AF 447 Thread No. 9

[Linktrained]

If one of the pilots had noticed the hands of "" ... My old Sensitive Altimeter ..." spinning round ( say.. by FL33.0 ?), one of them might have noticed that the THS had reached an unusual reading of fully NU.

I am lead to believe that the THS FOLLOWS commands, from A/P or S/S.
( I had mistakenly believed that it might have been otherwise, until I was corrected by Tanaka.)

The A/P was off. The THS must have moved in response to a S/S.

Some airlines seemed to train that " the THS is something WE do not touch"
I do not know whether this was so in AF.

Never having operated under the PF/PNF system, I would like to be told the etiquette then used when pressing the " I have control button" when one is reluctant to yield to the other.

[Lyman]

@airtren A corollary to the problem of redundancy showed up in BA038. At some stage, and not just in ETOPS, commonality rears its insistent head: eg turbofans burn fuel to produce energy. So then do pitot heads sense air pressure to indicate an absolute value. after 447, it was considered sufficient resolution of the Thales problem to allow one problematic probe to remain installed.

As in 038, the problem was identified in the penultimate position, an oil cooler in the engines. It was not considered ok to change out one TRENT for a GE. It is identical in presentation, a weak link is not allowed to remain in reduindancy, indeed, redundancy is the problem when common fault is the issue. Can we extrapolate? Two pilots are required as crew, and it is impossible to supply identical pilot one for one. In handover, the new pilot is a different solution, by definition, so redundancy in the case of pilots is not an issue, in fact, the "back up" is a fresh resource with different solution making potentials by definition.

The Thales had a specific problem due corrosion at the drain, was this the cause of the icing? from an "anomalous design solution" perspective, the problem becomes the solution, the difference in corrosion support probe to probe makes the Thales probe anomalous, which is the goal in fault prevention in similar systems. Facetiously, but truly, what makes similar devices superior in multiple install is their separate engineering approaches. See 'pilots' above.....

@Linktrained per the report, the AP was ON (selected ON). No?

[Sriajuda]

The "redudancy" assumed by this design of speed sensing - which at this point is not different than other manufacturers - seems to target intrinsic/internal sensor failures and less a failure caused by external events, such as weather.

Indeed - and it even only partly achieves redundancy for intrinsic failures, since design/manufacture faults are likely to be present in all sensors if they are from the same manufacturer & type and maybe even from the same production batch.

Since airspeed information is probably THE most important data in an AC (pilots, please correct me), this neglience to provide both true sensor redundance and obviously not implementing secondary, heuristic means to verify and/or determine air speed is incomprehensible to me.

[Sriajuda]

If one of the pilots had noticed the hands of "" ... My old Sensitive Altimeter ..." spinning round ( say.. by FL33.0 ?), one of them might have noticed that the THS had reached an unusual reading of fully NU.

If I remember correctly, in the Airbus the trim wheel does not make the 'clack-clack-clack' sound that other aircraft do. Another example of technology that seems to be designed to withhold information from the pilots? As in the sidestick configuration?

[Lyman]

The design of the airbus philosophy is fraught with examples of "inscrutabilities"

IMHO

[jcjeant]

Airbus met en avant des erreurs de pilotage sur le Rio-Paris - Libération (http://www.liberation.fr/societe/2012/07/11/airbus-met-en-avant-des-erreurs-de-pilotage-sur-le-rio-paris_832659)

Google*Traduction (http://translate.google.be/translate?sl=fr&tl=en&js=n&prev=_t&hl=fr&ie=UTF-8&layout=2&eotf=1&u=http%3A%2F%2Fwww.liberation.fr%2Fsociete%2F2012%2F07%2F11% 2Fairbus-met-en-avant-des-erreurs-de-pilotage-sur-le-rio-paris_832659&act=url)
The survey showed that other aircraft flying in the area shortly before the accident had opted for a radical change of course when the drivers of the Rio-Paris had slightly altered their course. The manufacturer also points out that "the loss rates should have led the pilot to apply the procedure on questionable speeds, which results not including the disconnection of the flight director."
This instrument, which ensures the trajectory of the plane, could mislead pilots, concluded last week the Bureau of Investigation and Analysis (BEA), in its final report. "As indicated by the BEA, we will never know if the pilots flew the flight directors in the absence of camera in the cockpit, but if they did, the phase of destabilization of the trajectory (which following the disconnection of the autopilot) in no case have been influenced by the flight director, "said the spokesman told AFP, referring to data stored in the report.

[RetiredF4]

Linktrained
The A/P was off. The THS must have moved in response to a S/S.

In this case it moved due to SS input.

To be correct though, THS moves also without SS input to hold the desired g, which would be 1 g without SS input. It has nothing to do with the autopilot on or off.

If PF would have only released the SS on his way up to the apogee (with decreasing speed) the FCS in ALT2B without protections would have deflected the elevators and in the following the THS Trim to full nose up to maintain the 1g (which is the demand with SS neutral) until the same result would have taken place, maybe within a somewhat prolonged timeframe.

Only positive SS ND input would have prevented that.

[Sriajuda]

Two pilots are required as crew, and it is impossible to supply identical pilot one for one. In handover, the new pilot is a different solution, by definition, so redundancy in the case of pilots is not an issue, in fact, the "back up" is a fresh resource with different solution making potentials by definition.

Hm, I think that is only partially true. Rigid procedures & training aim to make pilot behaviour both predictable and, consequently, identical.

In the case of AF447, we seem to see just that - but in a failure mode. Three pilots did not understand what was happening, and failed to fly the plane.

That leads me to another thing in the report that sends shivers down my spine: The stall warning was sounded more than 70 times during those fatal minutes, and there was no acknowledgement by any pilot of that, neither through action, nor through speech. It has been speculated that the pilots did not perceive the stall warning, maybe due to sensory overload. To me, it seems much more likely that they did not believe the stall warning. And if that is the case, simultaneously with three pilots, it tells a chilling story of the trust these professionals had in their technology, their aircraft, their instruments. Apparently zero. Wonder why??

[roulishollandais]

"As indicated by the BEA, we will never know if the pilots flew the flight directors in the absence of camera in the cockpit, but if they did, the phase of destabilization of the trajectory (which following the disconnection of the autopilot) in no case have been influenced by the flight director, "said the spokesman told AFP, referring to data stored in the report

I wonder that FD problem has been emphasized in the final report, but why not : It is easy and mandatory to replicate the flight in simulator to confirm or leave that theory. Scientific method needs ! :=

How could the BEA leave that theory without verifying it ? :E

Reading once more, and also a little more, in the final report, about the architecture of the flying software and automation, I see many problems with observability and controllability in the men-machine interface :\, and specialy with that FD who tells the AP , but doing something different : on is disconnected, the other not .... It seems all the possible cases have not been verified. I never worked sofware with such irresponsibility for human lifes.

The connection between air data and inertial reference is also unclear, and the BEA was not very curious ! The voting system between ADR and IR is not enough analysed for example.:eek:

[DozyWannabe]

With the current design, the 3 pitot tubes are not only of the same type and same manufacturer, but they are also located pretty much in the same place - under the nose...

Not quite true. Since the problems, it seems airlines have either switched to a combination of Thales AB and Goodrich, or all-Goodrich (which are deemed more reliable). The tubes themselves are located on opposite sides of the airframe (with the standby just forward and below the Captain's primary pitot tube).

Since airspeed information is probably THE most important data in an AC (pilots, please correct me), this neglience to provide both true sensor redundance and obviously not implementing secondary, heuristic means to verify and/or determine air speed is incomprehensible to me.

Welcome to the board!

Right - to answer some of your queries, the issue is one of complexity. The BUSS (Backup Speed Scale) device now offered as an option by Airbus works along the principles you describe - but the fact is that pitot tubes remain the most reliable, accurate and elegant engineering solution to the problem of airspeed determination.

Previous accidents attributed to loss of airspeed information involved either a lack of simplistic redundancy of the kind provided by the Airbus design, or (as in the case of Birgenair) failure to diagnose a fault within a single pitot tube and correctly use the redundancy available. The point behind the "quorum" design that existed prior to AF447 was that the systems themselves would be able to diagnose the problem and switch to the working sensors automatically - cases where all sensors failed within a tight timeframe were practically unheard of up until that point and as such, a triple failure was considered out-of-scope. As is so often the case, reality can intrude and make fools of us engineers in unexpected ways (in this case switching to the Thales AA pitot tube model without exhaustive testing to check whether the replacement was like-for-like in all conditions).

This "failure of imagination" has affected every complex engineering endeavour human beings have embarked upon, from bridge-building through seafaring and aviation right up to spaceflight. The only way to avoid that risk completely is to never embark on such endeavours in the first place.

If I remember correctly, in the Airbus the trim wheel does not make the 'clack-clack-clack' sound that other aircraft do. Another example of technology that seems to be designed to withhold information from the pilots? As in the sidestick configuration?

You could look at it that way, but (IMO) only if you've come at it from a pre-determined conclusion that the Airbus FBW design was intended to withhold information from pilots (which, while a stubborn notion to disprove, is in fact not borne out by the evidence). The sidesticks are not interconnected and do not provide force-feedback because of the additional engineering complexity required to do so, and in jet airliners from the late '40s onwards, any feedback through the control column is in fact artificial and as such can be prone to failure.

The trim wheels are quieter on the FBW Airbus because unlike other airliners of the vintage, trim is an automatic function in every law except Direct and MAN PITCH TRIM ONLY. Even in aircraft of a similar vintage (e.g. 757, 767), pilots will be trimming manually whenever autoflight is disengaged, and the trim wheels are an integral part of manual flight. Because this is not the case on the FBW Airbus in over 99% of cases, the trim wheels are not as intrusive.

Now - obviously in this case, having the trim wheels announce movement more forcefully might have drawn attention to the way the aircraft was being mishandled - but given the fact that neither of the two F/Os had high-altitude manual flight training on type this can't be taken as read.

It may interest you to know that when we ran the scenario in an A320 sim, it turns out that in Alternate [no speed stability] (the A320 equivalent of Alternate 2), autotrim had a hard limit of approximately 5 degrees nose-up, even when holding the sidestick against the back stop. As a result of this we managed to recover with stick full forward after losing barely 8,000ft. In order to test the exact circumstances, our TRE had to manually wind the trim up full once the limit had been reached on the following experiment - this time we lost closer to 18,000ft before recovering, but importantly we found that recovery was theoretically possible using sidestick alone - i.e. without having to manually adjust trim, *provided* that the problem was diagnosed relatively quickly.

Why there's a difference in autotrim behaviour between the A320 and her larger sisters I don't know, but it's definitely an interesting fact to take into account.

[bratschewurst]

but we don't really know if the airplane was unable to recover from a stall.Nor do we know that it could have been recovered from the stall induced by the PF. What we do know is that there was no procedure (certainly no tested procedure) known to the pilots for safely recovering from a fully developed stall. Obviously getting the nose down and unloading the wing - but for how long? And, if there had been a procedure, wouldn't it have used airspeed as a guide to when to start pulling up? I am skeptical that even a pilot more experienced in hand-flying large transport aircraft than were the PF and PNF (the captain of AF 447, for example) would have been able to fly AF 447 out the stall induced by the PF without breaking something, especially in the absence of reliable and trusted airspeed information.

[jcjeant]

would have been able to fly AF 447 out the stall induced by the PF without breaking something, especially in the absence of reliable and trusted airspeed information.
The BEA estimate reliable speed after 29 seconds
Page 24 Final report
At about 2 h 10 min 36, the speed displayed on the left side became valid again and
was then 223 kt; the ISIS speed was still erroneous. The aeroplane had lost about
50 kt since the autopilot disconnection and the beginning of the climb. The speed
displayed on the left side was incorrect for 29 seconds.Page 25
remained in the latter position until the end of the flight. Around fifteen seconds
later, the ADR3 being selected on the right side PFD, the speed on the PF side became
valid again at the same time as that displayed on the ISIS. It was then at 185kt and the
three displayed airspeeds were consistent. The PF continued to make nose-up inputs.
The aeroplane’s altitude reached its maximum of about 38,000 ft; its pitch attitude
and angle of attack were 16 degrees.

So if it was to be stall recovery .. they had good speed indications ..

[hetfield]

BTW

it's BRATWURST

not

Bratschewurst
:)

[paull]

The BEA estimate reliable speed after 29 seconds
Page 24 Final report

Which is all very fine, but you know that now, they did not know what was good.

I'm not a pilot but I find it very interesting how many pilots called these guys idiots. For me, they were qualified, they were trained, it was certified, it happened. It could happen again, WE SHOULD BE WORRIED.

I would really like to see a survey of current pilots of similar equipment as to whether they think these guys were idiots. Give me a list of those who say yes and I will pull the emergency exit door if I hear them on the PA prior to take-off. (Just joking, probably get arrested for this if it were a tweat etc,...)

[henra]

If PF would have only released the SS on his way up to the apogee (with decreasing speed) the FCS in ALT2B without protections would have deflected the elevators and in the following the THS Trim to full nose up to maintain the 1g (which is the demand with SS neutral) until the same result would have taken place,


Sorry for the nitpicking that will follow:
In a C* FCS law the g load command will progessively blend over to a pitch rate demand below a certain speed threshold.
But the result would be as you described (A pure g load law would even try to increase pitch in order to maintain g when aaproaching the stall).
The C* law would (try to) hold attitude (read pitch) constant at the value initially commanded by the PF.

[henra]

The voting system between ADR and IR is not enough analysed for example.:eek:

Is there a voting system between ADR and IR ?

I understood there is a voting system between the ADR's and a voting system between the IR's. And that logic was described.
But between the two? How would you vote between Air Data and Inertial Data? Normally they are complementary (not competing) data.

Could you reference to a document or a link where this is described?

[mm43]

Originally posted by henra ...
The C* law would (try to) hold attitude (read pitch) constant at the value initially commanded by the PF.Which is the reason the THS started to move NU on the final climb into the stall, even though the elevator was around 7° NU.:ok:

[Lyman]

Would the THS have stopped had a shaker/pusher been installed? What manner of seductive force was applied to the regulator such that a shaker/pusher was not required on this aircraft? Would it have mooted all discussion by virtue of preventing the pilots from maintaining the STALL?

[john_tullamarine]

I'm not a pilot but I find it very interesting how many pilots called these guys idiots

I suggest that comment is quite unreasonable.

The problem of concern (relating to the chaps in the front at the time) involves consideration of their training (which then involves consideration of their employer's training programs and philosophies) and subsequent piloting skill set, as well as experience overall.

It is reasonable to presume that they were typical fellows with typical mental capabilities and survival instincts .. but certainly not idiots.

We are all at potential risk of failing if the conditions are too far out of our personal comfort zones .. indeed, as is observed periodically, the simulator can be used as an instrument of torture to overload any pilot to the point where he/she cannot cope and, hence, fails. Pointless exercise but it happens.

[DozyWannabe]

Which is the reason the THS started to move NU on the final climb into the stall, even though the elevator was around 7° NU.:ok:

The concurrent action of the PF slamming the sidestick against the back stop and holding it there probably contributed to the extreme THS angle.

Would the THS have stopped had a shaker/pusher been installed? What manner of seductive force was applied to the regulator such that a shaker/pusher was not required on this aircraft? Would it have mooted all discussion by virtue of preventing the pilots from maintaining the STALL?

Because stall prevention works differently in a FBW airliner. Stick "pushers" were a relatively crude safety device that grew out of '50s technology, and the proliferation of T-tail designs from the late '50s to mid '60s. The only regulator that required them (regardless of empennage configuration) was the UK's CAA.

To my mind the only line accident where the stick pusher was a factor was the BEA548 Trident crash in Staines, and in that case the crew disabled the stick pusher in the middle of a stall, sealing the fate of the aircraft.

There are numerous cases of accidents where a stick shaker was ignored or dismissed as erroneous by the crew - including Birgenair.

One of the BEA's recommendations is for Airbus to bolster the auditory stall warning with extra visual clues.

However, based on prior experience it seems that if a stall warning or automatic recovery does not fit the crew's mental model, then even if you wire the stall warning to a cattle prod there's a chance that it will not be heeded.

[Lyman]

sriajuda @ 16:54

I think the goal is definitely not to produce identical pilots, but to train all pilots to minimum standards. The standard is set, though arbitrarily, by other than the crew, and experience and skill are varied, it is human nature.

For example, if there were two identical PF's and one had acquiesced to the other, the result on 447 would have been the same? No, because the position is different, the perspective is different, etc. No matter, it is clear that at least at the start, PNF had the picture correct....

How many have said the PF should have handed over to PNF? Merely looking at route experience, that would be logical.

My point above is meant to demonstrate the benefits of incorporating separate designs into two devices that accomplish the same task on an airliner. What defeated the Thales (microgranular water ICE), historically had less effect on Goodrich, type for type. So in grading the two, Thales is found wanting in ICE resistance; perhaps Goodrich has a different weak spot. Redundancy in the face of common fault is worse than no redundancy at all. Back up with a separate design approach is far better.

[mm43]

Originally posted by DozyWannabe ...
The concurrent action of the PF slamming the sidestick against the back stop and holding it there probably contributed to the extreme THS angle.I can accept that, but my comment was in relation to when the THS started moving in an attempt to hold pitch attitude constant at the value initially commanded by the PF, as airspeed went south.

[DozyWannabe]

Absolutely - but THS behaviour is entirely predicated on command trend over time. If the sidestick command was an initial nose-up followed by neutral then the THS woudn't have moved. What caused the movement was the best part of a minute where the sidestick commands were half nose-up for extended periods of time.

[Linktrained]

Thank you for the various contributions to " Sensitive Altimeter" suggestion. It would only have been of benefit as a possible attention getter once stalled.

As an ignorant newbie I sat myself in PF's seat on 5th. Aug. last year Thread 5. #1577 to see how I would feel in his circumstances. ( I have learned a lot since, thanks to the very wide ranges covered by contributors to PPRUNE.)

For Lyman and others I used "...A/P Off.." as a shorthand for " not functioning at the moment whatever the position of a switch" !

[DozyWannabe]

@Linktrained

A decade or two ago, there was a lot of debate around digital altimetry display versus the old "steam gauge" design - predicated on the idea that the old analogue design could be "read" at a glance whereas the digital display had to be read completely. Of course, with the "tape" display behind the precise altitude, this difference is mitigated. In the sim I could certainly read the descending trend at a glance once the stall was established!

I think most of us understood what you meant by "AP OFF". For everyone's future reference the AP was not only "OFF", but latched off (i.e. impossible to re-engage) as soon as the law changed to Alt 2.

[ I suspect Lyman's fishing for "AP was mysteriously re-engaged"... :ugh: ]

[mm43]

DozyWannabe;

I think we have had this THS discussion previously (http://www.pprune.org/tech-log/468394-af-447-thread-no-7-a-21.html#post6816266).

As BOAC would say, "that Oozlum bird is circling again!!":hmm:

[Lyman]

Dozy regarding my fishing.... It is Airbus who warns not to reselect Autopilot: "The autopilot may command undesirable Pitch attitudes, resulting in damage to the aircraft" (or something like that.) It is not I who first asked re: the autopilot in AL. If as you say reselect is impossible, why do Airbus warn pilots not to "reselect"? For that matter, why do they direct the pilot to turn off a/p as part of the drill? Isn't it already off, and "latched out"? Hmmm?

I assume an apology is out of the question.

Re: BEA salaries and the Law. My statement addresses the "Appearance of impropriety". The appearance is there, not my opinion, it is there. I cannot prove skulduggery, nor can you prove its lack... I can prove that Airbus profits go into the Government fund that pays the salaries and benefits of all its agencies. To that extent, you are barking up a tree.

The agency that regulates our banks in this country, (and the ones in France) also derives its budget from the regulated, through fees and charges. Do you claim that the Banks are treated with objectivity equal to a harsh analysis thereof?

[airtren]

Originally Posted by airtren http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/buttons/viewpost.gif (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-post7290293.html#post7290293)
With the current design, the 3 pitot tubes are not only of the same type and same manufacturer, but they are also located pretty much in the same place - under the nose...Not quite true.... The tubes themselves are located on opposite sides of the airframe (with the standby just forward and below the Captain's primary pitot tube).

If you think that the placement on "opposite sides" under the nose, protects the pitot tubes from sharing the same fate facing the weather, you need a reminder that at a body width of 5.64 meter, the maximum cross-span of the A330 could be just that.

As the location of the pitots is not diameter opposite, the cross span is less than the diameter. Based on memorized photos, I would say it's rather 3 meters between opposites, and abouot 1-2 meters between neighbor tubes. But even if it were 5.64meters, that is nothing when compared to the considerable larger width of weather fronts that the A/C is usually crossing. That qualifies for a "pretty much the same place - under the nose".....

[Machinbird]

In the sim I could certainly read the descending trend at a glance once the stall was established!
The trend, yes. But.....

Were you aware of the actual altitude? Would you be able to read the actual altitude with a heavy buffet?

[airtren]

Nor do we know that it could have been recovered from the stall induced by the PF. What we do know is that there was no procedure (certainly no tested procedure) known to the pilots for safely recovering from a fully developed stall. Obviously getting the nose down and unloading the wing - but for how long? And, if there had been a procedure, wouldn't it have used airspeed as a guide to when to start pulling up? I am skeptical that even a pilot more experienced in hand-flying large transport aircraft than were the PF and PNF (the captain of AF 447, for example) would have been able to fly AF 447 out the stall induced by the PF without breaking something, especially in the absence of reliable and trusted airspeed information.
This reminds me of the case of the September 1994 Tarom A310 event at approaching Orly/France , which is an example of pilots knowing what needs be done, at a stall - from manual flying training - and who in fractions of seconds, recovered from the stall - A/C almost vertical nose up - at a much lower altitude, and avoided any material or physical damage to the A/C or to the passengers - no-one was injured.

See: http://www.youtube.com/watch?v=VqmrRFeYzBI

[hetfield]

One reason the A310 finally made it was banking to the left at top of climb.

Is roll command on A330 in ALTN2 the same as in NORMAL law (roll rate command)?

Thx

[mm43]

If you haven't already done so, take a look at this post by sadpole (http://www.pprune.org/rumours-news/489790-af-447-report-out-17.html#post7291480) in the other thread. Some insight into what the Human Factors Group probably missed.

[infrequentflyer789]

Dozy regarding my fishing.... It is Airbus who warns not to reselect Autopilot: "The autopilot may command undesirable Pitch attitudes, resulting in damage to the aircraft" (or something like that.) It is not I who first asked re: the autopilot in AL. If as you say reselect is impossible, why do Airbus warn pilots not to "reselect"? For that matter, why do they direct the pilot to turn off a/p as part of the drill? Isn't it already off, and "latched out"? Hmmm?


Sometimes those in conflict are both right...

I think / recall that the a/p-off latch depends on precisely which law the a/c gets into. That depends on how many ADRs fail and for how long and maybe in which order. That in turn depends on which pitots ice up, how badly, and maybe in which order - which will vary.

I recall that there has been at least one case where a/p was re-engaged soon after UAS and did the wrong thing due to speeds being in agreement but still erroneous.

The line in the procedure looks like it is to ensure that ap/fd are off (they might have dropped out but maybe not). I think there has been additional guidance (that's come up on these threads) about not re-engaging them too quickly (ensure speed info is back to normal first).

[jcjeant]

Hi,

Interesting EASA publication:
http://ad.easa.europa.eu/blob/easa_ad_2010_0271.pdf/AD_2010-0271_1
So .. in 2010 .. they put emphasis on the FD ... (after the AF447 case)

[syseng68k]

henra, #259


Is there a voting system between ADR and IR ?

I understood there is a voting system between the
ADR's and a voting system between the IR's. And that
logic was described.

But between the two? How would you vote between Air
Data and Inertial Data? Normally they are complementary
(not competing) data.

The idea of combining > 1 independent, limited reliability
sources to improve overall performance is not new. For example,
GPS / inertial mixing has been in use for some time. A brief
description may help to illustrate why this is a good idea,
with of course apologies for those who know all this already.

An ins system (IRU in airbus speak) works by dead reckoning
and is subject to drift over time. By dead reckoning, I mean
calculated from the point of origin, or start position. The
accumulated position error could be as much as several
nautical miles per hour, though current state of the art may
be much better than this. GPS doesn't work by dead reckoning,
but by direct measurement of absolute position and has far
greater accuracy, to within a few feet over much of the earths
surface. However gps can suffer from signal dropout and loss of
accuracy in some regions and is susceptable to jamming.

With the gps / inertial mixing scheme, some very smart software
augments the ins data with that of the gps to provide better
long term accuracy, redundancy and improved error detection.
For example, if the margin between the ins and gps data exceeds
a given threshold for a number of samples, one or other can be
tagged as a degraded source, while still providing good data
over the short term. That is, we now have a holdover capability
in the event of a temporary fault from either source.

