is correct to just use 1/2m(v2^2 - v1^2) = mgh, you do not need intertial equivalents for v. 1/2m(v1-v2)^2 is wrong - unless v1 or v2 are zero!

[wes_wall]

the third report will be published this Friday (29th July), with press conference at 14.30 local time.



Better get ready to begin Thread nbr 6. This board is about to get real busy.

[Hyperveloce]

Hello there
Had the low speed protection been available, would the A/C have been able to zoom climb (or later stall) like it did ?

[takata]

Hi wes wall,
Better get ready to begin Thread nbr 6. This board is about to get real busy.
Certainly. And, as it's another interim report, maybe Threads 7, 8 ,9... will follow!

This communiqué means something like this:
This report will present the exact circumstances of the accident, the first analysis pointed, and the new facts established from the flight recorder data's processing.

[takata]

Hi Hyperveloce,
Had the low speed protection been available, would the A/C have been able to zoom climb (or later stall) like it did ?
It's hard to tell as it could be overriden by the pilot, but with VSw displayed, Stall alarms workings... certainly.
Check it by yourself:

http://takata1940.free.fr/lowspeed.jpg
*ALTERNATE LAW 2:
- Low speed stability is lost with double ADR fault.
- High speed stability is lost with triple ADR fault.

[HazelNuts39]

I'm not a pilot, though do have a degree in Applied PhysicsAs a student I piloted gliders. These routinely fly tight circles to stay in thermals. In a strong wind there is no airspeed loss turning downwind, nor gain turning upwind. I've never quite figured that out, may be as a physicist you can.

[Hyperveloce]

Hi Hyperveloce,

It's hard to tell as it could be overriden by the pilot, but with VSw displayed, Stall alarms workings... certainly.
Check it by yourself:

http://takata1940.free.fr/lowspeed.jpg
*ALTERNATE LAW 2:
- Low speed stability is lost with double ADR fault.
- High speed stability is lost with triple ADR fault.


Hi Takata. Ok, the gentle ND introduced by the low speed prot. can be overriden by the PF (and maybe the PF persistant NU inputs were to counteract the low speed prot. ND orders, but he did so much more than that). But if we consider the past UAS incidents analyzed by the BEA, do we see a single occurrence of a low/high speed prot. activation when the ALT2 was triggered by a NAV disagreement ? In a few past cases, a descent (never more than 5000 ft) was decided when the stall warnings sounded but it was a PF action. Can we assume that these low and high prot. were not available in all these UAS incidents and in the AF 447 case ?

[takata]

Hi Confiture,
Do we read a different version of the first interim report ?

Note: the alternate 2 control law is a load factor law for pitch and a direct law for roll. Only the load factor protection remains available. In certain cases, the high and low speed stabilities may also be lost.
But what's the point after all, still have to work with ACARS messages + BEA note when actually all FDR data have been retrieved ...
First, yes, I guess that we are reading the same report, but I'm trying to include every available informations from it, not only a single quote about the general case above that you underlined from it.

Second, the point is mostly to understand what we already have, before even going further with new data when they will be available (soon).

So, my initial point was to link those ACARS with real cockpit events:

1. Event started at 0210:05 with AP/FD and A/THR faults;
2. Event is due to 2 or 3 PITOT-PROBEs (total pressure) faults affecting some of their respective ADR outputs (barometric altitude, speed, Mach, angle-of-attack, temperature and overspeed warnings);
3. Those PITOT-PROBE faults caused all the following 0210 ACARS to be reported;
4. ALTERNATE LAW 2 was consolidated after monitoring, it was not transient;
5. 2 or 3 ADRs were rejected by FCPCs and FMGCs;
6. There was no "ADR DISAGREE" triggered during the 0210 sequence;

Hence, it may be deduced that it was due to a "triple ADR" fault:
=> ADR 1 + 2 / ADR 1 + 3/ ADR 2 + 3 (ECAM)
=> ADR 1 + 2 + 3 (not displayed by ECAM)
Consequently, Low and High Speed protections were lost while "SPD LIM" was flagged on both PFDs without VSw and VMax displayed.

- ADR 1 & 3 were coherent and valid again before 0211:06.
- Another triple ADR fault sequence started "after 0211:40";
- All speeds became invalid again;
=> It may be assumed that aircraft's airspeeds went below 30 kt, they would not be displayed anymore on both PFDs between 0211:40+ and 0212:19+
=> It may be assumed that "ADR DISAGREE" was triggered after this second triple fault was cleared.

[CONF iture]

In a strong wind there is no airspeed loss turning downwind, nor gain turning upwind. I've never quite figured that out, may be as a physicist you can.
Ground speed is affected, but not airspeed.
Once airborne, the glider is in the air mass that is moving at the speed of the wind, but for the glider itself regarding that air mass, there is no notion of tail or head wind.

[takata]

Ok, the gentle ND introduced by the low speed prot. can be overriden by the PF (and maybe the PF persistant NU inputs were to counteract the low speed prot. ND orders, but he did so much more than that).
See my post above. Low speed Stability, VSw, (and associated speed stall warnings) would only be available with two ADRs being declared valid, which might not have been possible before 0211:40+. Moreover, if it has been available before or after this point, it would have triggered "DIRECT LAW", whatever imputs made by the PF in order to counter those active ND protection imputs. Quite frankly, there is no trace of "Direct Law" and this never happened.


But if we consider the past UAS incidents analyzed by the BEA, do we see a single occurrence of a low/high speed prot. activation when the ALT2 was triggered by a NAV disagreement ? In a few past cases, a descent (never more than 5000 ft) was decided when the stall warnings sounded but it was a PF action. Can we assume that these low and high prot. were not available in all these UAS incidents and in the AF 447 case ?
No (first question). Yes (second one). All events involved 2 or 3 ADRs faults, this ruling out "Low Speed Protection" (other have been transient, hence, the system would revert to NORMAL LAW and this protection doesn't apply). Moreover, not a single aircraft ever made a single excursion out of its flight envelope.

[Lonewolf_50]

After reading post #661 ...

Hence, it may be deduced that it was due to a "triple ADR" fault:
=> ADR 1 + 2 / ADR 1 + 3/ ADR 2 + 3 (ECAM)
=> ADR 1 + 2 + 3 (not displayed by ECAM)
Consequently, Low and High Speed protections were lost while "SPD LIM" was flagged on both PFDs without VSw and VMax displayed.
Following so far, these protections are features of Normal Law.

Caveat: the following informed by sources that are between 5 and 10 years old.

When the pilots noted "Alternate Law," speed stability functions should have been in play if they were in Alt 1, but not Alt 2.

The system needs two valid ADR for stall warning and low speed stability.

I look at the FMA, and try to figure out if alert to "Alternate Law" is in one of the five fields above the attitude display, or on the ECAMS page. I cannot. (Don't have anything that tells me.)

Stability function can make inputs but can be overridden by the pilot's inputs.

This makes me wonder: did the crew know if their state was Alt 1 or Alt 2? (There may be more on CVR that will clear this up from next report, but there may not. Likely their work load was up, see below, and as such precluded any discussion as to which Alt mode was in play).

If PF didn't recognize alt 2 versus alt 1, would that have made a difference in how PF made and monitored nose inputs? My guess is no, but it's a guess.
(Question based on not having flown A330 ...)
- ADR 1 & 3 were coherent and valid again before 0211:06.
This leads to the question: were the pilots aware of this?

Perhaps the next reprt, and CVR analysis, release will shed light on that question. Perhaps task load precluded such a realization.
- Another triple ADR fault sequence started "after 0211:40";
- All speeds became invalid again;
From June 2005 revision of the Flight Crew Training Manual (8.110.3)

"... if all three ADRs provide consistent and erroneous data, the PRIMs and FEs will reject the “good” outlier ADR and will continue to operate normally using the two consistent but faulty ADRs."

Interestingly, in another section of the manual (2.60.11)
DIRECT LAW - In most cases of triple failure, e.g. triple ADR failure, direct law is triggered. Autopilot and auto-trim are not available.

One hopes that the various cases are handled in the simulator training sessions.

I also note that around pages 2.30.5 through 2.30.8 some ECAMS crew coordination is disucssed.

The process by which a crew clears ECAMS alerts is organized and formalized, but I see a source of possible scan disruption for the PF in this process, based on standard procedures for clearing ECAMS alerts.

[ChristiaanJ]

HN39 and CONFiture,
Your aircraft is not purely a feather blowing in the wind, it has a certain amount of inertia. Usually more of an issue during windshear, rather than while turning from downwind onto finals....
I would suggest the subject is mostly O/T here, and could maybe do with a separate thread on TechLog to kick the relevant notions around?

[CONF iture]

=> ADR 1 + 2 / ADR 1 + 3/ ADR 2 + 3 (ECAM)

Should not we have expected a relevant ACARS message ?
If 2 ADRs self auto detect at fault, should not we get SPD and ALT flags accordingly ?

[Squawk_ident]

The BEA will publish a new report next Friday 29th of July in the afternoon.

[airtren]

henra, grity, jd_ee,

Thanks for the additional comments on your previous posts.

I am looking forward for the next BEA report, and see how more it will contribute to the theoretical side of the accident understanding and interpretations.

Dutch M,

....Initially, I also thought the PF
screwed up. Though following the discussion .... I more or less changed
my mind.

Interestingly, I am among those that went through the same reaction, from an initial, simplistic, trivial "pilots fault" to understanding better and better the complexity of a rare intersection and confluence of multiple causes, that have a much wider span, and involve so many more players. Consequently, I believe, the AF 447 is one of those cases - the allocated resources were a big help as well - which will contribute to improving multiple aspects of the safety of commercial air transport.

post #636
1. Usage of TAS to calculate Kinetic Energie exchange for height.
====================================
...
Since the Kinetic Energy is the SQR of the speed, the Kinetic
Energy of different perpendicular axis are independent.
I think the spacial 3D/3axle character of the Kinetic Energy requires a consideration in its conversion to Potential Energy, regardless of it being linear or non-linear in terms of a mathematical function. However - if I understand correctly your sentence - I could not consider each of the 3 axle components "independent" of each other, by virtue of them all depending on the same spacial element, of which they are a component of.

post #636
- For general exchange of speed into another direction or height
(Potential Energy), the actual inertial speed has to be used,
so at least the ground speed and not TAS. I would even say, groundspeed
corrected with the earths' rotational speed (roughly 1800 m/s). This can be understood from the following thought-experiments:
= Assume the windspeed suddenly becomes zero. Will the effective
Kinetic Energy of the airplane change ? Nop.
(The airplane will show reactions after the change, though that's because
the force-field does change).
I have struggled with the use of airspeeds, including TAS, for the Kinetic to Potential Energy conversion/conservation, and I came to the same conclusion that the speed relative to the ground is the one that is relevant. Two elements are relevant, IMO, in this very order: (i)the height is relative to the ground, and therefore, that's the reference system, and (ii) air can transition from adding, diminishing, or being a null factor in the A/C speed relative to the ground, and thus Kinetic Energy, which is conserved from one (air) transition to the next, and relative to the ground.

