AF 447 Search to resume

[mm43]

originally posted by Low Flier ...

The other way would have been for Emeraude to weight down the tail end of the towed array and to cruise much much slower. The TPLs I was referring to were towed by USN surface vessels, whereas L'Emeraude was using her Sonar Dome detection system which was optimized to 37.5kHz post 01 July. There was a strict control system set up in Brest to ensure that there were no conflicts with the Emeraude and the surface vessel's towed gear.

mm43

[mm43]

In post #1216 (http://www.pprune.org/rumours-news/395105-af-447-search-resume-61.html#post5718760) Bearfoil wrote:-
The spoilers are part of the upper wing surface. The recovered Spoiler shows evidence of collapse in a deployed position.Why would the Port Outer Spoiler (the recovered one) have been deployed?

My understanding is that the outer spoilers can only be deployed following both MLG on the deck when landing or in a RTO above 72KT. Both outer spoilers are not used for speed brake or roll.

The Speed Brake section in A340 - A330 Control: Flight Laws (http://countjustonce.com/a330/a330-flight-laws.html) gives a fairly concise description.

mm43

[bearfoil]

mm43

My recall is that the spoiler recovered was the Port, Inner.

[CONF iture]

Don't worry about how this hypothetical pressure build up could happen just yet. The key questions I am hoping to answer are,
(1) Would this scenario likely proceed to a sad conclusion?
(2) Is Pilotaydin's sim experience technically flawed in its description?
(3) If the sim experience is technically valid, how could you break the sequence of events?
(1)(2) For sure when the airplane is stalled (however are the Pitot tubes and their respective drain hole, still obstructed or not) the indicated airspeed will decrease as the airplane is going down, high speed protection will cease and alpha floor should soon trigger but with an airplane already fully stalled. Then it all depends how the pilots will manage to exit the stall : Some guys tried it in a simulator and the only way they managed to recover from a deep stall was to select some flaps out … Now, is that specific simulator really representative of the airplane ?

(3) To prevent such scenario to fully develop, only a binome of 007 agents would deactivate the high speed protection as soon as triggered by degrading the system to alternate law which could be done by switching OFF two of the ADRs.

As I didn’t get the opportunity to practice any of this in a simulator, I cannot guaranty the reasoning behind.

[mm43]

Bearfoil wrote:-
My recall is that the spoiler recovered was the Port, Inner. Yes, and also the Port Outer which was found on 13 June at 1321z in position 04°42.1'N 029°55.6'W, or 42NM approx N by E of TASIL. Both were reported by the BEA to have suffered the same fate.

http://i46.tinypic.com/rc5351.jpg

I have an image of the top surface somewhere, and will post it when I find it.

EDIT :: Pic #1 and #2 show the spoiler on the surface when found and the last two shots are quite clear in showing the underside damage.

http://i46.tinypic.com/2guziw7.jpg

http://i46.tinypic.com/2wmhr2x.jpg

http://i46.tinypic.com/14m3r6a.jpg

http://i47.tinypic.com/2cylmr8.jpg
mm43

[auv-ee]

I think they are effectively quoting from the TSO C121 spec. The following snippet from their manual would indicate something different:-

It could well be that the spec merely quotes the TSO. It might be that we see only the spec representing what the pingers were once like, without any clue about the present behavior, or the spec might still represent the present design, if little has changed. It is hard to know without more detail. I notice that Benthos has the same spec on their pingers.

It appears the 37.5kHz piezo-ceramic transducer looks after itself, and the only requirement is for the 10msec duration switching pulse every second, and that would be derived from a separate time base.

I don't think the excerpt from the manual sheds much light on the question. It still implies that the "signal" (already generated) is applied to the transducer, not that the transducer is part of the oscillator circuit. The former (signal drives transducer) is, in fact, the normal approach to generating pings in underwater transducers. A piezo transducer, coupled to water, has a Q of about 3 to 5, which is not really narrow enough to control the frequency within +/-2.7%, as called for by the spec. Thus there must be one or more time bases to generate the 37.5kHz, 10ms and 1second timing.

[mm43]

Originally posted by auv-ee
A piezo transducer, coupled to water, has a Q of about 3 to 5, which is not really narrow enough to control the frequency within +/-2.7%, as called for by the spec. Thus there must be one or more time bases to generate the 37.5kHz, 10ms and 1second timing. Ok. We've done this to death, and I suspect you are right with one or two earlier stages to improve the Q. But it potentially shows that with the loose spec, that the likelihood of two pingers on the same aircraft chirping at the same frequency is almost zero.;)

mm43

[TheShadow]

Chris Scott said:
There seems to have been wide agreement here for a day or two that − in level flight, right at the beginning of this AF447 event − whichever ASIs were showing erroneous readings are more likely to have been over-reading the actual IAS/CAS, than under-reading it. Thus, if the crew were misled by the false readings, they might have slowed the aeroplane into a stall near the cruise altitude.
I can understand that, in the absence of auto-throttles, that a progressively ice-accumulating pitot head would cause an “indicated” airspeed drop-off – and that the crew would be alerted and would be likely to intervene. Whether they’d interpret it as an actual loss of performance is another thing. With a subtle loss of indicated airspeed, the first inclination would be to start thinking engine icing and airframe ice excrescences gradually (and cumulatively) causing increased drag/perf loss.

However, with no disagreement (at least initially) between the three airspeed/mach indications, in an A330 the compensating autothrottles would simply incrementally pump more go-juice into the equation to maintain the stipulated cruise speed….. would they not? If the pilots had their fuel schematic (instead of engine parameters) up on the screen (often the case I believe, when fuel may be tight, especially in an A330) and with the non-moving Airbus throttles, this minor increase in fuel flow/decreased AoA and slightly lower pitch attitude would probably go unnoticed. That’s the nature of an insidious event such as symmetric ice crystal accumulation in three Thales pitot heads…… until the displayed airspeed split becomes significant enough to trigger a “disagree”. If they were at FL350 in layered CirroCU and CS, it’s not likely to have been more than pebbly turbulent along their radar-chosen best course between build-ups – so they’d have not been “on the qui vive” and expecting trouble (aka settled into mind-numbing cruise ennui, if you will).

The end result (see Belgique pg61/post #1208 at link (http://www.pprune.org/rumours-news/395105-af-447-search-resume-post5718186.html?highlight=Belgique#post5718071)) of this quietly sinister acceleration would eventually be an aircraft headed, quite non-apparently, towards a Mach crit encounter. At, or even just prior to that juncture, either an airspeed disagree, pitch-trim disparity or (credibly) a mach-induced pitch-down may have caused the autopilot to click out – and then the crew would’ve been in a world of hurt as far as suddenly ascertaining what was what amongst their confusing displayed performance criteria. That’s a recipe for snap decisions, cross-cockpit misunderstandings and a “sucked-in” and fatally incorrect PF choice…… particularly in an environment where very few pilots have handflown a degraded law in a ‘Bus in IMC at night whilst trying to troubleshoot. Bedlam might be an adequate description of the scenario.

A pilot well-drilled in believing his instruments might have trusted the still credible airspeed display on his PFD and unwittingly had a (follow-up) Mach encounter with throttles placed fully forward. I’m not sure to what mach number an A330 would’ve been tested, but I know a few experimental test-pilots who have a healthy regard for flying beyond Mmo/Vne – because there “there be dragons”. It would be an easily achievable no-go area that can hold untold frights... in just this type of set-up. Airbus flight control protections are no longer in play when an aircraft is rolling, pitching and yawing as an aerodynamic direct result of a mach crit encounter. Having myself played those nose-low games in a quite robust jet trainer at great heights, I know that once you leave Mach country in total disarray and get below 20,000ft, things tend to sort themselves out. An airliner isn’t anywhere near as robust and could easily sustain significant structural damage in the first 5000 to 10,000ft plummet…. if the unusual attitude and pilot (or auto-trimmed to well out-of-trim) control response was extreme enough. Which brings me to the next query/point. What could induce a nose-down pitch into an Mmo encounter (which itself involves a reactionary nose-down pitching moment)?
.
During the quiet acceleration into/towards a mach crit encounter, what’s happening with the auto-trim and trimmable horizontal stabilizer (THS)? Is it getting conflicting inputs? (i.e. the computed trim-state from the ADIRU’s accepted and supposedly bona-fide indicated CAS airspeed - versus the actual dynamic pressures resulting from the actual airspeed). If the elevators were deflected and compensating to achieve an out-of-trim height-hold, what could’ve happened pitch-wise when the autopilot jumped out? Would the A330 autopilot have been opposing (i.e. holding) a nose-down pressure on its elevators due to undetected automation conflicts (or would it have been a pitch-up result at A/P disconnect?). Depends how the pitot/static data is being massaged into an autopilot interface - I guess.


We used to be able to declutch the autotrim in a PB20N autopilot and use the varicam trim (similar to THS) on the SP2H to squeeze a few extra knots (about 10 usually) for the cruise. It just achieved an “on the step” optimized attitude (was my diagnosis). It was a genuine increase validated by the navs, rather than an induced IAS position error). However if you forgot, and disengaged the autopilot without first removing the out-of-trim pressure being held by the elevators, you’d get a sudden nasty pitch-down – and some name-calling on the intercom. At coffin corner height in AF447, was this a likely contributing factor to a pursuant Loss of Control?

Any cogent input on the above suppositions?
.

[GobonaStick]

I see the DM has run a "truth of the crash revealed" article (http://www.dailymail.co.uk/news/article-1282367/Air-France-crash-The-truth-disaster-killed-228-people.html) ahead of the BBC programme. Says nothing new and looks like it came straight from a BBC press release. :hmm:

[HazelNuts39]

a progressively ice-accumulating pitot head would cause an “indicated” airspeed drop-off

I would think that with a progressively ice-accumulating pitot head nothing changes in the “indicated” airspeed until the pitot opening is almost completely closed, i.e. its opening is of the same order as the drain hole. After that, things happen fairly rapidly.

HN39

[Diversification]

By chance I found a Pitot Tube simulator on the internet. Using this you can block the drain port, etc, and study the effect. I don't know how accurate the simulation is, but the pitot tube is rather well described by bernoulli's eqn.
Try it. Here is a link:
luizmonteiro - Online Simulators - Pitot Static System Simulator (http://www.luizmonteiro.com/Learning_Pitot_Sim.aspx)
Perhaps it will make all agree to on what can happen.

[Doors to Automatic]

Apologies if this question has been asked before but does the technology not exist to transmit whatever goes to the two black boxes back to a server at head office as well?

I would imagine it is possible with today's technological advances and whilst black boxes could be retained as a back-up they would, in most instances, not be needed.

[vanHorck]

Hi Doors to Automatic,

It has been discussed heavily on this thread. You will find postings on the subject when using the Search utility at the top of this page.

It will include information about available technology as well as limitations due to bandwidth and much more

Good luck!

:ok:

[Capetonian]

On TV this Sunday there is a program that will interest you if you are in the UK.

LOST: THE MYSTERY OF FLIGHT 447

BBC2 at 10pm.

Should be worth watching. And you don't have to be in UK to get BBC2!

[bearfoil]

mm43

The Spoiler shown in your picture shows a typical air failure. The Spoiler, when deployed, especially in full, is a powerful lever. The force of the airstream is greatest at the trailing edge. When overloaded, the Spoiler uproots its hinges and "rolls" over its actuator, displaying its underside to the slipstream, hence the apparent upward failure.

BEA has also found that the flaps were stowed, protecting the underside of the spoiler from upward removal.

What interests me are the holes in the airside of the device. Clearly, the surface has been holed in at least three places. Nothing resembling a water flop would produce those high speed holes. My guess is that the spoiler was deployed to lose speed, but something parted the airframe ahead of it and blew those holes in it.

I would further state (guess) that the culprit may have been the Radome, having parted the nose in overspeed. If the Spoiler on the ship is the same one in the Sea, the evidence may remain, there appear to be no 'exit wounds' on the underside. If we're lucky, matching the projectile to the hole might roughly predict the two different airspeeds, instant.

bear

[BOAC]

i.e. the computed trim-state from the ADIRU’s accepted and supposedly bona-fide indicated CAS airspeed - how is this CAS derived?

[sensor_validation]

By chance I found a Pitot Tube simulator on the internet. Using this you can block the drain port, etc, and study the effect. I don't know how accurate the simulation is, but the pitot tube is rather well described by bernoulli's eqn.
Try it. Here is a link:
luizmonteiro - Online Simulators - Pitot Static System Simulator (http://www.luizmonteiro.com/Learning_Pitot_Sim.aspx)
Perhaps it will make all agree to on what can happen.

It doesn't simulate above 20,000ft or 220knots as far as I can tell.

At alts/speeds in its range it doesn't seem to model the small over-read due to the drain blockage, but this is likely to be specific to the particular design of probe. The model includes drain because if both ram plus drain blocked the total pressure is locked in and indicated speed just becomes function of altitude.

The AA probe was originally introduced to fix unreliable measurements, the critical period of flight is during climb after take-off, blocked drain+ram = false indicated speed increasing with increasing altitude, during which period pitot tube heater failure has been fatal. This model can be used to see how this can happen.

I believe there is a possibility of 3 identical probes in same airstream could suffer common mode fault of slowly blocking drains at same time. With auto-thrust the indicated air speed would not be seen to rise if all drains blocked - just true air-speed would fall (by small unquantified amount). Calculated wind speed would rise and engine thrust would be reduced. Would 30-50 knots be an issue?

At 02:10 there was an ACARS report

PROBE-PITOT 1X2 / 2X3 / 1X3

Which requires, for example one working correctly, one blocked ram+drain (stuck), one blocked ram (drain open =read zero).

So any false speed readings were just before this point, and have only an impact on the state of the a/c when the auto control gave up.

[ARFOR]

bearfoil

Yep, put the trailing edge front on to high speed air flow. Barn doors are not designed to withstand airflow from behind [swept wing roll without VS, flick, yaw, all over red rover]. The only way that could happen is loss of the VS following assem upset at alt. :uhoh:

What precipitated the loss of the lateral control [the VS] is any ones guess [Takata will chime in i'll guess].

[good spark]

bear
not sure about your ideas with the spoiler panel, i think if the spoiler was overloaded the actuator would have burst through the panel rather than acted as a pivot for the panel to rotate over itself.


gs

[bearfoil]

goodspark

The actuator takes all the spoiler's load, and is engineered accordingly. Note how the corners of the spoiler are broken downward, and the spoiler itself has folded in on itself longitudinally, ('around' the actuator, which is missing). This collapse is patent in overload, it is likely the actuator was 'pulled' out of its bed in the spoiler, as the spoiler left the a/c. Note the missing structure, roughly the shape of the join: actuator/spoiler.

The "Feathering" of the composite is typical of a spread-load failure, as opposed to focal collapse. This spread load can be related to either Air or SeaWater. the reason I choose Air Stream failure is that I would expect Water to have completely destroyed this panel at entry speeds entertained by BEA (ie above 100 knots.)

Composite, as opposed to Aluminum, has an instantaneous load/memory. It doesn't last long, but long enough such that the stress, if built up 'slowly' will instantaneously communicate with the whole panel at the failure point, causing a generalized rupture, instead of 'tearing', in the case of metallic sheets, or even laminates.

bear

[Chris Scott]

Quote from mm43 (post (http://www.pprune.org/rumours-news/395105-af-447-search-resume-63.html#post5721437) #1250):
"My understanding is that the outer spoilers can only be deployed following both MLG on the deck when landing or in a RTO above 72KT. Both outer spoilers are not used for speed brake or roll."

It's tough to keep up with the fascinating mm43/bearfoil dialogue (!) but, just for the record, Spoilers 1 are the inboards, and are the pair that are used only as Ground Spoilers (lift-dumpers). Spoilers 6 (the extreme outers) are used for roll. Perhaps someone with the Tech Manual can confirm that they (6) are also used as Speed Brakes?

Chris

PS (Edited addition)
The phrase now coloured pale orange has since been shown to be incorrect. See CONF_iture post (http://www.pprune.org/rumours-news/395105-af-447-search-resume-64.html#post5723072) #1273.

[CONF iture]

FCOM :

The speedbrakes involve spoilers 1 to 6.
Spoilers 1 to 6 act as ground spoilers.
Roll control is achieved by 2 ailerons and spoilers 2 to 6 on each wing.

[mm43]

Bearfoil; CONF iture;

I confused my "inners" and "outers", and thanks CONF iture for alerting me to an error in the Andy Tracy doc. Will let him know.

For the record, the spoiler arrangement and numbering are as follows:-

http://i47.tinypic.com/34reiy8.jpg

There still seems to be universal disagreement as to the cause of the spoiler detachment, though I am personally in favour of the BEA's version, as visible breakage of the spar attachments point to a high unidirectional force, which I don't see being as a result of an overspeed event. The usual proviso - I may well be wrong. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/sowee.gif

Bearfoil; Apologies, my original supposition regarding the non deployment of the "outer" spoiler was wrong. However, the top surface of the spoiler could have been impacted with shrapnel from anywhere at time of impact.

mm43

[Chris Scott]

Quote from CONF_iture:
"FCOM :
· The speedbrakes involve spoilers 1 to 6.
· Spoilers 1 to 6 act as ground spoilers.
· Roll control is achieved by 2 ailerons and spoilers 2 to 6 on each wing."
[unquote]

Salut Confit,

I see that the FCOM says Spoilers 1 act as Speedbrakes as well as Ground Spoilers. Am surprised for two reasons:
(1) The schematic posted above by mm43 appears to exclude them;
(2) They are much bigger surfaces than the others, as per A320 (which only uses them as Ground Spoilers).
Not sure if this effects the damage argument, but can you confirm from your own knowledge that the FCOM text quoted is not a misprint?

Chris

[CONF iture]

Chris,
I was a bit surprised too, but the text is supported by the following schematic :

http://i65.servimg.com/u/f65/11/75/17/84/af447_10.gif (http://www.servimg.com/image_preview.php?i=58&u=11751784)

According to the FCOM, in their speedbrake function, the maximum deflection for spoilers 1 is limited to 25 degrees, and that limit is 30 degrees for spoilers 2 to 6.

[mm43]

Chris Scott; Conf iture;

Strange that there appears to be a discrepancy, but a diagram I have indicates that the No.1 spoilers are for ground use only.

http://i45.tinypic.com/seuecl.jpg

I'm not sure of the actual source, but will try and find it.

EDIT :: Here it is:-

Electrical Flight Controls, From Airbus A320/330/340 to Future Military Transport Aircraft:
A Family of Fault-Tolerant Systems

by

Dominique Briere
Aerospatiale
Christian Favre
Aerospatiale
Pascal Traverse
Aerospatiale

The Avionics Handbook (http://www.davi.ws/avionics/TheAvionicsHandbook_Cap_12.pdf)

mm43

[HarryMann]

Nothing resembling a water flop would produce those high speed holes.

What pray, is a high speed hole?
Or even a high-speed hole...

Please forgive me, if I cannot force myself to be more credulous :rolleyes:

[CONF iture]

mm43,
Unless you see something I don't, but to me both diagrams are pretty similar :
Spoilers 1 are controlled by the PRIM3 computer and powered by the Green hydraulic system. They are used as GROUND LIFT DUMPER as well as SPEEDBRAKES.

[bearfoil]

mm43

The diagram includes all twelve spoilers for both Ground and Speedbrake does it not?

Is your original schematic for Direct Law? (Roll Only) ?

[mm43]

CONF iture;
Unless you see something I don't, but to me both diagrams are pretty similar You are right, they are the same. Spoilers 1 - 6 are both ground and speed brake, roll spoilers are 2 - 6, and more clearly marked in the second schematic. I would say the Aerospatiale guys used the Airbus schematic as the basis for the one they produced.

Bearfoil;
Is your original schematic for Direct Law? (Roll Only) ? Wasn't intended to be. But regarding the spoilers, it would appear that if 3 ADR fail, or VS1g computations fail, then there is no overspeed protection in Alternate Law, and side-stick input to spoilers in roll situation is direct and bank protections are lost.

EDIT :: As the flaps were stowed on impact, it is possible that they lifted cleanly upwards and took the spoilers out with them.

Oh yeah! I've put a red "strike-through" line through the reference to No1 spoilers not being used in the speed brake function in the A340 - A330 Control: Flight Laws (http://countjustonce.com/a330/a330-flight-laws.html)

mm43

[Chris Scott]

Thanks, CONF_iture and mm43, for the schematics.

Yes, they both confirm that Spoilers 1 perform as Speedbrakes as well as Ground Spoilers − clearly disproving my contrary suggestion. Sorry if I put the cat among the pigeons, but we now have some useful extra material to refer to. (In the cockpit, if selected, the F/CTL page of ECAM would clearly show this during Speedbrake operation.) It seems the air-braking capability of this A330/340 wing is quite powerful.

Chris

[henra]

Bearfoil,

the flipping over of the Spoiler is an interesting theory.
However, in that case I would expect upward bending / buckling of the trailing edge.
You would neet a fixed point around which the spoiler would create a lever to tear off the actuator. That would have to be the trailing edge.
Hiowever in the pictures, the trailing edge looks pristine compared to the rest of the device.

[takata]

Hello,
bearfoil
Yep, put the trailing edge front on to high speed air flow. Barn doors are not designed to withstand airflow from behind [swept wing roll without VS, flick, yaw, all over red rover]. The only way that could happen is loss of the VS following assem upset at alt. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/worry.gif
What precipitated the loss of the lateral control [the VS] is any ones guess [Takata will chime in i'll guess].
What precipitated the loss of the lateral control [the VS] seems to be impact with water.
At least, there is no clue that it happened between 02.10 and 02.14. Such a loss would trigger critical Hydraulics faults and all the relevant ACARS are missing. As none were received, it may be reasonably pointed that VS was not separated or badly damaged until ACARS stopped.
What happened later is still unknown but in flight separation would have certainly caused another kind of impact that what the investigation described. Now, one may want to be convinced that the BEA is bullying everybody but it would have to be done in collusion with NTSB and other bureaus working with it.
S~
Olivier

[bearfoil]

henra

The trailing edges are in no way pristine. They (corners) have failed down, the entire trailing edge has folded backward (from overloading), and the leading edge has failed from the middle (as a result of the hinges popping loose. At this point, all the airstream needs is a "peek" underneath, and the game is over The airflow is directed under the popped leading eedge, and fills the unprotected bottom surface with extremely energetic air. Meanwhile, the spill from the trailing edge has gotten mixed with other symmetrical spill and creates a local tornado of randomly blended vortices.

It is this folding of the panel back that precipitates failure, as it puts an enormous load on the center hinges, those in front of the actuator. The next stage is a rocking back and forth of the panel alternately loading either trailing corner. It is this undesigned for load that attacks the unengineered for weaknesses of the a/c that push the otherwise capable airframe into uncharted regions. Using an additional actuator might be one approach; bear in mind, this a/c is capable for all use as intended, it is not some exotic fighter that carries a single occupant. Aviation has categories and the 330 is a well made machine.

I think it is clear that the spoilers were deployed, and that some air loads were beyond design. As for the Flaps, they are inordinately robust as designed, but they were not meant to be a stand-in Hull for a water landing.I do think they separated, however, and if the Spoilers did not shear off in flight, they may well have been taken off with the Trailing edge of the wings.

takata

bonjour. I think no one is bullying anyone. A different point of view is not aggression. ACARS had one message left to send, as we know, there is that delay in transmission. You speak of loss of Lateral control, but all that has been shown is Lateral failure of the VS mounts. When the mounts broke and when or if the VS was lost in flight has not been established. Just as the spoilers were deployed as a result of some effort to gain stable flight, (an opinion), the VS may have stayed on.