By now, you can probably see where i'm taking this in terms of
a baro / inertial mixing scheme. Ins data could be used to
augment and cross check air data information. From what i've read,
the current systems are independent and any results of cross checking
between the ins and air data speeds (baro) are not presented to the
flight deck. The problem of using ins data to correlate air speed
is that the ins measures ground speed. However, at any given point
in time, there is a historical timeline and ongoing relationship
between the two. This could be used in the short term to provide
an indication of air speed in the event of a temporary pitot tube
failure. If one assumes that the wind speed remains fairly constant
short term, such a baro inertial mixing scheme could be a valid
solution to the loss of air speed data, upon which so many other
subsystems depend.

There other ways to measure air speed, such as the airbus developed
laser measuring system and which is, iirc, available as an option
on the A380. Hopefully, it will become mandatory at some stage.

Feel free to hack at all this if you like :-)...

[BOAC]

Interesting EASA publication:
http://ad.easa.europa.eu/blob/easa_a...AD_2010-0271_1 (http://ad.easa.europa.eu/blob/easa_ad_2010_0271.pdf/AD_2010-0271_1)
So .. in 2010 .. they put emphasis on the FD ... (after the AF447 case) - I see repeated reference all over PPrune to this being the 'correct action'. Was this in fact so, i.e.a QRH item before 447?

[jcjeant]

I see repeated reference all over PPRuNe to this being the 'correct action'. Was this in fact so, i.e.a QRH item before 447? Some clues page 98 periodic training check (unfortunately in french) in report N°2
http://www.bea.aero/docspa/2009/f-cp090601e2.en/pdf/f-cp090601e2.en.pdf

[DozyWannabe]

I recall that there has been at least one case where a/p was re-engaged soon after UAS and did the wrong thing due to speeds being in agreement but still erroneous.

The UAS duration was not sufficient to latch Alternate 2 in that case. While it's true that it was possible to re-engage AP in that scenario, the re-engagement had to be manual. The AP will not re-engage itself automatically in any scenario, and because Alt2 was triggered and latched in the case of AF447 even a manual attempt to re-engage AP would have been denied.

Because of the digital nature of the equipment, the AP switch is not a type where AP status can be determined by switch position - AP status is determined by the presence of the Autopilot button light on the FCU and the PFD status instead.

- I see repeated reference all over PPrune to this being the 'correct action'. Was this in fact so, i.e.a QRH item before 447?

Would need confirmation on the QRH, but "Flight Director : OFF" was definitely a step in the UAS procedure published by Airbus and disseminated to the airlines prior to AF447.

[Machinbird]

If you haven't already done so, take a look at this post by sadpole (http://www.pprune.org/rumours-news/489790-af-447-report-out-17.html#post7291480) in the other thread. Some insight into what the Human Factors Group probably missed. Good spot MM-43. I particularly liked his third point. What self-respecting pilot thinks autopilot time should be counted the same as actual handling time? You do learn Navigate and Communicate stuff and you do manage the systems, but are you really keeping the Aviate stuff up to speed?

Probably won't happen unless the regulators wake up. Too many sacred cows.:}

[Turbine D]

BOAC, jcjeant, Dozy & Infrequentflyer789,

I am thinking that perhaps (maybe) the AD 2010-2071 resulted from the TAM incident (perhaps others?). In the TAM incident the NTSB investigated and noted:
On May 21, 2009, at 2147 eastern daylight time (EDT), an Airbus A330-233, Brazilian registration PT-MVB, manufacturer serial number 238, operated by TAM Airlines as flight 8091 from Miami International Airport, Florida, to Sao Paulo Guarulhos International Airport, Sao Paulo, Brazil, experienced a loss of primary speed and altitude information while in cruise flight at FL370 over international waters, south of Haiti.
About 6 seconds after the autopilot disengaged, recorded data indicated two brief re-engagements of the autopilot. Concurrent with the re-engagement, a pitch up to about 7 degrees nose up and slight climb was recorded, and the pilot reported a stall warning. Left side stick pitch inputs were recorded about one second after the autopilot disengaged from the second brief engagement, as the airplane climbed to about 38,000 feet. The autopilot remained disengaged during the remainder of the event, and the crew turned about 60 degrees to the left to diverge from the weather area, and the altitude decreased to about 36,500 feet, before reversing and increasing again. About 3 minutes and 30 seconds after the initial airspeed drop, the No.1 ADR returned to 260 knots, and the 300 foot altitude discontinuity ceased, indicating an altitude of about 37,400 feet. Left nose down stick inputs and a decrease in pitch were concurrent with the altitude returning to 37,000 (FL370). Then autopilot and autothrust were then re-engaged and the flight continued to Sao Paulo in alternate law with no further incident, no injuries, and no damage. Post flight maintenance checks on the airspeed system revealed no discrepancies.

In this instance TAM never got to the Alternate 2 state where the AP couldn't be re-engaged (latched) as Dozy pointed out, but nevertheless, felt emphasis was required on not re-engaging the AP so quickly.
Just a thought....

[DozyWannabe]

@TD - Good catch. I think it was recognised as a general industry-wide issue before then though - I'm thinking in particular of the Flash Airlines 737 where the Captain repeatedly called for re-engagement of autopilot as he unwittingly manually took it outside of the envelope.

FWIW, while some of what sadpole said is true, some of the prejudice he showed in that post really rubbed me up the wrong way.

[BOAC]

Flash Airlines 737 - is really in another arena. What I am trying to establish is whether the UAS QRH action PROMULGATED BY AF at the time of 447 was as described.

[DozyWannabe]

- is really in another arena. What I am trying to establish is whether the UAS QRH action PROMULGATED BY AF at the time of 447 was as described.

Apparently so [Page 2]:

http://www.bea.aero/docspa/2009/f-cp090601.en/pdf/annexe.06.en.pdf

There was some debate over the "safe conduct" clause preceding it, but nevertheless, the first two memory items are AP/FD and A/THR to "OFF".

[A33Zab]

@HN39:

Accuracy of the vane sensor = +/- 0.3° at 100kts.


---

About the FMGEC voting logics:

The FMGEC uses different logic to compare the inputparameters.
The logics used are by voting, passivating or two by two comparision and/or a combination of those.

For the airspeed (considered as slow changing parameter) the two by two comparision is made on the (ADR) monitoring side of all 3 sources (ADR OWN, O3 and ADR OPP-osite), the result of this is passivated to the command side which only receives parameters of ADR OWN and ADR #3.
(the command parameters are following the selection of the ADR source selector however will revert to the good source if the selected source is considered not to be good, as it was in AF447 between 02:10:46 and ~02:11:07.

Already said before it is rather complicated, one parameter may pass the logic while an other parameter could 'reject' the ADR as being unreliable.

The two by two comparision example:

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

[BOAC]

Thanks, DW - my French was not up to the other link! I think it is fair to say, however, that the AD is much clearer in both layout and explanation. As you say, the 'Safe conduct' bit could well have caused problems, in particular if the 447 crew did not, for some reason, feel it was relevant, and they never got to the 'level off' bit where the FD OFF was heavily emphasised..

[infrequentflyer789]

If one assumes that the wind speed remains fairly constant
short term, such a baro inertial mixing scheme could be a valid
solution to the loss of air speed data, upon which so many other
subsystems depend.


There's your one teeny weeny problem right there. Wind speed might usually be fairly constant short term, but then pitots (properly heated) don't usually ice up either. Pitot icing is often in the vicinity of thunderstorms, and rapid changes in wind speed can be found... guess where.

In short, I think your scheme still has the common mode failure that the 3 redundant pitots have - the same external conditions may mess up the pitots and your inertial backup.

Additionally, you've now added another failure mode - if the pitot airspeeds vary wildly (but accurately) due to rapid air mass changes, is your inertial mixing going to vote out the correct data ?

[Lyman]

Do not forget that for three years on, the topic has been discussed ad nauseum; in that focus is lost the emergent conditions 447 experienced 2:10:04.6 instant. Safe conduct of the flight is the underlying parameter of any pilot; they do not need to begin differentiating and splitting hairs
the instant Speeds are lost. That is the emergency, and I defy any one here to state they would be available instantly to gauge coldly if the flight became endangered with the unexpected loss of a/p.

Assume one of sadpole's aces were flying? Does he coolly hold steady, to assess, knowing the flight is not in jeopardy? He does nothing with the stick as the airplane bounces and descends, rolls? Or does he make inputs to correct? The airplane was left maneuvering at a/p drop, and the initial corrections applied were correct. So the correct action has placed the handling pilot in harm's way: He is handling, and the response is not being assessed correctly by the ASI, his one true ally has quit. His reactions to the first eleven seconds are in the record, and it is these inputs that set the stage for disaster. the accident was born in these first eleven seconds, the cart had been upset. There is no going back, the crew was committed, by virtue of the unexpected change in instrumentation. With PNF's remonstrations to "go back down", we see the possibility for salvation. The PF rejected this verbiage, his instruments had just revolted, does he trust the second in command? Or does he buy time by placating him, and continuing his incorrect path? We know the answer.

The materials used to date the manuals must be examined closely, some of the dates and alterations are in disagreement, and some were "updated" without notation. I would direct anyone's attention also to a photograph in the final report, showing "Arm 36G" in the Rudder. It is completely different from the one supplied by BEA initially, the one that began the discussion of the Arm attachment discrepancies in the image with the text of their analysis. Closely inspect this photograph, please.

Dozy, are you sure the Stick shaker/pusher has been abandoned in favor of FBW? 50's technology? The 330 cannot fly with the best Stall Warn available? The Warn that trumps even the speed/AoA aural that was dismissed/ignore by the crew?

And the finest Stall recovery tool, the Pusher? Are you saying that Airbus will improve the aural qualities of its SW, and that will be sufficient?

So again, would 447 have benefitted from the Shaker/Pusher? I say yes, and I would question your position that she would not have possibly even entered the Stall with this equipment?

I would admit that furnishing the Shaker to a side stick might be problematic, and the Pusher to an electronic controls system as well.

[DozyWannabe]

@BOAC

This is pure speculation, but sadly it seems just as likely that the startle response was so complete that any thoughts of procedure never even got a look-in.

By saying this, I am absolutely not denigrating the unfortunate crew - as I said in the other thread, even the best have bad days.

...I defy any one here to state they would be available instantly to gauge coldly if the flight became endangered with the unexpected loss of a/p.

It could be argued that in those weather conditions, at that time of night, any deviation from normal operation has the potential to endanger the flight!

and the initial corrections applied were correct.

A pull to 15 degrees nose-up is certainly *not* correct, no matter which way you slice it.

Dozy, are you sure the Stick shaker/pusher has been abandoned in favor of FBW? 50's technology? The 330 cannot fly with the best Stall Warn available? The Warn that trumps even the speed/AoA aural that was dismissed/ignore by the crew?

History has shown that even with a stick shaker, crews can and will disregard a stall warning if it does not fit their mental model of how the flight is proceeding.

And the finest Stall recovery tool, the Pusher? Are you saying that Airbus will improve the aural qualities of its SW, and that will be sufficient.

Aural *and* visual - it can't do any worse than the shaker and pusher have done historically.

The stick pusher is not the "finest" anything - it was a product of its time. If you read HTBJ you'll find anecdotes from DP Davies about how many contemporary line pilots hated the thing and didn't trust it. Whether that enmity was justified or not, the fact is that stick pushers were only ever compulsory on G-registered aircraft of a certain vintage.

It can be argued that the pusher was really only necessary on T-tail aircraft, as the conventional empennage layout is not susceptible to the "deep stall" condition - and in fact aeronautical engineers design airframes to develop a nose-down tendency at the stall without requiring control input. The A330 is no exception - in this case the natural tendency was defeated by the PF who held the primary flight controls in a nose-up position for the majority of the sequence.

Modern aircraft with yoke controls retain the shaker (which can be - and has been - ignored with fatal results), but the pusher has moved into history across the industry. The FBW designs from both major manufacturers, rather than providing automatic stall recovery, instead try to prevent the aircraft from approaching stall in the first place, whether via hard protections in the case of Airbus, or by increasing opposing yoke force in the case of Boeing - and as I said above, the aircraft are designed to naturally nose-down at the stall. Sadly, no amount of design can prevent human interaction from defeating the failsafes.

[HazelNuts39]

Accuracy of the vane sensor = +/- 0.3 at 100kts.Thanks, A33Zab.

Let's assume that the accuracy varies as the inverse of dynamic pressure, then it would be +/- 0.8 at 60 kts, and +/- 3.3 at 30 kts. Perhaps the stall warning computer could take those tolerances into account?

It may also be possible with the data from wind tunnel tests and AF447 to expand the airspeed indicating PEC (pressure error correction) table to higher AoA's, to reduce the IAS error at high AoA.

[dClbydalpha]

Sadly, no amount of design can prevent human interaction from defeating the failsafes.

I agree with the sentiment but not the fact. It would be very easy to design a system that totally ignores the human. However conventional wisdom dictates that this should not be the case. The human must have the final say, that is what the regulations say, and so there will always be scope for human error as well as system failure. All these designs have been through massive amounts of scrutiny against these aims.


The idea of combining > 1 independent, limited reliability
sources to improve overall performance is not new.

But to get this to work then the two systems must be 100% correctly characterised otherwise the potential for one to mislead both is always one step away. In fact a modern airliner has systems that can perform a sense - effect loop many 100 times faster and more accurately than a human whilst the human can take decisions that without some very exotic AI the computers can't get close to. Unfortunately the interaction of the two is never perfect and that is what system designers strive for. In this instance I'm not sure the combination of sensors would have made any difference. With the loss of all primary air data, the system would still have to hand control back to the human. The airworthiness authorities basically demand it. In reference to the example, how many combined GPS/Inertial sensors are certified by a civil air authority for navigation?


There other ways to measure air speed, such as the airbus developed
laser measuring system.

Please tell me how. Can a purely laser based system provide a calibrated airspeed? From what I understand, it can tell you how fast the air is moving, but at 37,000ft that is pretty meaningless to the aerodynamics, how does it sense the air density?


With the current design, the 3 pitot tubes are not only of the same type and same manufacturer, but they are also located pretty much in the same place - under the nose...

Placement of the pitot tubes is determined by the need to achieve the most consistent and correct airspeed. The separation is sufficient to ensure they are independent from the point of view physical damage. However icing is and always has been a problem. That is why they have heaters in them. But it is possible for nature to throw something at you that is beyond that capability. No matter how you separate them they will always be subject to icing.

To me there are many lessons to be learnt. Perhaps in the event of unreliable airspeed the AoA indication should become more prominent. Perhaps the stall warner inhibition should only be below a certain radio altitude. Perhaps, perhaps, perhaps. There are perhaps 100s of improvements that can be made, but each one must be considered and the impact on all phases of flight and all types of operation must be analysed before implementing them. I can't subscribe to the idea that the current design is somehow "incomprehensible" or "technically flawed" it is fairly standard from what I see, and follows well established principles. We shouldn't look at one small sub-set of operation and criticise it in isolation, or try to correct it without considering the effect on the whole system. In my opinion, the overall system failed catastrophically because of poor interaction and breakdown of communication between the aircraft and the pilot, the causes need to be established and corrected without introducing more dangerous failure modes.

[roulishollandais]

@henra

Conditions of "validity" are unclear, here, what is "valid" (two ADR and two IR FMGEC), when is it "valid", aso.
Which max difference is acceptable from one ADR to another ADR, from on IR to another IR, aso. A33Zab's shematic is unclear too, "compare" is unprecise, as there are difference which are acceptable, and in + or in -, so the shematic is much more complicated1.6.9.2 Pilote automatique, directeur de vol et auto-poussée
{...}
Pour fonctionner et pouvoir élaborer les ordres des FD, les FMGEC ont besoin d’utiliser les données d’au moins deux ADR et deux IR, qu’ils doivent pour cela considérer valides. Les surveillances faites par les FMGEC sur les paramètres ADR et IR sont des surveillances d’écarts deux à deux. Si l’un des paramètres d’une ADR s’écarte par exemple des valeurs du même paramètre des deux autres ADR, la première sera considérée invalide et ne sera pas utilisée. Si au moins deux ADR ou deux IR sont invalidées, le FMGEC ne peut plus élaborer les ordres du FD et les barres de tendance
disparaissent. Cependant les FD ne sont pas désengagés ; les voyants correspondants au FCU restent allumés.
Note : dans la suite, on parlera de FMGEC valide lorsque les fonctions AP/ATHR/FD sont disponibles.

[syseng68k]

infrequentflyer789, #288


There's your one teeny weeny problem right there. Wind speed might usually
be fairly constant short term, but then pitots (properly heated) don't
usually ice up either. Pitot icing is often in the vicinity of thunderstorms,
and rapid changes in wind speed can be found... guess where.
Agreed, but in the existing system, pitot data will be subject to filtering
and may already include historical data to provide some sort of predictive
capability. The processing will reject out of range transient data. When a
storm is entered, things get more dynamic, but again the software will adapt
to this, changing it's filter parameters if required, to optimise the
measurements. If this were not already the case, flight deck values would be
unreadable.


In short, I think your scheme still has the common mode failure that the
3 redundant pitots have - the same external conditions may mess up the
pitots and your inertial backup.

Additionally, you've now added another failure mode - if the pitot airspeeds
vary wildly (but accurately) due to rapid air mass changes, is your inertial
mixing going to vote out the correct data ?
It depends on how the data is processed and it's not a case of one data source
or the other in competition, rather a synthesis of the two, where the error
characteristics of both are given less weight in the calculations and the
strengths given more weight. The idea is to model the characteristics of all
the sources under all conditions of operation. The filters and processing can
then be matched to provide a more accurate and consistent result than from either
source alone. A more robust system in terms of transient events and redundancy...

[syseng68k]

dClbydalpha, #292

Sorry, missed this:


In reference to the example, how many combined GPS/Inertial sensors are certified by a civil air authority for navigation?
No idea, but have seen examples of gps in lrg ins units
(Ferranti) that date back to the early nineties, so it's not exactly a
new idea. If it's not used in civil aviation, it's not because of the lack
of well proven technology.


Please tell me how. Can a purely l@ser based system provide a calibrated
airspeed? From what I understand, it can tell you how fast the air is
moving, but at 37,000ft that is pretty meaningless to the aerodynamics,
how does it sense the air density?
The first result from plugging:

"airbus laser based air speed measurement" into google:

Airspeed measured by laser | NRL Annual Report 2009 (http://annualreport2009.nlr.nl/en/safety/airspeed-measured-by-laser)

It will come, not a matter of if, but when :-)...

[roulishollandais]

@syseng68k
HN39, IF789 seem to have the same frustrations as iself with the final report's unsuffisant precision : all that is litterature, "communication" for commercial use, not science, not proofs...:(

[mm43]

A March 2012 comprehensive update on the NLR Daniela Project (http://reports.nlr.nl:8080/xmlui/bitstream/handle/10921/470/TP-2012-068.pdf?sequence=1) - a PDF file.

[Lonewolf_50]

We are all at potential risk of failing if the conditions are too far out of our personal comfort zones .. indeed, as is observed periodically, the simulator can be used as an instrument of torture to overload any pilot to the point where he/she cannot cope and, hence, fails. Pointless exercise but it happens.
Not completely pointless.

I posit for you three different crews, A, B, and C.

I sit as master torturer running the sim, and proceed to add task loading (via failures and malfuncitons) to the point where the crews fail. As we have discovered, we can usually find a way to task saturate nearly anyone, and nearly any crew.

For the sake of illustration:
After cascading seven failure tasks, Crew A are done for.
Cascading of 9 failure tasks does in Crew B.
Cascading of 13 failure task finally does in Crew C, and the sim torture master only had one more trick up his sleeve. :E

As each crew ultimately fails at a different level, I as training department, or as chief pilot, or whomever, have some information upon which to help inform who needs work on what, in terms of the training and proficiency requirements and systems knowledge.

Likewise, the crews may, after giving me the occasional dirty look, be aware on their own of some limits or holes in their knowledge of systems that they were not previously aware of. <== That is crucial to most pilots I have ever met, all of whom like to be good at what they do and tend to correct or improve areas where they find themselves not up to scratch.

For What It's Worth, not without value.
In the commercial world, however, there is a fine decision to be made due to cost of sim time, in terms of how often and how brutal, and what to emphasize. There are not infinite training funds.

[bubbers44]

Dozy, I agree with what you are saying. If they hadn't pulled the nose up to 15 degrees none of this would have happened.

Software isn't going to prevent a repeat of this event, competent pilots who know how to fly without an autopilot will. Unfortunately this breed is going away and Airbus convinced everybody that stall recovery is not required in training because the bus won't stall in normal law.

UAS checklists are in all airliners and would have prevented this crash if used. The PF thought he was protected when he pulled back the SS. They were not in normal law so they stalled. Both pilots in the cockpit needed the autopilot to fly with no airspeed.

[DozyWannabe]

Unfortunately this breed is going away and Airbus convinced everybody that stall recovery is not required in training because the bus won't stall in normal law.

Well, hold on just a minute. Airbus said you can't stall the aircraft in Normal Law - but it doesn't follow that such a statement should convince anyone that stalls won't happen. To my mind, airlines didn't ask the important question of what happens if the aircraft *isn't* in Normal Law before making decisions on training. The same thing happened 40 years ago when Douglas assured the industry that losing all three hydraulic systems on the DC-10 was impossible. Thankfully the captain on the flight where Douglas was proved wrong didn't buy it for a second and used his seniority to train himself how to fly the thing on asymmetric thrust.

The PF thought he was protected when he pulled back the SS.

With all due respect, that's conjecture - there's not enough evidence to say why he pulled up the way he did.

Airbus have had their problems over the years, for sure - but to say they're largely responsible for the decline in hand-flying skills is like arbitrarily blaming Ford for the fact that so few Americans can drive a stickshift - the industry and customers moved in a certain direction, and Airbus (and Boeing, MD etc.) supplied products to fit that demand.

The truth is that with ever more crowded skies, automation is going to be more necessary than it has been in the past (with the advent of GPS and RVSM airspace) in order to maintain a degree of safety in traffic. This is a distinct issue from the lack of training for situations where the system fails however - PJ2 did a rapier-sharp dissection of industry attitudes on the previous thread, but what it boils down to is the trend whereby more and more senior airline management have never developed specialist skills relating to the industry, instead being purely business-orientated.

[Lyman]

Dozy

Your "15" degrees PITCH UP I believe came from the DFDR, via ins and archive. You know the Pitch attained was not nearly that high, in the initial command post a/p loss. Once maneuvered, there ceased to be a comfortable baseline, and his PITCH was not available via INS, and you have no idea whatever what the cockpit was like, you just don't....No PITCH was ever spoken in the CVR, only "you go up....so go down..." "Am I in climb?" So your reference to a specific PITCH value from the DFDR is completely "out of your seat cushion"....I submit PF's grok of PITCH was never accurate, and from the evidence, there is NO way to know what they saw, or believed......via their instruments....

[DozyWannabe]

Your "15" degrees PITCH UP I believe came from the DFDR, via ins and archive. You know the Pitch attained was not nearly that high, in the initial command post a/p loss.

He yanked the sidestick halfway back the second AP disconnected Lyman - there's no getting round that.

I submit PF's grok of PITCH was never accurate, and from the evidence, there is NO way to know what they saw, or believed......via their instruments....

Yeah, the instruments were clearly lying or absent and the aircraft tricked him into crashing. Truly, denial is not just a river in Egypt and I don't see the point in continuing this debate.

[john_tullamarine]

Re this post (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-15.html#post7292580) .. sideline philosophical consideration ..

As each crew ultimately fails at a different level, I .. have some information upon which to help inform who needs work on what....

Likewise, the crews may .. be aware on their own of some limits or holes in their knowledge of systems that they were not previously aware of.

My original comment was directed at routine sim work and I stand by the philosophy for routine (training value emphasis with a lower case "c" checking strategy) sim work.

In the specific circumstances you cite, I am with you .. indeed, I would be in the line to participate for the reason you consider .. just where is my personal brick wall ? The underlying research value for training strategies is valid .. but the participants must be willing and not at jeopardy.

Perhaps we should have a beer or ten to debate the pros and cons ?

[OK465]

...just where is my personel brick wall ?

Perhaps we should have a beer or ten to debate the pros and cons ?

727 2-engine out, manual reversion, NDB approach to NDB minimums was essentially a one maneuver check-ride.

What was most interesting, was not who succeeded or failed at the maneuver, but who would be enthusiastically willing to attempt it.

[bubbers44]

With all due respect, that's conjecture - there's not enough evidence to say why he pulled up the way he did.

Then why did he pull up into an impossible climb that all of us know would end up in a stall? No airliner can go into a 15 degree climb at FL350 and not stall. He either trusted Airbus protections in normal law or was incredibly stupid. I think somewhere in his training he was told you can't stall in normal law so pull it up and let the automation handle it. These two spent most of their careers monitoring autopilots so probably depended on them a lot more than us old timers to fly the airplane.

The cockpit voice recorder shows how confused both pilots were when AS and AP went away. It didn't happen like that years ago before full automation took over.

