447
 

3holelover, I agree with most of what you say. I will go a step further by saying that part of airmanship is not to fly a heavy airplane at high altitude near the coffin corner, through Cb's. I get a kick out of the entire discussion about different "laws" and how to recover from a high altitude stall etc. etc. when this whole thing could have been avoided by diverting around the storm. That simple !! It's unbelievable how much this thread has gone off on a tangent to somehow blame the 'plane or the lack of knowledge in high altitude stall recovery. And one other thing. It wasn't ice crystals that caused the pitot blockage, it was supercooled water which froze on contact with the pitots. That same SC water would have made the AOA vane inoperative also. It would be helpful if we could stick to the real facts in all discussions. Just stay away from CBs at high altitude. End of story.

Since AF447 HAD AoA vanes, and they actually continued to provide good data except when invalidated by the system due to low airspeed, how do you conclude that the AoA vanes would have been inoperative? They were in the same atmospheric conditions as the pitots. The pitots couldn't cope, the vanes did.

No! AoA Vane #1 was having a 'rest' well before the AP disconnect.

http://oi51.tinypic.com/sfw9ic.jpg

Diagnostic/Zorin 75
 

I respectfully submit that the very length of these various threads on AF447 in itself indicates a widespread enough fear in many quarters that other high altitude UAS events on various aircraft could all too easily end equally fatally (under circumstances identical or very similar to AF447).......

Hi Clandestino,

The most important warning on that flight deck was "Stall Stall" - which appears to have been ignored / not acknowledged / not heard. (Similar to the You Tube "What's that Beeping?")

If their human auditory channel was filled to capacity with previous flight deck audio noises, (Cavalry Charge, ECAM Dings, ALT Alert etc), and the crew are attempting to verbally communicate whilst they trouble shoot - what is the point of having the only stall warning alert simply another verbal "Stall Stall"?
Even my iPhone has both audio ring plus Vibrator to get my attention.

Do most other aircraft have a stick shaker as a stall warning? If Apple can fit one into my phone, why was it not possible to fit something similar into the side sticks?

Before AF447 event, there was NO Stall Warning QRH procedure. The previous procedure was buried in FCOM.
The new QRH procedure emphasises reducing angle of attack, and does NOT recommend the use of TOGA power. (as the old FCOM procedure did)

- not a complete picture since the 'cessation' of the warning was recognised? Time to think again.

Shakers are installed if natural pre-stall buffet is too weak to be recognized (or non-existent). I hope final report addresses whether the Airbus got through certification too easily or FBW Airbi indeed have sufficient natural buffet to warrant omitting the stickshaker. I agree that with sidestick, effective shaker needn't be much larger than those used on modern cellphones.

All transient and not going off simultaneously with stall warning. IIRC even if they were trigered simultaneously with stall, stall warning overrides all other audio alerts.

Same way that you recover from mid or low alt stall. Hint: therr's difference between approach to stall and stall itself, which is seldom appreciated on PPRuNe.

If this theory is congfirmed by HF group, that would show complete incap on the PF side. Unstalling by pull? Only when flying inverted or you're doing some very serious aerobatics.

Because it was assumed that pilots understood stall & recovery from day one and never forgot it. Whooops.....


Little less respectfully, I offer alternative explanation: as usual, fatal accident wakes many up to the reality of aviation being a very hazardous game. Length of the thread is due to inability to lay our fears to sleep with usual lithany of "It was only loco/Africa/Russia/Asia/Latin America/cargo anyway"

Hi Clandestino,

Then why did the QRH have "EGPWS ALERTS" in the Emergency Procedures?
Using your logic - you would think that "Pull Up" before hitting the ground and apply TOGA power would be instinctive - so why include that one?

I think Airbus believed they had designed an aircraft that was so well protected and that the chance of stalling was so remote - that a Stall Warning QRH procedure was deemed not necessary.

With the benefit of hindsight - that has now been fixed.

You'll find that every Boeing & Lockheed has a dedicated stall warning stick shaker.

You'll find that every Boeing & Lockheed has a dedicated stall warning stick shaker.