I would not go that far though, as to using the ground rotational speed.

Post #636
... 4. The correlation between Stall (-warning) and AoA
=====================================
This item has been raised, including the statement, a stall (-warning)
is only a function of AoA. On first glance, this is true. However,
there are more aspects very important for this AF447 situation.

....the airplane can be stalled, without the
stall warning being triggered.
Based on the info that we have so far - this may change, once we have the next BEA report, and more info about the state of awareness in the cockpit - the Stall Warning or the lack of it is, IMO, a very, very important contributor to the accident. It was the lack of a Stall Warning while in the middle of the "stall" and the presence of a Stall Warning, when the A/C was close to "exit" from the "stall"..

Post #636
5. Icing type, super cooled water vs huge "clouds" of ice-xtals.
=======================================
...it's pretty likely the pitots did
absorb a lot of ice-xtals and not super cooled water freezing up
in the pitots.
One or another, is ultimately less relevant as the fact, that in adverse weather condition, all fail the same way, reducing this part of the system's "redundancy" to zero. This is an industry wide element, not only Airbus. The redundancy built in may work for individual electrical or mechanical failure, but such events are arguably less frequent than adverse weather conditions, and thus a weak point in passenger A/C design industry wide.

Post #636
6. Effect of ice-xtal on wing stall.
====================================
The first approximation of ice-xtal polluted air, would be to consider
this type of air as "thick" air. And thicker air gives more lift, so
an increase of lift.
Interesting....

I appreciate your post :D

[rudderrudderrat]

Hi airtren,

I have struggled with the use of airspeeds, including TAS, for the Kinetic to Potential Energy conversion/conservation, and I came to the same conclusion that the speed relative to the ground is the one that is relevant.
Simply use the air mass as your frame of reference. It may be moving horizontally over the earth's surface, but the conservation of KE + PE still holds.
IAS is just a measure of dynamic air pressure, it must be converted to TAS.

[Hyperveloce]

Thank you Takata for your patient answers. A last question: after the apogee at FL 380 of the quasi-ballistic trajectory, the AoA rapidly exceeded 30°, and the abnormal attitude law could have been triggered on this criteria (AoA>30°), but it has been said that it was inhibited since the airspeeds were invalid (below 60 kts) at that time (which is strange since IAS<60 kts is also an abnormal attitude criteria), and this also inhibited the stall warnings. But when the airspeeds became valid again, and when the stall warnings were allowed to sound again (after the ND inputs and thrust reduction), shouldn't the abnormal attitude protection law have triggered ? (since the AoA always remained above 35° according to the BEA)

[Neptunus Rex]

There have been many well thought-out and well explained hypotheses in this amazing thread. However, I still think that the basic problem was one that could have been solved by Power and Attitude.

Decades ago I flew an aircraft that had a beaut, coloured Standby Horizon, powered by a 28v DC battery, which was in turn kept charged by the aircraft's main electrical system. In the event of a Total Electrics Failure, the aforesaid 28v battery would provide power for a guaranteed 30 minutes. It was completely independent of any other power source, and would get you out of trouble when all else had failed.

Why can't we have such a simple and effective solution today?

[KBPsen]

effective solutionTo what problem?

[Zorin_75]

Why can't we have such a simple and effective solution today?
More effective than what?
There's no indication AI was ever lost...

[wallybird7]

JD-EE

wallybird7 said, "Apparently this crew didn't."

That is an assertion not in evidence. How do you know the storm showed on their radar? Was their radar working? Was it employed properly?

The weather forecast showed a line of thunderstorms about 100 miles wide over the equator. See AF447 Meteorological Analysis.

By the time the problem appeared on their radar any escape from the storm would have required extreme deviations from their flight plan with no communications to DAKAR.

They did note it at that time and made a deviation towards an area that appeared less risky than plowing on straight ahead.

Now, one might argue that they should have called Atlantico about this. But apparently this happens so often the pilots simply noted the fact and plowed onwards. I wonder what would have happened had they tried to check in at the follow-on control site after DAKAR since their flight plan was not properly forwarded.

Deviations happen all the time and you don't need clearance, just announce it on Guard Channel.

But the pesky detail stands - moving aside from the storm at the time they saw it would have required some serious course deviations. At the time they hit it the storm was a very wide solid band.

Agree. They should have deviated sooner. They knew the turbulence was coming.
Jcjeant
Hi,
Quote:
Was their radar working? Was it employed properly?

Again we return to the basic questions and answers ..
Radar working .. plane defect ?
Employed properly .. crew error ?
Again .. nothing between ...

Except a large build-up. And then all hell broke loose.

Bubbers44
The acars message said the pitot system failed causing AP and AT to disengage probably because of their recurring icing problem.
"Any speculation about weather other than icing taking the plane down needs to be proven."

Proven? How? Do you want a precise measurement of potential up and down drafts? What caused the ice build-ups? If not strong up and down drafts. Does turbulence exist in towering cumulous? Hell yes. Would it affect someone trying to hand-fly the plane?

So far there is no evidence of that being the problem since none of the other flights with normal deviations had a problem.

Just because the others skated through, is not "proof" that this one didn't get caught.

Those who insist it was turbulence and flying into a thunderstorm that caused the accident have absolutely no proof and are speculating. We know BEA knows exactly why they crashed by now. When they write the report we will know too. Be patient.

All of it is mere speculation. All the BEA has to come up with is "Probable" cause. Not "Exact" cause.

[Dutch M]

@cwatters (http://www.pprune.org/members/43381-cwatters)
That sounds very unlikely to me. You are suggesting that the HS is producing lift in the downward (negative) direction despite being at a severe POSITIVE angle of attack.

Imagine your explanation applied to a wing.. You're suggesting that a wing flown at a severe negative angle of attack (so severe that the lower surface is stalled) can still produce positive lift. I'm aware most cambered sections have a zero lift angle of attack that is slightly negative but your suggestion goes way beyond that. Yes, indeed, and it does look very strange.

Though, don't forget, in the main wing situation, the lift is destroyed because the airflow over the wing is not able to "carry" the weight of the airplane any longer and the boundary layer lets go.

In the HS situation, the weight is zero, because the direction of movement is already downwards.

And yes, in some situations the physics does look bizarre.

[Dutch M]

@sensor_validation (http://www.pprune.org/members/305146-sensor_validation)

Quote:
1. Usage of TAS to calculate Kinetic Energie exchange for height.
====================================
I politely suggest you go a read the Wikipedia article on Kinetic Energy. It is correct to use the airmass as reference and airspeed to calculate the KE relative to the axes (its not an absolute quantity). Newton's 2nd law is all about momentum, and momentum is linear in velocity (for constant mass). The equation for Kinetic Energy comes from integrating the momentum from one velocity to another. You do not have to take in account the KE of the system relative to the earth, sun, milkway etc - just use the same axes set before and after. So IMHO it is correct to just use 1/2m(v2^2 - v1^2) = mgh, you do not need intertial equivalents for v. 1/2m(v1-v2)^2 is wrong - unless v1 or v2 are zero! Yeah, suppose the windspeed goes from 100 knots back to zero, does this change the Ekin of the airplane ? If not, then you will need to take the groundspeed as speed reference.

The energy exchange Ekin vs Epot, is in general only valid for speeds in the direction of the change of Epot (ie Height) and not when trading speed between perpendicular axis.

[henra]

@sensor_validation (http://www.pprune.org/members/305146-sensor_validation)
Yeah, suppose the windspeed goes from 100 knots back to zero, does this change the Ekin of the airplane ? If not, then you will need to take the groundspeed as speed reference.


Dutch_M, you need to be aware that you have to determine the kinetic energy always with regard to the relvant reference system.
For an aircraft that is the air surrounding it.

To make it easier to understand let's take an example:

You have a wind speed of 200kts. Your aircraft is travelling at 250kts.
Minimum speed of your AC is 150kts.
How much speed can you trade for altitude now?

Correct ! You can trade 100kts.
You will be flying backwards then with regard to mother earth, but aerodynamically who cares ? You will still be flying.

If the relevant reference system changes its state beyond what the AC can bear, well then: bad luck. but you would have the same problem when you are flying at 100kts and suddenly a tailwind of 100kts hits you. Won't make a difference except for the horizontal component during impact with mother earth..

[Dutch M]

@henra (http://www.pprune.org/members/327762-henra)




Dutch_M, you need to be awrae that you have to determine the kinetic energy always with regard to the relvant reference system.
For an aircraft that is the air surrounding it.

To make it easier to understand let's take an example:

You have a wind speed of 200kts. Your aircraft is travelling at 250kts.
Minimum speed of your AC is 150kts.
How much speed can you trade for altitude now?

Correct ! You can trade 100kts.
You will be flying backwards then with regard to mother earth, but aerodynamically who cares ? You will still be flying.

If the relevant reference system changes it's state beyond what the AC can bear, well then: bad luck. but you would have the same problem when you are flying at 100kts and suddenly a tailwind of 100kts hits you. Won't make a difference except for the horizontal component during impact with mother earth...
Hmmm, headwind, tailwind, airspeed, groundspeed ?

And yes, the speed bleed-off is limited by the aerodynamics to keep the airplane flying. Though speed bleed-off is not the same as loss in inertial Ekin.