It also may have separated. I have a theory as to what occurred, and it is based on what is publicly known.

I do know what happens to control surfaces when their mounts are broken. After mount failure, there is a lack of direct response, and depending on circumstances, control is compromised in vibration, loss of rigidity, and ever increasing play. It is this play that needs to be handled with great care. Just as more control is desired, there is degraded performance, and the temptation is to regain the control provided by increasing input. It is a cycle that has befallen uncounted aircraft

au demain,

bear

[Mr Optimistic]

If the aircraft impacted the sea more or less wings level with significant downward speed, is it that clear how the wing structure would respond dynamically (flexing) and the consequential loads that would have been imparted to the spoiler, actuator and supporting structures ? Add in a bit of roll with one wing impacting first and the analysis gets even more complex. Think I'd want an FE model before I tried to assess the remains.

[kijangnim]

Greetings
What about the Engines, dont you think they will touch the water first and subsequently take the maximum load :confused:

[Fargoo]

Program on BBC 2 now in the UK if anyone is interested

"Lost : The mystery of Flight 447"

[Kalium Chloride]

First thing they're doing on the BBC programme is eliminating the possibility of in-flight break-up.

Did the production team read the interim reports? Would have saved them the effort.

[kilomikedelta]

For the "creative" team doing the "production", facts are irrelevant. It's audience and sponsor appeal that supports their lifestyle.

[Kalium Chloride]

So...nothing new, then.

Just a recap of the same theories. I like the way the in-house investigation 'discovered' things which the BEA publicly listed months ago.

[Basil]

"Our independent team believes . . . ."
May as well believe most of you lot :) :ok:

[mm43]

Bearfoil;

I found another image showing the topside of the spoiler. It clearly shows that the damage caused was puncture pressure from the underside. Note the neat rows of holes where the actuator attachment pad bolts have been dragged through. The other damage is self explanatory.

http://i47.tinypic.com/2yl19tw.jpg

However, when referring to the BEA Interim Report, the caption associated with their published image - see Post #1253 (http://www.pprune.org/rumours-news/395105-af-447-search-resume-63.html#post5721609) doesn't make sense. It says, "Lower surface of left-hand spoiler No.1, with a piece of the fitting attaching spoiler No.5 to the wing aft spar: failures due to the bottom upward loads on the spoiler".

From my perspective, if it was the right-hand spoiler No.6, then "with a piece of fitting attaching spoiler No.5 to the wing aft spar" would make sense. Any comments?

Starboard Nos.2 and 3 in ground mode, showing fittings.

http://i45.tinypic.com/5bqmaf.jpg

mm43

[Propellerhead]

I'd like to congratulate the bbc for a very good program. The media rightly comes in for a lot of stick on this forum for sensationalist rubbish it normally produces but this was well researched, accurate and non sensationalist. As some say maybe not ground breaking news but the general public probably haven't read the bea's report.

Yet again, it seems that basic flying skills were not sufficient to mitigate an accident on a highly automated aircraft after a series of failures - failure to avoid the storm and failure of the pitot static heat to keep the probes de-iced.

[angelorange]

Yes much has been said before and by the expert reports. However, their mention of previous Pitot failure incident reports and how some other A330/340 crews took up to 60 secs to apply the 5 deg pitch and greater manual thrust (point and power) technique is still quite astonishing.

[eugenefraxby]

I agree - the documentary was unremarkable, but welcomely unsensationalist.

One thing I find truly remarkable was the chief pilot's statement that transport pilots nowadays don't undergo stall training. Can anyone confirm this?

I find it quite incredible. As a student glider pilot, I have to do stall and spin recovery training, learning to recognize the symptoms and recovery procedures for both. To me it seems like a very important component of core flying skills, and I'd be really surprised if transport pilots don't do this.

[sensor_validation]

The Beeb experts seemed to say Speed would have been reduced from M0.82 to M0.76 and then be only 10knots above stall speed?

They also blamed super-cooled liquid for pitot freezing.

Back on thread they also reckoned stall from high level, near recovery, then low altitude stall - which would suggest the search has been too far North?

[mm43]

... they also reckoned stall from high level, near recovery, then low altitude stall - which would suggest the search has been too far North?
But then we have recent news reports in which the BEA have been attributed with saying, "AF447 never went south".

Someone must be wrong! http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/sowee.gif

mm43

[bearfoil]

mm43

This looks definitely like a different spoiler than the one in the sea (your image post #1253). I agree wholly that the caption must be in error relative to the outer. It matches number one with number five, (?).

I must say this spoiler exhibits a failure consonant with a great load from underneath, but it also shows that the TL and LE have failed upwards. This is not what is seen with the other spoiler. It may be that the panel is so trashed that its edges articulate in both directions; note it is not leaning against the ship's cabin here.

Thank you for your reply, I think this may lead into a more prolonged assessment, I hope you will stay with us, your work is exemplary, and much appreciated. The landing photos are supreme, they give an excellent view of the strength and the vulnerability of the spoilers . I agree the fasteners remained with the mounting bed, pulled through as the panel left under great duress. A large fracture is seen on the outer edge of the mount, the energy was most profound. This discussion is most instructive on the strengths/weaknesses of materials.

be well

bear

[Chris Scott]

The theory the producers chose to go for was roughly as follows.

A US meteorology specialist suggests that the main line of Cbs might have been behind, and in the wx-radar shadow of a relatively moderate shower... Thus, having successfully avoided/penetrated the first shower, the crew is unprepared for the severe line of wx just beyond it.

Here a UK-based Airbus training pilot (Capt Martin Alder), and an American ex-Airbus captain/safety analyst take up the story. Belatedly realising the problem, the crew select turbulence-penetration Mach (stated to be M0.76 − that's good for an A320 but I don't have a figure for the A330). The current speed being M0.82, the A/THR reduces the N1 (thrust) considerably for the deceleration. Entering the wx, the A/C encounters super-cooled rain at –40C. Pitots freeze, leading A/THR to disengage at a very low thrust setting, as A/C still slowing down. Pilots slow to take throttles out of CLB gate, so thrust does not increase in time to stop the A/C stalling. Their presumed failure to establish a Thrust/Attitude technique is partly due to non-driven throttle levers (lack of tactile cues).
Situation allegedly exacerbated by: (1) too much reliance by today's airline pilots on AP and other automation; (2) absence of stall-training (meaning as part of type-rating?); (3) plethora of warnings causing excessive work load. A/C may have recovered from first stall with wing-drop, but − if so − probably stalled again.

Little acknowledgement by the producers of the fact that nearly all the aircraft data and photos used must have originated from the BEA and Air France. Knowing Martin, I doubt he would have gone firm on one theory, to the exclusion of others. But, as these shows go, it was a pleasant surprise. The sim. footage was clear, relevant, and fairly well in context with the theory (which has some merit).

In haste (prior to travel),
Chris

[silverline001]

Nearly a year later,more questions than answers.Just saw again the section of the aft galley(correct me if wrong) and sorry could not paste the link but i`m sure many of you had already seen it ,which seems very intact and also the vertical stabilizer + rudder.Still leaves me baffled if the plane really disintegrated in the air or not.What are the chances of such two parts of an airplane remaining nearly intact after such a massive G load impact.....would it be a airborne disintegration or a particular angle of impact on the water,that would lead parts of an aircraft no to be severely distorted ,let alone mainly intact in composition.Remember that the initial impacting on water at such high speeds is like impacting on solid rock,no difference.Would love to hear your views.

[mm43]

Bearfoil;
This looks definitely like a different spoiler than the one in the sea (your image post #1253 (http://www.pprune.org/rumours-news/395105-af-447-search-resume-63.html#post5721609)).All the photographs in post #1253 (http://www.pprune.org/rumours-news/395105-af-447-search-resume-63.html#post5721609) and post #1290 (http://www.pprune.org/rumours-news/395105-af-447-search-resume-65.html#post5724646), including that in the BEA's Interim Report are all of the same spoiler. Check all the pics carefully and the damage and tell-tale marks all match.

Other than the BEA photograph, all the other images were supplied directly to me from the ship which picked the spoiler up. My only problem is establishing exactly what spoiler it is, as my initial impression was that it was the Starboard Outer, and I had recorded that in some graphics posted to the AF447 thread many moons ago. The BEA have since confused the issue with their caption.

mm43

[mm43]

Chris Scott;
Belatedly realising the problem, the crew select turbulence-penetration Mach (stated to be M0.76 − that's good for an A320 but I don't have a figure for the A330).The Airbus recommended turbulence penetration speed for the A330-200 at FL350 is M0.80 in ISA conditions; TAT -54.1°C. The forecast temp at FL350 was -46°C and probably rose considerably, so the -40C they mentioned was still a bit "low"!

mm43

[takata]

Hello,
The Airbus recommended turbulence penetration speed for the A330-200 at FL350 is M0.80 in ISA conditions;
Added to that both Airbus/Air France recommended turbulence penetration mode is Autothrottles OFF while AF447 A/T was kicked OFF by systems at 02.10, consequently, she was certainly not in turbulence penetration mode/speed until this point. Moreover, at 02.10, more than half of the CB system was already crossed, they were not just penetrating it.
S~
Olivier

[HazelNuts39]

she was certainly not in turbulence penetration mode/speed until this point
However, from BEA's 2nd report:
The RTLU was found in its place in the fin and disassembled. An examination
was performed at the manufacturer’s and showed that it would allow travel
of the rudder measured as 7.9° +/- 0.1°. As an example, at FL350, this travel is
obtained for Mach 0.8 +/- 0.004, corresponding to a CAS of 272 +/- 2 kt.HN39

[takata]

Hi HN39,
However, from BEA's 2nd report:
The RTLU was found in its place in the fin and disassembled. An examination
was performed at the manufacturer’s and showed that it would allow travel
of the rudder measured as 7.9° +/- 0.1°. As an example, at FL350, this travel is
obtained for Mach 0.8 +/- 0.004, corresponding to a CAS of 272 +/- 2 kt.You are right about its inferred speed, but it may be also due to other factors like weather avoidance as she was 3 nm west off track (going away or returning to flight plan). Nonetheless, ATHR engaged is possibly ruling out severe turbulences, IMHO.
S~
Olivier

[Mr Optimistic]

fair point but does it alter the point that dynamically the forces acting on any component at failure may not be as first motion ?

[HazelNuts39]

Chris Scott;

In your account of the BBC documentary on AF447:
Pilots slow to take throttles out of CLB gate, so thrust does not increase in time to stop the A/C stalling.I wonder, did they mention stall warning, and why it was ignored?

HN39

[Loose rivets]

The program gave a mini-course on supercooled water and pitot heads, but said little or nothing about airframe icing while encountering the phenomenon.

Severe icing from supercooled droplets can be astonishingly sudden, and flying an aircraft in turbulence, with the added burden of ice, could be one reason the crew had difficulty in staying inside the envelope.


I thought the program was quite good. It did have periods of the daft background noises that they seem to think makes things a tad more dramatic, but I noticed this was cut to zero when something important was being said.

I still find it hard to see why we're relying on Black Boxes. Given the amount of data being sent to 'Company', I can't help feeling that total monitoring could be done via satellite these days. While in America, I spend ages chatting to people on Skype. I share this with 20+ million people - many enjoying modest video. If this can be done as a give-away, surely something as important as crew well-being and aircraft integrity could be transmitted in real-time.

[takata]

Hello Bear,
bonjour. I think no one is bullying anyone. A different point of view is not aggression.
I dont feel aggressed but, I won't pick up each of your previous comment underlying that investigation is not credible or "is trying to suggest such and such scenario" which otherwise main weakness is that it doesn't fit yours. My opinion is that so far, no "scenario" was really pushed ahead by the BEA, only its findings about wreckages and flight conditions without regards if it will make sense or not.
ACARS had one message left to send, as we know, there is that delay in transmission.
I never read something about that. Reports are saying that all ACARS transmitted by AF447 were received.
You speak of loss of Lateral control, but all that has been shown is Lateral failure of the VS mounts. When the mounts broke and when or if the VS was lost in flight has not been established.
I used other poster's words, but so far, I have certainly read that it was established by investigators that the tail was not lost in flight neither any main part of the airframe.
Just as the spoilers were deployed as a result of some effort to gain stable flight, (an opinion), the VS may have stayed on. It also may have separated. I have a theory as to what occurred, and it is based on what is publicly known.
Obviously, it is still the exact same theory I'm reading from you, starting post crash. Whatever was found later about this flight, I'm not sure you'll be able to reconsider your point anyway.
S~
Olivier

[ushumgal]

I'm no aeronautical engineer, but is it perhaps possible that both theories - in-flight breakup and intact impact with the water - are partly true? Would it be possible for the aircraft to lose the VS and perhaps the HS and some control surfaces due to overspeed or excessive control inputs, and then enter some kind of stall or spin and impact the water in the manner suggested by the report (high vertical speed, but not so high as to completely disintegrate everything)? Or would losing the VS at altitude inevitably lead to an in-flight breakup?

I still find it hard to see why we're relying on Black Boxes. Given the amount of data being sent to 'Company', I can't help feeling that total monitoring could be done via satellite these days. While in America, I spend ages chatting to people on Skype. I share this with 20+ million people - many enjoying modest video. If this can be done as a give-away, surely something as important as crew well-being and aircraft integrity could be transmitted in real-time.The ACARS messages are actually extremely small in terms of data transmitted. This issue has been discussed elsewhere on this thread and the original AF447 thread. It boils down to this: with the existing infrastructure, it is not feasible to transmit the amount of data necessary to make a continuous recording of the flight parameters recorded by the FDR, still less to stream the multiple audio tracks from the CVR. It is not so much a matter of installing new technology into the airplanes, but of how to transmit the data, which would perhaps require new satellites and other very expensive bits of infrastructure.

Plus, pilots may object to the possibility of being micromanaged from the ground even as they fly, if all that data is being sent in real time to the home office.

[Hyperveloce]

Doesn't it seem unlikely that any major control surface failed during a possible overspeed given the conditions of impact ("en ligne de vol", no roll, no yaw, no sideslip, slight nose up) described in the BEA reports ?
If we assume a high altitude upset (which I do), we have to explain why the recovery from cruise altitude has not been possible... and despite this, why the A/C impacted the surface with a terminal velocity mostly vertical (contradictory with a recovery about to be successfull), but not as high as in previous cases of high dive from cruise altitude. Doesn't the possibility raised by the BBC documentary (overcorrection in the recovery at low altitude, possible in the absence of alpha prot and low speed stability => secondary stall at low altitude) have the potential to explain both of these aspects ?
Jeff

[Diversification]

I have read the following in the A330-340 Flight Crew Training manual (perhaps not the latest version?)
"Triple IRS or ADR failure is very unlikely and is not displayed on the ECAM. Should a triple failure occur, two double failures would be displayed, i.e. ADR 1 + 2 FAULT and ADR 2 + 3 FAULT. The subsequent ECAM actions would give conflicting instructions. In this case, apply the QRH procedure for ADR 1 + 2 + 3 failure. This is one of the few cases where the crew will not follow the ECAM procedure."
So the crew is left with conflicting info and have to find the proper document BEFORE they act.

When it comes to the software and hardware used on AF447, the BEA reports are very silent. Why give details about engines and some other hardware, but noting about the FBW-system? E.g. the QF72 accident report made by Australians contain a lot of such inf.

Now I am awaiting the flogging.

[kijangnim]

Greetings
Mr Optimistic I have great difficulties understanding your sentence :confused:, can you please be kind enough to elaborate a bit more :ok:

There is a VDO about the B767 Ethiopian ditching look at it to see the effect the engines have when ditching. :eek:

[wilyflier]

Can any one equate the design strength of the VS with the max possible deceleration "G" in any sort of flat ditching, and the forward "G" required to permit a fin and rudder to rip clean off its fittings?

[takata]

Hi,
I have read the following in the A330-340 Flight Crew Training manual (perhaps not the latest version?)
"Triple IRS or ADR failure is very unlikely and is not displayed on the ECAM. Should a triple failure occur, two double failures would be displayed, i.e. ADR 1 + 2 FAULT and ADR 2 + 3 FAULT. The subsequent ECAM actions would give conflicting instructions. In this case, apply the QRH procedure for ADR 1 + 2 + 3 failure. This is one of the few cases where the crew will not follow the ECAM procedure."
So the crew is left with conflicting info and have to find the proper document BEFORE they act.
Well, ADR 1+2+3 FAULT is memory item (ADR DISAGREE). Then, just apply it.
When it comes to the software and hardware used on AF447, the BEA reports are very silent. Why give details about engines and some other hardware, but noting about the FBW-system? E.g. the QF72 accident report made by Australians contain a lot of such inf.BEA's reports are only "interim" dealing with partial findings while final report will certainly deal with that in details if something relevant is to be said about it.
S~
Olivier

[takata]

There is a VDO about the B767 Ethiopian ditching look at it to see the effect the engines have when ditching.
There is also many videos about Hudson's ditching showing that engines, when they hit water with wings level - contrary to this B767 case, are absorbing a lot of forward energy without breaking up the airframe.

From my understanding, in AF447 case, vertical speed would have to be much higher to break it up and for causing so much compression into the lower part of the airframe (including tailfin separation, rudder damages, killing passengers, etc.).

I'm not quite sure actually how to represent accuratelly this kind of impact (a kind of slow flat spin, wings level and tail down? or with high sinking rate, first hit with tail, nose high, killing forward speed then pankaking?)... low end rudder damages are quite serious, possibly caused by tailcone's failure at impact with water. I'm waiting for the BEA's video to figure it out one day.
S~
Olivier

[kijangnim]

Greetings TAKATA

Huge difference between choosing to ditch and preparing the Aircraft with the right configuration speed and attitude and falling from the sky ......:}

[mm43]

Hello,
Takata;

In a reply to Bearfoil you wrote:-I never read something about that. Reports are saying that all ACARS transmitted by AF447 were received.I think that Bear is referring to the following detail from page 36 (English version) of the BEA Interim Report No.2. The PRIM 1 and SEC 1 faults below are possibilities, but the MAINTENANCE STATUS ADR2 would have been sent (if possible to do so).

F/CTL PRIM 1 FAULT (2 h 13)
This message indicates that FCPC1 (PRIM 1) has stopped functioning. This shutdown may have been commanded or be the result of a failure. In the absence of an associated fault message, it is not possible to command a shutdown. However, a fault message that had not had sufficient time to be transmitted can not be excluded. Indeed, this message was received at 2 h 13 min 45 and the last message at 2 h 14 min 26, whereas the fault message could have appeared up until 2 h 14 min 45.

F/CTL SEC 1 FAULT (2 h 13)
This message indicates that FCSC1 (SEC 1) has stopped functioning. This shutdown may have been commanded or be the result of a failure. In the absence of an associated fault message, it is not possible to command a shutdown. However, a fault message that had not had sufficient time to be transmitted can not be excluded. Indeed, this message was received at2 h 13 min 51 and the last message at 2 h 14 min 26, whereas the fault message could have appeared up until 2 h 14 min 51.

MAINTENANCE STATUS ADR2 (2 h 14)
This message was received at 2 h 14 min 14 and a class 2 fault message should have been received between 2 h 15 min 00 and 2 h 15 min 14.

mm43

[bearfoil]

PM1:

"Monsieur, the turbulences are increasing rapidly, what will you do?"

PM2: "I will wait until the auto pilot has had enough and cannot keep to its design limits, then we can catch the controls as they fall into our lap."

PM1: "Oui"

Of course NOT. The pilots were startled at dropout of Auto flight.

What caused the Trip? Was it a roll beyond 45 degrees? Had 447 sliced into a monster up elevator with the tip and then the rest of one wing? What is the definition of the "edge" of vertical development? Had she then recovered level flight upon complete entry into the vertical wind tunnel? Did the pilots reduce a/s to book penetration velocity? At lower mach, did she climb with the monster to 37, 38?

Did she then exit the vertical column into the monster's twin, the down cycle?
At reduced speed, heavy weight, and an AoA adjusted to the climb, did she break?

In the ensuing dive did she pick up sufficient velocity to reach a/s far in excess of critical? Down into thicker air, did the break take her vertical, or past it? This is all a possibility if the weather was dramatic enough. How many more times did she stall, partially recover, then break even deeper?

To me, it is the first transmission of ACARS that may have sealed 447's fate. Upset? By definition, of course. Stall? Certainly.

ICE? What if Ice wasn't involved? What do the pitots and ADIRU do with shear?
Does the computer know the difference between Unreliable AirSpeed and Discrepant readings that mimic it? Better question: had the computer been 'taught' the difference? Is sufficient Yaw possible in recovering from overbanking that engines and pitot(s) can be blanked? Long enough to cause Computer Fault/Fail?

bear (IMO) OTR for now, someone please save my seat.

[RetiredF4]

Can anybody explain the reasons for the ongoing discussion about the possibility of an inflight breakup or a partial inflight breakup?

BEA was in most parts of the tragic events very common, in the part of impact with the water and the probable condition of the hull prior impact very specific. The result had its origin in the found pieces of wreckage and most probably some experts looking at those in person and detail (despite us looking only at pictures) came to strong results, leading to the statement of BEA.

So what is the real sense in turning this result over and over? Would it not be better to accept it for the moment until other information tells otherwise and go on from that point?

franzl

[bearfoil]

Retired F4

My last post mentions nothing of any disintegration or even a dropped gerkin fork.
It could easily have ended as BEA would have it. Without questions, the temptation is to let others think for us. As you say, BEA makes no conclusions. why not challenge each other with possibilities. I know, wait for the final report.

I'm going Phishing, Phor Phlounder.

bear

[RetiredF4]

@ bearfoil

sorry, my post didn´t adress you or your last post (we probably wrote them same time) at all, it was more a common question in view of recent posts.

franzl

[TiiberiusKirk]

I wonder, did they mention stall warning, and why it was ignored?

HN39What generates a stall warning? Is it low air-speed detected?

If so, the pitot tubes were already declared unreliable.

With the computers deciding the pitot tubes were malfunctioning (unreliable air-speed)
would they immediately trigger as stall warn just in case, or suppress the stall warning because they're 'not sure'?

TK

[HazelNuts39]

TiberiusKirk;
I was asking about the content of a BBC program that I was unable to see.

What generates a stall warning? Is it low air-speed detected?

From BEA's 2nd report:
In alternate or direct law, the angle-of-attack protections are no longer available but a stall warning is triggered when the greatest of the valid angle-of-attack values exceeds a certain threshold. In clean configuration, this threshold depends, in particular, on the Mach value in such a way that it decreases when the Mach increases. It is the highest of the valid Mach values that is used to determine the threshold. If none of the three Mach values is valid, a Mach value close to zero is used. For example, it is of the order of 10° at Mach 0.3 and of 4° at Mach 0.8.The angle of attack is obtained from AoA vanes located on the nose of the airplane.

HN39

[tubby linton]

I would hazard a guess that the stall protection will be based on alpha provided by the AoA vanes to the Adirs.The QRH states that with a triple ADIRS failure stall warning is lost.The QRH continues by requiring use of the standby altimeter/ASI but if these are unreliable as well you are rapidly into unreliable airspeed territory which the x-list fails to mention!This x-list does appear next in the QRH.
The x-list for unreliable airspeed is quite long and initially requires a number of memory items.Pitch and power settings for level flight do not appear until the fourth page.
Did anybody else notice the sim in the BBC programme was an A320?