Which can and has been ignored by pilots. It is important to remember that this is not an accident related to the aircraft configuration. It is an accident related to aircrew behaviour.

Pavlovian
 

Which would appear to be a trained and ingrained 'by rote' behavior with little actual practical follow-up training.

@Old Carthusian:
All very true, sir.

However, in the spirit of trying to close as many holes in the proverbial swiss cheese as possible, I see no harm in at least considering whether stall warnings via a different cognitive route (i.e. non-verbal, non-text) might be helpful - although as you say, also not perfect.

In the case of AF447, the question in my mind is whether the stall warnings were (a) not heard (e.g. cognitive overload or similar) - perhaps stick shaker would help here; (b) heard but not believed (due to multiple apparent problems with the aircraft behavior, leading especially the PF to ignore all warnings?) - stick shaker might be ignored in this case too!; (c) some other reason.

Personally, I fear that the answer is (b) but of course, I don't know. I think that rudderrudderrat has put forward a very good case for auditory overload (also Ian W) - I know that when I'm trying to speak to someone, I do tune-out all extraneous sounds; I can't tune out only selected sounds unless one sound is especially loud. So perhaps the answer is (a), and for that reason shouldn't a stick shaker be considered, for those occasions when it would help?


@mm43:
I mentioned this a few weeks back, and sensor_validation kindly pointed out a very plausible potential cause (link below) unrelated to ice (I don't know if that's what you were suggesting?):

http://www.pprune.org/tech-log/45687...ml#post6628318


@TJHarwood:
I also thought you were right. I was only replying to (what I believe) Clandestino was saying, where he seemed to be saying that if 32 other crews could manage clogged pitots successfully, then AF447 was the exception. The reason I posted was that this assertion seemed to conflict with the data & analysis presented in the 2nd Interim BEA Report (which I found very interesting, as it touches on some aspects of my professional life).

If I misinterpreted what Clandestino was saying, and if everyone agrees that some of the other 32 incidents were also (or could, in other circumstances like in turbulance, at night, at FL350, have developed into) "close shaves", then I happily withdraw from the conversation for the moment. :)

Actually, I think they (and others) took the position that not only was it not necessary, it was actually prohibited, at least from the flight manual.

The idea that you recover from a stall by pushing the nose down was felt, at least by some, to be such basic airmanship that it was actually prohibited by regulation from inclusion. Airbus were not alone in having no such procedures.

That's really impressive data visualisation - brings out the difference between the PF and PNF's responses and also the dual input events.

(A thought - when we want to focus on the trend in a particular metric, we plot it on a chart like the DFDR traces. Strangely, aircraft displays show scrolling numbers or else multiple needles. Would a "value plus trend-line" be better? Medical monitoring displays do this.)

My wild-assed guess in this situation would be that stall recovery is taught in single-engined trainers from very early on in basic aircraft handling training. Most single engined trainers are not equipped with EGPWS.

Well, it's an opinion with merit in a theoretical sense, but I'd be surprised if that tured out to be the case. I remember reading an interview with a pilot in "The Tombstone Imperative" in which he advanced the opinion that things like stall recovery and microburst recovery have been mitigated by the arrival of the large high-bybass turbofans that were introduced with the widebodies and were installed on every new jetliner from the mid-70s onwards - you could just apply TOGA and keep the wings level and the AoA within a certain range and power out of it. It now appears that this is not always the case.

What makes your assertion doubtful for me is that if Airbus truly ever felt that way then they would not have put a stall warning in the aircraft in the first place - yet they did. So from an engineering perspective at least, Airbus always knew it was possible.


So did the VC-10, BAC 1-11 and HS Trident - in fact they pioneered the technology. However, as D.P. Davies said in the third and final edition of HTBJ, pilots had trouble trusting them and adjusting to their presence. Stick shakers in the Trident, 727, 757 and MD-80 have all been ignored on the line with fatal consequences.

As to the other discussion, the presence of supercooled droplets in the area AF447 flew through is debated. Even the BEA won't put the pitot failures down to anything more specific than "ice crystals".