[Shadoko]

In the HS situation, the weight is zero, because the direction of movement is already downwards.
Waouh!
If a/c weight was rero, then she didn't fall!
Weight can't be cancelled. Balanced, perhaps (when the a/c flies), but cancelled, not!
"Weight is the name given to the force (http://en.wikipedia.org/wiki/Force) on an object due to gravity (http://en.wikipedia.org/wiki/Gravitation)." (Wiki). And excepted a gravity failure (:}), it can't be zeroed on Mother Earth

[henra]

@henra (http://www.pprune.org/members/327762-henra)
Hmmm, headwind, tailwind, airspeed, groundspeed ?

And yes, the speed bleed-off is limited by the aerodynamics to keep the airplane flying. Though speed bleed-off is not the same as loss in inertial Ekin.


Hmm, I don't want to sound rude, but did you really understand my example ?

And yes, the square of the speed before the bleed minus the square of the speed after the bleed is exactly the kinetic energy you can trade for altitude.
What is speed bleed if not redution of kinetic energy ???

Edit:
You really need to understand the concept of reference systems to get a grip on this.
Let me ask:
What do you think is the kinetic energy of the aircraft in my example after the speed loss of 100kts?
Please note: It is flying backwards now. Does that mean it has a negativ kinetic energy by now ?

Other question: Would the aircraft care if mother Earth instantly decided to change its sense of rotation by 180° from one second to the next?
You probably guessed it: It wouldn't give a sh't as long as the air around it keeps moving unchanged. The only force which the Earth itself applies to the aircraft is gravity and that is vertical.

Edit3:
Yes you can calculate the total kinetic energy of the AC with regard to the sun but that would be absolutely pointless. You can also calculate the kinetic energy with regard to the ground but for the question of how much altitude can I gain by giving up airspeed it is also irrelevant. It is only speed through the air which I can trade. When speed through the air is Zero there is excactly 0kts to trade. You can't get 'slower' than 0kts TAS/IAS/CAS. No matter what the surface below does. Or how the sun turns around this point.

[grity]

it was said before that the change of the direktion horizontal vers vertical cost an extra portion energie.... so the calculation was not much/exact valid it was under a limit value view, and yes it is possible to climb with an bird and change Ekin into Epot... (in detail the pressure on the water-surface deep under the bird has to rise a little bit, and the earth will change her position on her way round the sun also a liiiiitle bit)

a calculation just to control the plausibility of datas

and due to the lots of lessknown faktors (AoA, Cl, Cd, Cm, temp. density, spezific weight, reynold.....) it is just a practician desicion of the calculator if he will more talk over the marginal conditions or over the basic applications

and yes the used calculations of Ekin has some mistake in turbulence conditions with changes in the airspeed, this mostly cost a second portion of energie....

[henra]

One last admission from my side to end this energy discussion:
When I simply enter the 275 kts into the simplified formula of an E6B calculator I get 467,5 kts as TAS.
When calculating considering the Mach values I get between 475 kts (M0,80) and 490kts (M0,82) for an ISA temperature of -54,3° (ISA standard atmosphere at 35000 feet).

Depending on the real temperature this value can vary significantly and therefore the TAS can probably have been easily been 460kts as well as 500kts. We shouldn't read too much into it without knowing OAT.


Mach dependent TAS:
a0*M*sqrt(T/T0)
where
a0: speed of sound at S/L
M: actual Mach number
T0: ISA temperature at sea level in Kelvin
T: actual temperature.

[ChristiaanJ]

... when you are flying at 100kts and suddenly a tailwind of 100kts hits you.... henra, you're making a mistaek....
Your aircraft has mass/inertia, so it will not be instantly dragged along by your 100 kts tailwind. Your airspeed will now be 0 kts. Not a healthy situation....
Read up about windshear (not exactly the same, but similar).

[henra]

henra, you're making a mistaek....
Your aircraft has mass/inertia, so it will not be instantly dragged along by your 100 kts tailwind. Your airspeed will now be 0 kts. Not a healthy situation....
Read up about windshear (not exactly the same, but similar).




That is EXACTLY the point I was trying to make.

It was my point about change of state of the reference system in reply to his remark:

Yeah, suppose the windspeed goes from 100 knots back to zero, does this change the Ekin of the airplane ? If not, then you will need to take the groundspeed as speed reference.


My point being that for the problem of loss of effective Ekin to trade for altitude it makes no difference if you have a headwind of 100kts while flying 100kts, i.e. being at a standstill with regard to the ground and the wind suddenly stopping or
you are flying at 100 kts and are suddenly hit by a 100kts tailwind. In the latter case you have no airspeed left to fly after being hit by the wind either.

Seems my explanation was a bit brief last time..


Edit:
To give another example:
You have a Microlight tied to the ground and the wind is blowing at 70kts. What will happen if you cut the ties?
It will lift off and start to fly backwards with regard to the ground. You have traded speed for altitude at that moment. And it had kinetic energy with regard to the air at that moment although with regard to the ground it didn't. It's all about relevant reference systems....

[ChristiaanJ]

henra,
Sorry, I dropped into the Ekin discussion halfway. I agree with your point of view.

[mm43]

At post #657 (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-33.html#post6594272) HN39 made the following "tongue in cheek" comment -As a student I piloted gliders. These routinely fly tight circles to stay in thermals. In a strong wind there is no airspeed loss turning downwind, nor gain turning upwind. I've never quite figured that out, may be as a physicist you can.I don't think that everyone picked up on what he said, but the discussion over KE principles has been interesting and informative.:ok:

henra;
I believe the forecast temperature was -46°C at FL350, and I wouldn't be surprised if it was even warmer where AF447 was, e.g. -42/-43°C.

[henra]

At post #657 (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-33.html#post6594272) HN39 made the following "tongue in cheek" comment -I don't think that everyone picked up on what he said, but the discussion over KE principles has been interesting and informative.:ok:

henera;
I believe the forecast temperature was -46°C at FL350, and I wouldn't be surprised if it was even warmer where AF447 was, e.g. -42/-43°C.

Thanks mm43 !

That would give us a TAS of 489kts at M0,80 and 500kts at M,82.
Looking at the setting of the RTLU at the time of the beginning of UAS a Mach speed of roughly M0,80 seems likely. So we would be back somewhere around the 490kts and ~4000ft.

[takata]

Should not we have expected a relevant ACARS message ?
If 2 ADRs self auto detect at fault, should not we get SPD and ALT flags accordingly ?

a) PROBE-PITOT fault seems to be the relevant ACARS, by logic priority, over ADR faults which should have been compiled under the same ATA 341.
b) ADR fault is not self detected (there is no ADR internal failure) ; monitored channels (airspeed, Mach,...) are declared faulty by FMGCs and FCDCs, but they are still displayed.

[Dutch M]

@HazelNuts39 (http://www.pprune.org/members/305001-hazelnuts39)

Originally Posted by Dutch M
I'm not a pilot, though do have a degree in Applied Physics

As a student I piloted gliders. These routinely fly tight circles to stay in thermals. In a strong wind there is no airspeed loss turning downwind, nor gain turning upwind. I've never quite figured that out, may be as a physicist you can.
Yes, that is also one of the aspects I considered, though did not have enough time to dive into. Though 2 aspects might be relevant in this:
- Speeds are relatively low, glider speed and "jetstream".
- An important control target is the constant airspeed. Small rudder changes and/or differences in thermal-absorbing might hide the effects in speed changes.
- An experiment might be to circle around and measure the pitch angle and rudder usage during the circles. I would expect a somewhat sinus shaped change in rudder/pitch position.

Let me change the challenge a little:
- Land your glider with a airspeed of 30.25 m/s and a headwind of 30 m/s (just enough to move a little bit related to the ground).
- The presumed TAS based Ekin would be 0.5xmx915 =458 m J
- The moment the glider does touch down, everything becomes ground speed based and the ground speed based Ekin would be 0.5xmx0.25x0.25 = 0.03 m J.

Where did the Ekin of (458 - 0.03) m J go ?????

[henra]

Let me change the challenge a little:
- Land your glider with a airspeed of 30.25 m/s and a headwind of 30 m/s (just enough to move a little bit related to the ground).
- The presumed TAS based Ekin would be 0.5xmx915 =458 m J
- The moment the glider does touch down, everything becomes ground speed based and the ground speed based Ekin would be 0.5xmx0.25x0.25 = 0.03 m J.

Where did the Ekin of (458 - 0.03) m J go ?????


It got nowhere. The only energy that got converted into heat was the 1/2*m*(0,25m/s)^2 during braking on the ground.
With regard to the air the remaining 1/2*m*(30m/s)^2 is still in the glider. Being fixed on the ground it is effectively being towed through the air at 30m/s by the ground with regard to the air. See my example of the microlight.
If the wind breezes up by 1m/s to 31 m/s it will lift off again. Or push it forward at 1m/s and it will take off.
If the air is still you will have to push at 31m/s. Big difference for you, no difference for the glider for its ability to lift off and fly. The difference for the glider is how it will move in relation to the 'other' reference system, i.e. the ground.
That's why aircraft prefer to take off and land against the wind. Mother Earth gives a certain amount of kinetic energy to fly to the Aircraft for free. For the same Aircraft you need less energy (thrust*distance) to leave the ground. And upon landing you have to dissipate less energy in your brakes. Still in between you were equally able to fly as if you took off and landed with the wind.

The trick is that you need to understand that for an Aircraft once it has left the ground, the movement of the ground below is totally irrelevant for the ability to stay in the air. And it stays irrelevant until it contacts the ground again. In between only its relative movement through the air is relevant.

[ChristiaanJ]

At post #657 (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-33.html#post6594272) HN39 made the following "tongue in cheek" comment -I don't think that everyone picked up on what he said....I did, but I don't have all the answers, and formulas, and figures, at my fingertips any more...

To stir up the discussion, what about a 'breakdown' of the Ekin of a Fieseler Storch (or similar) flying at about 50kts in a 50kts headwind ?

[Dutch M]

@CONF iture (http://www.pprune.org/members/104576-conf-iture)

Ground speed is affected, but not airspeed.
Once airborne, the glider is in the air mass that is moving at the speed of the wind, but for the glider itself regarding that air mass, there is no notion of tail or head wind. Sure, but the remark is, the airspeed should change when the inertial speed stays the same, whereas the airspeed is perceived to be constant (which in effect isn't, but this is masked by other factors).