[sensor_validation]

...The angle of attack is obtained from AoA vanes located on the nose of the airplane.

HN39

which would also be frozen at altitude in the BBC super-cooled liquid storm?

Would still have pitch from gyros?

[Low Flier]

Attitude plus power equals performance.

Never forget the basics.

[mm43]

tubby linton;
Did anybody else notice the sim in the BBC programme was an A320?
Which explains why they stated the turbulence penetration speed was M0.78 instead of M0.80 in the A330.

mm43

[HarryMann]

Can any one equate the design strength of the VS with the max possible deceleration "G" in any sort of flat ditching, and the forward "G" required to permit a fin and rudder to rip clean off its fittings?The whole aircraft should basically hang together (as far as compromising the pax cabin) at 9g deceleration...

I have no idea though, what decel 'g' in a flat ditching situation would fail the fin as suggested by the BEA report... other than more than 3g

[infrequentflyer789]

In your account of the BBC documentary on AF447:
I wonder, did they mention stall warning, and why it was ignored?

HN39

Their scenario is that in turbulence penetration, thrust is reduced below required power for flying pitch+power in the event of unreliable airspeed. Lack of direct feedback from non-moving throttles was mentioned, together with the high workload + alarms (in general) leading to pilots being slow to appreciate that power is below that needed. They state that this is born out in previous unreliable airspeed incidents, where pilots took 60secs to set power.

No mention of stall warning specifically. I can imagine it would be quite easy to ignore stall warning if you already believe the plane doesn't have a clue how fast it's going anymore.


The BBC had limited time, to go into everything, particularly when trying to get in as much dramatic commentary as possible... :) They may well have filmed discussion on stall warning and then cut it.

There was very little on the VS also - basically taken as read the BEA conclusion that it was still attached at impact. There's probably enough material on the VS on this thread to make an hours television just on that subject - however the interested audience would then be a bit more limited! :8

Not a bad program at all (certainly not full of hype or innaccuracies), but equally it doesn't bring anything new if you've already read this thread (for instance).

[takata]

Hello mm43,


In a reply to Bearfoil you wrote:- Quote:
I never read something about that. Reports are saying that all ACARS transmitted by AF447 were received.
I think that Bear is referring to the following detail from page 36 (English version) of the BEA Interim Report No.2. The PRIM 1 and SEC 1 faults below are possibilities, but the MAINTENANCE STATUS ADR2 would have been sent (if possible to do so).

F/CTL PRIM 1 FAULT (2 h 13)
This message indicates that FCPC1 (PRIM 1) has stopped functioning. This shutdown may have been commanded or be the result of a failure. In the absence of an associated fault message, it is not possible to command a shutdown. However, a fault message that had not had sufficient time to be transmitted can not be excluded. Indeed, this message was received at 2 h 13 min 45 and the last message at 2 h 14 min 26, whereas the fault message could have appeared up until 2 h 14 min 45.

F/CTL SEC 1 FAULT (2 h 13)
This message indicates that FCSC1 (SEC 1) has stopped functioning. This shutdown may have been commanded or be the result of a failure. In the absence of an associated fault message, it is not possible to command a shutdown. However, a fault message that had not had sufficient time to be transmitted can not be excluded. Indeed, this message was received at2 h 13 min 51 and the last message at 2 h 14 min 26, whereas the fault message could have appeared up until 2 h 14 min 51.

MAINTENANCE STATUS ADR2 (2 h 14)
This message was received at 2 h 14 min 14 and a class 2 fault message should have been received between 2 h 15 min 00 and 2 h 15 min 14.
Right, I have seen this but it is a different matter that considering that other ACARS messages were actually sent and not received.

All cases discussed above are linked to ACARS sequences interrupted which relevant part missing were actually NOT sent by the systems but which fault msg had not reached their time limit before being possibly triggered. On the other hand, Hydraulics faults messages are completely missing and it is consequently possible to point out that no hydraulic fault occured between 02.10 and ~02.14. If one hydraulic fault ever occured without being tansmitted, it would be at the very very end when ACARS were shut down.

Then, if one want to explain an upset between 02.10-02.14 with problems triggering hydraulic faults, he should be able to explain why it would take 4, 3, 2 or 1 minute for such an ACARS to be sent and to verify if such a case is possible, which is not.

My point was that investigation pointed that all ACARS sent by AF447 were received. There was no imaginatory sent ACARS missing as Bearfoil was suggesting and possible delays for such hard fault are only in the order of few seconds.

S~
Olivier

[HazelNuts39]

The program gave a mini-course on supercooled water and pitot heads, but said little or nothing about airframe icing while encountering the phenomenon.
Severe icing from supercooled droplets can be astonishingly sudden, and flying an aircraft in turbulence, with the added burden of ice, could be one reason the crew had difficulty in staying inside the envelope.
From BEA report no.1: ... the presence of super cooled water at FL350 is not very probable and would necessarily have been limited to small quantities. I believe that the problem of icing due to supercooled water droplets is well known and understood for about half a century (refer to FAR 25 Appendix C). Airplanes, engines and pitots are designed, protected and extensively tested for safe operation in those conditions.

It seems that the relatively recent icing problem at high altitudes with pitots (and perhaps also engines) is not caused by liquid water but by fine ice particles which present no particular problem for the airframe. From BEA report no.2: Examination of reported UAS events in cruise has shown that the majority of them occurred outside of the envelope defined in Appendix C. In fact, the certification criteria are not representative of the conditions that are really encountered at high altitude, for example with regard to temperatures. In addition, it appears that some elements, such as the size of the ice crystals within cloud masses, are little known and that it is consequently difficult to evaluate the effect that they may have on some equipment, in particular the Pitot probes. In this context, the tests aimed at the validation of this equipment do not appear to be well-adapted to flights at high altitude. HN39

[aguadalte]

Although I am a hard defender of the need for commercial pilots to keep proficient and skilled in manual flying, it was sad to see that the "investigators" and "experts" interviewed by BBC, have passed to the general public, the idea that the Air France pilots were unable to recover from stall, because they were not trained (and not used to fly manually)...
To compare the ability of that military pilot, to recover from stall, without mentioning that there was a huge difference between doing it in a flight simulator, with available speed information, and trying to recover a stalled heavy bird without speed info, is intellectually dishonest. :=
That colonel has lost almost half of his altitude to recover from stall. I'd love to see him talking, after a couple of attempts in a heavy jet, with almost 5 tons of fuel in the trim tank and without proper speed read-outs, in turbulence and dark...

[aiman]

One thing that was never mentioned was the supposed location of the Captain, not on the flight deck !

[autothrottle]

Yes I noticed too, it was two first officers. Was that an intentional supposition?

[overthewing]

Humble SLF question here.

It's been suggested that digital displays are hard to read if everything is vibrating in extreme turbulence. If the conditions are that rough, how easy is it to actually get your fingers onto a button or dial to change settings?

Is it easier to have throttles to physically hold onto while you're trying to change engine settings, than tweak a smallish dial?

If these are dumb questions, I apologise. I'm just wondering if this kind of situation has been factored into Airbus design?

[Basil]

overthewing,

I think you have already guessed the correct answer.
Other than a short play in the simulator, I haven't flown the 'Bus but with Boeings, one would also normally make selections via the Mode Control Panel or Flight Management System keyboard.

In moderate turbulence, on occasion, I've had to use both hands to make selections, one to steady the other.
Turbulence also makes instrument interpretation a little more difficult.
IF those guys flew into a Cb then, clearly, things would be a deal worse than I've described.

Over my aviation career, even mechanical instruments became smaller in order to fit more onto a finite panel space. If I had to make a choice between 1980s mechanical instruments and a glass cockpit, I'd have to say that maintaining situational awareness is much easier with glass.

Perhaps someone with a few thousand hours on each of Airbus and Boeing could comment further. (or give the posting number if it's been mentioned already :O )

[bearfoil]

FBW. It is not "state of the art", it is old. Likewise, it is dependable. No authority would allow skimping on Stall Recovery training without unquestionable confidence in it. When I fly, I yank the straps tight, just short of pain. As a student, a defective seat rail slid me back full on take off. Luckily I am tall, and didn't need to squirm forward while flying solo at launch.

Throttle manipulation? Panel reads? Bouncing about when called upon to start reading a book through page four to find out life saving instructions isn't old, it is stupid. Likewise, when a specific throttle position is do or die, and you can't scratch your ass let alone smoothly caress the power, something is terribly wrong.

Look for Voice recognition commands to the controls in the future.

ACARS is a maintenance option, something to cut the costs for big carriers. It is not intended to substitute for FDR. It logs and sends information so the Mx crew at the next shop can prioritize their work and have a lead on important parts. Just because a message wasn't received certainly does not mean it was not sent. It takes the pilots out of the Mx equation as well, someone whose input will be included at the next stop.

I think the VS failed laterally while in flight, as a result of the fractures seen in the mountings in BEA's photography. This does NOT mean a failure of hydraulics, necessarily. My estimate of the lateral play in this control is 1-2 feet at the tip, post fracture. Obviously, if the VS failed flat (the photography does not show this), it would have been lost. So the cracks in the female bracket (tower) allow dangerous play, but suggest no loss (departure) of the VS/Rudder in flight. Some combination of lateral rods, remaining integrity of the lugs, and lack of overwhelming deflection argue that the VS was hobbled, not missing. At impact? Severely compromised lateral strength and a weakened bed may not have required much more than 2-3 g's for forward separation at water entry, (impact). A sharp pilot might read lack of crisp yaw control as a breaking or broken Stabilizer or Rudder, and laid off, or tried spoilers? Perhaps asym thrust for yaw control? Or was it RTLU at ~8 +/- ?

bear

[ChristiaanJ]

Look for Voice recognition commands to the controls in the future.Nice one, bear.
But I DO wonder how your system would respond to ...

"Oh, feckin hell... now why did it do THAT?"

"So sorry Sir, error 404" , maybe?

CJ

[bearfoil]

"......I can't do that, Dave......."

[MurphyWasRight]

Nice one, bear.
But I DO wonder how your system would respond to ...

"Oh, feckin hell... now why did it do THAT?"



Not to mention that voice recognition accuracy degrades when the speaker is stressed, otherwise known as the "important demo detector".

Interestingly enough the more technical and complicated the subject the better voice recognition performs, one of the first commercially succesfull aplicatiosn was medical notes.
Of course being better than doctors handwriting is not all that difficult.

[funfly]

The BBC program commented that with lack of airspeed information a setting of throttle to (75%) thrust and the elevator to (15) degrees would maintain safe speed.
(Forgive me if I have the figures wrong, someone give correct figures for airbus)
They claim that the crew should have set these parameters fairly quickly.

These settings are obviously right to MAINTAIN straight and level flight but would the same settings get an aircraft BACK to level flight from a near stalled or just after stalled position i.e. nose down and possibly accelerating?

[sb_sfo]

As it's one year to the day since this accident, I wonder if we'll be any closer to an answer in another year.

[mates rates]

Who in their right mind would build a aeroplane where the power changes without the visual cue to the pilots of the throttles moving in response to this power change ?

[jcjeant]

Hi,

Who in their right mind would build a aeroplaneAirbus Industrie.

[HazelNuts39]

Can any one equate the design strength of the VS with the max possible deceleration "G" in any sort of flat ditching, and the forward "G" required to permit a fin and rudder to rip clean off its fittings?

The max possible deceleration "G" in flat ditching is perhaps a separate question, with too many unknowns in the equation to expect a meaningful answer. Flat ditching refers only to attitude: almost wings level, right wing slightly down, some nose-up pitch. Other relevant factors are: high vertical speed, probably low horizontal speed although unlikely to be lower than stall speed (160 kt clean?), and the condition of the airplane immediately after the initial tail-down impact. If one assumes the fuselage broke aft of the wing (crew rest module floating on the surface), the drag of the rear fuselage in the water would have been high relative to its mass, easily resulting in decelerations of the order of 30 – 60 g, depending on the assumptions made.

Just a crude layman’s attempt to relate aerodynamics, structural strength, and crash deceleration:

Aerodynamic load. The area of the VT is estimated as 44 m^2, and the max. rudder angle is 35 degrees up to 150 kt CAS. Assuming cL=2, the sideforce on the vertical tail is 30 t.
Vertical loads on VS attachments. If the VS bending moment is distributed equally over the six attachments, each receives a vertical load of 44 t, tensile on one side, and compressive on the other.
Inertial load compatible with attachment strength. The forward inertia force results in a vertical pull force on the two aft attachments. A pull force of 2*44 t corresponds to 73 t at the c. of g. of the vertical tail surfaces. In his post #1116 (p.56) “cc45” gives the VT a mass of 1800 kg, resulting in an acceleration of 41 g.

Graphic: A ‘back-of-the-envelope’ sketch illustrating the above is available here:
https://docs.google.com/leaf?id=0B0CqniOzW0rjMTFhMTA4ODYtODNkNi00YjA2LTkyOGUtMjBjNjg wMmZhNDI4&hl=fr

[takata]

Hello Bear,
In summary, as nothing will change your point anyway, I'll consider that you are either a so damn good expert capable of dismissing field investigation work by looking at a couple of pictures and telling us they are totally incompetent about this matter, either that you are stretching all evidences in order to fit your pre-conceived theory already made before a single piece of this aircraft was actually recovered.

ACARS is a maintenance option, .. Just because a message wasn't received certainly does not mean it was not sent.
So, the BEA is obviously bullying us...

1.16.2.4.3. Interruption of the messages
The last ACARS message was received at 2 h 14 min 26. The traces of
the communications at the level of the satellite show that the ACARS
acknowledgement from the ground was effectively received by the aircraft.

No trace of any attempted communication by the aircraft with the ground was then recorded, although there was still at least one message to be transmitted
(see above). In absolute terms, there are several reasons that could explain
why communications stopped.

¤ no message to be transmitted: as explained above, the “MAINTENANCE
STATUS ADR2” message should have been followed, one minute later, by
the transmission of a class 2 fault message. The aircraft therefore had, at
2 h 15 min 14 at the latest, one message to be transmitted.

¤ loss of one or more system(s) essential for the generation and routing of
messages in the aircraft:
• ATSU / SDU / antenna: none of the maintenance messages sent is
related in any way whatsoever with the functioning of these systems. A
malfunction of this type should have occurred after the transmission of
the last message and without forewarning.
• loss of electrical power supply: this would imply the simultaneous loss of
the two main sources of electrical power generation.

¤ loss of satellite communication:
• loss of data during transmission: the satellite’s quality follow-up does
not show any malfunction in the time slot concerned.
• loss of contact between the aircraft and the satellite:
• • unusual attitudes: given the relative position of the satellite with respect to the aircraft and the aircraft’s tracking capability, the antenna would
have to be masked by the aircraft’s fuselage or wings. Examination of
the debris showed that the aircraft hit the water with a bank angle close
to zero and a positive pitch angle. The aircraft would therefore have
been able, in the last seconds at least, to transmit an ACARS message.
• • end of the flight between 2 h 14 min 26 and 2 h 15 min 14.
Investigation worked out aircraft-sattelite-ground communications. Its conclusion was not only based on what was received on the ground but on the whole protocole, including the fact that the last message received at 02.14.26 was duely aknowledged by the ground to the aircraft as being transmitted. ACARS can not transmit if the aircraft is not loged on the sattelite meaning that ACARS are not sent into thin air with hopes it will be picked up by chance (or not) by the communication system.


I think the VS failed laterally while in flight, as a result of the fractures seen in the mountings in BEA's photography. This does NOT mean a failure of hydraulics, necessarily.
Of course it doesn't!
Airbus is so dumb as it does not want to bother pilots/maintenance when some control surface is falling from the sky, like if they needed it for something...
And so, the BEA is still bullying us... Where are the evidences (so obvious) of lateral failures here:

1.12.3.5.2 General examination of the vertical stabilizer
The vertical stabilizer was in generally good condition. The damage observed
on the side panels and on the rudder was largely due to the recovery and
transport operations. The damage due to separation from the fuselage was
essentially located at the root of the vertical stabiliser.

The vertical stabilizer separated from the fuselage at the level of the three
attachments:
• the forward attachment (male and female lugs) and part of the leading
edge are missing;
• the centre and aft attachments are present: male and female lugs and parts
of the fuselage frames (frames 84, 85, 86 and 87).

1.12.3.5.3 Examination of the fin structure
Rib 1 had almost completely disappeared.
Rib 2 was bent upwards with a right-left symmetry.
The front of the fin showed signs of symmetrical compression damage:
• failure of the leading edge right- and left-hand panels
• longitudinal cracking of the leading edge stiffener
• HF antenna support (attached to the forward spar): failure of the lower
part, crumpling indicating bottom-upwards compression loads

1.12.3.5.4 Examination of the vertical stabiliser – rudder attachments
The vertical load pick-up arm in the rudder’s hinge axis (arm 36 g) broke at the
level of the attachment lug on the rudder side.
The size of this arm is calculated to withstand a maximum load of 120,000 N,
corresponding to a relative acceleration of 36 g of the rudder in relation to the
vertical stabilizer.

Shear cracks, along a top-down axis, can also be seen on the rudder hinge arm
attachment fittings close to arm 36 g.
These observations indicate that the vertical stabiliser was subjected to a load
greater than 120,000 N in the rudder’s hinge axis.

1.12.3.5.5 Examination of the Rudder Travel Limiter Unit (RTLU)
The RTLU was found in its place in the fin and disassembled. An examination
was performed at the manufacturer’s and showed that it would allow travel
of the rudder measured as 7.9° +/- 0.1°. As an example, at FL350, this travel is
obtained for Mach 0.8 +/- 0.004, corresponding to a CAS of 272 +/- 2 kt.
Note: the maximum travel of the rudder is calculated in relation to the airplane
confi guration, its speed and its Mach number. This travel can be commanded between 4 degrees and 35 degrees.

1.12.3.5.6 Examination of the fuselage parts (remains of the skin, frames and
web frames)
The fuselage was sheared along the frames and centre and aft attachment
lugs by loads applied bottom-upwards.

The part of frame 87 that can be seen had undergone S-shaped deformation:
the left-hand side forwards, and the right-hand side backwards. The horizontal
stabiliser actuator supports were deformed and broke in a backwards
movement from the front. These observations indicate a backwards movement
of the trimmable horizontal stabiliser.

Frames 84 and 85 were pushed in backwards in the middle. The deformations
observed on the rudder control rod are consistent with this indentation.
The deformations of the frames were probably the consequence of the water
braking the aircraft’s forward movement.

1.12.3.5.7 Examination of the fin-to-fuselage attachments
The centre attachment had pivoted backwards with the parts of the frames
and web frames that were attached to it. The aft attachment had pivoted
forwards with the parts of the frames and web frames that were attached to it.

The aft attachment lugs (male on the fin and female on the airframe) had
marks indicating a backwards movement of frames 86 and 87 as a whole.

The centre and aft lateral load pick-up rods showed damage that was consistent
with this backwards pivoting of frames 84 to 87:
• tensile failure of the centre spar at the level of the centre rod attachments;
• compression failure of the aft spar at the level of the aft rod attachments
and failure of the left-hand rod by buckling.

[jimjim1]

sb_sfo (http://www.pprune.org/members/300425-sb_sfo) mentioned:
As it's one year to the day since this accident, I wonder if we'll be any closer to an answer in another year.South African Airways Flight 295

- Crashed into the Indian Ocean near Mauritius on 28 November 1987
- Abandoned the search on 8 January 1988 when the pingers were known to have stopped transmitting
- On January 6, 1989, the cockpit voice recorder was salvaged successfully from record depth of 4,900 metres (16,100 ft), but the flight data recorder was never found.

I would imagine that the sonar could be a lot better 20 years later, nearly everything else it.

So why not more progress on af477?

I found this a good read.
Blank Design page (http://strumpfer.com/Papers/HelderbergSearch.htm)
I read it a while back and I recall thinking it might be somewhat self-congratulory however I was convinced overall.

[cc45]

zSHARE video - Lost - The Mystery of Flight 447 _30 May 2010__PDTV_XviD__.avi.flv (http://www.zshare.net/videoplayer/player.php?SID=dl028&FID=76720262&FN=Lost%20-%20The%20Mystery%20of%20Flight%20447%20_30%20May%202010__PDT V_XviD__.avi.flv&iframewidth=648&iframeheight=415&width=640&height=370&H=767202621d6953ef)

[GreatBear]

The upset occurred within seconds of the ACARS position report at 0210 (02:10:10 - .1/WRN/WN0906010210 221002006AUTO FLT AP OFF). Minutes later, the aircraft reported that cabin pressure couldn't keep up with ambient (02:14:26 - .1/WRN/WN0906010214 213100206ADVISORY CABIN VERTICAL SPEED). Assume the aircraft was (and had been) falling fast. But not so fast as to exceed V-tears-itself-apart: impacted water intact at high vertical speed in line of flight.

In the earlier thread there was quite a bit of discussion about stalls and spins in an A330. Could a slow, flat spin have occurred after being upset and stalling at altitude? Could the pilot(s) have been working their way out of the spin with inventive ailerons and flaps, elevators and spoilers, getting the nose down and rotation stopped, airflow and nose-up AOA back, finally inching out of dive towards a level flight, degree by degree, deep into g forces. "Stand on the opposite rudder and then pump the elevator forward and hold it," my CFI explained from the right seat many years ago. I'm pretty sure this NASA Standard spin recovery procedure (PARE (http://en.wikipedia.org/wiki/PARE_%28aviation%29)) wouldn't work in rudder-limited Alt2 law... Don't know that control of AF447 was ever regained following the initial upset. Spin testing of commercial aircraft not part of the certification process nor part of training, as far as I know. Possibly a case of "unrecoverable spin mode" where "there is no guarantee that spin recovery can be effected beyond the first turn in a spin."

From the point of upset, and knowing/assuming the aircraft was in the water in less than five minutes, you can draw concentric circles showing the farthest the aircraft might have flown in a straight line at various averaged ground speeds. Thus in five minutes, the aircraft could have traveled as far as 24.9 nautical miles at an averaged ground speed of 300 knots. Could have traveled farther at a constant 400 knots. But forward travel not likely, with the aircraft out of control. See diagram.

More likely, all went bad and vertical very quickly. Shedding velocity and motion along the track, unusual attitudes, rapid descent (in a spin?), dark, stormy... Draw that circle maybe ten or fifteen nautical miles radius from the Last Known Position. BEA have not searched there yet.

http://i958.photobucket.com/albums/ae66/GreatBearMaine/AF447/crashDistance.jpg

GB

[GarageYears]

Originally Posted by bearfoil http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/buttons/viewpost.gif (http://www.pprune.org/rumours-news/395105-af-447-search-resume-post5728561.html#post5728561)
Look for Voice recognition commands to the controls in the future.


I am currently working on a development intended to add speech recognition support to Level D flight simulators. Initially this is intended to be an instructor support facility.

I can categorically state that no one reading this forum would want speech recognition controlling anything at all flight critical. For one thing, any accent is likely to break the recognition completely or at best reduce the word-recognition success rates to pitiful numbers, and secondly stressed, faster speech results in the same reduction in accuracy.