[DozyWannabe]

Then why did he pull up into an impossible climb that all of us know would end up in a stall? No airliner can go into a 15 degree climb at FL350 and not stall. He either trusted Airbus protections in normal law or was incredibly stupid.

That's two possible conclusions. Other conjecture has included the ideas that he tried to chase the intermittent FD bars and/or that the pull up was a panic reaction - and through a possible combination of body-clock offset, having just come off of holiday (and still getting used to being back in the saddle) - or even just that the shock completely threw him, all training went out the window.

Unfortunately there'll never be any irrefutable proof which of these theories, or any combination of them, caused him to react the way he did.

I think somewhere in his training he was told you can't stall in normal law so pull it up and let the automation handle it.

I've said this before, but it's very important to draw a distinction between FBW/protections and automation (in the autoflight sense). The ColganAir Q400 did not have FBW or protections and yet the captain still pulled the aircraft into a stall when the warning startled him.

The distinction is important because (for better or worse) a pilot expects to be using the automation on almost every flight, whereas in an ideal world the pilot would never have to rely on the protections (and in the real world, most never have). The protections are there primarily to help the pilot stay within the load limits of the airframe when aggressive maneouvres are required - but in this case there was no requirement for an aggressive maneouvre and hence no need to bring the protections into play.

These two spent most of their careers monitoring autopilots so probably depended on them a lot more than us old timers to fly the airplane.

The "old timers" didn't have to deal with RVSM airspace. :)

More seriously though, the industry needs to have a serious look at maintaining basic aeronautical knowledge, now that automation has become a necessity.

The cockpit voice recorder shows how confused both pilots were when AS and AP went away. It didn't happen like that years ago before full automation took over.

It did on Dynasty 006 in 1985 and Eastern 401 way back in 1972. We need to be careful when generalising.

[bubbers44]

Yes, pilots have made stupid mistakes in the past and will in the future. We have made wonderful improvements in GPWS and TCAS so flight safety is better than ever before. We just need to not let the pilots become monitors of autopilots instead of pilots in my opinion.

In my career I had to continually improve my basic skills because the airline didn't. You don't have to rent a Cessna, just disconect the autopilot and fly on raw instuments when it is appropriate. Why would you want your basic piloting skills going away because the airline you fly for doesn't care?

You should care.

[DozyWannabe]

You don't have to rent a Cessna, just disconect the autopilot and fly on raw instuments when it is appropriate.

The problem is that the number of appropriate points where this is possible is dwindling.

You should care.

I do - otherwise I wouldn't be here! :)

[jcjeant]

Why would you want your basic piloting skills going away because the airline you fly for doesn't care?

You should care. This is the kind of recurring comment
I wonder why fly in manual seems to be a problem for pilots who always invoke some of their company regulations
In fact is that these regulations have the force of law ?
Is there a law that prohibits pilots fly manually ?
Is that pilot can legally be put out of work for this action?

[Machinbird]

This is the kind of recurring comment
I wonder why fly in manual seems to be a problem for pilots who always invoke some of their company regulations
In fact is that these regulations have the force of law ?
Is there a law that prohibits pilots fly manually ?
Is that pilot can legally be put out of work for this action? Unfortunately, some of the large but unenlightened airlines do hold to a punitive view of what pilots should do and should not. I recall a recent post in the Rumors section where a Captain was quite certain that he would receive an invitation to "tea and dates" with the chief pilot should he choose to practice his manual flying skills outside the narrowly constrained takeoff and landing portions of the flight. Apparently the statisticians at his airline had built some sort of case that to do so increased the risks.

To my mind, this is the short term risk avoidance getting out of balance with the long term consequences of such a strategy. Of course, if they bring in highly trained crew continually into their operation and flush them out of the system after ~4 years or so, then the consequences of their short sightedness could well fall to someone else.:*

[Lyman]

Hi Mach.

From above... "Apparently the statisticians at his airline had built some sort of case that to do so increased the risks."

The statistician is correct of course, at any given time, manual flight is more risky than autoflight. Clearly, the case can be made that it is "Training", a more demanding regime than auto cruise. In my view, the ball is in the regulator's court, and it would take a pro-active reg to cause the lines to upgrade hand skills.

Besides nil, zip, and no chance, what do you think?

[slats11]

Airbus have had their problems over the years, for sure - but to say they're largely responsible for the decline in hand-flying skills is like arbitrarily blaming Ford for the fact that so few Americans can drive a stickshift - the industry and customers moved in a certain direction, and Airbus (and Boeing, MD etc.) supplied products to fit that demand.

True. But pilot and aircraft are inter-dependent. The aircraft design is clearly to revert to the pilot in the event of a problem.

An inherent assumption in this design is that the pilot is capable to manually fly the aircraft - without warning, at cruise altitudes, and with degraded systems or data. Increasingly, this assumption may not be entirely valid. What training is required by the operator? What is covered in the sim? Is regular maintenance of manual flying skills permitted by the operator?

Truth is often the first casualty of war. And it may be hear with the lawyers circling and large sums at stake.

However we need to ask ourselves if something has fallen into a crack somewhere between the designer / manufacturer, and the pilots. If there is such a crack, it is only a matter of time before someone else falls into it.

[DozyWannabe]

However we need to ask ourselves if something has fallen into a crack somewhere between the designer / manufacturer, and the pilots.

As I said, I don't think the crack - if indeed there is one - falls between the designer/maufacturer and pilots (after all, pilots were involved in the design of the Airbus FBW systems). I think the disconnect is between airline management and the pilots that work for them, because the breed of management that started to proliferate towards the end of the '80s were pure MBA material, and the old-school management who saw aviation as a specialty all began to retire.

[Lonewolf_50]

John T: good points!

As seems to have happened pre AF447, and probably still happens, sim "training," or more importantly sim sessions with "x" on the line, may not be designed nor used to do a "training" function but instead confirm adherence to standard policies and practices, or to highlight subtle changes or revisions to same. "Gents, as you know, there is a new SOP on CAT III approaches. You've read the bulletin, let's see that you know how to put it into place during this sim session!" (And other tasks, of course ... )

There is value for any organization in doing that. There is solid argument to be made against conducting training on revenue flights, since the pax didn't sign up for other than "get me from point a to point b."
In the specific circumstances you cite, I am with you .. indeed, I would be in the line to participate for the reason you consider .. just where is my personal brick wall ? The underlying research value for training strategies is valid .. but the participants must be willing and not at jeopardy.
Respectfully, I contend that any Airline company that does NOT invest in its human capital -- pilots-- as I had previoulsy suggested, in which actual Training, refresher, and currency are deliberate and well defined aims of their precious and expensive simulator time, are wasting time that they pay for. Not seeing the forest for the trees, perhaps.
Perhaps we should have a beer or ten to debate the pros and cons ?
Indeed. :ok:

I suggest that it is in the self interest of any airline to keep its crews sharp, and deeply systems knowledgeable. The better you know your systems, inside and out, the better you can do your job and complete your mission.

Adopting that attitude reduces their (company) risks and increases their (company) success rates of "malfunction/emergency sorted" when things do go wrong.

I do not believe that I am the only person who holds that position.

Problem is, I don't run an airline and thus am in no position to make an impact. That a clear and careful implementation of this philosophy, as you describe it, has to go hand in hand with how to fund it presents any airline management -- or leadership if there is any -- with a critical problem to solve.

Well, that's why those folks in suits are paid.

I have a few :mad: ed thoughts on what I think of MBA's who aren't pilots running airlines ... but that does not belong in this thread.

AF447 has to me shown that Air France (and perhaps a good portion of the industry?) does not make the points I allude to above a priority. (I may be overstating this, or may simply be wrong.) Maybe the idea I have would be that they have a system in place that doesn't achieve that end even if that were its intention.

Result: a crew unable to fly and CRM its way through a malfunction, with fatal results. From the CVR excerpts released, I get the impression of a crew that were trying and trying to get the situation under control, but they were trying the wrong things to resolve their malfunction. (And one could argue that the "how" of their trying, as a crew, was not what we have come to expect).

An analogy to some of my own experience would be something like this: in a helicopter while flying above the high seas, experiencing a loss of tail rotor control during IMC conditions, but treating it as loss of tail rotor thrust or an AFCS malfunction. Could have ended in tears, were I and my H2P to respond to such a malfunction, as a crew, incorrectly.

[PJ2]

BOAC, re post #284 (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-15.html#post7292073), "What I am trying to establish is whether the UAS QRH action PROMULGATED BY AF at the time of 447 was as described."

If I may leap in on your question to Dozy, the QRH drill and checklist did not reflect the EASA AD Procedure, which is:

PROCEDURE:
When autopilot and auto-thrust are automatically disconnected and flight controls have reverted to alternate law:

- Do not engage the AP and the A/THR, even if FD bars have reappeared
- Do not follow the FD orders
- ALL SPEED INDICATIONS...........................X-CHECK

 If unreliable speed indication is suspected:
 UNRELIABLE SPEED INDIC/ADR CHECK PROC...........APPLY

The QRH drill has essentially remained the same from November 2002:

IMMEDIATE ACTIONS
- AP/FD........................................OFF
- A/THR........................................OFF
- FLAPS........................................MAINTAIN CURRENT CONFIG
- SPEEDBRAKES............................CHECK RETRACTED
- L/G............................................UP WHEN AIRBORNE

IMMEDIATE PITCH ATTITUDE AND THRUST GUIDANCE
If the failure occurs before thrust reduction:
- THRUST LEVER...........................TOGA
- PITCH ATTITUDE.........................12.5°

If the failure occurs after thrust reduction:
- THRUST LEVER............................CLB
- PITCH ATTITUDE below FL 100.......10°
- PITCH ATTITUDE above FL 100.......5°

RESPECT THE STALL WARNING

WHEN FLIGHT PATH STABILIZED
- PROBE WINDOW HEAT...................ON
- ATTITUDE/THRUST........................ADJUST

The AD was to be incorporated into the applicable AFM 15 days after the effective date of the AD, (Jan 05, 2011).

Of interest is a note regarding the AOM, "the Aircraft Operating Manual is not intended to provide basic piloting skills, basic jet aircraft piloting techniques, or information that is considered as basic airmanship for trained flight crews familiar with that type of aircraft and with its general handling characteristics."

J.T., Re post #303 (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-16.html#post7292699), "Perhaps we should have a beer or ten to debate the pros and cons ?"
Re training vice checking, and jeopardy vice non-jeopardy, you should have seen the debates when we introduced LOFT!

The politics of failure and the underlying struggle for who controls who...regulator, airline, union, individual pilots - what a time.

Agree with all your comments on the sim. That said, I think there is reason to accept that "extrapolated" sim behaviour at and in the stall may not be that far from the airplane even though the regime is unflown, untested and has no data from such events. Because even a Level D isn't certified for here-be-dragons territory, it could only be used informally during any training. The primary difficulty has been the methods by which the AF447 circumstances are repeated, because the loss of pitots was not a separately-programmed scenario so the results had to be simulated using other methods and that can produce system behaviours that may not obtain in a loss of pitot(s) data.

[HazelNuts39]

(...) the pusher has moved into history across the industry. The FBW designs from both major manufacturers, rather than providing automatic stall recovery, instead try to prevent the aircraft from approaching stall in the first place, whether via hard protections in the case of Airbus, or by increasing opposing yoke force in the case of Boeing - and as I said above, the aircraft are designed to naturally nose-down at the stall. The rules haven't changed, so an airplane that doesn't meet the stall characteristics requirements without a stick pusher will still need one. What you have written applies to FBW airplanes. The FBW system permits modification of the natural characteristics of the airplane so that it meets the requirements. The Final Report describes the type certification in section 1.18.1.

While the airplane flight control system is designed so that, in normal law, the pilot or the A/P cannot command an AoA greater than alphamax, and therefore cannot stall the airplane in the 'usual' way, the system apparently can provide a powerful nose-down pitch very similar to a stick pusher if alphamax is exceeded in any other way.

[jcjeant]

Hazelnut39
While the airplane flight control system is designed so that, in normal law, the pilot or the A/P cannot command an AoA greater than alphamax, and therefore cannot stall the airplane in the 'usual' way, the system apparently can provide a powerful nose-down pitch very similar to a stick pusher if alphamax is exceeded in any other way.
Indeed .. in normal law
What about the other laws (no more AOA protection) isn'it the return to a "normal plane" ? and so need stick pusher ? ...

[DozyWannabe]

@HN39

Agreed, but what Lyman was referring to was a physical stick push that actually moved the column/sidestick.

@jcj:

I'm pretty sure that the A330 meets the stall requirements such that a stick pusher is unnecessary. As I said, stick pushers were a technical solution to the T-tail "deep stall" issue, and while they were installed in some non-T-tail designs some decades ago, that was to satisfy a UK CAA mandate.

[Lonewolf_50]

PJ2: as I understand your post, the procedure you cite in the blue box is based on lessons learned from AF447, while the other procedural steps were in place at the time (per your observation "... essentially remained the same from November 2002") of the mishap. What I don't have clear is which symptoms were considered sufficient trigger to enter that series of procedures. (Airspeed unreliable, or A/P kicked off due to Airspeed Unrealiable?)

To ensure that I am speaking the same language:

Does "immediate actions" mean "memory items" or is that "break out the checklist/procedure and do these first" in a challenge/response style of ordered operations by the crew?

IMMEDIATE ACTIONS
- AP/FD........................................OFF
- A/THR........................................OFF
- FLAPS........................................MAINTAIN CURRENT CONFIG
- SPEEDBRAKES............................CHECK RETRACTED
- L/G............................................UP WHEN AIRBORNE

IMMEDIATE PITCH ATTITUDE AND THRUST GUIDANCE
If the failure occurs before thrust reduction:
- THRUST LEVER...........................TOGA
- PITCH ATTITUDE.........................12.5°

If the failure occurs after thrust reduction:
- THRUST LEVER............................CLB
- PITCH ATTITUDE below FL 100.......10°
- PITCH ATTITUDE above FL 100.......5°

RESPECT THE STALL WARNING

WHEN FLIGHT PATH STABILIZED
- PROBE WINDOW HEAT...................ON
- ATTITUDE/THRUST........................ADJUST

I presume that "adjust" in that last means "adjust to desired speed and power combination for continued flight."

[jcjeant]

DW
I'm pretty sure that the A330 meets the stall requirements The "approach to stall" requirements .. certainly (regulators requirement fulfilled .. or this plane can't fly commercially)
"The stall" requirements (if any) .. we don't know ... the A330 in stall situation was not tested ... AFAIK
BTW AF447 can't be considered like a valid test ..

[infrequentflyer789]

"The stall" requirements (if any) .. we don't know ... the A330 in stall situation was not tested ... AFAIK

Where do you have this information from ?

I would be very very surprised if the A330 wasn't stall tested. I know that other models have been (see eg. Airbus A380 Test Flight Program and Certification - YouTube about the A380 testing - see the comments on stall in the full description on youtube) and as far as I know it is required for certification.

The A330 (and in fact any airliner) will not have been tested to the AOAs that 447 went to (this may be what you are confused on?). Nor will it ever. As I think someone else already posted recently, no one would be suicidal enough to try the 447 stall in the real a/c (and therefore there is no real data for recovery profile in the Sim either - it's all extrapolated).

[HazelNuts39]

What about the other laws (no more AOA protection)Conditions other than normal law are associated with system failures. Section 1.18.1 of the final report describes how these are addressed in the certification requirements.

[jcjeant]

infrequentflyer789
The A330 (and in fact any airliner) will not have been tested to the AOAs that 447 went to (this may be what you are confused on?). Nor will it ever. As I think someone else already posted recently, no one would be suicidal enough to try the 447 stall in the real a/c (and therefore there is no real data for recovery profile in the Sim either - it's all extrapolated). I see at 18 sec (and more) in the video people with a parachute on their back .. :)
So .. if this is possible (apparently) to evacuate the A380 in case of danger .. I see nothing suicidal to test stall like the of AF447 (the most risk is to end with a smoking hole in the ground)

[Lyman]

My original challenge to Doze was re: the Shaker. The recommendations of BEA re: STALLWARN gave me the impetus to explore the elements in the region of Approach to STALL.

The STALL is interesting, but to me, I still believe the LOC was made possible by actions and mechanical insufficencies prior to the second STALL WARN. In Alternate LAW, why should the A330 be allowed to avoid installation of the shaker? Can we not see that an additional and different sensate device would have saved the day here?

What pisses me off is the sacred cow nonsense I see in the Certification side. Is it impossible to equip a SS with an annoying vibration that would startle the pilot into focusing on the impending death of his passengers and loss of his aircraft?

Without protections the 330 is no different in controls theory than non airbus vehicles. Besides, the Bus seems to know well enough not to remain in NORMAL LAW if it is in danger of STALLING. Very convenient as a sales tool. Impossible to STALL? Read the gd fine print, eh?

[DozyWannabe]

Can we not see that an additional and different sensate device would have saved the day here?

Well no, as shakers have been ignored several times in aircraft equipped with them, sometimes fatally.

[Lyman]

Look, Sir, it is getting tiresome that you expect to make a glib comment about a failure of some piece of equipment and expect others to accept your pronouncement as 'end of discussion'.

Nothing works perfectly, consider the STALLWARN in this accident, ok? Sometimes engines quit, shall we give up flying?

Why don't you take an objective guess at whether the Shaker may have helped here?

[PJ2]

Lonewolf_50;, Re, Does "immediate actions" mean "memory items" or is that "break out the checklist/procedure and do these first" in a challenge/response style of ordered operations by the crew?
The term "Immediate actions" refers to the memory items only.

As we know, this drill has changed over the years. Until sometime in 2008, the drill began with "Immediate Actions", with no qualifying condition. There's info on this on the web or in the IR/Final Rpt as to when it changed but I don't have the time at the moment to source it.

Sometime in 2008, the qualifying condition, "If the safe conduct of the flight is impacted:" was added to the same drill items.

The way the drill was then written effectively split the drill into two parts: "Impacted/Not impacted". If "impacted", one does the boxed items. If not, the next "dot point" is "To level off for troubleshooting", etc. I don't think this was ever really clear prior to AF447. This is partly because within the memorized items under the qualifying phrase, was a qualifying condition that catered to low altitude failures but would not be done if the safety of the flight wasn't impacted: "When at, or above MSA or Circuit Altitude: Level Off for Troubleshooting". So the guidance was confusing, in my opinion and I thought the immediate actions should be qualified by flight-phase, not the very subjective, "If the safe conduct...", etc.

So there is no real, obvious guidance for cruise ADR or UAS/pitot failures because the drill was originally conceived after the Birgenair and Aeroperu accidents.

Trouble is, UAS events on the A330/A340 in cruise first occurred prior to April, 1996 and many listed in the BEA reports had occurred by 2008 yet the drill remained unchanged. I think appropriate training would sort this drill and checklist out such that it could be done correctly but sorting it out for oneself leaves the drill open, as we see, for interpretation as to what to do and when.

The addition of this qualifying condition placed the notion of "Immediate Actions" in limbo...What was one to do first?

At takeoff, it is clear - the safe conduct of the flight is impacted and one does the memorized items.

In stable cruise, even with mild turbulence, what does one do? "Above FL100, set pitch to 5deg, (about 2.5deg higher than normal cruise) and get out the books, but was this ever trained?

I'm won't re-argue the case but in response to your and BOAC's comments, aside from the addition of the qualifying condition, the drill hasn't changed, and still (to my knowledge) has not incorporated the AD admonition to not engage the AP or FDs, and not to follow the FDs until at least two airspeeds are considered valid.

Lots to chew on yet.

Here's the 2008 QRH UAS drill:


http://www.smugmug.com/photos/i-sm2Jtgb/0/X3/i-sm2Jtgb-X3.jpg

[Organfreak]

Lyman, Dozy is against anything that "might have helped."

I can only be relieved that he's not in charge of any airline.

:bored:

[Turbine D]

Hi PJ2,

Relative to the QRH drill, I have some questions. As in the case of AF447, you are cruising at 350, M .82, 2.5º pitch and an N1 setting of 95% (as referenced on page 183 BEA's final report for level flight). Due to expected turbulence, a reduction in M is dialed in to .80 resulting in a reduction of N1 to 84% by AT. Suddenly the AP disengages, the AT disengages and AT lock occurs. At this point, according to the QRH drill, the pitch should be set at 5º and the thrust levers must be moved to climb detent at which point one needs to know from the tables to reset pitch and power based on the aircraft wight and altitude. My first questions would be aren't the thrust levers already in the climb detent? Does the thrust lock latch a 84% N1? if so, does this give much time to figure the right pitch and power setting before a real stall warning occurs?

But when I see the tables, the reset for pitch is 3.5º and 90% N1 for a M of .82 based on altitude and weight. This seems a little low on N1% with a 3.5º pitch setting based on what is referenced in the BEA report for level flight at the altitude being experienced. I recognize at the upper end of the power settings at 350 there isn't much power left to be had, but the differences seem confusing to me more than anything, perhaps I am missing some finer points. Any thoughts? Is my logic off?

P.S. The source of pitch and power table I used came from the BEA final report, Page 104. Additionally, the BEA Interim Report #3 gave the following N1% power settings from each engine as follows:
At M .82 - True N1% 100.4/99.8
At M .80 - True N1% 98/98

[DozyWannabe]

Lyman, Dozy is against anything that "might have helped."

No, I'm against blanket assertions that something *would* have helped when there is no evidence to support said assertions.

Adding complex mechanical devices would add more potential points of failure to the flight control system for no proven gain.

Yet again I can't help but suspect a slight bias towards "the Boeing Way".

[Lyman]

Organfreak Lyman, Dozy is against anything that "might have helped."

I can only be relieved that he's not in charge of any airline.

Unfortunately, the rhetoric that is being parroted is that of people who build and certificate the AIRBUS.

[Lyman]

The shaker is experienced thousands of times a day in training, and typing.

"No evidence there would be any gain?" What a wild statement.

[DozyWannabe]

The shaker is experienced thousands of times a day in training, and typing.

I don't know about thousands - maybe hundreds - and the same could be said of the Airbus auditory/visual warnings. Unsurprisingly, in training situations, pilots respond well to both.

"No evidence there would be any gain?" What a wild statement.

No, it's a true statement unless you can provide evidence to the contrary - a "wild" statement is insisting something would have helped when there is no evidence to support it (and plenty of evidence that overwhelmed crews ignore the shaker just as easily as any auditory or visual warning).

[PJ2]

Hello TD;

Re post #330 (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-17.html#post7294017):
My first questions would be aren't the thrust levers already in the climb detent? Does the thrust lock latch a 84% N1? if so, does this give much time to figure the right pitch and power setting before a real stall warning occurs?
Yes, you're correct - the TLs would be in the CLB detent already. The drill merely ensures that this is so, just in case they have been moved out of the detent for any reason.

Yes, again correct - the Thrust Lock would synchronize with the aircraft parameter at the time of disconnect. Eighty-four percent is sufficient to maintain stable flight for the time needed to bring out the QRH, (which should always be right at hand). The page hasn't changed in quite some time, (2.21 in Nav Abnormals). In fact a five-degree pitch attitude results in a gentle climb of around 800 to 1200fpm, (again, I was wrong on the original statements) - for an experienced crew, this would not present a problem as "close to nothing" has changed and one can return to level stable flight with tiny movements on the stick and observing the altitude and altitude trend, (rate of change). Digital vice analogue adds a cognitive step because the notion of "amount-to or -away from" is missing - no big deal.
But when I see the tables, the reset for pitch is 3.5º and 90% N1 for a M of .82 based on altitude and weight. This seems a little low on N1% with a 3.5º pitch setting based on what is referenced in the BEA report for level flight at the altitude being experienced. I recognize at the upper end of the power settings at 350 there isn't much power left to be had, but the differences seem confusing to me more than anything, perhaps I am missing some finer points. Any thoughts? Is my logic off?
No, your logic is sound - it takes a significant change in pitch or power to place the aircraft at risk of overspeed or stall during this drill. The settings given are very close to what the aircraft would require but they're not exact. Going from recollection of the FCTM here...I think an answer lies in the 10T weight category intervals. The FCTM does state that the settings are approximate and that fine-tuning involves monitoring altitude using either indicated or GPS altitude:

LEVEL OFF AND STABILIZATION (IF REQUIRED)
The table gives the proper pitch and thrust values to stabilize level flight according to weight and altitude.

If the altitude information is unreliable, the FPV and V/S are also affected. In this case, the GPS altitude, if available, is the only means to confirm whether the aircraft is maintaining level flight.

When the altitude information is reliable, use the FPV.

 If the FPV is reliable, or if the GPS altitude is available:

‐ Maintain level flight (FPV on the horizon or constant GPS altitude)
‐ Adjust thrust according to the table
‐ Observe the resulting pitch attitude, and compare it with the recommended pitch target in the table:

• If the pitch necessary to maintain level flight is above the table's pitch target, the aircraft is slow, then increase thrust,
• If the pitch necessary to maintain level flight is below the table's pitch target, the aircraft is fast, then decrease thrust.

When the pitch required to maintain level flight gets close to the table's pitch target, re-adjust thrust according to table's thrust target.