[Dutch M]

@rudderrudderrat (http://www.pprune.org/members/313106-rudderrudderrat)

Simply use the air mass as your frame of reference. It may be moving horizontally over the earth's surface, but the conservation of KE + PE still holds.
IAS is just a measure of dynamic air pressure, it must be converted to TAS.
Unfortunately it isn't. See my example about the landing glider, a few posts back. The airframe can't be the reference point for conservation of energy.

[CogSim]

The BEA to publish another report on Friday?
Link (http://bourse.challenges.fr/news.hts?menu=news_actualites&urlAction=news.hts%3Fmenu%3Dnews_actualites&idnews=RTR110725_0076O0IL&numligne=16&date=110725)

[Dutch M]

@henra (http://www.pprune.org/members/327762-henra)

It got nowhere. The only energy that got converted into heat was the 1/2*m*(0,25m/s)^2 during braking on the ground.
With regard to the air the remaining 1/2*m*(30m/s)^2 is still in the glider. Being fixed on the ground it is effectively being towed through the air at 30m/s by the ground with regard to the air. See my example of the microlight.
If the wind breezes up by 1m/s to 31 m/s it will lift off again. Or push it forward at 1m/s and it will take off.
If the air is still you will have to push at 31m/s. Big difference for you, no difference for the glider for its ability to lift off and fly. The difference for the glider is how it will move in relation to the 'other' reference system, i.e. the ground.
That's why aircraft prefer to take off and land against the wind. Mother Earth gives a certain amount of kinetic energy to fly to the Aircraft for free. For the same Aircraft you need less energy (thrust*distance) to leave the ground. And upon landing you have to dissipate less energy in your brakes. Still in between you were equally able to fly as if you took off and landed with the wind.

The trick is that you need to understand that for an Aircraft once it has left the ground, the movement of the ground below is totally irrelevant for the ability to stay in the air. And it stays irrelevant until it contacts the ground again. In between only its relative movement through the air is relevant.

Yes, the ability to stay in the air is a function of airspeed.
The inertial Kinetic energy is not a function of airspeed, a very subtle difference......

So the amount of speed which can be bled of is related to the min. airspeed to stay in the air. The actual amount of Ekin released is depending on the absolute speed compared to the fixed reference. The reference should at least be earth (-surface). (And when you get convinced of that, you will also understand the earth rotation stuff).

[Dutch M]

@ChristiaanJ (http://www.pprune.org/members/105267-christiaanj)

I did, but I don't have all the answers, and formulas, and figures, at my fingertips any more...

To stir up the discussion, what about a 'breakdown' of the Ekin of a Fieseler Storch (or similar) flying at about 50kts in a 50kts headwind ?
Let's extend this: Headwind 49.99 kts and the Storch is having a collide with a tower, best would be just above a platform.

What would happen: A very gentle little bump against the tower and then the subtle drop/land on the towers' platform. Nothing bent.

[gums]

I am amazed at all the kinetic energy and OAT and such discussion here for last two days.

The profile of AF447, as we know it, and regardless of control laws or pilot inputs, resembles the classic manner of getting the Viper into a deep stall. You simply climb at a fairly steep attitude, fairly level roll attitude, and at low AoA until you run outta energy, then sit there and watch the jet try to nose over too late. AoA increases rapidly, and with little or no "nose down" pitch moment available from the flight controls, you are there!!

The jet's "protections" (or limits, as I prefer) are fooled. We simply fly past the jet's control authority to provide the so-called "protections". Worse, and in the case of the Airbus, we have a myriad of reversion "laws" that could cause the crew to do something worse than just sit there and hold attitude/power. The overspeed warning is what I am concerned about, as that could explain either pilot or computer commands, or both.

I refuse to believe that the Airbus is a poorly-designed jet from the aerodynamic aspect. I truly believe you could exceed the mach "protections" until reaching maybe 0.95M or so with no ill effects. I truly believe that you could fly the jet at 10 or 15 degrees AoA. I truly believe you could pull 3 gees without the wings falling off. I truly believe the jet has exceptional lateral stability, or we would not see a proflile with a slow rotation versus a tendency to enter a spin.

What I do see is an embedded "autopilot" influence that changes control laws depending upon flight phase ( and Viper had some of those, but not to the extent of the Airbus). I see confusing cockpit warning/caution indications. I see no firm "hang your hat on the jet's capabilities" control law that the human crew can use when things go to hell in a handbasket. Worst of all, I see no aspect of the system that acknowledges loss of air data and simply reverts to a basic control law while the crew and HAL figure things out.

[HazelNuts39]

An experiment might be to circle around and measure the pitch angle and rudder usage during the circles. I would expect a somewhat sinus shaped change in rudder/pitch position. You'd be disappointed. The point is - if the wind speed is horizontal and constant in magnitude and direction, there is absolutely no effect on the airplane, except that the center of the circles moves over the earth surface at the speed of the wind. Except for that, the airplane flies perfect circles at constant airspeed, bank angle, pitch angle, angle of attack, and control surface positions.

Another matter entirely is a vertical wind component, or changes of wind speed or direction, but let's keep that for next year ...

[wilyflier]

That Old Chestnut

I had it beaten out of of me when learning pattern B instrument flying on a Harvard "circling upwind or downwind has no effect on your airspeed as you are only flying/ circling with respect to the airmass"
I was convinced I had to keep adjusting power as I went round the 360 degrees maintaining an exact height
However we were also warned to be careful turning downwind near the ground for fear of stalling due to visual illusions of speed
In gliding, circling on the ridge, if one correctly maintains airspeed there seems to be a need to speed up/nose down turning downwind, and there is surge of lift as you turn back into the headwind .Though the detail effects are distorted by the changes of updraft and windspeeds near the hill .
Nevertheless there is a loss of height turning downwind, and a regain height as you turn into wind.
It is also interesting how the angle of bank changes as you fly elliptically over the ground while performing a supposed perfect circle in the airmass?
Swirlyflier

[airtren]

Hello henra
It got nowhere. The only energy that got converted into heat was the 1/2*m*(0,25m/s)^2 during braking on the ground.


And that was the only Kinetic Energy that it had left, when it crossed the virtual border between the two reference systems - air, and ground.


With regard to the air the remaining 1/2*m*(30m/s)^2 is still in the glider.
Being fixed on the ground it is effectively being towed through the air at 30m/s by the ground with regard to the air. See my example of the microlight.

Then, when I am standing watching kids playing in the yard, under a breeze of 0.5m/s, I must have a 0.5m/s corresponding Kinetic Energy.... even though I don't move... ;)

The glider at this time does not move, so it has 0 kinetic energy. (relative to the ground, just to be accurate).

Kinetic Energy goes beyond Aerodynamics, and thus, similar examples are abundant in various other fields of the Dynamics, some involving wheels and legs, instead of air, and wings....

For instance the example of a train at a certain speed, and a passenger walking on the train: if the passenger hits an object on the train, his pain is going to be relatively little, when compared with the pain he would have if he hit somehow, an object on the ground - classic comedy films with guys walking on the top of the train, while the train goes under a very low overpass bridge, come to mind.

The passenger Kinetic Energy relative to the train is given by his walking speed, measured by the little pain of hitting an object on the train, while his Kinetic Energy relative to the ground, is augmented by the train's Kinetic Energy, measured by considerable more pain, and possible destruction in the second case..

With that, back to the glider example, the Kinetic Energy corresponding to the 30m/s speed wind, is the air's Kinetic Energy, not the glider's.

The glider on the ground, is like the passenger off the train - no Kinetic Energy from the air, none from the train. Put the glider on the air - push it to make it fly - it's like having the passenger back on the moving train.

All of these examples contain momentum, and inertia aspects, which may add to the fun, or to the confusion....


The trick is that you need to understand that for an Aircraft once it has left the ground, the movement of the ground below is totally irrelevant for the ability to stay in the air. And it stays irrelevant until it contacts the ground again. In between only its relative movement through the air is relevant.

After these examples it is also clear that it's good to keep the Energy Conservation equation pure, in its General and Universal aspects, which transgress the specifics of the Dynamics fields, like Aerodynamics.

[rudderrudderrat]

Hi Dutch M,

Unfortunately it isn't. See my example about the landing glider, a few posts back. The airframe can't be the reference point for conservation of energy.

I didn't say use the aircraft airframe as the reference - use the moving Air Mass as your inertial reference frame.
I seem to remember a certain Mr. A. Einstein wrote a special paper about it.

[HazelNuts39]

I truly believe you could exceed the mach "protections" until reaching maybe 0.95M or so with no ill effects. I truly believe that you could fly the jet at 10 or 15 degrees AoA. Your first sentence reminds me of D.P.Davies: "If you can choose between stalling and something else, choose something else" (IIRC). IMHO your second sentence needs to be qualified: At M.82 the airplane can be considered stalled at about 8 degrees, at M.6 (the speed at apogee, see the graph I posted recently) at about 11 degrees, whereas 15 degrees may be just flyable at Mach 0.2 - 0.3.

[airtren]

Thanks for this update, and recent posts with sharing more info on the TAS calculations.

I have not checked, but it is probably the case, that you've calculated with an unchanged TAS at FL375 of 390knots....

Thanks mm43 !

That would give us a TAS of 489kts at M0,80 and 500kts at M,82.
Looking at the setting of the RTLU at the time of the beginning of UAS a Mach speed of roughly M0,80 seems likely. So we would be back somewhere around the 490kts and ~4000ft.

[jcjeant]

Hi,

Gums
I refuse to believe that the Airbus is a poorly-designed jet from the aerodynamic aspect. Domaine-de-vol-A330.pdf (http://www.mediafire.com/?n2xw5vmn41glxy4)

[gums]

Yeah, 'nuts, the stall AoA for the Airbus may have something more to do with mach than I am familiar with. Most jets I flew stalled at an AoA, whether supersonic or subsonic. The supersonic regime is more complicated, but big deal. Only problems I ever saw with a subsonic design had to do with shock waves over the wings, ailerons and HS that caused neat things like control reversal and a nose down "tuck" that required you to reduce speed real quick using spoilers, speed brakes, reduced thrust, etc.

My point is that it is possible to "zoom" at a "comfortable" gee and AoA and then run outta energy and control surface authority, passing thru all the "limits" and "protections" that the system is supposed to provide. We proved the point back in the late 1970's in my little jet.