I have previously worked on cockpit speech control control systems for aircraft such as the Eurofighter and in that case only non-flight critical systems were capable of speech control.

"I'm sorry Dave, I'm afraid I can't do that" :8

- GY

[Mr Optimistic]

The BBC programme had a military pilot fly a full simulator with a 'commercial jet' profile. Lost 19000 feet in less than 50 seconds and was of the opinion that unless you had been trained in stall recovery the chances of successful outcome were low. From what I have read elsewhere on this thread the chance of significant structural damage following a stall are high. The BBC hedged its bets on this and went with the BEA report, citing the radome and VS as evidence that the aircraft was structurally intact on impact. The programme was quite sympathetic to the crew I felt and was fair to the extent that it didn't pretend to have the final answer or paper over inconclusive/conflicting evidence.

[HazelNuts39]

From what I have read elsewhere on this thread the chance of significant structural damage following a stall are high.
The prototypes of any new airplane type do hundreds of stalls. Gentle stalls at 1 kt/sec; accelerated stalls at 2 - 3 kt/sec, turning flight stalls, power-on stalls, stalls with simulated and natural ice shapes on wings and tailplane, etc. etc., all well beyond the point of maximum lift and often into heavy buffet. There is some concern that, if you do hundreds of them on the same test-airplane, the fatigue life of the structure may be affected.

EDIT:: Stalls are demonstrated from various altitudes, if I remember correctly, from 5000 ft upwards. I heard the BBC person say that a stall is catastrophic, which is somewhat exaggerated. The colonel was clearly hired to demonstrate just that, and made an exciting show of it.

HN39

[bearfoil]

I think she didn't spin. Besides the constant com via ACARS, the Vertical Stabilizer could not have sustained that load. A spin would involve too much immediate roll to deal with as well. Level the wings (or at least center the ailerons), stomp the Rudder, and PUSH to break the Stall. 150 tons; wouldn't have entered a spin or recovered if it had. This is what the "Intact at Impact" suggests, deliberately or parenthetically. If the Elevator was used in this fashion, and failed (separated), it would have been "Up".
The same way as the water would have failed it.

The airframe was yawing left at impact, and flat, (minor NU), with a left wing low. (BEA).

Large Vertical velocity (vertical acceleration at impact). What does that say? If nothing else, it means it was falling, fast, ie, losing altitude at a rapid rate. If she began her descent in the deep vertical, and finished the same way, there isn't much forward progress to send the searchers 70 miles out. (Great Bear).

bear

[RetiredF4]

bearfoil
I think she didn't spin. Besides the constant com via ACARS, the Vertical Stabilizer could not have sustained that load. A spin would involve too much immediate roll to deal with as well.


It might be different in heavy metal, but my expierience concerning loads is another one.
In a spin there must not be a lot of load on the VS. In a spin there is a corksqrew flightpath with simultaneous yaw, roll and turn and high descent rate. The uneven stalled wings will produce the yaw, the following load on the VS will cause the rolll, both together keep the system turning. The forces are not hitting it broadside, to tell it simple it is the only part still aerodynamically effective. The load is only higher during entry and recovery. It is also noticable in the cockpit (have done spins myself in T-37 Trainer), the spin itself is not that uncomfortable, the entry and exit is.

franzl

[HazelNuts39]

The airframe was yawing left at impact, and flat, (minor NU), with a left wing low. (BEA).
bearfoil;

As expected, you would respond to my casual remark. Thank you for giving me the opportunity to explain.

The distortions of the frames showed that they broke during a forward motion with a slight twisting component towards the left.

That is of course relative to the fuselage. Relative to earth, the VS wanted to go straight ahead, but the airplane veered to the right. Therefore: right wing low.

HN39

[bearfoil]

Retired F4

The "load" I meant to be the load to stop the spin with opposite Rudder.
Ruddering opposite the yaw caused the failure in AA587. (Allegedly).:ouch:

If in RTLU at 4 degree limit, will that accomplish recovery? Enough?

HazelNuts39

I remembered the first report as left wing low, yawing left. Wrong? This computer does not have BEA reports.

thanks, bear

[RetiredF4]

Is there a recovery procedure with full rudder opposite the turning direction of the spin for airbus?

We had a saying that rudder brings you into spin, but not aut of it.
As mentioned before, i didn´t fly it in heavies, we had to unload to the max extent and apply full aileron in the direction of the spin / turnneedle and keep the rudder neutral. When the aircraft unloaded, rudder and ailerons had to be kept at neutral antil flying speed was achieved.

The force on leaving a spin is not the sudden stop of turning (because it doesn´t happen that fast), it is the sudden unloading when spin recovery procedure is successful.

But again, my expieience is not on heavies.

franzl

[sensor_validation]

@RetiredF4

It was stated in earlier posts that Airbus test pilots have drag chutes to deploy when testing, can't find the reference but

AF 447 – What The Crew Did … Maybe Dark Matter (http://msquair.wordpress.com/2010/02/07/af-447-what-the-crew-did-maybe/)

states

10. A hazard of large aircraft design is that they can become inertially locked in a developed spin and are unrecoverable without a drag chute, if at all.

@GreatBear re where?

In your scenario surely South or South East of last position is possible? The flightpath to Tasil was well searched by SAR. Recent searches went right up to the 40NM limit North/ North West, ignoring debris field drift evidence. Why?

[SaturnV]

mm43 or takata may have the exact coordinates for the two search boxes flown on June 1, but eyeballing the graphic, it would seem that the search that day covered an area about 20 NM to the left of the track, from the last reported position halfway to Tasil. It is hard to believe that if the plane had impacted within this grid, that evidence of the impact would have been missed. The first bodies and wreckage were recovered on June 6 at about 30 deg 30' N, 3 deg 30' W; an area, where some of which was probably within the search grid flown on June 1.

[bearfoil]

I think it's fair to say my focus on control surfaces might be annoying. If so, I simply find BEA's explanation wanting. I would like nothing more than to simply say, that's it!

The colored surfaces in red of the missing controls say quite a bit. It is possible of course that the airliner just sat in, with the VS equilaterally driving vertically down into the tail's support structure, then being spit out, with only a leading edge squash left instead of shrapnel, (spoiler). Then too, takata points to a lack of hydraulics problems on the ECAM. As the linked essay states, the comparable "peace" of a deep stall, potentially cueless, (compared to buffet and airstream noise of other ua's) might have been the last attempt to establish controlled flight. Controls that require airflow parallel to their surface are useless in vertical mush. Especially when trying to move a stubborn 150 tons

I have some folks working on animations of possible paths 447 took downward.
I'll look at them and decide if they are appropriate.

bear

[GreatBear]

Sensor_Validation:

Here's a graphic overlay of the latest BEA Search Area Update, 17 May, 2010, centered on the Last Known Position. As you can see, no part of the central 20nm diameter area has been searched. Some search traverses were made northward and eastward about 12 miles out from the LKP. The blue area directly north of the LKP is very deep.

The bodies seemed to drift in a cluster along a course setting due northward from this central area (see post 1120 (http://www.pprune.org/5709629-post1120.html)).

In your scenario surely South or South East of last position is possible?No reason to believe the aircraft didn't end up southward of the LKP, either. Once the upset developed, heading became irrelevant.

http://i958.photobucket.com/albums/ae66/GreatBearMaine/AF447/searchZones.jpg

GB

[mm43]

originally posted by Bearfoil ...
Controls that require airflow parallel to their surface are useless in vertical mush. Especially when trying to move a stubborn 150 tons Agreed. So unless there was sufficient forward motion through the air, the V/S would have no stabilizing effect, and neither would +/- 4° of rudder. Likewise HN39's comment regarding a yaw to starboard and the right wing dipping slightly because of the V/S moving to port would have caused a small roll effect, also comes unstuck.

The scenario of a high vertical acceleration with a small nose up pitch and wings nearly level, equates more to a slowly rotating flat spin where all the control surfaces had no affect because of the lost lift and the vortex created. The fact that the BEA reported that damage to the hull was symmetrical leads me to believe that the aircraft's heading nearly matched the real direction of "flight" [travel] at the point of impact.

HN39;
Your description of the forces involved on the V/S at the point of impact is appreciated. They have of course exceeded the magical "36 g"!

mm43

[jsfboat]

I wonder if Dr. Ballard will be called in, if anyone can find something on the bottom, he's the man for the job. With Titanic, Bismark, Yorktown and several others, I'm sure he would do well. I hope that it will be found

[mmciau]

jsfboat
I wonder if Dr. Ballard will be called in, if anyone can find something on the bottom, he's the man for the job. With Titanic, Bismark, Yorktown and several others, I'm sure he would do well. I hope that it will be found

I think this gentleman was the one who found the location of the HMAS Sydney off Western Australia.


Mike

[mm43]

originally posted by SaturnV ...
... may have the exact coordinates for the two search boxes flown on June 1, but eyeballing the graphic, it would seem that the search that day covered an area about 20 NM to the left of the track, from the last reported position halfway to Tasil. It is hard to believe that if the plane had impacted within this grid, that evidence of the impact would have been missed.The FAB screen shot shown in post #1127 (http://www.pprune.org/rumours-news/395105-af-447-search-resume-57.html#post5711208) shows the early search was a grid search along the route from the LKP to TASIL and it commenced 10NM before the LKP and included 10NM each side of projected track to about 42NM from LKP. A more intensive search was done from LKP to TASIL at about 3NM each side of track. The finding of some unidentified debris to the SE of the LKP disrupted any further searching in what we now believe was the area of real interest.

mm43

[crippen]

Has anybody thought about the main body of the aircraft not sinking to the bottom of the ocean?

Some composite boats reach a depth in the water where the hull is just the same density as the water and stop there,and just float with the tide,or so I have been told.???:confused::confused:

[kwateow]

The mainly composite part broke off, floated, and was fished out.

The rest of the structure is metallic. It's not airtight, so it will sink.

[takata]

Hello GreatBear,
More likely, all went bad and vertical very quickly. Shedding velocity and motion along the track, unusual attitudes, rapid descent (in a spin?), dark, stormy... Draw that circle maybe ten or fifteen nautical miles radius from the Last Known Position. BEA have not searched there yet.
In fact, this is the first place the BEA searched with its best assets (USN's dedicated TPLs = pinger locators) when the recorder's balises where still working.
You should remember that the search operation is in phase 3 and that the previous two phases were detailed in BEA 2nd report, annexe 2, p. 77-86.

In short: they defined the most probable crash zone called "Alpha zone" starting about 10 nm South of last know positition and extending to 10 nm South of Tasil. This is the black box pictured in the map below:
http://takata1940.free.fr/search1.jpg
Each grid box is 10 x 10 nm.
When pingers stopped to work, they assessed the above "quality" map to continue into phase 2 where other means were deployed by oceanic survey vessel Pourquoi pas? consisting of deep sonar robots (i.e. J-K-L-M 24 previously skipped boxes were searched this way). The goal was to systematically finish the Alpha zone and eventually also the 40 nm radius defined circle centered at LKP.

As you can see it now, phase 3 is completing the previous work using better reverse drift models newly developped, but they were also scanning already searched boxes having low quality scores (mostly from Emeraude's assigned zone).

Taking into account the very high probability that TPLs would have picked any signal from the recorders along the flight path to TASIL (where the relief is much more gentle), it is very probable that AF447's wreck is not located into this zone... or, if it is really there, that both pingers were destroyed during the crash.

The upset occurred within seconds of the ACARS position report at 0210 (02:10:10 - .1/WRN/WN0906010210 221002006AUTO FLT AP OFF). Minutes later, the aircraft reported that cabin pressure couldn't keep up with ambient (02:14:26 - .1/WRN/WN0906010214 213100206ADVISORY CABIN VERTICAL SPEED). Assume the aircraft was (and had been) falling fast. But not so fast as to exceed V-tears-itself-apart: impacted water intact at high vertical speed in line of flight.
You are right considering two big 'IF'.
- If upset did take place at 0210... [nothing is telling us it did].
- If end of flight was ~0215... [there is still very good chances it was not].
About the time it could take for AF447 to go down, something as fast as 1 minute and half is possible from cruise level. Then if ~0215 was the end of flight, an upset could have occured as late as ~0214, making quite some distance between 0210 (LKP) and crash site.

Consequently, the next major step into this investigation would have to be the localization of the wreckage which, by itself, will reveal a lot more about this upset/crash sequence. Last declarations (yesterday) are telling us hoppefully that the search will not stop here and big efforts will continue until they find it.

S~
Olivier

[HazelNuts39]

In his post #1358 sensor validation offers a link to an article by "Dark Matter". While that article is mainly the usual mix of truths, half truths, and misconceptions, it contains a link to an interesting article in the Boeing Aeromagazine on Upsets, that I would like to recommend to many readers of this thread:

Boeing Upset article (http://www.boeing.com/commercial/aeromagazine/aero_03/textonly/fo01txt.html)

HN39

[Centrosphere]

HN39

Very interesting.

Well, I´m new here, so forgive me if this was already asked by someone, but what are the prerequisites to becoming an airline pilot and, specially, to piloting large aircraft like an A-330 or a 7x7?

The article you linked to stress the need of pilots to be familiar with the laws of physics. It seems to me that this would constrain the pool of would be pilots to engineers, physicists and mathematicians. Maybe some economists also. :)

What is the usual extraction of the pilot workforce in the airlines?

ps: I´m a brazilian that for profissional reasons fly over the south atlantic quite often, including in the ill-fated AF447. I have read this thread from the beggining, and also the old one. I´m an engineer, but have no training in the aeronautics industry, and must confess that I´m learning a lot from the very competent commentators here.

[Lemurian]

The list of authors of the article has five names from Boeing and two from Airbus. That is understandable because it's a Boeing magazine. However, more generally, it seems to me that it is always Boeing who takes the lead in these inititiatives. Is this perhaps an area where Airbus could make an effort to match Boeing?
Is this where ignorance is bliss ?
Have a look at this site, for instance Smartcockpit flight ops docs (http://www.smartcockpit.com/flightops)

or check John Tullamarine's sticky thread " Useful websites and document references" in TECH LOG.
some knowledge in these two places.

and , of course, your hunch is wrong.

Regards

[henra]

Bearfoil

I have some folks working on animations of possible paths 447 took downward.
I'll look at them and decide if they are appropriate.


Bearfoil,
If I may ask : What is your profession / personal connection to this accident ?

Are you a lawyer or journalist or something completely different that you have people working on this?

[takata]

Hello Centrosphere,

Well, I´m new here, so forgive me if this was already asked by someone, but what are the prerequisites to becoming an airline pilot and, specially, to piloting large aircraft like an A-330 or a 7x7?

The article you linked to stress the need of pilots to be familiar with the laws of physics. It seems to me that this would constrain the pool of would be pilots to engineers, physicists and mathematicians. Maybe some economists also. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif

What is the usual extraction of the pilot workforce in the airlines?

It is not the same depending on countries. Concerning France, the main courses are ENAC (École Nationale de l'Aviation Civile, in Toulouse, one of the French prestigious "grandes écoles") and, for older generations also l'École de l'Air (Armée de l'Air). Both course are following a very serious scientific baccalaureat plus preparation and will provide a diploma at least equivalent to an engineer.
See ENAC page here: ENAC - Ecole - Accueil (http://www.enac.fr/pages_en/ecole/ecole_accueil.htm)
S~
Olivier

[HazelNuts39]

Lemurian;

Thank you for your useful and very welcome link to the Smartcockpit site. I wasn't aware of it and certainly still have to learn a lot about sources of information freely available on the web. On second thoughts, I have removed the remark from my post.

Regards,
HN39

[geoff sutherland]

The second BEA interim report into AF447, (p62-67), identified 32 other incidents caused by or related to freezing of pitots on A330-A340 and also stated that the test/certification regime (JAR25) for those pitots was for a maximum altitude of 30,000ft.
Why is it that one of the most heavily regulated industries in the world allows almost all of its commercial operations to be conducted using a critical speed sensing technology that is neither tested nor certified for critical icing factors at the very altitude that almost all of their commercial flights are conducted.
Maybe they should limit all flights to within the certified envelope (30,000ft) and wait for the business out-cry to put funds into solving the problem.

[GreatBear]

Takata,

Aaaaah yes, there are so many Unknowns! So many IFs. So many Possibilities. So many Questions.

My bad, not to clarify "BEA have not searched there yet" by adding "with side-scanning sonar." Appendix 2 of the 2nd Report includes a graphic ("Lanes defined in the search zone") and states "The SAR was operated on line 24, squares J,K, L and M." That's eight to ten nautical miles southwest of the Last Known Position, so it seems that IFREMER’s Towed Acoustic Sonar (TAS), with its 1 pixel for 25 cm resolution, only explored a tiny corner of the area within a 10nm radius of the LKP during Phase 2.

It's unfortunate that the very best assets (including a nuclear submarine) and TPL technology could not locate the pingers during Phase 1 in the Alpha Zone or elsewhere before their predicted battery life expired. As you say, if the wreckage is really in a tight circle near the LKP, both pingers could have been destroyed during the crash. Recommendations are already in place for lowered beacon frequencies, and pinger specs and CDR methodologies are undergoing a broad re-evaluation by the industry.

The timing of events with clues only in the ACARS messages is very tricky. My thinking is that for the 02:14:26 cabin vertical speed message to be sent, it had to be triggered by a rapid descent at least a minute or two PRIOR to its transmission. As the BBC experiment showed, a fall of 19,000 feet in 50 seconds might be a worst-case possibility. So the actual falling event must have begun well before that last message was timestamped and sent. In any case, it would seem that loss of control (the upset) occurred closer to 02:10, well before the cabin vertical speed message was sent. The idea of straight-and-level cruise flight much beyond AP Disconnect at 02:10:10 is difficult for me, but I am continually trying to simplify a very complicated event.

Aaaaaah, the unknowns.

Without doubt, the BEA search effort has gathered the best minds and resources to recover the hull and black boxes. It's simply one of the most difficult researches so far undertaken in this 21st Century.

Thank you for your considered feedback.

GB

[auv-ee]

I wonder if Dr. Ballard will be called in, if anyone can find something on the bottom, he's the man for the job. With Titanic, Bismark, Yorktown and several others, I'm sure he would do well. I hope that it will be found

I think this gentleman was the one who found the location of the HMAS Sydney off Western Australia.

The French are already familiar with Dr. Ballard, and Paul-Henri Nargeolet has an opinion:

http://www.titanicfiles.org/Essays_englisch/An%20open%20letter%20to%20Bob%20Ballard.pdf

[takata]

GreatBear,

Aaaaah yes, there are so many Unknowns! So many IFs. So many Possibilities. So many Questions.
Good point! my opinion too as one really need to keep open the right possibilities and discarding the wrongs only very very carrefully without being subject to tunnel vision.

It's unfortunate that the very best assets (including a nuclear submarine) and TPL technology could not locate the pingers during Phase 1 in the Alpha Zone or elsewhere before their predicted battery life expired. As you say, if the wreckage is really in a tight circle near the LKP, both pingers could have been destroyed during the crash. Recommendations are already in place for lowered beacon frequencies, and pinger specs and CDR methodologies are undergoing a broad re-evaluation by the industry.
There is still a good hope that the Navy picked the right signal. As a former member of this institution, I'm very confident about it, even if MOD's communication nearly ruined its credibility against BEA (to be verified) opinion of "no aircraft South of LKP".
The timing of events with clues only in the ACARS messages is very tricky. My thinking is that for the 02:14:26 cabin vertical speed message to be sent, it had to be triggered by a rapid descent at least a minute or two PRIOR to its transmission.
This cabin vertical speed message is still under high scrutinity. It will be very difficult to fully understand it without knowing precisely what was the exact configuration of the aircraft when it was triggered, but also, because it was the last one of the sequence while few more ACARS could have told a lot more about it. We can't know for sure that the flight ended strait after or a while after.
In fact, it left only three choices open: a) crash in the following seconds or b) ACARS failure; c) EMER-ELEC config.

This advisory can be triggered both in PRESS auto or manual mode (crew action). If PRESS manual mode (for whatever reason) was selected when the valve was open, cabin vertical speed could climb quite fast. All we know is that during 5 seconds (at least), the cabin moved (up or down) by 150 ft (at least). If PRESS was in auto mode and no ADR was valid, it is also possible, beside other faults, that the security will work as to keep the DeltaP (internal/external) constant based on other data (then move at the same rate at the aircraft from whatever altitude). AIRBUS FLIGHT SAFETY DEPARTMENT communicated about it that its meaning was not obvious:
The above mentioned messages indicate that there was unreliable
airspeed indication. This unreliable airspeed situation is
consolidated by several messages which show system reconfigurations
which are per- design consequences of the unreliable airspeed
indication.
The last transmitted message corresponds to the ECAM Advisory message
indicating a change of cabin altitude at a rate greater than 1800
ft/min, which remains to be explained.
Some messages might be consistent with unreliable airspeed indication
but require further analysis. Other messages likely result from
further aircraft evolution and/or crew actions. Finally system status
messages have also been transmitted but are not relevant for the
understanding of the event.
The data available at this stage of the investigation:
- does not suggest any loss of electrical power supply,
- does not suggest a loss of instrument display,
- does not suggest an ADIRU misbehaviour as encountered in a
recent A330 event for 2 reasons: the ADIRU supplier and the signature
of failure related messages are not the same as on AF447,
- does not explain the complete sequence of events which led to
AF447 accident.But, as it was the last ACARS sent, and like EMER-ELEC could have followed it - without being transmitted due to ACARS shut down - a wider range of possibilities could even occur (i.e. was it the consequence of engine roll back on PRESS/VENT systems before flameout?, etc.).

As the BBC experiment showed, a fall of 19,000 feet in 50 seconds might be a worst-case possibility. So the actual falling event must have begun well before that last message was timestamped and sent. In any case, it would seem that loss of control (the upset) occurred closer to 02:10, well before the cabin vertical speed message was sent. The idea of straight-and-level cruise flight much beyond AP Disconnect at 02:10:10 is difficult for me, but I am continually trying to simplify a very complicated event.
The BBC show was overall good (I feared worse) but there was still some fair amount of drama over reality; The third pilot would not have been PF if the commandant was resting (which is still unproved but quite possible). More annoying was the fact that they used an A320 simulator showing wrong settings (mach 0.76 in place of min. 0.80) and did not follow the real SOP -quite conveniently- for addressing their "non-moving throttles have been forgotten" theory (not adjusted to right settings), then the aircraft was stalled in heavy turbulences.

But as ATHR was ON, then kicked OFF with AP, it would also trigger a warning every 5 seconds until throttles would be adjusted into the right settings manually. Consequently, it would be pretty hard to forget about thrust and let the airspeed drop down to any dangerous level without noticing it. If turbulences were already an issue, ATHR would be OFF and the correct parameters of pitch and thrust already set before this pitot issue... In short, this is unlikely enough to produce an upset at this stage unless unknown issues or maybe, the appearance of all factors at exactly the same time (freezing, multiples faults, and unexpected heavy turbulences).

Concerning the stall demo, it is hard to tell as important details about the military simulator settings are left vague but it might be possible to go down in about 90 s without breaking appart the airframe. In this case horizontal distance covered would be quite limited and aircraft terminal attitude unlikely level.