Hi,

DW
Incorrect
This is a mandatory specification from regulators .. nothing to do with any Airbus decision.
As for a Airbus be able to not stall .. it's true .. for Airbus Industrie (or EADS)
This is black on white from Airbus
No training necessary for stall condition
This is one of the point in their commercial incentive ... low cost training

Note (from BEA report N°3 page 63)
Before this date .. Airbus don't write about "Stall recovery" .. but instead .. "Stall warning"

And this is the change made after the AF447 accident (BEA report N°3 page 82) for the simulator training

Yet .. nothing about training for stall recovery ..........

Ice crystals ? .. well I wonder what can be a training in flight simulator for "ice crystals" ....
A employee of the training center trowing ice crystals on the simulator casing ? :eek:

I am almost certain that these new workouts are not going to make more significant progress in terms of flight safety.
Only the real flight training will provide pilots with the mastery of certain events
More flight simulator training for this kind of event it's just like put a additional (redundant) fire alarm horn near another instead construct more fire escapes
You can't save lifes with a supplementary horn .. you can just spare money for short term .. but problem not solved (I was there)

Then stick to your words, concentrate on the facts and give a break to your snobbish and pompous style, that won't hurt.

Basic rule : Do not put words in my mouth or assume by quoting me if you pretend I have said so ...


I would rather think, according to the serial number, that F-GZCP was the Enhanced version of the 330.
I believe airfrance has or had 16 A330, 4 of them being A330E.
F-GZCP was also the newest in the fleet.

As you may have more accurate information ... please, let me know.

AoA Vane #1
 

Well it could be related to ice, or it could be related to the EASA AD, and there is no way of proving it now. Though looking at the traces (when valid), it was tracking again prior to 2:12:20.

In any case, it wasn't an issue in ALT 2B as the SW used the highest AoA value.

Air France F-GZCP (Airbus A330 - MSN 660) | Airfleets aviation

F-GZCP was an A330-203. As far as I know, they didn't retrofit design changes from later models to later production runs of earlier models because of the training issues that would ensue (pilots reported a significant difference in feel between the old system and the new). So for the moment let's assume that F-GZCP was of the old design when it came to the rudder controls. Either way I don't think it matters a great deal regarding this accident because the rudder barely came into it.

Still waiting on your reply on the other thread by the way...

AoA Vane #1
 

@mm43:
Agreed, sir - my point is just that we do have another plausible potential reason, and so I don't think we can say the AoA vanes (specifically #1) were definitely affected by ice.

I'm interested - other than the Perpignan incident (where the AoA sensors had been "abused" outside their specs before the flight), is ice affecting AoA sensors as much of a problem as pitot icing?

Rudder
 

DozyWannabe dared writing :

Read the report in full, including page 1xx where you will find the rudder traces. Just because BEA did not expand on the subject does not mean it is irrelevant.

You yourself have used the expression PIO (which stands for Pilot Induced Oscillation). Experts now prefer APC event (Aircraft Pilot Coupling), which better emphasizes the interface issue. There is a definite APC event in this instance, in roll and yaw. Rudder played a huge part, as a fast-moving, oscillating control surface with zero feedback to the pilots.

Regardless of what actually caused these oscillations, and why did PF had such trouble keeping the ship's wings level, rudder certainly played a major part in the whole sequence.

That the system governing this particular control surface was subjected to a large update is in itself source of questioning.

Yes, looking at the traces is dull work. But as long as we take these recorders for the truth of the matter, the traces are all we have as unbiased data, along with the ACARS messages. Unless one is prepared to use and study them carefully, one can only follow pre-made conclusions written under careful supervision by interested parties. Such should not satisfy an inquiring mind.

@Svarin:

Question - if there is no feedback through the rudder pedals of an A330, how come pilots reported a significant difference in feel between the earlier A330/340 (200-300) models and the later A340 models (500-600)?

And by "barely came into it", I mean that it came into it after control was lost, and was very much secondary to the pitch and roll inputs that went through the sidesticks.

One thing that I find interesting in the traces is that the sidestick traces are based on a graph where left stick input relates to values > 0, whereas roll traces say that values > 0 relate to right wing down. If this is that case then PIO/APC needs to be looked into, as the traces of roll vs. sidestick show the precise opposite.