Can't get the download JC. Will try later. Is the point that the Airbus has crappy aero characteristics?

Respectfully,


P.S. I agree that avoiding a stall is a sound procedure. We can worry about pieces falling off later due to high speed or gee.

[jcjeant]

Hi,

Can't get the download JC. Will try later. Is the point that the Airbus has crappy aero characteristics?


Weird ... Mediafire is reliable host and work great here ...
You can try this multi links host ... (make your choice :) )
Multiupload.com - upload your files to multiple file hosting sites! (http://www.multiupload.com/M9ZYPMKPXZ)

[CONF iture]

ADR fault is not self detected (there is no ADR internal failure) ; monitored channels (airspeed, Mach,...) are declared faulty by FMGCs and FCDCs, but they are still displayed.
But are not NAV ADR FAULT and faulty ADR two different species ?

NAV ADR FAULT is the result of an ADR internal failure or a manual switch OFF.
faulty ADR provides erroneous information but is not an ADR failure.




Le Figaro (http://www.lefigaro.fr/actualite-france/2011/07/25/01016-20110725ARTFIG00350-af-447-le-rapport-d-etape-de-l-accident-publie-vendredi.php) set the table to kill the pilots a second time :
Les boites noires ont révélé que c'est une erreur de pilotage qui a entraîné le décrochage de l'appareil puis sa chute en 3 minutes 30 dans l'océan. Le pilote a en effet maintenu un ordre à cabrer -c'est-à-dire a tiré le manche de l'appareil- quasiment pendant tout le temps de la chute alors qu'un ordre inverse -pousser le manche- aurait empêché l'avion de décrocher puis aurait sans doute pu permettre de récupérer l'avion durant au moins la première minute de chute.
Do not expect anything different from the BEA on Friday ...

[jcjeant]

Hi,

Le Figaro (http://www.lefigaro.fr/actualite-france/2011/07/25/01016-20110725ARTFIG00350-af-447-le-rapport-d-etape-de-l-accident-publie-vendredi.php) set the table to kill the pilots a second time :Not particulary the "Le Figaro" but instead the "aviation expert" of "Le Figaro" I quote Fabrice Amedeo
Note that this journalist is firstly a leasure sailor :)
http://www.youtube.com/watch?v=yw26YkTxa9k
Maybe better for him to comment BEA Mer reports ....
BEAmer : Bureau Enquêtes Accidents de mer : Rapports d'Enqutes (http://www.beamer-france.org/publications-enquete-fr.html)

[Mr Optimistic]

So it looks like the report will confirm that the intial climb wasn't briefed to the Captain on his return and that the word 'stall' was not uttered, as the Chief Engineer stated some time back. I hope that the 60kt inhibit of the stall warning gets the attention it deserves.

[takata]

But are not NAV ADR FAULT and faulty ADR two different species ?
- NAV ADR FAULT is the result of an ADR internal failure or a manual switch OFF.
- faulty ADR provides erroneous information but is not an ADR failure.
You are semantically right concerning internal/external faults but what matter is that those erroneous informations won't be used by the flight systems but still be displayed to the crew for information and troubleshooting. All relevant systems based on erroneous outputs would be declared inop during the fault isolation sequence (AP/FD, A/THR, PROT, RTLU, WINDSHEAR, SPD LIM, TCAS)

Concerning FMGCs and FCPCs monitoring, the effect is a rejection of the faulty sources (channel); in our case, all 3 ADRs are declared faulty by them and rejected. There is no cockpit circuit breaker at probe-pitot level and what could be displayed is a fault on ADR pannel; one may want to turn it off.

Until all ADRs are turned off, the stall warning based on Alpha is still working (if at least one AOA channel is not declared faulty), but it's computed differently as this function use a Mach correction and Mach is replaced by a default value. On the other hand, the computed stall warning based on Low Speed (VSw) is lost. Concerning Overspeed warning, it is lost as this function is based on faulty ADR channels, as well as VMax which is not displayed.

[sensor_validation]

@sensor_validation (http://www.pprune.org/members/305146-sensor_validation)
Yeah, suppose the windspeed goes from 100 knots back to zero, does this change the Ekin of the airplane ? If not, then you will need to take the groundspeed as speed reference.

You need to keep your reference axes the same, moving at the same constant initial velocity then there is no change in Kinetic energy - but OK "v" is no longer airspeed, if windspeed changes.

The energy exchange Ekin vs Epot, is in general only valid for speeds in the direction of the change of Epot (ie Height) and not when trading speed between perpendicular axis.WRONG. Of course you have to make assumptions about constant windspeed, thrust=drag, g constant etc but correctly applied the maths/physics works, in 3-d vector co-ordinates - until you get close to speed of light!

And back to the point, the reference points quoted for AF447 are consistent with a zoom-climb trading speed for altitude. AF447 did not get caught up in 7000ft/min updraught where an external force supplied the work done to increase the gravitational potential energy.

Note - a zoom climb was discussed on these forums as soon as the wreckage position reported, way before the BEA confirmed it - it was the most obvious way AF447 could shed horizontal speed so quickly and end up so close to its last transmitted position.

[HarryMann]

As Takata has pointed out that is only partly true as below a certain speed the drag will rise again due to ending up in a less good cl/cd area (higher Alpha) of the wing polar. So at the end you can probably leave excess thrust largely out of the equation.Indeed, to confirm, the drag curve consists of profile drag + induced drag + Mach drag. The absolute value of the sum of these can indeed increase below a minimum drag speed, particularly approaching a stall, but between the normal cruise and maneouvring speed unlikely to increase much if any at all.

== DutchM ==

I really dont think you need ground speed for calculating those energy exchanges, TAS is fine surely... Unless you state you are allowing for windshear of thermal gusts , which we aren't are we, because we can't can we, because we don't know the figures do we. So we do the basic steady state air-mass TAS calculations, and bear in mind some variations may occur in practice... but if we're within the right cricketpitch, then fine.. that's what engineers do, get in the right region, check they've got the order of magnitude correct and then use some commonsense to make further deductions and corrections!

===========
Possibly worth consideration (as airline pilots seem increasingly unfamiliar these days with hand-flying through heavy thermal activity, wicked windshear or terrible turbulence - ?)

Flying in a +ve going thermal, with increasing x and z wind-vector components, glider pilots can find that stick back for extended periods is quite OK, with an almost unstallable feel to the aircraft (for reasons possibly explained some while ago)
Conversely, when this 'free energy' phase is exited, you are effectively in heavy adverse windshear, known to some as 'going over the falls' for obvious reasons! It's a horrible feeling, as if your very lifeblood was being drained... and if you don't respond, it may well be. (I've heard hang-gliders say they've had to hand-stand on the bar to prevent -ve 'g' tuck during some exits from the back-side of thermals.
Now, I'm definitely not comparing a 300 kt IAS airliner with an 80 lb hang-glider, even though the latter does have a sensible AR (8 to 10), span as big as a Spitfire and several hundred square feet of wing.

Only by strong pitch stability or quick and considerable ND inputs, is a very quiet & lonely sensation avoided, with a subsequent stall or wing drop...

So, it is interesting that a strong right wing drop seems to have had to be countered early on in this series of events, around when the climb started (strong and persistent wing drop, is frequently one wing entering quite different air than another). Then after quite safely holding NU (and a high angle of attack) for some time, we have the new THS* position... and a quite telling one I'm sure the report will atest to.

It is this * that our (hypothetical) glider pilots wouldn't have had to deal with... just a firm but controlled ND to accelerate back down through dirty colder slow air (!)

[airtren]

Post #710


The energy exchange Ekin vs Epot, is in general only valid for speeds in the direction of the change of Epot (ie Height) and not when trading speed between perpendicular axis.

WRONG. Of course you have to make assumptions about constant windspeed, thrust=drag, g constant etc but correctly applied the maths/physics works, in 3-d vector co-ordinates - until you get close to speed of light!

The way I read Dutch M's reference to Ek and Ep exchange, is that the Ek - or speed vector - need to have a vertical component (direction of height), for the energy conservation exchange to take place. Which is CORRECT.

With no vertical component, there is no height gained/lost, and no potential energy change, or exchange. An object that goes horizontally, from zero speed, all the way to a certain speed, will not get potential energy regardless of how slow, or fast.

[PJ2]

Hi gums;

IIRC, Tubby Linton provided a set of AoA graphs two or three threads ago, (now ancient history, at this pace!), repeated below, which show quite clearly, the effects of Mach, and of slats/flaps at lower speeds.

I had a long and very productive discussion with HN39 in the third thread earlier this year on "stall AoA". Davies discusses AoA's of 15deg and very early (Private Licence time in the '60's), I was left with the impression that "the" stall angle for transport aircraft was "15deg" (or so), altitude and Mach not considered; of course, this is not so but I never encountered a correction to that impression in my career...high altitude stalls were simply never done and never discussed, I think, with legitimate reason given limited sim time and expanding items to cover over the decades.

One can see the effects of extended slats and flaps and the AoA's are in accord with Davies' "approach case". IIRC he doesn't discuss high altitude stall in detail, even in his section on "jet upset". With increased Mach, I learned that the stall AoA reduces substantially - in the neighbourhood 4deg, not 15!, etc, as can be calculated from the tables below which are employed by the A330 FWC [Flight Warning Computer] to trigger the Stall Warning in other than Normal Law. In Normal Law, the Stall Warning will trigger, but only at an AoA > 23deg, as described in the chart.

HN39, it was indeed Davies who said, "...choose any other alternative...", etc.

PJ2


http://www.smugmug.com/photos/i-Qr5xMMw/0/XL/i-Qr5xMMw-XL.jpg

[rudderrudderrat]

Hi airtren,

With no vertical component, there is no height gained/lost, and no potential energy change, or exchange.
We are not considering ballistics.
Aeroplanes convert P.E. to K.E. on every descent by simply using the wings.

[bearfoil]

I think PF's initial ss back is starting to gel into the 'climb command', once again. Nothing about BEA suggests that is so.

As to Harry Mann's 'wing drop', as far as it may be the result of airmass flow, it may well indicate a very robust 'up elevator'.

Between the first NU and the second STALL WRN. , only Nose Down inputs are mentioned.

Roll excursions are mentioned. The a/c is climbing rapidly, rolling, and losing energy.