S~
Olivier

[Chronus]

I am not sure whether any references have previously been made to the Swissair Flight 111 MD-11 crash of 2 September 1998. I would have thought a lot of knowledge was gained in underwater search and recovery operations and techniques from this accident. It took TSB of Canada four years and cost CAD 57 million (approx USD 38million ) to get the answers. The aircraft had crashed closer inshore and the debris lay relatively in much shallower waters.
In the case of AF447 the cost to date is EUR 9 million and the depth and extent of the search area is considerably larger. Should the FDRs and the CVR be eventualy recovered it is not an absolute certainty that the answers will be provided. Should the wreckage be found what would be the challanges and difficulties in recovering it from the great depths of the ocean. What may the final cost amount to.

How much should be spent on accident investigation for the sole benefit of flight safety. Surely in these days of global economic austerity there must be a limit.

[mmciau]

auv-ee

The French are already familiar with Dr. Ballard, and Paul-Henri Nargeolet has an opinion:

http://www.titanicfiles.org/Essays_e...%20Ballard.pdf (http://www.titanicfiles.org/Essays_e...%20Ballard.pdf)

Thank you for that insight and reference.

In return, may I recommend you have a look at the following site regarding the HMAS Sydney and in particular the Volumes 1-3 of the outcomes of the search and find.

The Search for the HMAS Sydney II Report Available for Download - Official Press Releases (http://presspass.findingsydney.com/blogs/official_finding_sydney_foundation_media_releases/archive/2008/10/28/report.aspx)

They were also searching in deep water but no where near the depth of water AF447 is resting .

Thanks again for providing that reference - it enables one to get a better understanding of matters.

Mike McInerney

[gwillie]

cc45

BBC AF447 documentary June 2010 available on the web

zSHARE video - Lost - The Mystery of Flight 447 _30 May 2010__PDTV_XviD__.avi.flv
Anyone aware of an alternate site hosting this program? The video streaming from that site...well, at least here, isn't.

[Unusual Attitude]

"Without doubt, the BEA search effort has gathered the best minds and resources to recover the hull and black boxes. It's simply one of the most difficult researches so far undertaken in this 21st Century."

I'm sorry but I could not disagree more strongly. The stipulation within the last tender issued that AUV's would be used for this search raised eyebrows amonst many involved in the subsea search & salvage industry.

An AUV is designed to fly over ideally a flat sandy bottom flying a pre programmed route using waypoints, ideal for a lengthy cable / pipeline / route survey. The terrain involved in the AF447 is about as far from ideal as you could get for the use of AUV's. The second factor being the battery life of an AUV and the time taken to submerge to 4000m, basically by the time it gets down there there is very little time left to actually do any searching before it then needs to start the journey back to the surface.

Basically the use of AUV's are a great way to spend a lot of time messing about without actually getting much searching done, I'll leave it at that.

[D Bru]

Failure to so far locate F-GZCP to the N, NE, NW, W and SW of LKP prompted me to revisit information on the currents and surface debris locations.

I'm well aware of mm43's analysis suggesting a location SW of LKP, relatively close to the area resulting of Meteo France's reverse-drift analysis, and until recently reinforced by the French Navy supposed pinger data.

A SW of LKP location is of course still not to be excluded, but one should beware of tunnel-thinking. Although BEA's recent stance that F-GZCP "has never been south of LKP" may equally be qualified as such, please consider the following:

Unless there was an immediate catastrophic event @ 0210 (other than iced pitots) there is little reason to assume that F-GZCP would be instantly that much off course that it could within 4 minutes end up at a location that would require (significantly) more than a 90° turn. To maintain heading would normally be a priority for a crew dealing with a series of events as it was confronted with according to the ACARS messages.

And if weather ahead would have required a change of course under those circumstances, it would make sense to turn the least possible. Given the N/NE course of F-GZCP, that would imply a turn to E rather to W.

Not only have two US reverse drift analyses suggested an impact point to the NE and NE/E of LKP respectively, also data of the Mercator model (used by Meteo France) do not exclude that.

I'm not privy to all data available to Meteo France used for their reverse drift calcs, but the Mercator based graphs I got hold of show that although on 27 May (closest I could get to 1 June) the prevalent current NE of LKP was E/NE, on 2 June the current was W/NW, while turning N on 9 June. US model based data are even more clear on a prevalent W/NW current.

Taken together this would IMHO not rule out that F-GZCP after its LKP initially pursued along its heading followed by a (relatively shallow/controlled) turn right and possibly ended up fairly E/NE near the 40nm search perimeter. We know that this area wasn't covered that well initially and certainly has not been covered recently.

Such an E/NE point of impact could also better explain the three debris items found in that area (see map page 37 of BEA's 1st interim report). Strangely enough these three debris items do not figure in the 1st interim report's annex 4 where a day by day location of the finds is given. So, unfortunately it is impossible to say when they were found and, equally important, what they are (in terms of how high or low they would float).


Dutch

[Gringobr]

I managed to download it and have it shared in Winmx..
Also, you could watch/download it using the BBC iPlayer from their site
If you are not in the UK you will have to use a proxy IP..

[SaturnV]

Dutch, the area E and NE of the LKP was searched extensively between June 2 and June 5, and nothing was found. How do you reconcile your hypothesis with the first body and wreckage being found W and NW of the LNP on June 6?

[poorjohn]

It's available on usenet, for those of you familiar with that concept. In alt.binaries.multimedia.

[jcjeant]

Hi,

Just tested and the streaming fom Zshare still available ....

[auv-ee]

The stipulation within the last tender issued that AUV's would be used for this search raised eyebrows amonst many involved in the subsea search & salvage industry.

An AUV is designed to fly over ideally a flat sandy bottom flying a pre programmed route using waypoints, ideal for a lengthy cable / pipeline / route survey. The terrain involved in the AF447 is about as far from ideal as you could get for the use of AUV's. The second factor being the battery life of an AUV and the time taken to submerge to 4000m, basically by the time it gets down there there is very little time left to actually do any searching before it then needs to start the journey back to the surface.

I'm curious to know what alternative you propose and what its search rate and percent coverage would be in mountainous terrain. All other systems I can think of are tethered and have issues of their own.

While any search system works better on a flat bottom, AUVs have characteristics that make them well suited to this work:

1. I covered the search rate parameters in post http://www.pprune.org/5692187-post1029.html
It works out to about 40 square kilometers/day for double coverage by one vehicle. [BEA: 100sq-km/day/AUV, maybe for single coverage.] A claim of much time lost in vertical transit is simply incorrect. REMUS-6000 descends and ascends at an average rate of about 60m/min, so it can make a one-way excursion to 3500m in 1 hour. With a 20-22 hour mission time, 2 hours lost in descent/ascent, and a 2-4 hour turn-around at the surface, that yields 18-20 bottom hours out of every 20-26 hours. Even with the worst of those values, the vehicle is on the bottom 70% of the time.

2. When surveying the bottom, the AUV transits at 4 knots. All the towed systems I know of are limited to 1-2 knots in deep water, to prevent the cable drag from lifting the vehicle off the bottom. [BEA: Orion system is listed at 2kts. BEA also lists 100sq-km/day/towed sonar, probably using lower frequency, lower resolution, but longer range to offset the slower tow speed.] Perhaps if the entire cable is faired, then the speed could increase, but that would significantly increase the size and complexity of the cable handling system.

3. AUVs spend no time in turns (other than the few minutes it takes to cover the offset distance between survey lines). [BEA: 15min for AUV.] Towed systems follow the ship track with 30-60min delay in deep water, and it can take 6-12 hours to align with the next track. There are perhaps operating skills that could shorten that time, but it won't be minutes. [BEA: Orion system turn time listed as 3hr.] Turn time is to the towed system, as vertical transit/servicing is to the AUV.

4. AUVs can follow the bottom more closely in rugged terrain than towed systems, at least more closely than I have seen towed operators willing to attempt. Contact of a towed system with the bottom in rough terrain carries the risk of fetching the vehicle under a ledge and breaking the cable if the winch operator and bridge watch don't react in time. For an AUV, collision with a cliff is a survivable event. While no one plans a mission to include a collision, it does happen and it is recoverable, usually with the mission continuing as planned. Aside from a collision, an AUV can follow terrain at about +/-30deg (depends on the AUV). Certainly there are steeper parts in the AF447 search area, but a lot of it is within +/-30deg, especially with "terrain aware" route planning.

5. Multiple AUVs can be operated from a single ship, further increasing search rate for a nominal increase in day rate (cost).

6. Navigation of track lines is generally more precise with an AUV, because there is no influence from ship motion. This improves coverage (fewer holidays) and becomes especially important if the debris field of AF447 is ever found, when the AUVs can be used to photo mosaic the field.

After the wide area search and initial photo work are complete, then tethered systems will be needed to finish any detailed survey or recovery.

Certainly, towed/tethered systems have advantages too. The most obvious being that the sensor data is available in real time, and similarly there is much higher bandwidth for control of the vehicle.

Enough said. I'm ready to be educated about the system(s) you have in mind.

[teleport]

BBC Investigative Documentary
The theory the producers chose to go for was roughly as follows.

......the A/C encounters super-cooled rain at –40C. Pitots freeze,....

How about using secondary navigational inputs on GPS based data?

[sensor_validation]

Unless there was an immediate catastrophic event @ 0210 (other than iced pitots) ...

And if weather ahead would have required a change of course under those circumstances...

The weather models suggest AF447 was inside the storm system @0210. They had reduced speed from M0.82 to M0.80 at some point. The final ACARS position report which probably reports the position at 02:10:30, shortly after the incident started, shows deviation West from the planned route, but with a precision that the BEA report does not appear to believe significant

AF447 ACARS MESSAGES (http://countjustonce.com/a330/acars.html)
2:10:34#0210/+2.98-30.59

The full set of ACARS position (and turbulence?) reports do not appear to be in the Public Domain. There are clearly false reports which appear to give a location for the 2:10:14z message.

The BEA 40NM search radius would appear to assume less than 1 minute level flight plus 10,000 ft/min rapid descent - keeping airframe substantially intact, triggering pressure advisory below 8,000ft and end of flight less than minute later.

It seems to me most likely that loss of control occurred almost immediately, with one cascade of problems starting with the pitots - detected at 2:10, but possibly giving faulty data before?

[takata]

Hi,
The weather models suggest AF447 was nearly through the storm system @0210. They were already deviating some 10NM W of flightpath and had reduced speed from M0.82 to M0.80 at some point, so precise heading unknown.
a) sorry, but which weather model is suggesting that?
BEA (position) + Méteo France (0215 weather sat map) data -see reports- are showing that AF447 was close to the coldest part of this active CB system @ 0210 (and roughly half way - but previous meteo analysis from Tim Vasquez was showing the wrong position on the right map).
b) Where did you get this 10 nm W of flightpath?
0210 last know position was exactly recorded 2.94 nm W of flightpath with an error margin inferior to +/-0.3 nm (eurocockpit source):
http://www.eurocockpit.com/images/UN873.jpg
http://www.eurocockpit.com/images/UN873Z.jpg

The BEA 40NM search radius would appear to assume less than 1 minute level flight plus 10,000 ft/min rapid descent - keeping airframe substantially intact, triggering pressure advisory below 8,000ft and end of flight less than minute later.
... way too much reading into this estimation!
This 40 nm circle was drawn from day 1 barely without any data analysis and absolutely no wreckage to study: 5 mn of flight (ACARS transmitted) at speed inferior to 500 knots = 40 nm (= 5.000 square nm). Alpha zone (based on higher probability) was even extended near TASIL and the Southern part, passed 10 nm from LKP, was discarded.

It seems most likely that loss of control occurred almost immediately, with one cascade of problems starting with the pitots - detected at 2:10, but giving faulty data before?
It doesn't seem most likely at all -until someone will find where the wreckage is.

Probability that it was not discovered by sea scans inside already searched zones is currently very low (both pingers destroyed).
The most unreliable part of the search so far was the airborne SAR operation during the first six days due to the lack of adequate means (site distance, very few aircraft, no helicopters), inadequate weather (low clouds, poor visibility, rain, sea state), disturbance by floating garbage (high seas are full of floating debris), dispersion with time (floating stuffs -nearly fully submerged - finally covered a large area that made it very hard to be spotted from the air).

The probability that all three sensors were giving simultaneous faulty data before 0210 is many many times more unlikely (such an issue would more likely start from the ground). More precisely, it is almost ruled out by the fact that this pitot issue was detected in flight at 0210 and that relevant systems seems to have reacted as per design.

S~
Olivier

[takata]

Hi Geoff,
You've got no answer as new post from new posters do not show up until a while and may be left unoticed. You did bring in a valid point:
The second BEA interim report into AF447, (p62-67), identified 32 other incidents caused by or related to freezing of pitots on A330-A340 and also stated that the test/certification regime (JAR25) for those pitots was for a maximum altitude of 30,000ft.
Why is it that one of the most heavily regulated industries in the world allows almost all of its commercial operations to be conducted using a critical speed sensing technology that is neither tested nor certified for critical icing factors at the very altitude that almost all of their commercial flights are conducted.
Maybe they should limit all flights to within the certified envelope (30,000ft) and wait for the business out-cry to put funds into solving the problem
It is hard to make a very simple answer to this point as this is a very complex issue. I have read few papers on the subject and this may be summarized like that:

- Until not so long ago, about 10 years, most scientists thought that no ice/water particules of any dangerous size for aircraft sensors could be encountered at altitudes above 30,000 ft due to very low atmospheric temperature. There was several long haul airliner pilots testimony saying otherwise during specific flight conditions: oceanic flight over seasonal tropical thunderstorms or at proximity of them. The problem was that it could not be reproduced in laboratory. It has to be 1) to prove the phenomenon, 2) to develop some new probe certification process.

- In fact, almost all pitot events are taking place at lower altitudes on every model of pitots, causing a lot of accidents, mostly in general aviation. Airliners are supposed to be safe due to the constant care about this known issue as well as by multiplying their sensors and backup systems. But the risk still remain that those systems could be overwhelmed by conditions not reproductibles due to actual knowledge and experimental means. It is just not possible to take a sample of one particular atmosphere and to bring it into our labs without changing it. Conditions have to be re-engineered and this seems to be the core of the problem.

- Until AF447, known pitot issues encountered in A330-340 fleet (only) lasted from 5 to 20 seconds. After AF447, other incidents occured, including the other probe models considered less sensitive than Thales AA (Thales BA & Goodrich/Rosemount probes). Actually, it seems that the probe makers are working empirically on this issue, without exactly knowing what to change in order to fix the problem, and it is the same for the regulator. Nowaday, a lot of ressources seems to be affected in order to study very seriously this phenomenon. Some scientists are pointing that it may be caused by climate changes and that it is much more frequent, others that it always existed and was dismissed, but as traffic increased, its frequency increased.

S~
Olivier

[Bluestar51]

Slightly off the current topic, is it possible that they have found some of the wreckage with their current search, but because of logistical restraints they are unable to explore those sights?

BS

[sensor_validation]

Ignore me I'm sure Takata is correct re facts re location/storm - there was much discussion in previous thread and elsewhere about how quickly you can get down in one piece from 35,000ft, clearly not a gentle 20:1 glideslope?

As stated in the BEA report, pitots on this type of aircraft have a history of problems. The AA probe itself was introduced to replace inferior earlier models, and then early examples had manufacture QC issue with drain hole

http://ftp.resource.org/gpo.gov/register/2004/2004_5788.pdf

This earlier incident on an Airbus quantifies the effect of pitot drain hole blockage for the probe in use at that time - is much higher/ faster much different in dynamic pressure?

http://www.aaib.gov.uk/cms_resources.cfm?file=/dft_avsafety_pdf_501829.pdf

So drain hole blockage alone is sufficient to disengage autopilot/ thrust.

Having identical probes makes it easier to detect one outlier - they should all read the same - but why would they then not fail in same way when subject to same ice cloud?

[takata]

Hi Bluestar51,
Slightly off the current topic, is it possible that they have found some of the wreckage with their current search, but because of logistical restraints they are unable to explore those sights?
Quite on topic!
They might have found something without actually knowing it (further data analysis may later reveal some possible traces of wreckage) but I don't think that logistical restraints would have been an issue. Those vessels were fully equiped for recovering any wreckage, or simply to verify any doubtfull spot at will.

For those interested, there is also some good videos about the search means used during this last campaign posted on BEA's site (three parts):
1.
http://www.bea.aero/fr/enquetes/vol.af.447/videos/depart.des.navires.mp4
English subtittles:
http://www.bea.aero/en/enquetes/flight.af.447/videos/depart.des.navires.srt
2.
http://www.bea.aero/fr/enquetes/vol.af.447/videos /premieres.plongees.operationnelles.mp4 (http://www.bea.aero/fr/enquetes/vol.af.447/videos%20/premieres.plongees.operationnelles.mp4)
English subtittles:
http://www.bea.aero/en/enquetes/flight.af.447/videos/premieres.plongees.operationnelles.srt
3.
http://www.bea.aero/en/enquetes/flight.af.447/videos/analyse.des.donnees.en.mp4
English subtittles:
http://www.bea.aero/en/enquetes/flight.af.447/videos/analyse.des.donnees.en.srt
[in order to read the subtittles file with the video, save it in same folder with video, use vlc, mediaplayer classic, or any player with vobsub filter.]

[takata]

sensor_validation,
Having identical probes makes it easier to detect one outlier - they should all read the same - but why would they then not fail in same way when subject to same ice cloud?
Airflow related to probe has to be perfectly symetrical, which is barely never the case in flight, because they are on both side of the fuselage. The value displayed is a mean value of two or three pitot readings.
If one probe is failling to drain one kind of particule, it doesn't mean that it will fail to drain another kind. You'll have to know what kind of particule you are dealing with.
S~
Olivier

[HazelNuts39]

The value displayed is a mean value of two or three pitot readings.
Hi takata,

My understanding is that the PRIMs use the median value of the three ADIRU's, not the mean, except for the AOA where it uses the mean of #1 and #2, as explained in the ATSB report on QF72.

Regards,
HN39

EDIT:: As to displays: no averaging, see tubby linton post #1399 below

[sensor_validation]

median of 3 (or bigger odd number) values is generally interpretted as you take the middle one when sorted in order of magnitude, without any averaging. This is sensible as it automatically ignores extremes and spikes values on any one channel. For even number you do average the middle pair. No difference between mean and median if you only have 2 values! A median filter also be applied to multiple samples over a time period, linear/ averaging filters tend to turn spikes into bumps.

[tubby linton]

Hazelnut -efis switching for capt is -normal(sys1),then sys3 then sys2.
FO switching is -normal(sys2) then sys3 then sys1.
Reference fcom 1.31.50 p3

[JD-EE]

How about using secondary navigational inputs on GPS based data?

Um. nice idea; been proposed before; GPS knows air speed?

All GPS knows is ground speed.

{o.o}

[JD-EE]

takata remarked

Hi Bluestar51,
Quote:
Slightly off the current topic, is it possible that they have found some of the wreckage with their current search, but because of logistical restraints they are unable to explore those sights?
Quite on topic!
They might have found something without actually knowing it (further data analysis may later reveal some possible traces of wreckage) but I don't think that logistical restraints would have been an issue. Those vessels were fully equiped for recovering any wreckage, or simply to verify any doubtfull spot at will.

This brings to mind the many eyes approach several groups are using to find interesting bits in huge volumes of data. If the bottom profiles were released to the public for processing and scrutiny both the state of the art and the chance of discovery of "bits" in large amounts of data improve.

If a prize is offered for finding parts of the plane it might result in cheaper and faster results.

{^_^}

[GreatBear]

JD-EE,

Yes! Many eyes looking at miles and miles of traverses. What anomalies might they find? Start with some of the contributors to this thread: engineers, scientists, pilots, masters. Bright, interested, trainable, and likely capable of the meticulous effort required. Possibly with available time.

Two problems: First, training volunteers to be able to recognize substance from noise then providing them with appropriate software and administrative infrastructure. Second, willingness of "owner" authorities to release the raw data and manage/filter the input from a Many Eyes collaborative approach...

The first problem can be solved. The second is not so easy, though eventually I hope the bathymetric data gained during the extensive search in this portion of the Mid-Atlantic Ridge will be released to the world's geophysics and oceanographic communities and be stored in the open-access international libraries for such data.

It could be that the authorities are already talking to the academic community and to those with experience with side-scanning sonar to provide more eyes.

What worries me, though, is that there may be blank spots in the already-acquired data (too deep, too fuzzy, out-of-range, dark blue, etc.) and that the search misses the hull by an unfortunate circumstance of probability. 95% of the sea floor is not 100% of the sea floor. Like pingers, not there if you don't hear it.

In any case,

Dear Mr. Bea,
We have organised an ad-hoc team of 34 highly-qualified volunteers willing to visually review your AF447 search data meter by meter, in case an anomaly or find has been overlooked during your initial traverses. Eleven are active or retired air transport pilots, seven are electrical and structural engineers, six are naval or merchant marine officers, four are computer scientists, and the remainder are just plain smart people. If you would post your raw data to an accessible FTP site, we will take a look at it in great time-consuming detail and let you know if we find anything remarkable.
Sincerely yours,
Great Bear
(or JD-EE, but I don't want to put words in your mouth.)Now if I can just find the right address...

JD-EE, it's theoretically do-able but perhaps culturally impossible. The world-wide culture of such investigations is more accustomed to locked hangars, yellow do-not-cross tape, tightly controlled evidence, very expert input, and very careful deliberation. Not a bad culture, mind you, just one unused to the public eye or, what would be perhaps more disconcerting, to public participation.

GB

[mm43]

auv-ee's post #1388 (http://www.pprune.org/rumours-news/395105-af-447-search-resume-70.html#post5733793) is well worth keeping as a detailed description of the operation of AUV's similar to those deployed from the "Seabed Worker" and as a comparison with the equivalent towed side-scan sonar that was employed by the "Anne Candies".

Thanks for taking the time to enlighten everyone on the operation of the AUV's, and it is easy to relate your description to that of the Phase 3 search just concluded.:ok:

mm43

[jimbeetle]

auv-ee,

A couple of very uninformed questions (hence the need to ask).

The oil industry has a fleet of ROVs like the 12 that are working on the Gulf spill. They're working at just shy of a mile down now. Is that their limit, or can they work deep enough to be effective at the AF-447 site?

I realize that they're tethered and that would probably add more difficulty. Anything insurmountable?

I guess I've been thinking along the lines of a couple of ships controlling a handful of these each for a very deliberate visual search that, if nothing else might rule out areas.

[xcitation]

In the search for Steve Fossett a "many eyeballs" method was used. I recall it was partly successful in that several wrecks were found but from other flights. I recall that one of the frustrations of the crowdsource group was that the data they were given was not in the SW area where it was believed his flight path went. Instead the data was only available due W of his departure airfield. Sure enough the wreckage finally turned up SW.
In the AF case I would expect something like the SETI@home project would be a better fit.

Wikip. quote...

On September 7, Google Inc. helped the search for the aviator through its connections to contractors that provide satellite imagery for its Google Earth software. Richard Branson, a British billionaire and friend of Fossett, said he and others were coordinating efforts with Google to see if any of the high-resolution images might include Fossett's aircraft.
On September 8, the first of a series of new high-resolution imagery from DigitalGlobe was made available via the Amazon Mechanical Turk beta website so that users could flag potential areas of interest for searching, in what is known as crowdsourcing. By September 11, up to 50,000 people had joined the effort, scrutinizing more than 300,000 278-foot-square squares of the imagery. Peter Cohen of Amazon believed that by September 11, the entire search area had been covered at least once. Amazon's search effort was shut down the week of October 29, without any measurable success.[58][59] Maj. Cynthia Ryan later commented that the 'crowdsourcing' was more of a hindrance than a help. She said that persons purporting to have seen the aircraft on the Mechanical Turk or have special knowledge clogged her email during critical days of the search, and for even months afterward. Many of the so-called 'sightings' proved to be images of CAP aircraft flying search grids, or simple mistaken artifacts of old images. Additionally, psychics flooded the search base in Minden with predictions of where the aviator could be found. Ryan got the majority of these calls personally, often at her home, in the middle of the night. One man from Canada was particularly persistent with daily calls to Ryan, interfering with her press briefings. Ryan requested her Incident Commander to issue a 'cease and desist' request, backed up by the RCMP if necessary. Ryan noted that all the 'crowdsource' emails, phone calls and mail was taken seriously - which added to the burden by USAF specialists who were brought in specifically to address that task - and that each was reviewed no matter how outrageous they may have seemed at first glance. In retrospect, the 'crowdsource' effort was "not ready for prime time" according to Maj Ryan

[jcjeant]

Hi,

JD-EE, it's theoretically do-able but perhaps culturally impossible. The world-wide culture of such investigations is more accustomed to locked hangars, yellow do-not-cross tape, tightly controlled evidence, very expert input, and very careful deliberation. Not a bad culture, mind you, just one unused to the public eye or, what would be perhaps more disconcerting, to public participation.
Just a remind
Mind you it is associations of the victims families and they requested (and continue to request) to have a observator from the associations for be part (as observator only) of the investigation processus.
The BEA (I think by the mouth of the french transport minister Bussereau) give them a hard refusal.
So you can allway dream to have a bit of data from the BEA :)

[auv-ee]

This brings to mind the many eyes approach several groups are using to find interesting bits in huge volumes of data. If the bottom profiles were released to the public for processing and scrutiny both the state of the art and the chance of discovery of "bits" in large amounts of data improve.

This is a great idea, except that I'm concerned that it would not produce useful results. In sidescan sonar records, a lot of things may stand out as targets, and may even have angular shapes that look like man made objects, but when investigated, they turn out to be rocks. If there were any large parts (wings, fuselage section, etc.) they would likely have been spotted by the eyes that already looked at the data. Even if there might be smaller parts in the data, the number of "false alarms" generated by inexperienced eyes would likely swamp any ability to investigate or even discard them.

I expect that the searchers are looking for patterns of targets that might be different from the surrounding rock fields. They likely got their local experience by investigating some of the early clusters and discovering they were rocks. We know that the ROV was used to investigate some targets. It seems likely that they learned what not to waste time on. That sort of knowledge is difficult to pass on. (Of course the flip side is that something ignored could have been debris.)

This search is not like the Fossett search, where color images can be scanned for white metal objects in a desert setting. The sonar images are composed of just varying reflection strength. While it's not as bad as looking at long range radar data that is just little blips and clutter, in some ways it is more like that than looking at a photo.

Perhaps someone will comment who has more experience than me in reading high clutter sidescan images.

[auv-ee]

jimbeetle wrote:

The oil industry has a fleet of ROVs like the 12 that are working on the Gulf spill. They're working at just shy of a mile down now. Is that their limit, or can they work deep enough to be effective at the AF-447 site?That depends. There are a number of ROVs world wide that are capable of operating at 6000m or 6500m. Only 2% of the ocean is deeper than 6000m, so a design depth of 6000m is often considered "full ocean depth". The deepest point in the ocean is 11000m at the Challenger Deep in the Mariana Trench. There is one (new) ROV/AUV (hybrid, dual mode) capable of reaching 11000m.

But you asked about the ROVs working in the Gulf. I don't know what their range of depth ratings is, though it's likely that others posting here know. It adds some expense to design for a greater depth than needed, so those ROVs might be limited to the depths being explored for oil around the world, or just the depths in the Gulf of Mexico. I would not be surprised if some of them are 6000m rated.

I realize that they're tethered and that would probably add more difficulty. Anything insurmountable?Difficult: yes. Insurmountable, no. There have been deep ROVs for 20 years or more.

I guess I've been thinking along the lines of a couple of ships controlling a handful of these each for a very deliberate visual search that, if nothing else might rule out areas.The search rate for ROVs is very low compared to other tools available. At this point the AF447 search needs to cover a wide area. The best visual range I have seen in the deep ocean is 20m, and 10-15m is more common. That limits a visual swath to about 30m, and at 1knot max transit speed, that covers about 1sq-km/day. The BEA site lists 5sq-km/day search rate for the ROVs they had, but that is likely using the ROV's sonar, not its cameras.

Also, ship time is one of the largest cost factors, so minimizing the number of ships is important. I'm not sure what the state of the art is for number of ROVs from one ship; I'm sure it depends on operating depth and other conditions. I have never seen more than one per ship, because of the difficulty of entanglement, but I expect that they are doing more than that at the oil spill site. Some differences there: the depth is "only" 1500m, and the ships are standing still or moving very slowly.

[HazelNuts39]

auv-ee,

My hope for retrieving the boxes still rests mainly on Emeraude's recordings. Some time ago I asked, if two pingers rest on the ocean floor with some distance between them, whether that distance would help to locate them. I wasn't thinking about doppler shift, but perhaps I wasn't successful in making myself clear. This sketch explains my thinking:

Sub and pingers (https://docs.google.com/leaf?id=0B0CqniOzW0rjYjZlOGQ1NzgtNzY4NS00YmU2LTgzNzctZTBlY2N lNThlMDMx&hl=en_GB)

Assuming that both pingers emit a pulse at the same time, the sub in position (1) would receive the pulse emitted by pinger B slightly earlier than that of pinger A. The time shift between the received pulses A and B would change in different positions of the sub relative to the pingers, would it not?

Regards,
HN39

[auv-ee]

Assuming that both pingers emit a pulse at the same time, the sub in position (1) would receive the pulse emitted by pinger B slightly earlier than that of pinger A. The time shift between the received pulses A and B would change in different positions of the sub relative to the pingers, would it not?

Well, off hand, I don't see how. The pingers won't emit at the same time, because they are independent devices. We had a long and inconclusive discussion about whether the oscillators are crystal controlled, or not. Even if they are, the pingers will have random and slowly changing time shift; if they are not they will have rapidly changing shift.

I am just hoping that Emeraude really heard anything at all. There seems to still be uncertainty about that.

[CONF iture]

Added to that both Airbus/Air France recommended turbulence penetration mode is Autothrottles OFF while AF447 A/T was kicked OFF by systems at 02.10, consequently, she was certainly not in turbulence penetration mode/speed until this point. Moreover, at 02.10, more than half of the CB system was already crossed, they were not just penetrating it.
Actually, in that perpetual push to make maximum use of automatism, it is not written anywhere in the Airbus documentation to pre-emptively disconnect the A/THR before entering a suspected area of turbulence, maybe it is in the AF documentation ?
The Airbus recommendation to disconnect A/THR applies if severe turbulence is already encountered and only when thrust changes become excessive as per QRH.

Which explains why they stated the turbulence penetration speed was M0.78 instead of M0.80 in the A330.
Just to clarify, the recommended speed for severe turbulence for a A330-200 at FL350 is 260 knots IAS which is for reference slightly below Mach.78
But the BBC program mention of Mach.76 is effectively also inexact.

[sensor_validation]

Flight plan was for M 0.82
Fin Rudder limit suggests M 0.80 when A/P disconnected

Does that mean speed was in transition?

[bearfoil]

Or altitude.

[jimbeetle]

Thanks for taking the time to answer my questions, auv-ee. It's great to have go-to folks to help explain all this arcane stuff.

the depth is "only" 1500m
Yeah, absolutely crazy. I found the bit of the feed I watched from the Gulf absolutely fascinating. But still having a very hard time wrapping my head around the depths that have to be dealt with at the AF-447 site.

[tubby linton]

But the BBC program mention of Mach.76 is effectively also inexact
That is because it was the CTC A320 sim!

[CONF iture]

But the BBC program mention of Mach.76 is effectively also inexact
That is because it was the CTC A320 sim!
It is a bit like tricking the figures to better fit the theory.


Did I hear it correctly around minute 18 ?
Several other flights took the same route as AF447, but all these pilots saw the storm coming and made detours of about 90 miles to avoid it.
As the BEA, the BBC wants to make people think AF447 was the only one to fly through the red area ...

[BOAC]

As the BEA, the BBC wants to make people think AF447 was the only one to fly through the red area - maybe they have been misled by some of the 'expert' postings here?:mad:

[HarryMann]

It is a bit like tricking the figures to better fit the theory.

Not really, a documentary like that is aimed simply at getting the idea across about what may have gone wrong/happened and why. Exact figures and exact simulation affects not one jot the theory on causation they were putting forward...

Suffice to say that the expected slowing down for turb.penetration may have had further consequences when the A/THR disconnected?

[overthewing]

I thought it was a well-balanced documentary which did a good job of getting across some complex technical concepts. Presumably they made use of a 320 sim because that was the closest type they could get hold of within their timescale? At least they didn't use a Boeing cockpit!

With regard to their statement that AF447 was the only flight to go straight through the stormband, I actually thought that was reasonably close to the facts as they emerged at the time? Other flights seem to have picked their way between bad areas, and I seem to recall at least one other pilot expressing surprise at the route followed by AF447, going by their reported track.

There was also a lot of discussion here about using weather radar. I thought the program made rather less of that than I would have expected.

[aguadalte]

My apologies if this was already posted:
Flight Paths of Flight AF 447 and of the flights that crossed the zone around the same time (http://www.bea.aero/en/enquetes/flight.af.447/trajectoires/trajectoires010609.html)

[soph_co]

Hello,

Been reading posts here for months with interest, not posting so far as not a professional pilot/crewmember.

Some additional info on who went through the storm (thanks Agualdate) :
El Al flight ELY010 on the route UN886 went straight through (at least from available info) while other flights displayed on the same route made a deviation AF401/ KLM792/AF415
(Trajectoires du vol AF447 et des autres vols ayant parcouru la zone dans la même période de temps (http://www.bea.aero/fr/enquetes/vol.af.447/trajectoires/trajectoires010609.html))

I wish I could find the comments of the El Al pilot on his flight conditions since he seems to have made the same kind of decision as the AF447 pilot. If someone has a source I would be more than interested btw...

I always wondered at this since to me understanding this choice is key in the process.

[SaturnV]

CONFiture

On the same route that night, LH507 preceded AF447 by 20 minutes; deviated west pf the track by 10 NM

IB6024 followed AF447 by 12 minutes; deviated 30 NM to the east.

AF459 followed AF447 by 37 minutes; initially deviated 20 NM to the west of the track, then deviated 70-80 NM to the east of the track.

[JD-EE]

GreatBear, re the many eyes approach, search for "astronomical "green pea"" without the outer quotes. This was an astronomical many eyes project result. They found a brand new type of object in the heavens because some one observer noticed something odd.

Amateurs does not mean inexperienced or ignorant garage mechanic. It more often means a dedicated practitioner with an excess of experience whether or not the education is there. It's an important technique.

If they open the database and its formats they can post the word to slashdot. That will result in an utterly overwhelming number of eyes, I am sure. Add a modest reward and some 15 minutes of fame to the mix and it'll be impossible to chase them away. If anything is there to find, it will be found.

{^_-}

[JD-EE]

jimbeetle, look for "Oceaneering" and "Perry Slingsby Systems". Both make ROVs good down to some 2000-4000 meters. I'm sure there are others. These two seem to be the ones in use at the BP site.

{^_^}

[JD-EE]

auv-ee
May I add to your remarks that ROVs are somewhat limited. They do not (usually?) work from a direct tether to the surface ship. They are lowered in a cage and turned loose with a tether back to their transit cage. The tether's length is limited. So their ability to move along in a search is limited. They'd have to search an area and come back to their cage to be moved to the next block lest cords get tangled.

They're ideal for working on drilling rigs. For wide area searches they would seem, to me, to be somewhat limited. (And I wonder when they will grow binocular vision.)

{^_^}

[SaturnV]

soph_co, the El Al flight was on a different track, In that BEA interactive, only AF459 is on the same INTOL-SALPU-ORARO-TASIL route as AF447.

This interactive graphic was discussed on this board after the second interim report came out, including speculation on why the BEA did not include the tracks of the IB and LH planes flying the same track as AF447.

There is some belief that the Lufthansa flight was the plane that the BEA references as being equipped with AMDAR, so a plot of its track and corresponding meteorological soundings would be interesting. And which may be why the precise LH track is not being released at this time. Similarly, the transcripts of communications between controllers at ATLANTICO and other planes on this route regarding weather conditions that night have yet to be released, although the communication between AF459 and ATLANTICO regarding the extent of its deviation is mentioned.

[keitaidenwa]

Crowdsourcing is a good option to consider, but only once professional people have gone through the sidescan sonar material to no avail. Keeping the data hidden after official investigators have given up wil only inspire conspiracy theorists. But lessons from the Fosset crowdsourced search must be taken in account:

1. Users need to trained before giving access to data - make them go through a online course of identifying various objects from sonar scan results.

2. Have *all* data available - debris findings and time, sound recordings from phase 1, etc.. Some people might find creative ways of combining data.

3. Make the reporting path non-intrusive. Instead of calling the investigators just click online of objects of possible interest, write a report of what you think you are seeing and let others comment on the credibility of finding.

Even if the crowd doesn't find AF447, one would presume something of scientific interest would be found. After all these seabeds are still not very well studied.

[bearfoil]

With all due respect, this is a proprietary investigation. It is cloistered and corporate; it is not a democracy. I don't disagree with this format, it is no different than virtually every other Aviation accident exploration.

ACARS was a gift, most likely from someone who is now unemployed, or worse.

My hope is that given the tyrranical nature of the work, people do not lose interest in 447.

[CONF iture]

So let’s stop pretending getting the simple truth, when actually, it is all about damage control or how to spare everyone.
The BBC documentary has no other aim than formatting the general public mind and if a few lies can help why not ...

[TiiberiusKirk]

GPS may only know Ground Speed, but isn't it true that some function of GS, Engine power and Pitch = Air Speed
f(Ground Speed, Thrust, Pitch)= Air Speed ?
GPS plus the other knowns could thus provide a pitot cross-check or alternative measure.

[bearfoil]

Why no Alvin? Three crew, 6 MkX eyeballs, 15,000 foot depth, no decompressing, visual (camera) recording, etc. She's 46 years old, but she found Titanic.

She works quickly. Just not cheaply.

bear

[mm43]

TiiberiusKirk

KTAS (True Air Speed), i.e. the speed the aircraft is actually travelling through an air mass, has nothing in common with the GS (Ground Speed). Consider an aircraft with 250 KTAS and a tail wind of 100 KTS. It will have a GS of 350KTS, and likewise 150KTS if it was pushing a 100KT head wind.

The aircraft performs relative to the airmass which it is in.

mm43

[auv-ee]

Why no Alvin? Three crew, 6 MkX eyeballs, 15,000 foot depth, no decompressing, visual (camera) recording, etc. She's 46 years old, but she found Titanic.

She works quickly. Just not cheaply.

Alvin was not used to find the Titanic. Titanic was found with towed side-scan and towed down-looking cameras (and by a ship based bottom sounder and a magnetometer, according to PH Nargeolet). Alvin visited for a detailed exploration in 1986, the year after the initial discovery.

Alvin is even more limited than an ROV for wide area search. It moves at 1-2knts, and can only stay on the bottom 6-10 hours out of 24. The shorter time applying to dives with long transits, like searching.

[HarryMann]

There was also a lot of discussion here about using weather radar. I thought the program made rather less of that than I would have expected.

Agree too... maybe because they theorised that until it was too lat, the view in-use showed short-range weather blocking what was behind, so didn't want to suggest other reasons the Wx radar might have misled.

[HazelNuts39]

the view in-use showed short-range weather blocking what was behind,
I didn't quite understand that part of the BBC story. Wouldn't the pilot try to avoid the weather in-sight, and thereby also what's behind?

HN39

[SaturnV]

HN38, three cabin crew seats were recovered, two from the area of left hand door 1, and one from the area of right hand door 2. The BEA stated none of the seats was occupied at the time of impact. There were nine cabin crew on the flight, there were 11 cabin crew seats. At least one of the cabin crew was not in his or her seat.

Bodies of four cabin crew, including the body of an "in-charge" flight attendant, were recovered and autopsied, as was the body of the captain. The BEA notes that the location of the captain on the aircraft cannot be determined from the autopsy results. There is no separate characterization of the autopsy results for the four cabin crew.

On can infer (but not conclude) from the unoccupied seats that there was no command for the cabin crew to be seated because of weather ahead. From the transcript of the communication between ATLANTICO and AF447, the crew did not make any inquiries about the weather. As the BEA has yet to release a transcript of the communication between the Lufthansa flight flying ahead (which deviated from the track) and ATLANTICO, we do not know what was said regarding this, and whether AF447 might have overheard if they were monitoring the frequency.

What should one expect with regard to preparing for meteorological conditions ahead when flying into a SIGMET area, and alerted by dispatch while enroute of convection in the vicinity of TASIL?

The captain had 16 rotations on the South American sector since 2007, 1.093 flying hours on the A330.

The co-pilot had 39 rotations on the South American sector since 2002, and had 1,882 flying hours on the A330.

The second co-pilot had five rotations on the South American sector since 2008, and 216 flying hours on the A330.

Their collective experience on these rotations with regard to conditions in the ITCZ, e.g., whether these rotations were mainly during January or July, is not given.

[FlexibleResponse]

TiiberiusKirk

KTAS (True Air Speed), i.e. the speed the aircraft is actually travelling through an air mass, has nothing in common with the GS (Ground Speed). Consider an aircraft with 250 KTAS and a tail wind of 100 KTS. It will have a GS of 350KTS, and likewise 150KTS if it was pushing a 100KT head wind.

The aircraft performs relative to the airmass which it is in.

mm43

Actually TiiberiusKirk makes a good point. GPS knows accelerations which integrated provide speed and the again provide distance in all axis. GPS routinely provides wind and true speed and direction and distance and thereby navigation information.

It would not be much of a stretch for GPS to be programmed to provide synthetic pressure altitude (as opposed to GPS alt) and also synthetic calibrated airspeed. This data could easily be compared to the triple air data sources that are measured by the pitot probes and static pressure sensors for validation.

I suspect that this or a very similar system will be part of the next gen aircraft.

Edit: Hazlenuts39 is correct (see next post). I used the term GPS when I meant to use IRS. IRS of course uses accelerations and integrates to achieve calculation of velocity and distance to give position. GPS of course knows position and works backwards to calculate velocities.

I still think it is merely an engineering problem to work a solution to provide synthetic airspeed and pressure altitude using normal air data and IRS/GPS information in conjunction to provide an alternative source of reliable data when an input sensor system is completely eliminated on a temporary basis (icing of all probes for example).

[HazelNuts39]

GPS routinely provides wind and true speed and direction and distance and thereby navigation information.Any question in this area should, first of all, distinguish between avigation and navigation.

For navigation, GPS does not add very much to IRS. The pros and cons of GPS versus IRS have been discussed earlier on this thread. GPS does not provide wind. The airplane computers (ADIRU or FMS?) derive wind by comparing groundspeed to airspeed.

However, the first priority after loss of airspeed indication is to keep flying. Pitch and power should keep airspeed and altitude within safe limits. Groundspeed isn't needed immediately, but could perhaps help in the longer term if the pilot knows what groundspeed he had prior to the loss of airspeed indication.

Why is GPS or IRS groundspeed no substitute for airspeed? The liftforce that keeps the airplane flying is the result of aerodynamic pressures around the wing. These pressures are directly related to the pressures measured by the pitot/static system. In fact, the needle of a pneumatic ASI indicates the dynamic pressure directly, only the scale markings on the dial behind it are 'calibrated' in airspeed units.

EDIT:: Similarly pressure altitude = static pressure. To 'synthesize' pressure altitude from GPS height, the computer needs to know the pressure at sealevel, and the temperature profile between sealevel and flight altitude.

HN39

[HazelNuts39]

SaturnV;

thank you for the information from the BEA reports. Perhaps I did not explain my question very well, so let me rephrase it:
Is there any merit in the BBC claim to have solved (part of) the mystery of AF447, with the theory of an NOAA meteorologist that a small convective cell may have hidden the 'big' one behind it on the Wx radar screen? Wouldn't the crew have avoided the small cell, and thereby the one behind?

HN39

[steamchicken]

I'm quite dubious about crowdsourcing in the pure sense, because the problem is too much like screening bags - people aren't very good at detecting significant rare events in a large number of insignificant ones. Further, as a lot of the seabed is going to be quite different oceanographically, most of the variation in it will be rocks and the reviewers will lock on to the rocks because they're what's available (anchoring; target fixation).


But there might be some role for it as part of a semiautomatic process - for example, if some kind of statistical model has thrown up x number of probables, there could be value in having the crowd work through them, as the targets probably aren't very amenable to automatic detection. If we were looking for the fin, for example, that would have some nicely defined corners, but we're looking for "stuff that looks engineered, but has been smashed" and that's quite subjective.

There are some interesting methodologies for this sort of thing; one would be pairwise comparison (a.k.a kittenwar). Rather than "is there an aeroplane here?" or worse "here are 100 very similar sonar images, can you spot a piece of wreckage?", this presents the user with 2 randomly selected probables and asks them to pick one - eventually, you should end up with the images sorted by the totality of the users' preferences, which should be a valid Bayesian search. There's a more formal version called the Analytical Hierarchy Process, where you make the pairwise comparison on the basis of parameters you choose in advance.

As well as kittenwar and Am I Hot Or Not, this has been used for quite a few hard problems - like examining British politicians' expenses claims, and making technology decisions in big companies.

Alternatively, if you were trying to build a statistical method of identifying targets on the seabed, you might use something similar to classify the seabed into different topographies, or to confirm that a zone was clear of wreckage so that you could use it to calibrate the model.

Depending how self-similar the seabed topography is at the relevant scale, it might be possible to use a Fourier analysis to compare similar areas of seabed - the answer to my assumption looks to be "not very", but it might be possible to classify it into relatively self-similar zones.

[aguadalte]

HN39:
Is there any merit in the BBC claim to have solved (part of) the mystery of AF447, with the theory of an NOAA meteorologist that a small convective cell may have hidden the 'big' one behind it on the Wx radar screen? Wouldn't the crew have avoided the small cell, and thereby the one behind?In fact, this is not knew to us. We all know that a smaller cell, may hide a bigger one. Sometimes, this smaller cell, may appear to the crew, as not threatening the path we are flying. However, when the radar gets a first cell, and if it appears to be "blocking" the "view", the radar will display a continuous solid band at the further end of that same display, as wider as the shadowed angle, to alert pilots for that possibility.

[JD-EE]

Actually TiiberiusKirk makes a good point. GPS knows accelerations which integrated provide speed and the again provide distance in all axis. GPS routinely provides wind and true speed and direction and distance and thereby navigation information.

GPS does not track accelerations. It is a tool for calculating positions. Differentiating position with respect to time gives velocity to relatively poor resolution. Differentiating velocity with respect to time gives acceleration "sort of". The intertial units provide the acceleration. Neither directly gives velocity. Both GPS and the intertial units are combined with other data sources in Kalman filters to give reasonably good estimates of position, velocity, and acceleration.

None of them know squat about the surrounding air mass.

{^_^}

[auv-ee]

It seems that an alternative air speed measurement is needed to augment the pitot tubes, something that would be affected differently by environmental effects and other failure modes. I'm not suggesting replacing pitot tubes, because that would just introduce a different, but still single, failure mode, rather than introducing redundancy. What comes to mind is Doppler measurement of back-scattered energy, either EM or acoustic. A quick search reveals that an optical version of this is already being developed in the UK (though they seem to want to replace pitot tubes):

Emerald: Article Request - New optical airspeed sensor poised to cut airline costs (http://www.emeraldinsight.com/Insight/viewContentItem.do;jsessionid=5831B14D551F3A3F5AD7A919CE52BB FF?contentType=Article&hdAction=lnkhtml&contentId=1464085)

Likely other groups are working on this also.

[BOAC]

Not a lot of use when it is IAS you need.

[auv-ee]

Not a lot of use when it is IAS you need.

If you are responding to the use of Doppler measurement for air speed, that is an excellent point. It would be necessary to measure air density to go along with the velocity measurement. I don't know how the UK team plans to do that, though it could be derived from temperature, static pressure and humidity (any other significant factors?).

[bearfoil]

Redundancy is a siren on the rocks when one is up against common fault. BA038 had redundancy, but at some stage a system must be parallel, hence the dual rollback. The closer the rubber gets to the road, a system folds into unity, up only against the odds.

Unreliable airspeed became common on this type, hence the acronym, and the training focus. Because three separate pitot static systems generate discrepant airspeeds does NOT necessarily mean they have all iced, together or in some aberrant sequence.

Sailing in the doldrums one experiences no "wind". The mass is expanding around you and rising. Slowly at first, then as this warmth gains altitude, it increases in velocity.

Had 447 entered the mother of all cells? Most likely not. An average one will do nicely relative to upset and airspeeds that rocket up and down. Was any of the Alert/warning/alarm prompts singled out and addressed/cured? Shall we use the RTLU as an impromptu altimeter, by its demonstrated limit after falling out of the sky? The fuselage of the 330 is massive, and the pitots are well away from each other. This attacks the theory of Ice/turbulence, and entertains the discrepant/local theory. 1/2, 1/3, 2/3? Look at the numbering of the Tubes and the ACARS.

Again the autopsies are mentioned. The Captain's remains do not suggest a position in the a/c. Neither do the other peoples' remains who are of necessity assumed to be unseated, mobile, and not just at impact. Specifics of trauma are limited to the determination by BEA that these were seated. Belted? An easy conclusion given the facts? Evidently not. I say again the trauma focussed on by BEA is patent in trauma exhibited by human beings in CAT or upset historically; in this case the posture of each victim is concluded to be known. Mistake?

[SaturnV]

HN39,
Perhaps more a function on how the radar was being used and less on whether cells were being hidden. From the first BEA interim report,

Flight AF459 (Airbus A330-203) passed at the level of the ORARO waypoint approximately 37 minutes after l’AF447. The sky was clear but the half-moon, visible to the aft left of the aircraft, did not make it possible to see the contour of the cloud mass distinctly. After flying through a turbulent zone in the head of a cumulus congestus formation at the level of NATAL, without having detected this zone on the radar, he selected gain in MAX mode. At about 2 h 00, he observed a first echo that differed significantly depending on whether the radar’s gain was in CAL or MAX mode. The TILT was set between -1° and 1.5°. He decided to take evasive action to the west, which resulted in a deviation of 20 NM to the left of the route. During this evasive action, a vast squall line with an estimated length of 150 NM appeared on the screen, which was set to a scale of 160 NM. The echoes were yellow and red when the radar was set with gain on the MAX position and green and yellow when the gain was on the CAL position. No lightning was observed.

ATLANTICO control, informed by the crew of their decision to avoid this squall line by taking evasive action to the east, asked them to return to the airway as soon as they could. This evasive action meant the aircraft flew between 70 and 80 NM to the right of the planned route. In addition, the crew was authorised to climb from FL350 to FL370.

Similar narrative detail is not provided for the actions of the pilots on the Iberia and Lufthansa flights, who also deviated.

bearfoil, there were 50 bodies identified through autopsy. The second interim BEA report says this:
Forty-three of the victims had fractures of the spinal column, the thorax and the pelvis. The fractures described were located mainly at the level of the transition vertebrae. The compression fractures of the spinal column associated with the fractures of the pelvis(2), observed on passengers seated throughout the cabin, are compatible with the effect, on a seated person, of high acceleration whose component in the axis of the spinal column is oriented upwards through the pelvis.
(2) Fractures of the pelvis can also be associated with the wearing of a seat belt.

Whether from deliberate or imprecise phrasing, the above language read literally suggests the 43 victims so described were passengers, with the results of the five crew autopsies omitted.

[syseng68k]

JD-EE,

That might need a little clarification. http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/confused.gif

While gps is primarily a system to calculate position, it can also be used to provide fairly accurate heading and ground speed data, in conjunction with appropriate software.

For example, if gps position is sampled at a constant, known rate, it only needs a bit of trig to calculate heading and for ground speed, a bit of arithmetic using sample rate (time) and change in position + scale accordingly. Not exactly rocket science.

Of course, ground speed != air speed, but in a typical flight, with small changes in wind force and direction, there would be a measurable relationship between the two, which could be used as an added data input to the various system filters. It may be "poor quality data", but still usable within it's limitations...

Regards,

Chris

[ettore]

Just an idea, or two...:

Could variations of the air flow, measured at the engine's intake at a given rpm, give a clue about pitots' malfunction ?

Would air speed measurments at the engine intake, compared against the tremendous engine's thrust, be reliable ?

Sorry, I'm not an engineer... :{

[infrequentflyer789]

It seems that an alternative air speed measurement is needed to augment the pitot tubes, something that would be affected differently by environmental effects and other failure modes.

Already exists - BUSS. Not fitted on AF airbuses. There seem to be some widely varying opinions of how well it works. AF rationale for not fitting it is here:

Air France - Corporate : The BUSS or "Backup Speed Scale" (http://corporate.airfrance.com/en/press/af447/the-buss-or-backup-speed-scale/)

I believe BUSS is standard on A380, where it was optional on earlier models.

[voltage]

Preface: I have 250H+ TT and study for my ATPL exams at the moment.

syseng68,

I can tell you from my limited experience that it would not be very useful. The relationship between TAS and GPS GS would be the wind, and then between IAS and TAS temperature, ambient pressure, altitude and humidity.

The only way to know the wind vector is to compare GPS vector with airspeed and heading information. If you have lost airspeed, you have lost all information about winds.

Winds do change, especially around convective activity. If the margin between stall and overspeed is small, GPS groundspeed is just about useless.

In my opinion, using optics or engine pressure readings sounds more promising as an ASI backup, because it tries to *measure* airspeed rather than deduce it.

[sensor_validation]

One for the conspiracy theorists:-

When the 1st BEA interim report was issued on 2nd July 2009 the English language version was only 72 pages long, it didn't have all the appendices in the French version. The version with the same filename f-cp090601e1.en.pdf (created 28th July 2009) now on the BEA website is complete and is 128 pages long, but doesn't include the exact final position ACARS message, which is in the earlier version

2:10:34 #0210/+2.98-30.59This is the same location described elsewhere, but was it removed because

a) They missed the fact that this position was slightly off-track (see takata post earlier re eurocockpit analysis)

or

b) The position is more likely to be @2:10:30 (higher priority messages inserted into sequence), which puts it some 20 seconds or so after the cascade of errors started, not just before. I'm pretty sure mm43 posted before about positions quoted at half-minutes, but maybe that was based on Brazilian Air Force extrapolation data - they also had a position at 02:14z.

or

c) It just wasn't supposed to be there in the first place (wasn't in the first TV leak),

Can't say its very important, but I was sure I'd seen the #02:10 position report, but no obvious revision marks to the document...

For all the AF447 positions from 00:10 in ACARS 2 dp precision use in

Flight Paths of Flight AF 447 and of the flights that crossed the zone around the same time (http://www.bea.aero/en/enquetes/flight.af.447/trajectoires/trajectoires010609.html)

see

http://www.bea.aero/en/enquetes/flight.af.447/trajectoires/data/AF447.txt

[auv-ee]

It seems that an alternative air speed measurement is needed to augment the pitot tubes, something that would be affected differently by environmental effects and other failure modes.
Already exists - BUSS. Not fitted on AF airbuses.

The description of BUSS does not make it sound very appealing. I was thinking of something that would be a precise speed measurement, as valid as the pitots, a few of which would provide more inputs to the voting logic and the Kalman filter.

Redundancy is a siren on the rocks when one is up against common fault.

The idea is to add a speed sensor based on different physics that would not be subject to the same failure modes as pitots. I agree about "parallel" redundancy, like multiple pitots, where a common fault is possible, or the case of "series" redundancy where the pre-existing failure of a backup is not evident until the primary fails (double pressure seals come to mind).

[auv-ee]

[ROVs] are lowered in a cage and turned loose with a tether back to their transit cage. The tether's length is limited. So their ability to move along in a search is limited. They'd have to search an area and come back to their cage to be moved to the next block lest cords get tangled.

Agreed that the cage or depressor weight (2-body launch and recovery) is the usual configuration for a deep ROV. However, it is not so that the ROV has to return to the cage to move the ship. When the ship moves, additional scope must be payed out from the ship to keep the depressor at the right altitude, and the ROV can tow its neutral tether as the depressor moves. When the ship stops, the additional scope is retrieved as the depressor settles under the ship. With a rough bottom, it is necessary to ensure that the neutral tether is not dragging on the bottom, lest it fetch up on something. I don't know if this is attempted with more than one ROV/ship; that would surely be more tricky. Agreed though, for reasons already discussed, that ROVs are not the right tool for a wide area survey.

[HarryMann]

Alternative Air speed sensor
Hot-wire anemometer, hot film anemometer? Would need a filtered air feed (which might ice uip, unless it was designed like a Dyson bagless vacuum), but they last for ages in windtunnels and engine Air Flow Meters
With temp can give dyamic head fairly well I believe (Ptot)

[alexd10]

Hello!

Maybe I am missing something, but since airspeed is essentialy neded for assesment of the lift produced by the wings, would'nt be more straightforward to measure/calculate the lift? It should be possible at least by measurement of the stresses in the wing structure. Or by measurement of the pressure on a section of the wing and by integrating the pressure on that closed curve.
Had anybody heard of such an approach?

[HazelNuts39]

Would air speed measurments at the engine intake, compared against the tremendous engine's thrust, be reliable ?Not a bad idea at all. Very likely each engine has its own probes for measuring intake total pressure P1 and intake total temperature T1, which are used by the engine electronic control system (FADEC). The difference between Pitot pressure and P1 is engine intake total pressure loss, which is quite small in cruise. I don't know if the engine's P1 probes have ever experienced similar icing problems as the airplane's pitots.

HN39

[JD-EE]

While gps is primarily a system to calculate position, it can also be used to provide fairly accurate heading and ground speed data, in conjunction with appropriate software.

With processing accelerometers provide you with distance covered despite their primary data being acceleration. Similarly you can differentiate GPS location (and time) information to get velocity and a second differentiation gives acceleration.

Note that with GPS you are differencing two quantities that have significant error dimensions relative to the difference obtained. So the error band on velocity is large. The error band on acceleration is even larger.

I have a pair of GPS receivers a few feet to my right. They are for precision time keeping rather than navigation. But I note the wandering of their time signals relative to each other with stationary antennas. "A few feet" is the translation I get on errors at about 1ns per foot. (That is accurate within a three percent.) If a plane is proceeding at a ground speed of say 300mph that's about (mumble 88*6 feet per second or about 440'/second.. If you take a reading once a second you have a speed range of perhaps 430'/second or 293 MPH to 450'/second or about 307 MPH. That may be accurate enough if the plane is not in distress. If the plane's dynamics change on a second by second basis, as with turbulence, it might not tell you quite as much. At a tenth second you have 23% error bands without some smoothing rather than 2.3%.

I'm not sure what speed accuracy is needed for being happy within a cockpit. I suspect 2% is acceptable and 10% is not. GPS is perhaps marginal. Over a 10 second interval GPS velocity determination is, of course, much better than my bogey numbers.

Another detail to remember, if you are dealing with high dynamics or simply high speeds, is that GPS tells you where you were at the time of measurement not where you are at the time you read it. To the extent that the distance traveled during that interval matters this detail is important to keep in mind. Fortunately the various filters in the system "take up the slack" on this detail.

She knows more about GPS than she would like to bother with. You guys have, for more than a couple decades, been relying on some work I performed while at Rockwell International in Anaheim on the satellites as designed in the late 70s. At that time it was a pasttime of mine to "annoy" AF officers over their silly "dithering" pointing out differential techniques render it pretty much moot. It does provide a nice way to gain precision from the oscillators, though.

[JD-EE]

auv-ee
I was concerned with that towing scenario and potentially snagging the ROV to cage tether on rocks given the mountainous terrain.

{^_^}

[BOAC]

All this techno-babble about GPS/INS etc. All we need are:

1) Multiple (3?) probes with adequate heating

2) Instruments which provide basic attitude and engine settings WITH NO COMPUTER INTERFACE for use in any failure of 1)

3) Crews trained to use 2) if 1) happens.

So simple.:ugh:

[auv-ee]

auv-ee
I was concerned with that towing scenario and potentially snagging the ROV to cage tether on rocks given the mountainous terrain.

It's all about situational awareness. With lights, cameras and maybe an altimeter (acoustic range to bottom) on the cage/depressor, this can be done. Remember that 1knt is only 0.5m/sec horizontally, and the winch rate is typically 1-1.5m/sec; it's manageable. Doing this depends on the tools available to the operator (tether management between depressor and ROV, adequate visibility, ...), the operator's skill, and the severity of the terrain/currents. Certainly there are times and places where the ship can move with the ROV deployed, and others where it cannot.

[gums]

Salute!

Thank you, BOAC. Well said, IMHO.

The current crop of "Playstation" pilots and crew are beginning to scare me.

Fer chrissakes, point the plane best you can using the ADI or stby gyro and keep power where it would normally be. NO AUTOPILOT in turbulence. Let the jet fly as it was designed to and she'll prolly do just fine.

Seems we had a "bus" Delta crew with a loss of IAS and such and they did just fine holding attitude and normal power setting ( inbd to Tokyo?). Sheesh

Gums sends ...

[bearfoil]

Can't fly pitch and power w/o AH and throttles, though. The AH is an option, only luddites would want one.

bear

[FlexibleResponse]

engine P1
Quote:
Originally Posted by ettore
Would air speed measurments at the engine intake, compared against the tremendous engine's thrust, be reliable ?
Not a bad idea at all. Very likely each engine has its own probes for measuring intake total pressure P1 and intake total temperature T1, which are used by the engine electronic control system (FADEC). The difference between Pitot pressure and P1 is engine intake total pressure loss, which is quite small in cruise. I don't know if the engine's P1 probes have ever experienced similar icing problems as the airplane's pitots.

HN39

Yes the engine probes in the A330 fitted with Roller engines did suffer this problem. RR engines have a P1 probe to measure pressure ratio as the thrust is measured as EPR.

Quite a few years back I had a pax visit to the fight deck of my A330 and who was an engineer from RR Derby. I (actually the a/c) was able to demonstrate this problem as we negotiated TS's over the Philippines and each engine was affected in turn by icing as the supercooled water at cruise altitude exceeded the heating capability of the probes. The effect of the icing of the P1 probes was to reduce maximum allowable EPR (blue triangle in the EPR gauge) in each engine as it was affected by icing. The RR man was excited to access the data from the MCDU (under supervision of course).

I subsequently learned that RR first knew of this problem from experience on the B747-400 but they were reasonably unconcerned as the consequential P1 error from icing was temporary in time and reduced the max allowable EPR and therefore was considered to be safe.

[auv-ee]

BEA has updated their Phase 3 Search page to briefly describe the results of the search. I don't see any new information, other than an updated search coverage map.

Sea Search Operations (http://www.bea.aero/en/enquetes/flight.af.447/sea.search.ops.phase.3.php)

[MurphyWasRight]

Quote:
engine P1
Quote:
Originally Posted by ettore
Would air speed measurments at the engine intake, compared against the tremendous engine's thrust, be reliable ?
Not a bad idea at all. Very likely each engine has its own probes for measuring intake total pressure P1 and intake total temperature T1, which are used by the engine electronic control system (FADEC). The difference between Pitot pressure and P1 is engine intake total pressure loss, which is quite small in cruise. I don't know if the engine's P1 probes have ever experienced similar icing problems as the airplane's pitots.

HN39


Given that the need for true backup airspeed is rare here is another possible option:

Deploy the RAT (ram air turbine) emergency generator and use the RPM and generated power to compute air speed.

This would also require air temperature and static pressure for decent accuracy, although even without those a usable estimate might be possible.

I don't know if this is at all practical (max speed etc) but it would certainly be an alternate method.

(I created a similar message yesterday but appear to have not actually submitted it, so pardon in advance if this shows up as a dupe.)

[HazelNuts39]

For whom it may interest - How AoA changes when encountering an upward gust:
25 fps gust (https://docs.google.com/leaf?id=0B0CqniOzW0rjZWVmNDBmMGQtZGJiZi00N2UwLWFjMzgtZGRhODE zZGI4Zjk5&hl=en_GB)
35 fps gust (https://docs.google.com/leaf?id=0B0CqniOzW0rjMWNiZTgwZDctNzU3ZC00YjEwLWFiZTktZTQ0Yjl hZTk1NWE1&hl=en_GB)

HN39

[Smilin_Ed]

Deploy the RAT (ram air turbine) emergency generator and use the RPM and generated power to compute air speed.

The rat will also accrete ice and given that it (probably) isn't heated will ice up pretty quickly.

As an old f@&t, I have to say that if you really get into icing and turbulence (which you should avoid anyway), the way to survive it is to keep the power at cruise settings and fly attitude. Ignore altitude fluctuations. Turn the autopilot OFF or you'll be fighting it constantly. You will move up and down with the air mass but as long as you are stabilized within the air mass, you will get through it.

[mm43]

HazelNuts39;

Very interesting.

Looking at the graphs in post #1467 (http://www.pprune.org/showthread.php?p=5746985#post5746646), I sense that the relationships between AoA, vertical gust velocity and "g" are fairly linear, and riding a 50fps gust is going to give an AoA of 5.6 degrees and 1.72g. Does using a fixed mixing zone figure, e.g. 300 feet, produce a higher "g"?

It follows that loss of an effective CL is a given.

mm43

[HazelNuts39]

Does using a fixed mixing zone figure, e.g. 300 feet, produce a higher "g"?
mm43;
thanks for your reply. The 35 fps gust with 300 ft mixing zone will result in a peak AoA of 5,0 degrees and 1,55 g. At higher AoA's the cL-alpha will become non-linear and "g" will be limited by cLmax (stall).

35 fps 300 ft (https://docs.google.com/leaf?id=0B0CqniOzW0rjZGUwMDczZjgtODM3Zi00NDc5LWE4YTgtNzQ5NzA 0MTJmMjdi&hl=en_GB)

regards,
HN39

[UNCTUOUS]

To assist an author looking at the entire vista of AF447 plausible scenarios, I've deconstructed the BBC transcript to as much as possible offer one alternative explanation.
.
The first file is the unexpurgated BBC transcript and the second is a commentary on certain aspects of that (with the line numbers in the 2nd file relating directly to the BBC transcript's line numbers).
.
RIGHT-CLICK save as ......
.
Please feel free to comment upon either/both (seeking validation/verification).
.
a. BBC Transcript
..................link one (http://tinyurl.com/2azrr5b)
.
b. Comments upon the BBC program's treatment of the AF447 mystery
..................link two (http://tinyurl.com/27ozhbl)
.
..................

[auv-ee]

From linked comments, regarding control of pitot heat:
This could be done via an altitude switch or via an outside air temperature (OAT) threshold. This recourse assumes that the OAT

If the underlying problem is that there can be both too little and too much pitot heat, then it seems that the logical approach is the direct one: to embed a thermistor in the pitot head and regulate the heat (for example, by duty cycle) to maintain a safe temperature at any speed/altitude. Someone likely knows a good temperature to use for the core of the probe that would keep the whole probe ice-free, possibly 40-60C?

[sensor_validation]

@UNCTUOUS

What is your mechanism for a pitot to slightly under-read?

If the ram-port blocked the the indicated flow will fall to zero if the drain open - guess you are looking for partial blockage of ram with drain open? If the drain also blocked the total pressure locked and indicated flow will vary with static pressure (known danger during take-off climb). I fear drain holes blocking at similar rate on more than one pitot could lead to small over-read before all 3 disagree, but as Takata has already pointed out still unlikely.

What are the real speed margins before or after a reduction in speed for turbulence entry?, and what is magnitude of drain hole blockage effect? If ice detected/suspected how much engine power will be used on wing anti-icing measures?

@auv-ee (http://www.pprune.org/members/327881-auv-ee)

Its going to be very difficult to maintain the temperature of pitot tube in 500 mph wind at much above the ambient air temperature - monitoring the power needed would turn it into a "hot-wire anemometer". If melting out ice the surface in contact with the ice will be at the freezing point of the water - a principle you could use to detect ice! You do need temperature control when on the ground to avoid turning the probes into soldering irons.

[jcjeant]

Hi,

UNCTUOUS
Thank you .. good job.

[GreatBear]

@UNCTUOUS

In your section 173: "An ACARS message from the airplane recorded the sudden onset of critical Mach and the autopilot disconnecting due to the high aerodynamic trim loads it was holding (and no longer could)."

There were no ACARS messages recording "the sudden onset of critical Mach." The AUTO FLT AP OFF message arrived at 02:10:10 quickly followed by AUTO FLT REAC W/S DET FAULT (unavailability of the reaction to wind shear detection function), then F/CTL ALTN LAW (PROT LOST) and the others.

Overspeed/underspeed/stall as part of the upset sequence has been discussed at length on this and the prior thread, and remain still in the realm of whatIfs. MachCrit is but one of the possibles. Need the black boxes to work out the sequence.

I'd be interested in your expert opinion and description of the politics that might be influencing the science of the "researches" so far. Who are the interested parties and national and international stakeholders; what are the lawers looking for (and why); what are the truths that would be favorable or unfavorable to these groups and why. Can the truth be bent in such investigations? How? That description would in many human ways define our times...

GB

[UNCTUOUS]

GreatBear asked:
I'd be interested in your expert opinion and description of the politics that might be influencing the science of the "researchs" so far. Who are the interested parties and national and international stakeholders; what are the lawyers looking for (and why); what are the truths that would be favorable or unfavorable to these groups and why. Can the truth be bent in such investigations? How? That description would in many human ways define our times...
The following linked input (for the same author) may answer that:
.................link (http://www.iasa-intl.com/folders/belfast/AF447/AFOct09response.htm)
GreatBear also said:
In your section 173: "An ACARS message from the airplane recorded the sudden onset of critical Mach and the autopilot disconnecting due to the high aerodynamic trim loads it was holding (and no longer could)."

There were no ACARS messages recording "the sudden onset of critical Mach." The AUTO FLT AP OFF message arrived at 02:10:10 quickly followed by AUTO FLT REAC W/S DET FAULT (unavailability of the reaction to wind shear detection function), then F/CTL ALTN LAW (PROT LOST) and the others.

Overspeed/underspeed/stall as part of the upset sequence has been discussed at length on this and the prior thread, and remain still in the realm of whatIfs. MachCrit is but one of the possibles. Need the black boxes to work out the sequence.
.
One of three likely events precipitated the upset:
a. BBC Scenario - Pilots neglected to add power (i.e. left throttles in CLB) after dial-selecting a slowdown to turbulence penetration speed and this led to an autopilot kick-out and stall/LoC following the airspeed indicators winding back to zero (the pure precipitation instant pitot freeze-over theory). Considered an unlikely confluence of events in comparison to (b. below) - a more insidious development during a relatively smooth cruise in the dense CirroStratus cloud to be found in the ITCZ areas (i.e. crew ennui/lethargy/surprise more likely to be a player than when alert and roughing it in the grip of a storm).
.
b. Favoured Scenario - Autothrust quietly adds power incrementally as supercooled ice crystals overcome the limited pitot-heating abilities and gradually accumulate as a granular filter inside each pitot (clogging drain and tube equally). Pilots fail to notice power adds or fuel flow increases as it's common to monitor the fuel management synoptic in long-haul (vice the engines page). In fact it's probably SOP to do so - as any engine fault will be separately annunciated, whereas fuel transfer discrepancies or leaks will only show up latterly). Aircraft hits Mach crit and mach tucks (autopilot disconnects and a/c pitches down violently).
.
c. Possible Scenario - As per b., however autopilot kicks out prior to Mach crit, due to one of:
(i) Holding too much pitch force due to THS being incorrectly trimmed by invalid airspeed data (...and a/c pitches them down into Mach Crit)
(ii) Airspeed splits becoming large enough to trigger a system-detected discrepancy..... and A/P kick-out occurs
.
In any of these three cases, particularly if the THS was in an out-of-trim state at A/P disconnect, the crew would be without airspeed info and therefore prone to hitting either an aerodynamic stall or Mach Crit. This would quickly lead to an "upset" as the Airbus Flight Control system protections in Normal or a degraded Law (ALT 1/2) would not be able to prevent an unusual attitude developing. Any misinterpretation of their predicament would put them in a world of greater hurt.
.
e.g. Max power and stick forward as a result of an assumed stall would embed them in Mach tuck. Rolling the wrong way in an attempted roll-out from an autorotative flick-roll would be an entry into an unrecoverable unusual attitude. Large bank angles always involve steep nose-drops - which lead to rapid acceleration of a heavy jet at height.
.
Finally, GreatBear said: "There were no ACARS messages recording "the sudden onset of critical Mach." Well think it through. Why would there be in any airspeed pitot compromised scenario? It's not a missing message, it's a disabled capability. That's one of the issues that I have with the cascade failures typical of (and endemic to) interdependent and integrated automation.
.

[BOAC]

Pilots neglected to add power (i.e. left throttles in CLB) after dial-selecting a slowdown to turbulence penetration speed - excuse a dumb q from a non-AB chap - isn't the A/T supposed to do that?

Unctious- I am now totally confused as to what you are presenting regarding BBC/ACARS. First you 'present' "An ACARS message from the airplane recorded the sudden onset of critical Mach" with no comment and then you tell GB "Well think it through. Why would there be in any airspeed pitot compromised scenario? It's not a missing message, it's a disabled capability."

[GreatBear]

Thanks, BOAC, my point exactly.

UNCTUOUS. I'm still having trouble picturing the auto throttle creep necessary to your "favoured" Mach tuck scenario when, by measuring ground speed until the upset (A/P disconnect, ten seconds after the last position report), the A/C seemed to be traveling at a constant cruise speed... see diagram (http://www.pprune.org/5715414-post1178.html). Perhaps creep towards the upper right of the coffin corner (+20kts? +40knts? +more? to a flick-roll) occurred in a very short timespan? Short enough not to influence the 0200 to 0210 distance traveled segment?

GB

[henra]

/Quote GreatBear

occurred in a very short timespan? Short enough not to influence the 0200 to 0210 distance traveled segment?


Hmm, without change in attitude this seems technically not feasible to me given the SEP of an A330 @210t at FL350.
That will take 'ages' to get it to Mcrit given a constant level attitude (>10min).
Had it left that level attitude before than something was pear shaped anyway.
Or they pushed the nose down due to a perceived risk of a stall.
Either way you see it a subtle Mcrit encounter without preceding event seems not very likely (at least to me).
However, an Mcrit encounter after an initial LoC seems absolutely possible.

[UNCTUOUS]

GreatBear Said: "UNCTUOUS. I'm still having trouble picturing the auto throttle creep necessary to your "favoured" Mach tuck scenario when, by measuring ground speed until the upset (A/P disconnect, ten seconds after the last position report), the A/C seemed to be traveling at a constant cruise speed... see diagram. Perhaps creep towards the upper right of the coffin corner (+20kts? +40knts? +more? to a flick-roll) occurred in a very short time-span? Short enough not to influence the 0200 to 0210 distance traveled segment?
BBC 178
MARTIN ALDER (A330 pilot). Our speed range is quite limited. Typically it could be ten knots either side of the cruise speed.

If, over a 6 minute period (say), the average of the undetected CAS speed increase was 5 knots, it would only make a half-mile extra distance gained along track. As the pitot became increasingly blocked, the rate of the displayed speed decrease trend (requiring auto-thrust increments to retain a system-stable displayed speed) would accelerate - so logically the last half of that 10+kt undetected speed-gain would occur over the last few minutes. i.e. not a uniform acceleration.

ACARS messages are queued for transmission and can be sent out of sequence. Positions relayed with messages are probably related to msg formatting times.... rather than Tx times. Pls correct me if I'm wrong there. However precision in the reported positions might be an unsupportable assumption anyway.

BOAC said: "Pilots neglected to add power (i.e. left throttles in CLB) after dial-selecting a slowdown to turbulence penetration speed"

BOAC's query: "excuse a dumb q from a non-AB chap - isn't the A/T supposed to do that?
The BBC assertion seems to be (sequentially) that:
a. a lower speed (turb penetration of M0.82) was dialled in due to radar-perceived down-track cell activity

b. at some time before they reached that speed, the "pure precipitation instant freeze-over" of some/all pitots occurred, causing the autopilot and autothrust disconnect.

c. in order to preclude a stall, the pilots would have then had to set 85% power and a 5 deg nose-up attitude (says Alder). Because of all the distracting alarms and reversion to ALT1, they possibly neglected to set the power, lost speed (unbeknownst to them) and stalled. i.e. they'd have been very acclimatized to autothrottles taking care of power to sustain selected speeds (another automation trap). A selection of max power at FL350 DURING a high AoA stall would stand a good chance of compressor stalling one engine (at least). That would introduce a severe asymmetric component and increase the chance of an autorotative "departure".
BBC208 - In 10 previous incidents of airspeed failure, the crews failed to increase thrust immediately.

TONY CABLE. In quite a number of them, it’s clear that the crews were very slow to get onto manual throttle operation.
BOAC said: Unctuous- I am now totally confused as to what you are presenting regarding BBC/ACARS. First you 'present' "An ACARS message from the airplane recorded the sudden onset of critical Mach" with no comment and then you tell GB "Well think it through. Why would there be in any airspeed pitot compromised scenario? It's not a missing message, it's a disabled capability."
Sorry, didn't mean to mince words/semantics, but I did say "recorded" rather than "reported" (in both the original and the response to the query above). I was trying to get across the timing of the triggering event (causing immediate autopilot and autothrust drop-outs), rather than infer that there was a specific Mach crit report.... which of course there couldn't have been - as (at that time) there was no airspeed data from which to derive it.
.
Ref henra's comment about the time taken to accelerate a 210tonne A330 to Mcrit, I've really no idea. The whole leg could've involved a quite slow acceleration (over 30 minutes say) or it may have been <10 mins. All such timing depends upon the rate of ice crystal accretion within the pitots, requiring autothrottle offset for a sustained display speed.
.

[bearfoil]

Fixation seems contagious. Dark, bumpy, somewhat complacent, most likely the Captain not flying, and a/p A/T quit, followed by a workload that doesn't stand a chance while surprised pilots try to get current with 'what is she doing now?'.

Then a slowly rotating a/c hits the sea vertically in "Line of Flight" (Which means what under the circumstances?). Trying to pin a time on the upset, I would suggest it happened quickly, followed by loss of power and hopes of regaining controlled flight.

Speed limit alert and Alternate Law controls. Maybe someone could advance a possibility given the cockpit environment (imagined). Throw in a powerful and unseen airmass with some very strange noises emanating from engines and airframe. With upset comes the need for immediate and precise controls on a good day, once established, how could recovery not be impossible.?

Stall Recovery is not taught here, it is deemed virtually impossible to happen. Yet the a/c can Stall. Therein lies the hubris and the politics for GreatBear. Colgan doesn't train Stall recovery either. At least not back in February, 09. For the record, a recovery was likely impossible with 447 in any case.

bear

Perhaps the defensiveness came from the original heated debates re: FBW.

[Hyperveloce]

it seems that the A/C could have exited its flight enveloppe underspeeding or overspeeding once the A/P & A/THR gone OFF. but I also feel that a large excursion in the high mach numbers (overspeed) take some time to become critical (see http://www.pprune.org/5102068-post4106.html for a basic/not validated attempt to get an idea), even descending at 1 or 2° with N1=95 or 100%. In past cases, 5 crews reacted to stall alarms by a nose down and a descent, -3500 ft max. but if there were increased turbulences close to the Cb cell and/or a turn to avoid a weather hazard, maybe the aerodynamic margins were further narrowed ? I thought that the overspeeding possibility was more probable / explainable given the known conditions/procedures/past cases, but if the plane is really south of LKP (so far from its route) close to the region where the pingers were detected by the French Navy & Thales, then the high altitude upset (in alt2, no alpha prot, no low speed stability) must have been more sudden/immediate than an overspeeding event ? (at 02:10 or early 02:11, not 02:12 or over). Then the other possibility, the low speed stall (BEA: low index vs the pich remaining locked)(possibly accompanied with a large roll excursion complicating the recovery) would appears more probable if the flight ended around 02:15Z in the pinger area ? in one past case of Pitot freezing the A/THR remained engaged and the N1 was varied between 48 and 100% (airchasing in turbulences ?). And as it was said, a low speed stall at high altitude can turn into an overspeed. Can a low speed stall due to a low N1 (50, 60%) locked occur rapidly from A/P A/THR OFF ? (say less than 20-30s)
Jeff

[ChristiaanJ]

Question from an ancient stupid here....

What's wrong with an "overspeed"?
Increased drag, increased buffet, possibly some decrease in controllabily. Oh, and in the books you're not supposed to go there.
But otherwise?

The DC-9 was deliberately flown to over Mach 1 during flight testing.
At least one 747 exceeded Mach 1, even if that was not deliberate, and returned to tell the tale.
The RAF VC-10s were over-powered, and some, towards the end of certain flights, were taken way beyond the formal Mcrit.... and they returned.
I'm sure there are others.

Now, I don't know zip about the A330. So maybe it DOES fall apart the moment you exceed Mcrit by two percentage points. I doubt it.

On the other hand, when an aircraft stalls, it's like any other aircraft.... it no longer flies.
And I mean when it "physically" stalls (not with various FBW protections having kicked in, and the aircraft is mushing down, but with still some kind of control) but with loss of airflow over the wings, and settled in a nice flat spin.

My uninformed conclusion is that they got in the "stall" corner of the coffin corner, not the Mcrit one.

Christian

[BOAC]

they got in the "stall" corner of the coffin corner, not the Mcrit one. - if you understood 'coffin corner'..........................................:ugh:

[CONF iture]

What's wrong with an "overspeed"?

I've no clue either but they build some protections for the 330 and sisters ... there must be a reason, a way to allow some structural weight saving maybe, or is it just for the fun to take control away from pilots ... :}

[ChristiaanJ]

I've no clue either but they build some protections for the 330 and sisters ... there must be a reason, a way to allow some structural weight saving maybe, or is it just for the fun to take control away from pilots ... :}CONF,
As I said, I'm an ancient...... Concorde.... remember?

We didn't call them "protections" at the time.
MAX CRUISE was simply an autopilot mode, that kept the aircraft within those three basic limitations: Mach 2.04, Tt 127° C, and IAS 530 kts.

Mostly there to make sure we could use the aircraft again next time.... or more seriously, to make sure it would would stay within the certification limits, to meet the certified supersonic cycles requirements.
And yes, we went up to Mach 2.23, and we did not use that aircraft (Delta Golf) again for commercial flight afterwards, even if it was thought about seriously at one time.

I've seen M 0.8 or suchlike mentioned for the A330. Was she certified to M 0.9 and beyond (as she should have been)? Or DID they "save some structural weight" somewhere?

CJ

[HarryMann]

What's wrong with an "overspeed"?

In smooth air when you know what's what and have been there before....

or when it's rough as hell and you don't really know what's what?

[CONF iture]

FCTM for reference :
HIGH SPEED PROTECTION

When flying beyond maximum design speeds VD/MD (which are greater that VMO/MMO), there is an increased potential for aircraft control difficulties and structural concerns, due to high air loads. Therefore, the margin between
VMO/MMO and VD/MD must be such that any possible overshoot of the normal
flight envelope should not cause any major difficulty.
High speed protection adds a positive nose-up G demand to a sidestick order, in order to protect the aircraft, in the event of a dive or vertical upset. As a result, this enables a reduction in the margin betwen VMO/MMO and VD/MD.

Therefore, in a dive situation:
. If there is no sidestick input on the sidestick, the aircraft will slightly overshoot VMO/MMO and fly back towards the envelope.
. If the sidestick is maintained full forward, the aircraft will significantly overshoot VMO/MMO without reaching VD/MD. At approximately VMO + 16 / MMO + 0.04, the pitch nose-down authority smoothly reduces to zero (which does not mean that the aircraft stabilizes at that speed).
MMO = M.86
MD obviously above M.90 ?

[OVERTALK]

My interpretation of the intended thrust of CONFiture's post on High-speed Protection follows.

As Normal Law would've been in play when (and if) the A330 hit Mcrit, for these protections to have been then overcome (and an upset occur), what particular anomaly could've been involved at the same point or as an immediate preliminary (i.e. to cause a transitioning to a degraded law - and kill the protections)?

It's becoming a bit "chicken and eggish".

but IMHO, it's looking more and more like it would've been the developing airspeed splits that started the downgrade in FC Laws and caused autopilot and autothrust to jump out. That would have instantly placed the pilot in the cross-hairs for an upset, for all the usual reasons:

a. surprise,

b. unfamiliarity,

c. loss of airspeed read-out,

d. engine parameter screen not being displayed,

e. a THS out-of-trim pitch-down into a high mach (possibly compounded by a misinterpretation of the situation as a stall - and max power and a lower nose attitude being selected),

f. or alternatively, mere distraction due to the aural and visual alarms allowing an unusual attitude to develop. Aircraft at height under manual control in ALT1 would be inherently unstable, particularly if manual thrust was changed significantly to affect the trim-state.

This scenario tends to accord more with what's known of the prior instances of pitot icing at high levels.

[Machinbird]

What's wrong with an "overspeed"? In an aircraft designed for subsonic flight, there is a lot of reason not to get too close to M 1.0. The primary reason is the center of pressure shift which occurs rather abruptly.
The aerodynamic center of the wing shifts from the quarter chord to the 50% chord (Actually the whole airframe generates lift based on the Angle of Attack of the individual components).
Since your lift is being generated further aft, the nose wants to tuck. The only way to get it back up will probably be THS trim since the elevator will be ineffective, but that has hazards all of its own, particularly when you decelerate below the transition point.
Then you might well break something when all that nose up trim takes hold.
If you haven't seen it before, take a look at the A380 flutter test video. YouTube - Airbus A380 Flutter Test (http://www.youtube.com/watch?v=ImSuZjvkATw)
In addition to Mach tuck and flutter when you exceed the demonstrated envelope, subsonic airliners buffet and occasionally lose bits off the aircraft.
It was impressive to see how much nose up stabilator (stabilator itself was nose down) was required to fly level in a supersonic F-4.

[CONF iture]

As Normal Law would've been in play when (and if) the A330 hit Mcrit, for these protections to have been then overcome (and an upset occur), what particular anomaly could've been involved at the same point or as an immediate preliminary (i.e. to cause a transitioning to a degraded law - and kill the protections)?
If all airspeed indicators under read at a similar level, the high speed protection won't trigger even if the real MMO is already passed. At this point the airplane is still in Normal Law as no malfunctions have been identified. The message for the Pitot tubes malfunction can appear only later on when finally the split between airspeeds reach the required threshold ... only then appear the ACARS messages as we know them ...

Very unlikely does not mean impossible ...

[jcjeant]

Hi,

Sorry for return again on the "tail problem" but I read something interesting there ... some comparison of crashs outcome about the tail ....

AF 447 : questions de dérives : Les dossiers noirs du transport aérien (http://henrimarnetcornus.20minutes-blogs.fr/archive/2010/06/13/af-447-questions-de-derives.html)

From up to bottom
Pic N°1 is AF447 tail (lost on sea "BEA" or in air ?????? )
Pic N°2 is raw drawing of attachement system (A330 and A300 same system of attachement)
Pic N°3 is tail at Tripoli crash on ground (stay attached)
Pic N°4 is tail Monterey crash A300 on ground (stay attached)
Pic N°5 is tail NY crash A300 (lost in flight)

[bearfoil]

jcjeant

Thank you. Food for thought. It comes to mind that the tail (complete) is built as a mating of cantilevered stabilizers and articulating control surfaces. When confronted with an impact into the ground, or water, it fails as a unit, due to overwhelming and reasonably conforming and directional stress. Failure of individual surfaces and panels suggests a mix of stressors, rather than one massive arrestment. It is intuitive. An impact with the ground or water would then have a tendency to remove much of the tail at once. This suggests to me (not conclusively, but certainly as a result of patent failures), that 447's V/S came off as a result of stress that was not sufficient to remove panels and surfaces that were not attendant to lateral failure, eg: HS or dorsal skin. I consider it odd that the VS was found alone, likewise the elevator. This isn't probitive, but it meets the test of possibilities. The elevator has its trailing edge fractured from the main panel which has removed from the THS, but the TE remains attached to the elevator. This just doesn't square with a single and overwhelming failure of all the parts. Likewise, the splinter at the TE of the elevator should have been explosively removed, and here's the thing: Separating from the THS infers a separate stress from that which (is proposed per BEA); the description of impact by BEA would have the reader think that one impact was suffered by an all intact tail, there would have been no time separation for a sequential, and partial failure of any part, it had to come off the tail as a unit, like the V/S Rudder.

Any failure which served to have distributed parts in the SEA, would have thus been caused by the airstream, and prior to impact.

bear

[HarryMann]

Any failure which served to have distributed parts in the SEA, would have thus been caused by the airstream, and prior to impact.

Could we have at least some guide to your qualifications to make that statement please?

[bearfoil]

Harry Mann

The statement stands; I am sure my qualifications would not satisfy you, and you are welcome to rebut or invite another to do so. If the mods allow it, I propose that you do as well, and consider the statement on its own "merits", subject of course to your critique.

[MCScott]

All,

I am not a pilot, nor an aerospace engineer per se. But I do have an MSME degree, have spent most of my life in computer programming, and have an elementary grasp of statistics and probability. I've also followed these AF447 threads with great interest, since the beginning a year ago. I have some comments regarding UNCTUOUS' very interesting theory, as expressed in comments to the BBC script.

- The BBC obviously did not do much research on previous incidents of IAS inconsistencies. As you said, most of these seem to have occurred in contexts that suggest ice crystals, rather than supercooled water, as the primary cause.

- I had understood the possibility, before, that engine thrust at AT disconnect might have been different than the pilots may have intuitively expected, due to intervention by the flight management system in response to turbulence settings or other phenomena. I had not known, though, that selection of the "fuel monitoring" screen would further obscure the true current engine thrust settings.

- Without doing any in-depth analysis, your theory of relatively gradual degradation in speed readings leading to mach-effect overspeed phenomena, while plausible, does not seem very likely. The pitot tube is a very simple analog device, whose basic design predates the dawn of aviation. It operates primarily on pressure difference, rather than flow, per se - very little air actually flows through the tube (some air does exit through drain holes, etc, but that is by design a small amount, or the tube won't serve its intended purpose). This in turn means that the tube will need to be almost fully blocked before significant pressure and airspeed indication loss is observed. And that, in turn, means that airspeed indication loss due to icing will very, very likely be 1). rapid, 2). unstable, and 3). inconsistent between redundant tubes. This is consistent with the summaries of known IAS anomalies previous to AF447. While I have no knowledge of the airspeed validation algorithms in the Airbus flight management systems, it seems likely that they would be programmed to reject airspeed data inconsistent with the physical capabilities of the aircraft and known limits of windspeed variation, which would further limit the kind of airspeed variation which could lead to your scenario. It is certainly possible that high-altitude upset could have occurred due to overspeed because of pilot input in a confusing environment with no accurate feedback, but I don't see that overspeed due to AT correction is especially likely.

- The issue of training for high-altitude upset (stall, mach-tuck, etc) is interesting. The apparent inability of most commercial simulators to simulate stall in combinations of pitch and roll is something I'd not understood. Beyond that, there is the fact that humans are not machines, and will react differently when primed to expect surprises than when they are lulled into complacence by thousands of hours of uneventful automated flight at cruise altitude. The point made by the military pilot - that military craft are almost always manually flown, and thus the pilot is always in that "zone of awareness", is significant. And then there's the question: with all of the air miles flown today, and the fragmentation of air traveler miles into more and more flights on smaller and smaller planes, can we possibly expect all of the burgeoning ranks of pilots to have the degree of manual flight skill needed to recover from the hypothetical AF447 situations?

- It is easy to identify accidents related to failures of automated flight systems, or the misuse thereof. It is impossible to track accidents avoided by such systems. The overall statistics, which seem to show fewer and fewer accidents per air mile traveled, suggest that if automation is either a net safety benefit, or it is being overwhelmed by other safety improvements. I have no data to say one way or another.

[CONF iture]

What about this one ?

http://i65.servimg.com/u/f65/11/75/17/84/nz_00110.gif (http://www.servimg.com/image_preview.php?i=59&u=11751784)

Amazing, it didn't really happen in the middle of the Atlantic, but that's the only photo we have seen so far ... Some know how to control the information.

[Machinbird]

What about this one ?Yes, but we know it flew into the water nose down at fair speed.
I think what we are seeing is that the Airbus VS structure is fairly robust and will survive a fair beating relatively intact. The attach lugs tell the story of how they came off the rest of the airframe.

[HazelNuts39]

(DingDong) Ladies and gentlemen, your captain speaking:
We have just arrived at our cruise altitude of 35,000 feet, popularly known as "the coffin corner" (https://docs.google.com/leaf?id=0B0CqniOzW0rjMjM1NGE5ZWYtMmM4OS00NDYyLThjNjYtZGFmMGY xYTNjYjEz&hl=en_GB)'. Enjoy your flight with XYZ Airlines ...

EDIT:: Just to put Martin Alder's remark in the BBC documentary into perspective: in this case as shown in the graphic, the 'coffin corner' is actually 102 kt wide: from M=0,58/192 ktCAS to M=0,86/294 ktCAS.

HN39