PS. I like the term "dared" - it makes me sound like a far more "caution-to-the-wind" guy than I actually am. :)

Adverse yaw
 

It´s a reaction, i´m quite familiar with from big ugly F4, caused by adverse yaw in combination with swept back wings.

Might be the same here. That would also explain the nosedrop in addition with the max bank angle points and the nose rise when by use of rudder the bank reversed.

As i don´t know it, others comments more than welcome.

F4 flight characteristics High AOA
With high AOA the down going aileron (in our case on the right wing) produces a lot of drag (the down gong aileron stands nearly 90° to the FPA). That produces a yaw into the low right wing. We had the spoiler on the other side go up, but that one was blanked out at high AOA. The wings are swept back as we know. Due to the yaw to the right the right low wing looses lift, as it is now more swept back in relation to the relative wind, wheras the left wing is moved forward and is less swept back in relation to relative wind. The right low wing therefore produces less lift than the left high wing, minimizing, equalizing or even overcoming (dependent on AOA) the upforce of the deflected aileron on the right wing. Live expierience: Full left aileron and the ship rolls to the right. Only help is use of rudder in the same direction as rolling is intended. In our F4 best was to roll with rudder alone and keep the ailerons at neutral.

(bolding by me)

(bolding by me)


If i read the TTM correct, automatic countering of yaw/sideslip would not be available in ALt2.

Are you discussing the control of the aircraft when stalled ? If so, surely the control characteristics are markedly different from what anyone is used to in normal flight, and the aircraft response ditto. Aircraft seems to have been very well behaved given the situation.

You have interpreted me kind of correctly, sir. I was pretty serious when I mentioned curves of crew performance available vs required. It is possible that some of the crews exposed to the pitot icing under the circumstances of AF447 crew would have gone through the same motions and ended up similarly. It is possible that AF447 crew would have made much better job under more favourable circumstances, however such speculations are only useful if they bring us closer to answer why the crew did what they did. Only when this is answered we can proceed to "How do we prevent it in the future?"

Number 32 was often quoted in threads referring to AF447. I was able to trace it as far as PBS show "Crash of flight 447". Interim report #2 refers to 33 cases preceding AF447 and four occurring afterwards. In those cases that could be further analyzed, crew pushed forward when faced with stall warning, CM2 of AF447 pulled and kept pulling. My entirely subjective criterion of exception is thus met.

Actually it is Interim report 3, page 112, Lateral parameters.

There is not in yaw.

To have PIO/APC you have to start with pilot's oscillatory input. Rudder starts to oscillate without pilot's input at about 2:11:45 (following yaw damper commands) when the aeroplane is so deeply stalled that high AoA and low speed make it pretty inefficient. There's fast pedal movement to the left at approximately 2:13:05, followed by sharp reversal to the right and return to neutral over next minute. No oscillatory inputs. No APC. Just an aeroplane gently mushing in stall.

I could not put it better myself, sir.

Reasons to ignore stall warnings:
 

Indeed, a major puzzle why ignore the stall warnings for 3 or 4 minutes? In the entire transcript of the incident not once was "stall" or "décrochage" ever mentioned by any of the 3 pilots.
Reasons
1. Both FOs overloaded for 4 minutes and did not hear it.
2. Both FOs heard it and ignored it as being false (as per recent QF72 etc malfunction.) But why not verbalize that?
3. Both FOs didn't understand it/unfamiliar "<Stall><Stall>. What's that?". Would the french décrochage or flat line tone been better warning? Were they verbalizing that they did not understand it. Perhaps confused in the heat of the moment. Or did "What's that?" refer to something else.
4. Both FOs heard it and accepted it and did not know what to do. Again why not verbalize that?

The case for cognitive overload is by no means proven I am afraid. Iain W's reference to Wickens was somewhat simplified and didn't really offer a suitable explanation. It does sound seductive but is only a small part of what is a complex theory. Once more parts of the theory are included cognitive overload falls by the wayside. I highlight the states of panic and shock as more likely causes for the PF acting as he did because the characteristics of those states better fit his actions than cognitive overload. This also ties in much more effectively with the apparent lack of professionalism in the aircrew.