At the 'top' of climb, the AoA decreases, (6?), and there are STALL wrns.


Harry. Climbing, unstable in Roll (with corrections), and losing energy, would not the a/c STALL with increasing loss of altitude due loss of energy, regardless of pitch commands? as the a/c loses energy in climb, the AoA is affected as much by arrival at apogee as Pitch, perhaps more?

In a serious updraft, the correct input, (perhaps other than none!) might be Nose Down? Hold Altitude? Lose as little as possible?

BEA report seems to suggest that PF was not reacting to the climb. Too many here seem to assume the PF was "along for the ride".

Again, I think the source of the STALL was timed to the loss of the autopilot and autothrust. If in an uncommanded climb, of course the PF would not advance the Throttles. He would input ND, and BEA have not said he did not.

With the loss of 'g' at the top, TOGA and "back pressure" relief would be correct? Especially if associated with STALL WARN?

[airtren]

Hi ruderruderrat,
Hi airtren,

With no vertical component, there is no height gained/lost, and no potential energy change, or exchange.

We are not considering ballistics.
Aeroplanes convert P.E. to K.E. on every descent by simply using the wings.
An airplane descent implies a speed spacial vector that has a vertical component (vertical speed component), and so the Ep to Ek conversion takes place. And that is true in general with any descent, involving airplanes and wings or not.

If the airplane flies flat, horizontally, the vertical speed component is NULL, and there is no Ep change/exchange. An Ep to/from Ek conversion starts as soon as there is a non-NULL vertical speed component (up, or down) of the speed vector.

[bearfoil]

If unaccelerated?

[airtren]

If unaccelerated?
The aerodynamic braking during airplane controlled descent consumes the gain of Kinetic Energy, resulted from the Ep to Ek conversion, resulted from the loss of height/elevation. Slowing down for landing, means decreasing the Ek. What is left of the Ek, at touch down, is consumed (converted into other forms of energy) further through aerodynamic and mechanical braking.

The Ep to Ek conversion takes place regardless of controlled descent, or free fall. The difference is that in a free fall the Ek gain (or most of it, to be accurate) is not consumed/converted until the very end of the descent.

The airplane case is not different than a car descending a hill, from the generic Ep to Ek conversion perspective.

A car's free hill descent, will mean gain of speed - Ek not consumed. A controlled descent at constant speed, or decreased speed, requires different degrees of braking. The braking is consuming the Ek gain through friction, converting into Thermal Energy - brakes are quite hot at the bottom of the hill.

[takata]

At the 'top' of climb, the AoA decreases, (6?), and there are STALL wrns.Stall warnings started 15 seconds before the top of the climb, at 0210:51, when Alpha reached 6° (BEA).
0210:05 = 0210:05 => 275 kt; FL350; Alpha was about 3° (estim.)
0210:16 < 0210:50 => 215 kt; FL375; Alpha was about 4° (BEA)
0210:51 = 0210:51 => Stall Warnings; Alpha was about 6° (BEA)
0211:06 ~ 0211:06 => 185 kt; FL380; Alpha was about 16° (BEA)
During those 15 seconds at the beginning of the stall warning sequence (stall warning only stopped 35+ seconds later, after 0211:40)... the AOA increased by 10°.

[bearfoil]

Having a bit of a problem. As the a/c slows in a climb, AoA increases.

When the Nose dropped (it had to, yes?), the AoA immediately decreases (to +6). At this drop is when I propose the PF 'felt' the STALL, added TOGA, and 'relaxed' Back Pressure. He may not have relaxed it enough, and the a/c may have input NU instead of "minimizing altitude loss" (a very wrong thing to do, at this point!) PITCH is for drama? AoA is directly related to STALL, and what the PF "feels". In the dark, Pitch is "irrelevant"?

[Linktrained]

What is the effect of increasing thrust with underslung engines on the uncorrected pitch of an aircraft ?

[BOAC]

When the Nose dropped (it had to, yes?), the AoA immediately decreases (to +6). - where do you see this and why would the nose 'have to drop'?

[airtren]

... the word 'stall' was not uttered, as the Chief Engineer stated some time back. I hope that the 60kt inhibit of the stall warning gets the attention it deserves.
I would go further than hope.... The Chief Engineer should be really worried and should drive the addressing of the problem that the word STALL was not BIG on the screen for everyone in the cockpit to see it clearly, after Stalling and for most of the STALL duration.

[ChristiaanJ]

Having a bit of a problem. As the a/c slows in a climb, AoA increases.
When the Nose dropped (it had to, yes?), the AoA immediately decreases (to +6). At this drop is when I propose the PF 'felt' the STALL, added TOGA, and 'relaxed' Back Pressure. He may not have relaxed it enough, and the a/c may have input NU instead of "minimizing altitude loss" (a very wrong thing to do, at this point!) PITCH is for drama? AoA is directly related to STALL, and what the PF "feels". In the dark, Pitch is "irrelevant"?

Your literary efforts resemble those of 4th century 'philosophers'.
They're amusing.... which is why you're not on my "ignoramus" list yet, but they pollute the current discussions.
Some intelligent input from you would have been useful..... as I don't think you're just stupid.

[bearfoil]

BOAC

"had to drop". IF the PF had been trying to arrest the climb, (BEA have not located the NOSE Down inputs, time wise), He would have arrived at a ND a) eventually, b), in spite of elevator authority (due loss of energy), or c) STALL.

I think it extremely unlikely the a/c remained Nose up through the ordeal of the climb without it dropping @ "AoA decreased to 6, and STALL WARN." Yes?

ChristiaanJ sorry, I'll leave. Had a stroke last year. Memory and other things are a bit different.

[gums]

Thx, PJ, good review.

Gotta admit, that after a few years in straight wing planes I was then spoiled by sturdy subsonic wings and true supersonic wings. My straight wing jets "stalled" as you and the experts state. The shock waves over the wings caused by just a slight increase of AoA did more than cause the wing to lose lift, like the phenomena I described - aileron reversal, elevator reversal, etc. Scary, but I learned not to press the 'envelope" after some hairy moments.

THE RELEVANT POINT is if the crew tried to stop the "overspeed" warning by pulling up to slow down, then they could have entered a stall that they had not anticipated, way before speed was a factor. My training was to reduce power first, as pulling up got one closer to a stall and/or had other bad effects.

MY SECOND RELEVANT POINT ( IMHO) is that one can zoom at a comfortable AoA and gee and then run outta air molecules over the wing very quickly. By the time your AoA "protection" triggers, you are too slow for effective nose down control authority depending upon pitch moments determined by c.g. and basic aero characteristics of the jet. Back in 1979 we couldn't believe it would happen to our little rascal, but it did! It's why I joined the fray here when I saw more and more details of the crash. I simply wanted to point out that there are situations that the engineers never anticipated, whether "clever" maneuvers by the humans, or assumptions that the engineers made in the basic control laws.

Give me a 'bus and I believe I can duplicate the scenario easily. It is EXACTLY the scenario we discovered. Sure, pitch attitudes much lower, AoA much lower, but the identical scenario.

I pray that the users look at training, and remember the incidents of pitot-static failures.

And to beat a dead horse, I question the lack of design to allow for loss of the air data and still have a flyable jet. It ain't rocket science. Use last reliable data or use generic values depending upon gear up or gear down, etc. The Shuttle doesn't/didn't use air data until way slow. It was body rates, gee and such. The FBW systems use air data for "gains" - to command both rates and degree of control surface movement. Makes the jet "feel" like the old days, and it's a good thing. I would be the last pilot to recommend "direct" commands except as an absolute last-ditch maneuver. It's too easy to limit control surface movement according to "q". And body rates are easy to take into account without any air data at all. We only lost one jet I know of when the radome and pitot-static probes and AoA cones were ripped off. The guy flew for 10 minutes or more IFR (due to pelican blood over the canopy, heh heh). The body rates and 'standby gains" of the FLCS kept him flying on instruments until he gradually got into a PIO and had to bail.

[PJ2]

My training was to reduce power first, as pulling up got one closer to a stall and/or had other bad effects.
Ours too - in mountain wave for example, the power comes off...sometimes to idle thrust, then picks up again as speed reduces and stabilizes. A manual pitch up in response to an "overspeed" is a very long way from a normal, trained-and-checked SOP response, (I don't believe it occurred here). The "Overspeed Law" will pitch the aircraft up at VMO + 6kts or at MMO + M0.010 to M0.015 depending upon initial pitch attitude. The response, IIRC, is about 0.05gee - very gentle, and the power reduces; (the Autopilot does disconnect in this circumstance).
By the time your AoA "protection" triggers, you are too slow for effective nose down control authority depending upon pitch moments determined by c.g. and basic aero characteristics of the jet. IIRC, there have been comments that elevator effectiveness was not lost entirely, nor was it entirely lost throughout the descent. The discussion on whether elevator alone, without rolling the THS towards the ND position, and including the elevator's reduced effectiveness at its full-down position, could have recovered the aircraft has been had; we'll see on Friday whether this discussion was also had by the BEA.

[sensor_validation]

What is the effect of increasing thrust with underslung engines on the uncorrected pitch of an aircraft ?

Pitch up of course, but what was the thrust setting before increase - 90+%? So the converse, throttling back the engines to flight-idle, which was tried later should have a more dramatic effect in what should have been the right direction.

[DozyWannabe]

@gums, PJ2

As far as I was aware there was no overspeed warning though - have I missed something?

[A33Zab]

You are semantically right concerning internal/external faults but what matter is that those erroneous informations won't be used by the flight systems but still be displayed to the crew for information and troubleshooting. All relevant systems based on erroneous outputs would be declared inop during the fault isolation sequence (AP/FD, A/THR, PROT, RTLU, WINDSHEAR, SPD LIM, TCAS)

Concerning FMGCs and FCPCs monitoring, the effect is a rejection of the faulty sources (channel); in our case, all 3 ADRs are declared faulty by them and rejected. There is no cockpit circuit breaker at probe-pitot level and what could be displayed is a fault on ADR pannel; one may want to turn it off.


ADR Single and ADR Dual faults are detected by ADR itself.
A Triple ADR Failure message (ADR 1+2+3 FAULT) only exist if the BUSS option is installed, this is a level 3 (Red & Master Warning).
This Triple ADR monitoring was NOT installed on the A/C.
A local ADR fault without ECAM message doesn't seem logical to ECAM protocol.