This technique permits to stabilize the speed quickly while maintaining level flight.

 If the FPV is not reliable and the GPS altitude is not available (no means to ensure level flight):

Adjust pitch and thrust according to table values, and wait for speed stabilization. Expect a significant time to stabilize and important altitude variations during the stabilization.


Hope this helps.

[henra]

Does the thrust lock latch a 84% N1? if so, does this give much time to figure the right pitch and power setting before a real stall warning occurs?


Stall did occur at ~180 -190 kts IAS. That is around M0,55.
That is a huuuuge way from M0,8 or 0,82 from a kinetic energy perspective.
So even at 84% you're lightyears awy from a stall.
It takes a significant climb to shed that energy. Thrust variation (short of a shut-down) has much less immediate impact on kinetic energy than a climb. If simply keeping altitude you have ample time to sort things out.

Edit: Stall warning would come on earler especially in Alt Law but with a constant altitude it should come up somewhere around 230 kts (M0,65 - 0,7)

[Lonewolf_50]

PJ, thank you very much, and also thanks to TD and henra for some amplifying thoughts.

I better understand what was, what is, and an idea for "what ought to be."

The industry as a whole, who fly AB 330's, will hopefully come to a consensus on a "best practice" regarding this malfunction family. What I gather from your observations is that perhaps the consensus has not yet been achieved.

[rudderrudderrat]

Hi DozyWannabe,

...and the same could be said of the Airbus auditory/visual warnings. Unsurprisingly, in training situations, pilots respond well to both.

Please see Page 105 of the final report:

"1.16.8.3 Response to aural warnings
Numerous studies have been conducted on insensitivity to aural warnings and they showed that the aggressive nature, rarity and unreliability of these warnings may lead operators to ignore these signals [1, 2]. In particular, in the event of a heavy workload, insensitivity to aural warnings may be caused by a conflict between these warnings and the cognitive tasks in progress. The ability to turn one’s attention to this information is very wasteful as this requires the use of cognitive resources already engaged on the current task. The performance of one of these tasks (solving the problem or taking the warning into account) or of both would be affected [3].
In addition, studies on the visual-auditory conflict show a natural tendency to favour visual to auditory perception when information that is contradictory and conflicting, or seen as such, of both senses is presented [4, 5, and 6]. Piloting, calling heavily on visual activity, could lead pilots to a type of auditory insensitivity to the appearance of aural warnings that are rare and in contradiction with cockpit information.
A recent study in electrophysiology on a piloting task seems to confirm that the appearance of such visual-auditory conflicts in a heavy workload situation translates into an attention selectivity mechanism that favours visual information and leads to disregarding critical aural warnings [7]."

Having the stall warning alert only via the auditory channel is not a good design during high work load situations.
If you were busy arguing with Lyman in a noisy party and I wanted to get your attention, the most effective way would be by touch (on your arm or shoulder say). It's a completely separate channel with no competition from any other warning - as is the stick shaker.

[Turbine D]

Hi PJ2,

Thanks for the response to my questions, much appreciated.

[dClbydalpha]

From what I've read I don't believe that Dozy was saying a Stick Shaker wouldn't benefit. Simply that you can't look at it from your armchair and say "that's the solution". You need to look at the whole system and work out the pros and cons. If I read the report correctly, in this tragic situation the pilot ignored the aural warning, ignored the instruments and even ignored the other pilot in the cockpit. He had become fixated completely and if he was ignoring all of those I would guess, and it is a guess, he had a mental picture where he no longer believed what the systems were telling him, if that is the case then there is a real possibility he would have ignored the stick shaker as a false indication too.

As for the crowded noisey room scenario, have you ever tried to break up a fight just by tapping someone on the shoulder?

I will also question why some people on this thread are obsessed with a stick shaker. This aircraft had a system that could have safely restored level flight had it been re-engaged. So, instead of putting a stick shaker in, why not allow the system to take control again if it is convinced that the aircraft is in danger of exiting the envelope?

The system is designed to respect principles that have been held sacred for several decades. The safety analysis is extremely stringent and forces decisions into the design that when analysed against a very specific set of conditions doesn't seem to make sense. If you step back and look at the whole picture, with all the analysis at your disposal, it makes more sense. Of course nothing is perfect, and it takes such events as this to expose weaknesses in the design decisions. However in these cases it is very rare for the fix to be simple. The system has to be re-analysed.

I have read a lot of comments on these threads, many seem to be from people who, from what they've written, appear to have never been involved in designing, clearing and certifying a complex avionic system. But even in their position of ignorance they are quite happy to throw rocks at the Airbus design team.

In my view of this tragic event, the aircraft let down the pilot by suddenly exposing him to a set of conditions that caused him to lose situational awareness and expecting him to run with it. The pilot let down the aircraft by not carrying out the basic tasks required to return the aircraft to safe steady flight. The reasons this happened are no doubt deep and wide going way beyond just the pilot and the aircraft, the lessons will be many and varied and hopefully will lead to changes that improve safety all round.

What scares me is for how little a span of time the airspeed was unreliable and how quickly this event went from routine to catastrophic. What saddens me is that perhaps in 99 time out of 100 this pilot would have correctly interpreted the situation and it would have become a none event.:sad:

[DozyWannabe]

Having the stall warning alert only via the auditory channel is not a good design during high work load situations.

Which is why they've recommended bumping up the visual component, at a guess... :)

If you were busy arguing with Lyman in a noisy party and I wanted to get your attention, the most effective way would be by touch (on your arm or shoulder say). It's a completely separate channel with no competition from any other warning - as is the stick shaker.

Heh.

I'm well aware of the theory that the tactile channel - as separate and distinct from audio-visual - can get attention when audio-visual can't, and it makes sense in terms of pure logic and psychology. This doesn't alter the fact that in times of high stress workload in the flight deck, shakers have been ignored multiple times. The only way to know for certain would be to blind-test the two methods, but I don't see that happening any time soon.

[Clandestino]

Ladies and gentlemen, dear PPRuNers, honourable participants in our discussion, I would like to take an opportunity to kindly ask you to get acquainted with The Book:

http://www.pooleys.co.za/images/Handling%20big%20jets.jpg

It will do you a lot of good and also might help reduce the PPRuNe bandwidth wastage.

If you have third edition on your bookshelf, you might find the following chapters useful:

Pg 109, Stalling, which shows that pilots' wildly divergent views on the subject of stalling have preceded PPRuNe by decades. Also displays DP Davies fantastic ability of insight, in matters not just technical but also in human nature.
Pg 128, Stick shakers.
Pg 130, Stick pushers.

Stickshakers are not supposed to be universal stall warning devices! They are fitted to aeroplanes that have no pronounced natural pre-stall buffet or margin between buffet and stall is to thin for buffet to be used as effective deterrent. Why A330 doesn't have it installed? Two possible clues in the final report.

Airbus subsequently flew special flights to collect more accurate data at high angles
of attack and with an aircraft configuration close to that of the accident (mass, flight
level, Mach, etc.). These tests made it possible to refine the preliminary correlations
and to establish that the level of buffet was considered to be a deterrent by the test
pilots when the angle of attack was about 10°, corresponding to normal acceleration
amplitude of 1 g at the pilot’s seat.

When there are no protections left, the aeroplane no longer possesses positive
longitudinal static stability even on approach to stall. This absence specifically results
in the fact that it is not necessary to make or increase a nose-up input to compensate
for a loss of speed while maintaining aeroplane altitude. This behaviour, even if it
may appear contrary to some provisions in the basic regulations, was judged to be
acceptable by the certification authorities by taking into account special conditions
and interpretation material. Indeed, the presence of flight envelope protections
makes neutral longitudinal static stability acceptable.So 330 both shakes out of her own accord and did receive some special dispensation in certification process by virtue of her envelope protection.

Now about stick pusher: it is not stall recovery device, it is stall prevention device! It has to be fitted to aeroplanes with unacceptable stall characteristics. e.g. pitch-up at stall or prone to entering the deep stall. As anything else related to aeroplanes, while solving some problems, they bring in some problems of their own (HTBJ, pg 131) so claiming they are stall recovery devices and suggesting they should be installed on any aeroplane to deal with the problem of distracted crew would be sparkling display of aeronautical ignorance.

Since for nine years I have been earning my daily bread flying the aeroplanes equipped with both stick shakers and stick pushers, implying if I ignored the stall warnings and somehow pulled them into stall they would bite without warning and once stalled would stand good chance to be unrecoverable, one might perchance find understandable that I view the propositions to indiscriminately train each & every airline pilot in full stall recovery procedure with considerable amusement.

Your "15" degrees PITCH UP I believe came from the DFDR, via ins and archive. You know the Pitch attained was not nearly that high, in the initial command post a/p loss.Yea... it was measly 13 degrees. Far too high for cruise anyway but compatible with the ardent desire to climb and having no idea aeroplane has insufficient performance to fulfill her masters wish - yet she attempted to obey into her eventual destruction.

727 2-engine out, manual reversion, NDB approach to NDB minimums was essentially a one maneuver check-ride.

What was most interesting, was not who succeeded or failed at the maneuver, but who would be enthusiastically willing to attempt it. Emphasis is mine but this is one of the most precise hitting the nail on the head that can be found on the PPRuNe.

Look, Sir, it is getting tiresome that you expect to make a glib comment about a failure of some piece of equipment and expect others to accept your pronouncement as 'end of discussion'.Maybe it's just me, but when someone counters to spectacularly wrong theory with some solid facts disproving it, least I expect it would mean the end of that particular direction of discussion.

he AP will not re-engage itself automatically in any scenario, and because Alt2 was triggered and latched in the case of AF447 even a manual attempt to re-engage AP would have been denied.Sorry Dozy, I missed the part where this was discussed. Could you provide the reference that states latching of ALT2 permanently disables the autopilot? I need to get my head around this.

[lomapaseo]

Lets not get too deep into the helpfulness of stick shakers.

There is some unique combinations at play in this accident

For starters its at high altitude and preceded by speed drop outs.

My feeling is that if only the stick shaker had annunciated, the crew would likely have addressed that bit somewhat better. But when multiple annunciations are alerted the tendancy of some might be to go to lowest common denominator in their memory bank ( and forget about the stick shaker or auto-something disconect)

I've seen this happen before

[jcjeant]

What scares me is for how little a span of time the airspeed was unreliable and how quickly this event went from routine to catastrophic. What saddens me is that perhaps in 99 time out of 100 this pilot would have correctly interpreted the situation and it would have become a none event.Indeed .. and the solution was simple ... and repeated by many here "Pitch and power"
What is needed for a auto control flight like in the Airbus to automatically go in a mode (one more law :) ) "pitch and power" in case of UAS ?
Can this be implemented ... for avoid the "1%" pilot failure to set the famous "pitch and power" ....

[bubbers44]

Stick shakers help because you immediately release the back pressure or decrease bank angle to stop it. I had it happen at night in a 727 over the water held high with speed brakes and a 30 degree bank circling to keep the pattern tight to lose altitude landing at POP in the Dominican Republic. The speed was fine but the bank and speed brakes set it off.

You instinctively fix the situation not ever experiencing it in an airplane, only the sim during training. It would definately override any oral warning.

[syseng68k]

jceant, #344


Indeed .. and the solution was simple ... and repeated by many here
"Pitch and power". What is needed for a auto control flight like in
the Airbus to automatically go in a mode (one more law ) "pitch and
power" in case of UAS ?. Can this be implemented ... for avoid the
"1%" pilot failure to set the famous "pitch and power" ....
This is really the common thread of what i've been thinking in terms
of a system that should be designed to degrade more gracefully at
the edges. When all the standard "protections" fail, there should be
absolute limits in command inputs that cannot be exceeded to ensure the
safety of the aircraft.

With so much technology built into these machines, it amazes me that there
are so many corners where the pilot can get himself into serious trouble,
for whatever reason. The acceptable limits under all conditions of flight
are known, so there's no technical reason why such last line of defense
protections shouldn't be built into the system design.

Perhaps they never thought it could never happen, but it does...

[mm43]

Clandestino;Could you provide the reference that states latching of ALT2 permanently disables the autopilot? It has been posted a number of times, but it was takata in AF447 - Thread No.5 (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-7.html#post6565899). I think A33Zab has also had something to say on the latching of ALT2B.

EDIT :: If you are looking for an AI definitive reference, then I have not been able to find it in FCOM or Instructor Training Manuals, so assume that it will be hidden somewhere in the AMM.

[HazelNuts39]

Now about stick pusher: it is not stall recovery device, it is stall prevention device!Maybe a bit semantic, but it is primarily a stall identification device. I fail to see the the distinction you make between recovery and prevention. On some airplane it is set to fire after the point of maximum lift (see fig. 5.25 in HTBJ) to provide the stall identification prescribed ("a nose-down pitch that cannot be readily arrested") with minimal loss of performance.

From HTBJ page 111 (my bold):
Hence, on aeroplanes capable of super-stalling, the 'stall' speed needs to be positively identified by a completely unmistakable, sharp, forward movement of the control column causing the aeroplane immediately to pitch down and reduce its incidence.And on page 131:
... the pusher is required to work only when the wing arrives at its 'stalling' incidence ...

[syseng68k]

If you want a stick pusher equivalent on airbus, just program it into
the software..

The more relevant question might be: Why hasn't this been done
already ?...

[Clandestino]

Thanks mm43, takata discussed the reasons for latching the alt law but I am looking for the confirmation of notion that has made circles around this thread lately: namely that latching of ALT2B disables the autopilot until ground reset. What logically follows is that since other crews normally used autopilot while remaining in ALT mode after regaining the normal airspeed display, they never got as far as ALT2B and AF447 was pretty unique. However, pretty old FCOM I have shows ADR disagreement doesn't result in AP being lost, so I'm looking for further reference.

Maybe a bit semantic

Maybe semantic but it looks to me like a scope issue.

If a stick pusher is used to meet the stall requirements it must provide two qualities: clear and unmistakable identification of the stall, by a sharp positive forward movement of a control column, and an adequate nose down pitch by the aircraft.

(...)

It is obvious that those constructors forced to use stick pusher, installations did so because they either found that their natural stall was quite unacceptable, or were not prepared to investigate the aeroplane's qualities beyond Max. Cl by other than a small margin, or decided that some part of their structure could not take the hammering in the violent buffet before the nose drop.

It follows form all these considerations, therefore, that that the stick pusher must always prevent the natural stall being reached in service.

[HazelNuts39]

It follows form all these considerations, therefore, that that the stick pusher must always prevent the natural stall being reached in service.I fail to see how that follows from the foregoing considerations, and it conflicts with what follows immediately next.

[Lyman]

Clandestino...

"Maybe it's just me, but when someone counters to spectacularly wrong theory with some solid facts disproving it, least I expect it would mean the end of that particular direction of discussion."

No solid facts were in evidence, merely a retort that a shaker had on occasion been ignored. Further, even BEA had trouble identifying Buffet and had to with accelerometer data from DFDR.

The dispensation you reference is what is galling. Do you honestly think the shaker would have been without possible benefit on 447?

The 330 in this case showed signs of Buffet only two seconds after the SW fired.

You are without doubt an expert, and I admire and respect your knowledge. Your personality is of no concern to me, I actually enjoy your posturing and preening. I expect that in a good pilot.

[syseng68k]

WRT "mixing" baro and inertial.
Regarding the concept of "mixing" baro and inertial (as posted above).

I would suggest, that such an idea, in a unreliable baro situation,
(which has caused the AP to disconnect in the first place), is,
stupidity personified.
You need to read what I said again, which was not suggesting that a
faulty source continues to be used, but that tracking the two sources
on a continuous basis provides a more accurate view of the overall
situation, a potentially earlier warning of developing problems and
fallback in the event of a single source failure. Perhaps i'm not very
good at decribing what i'm trying to get across ?.

If you have an ivsi on the panel, then you are already using baro /
inertial mixing, though not in a particularly complex way.


Why "contaminate" a supposedly "good" source of reliable data (inertial) with "known" or "suspect" baro data ?
All you end up with is a new layer of "uncertainty", on top of the one you already have, which you then have to troubleshoot.
Why make an uncertain situation even more uncertain and harder to troubleshoot ?
Such a situation is self defeating.
In a crisis, you need "crystal clear deliniation" of what is "good" from what is "suspect", or "bad".

The system should clearly "split" the two data sets by source.
Baro says "this", inertial says "that".
Separate functions, yes, but cross check between the two to improve
validity and consistency of data.


That can be done very simply.

Upon AP disconnect, the system should automatically, and instantly, modify the PFD to show all good inertial data, and remove the suspect data, as follows:
(a) remove FD bars if they were on, and
(b) put up the "inertial" FPV (bird) [with the inertial GS (not CAS or TAS or MN - they are baro) in the circle], and
(c) on the right of the bird - display the "actual" AOA, ("baro-ish" - but - we need it) and
(d) on the left of the bird - display the "target" AOA (for altitude, weight and speed from database - should be the same as the QRH - UAS tables).
(e) on the right - below the bird - display the "actual" N1's
(f) on the left - below the bird - display the "target" N1's (for altitude, weight and speed from database - should be the same as the QRH - UAS tables).
(g) in the left lower corner of the PFD - display a circular "traditional steam gauge" altimeter with a moving hand driven by inertial data, and
(h) in the right lower corner of the PFD - display a circular "traditional steam gauge" variometer with moving hand driven by inertial data.

PF should then just simply fly the bloody aeroplane.
That's high level detail and not really my area. No argument
about the last line though :-)...

[gums]

I have to go with PJ, TD and Cland on the crew procedures and following both untuitive actions and those in the "books". Still a mystery to me why the PF did what he did and why the PNF did not take a more pro-active role.

I only flew one jet with the pusher, and that sucker was a 28 pound forward force. If close to the "pitch-up", and handling the jet carefully, it literally took the stick outta your hand! Flew another with the rudder shaker and anybody that didn't think they were getting close to a stall by then was a sorry pilot.

So I don't think a pusher would have helped. But there's more.

The Cl versus AoA curve we see in many 'bus discussions is not accurate. The jet does not lose a lot of lift when the curve reaches the max. and more degrees AoA are required before the thing completely stops flying. Further, the jet seems to have very benign stall characteristics, so entry could be disguised by WX turbulence, mach buffet, spoiler deployment, etc. In short, lowering the nose with a bit of power seems to be a viable recovery technique ( assuming the crew realizes their predicament). No point on the pitch coefficient plot to show a "deep stall" such as we had in the Viper. The THS and elevators could have enabled recovery.

My last point on the pusher is what good is it if the FBW system ignores AoA?

Some really good points lately, and I am happy to have been given a seat at the table.

[mm43]

Clandestino;From A330/A340 FCTM 8.110.4 -
In a failure situation, various combinations of ADR faults may occur, each
interpreted differently by the PRIM and FE computers:


One ADR output is erroneous and the two remaining ADRs are correct. The PRIMs and the FEs reject the faulty ADR. On basic A333/A343 aircraft, there is no ECAM alert, however one PFD will display some incorrect parameters. On the A346 and enhanced A333 aircraft, if one ADR output is erroneous, and if this ADR is used to display the speed information on either PFD, a NAV IAS DISCREPANCY caution is triggered. In all cases, CAT3 DUAL will be displayed as an INOP SYS on the STATUS page.
Two ADR outputs are erroneous but different and the remaining ADR is correct, or if all three ADR outputs are erroneous but different. The AP and A/THR will disconnect. If the disagreement lasts for more than 10 seconds, the PRIM triggers the NAV ADR DISAGREE ECAM caution. Flight controls revert to ALTN 2 law. The SPD LIM flag is displayed on both PFDs, however VLS and VSW are not displayed. This condition is latched until a PRIM reset is performed on ground without any hydraulic pressure. However, if the disagreement was transient, the AP and A/THR can be re-engaged when the NAV ADR DISAGREE message has disappeared.
One ADR is correct but the other two ADRs provide the same erroneous output, or if all three ADRs provide consistent and erroneous data. The PRIMs and FEs will reject the “good” outlier ADR and will continue to operate normally using the two consistent but faulty ADRs.

The bolding is mine. The > 10 second disagreement is the trigger for ALTN 2, and it seems that the NAV ADR DISAGREE would remain for rest of the flight.

I know the quote is from A333, but I don't believe this is one of the minor differences between A332 and A333.

[PJ2]

mm43;
The > 10 second disagreement is the trigger for ALTN 2, and it seems that the NAV ADR DISAGREE would remain for rest of the flight.Yes, and for ALTN 1 as well. This change was made around 1997. Prior to this change, a momentary loss of valid air data would latch the EFCS in ALTN law for the balance of the flight. As far as I can determine, the only conditions which would cause the loss of AP 1 + 2 for the balance of the flight are the NAV ADR FAULT 1(2) + 2(3):

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


http://www.smugmug.com/photos/i-Z37FZHq/0/XL/i-Z37FZHq-XL.jpg

The only other possibility (only because it isn't clear if the AP is lost until landing) is the Abnormal Attitude Law, which if set pitch and/or bank angle values are exceeded, the laws revert to, in roll - yaw alternate, and in pitch - an adapted Nz law, without autotrim.

The autopilot will not engage without autotrim, (Use Manual Trim). After aircraft recovery, and until landing, the laws stay the same for roll but revert to Nz law with a recovered autotrim. I would expect the autopilot could be engaged depending upon other factors, (both elevators controllable, yaw damper functioning).

[Lyman]

@PJ2... "The only other possibility (only because it isn't clear if the AP is lost until landing) is the Abnormal Attitude Law, which if set pitch and/or bank angle values are exceeded, the laws revert to, in roll - yaw alternate, and in pitch - an adapted Nz law, without autotrim."

I probably sound impatient or worse... I have read here that AP is lost until ground maintenance. Are you saying it is not yet established? From the report, with the new addition of the Captain's comment re: "Wait, the autopilot.....(sound of selector switch, CAM)" which he spoke very late in the descent, we do not know if the a/p was merely left on, or if the PF or PNF selected it, do we?

If the a/p is locked out after AL, it is probably not important, but if the a/p was reselected, the AD definitely says that the autopilot can come back on line with rectified NAV ADR disagree? Of course this would interest the investigation....or it's discussion....

[mm43]

PJ2;Yes, and for ALTN 1 as well. This change was made around 1997. The FCTM is a CX one dated June 2005, and it seems strange that it made reference to the >10 sec ADR disagreement resulting in ALTN2 only.

The notable difference between ALTN1 and ALTN2 is the Roll Direct, and it is possible that the A/P cannot be re-engaged in that condition, i.e. PRIM requires a hydraulic reset on the ground. The RTLU can be reset with slat/flap extension below FL200.

Hopefully someone can identify exactly when and why the A/P re-engagement is inhibited.

EDIT :: My crib sheet has the following on Law reversions:-

Alternate 1:The pitch attitude (Theta) protection is lost. High speed and stall protection are alternate.
Alternate 1A:In addition the stall protection is lost.
Alternate 2:The pitch attitude is lost and high speed and stall protection are alternate. In addition the lateral normal law is lost and replaced by the lateral alternate law (roll direct and yaw alternate).
Alternate 2A:In addition stall protection is lost.
Alternate 2B:Pitch attitude, high speed, and stall protection are lost and the lateral normal law is replaced by lateral alternate law (bank angle protection lost).

[PJ2]

mm43;

Doh!...my expanded abnormals indicated the following:

NAV ADR DISAGREE
F/CTL ALTN LAW (PROT LOST)
Note: Following an ADR DISAGREE, detected by the PRIMs, ALTN law is latched. Resetting the PRIMs by using the pushbutton does not allow normal law recovery.

The latching only after 10 second was the feature introduced after 1997. I drew the conclusion from this and from another document which discussed the 1997 change, that both ALTN 1 and 2 latched. I've checked with my FCTMs as well and they agree with your comment that only ALTN 2 is latched. Thanks for the correction.

Interestingly, the following comment is offered in the CP FCTM:

Handling Characteristics

In pitch, handling remains similar to normal law.

In roll, depending on the failure level, control is either normal (ALTN 1) or direct (ALTN 2). In roll direct, the aircraft appears to be very sensitive and bank stability is no longer active.

[Clandestino]

Thanks mm43, seems that idea that AP was permanently lost stems from interpreting: 1. "This condition is latched until a PRIM reset is performed on ground without any hydraulic pressure." to be applicable to AP inhibit and not just to flight controls law 2. "the AP and A/THR can be re-engaged when the NAV ADR DISAGREE message has disappeared." to mean that AP is inhibited rather than "can" indicates it is possible yet inadvisable to engage the AP before ADR DISAGREE has cleared.

Unfortunately, comprehensive list of A330/40 UAS incidents, such as posted by Takata (http://www.pprune.org/tech-log/456874-af-447-thread-no-5-a-7.html#post6565899) is absent from final report. It is obvious that all of the incidents involved blockade of at least two pitot probes, so not much difference from AF447 there. 1.16.2 of the report further refers to automation behaviour. ALTN law mostly remained latched for the duration of the flight yet AP and ATHR were recovered, there were even cases of engaging the autopilot while UAS was underway and following the wrong but agreeing air data.