It might be that stall warnings via a different cognitive route do offer an aid in the future but we have to think about the situation as it is and as Diagnostic mentions it is possible that a stick shaker might not have saved the day. We have to look at the situation as it is and try to understand why the crew acted as they did. Then we can start to look at possible solutions which might indeed include a stick shaker. But this accident is about professionalism, training, culture, CRM and SOPs all mixed togther and above all knowing your machine. It is not about failings in the machine. I would say, a big shake up in how AF and probably other airlines train their pilots would seem to be necessary.

The examples of cognitive overload discussed seem to focus on someone who's focused on a specific task they believe is going normally, to the exclusion of an input that would have warned them it wasn't.

I wonder how well the theory applies to someone who realizes something's wrong but doesn't know what it is. It seems to me that when you go into troubleshooting mode, as the AF 447 pilots apparently did, you're more likely to step back and look/listen for clues that might explain what's wrong.

Attentional Tunneling
 

ChuChu
The effect that is repeatedly observed is that the human finding something difficult starts to enter 'attentional tunneling'. This may be called several things 'the pilot's scan broke down', he had 'tunnel vision' etc.

The pilot with cognitive tunneling may concentrate on entirely the incorrect stimulus - it is not something that lends itself to logical decomposition.

Ideally, simulation rides should be set up to initiate attentional tunneling then the ride frozen or rerun in playback and the tunneling pointed out to the 'subject'. It was found that using this approach with military pilots reduced susceptibility to tunneling.

Yet again it is back to training.

@Clandestino:
Thanks for the clarification.
Indeed - I was just quoting your mention of that number, without detailing the variations around it.

But that only addresses one reaction - to the stall warning. Other crews made different errors, which the crew of AF447 did not make (e.g. re-engaging the A/P during the UAS event). So depending on what specific criterion is considered, other crews were exceptions and not AF447. :) That's exactly why I agree with you about the subjectivity - thanks again for your clarification.


@xcitation:
Absolutely - I said something very similar earlier. :) The lack of apparent recognition of the stall warnings, but also the lack of explicit verbal reasons for ignoring them, is a puzzle.

How are we ever going to know the reason(s)? I can only think that the BEA Human Factors folks will eventually give us their best guess, which will be based on more info than we have e.g. intonation used on the CVR recording.


@Old Carthusian:
Thanks for the summary.
Agreed - many factors indeed. I also believe that there is a large dose of the "Ironies of Automation" [Bainbridge] in there too - humans monitoring machines (any) don't do very well when they have to take over completely and suddenly, with no prior warning. That seems to be a human "failing", and not something that we can (should?) expect to "train out of people".

That's why I've been following with interest the comments here about the advantages of designing some kind of "ATT Hold" autopilot in the event of UAS - something to gradually ease the transition from A/P to manual control, and lessen that "shock factor" (which is my currently favoured reason, from everything I've read so far, for the NU inputs from the PF - just muscular tension from the shock of having the plane "dumped in his lap". That's why he didn't know he was causing the climb, as it wasn't a conscious input).

I've learned here some of the difficulties of implementing something like that, especially if (as in this case), the plane is in some turbulance when it is engaged, and we may not want the current attitude (which could be momentarily significantly NU or ND in turbulance) to be the one which is held by the ATT Hold system. That requirement for the PF to control the plane in the turbulance immediately, prevented PJ2's lovely phrase of "don't just do something, sit there" (IIRC) after the A/P disconnect. :(

If the onboard systems had given the crew time to think & get up to speed, instead of immediately forcing them to react, in a state of shock from their "cruise state", I wonder if we would have had a better outcome. The Human Factors analysis of the final accident report will make facinating reading, I expect.

AoA Vane #1
 

To me, the issue is at the different level, and could be very significant.
Due to the AoA discrepancy, it is very probable that the following STATUS message was displayed on ECAM to the AF447 crew :

RISK OF UNDUE STALL WARNING
I believe blue to be the color but cannot positively find that information for now.


But once again, the real issue is that BEA didn't say yet a single word about it ...

@CONF iture

The QRH would have told them to disregard that message though - if indeed it appeared (the PNF did not call it out). At any rate, I suspect that message referred to the short-term SW that could be expected while the systems sorted out what sensors were valid and which ones weren't. I'd be surprised if any of the designers in the early '90s thought maintained application of full back stick would be the response to UAS.

WRT the BEA, give them time. They're a very different organisation these days from what they were 23 years ago.

Or, as a variation on that, they understood, but ignored or distrusted the warning preciseley (or in part) because it was in english. Already overloaded, they focused, what attention they gave to it, on the messenger and not the message.

The exclamation "shut up gringo" might ring a bell for some readers... (in that case, clearly time for the brain to process the race/language of the speaker and prepare and verbalise corresponding insult - but not to process the message content).

This page won't directly specify the status Enhanced or not of the aircraft. Only the serial number indirectly will.

http://i45.servimg.com/u/f45/11/75/17/84/af447_18.png

There is no training issue between both versions, at most a PDF document to log on.
You simply don't retrofit an earlier model in newer Enhanced one. Enhanced is much much more than a design change in the rudder engineering, starting with the size of rudder + fin.

Training
 

PF had practiced the UAS out of Rio on the Simulator three months ago (with this PNF ?) which was a 15 degree climb and TOGA, ( for lower levels). He may have tried to do just this. He was slow in increasing his thrust to TOGA on AF447. But he may have decided that this was the correct drill. His mind was set.

I have mentioned earlier one fleet in the sixties, where, in the Crew Room it was joked "that it did not matter which Drill you did... so long as you did it quickly."

More training ? Garage Years #644, says that his simulators are in use 20 hours a day with 4 hours for maintenance. One of AB's sales lines was that conversion from one AB to another AB was simpler..

Have another look at the traces and you will find the yaw damper was working and contributed more and more as the IAS decreased. The pedals were only used from 2:13:05, and all other rudder movements were from the yaw damper.

Check Post #373 and you will note that the second group of traces is a compilation of pitch, roll and rudder input. I don't think the yaw damper was helping with the roll as lateral stability decreased.

@CONF iture

Re AOA Vane #1
RISK OF UNDUE STALL WARNING

As with the STALL STALL, the lack of verbalization between the PNF and PF is a problem. No wonder the BEA want a cockpit camera.

Once again Dozy, you may not be in the best position to appreciate how a technical recommendation figuring only on the second page of a QRH procedure will catch your attention when action is taking place.

Regarding the BEA, the only thing that has changed is that corporations are getting more powerfull than ever ...

@CONF iture:

With all due respect, I'm well aware of how long it takes to pull out a QRH in an emergency situation, don't think I havent borne that in mind. However, right now we know neither

• whether that ECAM message appeared
• whether it was noted by either pilot

What we do know is that it was never called out, and that the PNF seems to have been increasingly concerned about the way the aircraft was being handled. Unfortunately there's nothing on the CVR excerpts to confirm or deny "Hey - that's a Stall Warning" - "ECAM says disregard it", but I'm pretty sure that if such a thing was said then it would have been included (if the BEA are so big on protecting corporations like Airbus, why have the DGAC already mandated a software change?). You're clearly an intelligent guy - if you stopped fighting 24-year-old windmills and applied yourself fully to the facts we could really use you.

5. PF believed he was applying a correct procedure of stick back, apply TOGA and airbus protections especially alpha prot would prevent the bus from stalling with minimal height loss.

@CONF:
 

Hi CONF iture,


An *e-rudder* version is not equipped with a rudder travel limiter unit.
Since a RTLU is found with the VS, the F-GZCP was a *m-rudder* version.

Hi,

Interesting
Do you have any information about the change from 23 years ago :confused:
A historic of the change .. the new status ?
So far I do not find any change in the BEA organization along those 23 years...

Indeed it was only some "professional" call out on the beginning of the event AF447
From the PF
I have the conrols
Ignition start
From PNF
Alternate law protection
Wing anti-ice
The other CVR words .. are more like a discussion between Laurel and Hardy .. as I write sometime ago