I really can't find a statement that FCPCs would reject more than 1 ADR source.
If 1 ADR is rejected the FCPC(PRIM) will use the average of the other 2.
NAV ADR DISAGREE is triggered if these 2 values deviates a certain value.
or if all 3 sources deviates from each other.
This message and following ECAM crew action demands the crew to monitor and switch of the ADR in error, to prevent it being used by FCPC.

~o~

FCOM:

MAIN REASONS FOR ERRONEOUS AIRSPEED-ALTITUDE DATA

The most probable reason for erroneous airspeed and altitude information
is obstructed pitot tubes or static sources.
Depending on the level of obstruction, the symptoms visible to the flight
crew will be different.
However, in all cases, the data provided by the obstructed probe will be
false.
Since it is highly unlikely that the aircraft probes be obstructed at the
same time, by the same amount, and in the same way, the first indication
of erroneous airspeed-altitude data available to flight crews, will most
probably be a discrepancy between the various sources.


CONSEQUENCES OF OBSTRUCTED PITOT TUBES OR STATIC PORTS

All aircraft systems using anemometric data have built-in fault
accommodation logics.
The fault accommodation logics are not the same for the various systems;
but all rely on voting principles whereby when one source diverges from
the average value, it is automatically rejected and the system
continues to operate normally with the remaining two sources.
This principle applies to flight controls and flight guidance systems.

Normal situation
Each PRIM receives the speed information from all ADIRUs.
It compares the 3 values.
Pressure altitude information is not used by the PRIM.
Each FE (Flight Envelope computer) receives the speed and pressure
information from all ADIRUs.
For each of these two parameters, it compares the 3 values.

If one ADR output is erroneous and the two remaining ADRs are correct
The PRIM and the FE eliminate it without any cockpit effect (no caution;
normal operation is continued), except that one display is wrong and CAT III dual
can no longer be available on the FMA.

If two ADR outputs are erroneous, but different, and the remaining ADR is correct,
or if all three are erroneous, but different
The autopilot and the autothrust are disconnected by the FE (whichever
autopilot is engaged).
If the disagree lasts for more than 10 seconds, the PRIM triggers the ADR
DISAGREE ECAM caution.
It reverts to Alternate 2 law (without high and low speed protection).
On both PFD, “SPD LIM” flag is shown, no VLS and no VSW is displayed.
This situation is latched, until a PRIM reset is performed on the ground
without any hydraulic pressure.
However, if the anomaly was only transient, the autopilot and the
autothrust can be re-engaged when the disagree has disappeared.

If one ADR is correct but the other two ADRs provide the same erroneous output or
if all three ADRs provide consistent and erroneous data
The systems will reject the “good” ADR and will continue to operate using
the two “bad” ADRs.
This situation can be met when, for example, two or all three pitot tubes
are obstructed at the same time, by the same amount, and in the same way.
(Flight through cloud of volcanic ash, takeoff with two pitots obstructed by
foreign matter (mud, insects)).

Human beings (the pilot) tend to use the same type of “fault accommodation”
principles to detect an erroneous IAS/altitude indication.
Flight crews will tend to reject the outlier information, if the other
two outputs are consistent.
This choice is, in the great majority of cases, correct; but, all flight crews
should be aware of very extreme and unlikely situations where two (or
even three) speed/altitude indications can be consistent and wrong.

- BEWARE OF INSTINCTIVELY REJECTING AN OUTLIER ADR

The following chart provides a non-exhaustive list of the consequences of various cases of partially or
totally obstructed pitot tubes and static ports on airspeed and altitude indications. It should be noted that
the cases described below cover extreme situations (e.g. totally obsctructed or unobstructed drain holes)
and that there could be multiple intermediate configurations with similar, but not identical, consequences.

http://i474.photobucket.com/albums/rr101/Zab999/PITOTPROBLEMS.jpg

Based on the information given in the preceding chart, it is clear that no single rule can be given to
conclusively identify all possible cases of erroneous airspeed/altitude indications. However, any case of
erroneous speed/altitude indications will always be associated to one (or more) of the following cues :
a) Fluctuations of airspeed indications;.
b) Abnormal correlation of the basic flight parameters (IAS, pitch, attitude, thrust, climb rate) :
– IAS increasing with large nose-up pitch attitude;
– IAS decreasing with large nose down pitch attitude;
– IAS decreasing with nose down pitch attitude and aircraft descending;

c) Abnormal AP/FD/ATHR behavior;
d) Undue stall warning or overspeed warnings;
e) Reduction of aerodynamic noise with increasing IAS;
f) Increase of aerodynamic noise with decreasing IAS.

RECOMMENDED PROCEDURES

The procedures described below are intended to provide flight crews with
general guidelines to be applied in case of suspected erroneous
airspeed/altitude indications.

FOLLOW ECAM ACTIONS
if failure undetected:
CROSSCHECK ALL IAS/ALTITUDE SOURCES:
ADR1,ADR2,ADR3 AND STANDBY INSTRUMENTS

If it is obvious that the outlier is wrong, select the corresponding ADR OFF
and reconfigure the PFD indications accordingly, by applying the ECAM drill

which will be automatically displayed.

Flight crews should, however, be aware that in very extreme

circumstances, it may happen that two, or even all three ADRs may

provide identical and erroneous data.
Therefore, the suspect ADR should only be switched OFF, if it is positively
confirmed that the two other ADR's are correct. If in doubt :





DISCONNECT AP,FD AND ATHR
FLY TARGET PITCH ATTITUDE AND THRUST SETTING

The initial pitch attitude and thrust values given in the QRH should be
considered as "Memory Items", since they allow "safe flight conditions" to
be rapidly established in all flight phases (takeoff, climb, cruise) and
aircraft configurations (Weight and slat/flaps).

Once the target pitch attitude and thrust values have been stabilized,

the expanded data of the QRH (Flight with Unreliable Speed Indication)
should be followed to determine the precise pitch attitude and power
setting required, as a function of the aircraft's weight, configuration and
desired speed.
After applying the QRH procedure, and when the aircraft is stable, the
flight crew should try to identify the faulty ADR (one or more).
Once the discrepant ADR has (or have) been positively identified, it
(they) should be switched OFF.
This will trigger the corresponding ECAM warnings and the associated
drills which should be followed to address all the consequences on the
various aircraft systems.

[PJ2]

As far as I was aware there was no overspeed warning though - have I missed something?
The notion that the PF was responding to an "overspeed indication" on his PFD has been put forward a number of times as a reason for the pitch-up. There is no basis for the theory in any information currently available. The FWC does not send either the Stall or an Overspeed event to the ACARS, (which is, after all, a maintenance tool, not an investigative installation) and the BEA Update does not provide any information to support the notion.

[gums]

Yeah, Doze, and PJ has corrected me.

Consider me "corrected", heh heh.

Looking for a plausible reason to command a pitch change, especially after the pilot stated he had assumed manual control and another comment about "alternate" laws.

[bubbers44]

Hopefully Friday we will know if an overspeed warning caused the pf to pitch up. I will be glad when that dispute is over. It is the simplest explanation of why they zoomed 3,000 ft. I flew sailplanes and towed them before the airline career began but like Sully, don't think it would have helped in either situation with a jet airliner. Good basic flying experience though. Something not encouraged much any more with automation unfortunately.

[andianjul]

Gums
I'm sure I'm not alone in enjoying your insights into computer controlled flight based on your experiences in jet fighter aircraft and your associated 'war' stories. Please keep them coming. As to the possibility of flying the 330 into a similar engineer-unexpected, computer-defying, state as you suggest may have occurred, I hope that the designers of future passenger jets flight computers, systems, et-cetera, are informed in their approach to their task by the demise of AF447.

[JD-EE]

Dutch M, regarding the energy calculations you're asking questions that don't quite make sense in physicist terms.

If one wants to get VERY technical said airplane has an incredible amount of energy, and angular momentum, if calculated referenced to some as yet undetermined center of mass of the total observable universe. It's tiny speed changes won't change that energy more than a wiggle many decimal places out. It's not worth it to try to make that calculation simply because we don't observe it from that point in space time. We measure it typically from a reference on the Earth's surface. And the numbers in that sense work.

You mention stopping the Earth's rotation. For an Earth based observation that vastly changes the energy of the plane. Observing from the plane it makes no change, the energy is zero because the plane is not moving relative to the plane and is at zero height relative to the plane. Of course, this skirts the issue of what happens to the air mass over the Earth on the scale of the plane? I'm not sure it's fruitful to discuss this. By the time you appropriately account for the shifted frames of reference it all washes out anyway. It must or the physics that make your plane fly wouldn't work.

Referenced to a point on the Earth, conveniently directly below the plane, you can calculate an instantaneous "energy" value, mgh plus mV^2. (Note that squaring a velocity vector erases the direction part and leaves speed squared.) At 35000' and a given velocity it has one energy. At 37500' and a new velocity it has a new energy state. We also must consider the thust of the engines over time and the drag over time as two distinct energy inputs, initially balanced and more or less balanced once the plane is at the new altitude. What additional drag happens to subtract energy from the aircraft? We don't particularly know. And I certainly don't know how "more or less" my blithe "more or less balanced" is. Would it be accelerating once it levels out or not?

I certainly don't have the knowledge of the aircraft to handle these extra energy terms. BEA should. What I can do is work out the values and wave hands. It appears the altitude gain and speed loss were "sane", meaning there was no mother of all wind influences on the plane. It does not rule out a 100 mph level or smaller influence, at a semi scientific wild assed guess level of accuracy. The BEA phrasing doesn't tell us whether PF felt a downward movement and tried to counter it or not. It does imply a possibly unusual lag between a very serious climb and application of climb command on the stick.

What more can we say?

Edit: We can say that the ascent rate was about 84 miles per hour. So my 100 MPH wind level swag might be excessive.