Gums, pusher and shaker are only really meant for the aeroplanes that don't have acceptable natural stalling tendencies. If you don't need pusher - you don't install it as there's always risk of untimely activation. To mitigate it, pusher must push positively but not with such a force that it cant be manually overridden. That's the difference between alpha protection and pusher - alpha prot can not be overridden, that's why it is designed to shut itself down when there is doubt about the integrity of the air data feeding it and that's what we, very technically, call "alternate law". Perhaps tihs is the reason why it is apparent to you that FBW ignored the AoA - it got ignored because FBW is based on unintelligent computers, it detected that there is discrepancy between AoA and speed but it cannot see the whole aeroplane energy picture and has no memory to remember what was the aeroplane doing for last couple of seconds to make a judgment what is right and what is false. The decision must be made by the system both possessing and properly using intelligence.

Regarding the "flying near the edge" and "absence of G trim", I have to return to the teleological discussion regarding the passenger transport aeroplanes. G trim is useful on fighters, to set it to 1 when cruising to decrease the workload and set it to zero while maneuvering to achieve prompt unload with stick neutral. For aeroplanes designed to spend most of their lifetime in straight and level flight, it would be completely superfluous. Flightpath stability makes much more sense. As for the edge:

In cruise at Mach 0.8, the margin between the flight angle of attack and the angle of
attack of the stall warning is of the order of 1.5 degrees, but the stall warning speed
displayed on the air speed tape (in alternate or direct law) will be around 40 kt below
the current speed.40 knots indicated for the aeroplane that makes only gentle heading corrections while cruising is actually quite enough.

No solid facts were in evidence, merely a retort that a shaker had on occasion been ignored. That a shaker had on occasion been ignored, which resulted in stall, loss of control and subsequent fatal injuries and damage to the property is a solid fact.

That a stall warning was heard and heeded in some cases of A330/340 UAS is a solid fact.

That there were A330/340 crews who believed that stall warning is false but they didn't pull, kept AoA under control and lived to tell the story is a solid fact.

[A33Zab]

Could you provide the reference that states latching of ALT2 permanently disables the autopilot?



AMM:

The AP can be engaged in EFCS normal or alternate control law, not in direct law.


If ALT is caused by double ADR FAIL the AP is not available (see PJ2 #356 (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-18.html#post7294685)) but after UAS the AP can be available.

One of the conditions to engage AP is CAS > VLS, For AF447 this means that after 02:10:46 (2 consistent and good airspeeds available) but CAS < VLS the AP could not have been reengaged.

In the 'air caraibes memo' AP2 could be reengaged after UAS while in ALT2x, although VLS was not displayed here, it must have been calculated by FMGEC and CAS>VLS.

[A33Zab]

Hopefully someone can identify exactly when and why the A/P re-engagement is inhibited.

http://i474.photobucket.com/albums/rr101/Zab999/A33APFDATHR_COND.jpg

[syseng68k]

A33ZAB

Turning that into english, both the AP and FD are inhibited unless at
least 2 IRU and 2 ADR are valid, amongst other things. If either pair
are invalid, engagement or reengagement of the AP would fail..

A/THR needs only the ADR condition valid of the above pair...

[A33Zab]

Agreed,

Invalid ADR is not equal to a failed ADR.

An ADR FAIL (announced by ECAM msg and local warning) is always an invalid ADR!
This ADR FAIL condition was not present in AF447.

To be exact:

AP needs AP/FD common conditions AND AP specific conditions AND AP operational conditions.
FD needs AP/FD common conditions only.

note:
Not completely clear in this - selfmade logic - is that [AP/FD & A/THR common conditions] are only required in managed modes.

[Lonewolf_50]

I will also question why some people on this thread are obsessed with a stick shaker. This aircraft had a system that could have safely restored level flight had it been re-engaged. So, instead of putting a stick shaker in, why not allow the system to take control again if it is convinced that the aircraft is in danger of exiting the envelope?
There is a system, meat based, that at no additional charge and with no further engineering complexity, flies the plane. Going further into automation dependence seems poor path to follow.

Turning that into english, both the AP and FD are inhibited unless at least 2 IRU and 2 ADR are valid, amongst other things. If either pair
are invalid, engagement or reengagement of the AP would fail..

A/THR needs only the ADR condition valid of the above pair...

As I read your translation: so long as the IRUs are up and operating, and the ADRs return to "valid" once the icing in the pitot tubes clear and airspeed input becomes reliable again, the A/P can be reset.

Did I get that right?

[OPENDOOR]

Just one question; what idiot designed a system where by max nose down input on the left stick was canceled by max nose up input on the right stick?

What possible situation could arise where this feature would have any benefit?

I'm referring to the inputs as AF447 went through 10,000 feet.

[Lonewolf_50]

Opendoor, I think I see a rationale behind summing / averaging the inputs by two SS: avoid potential over controlling (and possible damage) to the aircraft if the two pilots are both trying to make an input at the same time.

For example, if you have a 2.75 g limit, and the Ground Prox warning goes off, both pilots (even though one is flying at the time) may instinctively grab the stick and pull to the limit. If you allowed both inputs to add, then you have a 5.5 g pull. That may be a few g's more than needed, and potentially damaging, and might also induce an accelerated stall just when you cannot afford one. What needs to be done and trained to deal with the situation you cite is one pilot takes controls (I have the controls!) and the other pilot relenquished (you have the controls!) and ONE flies. It seems to me that the control logic is built to accomodate sound CRM principles.

Granted, not pulling enough could profoundly damage the aircraft via ground impact ... but I think the limit design tries to account for that.
(Aside: There was some very good and informed discussion of this in the Islamabad crash thread where they hit that mountain, over a year ago).

While the situation I cite may not be the best example, I think it illustrates the problem of two FBW inputs being used at once, inadvertently or not, without a filter to process two inputs when, ideally, the system is only ever supposed to have one man flying in the first place.

This follows good CRM practices, usually, except when you need one guy to save us all from the idiot trying to kill us in the other seat ... :eek:).

[OK465]

AP needs AP/FD common conditions AND AP specific conditions AND AP operational conditions.

A33Zab:

This is, as usual, very interesting. A check of the STATUS page at any given point during one of these various UAS scenario sequences might pin down exactly when the A/P becomes available again, if in fact it actually does.

I'm having a problem with understanding that an A/P pb will physically engage in 'latched' ALT2 when it wouldn't engage during the period of time that the condition precipitating the latching was in effect.

If you were able to get the A/P pb to engage in ALT2, what would the FMA displayed lateral steering mode be in roll direct? Same as roll alternate? Blank?

[Organfreak]

There's always room for improvement, whatever the make of the aircraft.

What about a "smarter" sidestick? Keep the averaging IF the sticks are going in the same direction; if they are going in conflicting directions, supress the non-priority input (null).

[Lyman]

"That a shaker had on occasion been ignored, which resulted in stall, loss of control and subsequent fatal injuries and damage to the property is a solid fact."

From Clandestino....

You supply evidence (anecdotal) that supports a partial story. Shall I waste our time and bandwidth by supplying reams of data that support the opposite side? That the stick shaker is a life saver, is trained in approach to Stall syllabi, and is found on your very own aircraft?

You fly a turboprop, a T tail, I assume. That is a complex platform, and in challenging conditions, I propose that your aircraft so equipped, is a safe one?

My comments were meant to gain information from others, not meant to be argumentative. I said that in the type of Stall 447 experienced, and flown by a confused pilot, that the outcome may have been better if the stick turned into a buzzing snake in her pilot's grip? At the moment when the a/c exited the envelope? Further, the rest of the way down, he held back stick. Would he have done so if the stick started to actually shake his hand numb? Also, wouldn't the other two have noticed the stick shaking? Could the Captain's side have been included in the warning state? For three minutes, would the PNF have allowed the PF to continue holding the mushed attitude? I say things would have been markedly better, and though you may claim, "one in a million", would that cause the families of 228 dead people to agree with you?

The 330's Stall was entered in extreme fashion, quickly, and without the nose drop and falsely advertised Buffet from Stall that the Airframer sold the regulator on when begging for what you describe as "dispensation" from Shaker install.

I am amazed that such a seasoned pro would continue to say that the shaker would have been of no use.

"I'm having a problem with understanding that an A/P pb will physically engage in 'latched' ALT2 when it wouldn't engage during the period of time that the condition precipitating the latching was in effect."

From OK465

My friend, so am I. At the very least, even if the a/p did not return, why did the Captain make his comment? Also, if the a/p is latched out, common sense would indicate the logic would remove the selector from annunciating "ON". In a critical cockpit, let's agree that cleaning up all extraneous (and possibly dangerous) info would be a mind set for the designers of the panel.

[DL-EDI]

what idiot designed a system where by max nose down input on the left stick was canceled by max nose up input on the right stick?

What would you suggest should happen when one pilot pushes and the other pulls? How would the systems know which input to follow? What happens when one pilot pushes a conventional yoke while the other pulls?

Ignoramus that I am, my understanding is that on yoke-equipped aircraft resistance to their attempts would trigger recognition of a conflict and they'd either agree who has control or continue to counter the other's input, with the stronger pilot "winning". On an Airbus the trigger would be aural and visual warnings with the respective arm strengths not being a factor.

In either case, wouldn't continued wrestling with the the controls suggest a bigger issue than how the logic works?

[Lyman]

"In either case, wouldn't continued wrestling with the the controls suggest a bigger issue than how the logic works?"

Yes, an issue that would be readily known by both pilots, in yoke equipped a/c.
Rather than unknown, and problematic, with SS's? This is the fundamental problem with SS, as interpreted in Airbus a/c, that both pilots can happily input commands, that are followed by the a/c, without knowing the other's actions..... Schizophrenegenic.

The corollary for SS would be that they are connected directly, such that each pilot would know what the commands are, and that they in fact emanate from his/her oppo. One stick could not move independently of its second/other. This is immediate and non verbal, which is currently non existent in the platform.

What's he/she doing?

Opendoor, I think I see a rationale behind summing / averaging the inputs by two SS: avoid potential over controlling (and possible damage) to the aircraft if the two pilots are both trying to make an input at the same time. LW50.

A rationale? Made necessary by something that should be impossible in the first place: Dual Control? A third and synthetic solution to a problem created out of mistakes made by two disconnected pilots? It is a palliative, made necessary by shortcomings of the design in the first place? Airbus makes a serious mistake in the very creation of the problem: they dilute and make a nonsense of what for a century has been critical to safe flight, in the interest of doing something merely different. that something? COMMAND. One pilot at a time. In making the pilots role secondary, they have fallen too far into the trap set by their own automation, to wit: an airplane cannot fly two ways at once. Offering a summed and synthetic solution to a confusion is not dangerous? I say it can be, and 447 demonstrates that one confused pilot can frustrate the mere possibility of salvation by two others in pursuing the path Airbus set: two separate control stations, with a computer that tries to resolve both inputs, when one is decidedly wrong.

A correct result cannot come from a computer that bases its own solution on two others, one of which is false.

[DL-EDI]

Rather than unknown, and problematic, with SS's?


In spite of the aural and visual "Dual Input" warnings?

both pilots can happily input commands, that are followed by the a/c


On a yoke-equipped aircraft with one pilot pushing and the other pulling, which input does the a/c follow?

[1066]

If LHS PNF was convinced that he needed control all he needed to do was push SS forward while at the same time pressing and holding the take over button on the SS and saying, "I have control". If RHS PF does not respond in time honoured aviation fashion, "You have control", PNF keeps the TO button pressed.

If I remember correctly all the time the to button is pressed you have control and after 30secs holding it pressed the opposite SS is latched out.

Correct CRM, I have/You have, allows takeover without the need to lose the other SS as the taking over pilot can release the TO button before 30secs has elapsed.

Press and hold, until release is acknowledged, is taught for capts taking over in the event of a botched landing from the other seat!

[DL-EDI]

Correct CRM, I have/You have, allows takeover without the need to lose the
other SS as the taking over pilot can release the TO button before 30secs has
elapsed.

In a co-operative handover, does a Priority button even need to be pressed? E.g. FO flying, Captain puts his hand on the stick, calls "I have control" or "my aircraft" or whatever, FO releases his stick.

[Lyman]

On a yoke-equipped aircraft with one pilot pushing and the other pulling, which input does the a/c follow?

Hi DL-EDI....

Which input? There is only one, the columns act as one. The efforts of two pilots result in one command only. They are mechanically connected.


"If LHS PNF was convinced that he needed control all he needed to do was push SS forward while at the same time pressing and holding the take over button on the SS and saying, "I have control". If RHS PF does not respond in time honoured aviation fashion, "You have control", PNF keeps the TO button pressed."

Hi 1066....You presume that the system will be followed, when it has built in traps that depend on CRM. With or without CRM, a yoke equipped a/c cannot split command, mechanically, it cannot happen, and is independent of the sanity or skill of either pilot.

[DL-EDI]

Which input? There is only one, the columns act as one. The efforts of two
pilots result in one command only. They are mechanically connected.


Well, that was kind of my point. :)

So what's the difference between that situation and the Airbus method of producing one command only, apart from not giving preference to the pilot with the stronger arms?

[hetfield]

So what's the difference between that situation and the Airbus method of producing one command onlyThe "Airbus method" is not of one command only, like most of us know.

If you mean just the algebraic summation it is true, but the critical point are subtle inputs from either side, without knowing of the other pilot. And this happens day by day.

[Lyman]

Howdy...

It is perhaps easier to consider that the two systems are offering two ways to input command. Both have two stations, one has split input engineered into it. In an arse about look, consider that the yokes are made smaller and put on either side of each pilot. That is architecture alone. Now, consider the yokes can be manipulated differently, with simultaneous and differing command, but to a computer?

In making everything computer dependent, Airbus has missed something, the need for Bulletproff CRM. The possibility exists that command is in some cases made murky by a design, which should never be the case?

Split input engineered into it? Why yes, else "summed solution" would not exist. Can one say the split input is an artifact of poor design? Without question. For that to be considered wrong, one would have to say split input was inadvertent. I think the designers might take offense....

[DL-EDI]

Now, consider the yokes can be manipulated differently, with simultaneous and
differing command, but to a computer?

Airbus scenario - One pilot pushes his stick to 100% nose-down while the other pilot pulls his stick to 100% nose-up.

Boeing scenario - One pilot tries to push the yoke to 100% nose-down while the other tries to pull the yoke to 100% nose-up.

Assuming both Boeing pilots have the same strength, wouldn't the net result in both cases be zero pitch input? Isn't it the case that neither system is deliberately designed to allow two pilots to engage in a prolonged fight for control?

The possibility exists that command is in some cases made murky by a design,
which should never be the case?

I'm no aviation expert but, based on my IT experience, I'm not sure that algebraically summing two inputs is a particuarly challenging task for computers. :)

[bubbers44]

When flight path stabilized use the UAS checklist using pitch and thrust.

Level at FL350 seems pretty stabilized to me. The pitch up and climb power were meant for terrain clearance not for high altitude autopilot and airspeed loss. We can't help AF447 but maybe this investigation will help some other pilot that loses airspeed and autopilot in high level flight to not make the same mistake.

[bubbers44]

DL, that is what the palm of your hand is for. To smack the FO so he lets go of the wheel. Now you have control. Works every time.

[kwateow]

In the Boeing FBW planes (777, 787) where the yokes are not mechanically connected to the control surfaces, is there a take-over button to resolve the conflict?

[Clandestino]

I'm having a problem with understanding that an A/P pb will physically engage in 'latched' ALT2 when it wouldn't engage during the period of time that the condition precipitating the latching was in effect.

Seems that FCS gives up restoring itself back to normal law after it detects long lasting ADR disagreement, however AFCS keeps checking indefinitely and will restore itself as soon as two ADCs agree, not necessarily at correct value. Page 86 of the report refers.

If you were able to get the A/P pb to engage in ALT2, what would the FMA displayed lateral steering mode be in roll direct? Same as roll alternate? Blank? Probably NAV, HDG or TRK. Airbus AFCS is just an AFCS, only special thing about it is output; it doesn't go to autopilot servos but to FCCs. I suppose it doesn't care if its roll commands are obeyed by moving the spoilers and ailerons with constant roll rate or constant deflection. I suspect that AP doesn't work in direct law is because FBW has no control over pitch trim in it.

There's always room for improvement, whatever the make of the aircraft.Yup, but they don't come about just because someone has wished for them and they never come without a price.

That the stick shaker is a life saverSo are a parachute and a helmet but you won't see me wearing those when flying passengers.

is trained in approach to Stall syllabiOn the aeroplanes equipped with it!

and is found on your very own aircraftBecause during certification, her natural stall characteristics were found wanting so they had to be supplemented by the artificial means!

You fly a turboprop, a T tail, I assume. That is a complex platform, and in challenging conditions, I propose that your aircraft so equipped, is a safe one?Safe aeroplane with totally unsafe natural stall characteristics. How about that?

the outcome may have been better if the stick turned into a buzzing snake in her pilot's grip?

BEA actually performed the study to determine what it felt like as the AF447 approached the stall:

Airbus subsequently flew special flights to collect more accurate data at high angles
of attack and with an aircraft configuration close to that of the accident (mass, flight
level, Mach, etc.). These tests made it possible to refine the preliminary correlations
and to establish that the level of buffet was considered to be a deterrent by the test
pilots when the angle of attack was about 10°, corresponding to normal acceleration
amplitude of 1 g at the pilot’s seat. This angle of attack was reached at about 2 h 10
min 57 s during the accident flight.What are the chances that the pilots that ignored 1G amplitude shake as the sign of impending stall would pay attention to "buzzing snake"? I hope this lays the notion of stick shaker being useful on A330 to rest.

The 330's Stall was entered in extreme fashion, quickly, and without the nose drop and falsely advertised Buffet from Stall that the Airframer sold the regulator on when begging for what you describe as "dispensation" from Shaker install.See previous entry.

I am amazed that such a seasoned pro would continue to say that the shaker would have been of no use.With a little help from the red warning at the bottom of this page, your posts amaze me no more.

In either case, wouldn't continued wrestling with the the controls suggest a bigger issue than how the logic works? Depends on controls architecture. On some aeroplanes you may end up with split controls and each side flying just one elevator, completely independently of the other. Sounds fun, eh?

In a co-operative handover, does a Priority button even need to be pressed?No.

a yoke equipped a/c cannot split command, mechanically, it cannot happen, and is independent of the sanity or skill of either pilot.It can split. It can happen. It is not independent, especially in the wrestling over controls cases. Priority button is very neat way of taking the control away from the captain Gonenuts.

I'm no aviation expert but, based on my IT experience, I'm not sure that algebraically summing two inputs is a particuarly challenging task for computers.That's just what they do but it is very, very wrong way to fly an Airbus. Only one pilot can fly her at the time, be it left, right or auto, this feat is just there to ease the hairy control handovers, before PiC clearly designates who will fly.

[DL-EDI]

bubbers44:

DL, that is what the palm of your hand is for. To smack the FO so he lets go of the wheel.

Though in either type, that might favour a married FO, with a large wedding ring on his/her inboard hand... at least until they're back in the office... and it would only happen once. :)

kwateow:

In the Boeing FBW planes (777, 787) is there a take-over button to resolve the conflict?

They have inter-connected yokes.

Clandestino:

Thank you - I didn't think transferring control was as complicated as some think (no-one in particular).

That's just what they do but it is very, very wrong way to fly an Airbus. Only one pilot can fly her at the time, be it left, right or auto, this feat is just there to ease the hairy control handovers, before PiC clearly designates who will fly.

Indeed but some seem to think there's something dangerous about the Airbus dual-input logic when, functionally, it's not that different. As I said, if you get continued conflicting dual-input then you've got bigger issues to worry about.

[A33Zab]

I'm having a problem with understanding that an A/P pb will physically engage in 'latched' ALT2 when it wouldn't engage during the period of time that the condition precipitating the latching was in effect.


AP was disconnected due to (dual) ADR loss, AS gains could not be established.
Once the (dual) AS returnes, the gains can be established again.

The AP has it own gains, rate- and amplitude limitations build in, it don't need the NORMAL LAW or whatever remaining protections in ALTERNATE.

AP commands a separate pitch deflection order for elevator (DQ) and THS(DQT) to FCPC in control.
For roll command there is a separate roll order(P) for ailerons and spoilers.
Yaw control command is separated in (Ytrim) and (Ystab).
All are deflection! orders.

If you were able to get the A/P pb to engage in ALT2, what would the FMA displayed lateral steering mode be in roll direct? Same as roll alternate? Blank?

After 02:10:46 it would return in HDG or TRACK because that are the only SELECTED lateral modes available.
AFAIK with current HDG or TRACK as default.

[OK465]

A33Zab: Thank you, sir.

Should the STATUS page eventually reflect availability of the A/P (by exclusion) even though ALT2 initially latched with AP 1+2 displayed as INOP on the STATUS page?

Is the displayed A/P STATUS and availability updated automatically or does it have to be cleared?

(edit: thanks clandestino also, and is roll direct an FCSC function in this case? additional edit: It occurred to me that doesn't really matter if the commands are deflection orders. Thanks again.)

[bubbers44]

DL, you have to survive so fighting control over the aircraft is not an option. The PIC normally takes control in a conflict because he is in command. Sometimes the FO has to take control if the PIC is going to kill everybody. I only had to do this once as an FO on a 4 engine corporate jet and forced a go around.

I assumed I was fired but the chief pilot thanked me for saving a totally botched approach on a short wet runway. We were too high to not have an overrun so I went max power and went around on his leg.

[mm43]

A33Zab re Post #362 (http://www.pprune.org/tech-log/489774-af-447-thread-no-9-a-19.html#post7295037)

Many thanks for the logic schematic which certainly is an improvement over that described in FCOM / FCTMs.

With the logic shown, the conditions for A/P engagement are clear, and I assume that the A/P Auto OFF conditions, i.e.if abs(φ) >45°,
or θ <-13°, or θ >+25°,
or CAS < VLS,
or CAS >(VMO/MMO or VLE/VFE)
will take precedence once the A/P has been engaged?

[A33Zab]

Should the STATUS page eventually reflect availability of the A/P (by exclusion) even though ALT2 initially latched with AP 1+2 displayed as INOP on the STATUS page?

Is the displayed A/P STATUS and availability updated automatically or does it have to be cleared?


As a general rule ECAM messages and INOP status are cleared automatically when the fault or inop conditions are not active anymore.

(edit: thanks clandestino also, and is roll direct an FCSC function in this case?)

If you allow me,

No, roll direct is part of ALTERNATE (ALT2x) control of the FCPC.

FCSC ALTERNATE YAW/DIRECT control becomes active if all 3 FCPCs failed to control in DIRECT.
To set that in perspective:

Priority:
1 = FCPC #1 in NORMAL
2 = FCPC #2 in NORMAL
3 = FCPC #3 in NORMAL
4 = FCPC #1 in ALTERNATE (active @ AF447)
--
7 = FCPC #1 in DIRECT
--
10 = FCSC(#1 & #2) ALTERNATE YAW/DIRECT

[bubbers44]

Do pilots follow unknown FD commands and if so for what reason? Isn't the checklist saying 5 degrees nose up and climb power until at a stabilized altitude which they were at at FL350 and use UAS and thrust charts to continue. Seems they were already stabilized.

[A33Zab]

Correct, there are small deviations in the values to engage and the values to automatically disengage.

Yours are indeed the disengage values.

to use your format:


AP Engage is inhibited:

if abs(φ) >40°,
or θ <-10°, or θ >+22°,
or CAS < VLS,
or CAS >(VMO/MMO or VLE/VFE)

[DozyWannabe]

Which input? There is only one, the columns act as one. The efforts of two pilots result in one command only. They are mechanically connected.

Not exactly true on advanced airliners - remember the EgyptAir 990 case highlighted an unforeseen problem with the 767's interconnection, namely that when one pilot pushed and the other pulled, the result was split elevators and immediate departure from controlled flight.

[Machinbird]

....when one pilot pushed and the other pulled, the result was split elevators and immediate departure from controlled flight.
Is that strictly correct? Seems to me that shutting off the engine master switches followed by loss of electric power had a lot to do with the loss of control. (Which way is up?)

Be careful about half truths.:=

[roulishollandais]

In my view, the ball is in the regulator's court

Lyman,
You often evocate law problems. You are right. But they are hard law in aeronautics, and near nothing in the young science of automation.

In my interpretation, some Court have to say what "hand flying" means for the airline, as everything is still secret, or proprietary knowing (to verify!), as no Justice enquiry has been done.

That situation started with the Habsheim case : the lawiers, judges, experts, did never spoke about the definition of automation, responsibility of the engineers who hide important information to the Captain of the flight. They just do not know what it is !

The law (Code de l'Aviation Civile for instance, enforced by the Chicago convention, their annexes, and a lot of Court decisions) give all the rights to the Captain. Compared law exist, and is important, between Captain of an Aircraft, and Captain of a Ship : nearly the same.

The french Code l'Aviation Civile protects the Captain in the independance
of his decisions in flight.

The french Code pénal (criminal code) protects everybody against blackmail, when the airline intimidates the Captain. But HE HAS TO SAY "NO" !:=

[DozyWannabe]

Is that strictly correct?

Sorry I can't find a better source more quickly than Wikipedia, but here:

EgyptAir Flight 990 - Wikipedia, the free encyclopedia (http://en.wikipedia.org/wiki/EgyptAir_Flight_990)

The flight data recorder reflected that the elevators then moved into a split condition, with the left elevator up and the right elevator down; a condition which is expected to result when the two control columns are subjected to at least 50 lbs of opposing force.[1] At this point, both engines were shut down by moving the start levers from run to cutoff.

It looks like the split condition happened at around the same time the engines were shut off.

Admittedly the departure from controlled flight as a result of the split condition is conjecture to some extent, but given the authority the elevators have it's got to result in a serious upset very quickly.

At any rate, the point I was trying to make was that in modern airliners, yokes aren't simply attached to a big metal bar like they were in the days of yore, they are complex electro-mechanical devices that can behave in unexpected ways when put into unusual configurations.

[mm43]

EgyptAir 990 - NTSB Report (http://www.ntsb.gov/doclib/reports/2002/AAB0201.pdf)

[kwateow]

"That situation started with the Habsheim case".

You probably have a lot of automation in your car, but the manufacturer doesn't explain in detail how it works.

It remains your responsibility to not to drive it negligently into the trees, killing your passengers. Something which Capt "Rambo" Ass-line never understood.

[DozyWannabe]

That situation started with the Habsheim case : the lawiers, judges, experts, did never spoke about the definition of automation, responsibility of the engineers who hide important information to the Captain of the flight. They just do not know what it is !

This isn't about Habsheim - which is a 24-year-old case!

The engineers "hid" nothing from the Captain - he simply didn't appreciate the consequences of the actions he performed when trying to rescue a botched approach rather than go round and try again.

As I said before - by trying to make it about pilots vs. automation his lawyers actually made things more difficult for him in terms of the criminal proceedings - the report basically threw the book at Air France for poor procedure and implied that the mistakes made by the captain were understandable, but by making a media circus out of it his legal team made him more of a target.

Sadly what it's also done is propagate a lot of misunderstanding about the case - and some of those misunderstandings are still repeated by the media today.

[Machinbird]

Admittedly the departure from controlled flight as a result of the split condition is conjecture to some extent, but given the authority the elevators have it's got to result in a serious upset very quickly.That is a lot of conjecture on your part. Split elevators are going to result in an average of the two pitching moments and a roll moment. Since the elevators are very close to the aircraft's roll axis, any roll moment generated by the split elevators can be countered by the ailerons and spoilers which are much further away from the roll axis and therefore have a much greater moment arm, which is conjecture also, but results from the application of simple physics.:}

The core problem on Egyptair 990 had to be the active sabotage of the flight.

[Flyinheavy]

@bubbers
Isn't the checklist saying 5 degrees nose up and climb power until at a stabilized altitude which they were at at FL350 and use UAS and thrust charts to continue.If only they would have identified UAS and started the procedure.

BEA speculates about, that PF might have thought, he was in an "overspeed situation".

Wasn't he trying to extend spoilers? Who would extend spoilers in any other situation than overspeed?

[DozyWannabe]

Since the elevators are very close to the aircraft's roll axis, any roll moment generated by the split elevators can be countered by the ailerons and spoilers which are much further away from the roll axis and therefore have a much greater moment arm, which is conjecture also, but results from the application of simple physics.:}

I have no doubt that a pilot briefed on the behaviour should be able to counter it, as you say. I still wouldn't rate the chances of countering that if such behaviour was not widely known.

In any case, we're digressing here - the point is that modern yoke designs are more complex than Lyman suggested.

[bubbers44]

I guess if he did the 5 degrees nose up with climb power he would let the higher altitude static port because of the lower static pressure but blocked pitot tube cause an overspeed warning. Then he increased attitude to around 15 degrees when the overspeed warning happened.

This happened in the dominican with a taped over pitot tube on a 757.

[DozyWannabe]

@bubbers44:

There was no overspeed warning - nor did the aircraft approach an overspeed condition at any point.

The PF queries whether the PNF and Captain suspect "crazy speed" (which we're assured by our Francophone colleagues means he was concerned about overspeed), but the PNF at least seems convinced this is not the case and rebukes the PF for trying to extend the speedbrakes.

It has been suggested that the PF may have suspected overspeed due to abnormal wind noise (possibly due to stalled air).

[FYI : The Birgenair 757 crash you refer to was suspected to have initiated from an insect nest inside the pitot tube - the "taped over" incident was the Aeroperu 757, and in that case it was the static ports. ]

[bubbers44]

Probably not but why would a pilot pull up 15 degrees unless something startled him into doing it. You can't do that at FL350. The scenario I told is the only one that made sense, trapped pitot pressure and a climb with real static pressure would give an overspeed. None were heard on the CVR that I know of but why did he pull up into an impossible climb?

[DozyWannabe]

@bubbers44:

...why did he pull up into an impossible climb?

I suspect that question has a lot to do with why there are nine threads on this incident!

Unfortunately the only man who can provide a definitive answer is dead, and so the report suggests several potential reasons. The one that makes the most sense to me is a sustained startle response of the type that afflicted Captain Renslow of ColganAir 4805.

[Flyinheavy]

@Dozy

rebukes the PF for trying to extend the speedbrakes.
According Interim 3 CVR transcript:

2:12:04 to 2:12:07 "The airbrakes are controlled and deployed" and PF comments "I have the impression that we have some crazy speed..."

That has occurred at about FL300 descending. What else than thinking of overspeed makes a pilot deploy airbrakes?

[Lyman]

@Dozy...

"It has been suggested that the PF may have suspected overspeed due to abnormal wind noise (possibly due to stalled air)."

1. Suspect nothin'...the spoilers were deployed, see the traces of the devices. There is no record that I could find that however they stowed, they all stowed completely. That is the genesis of my guess that the chronic right roll, yaw was damage related...

2. You have not considered the wind shear as the source of the Belief in crazy speed? There could easily have been an apparent accel/decel due to this type of turbulence, and changing air mass/noise...

Erm..... Thanks Flyinheavy, great minds think alike...

@Dozy... I think their respective TT and TiT are very similar, and I concur re: Renslow, Bonin. Good catch.

@Dozy...PNF: "do not extend....etc." So yes, the PNF was assertive, here, and if I might, I'll use this bark to introduce a possible problem.. To now, I have been reliant only on what I read in PPRuNe and the officials to found my remarks. Recently, I have ventured off the reservation, and have read some interesting discussion re: CVR content. The BEA have heavily witheld crew remarks if they are profane. They euphemistically use the Catchall: "not related to flight". I think there might be some interesting rhetoric in the CVR that is witheld due it's colorful nature. There is also so much to understand from volume and tone, notwithstanding profanity, that I'll bet you a kidney the CVR has much more to tell us than what we are given...

[DozyWannabe]

@FlyinHeavy:

The speedbrakes are only partially deployed, as the PNF immediately selects them back in.

The PF may have suspected overspeed, but the point is that the suspicion was incorrect. There was never an overspeed warning because the aircraft was never in an overspeed state.

@Lyman:

The roll problem is an artifact of stall, nothing more. The indicated spoiler positions after the attempt to deploy correlate precisely with the sidestick roll inputs made by the PF, and there was no obvious sign of damage to the spoilers on the wreckage found. Is it that hard to accept that - besides the pitot tubes - the aircraft behaved normally? The report does not damn the crew, and outside of scuttlebutt neither does anyone else. Why this quixotic crusade to prove a mechanical failure?

Re: CVR - while the BEA sought to spare unnecessary detail, that book published earlier this year claimed to have more of the unexpurgated content - in fact I'm pretty sure it used all of it, while leaving some of the more relevant stuff out. I'd be very surprised if there is any more useful information that we don't already know about.

[Lyman]

Recheck your spoiler response....What the pilot considered, created their collective reality. That you do not understand this is what keeps us miles apart.

What the CVR has in the way of usefulness is lost on you when you use it only to qualify a mechanical log... It is the human version of the DFDR.

I can't discard your take on the CVR contents, but it is half full.... Their is more to spoiler operation than roll, and drag, likewise deficiencies in position sensing that you do not consider. Position of spoilers can be correctly displayed without the spoiler being attached to the actuator. For example only, not a statement of support for any theory...

[Flyinheavy]

@Dozy

There is no doubt about that there had been nor a warning neither real overspeed. Sadly enough did this crew not realize what WAS their situation.

I found it remarkably though that BEA cared to mention it as a POSSIBLE reason for the otherwise very strange maintaining the SS in nose up.

Sorry to post again, but just as a reminder:

2.1.3.3.1 PF’s reactions

On the other hand,
in the absence of airspeed information known to be reliable, it is possible that the
PF thought that the aeroplane was in an overspeed situation, notably due to his
interpretations of several clues:

ˆ The aerodynamic noise,
ˆ The buffeting, that he might have interpreted as being due to high speed,
ˆ The speed trend arrow on the PFD, which at that time indicated acceleration.

He reformulated his impression
a*few seconds later, combined with an attempt to extend the speedbrakes.
Other factors which may have prompted the PF to fear an overspeed situation were:
ˆ The display on the ECAM (max speed 330/.82) combined with the reconfiguration
to alternate law which may have been read;
ˆ The fact that, in cruise, the upper red strip on the speed tape (MMO) is about ten
knots above the current speed, whereas VLS is barely visible at the bottom of the
tape (thirty knots less);
ˆ The dangers associated with overspeed situations embedded in the collective
consciousness of pilots.



May I add, that I did also exams for ATPL in France and I do recall that they were putting a lot of emphasis to the problem of overspeed in Aerodynamics. Much more than FAA or some other European ATP exams would. So I would understand a French pilot thinking of this getting into a subjectively high stress situation.

[Lyman]

Dozy. you continue to misuse the report. Again, what the PF was thinking and doing, you reject because it does not fit what happened.

That is absurd, when you consider that what he thought and did created what happened, otherwise known as 'what happened'....

Flyinheavy....by "Possibly" do you refer to its misuse, when it is quite clear the PF was convinced enough to select speed brakes? Is there a doubt?

[DozyWannabe]

I found it remarkably though that BEA cared to mention it as a POSSIBLE reason for the otherwise very strange maintaining the SS in nose up.

It's not that remarkable really - as I said, because there is no way to be definitively certain about why the PF handled the aircraft the way he did, the BEA are therefore compelled to examine all potential reasons.

Recheck your spoiler response....What the pilot considered, created their collective reality. That you do not understand this is what keeps us miles apart.

The point is that they were supposed to act as a crew, and what we instead see is a significant difference in perception between the two FOs. From the start of the sequence, the PF seems completely out of his depth and it looks very much like he was throwing possible conclusions out there -almost at random - to see if anything would stick. The PNF on the other hand seems to be trying to work from the evidence in front of him, and gets increasingly frustrated with his colleague.

What the CVR has in the way of usefulness is lost on you when you use it only to qualify a mechanical log... It is the human version of the DFDR.

You're levelling assertions at me that don't fit my actions. If you recall, I was one of the first to point out the PNF's growing sense of uncertainty and irritation with the PF - I've used the CVR transcript for far more than qualification of the DFDR!

Position of spoilers can be correctly displayed without the spoiler being attached to the actuator.

I'm not so sure of that. I'm pretty sure that a "position" trace requires confirmation from the systems that the position was actually achieved.

Dozy. you continue to misuse the report. Again, what the PF was thinking and doing, you reject because it does not fit what happened.

That is absurd, when you consider that what he thought and did created what happened, otherwise known as 'what happened'....


I'm not "rejecting" anything, and I'm certainly not "misusing" the report. The evidence suggests a sequence of incorrect diagnoses by the PF, and that's all there is to it.

Without wanting to sound harsh, you've attempted to advance theory after theory for over a year, and every time the evidence has disproved those theories (which have included vertical stabiliser separation, THS jackscrew failure and structural failure of the spoilers among others), you come back with another one.

Now it seems you're trying to argue that the PF's assertions were actually correct and it is the data gathered that is somehow wrong. What makes this incredibly unlikely as far as I'm concerned is that on the CVR, you can hear the PNF in the opposite seat repeatedly making assertions and suggestions which *do* fit the data and which in all likelihood would probably have helped. If the PNF had even the slightest belief that the PF had a point, then you'd have heard co-operation between them. Instead, we hear the PNF openly wonder where the Captain is, while at the same time trying to get the PF to snap out of it and approach the problem logically.

[gums]

Salute!

Good grief, Doze, how ya gonna get an overspeed warning if the air data system is FUBAR?

So maybe the junior crewmember up front was more worried about overspeed than stall or something else. And I have a problem with the senior guy in the other seat not "suggesting" something early in the UAS.

The simple fact is that we here shall never know until we meet those dudes in that neat hootch bar in the sky and get their side of the story.

That's what Gums says this nice evening in the high country...

[DozyWannabe]

@gums:

The speeds had in fact been back online for almost a minute prior to the "crazy speed" comment. Just before the comment was made, the air data was again fouled, this time by stalled air.

The reason I can't fathom why he'd think "overspeed" is that the aircraft had been descending increasingly rapidly with the nose consistently pitched above neutral for 45 seconds prior to the comment - this behaviour is completely inconsistent with overspeed.

[bubbers44]

I think we are coming back to the experience level of the two pilots.

[DozyWannabe]

@bubbers44:

Experience is certainly a factor, but there are other more complex issues involved.

The PNF didn't actually have a great deal more hours under his belt than the PF, but it seems apparent that he had a better handle on the situation at first. Regardless of experience, some people handle pressure and abnormal situations better than others - and the initial difference in approach between the two FOs seems to highlight this.

What's more disturbing is the complete lack of CRM throughout the sequence and the fact that upon his arrival, the Captain got bogged down in a reactive mode rather than taking charge and pooling all the information as to what happened before his arrival.

[jcjeant]

Hi,

DW:
The PNF didn't actually have a great deal more hours under his belt than the PF, but
Just five times more ....

1.5.1.2 Co-pilot in left seat (Robert)
Male, aged 37
ˆ Medical certificate (class 1) issued 11 December 2008, valid until 3
2009 with compulsory wearing of corrective lenses.
ˆ Experience:
y total: 6,547 flying hours
y on type: 4,479 flying hours
y in the previous six months: 204 hours, 9 landings, 11 take-offs
y in the previous three months: 99 hours, 6 landings, 5 take-offs
y in the previous thirty days: 39 hours, 2 landings, 2 take-offs


1.5.1.3 Copilot in right seat (Bonin)
Male, aged 32
ˆ Medical certificate (class 1) issued on 24 October 2008, valid until 31 Oc
2009 with compulsory wearing of corrective lenses.
ˆ Experience:
y total: 2,936 flying hours
y on type: 807 flying hours
y in the previous six months: 368 hours, 16 landings, 18 take-offs
y in the previous three months: 191 hours, 7 landings, 8 take-offs
y in the previous thirty days: 61 hours, 1 landing, 2 take-offs

[DozyWannabe]

More like 2x if you take total hours into account - we're not talking a major gradient here.

[Machinbird]

The reason I can't fathom why he'd think "overspeed" is that the aircraft had been descending increasingly rapidly with the nose consistently pitched above neutral for 45 seconds prior to the comment - this behaviour is completely inconsistent with overspeed.
Maybe PF though his PFD was lying to him.
In any case, it is tragic that the lack of deceleration when he briefly deployed the speedbrakes didn't start someone thinking. Instead the lightning bolts sparking between the PM and PF by then washed away the ability to form that type of question.

Incidentally, has anyone considered the short period that PM was awake as a potential reason for his lack of assertiveness. Perhaps he just didn't trust himself yet?:hmm:

[Organfreak]

Dozy,
There's no such thing as "stalled air." (Near the pitots.) Only a stalled wing.

This has come up before.

[DL-EDI]

At any rate, the point I was trying to make was that in modern airliners, yokes aren't simply attached to a big metal bar like they were in the days of yore, they are complex electro-mechanical devices that can behave in unexpected ways when put into unusual configurations.

:ok: And I should clarify that my point was only that the Airbus dual-input logic makes sense when one thinks about it and probably wasn't designed by "idiots".

[chrisN]

As to why the PM/PNF was not more assertive; after he told the PF to be more gentle with SS movements while PF was “stirring mayonnaise” (and PF had taken back control when PNF had started to correct the nose up condition), PNF concentrated on calling back the CDB. It seemed to me that the way CDB had handed control to PF before he left the cockpit may have implied that PF was not only PF but acting PIC too.

This would explain (not justify, but explain) both why PF felt he could seize control back from PNF, and why PNF then gave up trying to override PF and instead wanted the CDB back to assert his authority.

Admitted speculation, but it fits who did what.

(I tried to find the CVR transcript again but can’t – but I did read some of it that reached the public, which had that implication as i read it.)

[Lyman]

@DL-EDI...

"And I should clarify that my point was only that the Airbus dual-input logic makes sense when one thinks about it and probably wasn't designed by "idiots"."

Howdy. Yes, the solution is elegant. My point went to the actual need for a solution in the first place. In creating a system that facilitates inadvertent dual input, the solution becomes mandatory. The argument against dual yoke seemed to be based on physical confrontation, a separate issue. At no time did I imply that The Airbus system was vulnerable to battling pilots. On the contrary, the danger is in the subtlety of the SS, and it's other shortcomings, visibility being one, and I'll add lack of shaker warn to that. BEA have demonstrated that in Alternate Law, the Airbus is mostly vanilla, but untested in STALL, so the basis for a stick (shaker) waiver is found to be awarded in error.

Clandestino has posited, in my opinion, that a shaker is not needed, simply because it is not fitted ...

The CVR has been removed from the report, at least in my efforts, I cannot find it. I was trying to locate the new to the discussion remark made by CDB DuBois to the effect that the selector had remained in "ON". That is my conclusion, or that he had attempted to select it "ON" for some reason. The CVR remark was not clear, only that the sound of a selector being cycled was picked up by the Cockpit Area Microphone....

[infrequentflyer789]

The CVR has been removed from the report, at least in my efforts, I cannot find it.

Do you mean the transcript ? English is at http://www.bea.aero/docspa/2009/f-cp090601.en/pdf/annexe.01.en.pdf

I haven't seen actual audio file, anywhere.

[Lyman]

Thanks, that is working

2:13:53. From Captain. "(so wait) AP OFF". Sound of selector.....

Whether or not the a/p was engaged, apparently, the selector was ON. Seems a poor result that may upset or interrupt, or lengthen, the attempt to recover flight path.

If the crew rejected STALL from the very first chirp, the campaign against it for the rest of the descent makes sense, the WARNING was actively ignored. IS there no CB to eliminate the perceived distraction? Why carry on listening to something deemed an enemy of recovery?

Is there a linked circuit that shows a conflict in the a/p channel? Because as important as the system is, it would seem imperative to extinguish a false
display...is this in the report?

Not one mention of the STALL WARN by anyone of the three? Challenges credulity.

Jcjeant, you follow the trial? Has anyone formally challenged the BEA to supply the full CVR, with audio? Seems an obvious course of action, the part released to the public challenges common sense, not to mention airmanship...

[jcjeant]

Jcjeant, you follow the trial? Has anyone formally challenged the BEA to supply the full CVR, with audio? I will follow the trial .. the best I can if I stay alive :) as it's expected in many years to come ..
It's a possibility that one partie or the judge itself ask the full CVR recording (I think the judicial experts have already acces to the full FDR listing .. but the public not yet )
Regarding the full CVR (not a partial transcript) I know a case where the court (canadian) asked for have it with succes ( judicial battle about what was exactly with ATC).. and it's in the Toronto AF A340 accident .. IMHO

[DL-EDI]

The argument against dual yoke seemed to be based on physical confrontation

The points I made were to counter this:

what idiot designed a system where by max nose down input on the left stick was canceled by max nose up input on the right stick?

My avoidance of a general comparison of the pros and cons of Airbus side-sticks v. yokes was no accident. :)

[Turbine D]

@ Lyman,

Quote by Lyman: On the contrary, the danger is in the subtlety of the SS, and it's other shortcomings, visibility being one, and I'll add lack of shaker warn to that. BEA have demonstrated that in Alternate Law, the Airbus is mostly vanilla, but untested in STALL, so the basis for a stick (shaker) waiver is found to be awarded in error.

Clandestino has posited, in my opinion, that a shaker is not needed, simply because it is not fitted ...

So in the instance of AF447, would a stick shaker be of help at 350K, M 0.8 with the A/P & A/T disengaging shortly followed by a stall warning? Isn't the key here what was recorded on the CVR, "We have no speeds"? If you have no speeds and you have been flying normally, wouldn't that be interpreted as UAS? Wouldn't you then apply the Unreliable Speed Indication/ADR Checklist? So then, you would level the wings and apply 5º pitch and get out the pitch and power tables? Now would a stick shaker shaking help or hurt you accomplishing this as very gentle adjustments of the sidestick are required? Where would the stick shaker get it's information from that wouldn't be erroneous? Would this extra layer of "protection" add to the confusion having not reacted in the correct manner? Wouldn't the designers, engineers and test pilots of the aircraft thoroughly thought through the need for a stick shaker and implications it might present, both positive and negative and concluded the negatives outweighed the positives?

And finally, would the pilots who have or do regularly fly Airbus aircraft, such as Clandestino, be clamoring for sidestick shakers if it were of true benefit? Just asking....

[slats11]

I just looked at the CVR transcript for the first time in a while.

What do people think of the sudden smell of ozone, and the sudden change in perceived cockpit temperature (noted by both crew, and sufficient that PF asks PNF if he did something to the A/C).

It seems odd that in an 11 hour flight, this should occur only a minute before presumed pitot freezing

I am sure this has been discussed previously, but I can't find any reference to it.

Thanks in advance.

[DozyWannabe]

@slats11:

I think people said a while back that it was consistent with transiting the weather they encountered.

EDIT : Yes.

Ozone smell probably came from the Cb overshoot they were flying near. I believe the top of the Cb was estimated by Meteo France as 52000 feet, and by Vasquez as 56000 feet. Ozone is present in significant amounts near the tropopause and the Cb overshoot reached into the ITCZ tropopause by 6,000 feet according to Vasquez.

The PNF seems to have recognized what it was.

there is no electronics failure that will fill an aircraft cockpit with ozone. Ozone production requires voltages that are not present. When they stink electronics failures are very distinctly not ozone smells. Phenolic (not used anymore) has a distinctive smell when it burns. Various wire insulation materials have their own distinctive smells. Burned transformer varnish and insulation has yet another smell. Burned carbon composition resistor (not used anymore) is yet another smell. Burned metal film resistors have too little smell to worry about. Burned epoxy fiberglass circuit boards are burned epoxy smell. (Don't ask. It was after three months of 60-70 hour work weeks.) The blue smoke from integrated circuits has little or no smell because it's generally magical and in small quantities. (No, you cannot stuff that blue smoke back inside, either.) When an electrolytic capacitor overheats and dies the odor is "impressive"; but, it is not ozone. A modern cockpit has few if any motors present spinning at high currents and high voltages.

[Lyman]

In my reply at the time, I suggested that Ozone accompanies heated wiring, and electrical fire. It did not play well, but there were artifacts that made a human caused Ozone release possible, the ACARS "WRG" data, and the immediate recovery of the avionics bay in the first moments of seabad acquisition possibilities. Were the recovery team eager to catch the avionics bay and sequester it with special care? Yes, I have smelled the remnants of Lighning strike, and electric motor under great load, the smell is unmistakable.

Listen, we are in an area that can confuse, and I want to call Dozy's attention to it. Both in JD-ee's post, and many of Dozy's, there is this attitude that what someone senses or believes is wrong because they do not understand the data involved. The PF asked about a smell, it was PNF who offered St Elmo, or whatever. It is disturbing that some people believe an explanation that doesn't click with them perforce means that the experience did not happen....or should not continue to be challenged...

The pilot smelled something, else he would not have asked. The explanation given by PNF may have been accurate, it may have been WRONG. We are supposed to be chastened and drop the topic because some one can explain OZONE? What if it was wires burning, or shorting? What if the AP selector was in the circuit that caused this smell? How does supplying an astute answer to anything necessarily answer correctly the question asked? It does not. I would rather keep asking questions if appropriate, and I reserve the right to call any explanation into question. For the record, I believe Lightning was determined not to be in the area.

[DozyWannabe]

Lyman,

JD-EE's comment was in fact addressed directly to you in the original post. I elected to summarise rather than potentially cause discord, but just so we don't get sidetracked, let's have the rest of it.

And, yes, in more than 60 years playing with electronics and electricity I've smelled all those smells above, some under rather dramatic conditions. (Wet slug tantalum capacitors don't stink much at all. They just embed themselves in ceilings. They're not used anymore.)

[to Lyman/bearfoil :] Your fancy is getting too many flights of late. Maybe you should have it take a vacation. It's not in the competition for frequent traveler miles. I know people who could run rings around your imagination.

I repeat : JD-EE is an electrical and electronic engineer of 60 years' standing. I think she knows what she's talking about.

[EDIT : Good catch!]

[infrequentflyer789]

I repeat : JD-EE is an electrical and electronic engineer of 60 years' standing. I think he knows what he's talking about.

^^^ " he's "

Umm...

[not sure JD-EE is still around to correct, but see e.g. http://www.pprune.org/tech-log/449639-af-447-search-resume-part2-48.html#post6437226] ] :)

[Lyman]

The PNF may have been absolutely wrong. The PF sensed an odor he did not recognize. Having an answer to a question is not sufficient to close the topic if it may have been wrong. JD-EE was not present, thankfully. PF was, and his question got an answer.

You are easy to please, if it matches your goal. I suggest that more common by far are electrical faults, overheated defrosters, motor spark, and hot wiring, than a smell an experienced pilot cannot identify, and wants input from his partner....

Have electrical problems been eliminated by anyone other than you? Not by BEA.

[slats11]

I'm pretty inclined to accept whatever JD-EE (female) says about electrical matters and the production of ozone. However I suspect many of us will not be able to reliably distinguish the smell of ozone from the smell of an electrical fault/short. A common misconception is that the this "electrical smell" is a result of ozone production. So did the pilots really smell ozone, or did they smell an electrical problem that they (incorrectly) ascribed to ozone? What may be easily distinctive to JD-EE may not be to many of us.

The timing seems suspicious, and I would not be inclined to dismiss an electrical fault just because this fault should not have produced ozone. It might have produced something that the pilots believed was ozone.

At the same time that both pilots suddenly perceived that the cockpit had suddenly become uncomfortably warm. A sudden updraft of warmer air from below, which was sufficiently rapid to temporarily "overwhelm" the ability of the climate control system to compensate? Maybe. Or maybe something else.

[Organfreak]

Somehow, I missed JD-EE's post on electrical smells.

As a long-time Hammond Organ fixer (over 40 years), I can tell you that the so-called "electronic smell" is often the smell of:
a) burning/melting plastic (often insulation)
and/or
b) over-heated transformer components, such as wax, oil, and the like.

Ozone itself is a different smell. Lyman's speculation can never be verified as truth or not. We weren't there; we can't smell it. But it walks like a dog, barks like a dog, etc. etc.

OTOH, burning plastic is generally extremely toxic, so now we can add fuel to the fires of speculation: PF was maybe poisoned by toxic fumes(???). :ugh:

Off to search for JD-EE's post.

[DozyWannabe]

@Lyman, slats11,

The lack of secondary evidence in terms of items recovered, no cascading series of failures consistent with arcing or fire and no reference to unusual smells, temperature changes (or, indeed, smoke) after the initial query leans heavily towards discounting the possibility, does it not?

@Organfreak - you can click the little arrow next to JD-EE's name in my initial quote above and it will take you directly to her post.

[Organfreak]

Yes indeedy, DW, and thanks for that. A post from last year; who knew?

And, I meant to include this photo in order to bolster my own credentials: :hmm:

http://www.organfreak.com/images/contpanel.jpg

;) (I 'spose this will be removed)

[slats11]

Perhaps Dozy. However so much of this still doesn't quite make sense. I am certainly not insisting there was a electrical fault. But I am wondering if it is possible.

I just find the timing odd. Confusion about whether PNF had adjusted the A/C. An ozone smell. A significant rise in cockpit temperature. And then a minute later UAS and autopilot drops out.

Yes the explanation could be an updraft of warmer air associated with Cb. This could have produced an ozone smell in the cockpit, and may conceivably have resulted in a transient rise in cockpit temperature. No comment about an updraft or turbulence at that time however.

2 h 08 min 27 It’s me who just changed to max eh Any idea what PNF is saying here? Radar??

2 h 08 min 44 it’s ozone that’s it we’re alright Was PF worried about something at that time?

[DozyWannabe]

Perhaps Dozy. However so much of this still doesn't quite make sense.

What in particular is bothering you? I've been hanging around these threads so long I could probably dig up some stuff to help.

[Turbine D]

I am not sure I would put much weight on an electrical fire situation, on board the aircraft that is. But outside, think St. Elmo's Fire. A quote from a B757 FO flying from LAX to ATL in high clouds:
As soon as we got into the clouds, St. Elmo’s fire was blasting off the nose of the airplane, the ozone smell was intense.

[roulishollandais]

@Organfreak
The organ of my church is a traditional organ, but for some months "they" did important work of "renovation" (no need !). The air is blowed with an electrical engine, but they connected the whole to... the speakers already connected on an electronic organ...

the organist found something sounded wrong wenn he played the great organ : his nightmares and earmares are finished : the engine burned last week doing much damage in the church...:E

Nice cockpit !

[Lyman]

I think the problem warranted a look see at the logs of GZCP. Look for squawks, fixes, and any repetitive maintenance. I'll just go find it in the report.


Sure.

[DozyWannabe]

And since when has any accident report contained maintenance logs for the aircraft when there was no obvious maintenance problem relevant to the accident?

Back when we started this merry dance you expressed a desire to make sure the crew were not held solely responsible for the accident if there was any doubt. The crew have not been held solely responsible. What, ultimately, are you trying to achieve now?

[Lyman]

If you think the logs were not gone over with a magnifying glass, you would be mistaken. Are you always satisfied with what is obvious? You do not consider that which may be hidden?

I am not and may never be comfortable with the finding's accuracy.The conclusion is beyond belief. It stretches the imagination that it could be true.

[DozyWannabe]

Lyman, you're confusing the BEA going over the records (which I'm sure they did) with said records' inclusion in the report (which in all likelihood was unnecessary).

What is it about the conclusion that you find so hard to believe? It fits aspects of several previous accidents and known HF problems. Most pilots aren't supermen and even the best are as prone to bad days in the office as anyone. Combine this with organisational entropy on the part of their employer and the chances of something serious happening increase exponentially.

Contrary to the beliefs of some, the BEA have never hidden anything or covered for Airbus, and I'll cheerfully debate anyone who disagrees.

[rudderrudderrat]

Hi Lyman,
The conclusion is beyond belief. It stretches the imagination that it could be true.
It makes perfect sense.
All the holes in the Gruyère cheese simply lined up that night.

At time 2.10.03 the flight deck loud speaker warns of autopilot disconnect, and is heard and acknowledged.
From time 2.10.09.6 the Altitude Alert deviation warning "C Chord" sounds and continues to sound until impact.

It is only interrupted by "Stall Stall", ECAM "dings", crickets, "Priority Left / Right", "Dual Input" etc.

No one on the flight deck mentions hearing anything. No one thought to cancel the "C chord".
The only device attempting to warn them that were stalled was lost amongst the cacophony of other aural warnings.

On previous aircraft, we had both the vibrator noise (unmistakeable) and the tactile feel through the control column.
Why was something similar not thought to be necessary?

[jcjeant]

From the final report:
It would also seem unlikely that the PNF could have determined the PF’s flight path
stabilisation targets. It is worth noting that the inputs applied to a sidestick by one
pilot cannot be observed easily by the other one and that the conditions of a night
flight in IMC make it more difficult to monitor aeroplane attitudes (pitch attitude
in particular). In addition, a short time after the autopilot disconnection, the PF’s
statement that he had the controls and his reaction to the initial deviations observed
(in particular in roll) may have led the PNF to change his action priorities. Identification
of the failure appeared to become a priority over control and flight path monitoring.
Consequently, he was unaware of the climb.
Control of the flight path does not correspond to what is expected. The amplitude
of the actions may doubtless be explained by the highly charged emotional factors
generated by the unexpected autopilot disconnection in the context of the flight.From the CVR:
2 h 10 min 30,0 Stabilise
2 h 10 min 30,7 yeah
2 h 10 min 31,2 Go back down
2 h 10 min 32,2
According to that
we’re going up

2 h 10 min 33,7
According to all
three you’re going
up so go back down

2 h 10 min 35,2 okay
2 h 10 min 35,8 You’re at…
2 h 10 min 36,4 Go back down
2 h 10 min 36,7
It’s going we’re
going (back) down

2 h 10 min 38,5 gently
2 h 10 min 39,3
I’ll put you in in A T
T (*)… So .. the PNF made remarks (give orders) to the PF to go back down and the PF give a positive verbal answer
Anyways .. the PNF can't see if the PF make good actions on the stick ...
How he can be sure that his orders are really followed by PF actions ?
By checking the instrumentations ?
Maybe by looking at the instruments and seeing that these would not show what he expected of them (because his order to the PF" back down" and the positive answer by PF) he began to believe that the instruments were no longer reliable
That can be a additional trouble for the PNF ... and alter momentarily is judgement of the situation ..

[Lonewolf_50]

jc, just to let you know:

When I used to teach instruments, and I gave a flight student a correction, I rarely if ever "rode" the controls, unless the student was badly over controlling.

What I did do, however -- and I suspect that the PNF something similar -- was that after I gave a corrective input to the flight student, I watched the flight instruments to see if he put the correction in or not.

In the fleet, I took that same approach when I was a C/P flying with a pilot who was having trouble while flying instruments. I'd make an oral input and watch the instruments to see if he complied with my suggested correction. A number of my copilots did the same for me, and one talked me out of a slight case of the leans.

(Granted, at night near a the deck of a ship, however, I did tend to guard the controls when the other pilot was flying just in case my call for "power" went unheeded, in which case I'd make the input).

Put another way, I'd say that your line on "watching" the controls may not fit with the primary concern that pilots focus on to see if their suggested correction is acted upon or not.

He migh guard the controls, or ride them. Depends.

[DozyWannabe]

PNF doesn't make any reference to his instruments (other than speed) being out. Remember it was the instruments on his side being recorded, and the report makes no mention of instrument failure. Also, his rising alarm regarding the Captain's return could suggest that he could see exactly what the aircraft was doing and didn't like it one bit.

[Lonewolf_50]

Dozy, that does not relieve a copilot from staying in the problem until the Captain returns.

But it does speak to a problem with "cockpit gradient" that we have only a little to work with.

[jcjeant]

PNF doesn't make any reference to his instruments (other than speed) being out. Remember it was the instruments on his side being recorded, and the report makes no mention of instrument failure. Also, his rising alarm regarding the Captain's return could suggest that he could see exactly what the aircraft was doing and didn't like it one bit. To be simple:
You are PNF in an C172
You see (instruments) that with no doubts the aircraft is climbing
You ask the PF to stop climbing or more you ask him to go down
The PF answer you "yes ok i go down"
Again you check the instruments .. and see that the plane continue to climb .. and of course as nothing indicate an instrument failure .. you become concerned
For the demonstration only (as you can check your own yoke :) ) .. you check the PF yoke and see he pull the yoke in his stomach ...
In the A330 ...
It was already an instrument failure (unlike in the C172) ... it was a positive answer of PF (like in the C172) ... and when you check again instrumentation .. the instruments show the aircraft continue climbing
You check your stick ?
You check the stick of PF ?
You put handcuffs on the PF ?

[Clandestino]

Clandestino has posited, in my opinion, that a shaker is not needed, simply because it is not fitted ...Either we are looking at another dazzling display of inability to understand what was written or strong tendency to falsify other folk's posts. Shaker is not installed on aeroplanes that have natural pre-stall shake. BEA did flight tests with A330 with similar weight and C.G. as AF447. While they didn't push it all the way to stall...

Airbus subsequently flew special flights to collect more accurate data at high angles
of attack and with an aircraft configuration close to that of the accident (mass, flight
level, Mach, etc.). These tests made it possible to refine the preliminary correlations
and to establish that the level of buffet was considered to be a deterrent by the test
pilots when the angle of attack was about 10°, corresponding to normal acceleration
amplitude of 1 g at the pilot’s seat. This angle of attack was reached at about 2 h 10
min 57 s during the accident flight.

Repeat after me: shakers are devices fitted to aeroplanes with natural pre-stall buffet too weak to comply with certifying regulations.

Why was something similar not thought to be necessary? See previous entry.

Good grief, Doze, how ya gonna get an overspeed warning if the air data system is FUBAR?Good grief, Gums, where would the energy for overspeed come if you are at practical ceiling and pulling up like mad?

So maybe the junior crewmember up front was more worried about overspeed than stall or something else.Maybe, but if he was, he was dead wrong and consequently just dead.

Whether or not the a/p was engaged, apparently, the selector was ON. It was not. Read the report, please. AP was off and by the time descent started it was blocked off by ADR rejection due too to low forward airspeed. Capt was unable to grasp the situation so he thought it would be good idea to press the non-function AP button, without explaining it, either for the benefit of co-pilots or CVR.

very gentle adjustments of the sidestick are required? Bravo sierra perpetuated on PPRuNe. Read the report. Page 87. Slamming the stick from full back to full forward in ALT won't kill or even hurt you, if the average of pitch gyrations is centered on cruise pitch.

And finally, would the pilots who have or do regularly fly Airbus aircraft, such as Clandestino, be clamoring for sidestick shakers if it were of true benefit?Who said I regularly fly Airbus? I was just a line jock, warming the RHS of 319/20 for a bit less than two years. Who gives a rat's stern about me? It is all in the certification standards!

The timing seems suspicious, and I would not be inclined to dismiss an electrical fault just because this fault should not have produced ozone. It might have produced something that the pilots believed was ozone.Every fault recorded on DFDR came from just two sources: 1) blockade of pitots in cruise 2) stall. No fault that could be consequence of shortcut or fire was detected. Of course, there is also a dissenting opinion on Egyptair 990 that claims there are faults that go completely unrecorded on FDRs yet render the aeroplane uncontrollable in seconds. We must examine every option, must we?

Yes the explanation could be an updraft of warmer air associated with Cb.That would leave massive trace on Nz. Read the report.

[mm43]

I'm a bit late into the ozone discussion, but you're going to get my dimes worth anyway.

St. Elmo's fire and Ozone smell can be found from sea level and upwards when the conditions are right. On ships passing through tropical zones, St. Elmo's fire is often seen attaching itself to a yardarm of a mast, or even the outer corner of a bridge wing. The Ozone smell comes with the event.

Having had a lot to do with Ozone generators in a former life, I do know the smell of Ozone, and the linkage of St. Elmo's fire to that of the Ozone smell is also one I know well.

The PNF had crossed the ITCZ many times and was well aware of what he saw and smelled, and any conjecture that the smell was of electrical origin is just that - conjecture.

[rudderrudderrat]

@ Clandestino
Repeat after me: shakers are devices fitted to aeroplanes with natural pre-stall buffet too weak to comply with certifying regulations.
Then why do all Boeings & L1011s etc. have stick shakers, despite having natural pre-stall buffets?
Belt & Braces perhaps?

[Clandestino]

Beats me. Where did you get the reference about Anyboeing and 1011 having natural pre-stall buffet? Now we know 330 has it and 1g amplitude at cockpit is not what anyone would call "light buzz".

Anyway, what would have happened to flight controls of the aeroplane with synthetic pitch feel that suddenly got fed with low speed signals in cruise?

[rudderrudderrat]

Where did you get the reference about Anyboeing and 1011 having natural pre-stall buffet?
On every conversion course in the simulator. "Cobble stone" turbulence can feel similar.
Anyway, what would have happened to flight controls of the aeroplane with synthetic pitch feel that suddenly got fed with low speed signals in cruise?
The controls would feel lighter than normal - just like roll in ALT LAW

[Lyman]

Buffet was not noted on CVR. Buffet was determined by analyzing accel. The aC did not pitch nose down at Stall.

The pilots were not privy to recorded data on flight recorders. The Shaker vibrates the stick with no net effect on Pitch. Most installs include a very loud and disconcerting clatter, there is virtually no chance to miss the warning, though of course a possibility exists that it will be ignored or misunderstood. Marvin Renslow proved an exception.

I think any agreement on these points may be impossible, except to agree to disagree.

End of shaker discussion pour moi.

[gums]

@ Cland..... my comment to Doze was a "barb" about the almost perfect flight control laws and reversion sequences, especially WRT to stall warning/avoidance. And with respect to energy required to overspeed at the limits of the envelope, I stand my ground. With even a "limit" of "x" gees above gee=one, kinetic energy is enough to do exactly what the dweeb did - pull and pull to the limits and run outta energy while transitting the stall protection limits, then get to new territory. pushing forward would have equally bad outcomes if the "overspeed" "protections" ( how I hate that term) are FUBAR due to invalid speed inputs to HAL.

Thanks, Wolf, for the IFR training comments. I followed the same procedure for many years when dual, and when in a chase plane for the single-seaters I watched and talked a lot on the inter-flight radio. In the Viper, we were in a back seat and the control stick did not move or reflect what Joebaggodunuts was doing up front. So watch the gauges and feel the jet, then take over if things are going to hell.

Back to Cland..... From the CVR fidelity ( could detect switch changes) and the comments by the troops, doesn't sound as if the AB330 has pronounced buffet in the stall regime. On the other hand, the older designs many of us flew from the 60's and on had distinct pre-stall indications. In my case, we had vastly larger margins from stall-onset to actual stall, as well as immensely larger speed margins before reaching VNe.

An example presented was to have a shaker or pusher when the jet had no clear pre-stall buffet or warning. So I flew the VooDoo, which fit the description when supersonic. But sub-sonic, the thing shook and wobbled and such that only a hamburger would have pulled harder. You could also feel "stick lightening" ( also feel it supersonic, but no buffet). I will bet a hundred bucks I could fly with you in a pre-AB330 heavy and show you the buffet or buzz indicating an approach to a stall.

I read the CVR again, and the experienced pilot is telling the other guy to stop climbing and to be "gentle". After a minute of fruitless talk, he calls for the aircraft commander. All the while the stall warning doofer is going off. I never wished to fly a "crewed jet", and what we saw in AF447 confirmed my fears. " I got it, no, you got it........" Least in the Viper we could completely cut out the student's stick very easily.

Thanks to JC for reviewing the CVR comments for first minute or so.

[slats11]

And the abruptly increased temperature in the cockpit?

There are still some details that appear to be without explanation.

It is easy to overread or under read a CVR transcript. Human behavior psychologists believe that 10% of communication is the words themselves, 30% is the tone and the way the words are said, and up to 60% is nonverbal cues. I expect the exact words used account for > 10% when considering technical and procedural matters. On the other hand, we don't have a complete transcript (for understandable reasons) and so we may be missing some information which would help put things into context.

Why did the Captain not get a useful handover when he returned to the cockpit? Had things already degenerated that much. He got garbled bits if information plus lots of warnings and alarms plus a feeling that things were not right ( abnormal pitch attitude). It would have been perplexing to understand what had gone wrong in the brief interval since he had left the cockpit.

[Turbine D]

@ Clandestino,

Quote:
Originally Posted by Turbine D
very gentle adjustments of the sidestick are required?
Originally posted by Clandestino: Bravo sierra perpetuated on PPRuNe. Read the report. Page 87. Slamming the stick from full back to full forward in ALT won't kill or even hurt you, if the average of pitch gyrations is centered on cruise pitch.

The reference you mentioned is the TAM incident. What I referred to in the BEA Final Report was in Appendix 6, Page 1.
Airbus "Unreliable Speed Indication" Procedure, A330 Air France FCOM:
During this failure identification time, since the flight control laws may be affected, it is recommended to maneuver the aircraft with care until the ADR (s) is (are) switched off.
Guess the TAM folks proved the Air France FCOM wrong?

Quote:
Originally Posted by Turbine D
And finally, would the pilots who have or do regularly fly Airbus aircraft, such as Clandestino, be clamoring for sidestick shakers if it were of true benefit?

Originally posted by Clandestino: Who said I regularly fly Airbus? I was just a line jock, warming the RHS of 319/20 for a bit less than two years. Who gives a rat's stern about me? It is all in the certification standards!

I am sorry Sir, that I gave you credit for something that didn't deserve credit. I was just going by your previous information (Bio) that very recently changed including your location...

[Ian W]

dCLbydalpha

The airworthiness authorities basically demand it. In reference to the example, how many combined GPS/Inertial sensors are certified by a civil air authority for navigation?


There is a lot of work in this area - and QANTAS and Honeywell are in the lead on it: See this ICAO document one of many - https://docs.google.com/viewer?url=http%3A%2F%2Fwww.icao.int%2Fenvironmental-protection%2FDocuments%2FPublications%2F6104_en.pdf

[OK465]

I never wished to fly a "crewed jet"...

I never saw a jet I didn't want to fly. :)

[Lyman]

from BEA: "Control of the flight path does not correspond to what is expected. The amplitude of the actions may doubtless be explained by the highly charged emotional factors generated by the unexpected autopilot disconnection in the context of the flight."

Sounds a lot like some folks here.... Conclusion, doubtless correct, no need for explanation or analysis.. "Trust us, this is a government opinion."

Eliminated are ham handed tendencies persist, despite busts on sim, rote obedience to Stall Warn on TO, palsy, or bad curry from flight kitchen.

On the other hand, maybe it is a quote from one of Dozy's posts... There is a familiar ring to the rhetoric...

[Rockhound]

What possible significance is the temperature in the cockpit?
Why was there not a proper handover to the captain when he returned to the cockpit?
When he entered, he asked "What are you doing?" The PNF (in the LHS), the much more experienced of the two copilots, responded: "What's happening? I don't know...I don't know what's happening". The captain didn't even resume his place in the LHS where he could assume control, he got into the jump seat behind the console. Ten seconds later, six stall warnings sounded in the space of four seconds. No reaction from any of the three pilots. Seventeen seconds on, at FL250+, the PNF asks: "What do you think? What should we do?". The captain replies, "I don't know. It's going down". He's been on the flight deck a full minute, during which time neither of the two copilots has been able to explain what's been happening, yet he makes no effort to assume control.
In his book Erreurs de Pilotage 5, Otelli points out that STALL was verbally annunciated 75 times, taking up a total time of 54 seconds; the stall itself lasted 4 minutes and 24 seconds.

[Lyman]

Obviously it has no significance whatever, it is not covered in the "analysis".

On the other hand, evidence of absence is not absence of evidence.

"why should anyone give a rip?" is your question rhetorical, rock hound?

What are the odds the report is a fiction?

[slats11]

Rockhound, I have absolutely no idea what the significance of the cockpit temperature is. I am asking a question, not posing an explanation. Likewise I don't know what the PNF turned to maximum just before. He denied he had touched the A/C, so maybe the radar range (they were discussing a possible deviation to the left at the time).

All I am saying is that it may possibly be of significance. Out of the blue. In the middle of an 11 hour flight. Just one minute before other problems quickly unfold.

Obviously the PNF can't explain what he can't understand. But I would like to think he could have given the Captain a reasonably coherent account of the events that had transpired.

The Captain seemed very slow to act. Given he had only left the cockpit 11 minutes earlier, it is unlikely he had been asleep and was suffering from sleep inertia. So why?

Well in fairness, what was he expected to make of the following?

What’s happening? I don’t know I don’t know what’s happening
We’re losing control of the aeroplane there
We lost all control of the aeroplane we don’t understand anything we’ve tried everything

A quick explanation that the autopilot dropped out and they climbed and then entered a stall may have been sufficient to give the Captain the required situational awareness.

Although we don't have the audio, it is likely that PF and PNF were somewhat agitated (or more) when the Captain returned. Lack of clear handover. And then confusion, lack of assertiveness, and likely increased agitation.

[mm43]

slats11;A quick explanation that the autopilot dropped out and they climbed and then entered a stall may have been sufficient to give the Captain the required situational awareness.That's the problem, they didn't know they were "stalled".

You're right though, a quick briefing by the PNF may have helped, but on the other-hand he probably thought the PF would do it. :sad:

[bubbers44]

They were pitched up 15 degrees at FL350 and when the stall warning went off they didn't know they were in a stall? Sorry I guess we have covered this many times before. Unbelievable.

[slats11]

Ok. You are correct. I really meant that a coherent explanation from the PNF ( who seemed to have the better SA) that the AP had dropped out and they had climbed together with the Captain noting the pitch up attitude followed by the stall warning ...... Surely this would have been enough to make sense.

[mm43]

Nothing coherent (crew wise) happened in that cockpit from the A/P disconnect through to the end. It would seem that the BEA's Human Resources Group were not able to format a reasonable explanation for this behaviour either.

[rudderrudderrat]

Hi Rockhound,
What possible significance is the temperature in the cockpit?
It's a clue that you've just entered a region of much warmer air suddenly.
If the outside air temperature has risen faster than the hot air trim valves can respond, then you may have just entered the warm rising air of a big CB.
Best recheck the OAT for possible engine anti icing.

The two copilots were maxed out when the Captain returned to the flight deck. I don't understand why he didn't ask for the Altitude Alert deviation warning ("C chord") to be silenced so he could think straight. It was constantly filling in all the gaps between the other aural warnings until impact.

[Clandestino]

The controls would feel lighter than normal - just like roll in ALT LAW Thereby making it easier for the pilot bent on pulling to overstress or stall the aeroplane? Isn't it unsafe design? Unlike airbus where you are presented with constant stick force?

Of course I'm indulging in mockery here; both constant force sidestick and syntethic feel yokes are well thought-out systems with good and bad sides. Pilots who use them must be well acquainted with their normal and abnormal behaviour. PPRuNers would do well to remember that "natural feeling" yokes are in reality dependent on whole lot of instrumentation and electronics to simulate DC-3 like feel in modern aeroplanes.

Buffet was not noted on CVRNeither was any explicit comment on stall warning, however there was an inanimate object that provided some clue on CVR:

This modification of the behaviour resulted in the appearance of a high frequency
component of an amplitude increasing to up to about 0.1 g peak-to-peak, and with
a signature that is very different from a turbulence signature of aerological origin.
Furthermore, there is a noise on track 1 of the CVR, at about 2 h 10 min 55, which may
be the impact of the microphone striking a panel, heard at a stable frequency.

Buffet was determined by analyzing accel.Well, not just that. As pre-stall buffet is defined and measured at cockpit and IRS tend to be near C.G...

Additional analyses were conducted with Airbus to determine if this phenomenon
could correspond to buffet. The identification of this phenomenon is complicated by
the fact that the concept of buffet is defined as accelerations at the level of the pilots’
seats and not at the centre of gravity...some test flights were flown:
Airbus subsequently flew special flights to collect more accurate data at high angles
of attack and with an aircraft configuration close to that of the accident (mass, flight
level, Mach, etc.). These tests made it possible to refine the preliminary correlations
and to establish that the level of buffet was considered to be a deterrent by the test
pilots when the angle of attack was about 10°, corresponding to normal acceleration
amplitude of 1 g at the pilot’s seat. This angle of attack was reached at about 2 h 10
min 57 s during the accident flightHowever, I believe 1g to be a typo in both French and English versions. 0.1 G is more likely and nevertheless represents very significant vibration. At 1G amplitude, aeroplane would be buckling like mad.

The aC did not pitch nose down at Stall. Because CM2 got in his head that he has to keep the nose high, even if it meant setting TOGA and pulling all the way back. That's the only constant about his behaviour; he pulled when stall warning blared, he pulled when it did not. He pulled when F/Ds told him to pull, he pulled when they were knocked out.

He was quite successful in keeping the nose high, too.

pull and pull to the limits and run outta energy while transitting the stall protection limits, then get to new territory. pushing forward would have equally bad outcomes if the "overspeed" "protections" ( how I hate that term) are FUBAR due to invalid speed inputs to HAL.
We are getting somewhere. Insane pushing could eventually get as dangerous as insane pulling. So question is why push or pull at all? Many a crew has survived the UAS ordeal by making no reaction to turbulence induced, high Ma induced low threshold stall warning at all, just keeping the usual cruise attitude. They would if they have gone for memory items, too.

From the CVR fidelity ( could detect switch changes) and the comments by the troops, doesn't sound as if the AB330 has pronounced buffet in the stall regime. I don't mind having shaker or blinking red STALL light installed on Airbi. I explained why it was not required to be installed. Also I believe it would not make a lot of difference in AF447: I'm not buying aural saturation theory. Seemingly CM2 disbelieved everything he has seen or heard and somehow got idea pulling will get him out of the situation. Too bad he didn't comment out loud what he believed was going on, like capt of Birgenair 301 that first told his crew to disregard the warnings only to break down a few minutes later and dismiss every speed information as false, when 2 out of 3 were correct.

Why did the Captain not get a useful handover when he returned to the cockpit? Because co-pilots' performance in the cockpit was not matched to circumstances and can be described as useless.
Had things already degenerated that much. In my book, 40° AoA in public transport category aeroplane is that much degeneration.

Guess the TAM folks proved the Air France FCOM wrong?Pardon my level2 English: I meant to say that usual Frankensteinan idea that aeroplane has suddenly turned into monster prepared to kill her masters at the slightest provocation, which surfaces almost every time someone is killed in aeroplane accident, has no merit. FCOM recommendation to manoeuvre with care absolutely doesn't imply that very gentle adjustments of the sidestick are required. While TAM crew went against the recommendation of care, their roller-coaster ride did prove you can get away with being severely ham-fisted in high-altitude manual flight, as long as amplitude and average of your shenanigans keep you inside the envelope.

In law degradation, or control problem or whatever, control displacement or force gets second seat to taking feedback from instruments! "Hoot" Gibson did not care a little bit that post-dive it took him almost full roll control and considerable force to keep the aeroplane level, he was just interested in keeping it level and applied as much deflection and force as needed to achieve that goal. As should any instrument rated pilot.

I am sorry Sir, that I gave you credit for something that didn't deserve credit. Apology accepted.

It's a clue that you've just entered a region of much warmer air suddenly.No trace of it on FDR concurrent with the comments. Blockade of TAT probe did rise the apparent temperature 40 seconds after the comments were made.

[RetiredF4]

Quote:
Originally Posted by Lyman
The aC did not pitch nose down at Stall.

Clandestino
Because CM2 got in his head that he has to keep the nose high, even if it meant setting TOGA and pulling all the way back. That's the only constant about his behaviour; he pulled when stall warning blared, he pulled when it did not. He pulled when F/Ds told him to pull, he pulled when they were knocked out.
He was quite successful in keeping the nose high, too.

Just to make sure that it is now understood, that after the initial pull with too high pitch attitude "not pulling" anymore" would not have been the solution to get the nose down by itself. A nose down push is necessary to change the trajectory in ALt2.

See below. I know, that Oozlum bird again....


BEA final report 2.2.5 (my bolding)
However, positive longitudinal static stability on an aeroplane can be useful since it allows the pilot to have a sensory return (via the position of the stick) on the situation of his aeroplane in terms of speed in relation to its point of equilibrium (trim) at constant thrust. Specifically, the approach to stall on a classic aeroplane is always associated with a more or less pronounced nose-up input. This is not the case on the A330 in alternate law. The specific consequence is that in this control law the aeroplane, placed in a configuration where the thrust is not sufficient to maintain speed on the flight path, would end up by stalling without any inputs on the sidestick.

[slats11]

OK so no spike in TAT concurrent with increased cockpit temperature.

So what else can suddenly lead to increased cockpit temp? I mean both guys commented on an abrupt and significant increase in temp. That's odd surely. So what are the possible explanations for this? (other than increased TAT overwhelming climate control which the evidence does not support as the explanation)

[HazelNuts39]

However, I believe 1g to be a typo in both French and English versions.

BEA#3 page 17: Note 1: The appearance of buffet (buffet onset) is defined by an oscillatory vertical acceleration whose amplitude reaches 0.2 g from peak to peak at the pilot’s seat. The notion of deterrent buffet is subjective.BEA#3 page 44: Note: Examination of flight test data revealed, based on the frequency and amplitude, that this signature could in fact be that of buffeting. By drawing analogies with the flight tests, the amplitude of 0.1 g at the centre of gravity suggests that the amplitude of the buffeting at the pilot seat is high (approximately 0.6 g peak to peak).I don't think it is a typo. Buffet onset is defined as 0.2 g and is considered the lowest level of perceptible buffet. The buffet onset boundary is scheduled in the FCOM and QRH. In the conditions of AF447 it occurred at M=0.64 and AoA=7.7 degrees. The 'deterrent' buffet described on page 93 of the Final Report is so severe that it is considered an effective deterrent to further speed reduction, so that in certification stall tests the airplane would be considered 'stalled' and recovery would be initiated as soon as that condition is reached.

P.S. Sequence of AF447 events:
02:10:51 AoA=6 deg, stall warning triggered
02:10:53 AoA=7.5 deg, buffet onset
02:10:57 AoA=10 deg, deterrent level of buffet reached

[rudderrudderrat]

Hi slats11,
OK so no spike in TAT concurrent with increased cockpit temperature.
There are very few TAT recordings reported.
However, please see the report published in July11, page 86.
Time 0hr.09min FL. 34.992 Static temperature (°C) -43.5
Time 2hr.10 FL 35.044 SAT -38.8

From the CVR report:
02.06.54 the crew say "Minus forty-two we won’t use the anti ice that’s a plus."
02.08.41 "What's that smell" .. It's Ozone...You can feel already that it's a lot hotter...It's amazing how hot it is all of a sudden.."
02.09.40 Change in background noise (from impact ice crystals)
02.10.03 Engine anti ice is turned on (in response to TAT being warmer than -40)

The TAT has warmed from -42°C to -38.8°C over a very short time.
They must have just entered the warm rising air of a CB.

The Turbine Bypass Valves in the Air Conditioning Packs move slowly, the SAT rise was felt by the air conditioning temperature rise.

[slats11]

The TAT has warmed from -42°C to -38.8°C over a very short time. They must have just entered the warm rising air of a CB.

OK. But this is at odds with Cllandestino

Originally Posted by rudderrudderrat It's a clue that you've just entered a region of much warmer air suddenly.
No trace of it on FDR concurrent with the comments. Blockade of TAT probe did rise the apparent temperature 40 seconds after the comments were made

So did the outside temp really increase as the crew believed (and turned on anti-ice)? Or was this increase due to a blocked TAT probe?

OK. Assuming they are talking about increasing cockpit temp rather than outside, I guess the possibilities include:
1. Increased heat production within cockpit. Unlikely.
2. Increased transfer of heat into cockpit. Increased outside temp and lag in climate control adjusting for this would be one cause, but there are others..
3. Decreased transfer of heat out of cockpit.
4. Loss of (or decreased ) air flow around the pilots leading to decreased evaporative cooling. This would only cause an perception of increased temperature rather than a true increase in temperature.

Many of these explanations involve altered internal air flow. So what exactly is the "change in background noise" noted twice at 02.08.17 and 02:09:40. During this 83 second period, the PF questioned whether the PNF had adjusted the A/C, both pilots noted a smell of ozone, and both pilots noted increased cockpit temp.

I can accept increased TAT due to rising air from Cb, and this explains the ozone. However Clandestino states TAT did not rise during this period, and further that the FDR did not record a change in vertical acceleration.

If Clandestino is correct, there must be another explanation for the increased temperature. The changed background noise and the smell of ozone (or whatever) may be relevant to this explanation.

[Rockhound]

Lyman,
Yes, my question was rhetorical. I fail to see what the temperature has to do with how the crew handled the last four minutes or so of "flight".
Slats wrote: The captain seemed very slow to act.
Slow to act? The captain did not act at all. He merely dispensed advice, some of it useful (use the rudder rather than the ailerons), some of it not (repeatedly urging that the wings be kept level), and at one point exclaimed despairingly "Damn, that's not possible!" (without specifying what wasn't possible).
I always thought the captain is the guy who's supposed to take over when things go pear-shaped.
Slats is also under the impression that the PNF had better situational awareness than the PF.
This is debatable. When the PNF formally took control from the PF, at 2:11:37.5, instead of pushing the sidestick forward, he held it hard left exactly as the PF had been doing. That's just one example of deficient SA. However, to his credit, the PNF did realize that they were not in an overspeed condition and told the PF smartly to stow the speed brakes that he was deploying at max thrust at FL297. Incidentally, this episode elicited no comment from the captain.
No, Lyman, you could not make this stuff up.

[HazelNuts39]

I can accept increased TAT due to rising air from Cb, and this explains the ozone. However Clandestino states TAT did not rise during this period, and further that the FDR did not record a change in vertical acceleration.Blockage of TAT probes tend to occur suddenly, similar to pitots. In this case the TAT rose gradually between 2:09:52 and 2:10:04, while the airplane was entering a vertical gust that reached 22 kt at 2:10:03.5 - see figure 64 of the Final Report, the correct one, not the figure 64 erroneously included in the English version.

[rudderrudderrat]

Hi slats11,
OK. But this is at odds with Clandestino
It probably is - but I'm using BEA's reports as my reference, not something that Clandestino thinks.
So what exactly is the "change in background noise" noted twice at 02.08.17 and
02:09:40.
From the CVR report 2012, page 23:
"2 h 09 min 46. Background noise increases (typical noise of impact of ice crystals, identified by A330-340 pilots) "

However Clandestino states TAT did not rise during this period, and further that the FDR did not record a change in vertical acceleration.
The autopilot was engaged, flying ALT CRUISE. Why do you think there would be a change in vertical acceleration? The AP would simply reduce the pitch attitude slightly.
I posted the FDR TAT record in my previous, and the crew's observation of the TAT.

They are all classic symtoms of flying into CBs.


If Clandestino is correct, there must be another explanation for the increased temperature.

Excuse me if I don't hold my breath.

[slats11]

Blockage of TAT probes tend to occur suddenly, similar to pitots. In this case the TAT rose gradually between 2:09:52 and 2:10:04, while the airplane was entering a vertical gust that reached 22 kt at 2:10:03.5 - see figure 64 of the Final Report, the correct one, not the figure 64 erroneously included in the English version.

Fair enough. Thanks for clarifying. So then why did both pilots notice increased temp more than a minute before the TAT increased? If rising TAT led to increased cockpit temp, then the sensed TAT (measured externally) should rise before this warmer air led to increased cockpit temp.

"2 h 09 min 46. Background noise increases (typical noise of impact of ice crystals, identified by A330-340 pilots) "

Sure, the report explains this instance of increased background noise as being due to ice crystals. It makes no interpretation of the two previous references to change in background noise at 2.08.17 and again at 2.09.40. The CVR transcript merely states "change in background noise". These comments are earlier, on page 22.

[Lonewolf_50]

Y'all have been having some fun since I last visited.

Clandestino
gums
Good grief, Doze, how ya gonna get an overspeed warning if the air data system is FUBAR? Good grief, Gums, where would the energy for overspeed come if you are at practical ceiling and pulling up like mad?

clandestino
gums
So maybe the junior crewmember up front was more worried about overspeed than stall or something else.
Maybe, but if he was, he was dead wrong and consequently just dead.

I'd rather be in a bar with you two, talking this over, a few pints included. T'would be goodness.
clandestino
AP was off and by the time descent started it was blocked off by ADR rejection due too to low forward airspeed. Capt was unable to grasp the situation so he thought it would be good idea to press the non-function AP button, without explaining it, either for the benefit of co-pilots or CVR.

Your analysis, not necessarily a fact. But I'll bet with your read on that one, if we have to go to Vegas on that.
gums
I read the CVR again, and the experienced pilot is telling the other guy to stop climbing and to be "gentle". After a minute of fruitless talk, he calls for the aircraft commander. All the while the stall warning doofer is going off.
This is CRM training module X: What does it take for the copilot to say "I have the controls," take the controls, and make the right thing happen? Over to the cockpit gradient sub discussion we go ...
Rockhound
Why was there not a proper handover to the captain when he returned to the cockpit?
slats:
Why did the Captain not get a useful handover when he returned to the cockpit? Had things already degenerated that much. He got garbled bits if information plus lots of warnings and alarms plus a feeling that things were not right ( abnormal pitch attitude). It would have been perplexing to understand what had gone wrong in the brief interval since he had left the cockpit.
The PF was task saturated. As I analyze the event, PNF had at least partially bailed out (mentally) when he called for adult supervision. (Aircraft Commander). The clue to this for me was the "where is he" and frequent call up.
That aside, the time and environment for "briefing" is when you are in control of the situation. The two up front were, from the evidence, NOT in control of the situation, but were playing catch up.
slats:
It would have been perplexing to understand what had gone wrong in the brief interval since he had left the cockpit.
Yep. Fatally perplexing.
Although we don't have the audio, it is likely that PF and PNF were somewhat agitated (or more) when the Captain returned. Lack of clear handover. And then confusion, lack of assertiveness, and likely increased agitation.
That's how I'd bet it in Vegas.
mm43
Nothing coherent (crew wise) happened in that cockpit from the A/P disconnect through to the end. It would seem that the BEA's Human Resources Group were not able to format a reasonable explanation for this behaviour either.
They were left guessing, but one wonder just what the "command climate" is at AF, and in AF cockpits. (Air France, not Air Force, about whom I have other doubts. :E)
Clandestino:

Because CM2 got in his head that he has to keep the nose high, even if it meant setting TOGA and pulling all the way back. That's the only constant about his behaviour; he pulled when stall warning blared, he pulled when it did not. He pulled when F/Ds told him to pull, he pulled when they were knocked out.
He was quite successful in keeping the nose high, too.
Seemingly CM2 disbelieved everything he has seen or heard and somehow got idea pulling will get him out of the situation.

Training issue, and possibly an Airbus and Air France Indoctrination Issue. Education and training go hand in hand with indoctrination.

HN39 in re buffet: thanks, well explained!


The TAT has warmed from -42°C to -38.8°C over a very short time.
They must have just entered the warm rising air of a CB.
I almost hear Linda Ronstadt singing "Heat Wave" in the background.

Rockhound
No, Lyman, you could not make this stuff up.
Well said. Truth is once again stranger than fiction.

[philip2412]

maybe i can get some support from hf experts, because it`s quite difficult to explain with my bad command of english.
there`s something missing from the BEA report,which in my mind is one important cause for the crash.
the command structure in the cp when the cp left.Bonin was the assigned pilot flying although he was younger and had less hours on type.
Maybe there was one though on his mind,that when the cp returns,he didn`t expect that he,Bonin , had given up command.that maybe the reason for taking back command from dubois .And dubois thougth the same: the cp does not expect me having taken command when he comes back.
that could be the reason for such bad crm.
I´m sure had command been given to dubois by the cp that he would have taken command immediatley from Bonin because he had a right guess.

[gums]

Thanks for finding that pearl about the static stability, Retired. Thank you, thank you.

For those that have not flown a FBW system that has "limits" or "protections" embedded in the flight control laws, you are only commanding control surface deflections when rotating on the the runway to get airborne. So if the system is using gee as the primary "command" or even "limit", then the elevators could be moving all on their own despite your stick inputs to achieve that gee. This is a player when at a steep climb unless the system compensates for the pitch attitude ( as the 'bus does in Normal law). The system will move the elevators and THS to achieve 1 gee, but you really should be commanded less than 1 gee. For example, at 30 deg of pitch we should be holding 0.87 gee to maintain a 30 deg pitch while climbing ( honest, the VooDoo required that until about 25K when in an afterburner climb). If you command 1 gee, then you continue to increase pitch attitude.

And now, Airbus shows us that the jet DOES HAVE a point on the pitch coefficient curve that is "neutral". It's why I jumped in here initially to show that the Viper has such a point and we didn't find it until well into the program. But the combination of relaxed static stability and the control laws ( gee command and AoA function) allowed us to get to a deep stall and stay there with hands off the stick. We got there by doing exactly what AF447 did - climb at a sufficient angle and power setting to run outta energy/aerodynamic effectiveness of the elevator before the system could get the nose down. I posited this scenario the instant I saw the graphic of the wreckage. Looked like a classic deeply stalled jet pancaking into the water at a high, very high AoA.

The BEA comment about positive static stability and stall entry was a good one. Before FBW, it worked. You had to work hard/pull hard to get to the stall. Let go and most planes would pitch nose down to achieve the trimmed AoA. But the FBW systems will allow you to get to the stall if the laws are heavily biased for gee command, and do not blend in AoA, pitch rates and so on.

The second "aha" for me was the buffet values were established. Certainly high enough for most pilots to realize that something was wrong, as in an approach to a stall. Before this, I felt that the jet was so smooth that a stall entry buffet was too low to provide a tactile warning. Personally, a buffet of 0.1 gee Nz seems adequate to provide a warning without any fancy chimes/clangs/etc. And a buffet much higher than that once in the stall should have been a very big indication of what the jet was doing.

The good news is that we can train to handle the situation, even prevent the situation.

I would also like to see Airbus use the AoA in conjunction with the gee command to keep the jet from trying for gee "uber alles". This is in alternate laws, as the thing seems to do this in Normal.

The air temp and ozone stuff seems irrelevant other than distracting the crew. And an apology to OKie. I wanted to fly the F-4 when it first came out, and even a C-130 if I couldn't make the cut for fighters. Nevertheless, I never wanted the degree of responsibility required to get a few hundred folks to their vacation venue, so took a pass on an airline job once outta the fighter community. If I screwed up, then it was my skinny butt and not a slew of others. Just my personal philosophy, and no offense to all here that have accepted the responsibility and have survived along with their passengers.

[BWV 988]

02:10:51 AoA=6 deg, stall warning triggered
02:10:53 AoA=7.5 deg, buffet onset
02:10:57 AoA=10 deg, deterrent level of buffet reached

With severe buffet at 02:10:57, the Captain would have felt it too. He must also have noticed an unusual, continued climb >1/2 min before that.

So why didn't he return to the flight deck earlier than 2:11:40, and should he even need a briefing from PNF to connect those dots?

[RetiredF4]

BWV 988
With severe buffet at 02:10:57, the Captain would have felt it too..........

I think that´s not a too difficult question to do some guessing answer.
While expieriencing buffet while flying through bad weather seems a normal and often expierienced event, buffet due to approaching stall sure was the first time in their life in an aircraft.

And even in the simulator AFAIK stall approaches are not trained with nose high attitudes but beginning from decelerating in straight and level flight.

The mindset of the complete crew was not orientated to a loss of control situation in the classical sense, meaning stall, but in the sense that the aircraft does not react like expected. "What´s happening? We dont know......"

BWV 988
He must also have noticed an unusual, continued climb >1/2 min before that.

In a full motion simulator we can feel climbs and descents, acceleration and deceleration along the longitudonal axis by just tilting the box. So pilots are not used to base their judgement on the bio vestibular system when lying in the crew bunk or being on the way to the cockpit.

When pitch is established (lets sáy 10°) and the aircraft is decelerating, the body would feel a descending sensation even if still climbing.


BWV 988
So why didn't he return to the flight deck earlier than 2:11:40, and should he even need a briefing from PNF to connect those dots?

Answer see above.

[Rockhound]

Philip,
I think you have confused the cast of characters. The captain's name was DuBois, the left-seat copilot was Robert and the right-seat copilot was Bonin.
When the captain left the flight deck to take his rest, Robert had just returned from his rest. The captain did not unambiguously assign crew responsibilities in his absence. For example, although Robert occupied the LHS, the captain did not explicitly designate him PIC.
What do you mean by "cp"?

[Lyman]

@slats11.....

"OK. Assuming they are talking about increasing cockpit temp rather than outside, I guess the possibilities include:
1. Increased heat production within cockpit. Unlikely.
2. Increased transfer of heat into cockpit. Increased outside temp and lag in climate control adjusting for this would be one cause, but there are others..
3. Decreased transfer of heat out of cockpit.
4. Loss of (or decreased ) air flow around the pilots leading to decreased evaporative cooling. This would only cause an perception of increased temperature rather than a true increase in temperature."

Could I add...

5. Loss of dedicated cooling to the avionics.

A lot of stacks of heat producing equipment. If I was a smartie, I might exhaust the heated cooling air from the avionics bay into the cockpit environment?

Might that explain the smell?

Might be easy to check, it could be entirely off base... If a fan motor went tu, could it produce the noise referenced by BEA as "increased cockpit noise" (unidentified)?

BWV988

02:10:51 AoA=6 deg, stall warning triggered
02:10:53 AoA=7.5 deg, buffet onset
02:10:57 AoA=10 deg, deterrent level of buffet reached
With severe buffet at 02:10:57, the Captain would have felt it too. He must also have noticed an unusual, continued climb >1/2 min before that.

So why didn't he return to the flight deck earlier than 2:11:40, and should he even need a briefing from PNF to connect those dots?

Long ago, I reminded myself that a return up the aisle to his (Captain Dubois) office would be seriously "uphill"... Quite a climb actually...About four times as steep as he may have "expected". He walked into three seconds of STALL WARN, so combined with the uphill climb and the chirp of STALL: "hey knucklehead, get the nose down, you looking for a swim?"

At this point, and due to Autotrim, if he continued to use Approach to Stall recovery method, he would merely "relax" back pressure, not actively lower the nose, and the THS would prevent the nose from dropping, further confusing the frustrated recovery... If there was one.

[rgbrock1]

As a non-aviator I was interested in the many posts referring to Buffet. So I did a little research on my own with the hope of understanding this phenomena. I think I have a basic idea of what Buffet is. (Both over speed and under.)

So, the question I pose is this: could both the PF and PNF, distracted as they were by so many issues going on at the time, have thought that buffet was, instead, a result of turbulence? (The same turbulence which PF was obviously so focused on prior to AP disconnect.)

[Lonewolf_50]

rg, that's an interesting question. I surmise from three years of discussion on this topic that few to no A330 pilots have been in a training flight that included actual stall buffet. As I understand the training rig, pre stall conditions are responded to with a series of actions to prevent getting into a stall. (There is considerable merit in "an ounce of prevention being worth about 230 tons of cure" as shown by this case. :{ )

Note: If I am wrong about this training regimen, I ask the A330 pilots and trainers to correct my surmise. Being wrong is one way to learn something.

[Lyman]

Hey rg... Any question will get you several answers here. Here's mine.

Of course the Buffet was charged off to turb, else they would have mentioned it.

Slag on, mc duff.