[3holelover]

Gums
I'm sure I'm not alone in enjoying your insights into computer controlled flight based on your experiences in jet fighter aircraft and your associated 'war' stories. Please keep them coming.You are most certainly not alone.:ok:

[JD-EE]

jcjeant, it's simplest to rule out more than one "failure" per incident. Look for a failure (in reliability speak terms) that could cause the given effect. There might be say 20 such failures. If nothing fits start looking for combinations of failures that could lead to the overall results. That's maybe 400 combinations to consider. Three such failures is 8000 combinations of those 20 items, alone, to consider. And once you consider one of the 20 plus something else you may discover something else might be 5 or it might be 50 different failures could lead to the results.

Considering "partly failed" becomes a nightmare.

And I suspect BEA is being just a whole lot more methodical working through the various trees and figuring out what external influences the plane experienced than we are.

So I figure it's not time to worry yet about conspiracies or pinning blame where it does not belong. And I note you're not working to go beyond "failure" to find "cause" which is required before you can assign "blame." You're before the cart the horse putting. (or something.) It does SEEM like you're very anxious to get to the blame part. OUR analysis here isn't anywhere near that, yet.

For people who lost a loved one it's quite natural to want to find a target at which they can lash out and vent their fury. Premature action leading to selection of the wrong victim for that fury can be most tragic. (This is often how feuds and wars begin.)

[DJ77]

Give me a 'bus and I believe I can duplicate the scenario easily.

Not so sure you could.

I think the scenario you describe explains why the “bus” FBW computers calculate a “phase advanced AoA” as mentioned in the A340 zoom climb incident report. Remember the bus has a pitch attitude protection (IIRC: 30 deg NU progressively reduced to 25 deg at low speed). With that limitation and factoring pitch inertial moment and tail effectiveness it must be relatively easy to anticipate and prevent the AoA to become greater than alpha prot. Of course, this works only in normal law.

[JD-EE]

As a student I piloted gliders. These routinely fly tight circles to stay in thermals. In a strong wind there is no airspeed loss turning downwind, nor gain turning upwind. I've never quite figured that out, may be as a physicist you can.

The same way a tacking sailboat can go faster than the wind. If you hit the wind at the right angle with an airfoil you can acquire energy from the wind. Of course, the sailboat has its keel to make this effect more pronounced. That allows its crumby airfoil called a sail to work. The sailplane has only its mass to provide the effect.

[JD-EE]

Yeah, suppose the windspeed goes from 100 knots back to zero, does this change the Ekin of the airplane ? If not, then you will need to take the groundspeed as speed reference.

The energy exchange Ekin vs Epot, is in general only valid for speeds in the direction of the change of Epot (ie Height) and not when trading speed between perpendicular axis.

This is why I use the surface of the Earth as a reference. Then you find it easier to include the effects of thrust, drag, and wind. If the wind stops there is no change in the energy of the aircraft except through changed drag and lift.

[JD-EE]

Where did the Ekin of (458 - 0.03) m J go ?????

Nowhere. You changed frame of reference. You can't do that when calculating energies unless you take account for the different energy states of the frames of reference.

The glider that lifts and sails backwards relative to the ground is not trading velocity for height. The wind against the glider that is moving at a different rate generates both lift and drag. Those are forces which will change the glider's energy picture relative to its starting point. Rigorous application of forces and frame of reference can tell you what the plane or any other object is going to do.

Without considering the external forces you're hand waving. And, yes, we were hand waving to get a feel for what an ideal energy exchange would give. Once you add the external forces applied to the plane you can account for some discrepancies. If you include enough of the known forces you can deduce what additional force must have been applied to get the final result.

If I knew what climb rate to expect from a 10 degree angle of attack we could probably deduce whether or not there was wind speed, relative to the ground, working to alter the aircraft's energy profile. On doing an obvious estimate (rather than exact math) the plane was moving upwards at something around 80 MPH when it was going 7000'/min. So that motion is slow enough external winds could have been a factor. The climb rate expected for the plane's condition would nail this down a little tighter. And the wind itself would impart forces on the plane which would change it's apparent energy profile.

But, first, keep everything in one frame of reference. As soon as you change frames everything gets all gooey and slippery to think about. It's also best to consider a nice conceptually solid frame of reference so that it's easier to think about what's happening. Referencing the air mass is tricky because it's a changing reference.

[JD-EE]

Let's extend this: Headwind 49.99 kts and the Storch is having a collide with a tower, best would be just above a platform.

What would happen: A very gentle little bump against the tower and then the subtle drop/land on the towers' platform. Nothing bent.

Not quite. The plane would still be "flying" while touching the platform as long as the platform is not applying any force to the plane. If you change the control surface settings you can generate a net downward (and backwards) force on the platform that must be taken into account. Or you can lift off again and ride along 0.2 mm off the surface of the platform. When in that stable condition the forces on the aircraft are balanced, and easiest viewed and determined by considering the ground as your reference.

(Then ask yourself if having said sail plane stationary 0.2mm above the ground neither ascending nor descending is at all realistic.)

[JD-EE]

OK465, what wilyflier was saying, in essence, is that the perfect circle relative to the airmass does not change the forces upon the aircraft so it maintains its altitude. If you try to fly a perfect circle relative to the ground that's a different story.

Consider the forces acting upon the plane as well as whatever frame of reference you are using. (And if the airmass is in some way changing the inertia of the aircraft must be considered in your estimates of what is happening.)

[JD-EE]

Airtren, IMAO the plane's software declares stalls inappropriately. The stall at 2 h 10 min 05 is likely spurious related to the airspeed indication dropping even though the plane is still flying at altitude with very little real speed change.

If it was real the plane canceled it inappropriately when the real velocity was still high and the indicated air speeds were below 60 kts. It should be 'obvious' to the software that if the plane was really stalled, it's inertially derived ground speed had not changed, that it was still stalled.

If it was a spurious warning the plane should have cross checked inertial data with air speed data and decided the warning was spurious.

The warning at 2 h 10 min 51 was probably real. By then the pilot was confused by the on again off again stall warnings and not sure if this one was real.

Couple this with the PF's initial apparently inappropriate action and I'm not sure what I'd expect the PF to do.

What I really want to know is WHY the PF might have might have made this apparently inappropriate action. If he was still thinking he clearly thought it was the right thing to do. Once PF had the plane at 16 degrees pitch and an AoA of 60 degrees I am reasonably convinced it was all over. There was not enough altitude to get the plane back into a flight configuration based on the NASA curves posted here in the past.

So once the pilot made that inappropriate move the plane's responses to his actions certainly did not help. PF needed something to beat into his brain (a physical slap in the face?) to convince him he was stalled. Turning off the warning is not going to do that.

[JD-EE]

PJ2, please forgive an assinine comment or observation here....

My understanding is that in aircraft pull on the yoke is go up. This was true from day one. The joystick handles the same way.

Now, take that joystick and mount it on a panel that is vertical. Diddle it with your fingertips resting on a sturdy arm rest. If you diddle it up the plane should go up, it's the way people normally think. Translate that "diddle stick" back down to mostly horizontal on the arm rest and you have chaos.

Could the pilot have somehow slipped into a thinking mode that had push is up? That's what the little diddle knob on my Lenovo laptop does. Push to move the cursor up the screen.

Is this a hidden danger in joystick aircraft control? Get too used to a laptop or something and when a crisis hits you revert to laptop thinking and do the wrong thing.

Note that in this case I'd expect PNF to take notice. Somebody noted that the stick inputs are indicated on the displays. So if the appropriate display was on the PNF's scan it should have been noticed.

[JD-EE]

Energy Management (EM) in a fighter aircraft had nothing to do with the Earth frame of reference, other than avoiding contact with it.

I'm beginning to feel like I was lied to all those years and never noticed it.

Not really. Understanding the forces on the plane requires knowledge of what the plane is doing relative to the air mass. When you have have an air mass that throws curves at you knowing what the plane's going to do may become more difficult due to the plane's inertia. Considering only the air mass is good for estimating which direction the energy will change. For more absolute numbers one must consider that large annoying attractive lump of hard stuff far below. Then you know "how much" the energy changed and what factors are contributing to that change including changes in the air mass.

[EMIT]

JD EE

Stick input is displayed ONLY on the ground, to enable flight control check and to monitor stick inputs during ground roll. As soon as aircraft is airborne, the "Iron Cross" and its reference box disappear from the ADI on the PFD (that is the Attitude Director Indicator on the Primary Flight Display).

As soon as the aircraft is airborne, aircraft response indicates what (the hell) the pilot flying is doing with his side stick.

Mix up of sidestick inputs such as you describe does not seem very logical to anybody who has handled aircraft controls.

[PJ2]

gums;

First, yes sir, keep it comin'.

Second, why the pitch-up? I think the answer will be straightforward, not complex at all.

[Machinbird]

Quote:
Originally Posted by gums
Give me a 'bus and I believe I can duplicate the scenario easily.

DJ77
Not so sure you could.

I think the scenario you describe explains why the “bus” FBW computers calculate a “phase advanced AoA” as mentioned in the A340 zoom climb incident report. Remember the bus has a pitch attitude protection (IIRC: 30 deg NU progressively reduced to 25 deg at low speed). With that limitation and factoring pitch inertial moment and tail effectiveness it must be relatively easy to anticipate and prevent the AoA to become greater than alpha prot. Of course, this works only in normal law. DJ77, I think we have already seen what can be done with an aircraft when it doesn't have good airspeed information to the computers. I concur with Gums that it would be easy to duplicate this scenario. Wouldn't be that hard to do any number of aerobatic maneuvers that you are not supposed to do with the beast. You would just have to sit down and do the calculations first to avoid breaking things.

Even the direct hydraulic control A-4 Skyhawk and F-4 Phantom could run out of control effectiveness and end up back sliding/falling at higher nose up attitudes.

I would hate to take an F-4 in autopilot Control stick steering mode (which is very much like the mode that AF447 was in when it lost control) and do anything but essentially level flight. (You former F-4 flyers should remember what this was like). It would be too easy to set an unstable attitude and decelerate/accelerate. (basically a pure attitude hold).

The control inputs made by the AF447 crew as presented to date by BEA only seem to make sense WRT seat of the pants flying. I hope BEA has been able to make some sense of the control inputs and their rationale when they give their next interim report.
I'm having trouble believing that there was almost no scan of the instrument panel going on.

JD-EE. That was a very respectable explanation for the problems with Dutch_M's "paper." Newtonian Physics should work properly in any frame of reference and give consistent results. When it doesn't work out that way, then there is a problem with the analysis.:ok: