AF447 Thread No. 3

[bearfoil]

promani

"Sorry but I consider that airline staff have an easy life."

I'll not argue that, but what is important is that this was a flight of 11? hours? The enemy is not SA, but the ennui that can degrade it. It would take Clarence Darrow to absolve this crew of the last bit of 'nonchalance'. Rest is more than being able to quickly recapture SA. It has to do with the time before and after the flight. There is no black, no white, I think, but shades of grey?

There is a larger topic in this, embracing more than the Airbus, Boeing, Bombardier, or other a/c. Being always ready takes almost as many calories as being in performance?

[peplum]

AoA indicator, as on Boeing would have save them.

Plane knowed it but was censured for pilots.
Investigators talk about it almost every line of report, post mortem.

But it has been censured for pilots. What an irony.

[DozyWannabe]

Bear: there is no reason to think the software was at fault in this instance is there? Necessarily limited perhaps, but isn't it more to do with the presentation of information which is at issue ?

Agreed, and I hope I'll be forgiven here for stating things more bluntly.

Allow me. A casual view of the history of the Airbus leaves a few undigested morsels. Question the electrics, and the software side gets indignant. Some flyers get indignant that the a/c seems "arrogant" (sic).

An airplane cannot be arrogant, and software cannot be defended when it is garbage.

After all this time, if there is a remotely valid question raised (There are), something is wrong with the approach.

The honeymoon was over long ago, and this airplane has worn long pants for years. To be able to get away with calling it a "work in progress" at this point is beyond absurd.

Training? Confidence? User friendly? Who gives a crap, Fix it.

Bear, I deliberately stepped back from this thread when I realised a few days ago that all I was doing by posting was repeating myself - and in doing so getting far more worked up than I should. So unless you have new information may I respectfully request that you consider the same?

Now, if you'll allow me to refer to your points:


No-one on the "software side" has become "indignant" in this thread. You have a few skilled electrical engineers (not all of whom are familiar with the system's design) positing theories, but that's about it.
Flyers are allowed to think what they like - and they seem to be about fairly divided on their opinions towards automation (though understandably some are a little short on the facts and some are unable/unwilling to understand certain aspects of it).
Sometimes they get the presence of automation confused with how some airlines are using that automation - and how it affects their jobs. Again, this is understandable, if sometimes a little frustrating
At no point has any piece of evidence been raised that points to a failure in the aircraft systems, over and above the loss of airspeed information. What little we have suggests that it was behaving as designed.


My personal opinion, for what it's worth, is that all this talk of control laws will turn out to be a red herring. What sounds complicated on paper is in fact not all that complicated. With all systems functioning, you are in Normal Law. When certain systems components fail, you are in Alternate Law. If basic flight data becomes unavailable, you are in Alternate Law 2 (which for the sake of argument should be thought of as Alternate Law without protections).

In Alternate Law 2 the pilots have complete control over all aspects of the aircraft, though you're commanding pitch and roll rate unlike in Direct Law which commands deflection. In short - the pilot is in charge and the computers are specifically programmed to do whatever the pilot asks.

Autoflight is already out, so the computers cannot command anything that the pilot is not already commanding. In this law, Autotrim will answer commands from the sidestick, if the sidestick remains deflected past the limit of elevator authority. In this aspect it is not unlike the old DLC system in the TriStar, which linked all flying surfaces to the controls to better stabilise the aircraft. Autotrim can be disabled in this mode simply by grabbing the trim wheel and moving it, just like in any other airliner - if this aspect is not being trained by airlines then it is a *serious* omission.

So - what we have so far is the aircraft's trajectory during the accident sequence, and a set of "point-in-time" status reports of what was going on and being said in the flight deck. Other than that we know *nothing* - even CONF iture is holding back on blaming the aircraft, which is almost unheard of (even if he is making up for that by bashing the BEA)!

Take out all this discussion over laws and automation and what you're left with is a crew over the ocean in the middle of the night (low circadian time and - perhaps even more importantly - no visible horizon or external reference) who suddenly find all airspeed information gone, a plethora of warnings they've got to figure out and a few minutes to make the correct choice. This is not the first time it's happened, and it's not the first time it's killed people.

Right, now back to radio silence on this thread for a bit...

@peplow - The ADI (artificial horizon) would have given them enough attitude information to work with - and even with a working AoA indicator, experienced pilots have failed to heed it in this situation.

[sensor_validation]

.... (I hope they did not try to swap seats or something like that. I doubt it - PF never handed over to PNF for the captain to swap in safely...

There may be more to come out on this - who took the controls in the last minute? An assumption made elsewhere is that it was the captain, presumably displacing the 2nd co-pilot PNF in the left seat.

[JD-EE]

bearfoil

"BEA know exactly what happened, and could explain it in layman's terms yesterday."

How right you are. If their reason for only releasing the limited info was to placate the media and stop leaks, I fear that the opposite will happen. I can't imaging Le Figaro et al sitting back and waiting for July.
I can see Euros being waved under the noses of those 'in the know'.
I wonder if mm43 can relocate to France to get some insider info, which he seems to be good at?http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/smile.gif

I'm not willing to say "BEA know(s) exactly what happened...." They may suspect it. But knowing what happened and why it happened requires careful analysis. What happened does not necessarily tell you why it happened and what corrective action must be taken. They are working with a vastly richer data set than before. But they do not know what the radar screen showed. That's not recorded (quality video uses IMMENSE bandwidths compared to FDR standards.) So there is still guesswork.

I hope they avoid the "quick solution" you and bearfoil seem to be implying we could have and instead drill down to the real factors that contributed to the crash. If fault is needed for some emotional reason get it right.

And be sure to accept that sometimes "stuff" just happens. If I had to apportion blame at this moment that is exactly what I'd blame. A situation that was "rumored" and "suggested by past events" struck this hapless plane with more force than any other plane that may have experienced it. After that crew reactions may have made a bad situation worse. And the cause for that seems to this SLF to be training, inexperience with real control of aircraft at that level, and basic primal human reactions.

What happened apportions blame. Why it happened discovers how it can be prevented, which is infinitely more important. If we never learn why 228 people went to a watery grave for nothing. And THAT would leave me furious - not that I as a person matter that much. The Internet does give some leverage here, though.

[Machinbird]

Call Captain X at three a.m. for a sim session, "now". Then throw a few nasties at him.
I think the unions would go berserk.... even if it might produce some "interesting" results.

When I think of what military pilots go through during military campaigns, lack of sleep and all that, I just wonder why commercial pilots are unable to perform their duties without rest periods and having to have a 'wake-up' time before resuming their assigned tasks. Just what do they do when they are off duty? Do they not sleep before going to work? Okay maybe I am ignorant of facts, and will hold my hands up if critized.
But I just wonder what public opinion would be if a doctor was woken up at three am and told one of his patients was 'crashing'. And he replied that he would have to wake himself up properly before he could give orders, so call back in fifteen minutes or so? Many doctors in ER work 24 hour shifts. But they do not have unions of course.
Sorry but I consider that airline staff have an easy life.

I have no wish to make fun of what airline crews have to do to earn a living. The following is for comparison only.

Short Sea Story.Combat operations.
Fly 2-3 flights per 12 hour Carrier flight cycle. During off cycle, there is a requirement for a 5 minute fighter alert. Each squadron assigns a crew for a 4 hour stint. There you are strapped in, switches set, but power off waiting for the call to launch. The back seater has enough time before he has to function that he can lie down on the wing. Yours truly could only unlock his shoulder harness, take off helmet-put on top of stick, take off kneeboard, put on top of helmet, put head on kneeboard and fall asleep. Meanwhile adjacent E-2 is doing a maintenance turn.
One thing I knew. No matter how clobbered the flight deck looked, they could clear a catapult and launch inside of 5 minutes. Next day, you were on the schedule for 2 more flights. I was very thankful that I wasn't actually called on for a night cat shot on 5 minute notice.
Sea story over.
Back to your regularly scheduled discussion.

[FE Hoppy]

@Dozy
Take out all this discussion over laws and automation and what you're left with is a crew over the ocean in the middle of the night (low circadian time) who suddenly find all airspeed information gone, a plethora of warnings they've got to figure out and a few minutes to make the correct choice. This is not the first time it's happened, and it's not the first time it's killed people.

I'm not sure how you know that they found all airspeed information gone. There is no indication in the report that the airspeed information was false at any point. Only that for a minute the standby didn't agree with the PFD. I also don't see and indication of a "plethora of warnings".

If you ignore all the previous speculations and just read the new report there isn't much wrong with the jet except an AP-AT disconnect in turbulence.

[peplum]

40° AoA, read a such value and i guaranty the guy would have push all his weight on the stick ..

[steamchicken]

I stand by post#1 here, posted nearly two years ago, and would repeat another post somewhere else that an easily accessible big button on this type of system is needed to enable direct control

Why? So they could pitch further nose-up?

[bearfoil]

Doze

"...Take out all this discussion over laws and automation and what you're left with is a crew over the ocean in the middle of the night (low circadian time) who suddenly find all airspeed information gone, a plethora of warnings they've got to figure out and a few minutes to make the correct choice. This is not the first time it's happened, and it's not the first time it's killed people..."

From three years ago, I have said pretty much the same thing, and after your last post I admitted to that very thing. The problem aisi, is the interface twixt a/c and PF's caress.

[JD-EE]

MurphyWasRight, sensor_validation's words led me to think "he" referred to the captain rather than PNF. But, I note further on in sensor_validation's remarks he says PNF was unhappy with what PF was doing, implying he was more alert than the PF.

I won't let you guys have it both ways.

[bratschewurst]

LYKA:

NTSB studies show weather to be a factor in about 25 percent of all U.S. flying accidents between 1994 and 2003. Khatwa said initial and recurrent flight crew training should cover fundamental concepts in six areas of weather-radar operation: beam coverage, Earth-curvature effects, antenna stabilization, tilt and gain management, calibrated weather and range. System limitations, such as attenuation and the significance of green radar “echoes” at high altitude, also should be covered.

These recommendations arise from analysis of pilots’ difficulties and concerns uncovered while Honeywell was developing its RDR-4000 radar. Khatwa’s study included a human-factors evaluation of flight-crew radar use, a global survey to assess pilots’ fundamental understanding and perceptions of training, and analyses of weather radar-related incidents and accidents. He concluded pilots did not understand fundamental weather-radar concepts; typical equipment use precluded detection of severe weather; and dedicated training was not standard practice.

Not clear if this applies to all operators. How much training is typical in an airline environment? Given the importance of avoiding CBs, substantive formal training would seem to be warranted.

Has anyone developed a radar simulator? By comparison with a full flight simulator, it would appear be quite cheap and simple to develop one.

[DozyWannabe]

I'm not sure how you know that they found all airspeed information gone. There is no indication in the report that the airspeed information was false at any point. Only that for a minute the standby didn't agree with the PFD. I also don't see and indication of a "plethora of warnings".

Hi.

From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS).
...
Note 2: Autopilot and auto-thrust remained disengaged for the rest of the flight.
At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]".

All of this is consistent with loss of speed information to the computers (and the flight deck instruments) due to iced-up pitot tubes, and it would appear that the PNF correctly diagnosed this in a little over 10 seconds. The plethora of warnings came after whatever caused the pitch-up and stall condition.

40° AoA, read a such value and i guaranty the guy would have push all his weight on the stick ..

Then why didn't the Birgenair Captain in his 757 do just that in the same situation? This is where the psychological/human factors aspect comes in to play.

From three years ago, I have said pretty much the same thing, and after your last post I admitted to that very thing. The problem aisi, is the interface twixt a/c and PF's caress.

And the point I'm making is that the aircraft is, by design, doing exactly as the pilot commands. At this point there is no "interface" as such - the computers are simply doing everything they can to pass the pilot's commands along to the control surfaces.

Anyway - I *really must* leave it there!

[bratschewurst]

DJ77:

With this in mind and noting that between 2 h 10 min 16 and 2 h 10 min 50 (citing the report) “The PF made nose-down control inputs”, I venture to submit that it is quite unclear what exactly caused the zoom climb to 37500 ft and this is a hint that BEA intends to closely examine this point.

Whether it was pilot induced or something else, this phase of the accident played a major role in establishing the confusion that followed.

The zoom climb and resulting loss of a/s and increase in AoA was the apparent cause of the stall, which the crew either didn't recognize or was unable to fly out of. So, after the loss of reliable a/s, it was essentially the proximate cause of the accident. And the report gives no real hints as to why the PF commanded nose-up. As the FDR didn't record the a/s displayed on the PF's display, it may, in the end, be unresolvable to a certainty.

Although it appears that this accident was a result of incorrect crew response to a UAS, that hardly absolves anyone else of responsibility. Airbus built a flight control system around critical flight data coming from instrumentation that proved, in the end, insufficiently redundant. Thales designed a pitot tube that, although meeting Airbus specs, proved far more prone to icing than did its competitors. AF did not appear to be sufficiently alarmed by previous instances of pitot icing to act to fix the problem with sufficient urgency. And, of course, the training provided to aircrews to deal with the situation proved inadequate.

Lots of blame to go around, based just on what's known so far. I do find it telling, though, that AF seems better at lining up the holes in the cheese than its competitors. That's not to say AF is unsafe; no major carrier is "unsafe" in comparison to competing modes of transport. But no other carrier has managed to have the first instance of hull loss in revenue service and/or loss of passenger life in four different aircraft types (Concorde, A320, A330, and A340.)

The French have managed superlative safety records in comparable high-tech enterprises (nuclear and high-speed rail in particular). AF appears an outlier in several ways.

[Diversification]

Hi!
I have been following these discussions on several forums for some years now.and learnt a lot. However, there are some unexplained, and unexpected, messages in the ACARS stream. Some of these seems to be ignored in the current discussion. Why? E.g. 2:11:55-.1/FLR/FR0906010210 27933406EFCS1 X2,EFCS2X,,,,,,FCPC2 (2CE2)/WRG:ADIRU1 BUS ADR1-2 TO FCPC2,HARD.
If WRG means wiring problems or signal problems it is a strange message from a healthy aircraft system.

[FE Hoppy]

From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS).
...
Note 2: Autopilot and auto-thrust remained disengaged for the rest of the flight.
At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]".
All of this is consistent with loss of speed information to the computers (and the flight deck instruments) due to iced-up pitot tubes, and it would appear that the PNF correctly diagnosed this in a little over 10 seconds. The plethora of warnings came after whatever caused the pitch-up and stall condition.


Wouldn't a "left nose up" command without any change in thrust cause airspeed to decrease?
For a stall warning to sound wouldn't the airspeed signal still need to be valid?
If with no increase in thrust and a nose up input after a stall warning sound along with a climb rate of up to 7000 ft/m cause the airspeed to rapidly fall?

I believe the correct position for the horse is in front of the cart not behind it.

[Machinbird]

JD-EE
MurphyWasRight, sensor_validation's words led me to think "he" referred to the captain rather than PNF. But, I note further on in sensor_validation's remarks he says PNF was unhappy with what PF was doing, implying he was more alert than the PF.

JD-EE and others.
Most of you may not recognize what sensor_validation is doing with his analysis, but if anyone is familiar with the communication analysis techniques of Sidney Dekker in (for example) "The Field Guide to Understanding Human Error" (a highly recommended read) they will recognize the process.

Sensor_validation gets a big attaboy:ok: for those initial efforts.
There is a lot that can be learned from this type of analysis process.

[mm43]

Originally posted by Diversification ...
... there are some unexplained, and unexpected, messages in the ACARS stream. Some of these seem to be ignored in the current discussion. Why? E.g. 2:11:55-.1/FLR/FR0906010210 27933406EFCS1 X2,EFCS2X,,,,,,FCPC2 (2CE2)/WRG:ADIRU1 BUS ADR1-2 TO FCPC2,HARD.What we are up against here, is that the BEA has provided a brief description of what happened, but not why. In that context the ACARS message you have mentioned is a "maintenance" message that is indicating a fault that occurred at 0210. It may be indicating something that is complicit in what was happening, or a by product. Svarin has spent some time trying to analyse what it was trying to tell us, but until the BEA have completed their investigation, the relationship to this accident and the above ACARS message will remain a mystery.

Having said that, I did mention it a few pages back in relation to what caused the initial upset.

[MurphyWasRight]

JD-EE:
MurphyWasRight, sensor_validation's words led me to think "he" referred to the captain rather than PNF. But, I note further on in sensor_validation's remarks he says PNF was unhappy with what PF was doing, implying he was more alert than the PF.

I won't let you guys have it both ways.


The only "fact" is that the PNF (recently asleep) was calling the Captain, whether he was seriously unhappy or just following protocol for any unusual situation is not mentioned in the report.

I would suspect it well could be both, however the point remains that he may not have been at the top of his game when things went wrong and thus less likely to be able and or willing to offer suggestions or intervene.

If I understand correctly he could have taken control at any point but did not utill much later.

----

As to Captain taking over the controls, not likely since his body was found, hence not strapped in.

[JD-EE]

DozyWannabe, all that's correct about loss of airspeed. However, I am an engineer and apparently so are the BEA people. They specifically noted the RHS is not recorded. So they never directly said all airspeed was lost. They could not sit down and directly prove it without "circumstantial evidence".

[DozyWannabe]

Wouldn't a "left nose up" command without any change in thrust cause airspeed to decrease?

Yes, but not by that much. We're not told how much deflection went into the "left nose up" input, nor are we told how long it was held.

For a stall warning to sound wouldn't the airspeed signal still need to be valid?

No, it's as much a function of AoA as anything (while the A330 doesn't have a specific indicator, it *does* have a vane sensor). Stall *protection* requires valid airspeed (which is why the degradation to Alt 2 law).

If with no increase in thrust and a nose up input after a stall warning sound along with a climb rate of up to 7000 ft/m cause the airspeed to rapidly fall?

Not by that much and not that quickly.

I believe the correct position for the horse is in front of the cart not behind it.

I believe that the BEA and Airbus considered the ACARS messages they received consistent with pitot icing. Is your supposition that this was not the case, and if so, what do you suppose it was?

JD-EE - see above.

(Damn, caught posting *again*!)

[mm43]

Originally posted by JD-EE ...
They could not sit down and directly prove it without "circumstantial evidence".They were dealing with the FDR and CVR, and it may well be that data will be available from the QAR. I doubt if we will know that until the next Interim Report.

[JD-EE]

MurphyWasRight - it looked like sensor_validation was drawing conclusions or making inferences beyond the bare facts that I didn't think were particularly valid for the very procedural and ritualized aspects of being in a cockpit - or even being a waiter going on break briefing his replacement.

[Machinbird]

Dozy
In Alternate Law 2 the pilots have complete control over all aspects of the aircraft, though you're commanding pitch and roll rate unlike in Direct Law which commands deflection. In short - the pilot is in charge and the computers are specifically programmed to do whatever the pilot asks.


I think you are missing a big aspect of the crew's control problem that night.

If the aircraft is right wing heavy, the aircraft will only fly straight with continuing left stick. How easy is it to separate the roll chanel from the pitch channel in this case? This aircraft was flying in Direct Law in roll.

Think about what this means to the lateral trim situation.!!!
NO Lateral Trim.
NO tendency to return to wings level. You must fly the roll angle full time.
Yes you have enough roll authority to level the wings.
You cannot let go of the stick-It will roll.
Do you see how a guy settling into this situation might apply nose up at the same time???

If not, do this experiment:
Place right arm on table in front of you. Point thumb up.
Put a stick in hand. Tilt stick to left.
With opposite hand, resist the attempt to tilt stick. Do you accidentally tilt stick toward you?? If not, apply more force until you have to cup stick in hand instead of with finger tips.
Get the idea?

[JD-EE]

Quoth DozyWannabe:
Quote:
If with no increase in thrust and a nose up input after a stall warning sound along with a climb rate of up to 7000 ft/m cause the airspeed to rapidly fall?
Not by that much and not that quickly.

OK, let's look at energy. Potential energy is mass times gravitational force times height, mgh. Kinetic energy is 1/2 the mass times the speed squared.

So we should be able to calculate speed lost from the height gained. "m" or mass is the same in both equations. So we can leave it out. The change in potential energy was m * 32 feet per second times 1500 feet. The change in kinetic energy must equal this. So 1/2 m dV^2 (delta-V squared) is 32*1500. Or dV^2 = 32*1500 or about 219 feet per second which is about 130 knots REAL speed. That needs to be converted to a change in kCAS and I'm not sure of that conversion. But it puts the plane's velocity change within the ballpark of what was shown.

Thanks for tweaking me into doing the rather simple math. They note no change in thrust took place. PF may have expected, for whatever reason, CLB thrust to be asserted. This might be because he moved the stick before the stall warning was played.

[Bigdave599]

Although not an airline pilot, I have read every post on this thread. There are a couple of things as yet unexplained:
1) there seems to be an assumption that the first (2) stall warnings (just after 2h 10m 05) were spurious, possibly related to the IAS error. Firstly, there is nothing in the BEA statement to suggest they were spurious; and secondly, as the stall warner is fed from the AOA indicators and not the pitots, the IAS error would surely not cause a stall warning
2) the "storm climb" at 7000fpm for 2500 feet is not explained. The PF made "a left nose-up input" not, as he is later stated to be making, "sustained" nose-up input. And there is nothing in the text to suggest that he pitched the aircraft up to the extent needed to climb at this rate on cruise power settings - surely that would have required 20-30 degree pitch angles that would surely have been mentioned? There is also a mention of nose-down inputs in this phase

On the other hand, a big updraft would both lift the aircraft without big pitch-up, and cause the AOA to increase, perhaps setting off the stall warner?

Where this leaves the explanation of the crash I don't know, but we do not yet seem to have satisfactorily explained this first 45 seconds.

[MountainWest]

Excellent example with the stick! That clarified much of the difficulty I was having in understanding the continual trim up. That, combined with the sudden mixed rules of operation in different stick axes . . . in a crisis . . . what a recipe for disaster.

[mm43]

Back in post #260 I made some assumptions about the THS and the AoA. The basic post is repeated below with a small addendum and should be self explanatory.
At 2 h 12 min 02, the PF said "I don’t have any more indications", and the PNF said "we have
no valid indications". At that moment, the thrust levers were in the IDLE detent and the
engines’ N1’s were at 55% the angle of attack decreased, the speeds became valid again and the
stall warning sounded again.My interpretation is that the aircraft was in a well established stall (deep stall?) and passing through FL250 with RoD about 10,000 feet/min, and even though both engines N1's were 55%, the pitch-down inputs decreased the AoA and the airspeed data became valid. However, that IAS was low and the stall warning activated again but ceased with further pitch-up commands as the data again became invalid.

Without AoA information, neither pilot had any idea in what part of the stall regime they were, and seemed to react as if a return of the SW was indicating Vmo, hence the continuing pitch-up command. So failure at this time to persist with the pitch-down command effectively left them doomed, as even then with the time taken for the THS to readjust (if it was going to**) and for the wings to start flying, meant that the chance of reducing the RoD to zero before FL0 was marginal.

It strikes me that no-one on the flight deck realized that the AoA data was only valid when IAS was greater than 60KTS. Even though they went looking for the FPV, it seems it was only after the SW stopped at 2:11:40 plus a few seconds, and therefore to no avail - see ACARS FPV messages timed 0212z. Their final chance to grab the FPV page was missed shortly after 2:12:02 when the stall warning sounded again - meaning valid airspeed!

** The THS question?? As IAS had gone below 60KTS, the aircraft was no longer in Alternative 2 Law, but was now in Abnormal Law which means that the THS must be manually trimmed. Even so, in the description given above, I believe that with the low airspeed the elevator was still capable of making an attitude change, provided it received a nose-down command.

[FE Hoppy]

Note: When the measured speeds are below 60 kt, the measured angle of attack values are considered invalid and are not taken into account by the systems. When they are below 30 kt, the speed values themselves are considered invalid.

This note from the report links the vane angle signals to the validity of the airspeed.

Later when the nose is lowered and airspeed increases back to above 60kts the stall warning sounds again. The pilot responds by pulling and the warning stops as the airspeed drops below the lower limit.

So while we cannot say what caused the airspeed to drop we do know that it happened after the nose up command and after the stall warning.

We also know that the pitch attitude increased to 10° and the aircraft began to climb.

We also know that after the first mention of nose down input the VS dropped from 7000f/m to 700f/m and the airspeed increased sharply to 215kts by which time the aircraft had climbed 2500ft

The first mention of thrust increase is after this initial climb after a further stall warning.

If I bunt at the top of a zoom climb but fail to increase thrust will this cause a stall warning as the g reloads after the bunt?

I'm not discounting anything but I'm not adding information that isn't described in the record of events described in the report.

[DozyWannabe]

If the aircraft is right wing heavy, the aircraft will only fly straight with continuing left stick. How easy is it to separate the roll chanel from the pitch channel in this case? This aircraft was flying in Direct Law in roll.

Think about what this means to the lateral trim situation.!!!
NO Lateral Trim.
NO tendency to return to wings level. You must fly the roll angle full time.
Yes you have enough roll authority to level the wings.
You cannot let go of the stick-It will roll.
Do you see how a guy settling into this situation might apply nose up at the same time???

If not, do this experiment:
Place right arm on table in front of you. Point thumb up.
Put a stick in hand. Tilt stick to left.
With opposite hand, resist the attempt to tilt stick. Do you accidentally tilt stick toward you?? If not, apply more force until you have to cup stick in hand instead of with finger tips.
Get the idea?

All fair points.

Firstly, was the aircraft right-wing heavy?

Secondly, I can see how it would be a handful, but the force we're talking about here is not an accidental tweak in the wrong direction. To get the THS up to 13 degrees requires full back pressure for several seconds. This is the problem that is not going to be solved until at least an interim report is out, and anything we suggest is ultimately pointless.

Thirdly, I couldn't get your experiment to work - would the fact that I am left-handed be a problem there?

[Machinbird]

Thirdly, I couldn't get your experiment to work - would the fact that I am left-handed be a problem there?
Try the mirror image experiment.
The idea is that to exert force toward the body's center, you are probably going to use the wrist joint to do this if the thumb is pointed up.

[FE Hoppy]

Secondly, I can see how it would be a handful, but the force we're talking about here is not an accidental tweak in the wrong direction. To get the THS up to 13 degrees requires full back pressure for several seconds. This is the problem that is not going to be solved until at least an interim report is out, and anything we suggest is ultimately pointless.

The THS movement was in response to the sustained nose up input as described here:

At 2 h 10 min 51, the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight.

[bearfoil]

Bigdave599

The initial storm climb
Although not an airline pilot, I have read every post on this thread. There are a couple of things as yet unexplained:
1) there seems to be an assumption that the first (2) stall warnings (just after 2h 10m 05) were spurious, possibly related to the IAS error. Firstly, there is nothing in the BEA statement to suggest they were spurious; and secondly, as the stall warner is fed from the AOA indicators and not the pitots, the IAS error would surely not cause a stall warning
2) the "storm climb" at 7000fpm for 2500 feet is not explained. The PF made "a left nose-up input" not, as he is later stated to be making, "sustained" nose-up input. And there is nothing in the text to suggest that he pitched the aircraft up to the extent needed to climb at this rate on cruise power settings - surely that would have required 20-30 degree pitch angles that would surely have been mentioned? There is also a mention of nose-down inputs in this phase

On the other hand, a big updraft would both lift the aircraft without big pitch-up, and cause the AOA to increase, perhaps setting off the stall warner?

Where this leaves the explanation of the crash I don't know, but we do not yet seem to have satisfactorily explained this first 45 seconds.

The time frame from 15 seconds prior to, and 30 seconds after a/p drop are the focus. The rest is marbles and chalk. In your post is a gob of important thought.

Short some one who is bilingual and conversant with Physics and aero, the majority of 'aha' is here. Energy( including ambient), Flight Path, and Input by both a/c and PF.

[BarbiesBoyfriend]

I'm not 'anti airbus' - I've never flown one. But...

It strikes me that the bus flies quite unlike other aircraft even when everythings working as it should, which is practically always. I'm talking about the way it processes roll and pitch inputs, with the a/c staying rolled or pitched when pilot input ceases.

But when the autos have gone off-line and instruments have stopped indicating normally, its behaviour is going to change more than a non-airbus would. ie it changes back into what a non-airbus would be like with the same failures.

Someone mentioned having to roll the wing level by hand. The pilot of a non-airbus would not be surprised at suddenly having to do this. An airbus pilot, with probably very small actual 'stick time' (never mind stick time in IMC on partial panel) would probably be very surprised to fiind that his 'bus had stopped helping him in this way.
Also, unless given the chance to practice in this degraded flight condition, is it really surprising the pilots struggled?

The trouble with these autos is that the better they get, the more confused you are when they fail.

All I'm saying is that a highly automated Airbus makes a pilot highly dependant on its autoflight system and 'easy handling'.

Maybe a bit too dependant.

[sensor_validation]

JD-EE

JD-EE and others.
Most of you may not recognize what sensor_validation is doing with his analysis, but if anyone is familiar with the communication analysis techniques of Sidney Dekker in (for example) "The Field Guide to Understanding Human Error" (a highly recommended read) they will recognize the process.

Sensor_validation gets a big attaboy:ok: for those initial efforts.
There is a lot that can be learned from this type of analysis process.

Gotta go and read that ref now - but we are just given a glimpse into the mindset of the the BEA investigators who can't say what they are not certain about, or AF / AB could object to - but sure they will by now have more potentially controversial 'facts' and theories. I hope they can recreate what speed indication was on the RHS display.

On consulting mon interprète there's little doubt "réveille" means "wake", but perhaps there's nothing in the captain "assiste" rather than just "attend" the handover, and the PNF "éventuellement" translated to "maybe" could have been "possibly" and not be passive in context - but why did BEA highlight that but not whose decision to reduce speed. Maybe they wanted to make the point he was fresh and alert after "power napping"?

By the way - if you study the A340 airprox Appendix B zoom climb it appears (as has been pointed out before in this thread) pitch-down commands are plotted as positive which is somewhat counter-intuitive isn't it?

[Machinbird]

Firstly, was the aircraft right-wing heavy?

Circumstantial evidence only at this point. All turns were made to the right following the initial problem. We will have to wait for BEA to confirm.


Secondly, I can see how it would be a handful, but the force we're talking about here is not an accidental tweak in the wrong direction. To get the THS up to 13 degrees requires full back pressure for several seconds. This is the problem that is not going to be solved until at least an interim report is out, and anything we suggest is ultimately pointless.

Pointless? Not necessarily. Once we have an idea of how this might have happened, we can explore other implications. The number of pathways we have to explore are far fewer than before AF447 was found.
It takes a while for the light to come on with some regarding what the crew faced. The more lights that come on, the easier it is to discuss other factors. At the moment, it seems no one on the thread is volunteering any of their experiences with the ALT2 flight control law. Or maybe they only did it with the aircraft in lateral trim (due to a kind simulator instructor) Maybe no one trained for it with lateral imbalance. That would be significant.

[L337]

a big updraft would both lift the aircraft without big pitch-up, and cause the AOA to increase

AoA would decrease.

[forget]

L337. Other poster's correct. Increase.

[atakacs]

Folks

May I point you to this Spiegel (http://www.spiegel.de/international/world/0,1518,765764-2,00.html) online article with the following

The BEA report, in its current form, only provides the angle of the stabilizer but provides no explanation as to why. The report merely indicates that it was at this moment that Captain Marc Dubois re-entered the cockpit.

Exactly what orders he issued are not part of last Friday's report. But sources close to the investigation are saying that he said: "This is a stall. Reduce power and nose down!"

I have no idea about the veracity of this quote but I would tend to say that this is generally a serious publication. If confirmed this would obviously paint a very different picture.

[DozyWannabe]

It strikes me that the bus flies quite unlike other aircraft even when everythings working as it should, which is practically always. I'm talking about the way it processes roll and pitch inputs, with the a/c staying rolled or pitched when pilot input ceases.

I distinctly remember when doing my AEF in a Chipmunk that moving the stick to the left would put me in a left turn and returning it to neutral would hold me at that angle of bank. How is a FBW Airbus in Alt2 or Direct Law any different? You're not positioned as precisely as you would be in Normal Law, and the computers can't hold you there if you're being buffeted - but that's a pretty basic flying skill surely? Isn't that what recurrent training is for?

[HarryMann]

a big updraft would both lift the aircraft without big pitch-up, and cause the AOA to increase AoA would decrease.

How's that then ?

[gums]

Well, well, well.

As someone asked the 'bus drivers some posts ago, how many realized that AoA was considered invalid if airspeed below 60 knots? Oh!!! Sheesh, the airspeed is deemed invalid. What now, kemo sabe? Where's my AoA "protection"? Oh! There it is again, but I am stalling and maybe getting a speed warning. I am confused.

So "attaboy" to mm43 and Hoppy.

I then ask all to look at the "reversion" sequences in the manual and all the "protections" lost at each stage. Having trouble with capturing the page, so check back later or look at previous ref by 'bird, et al.

To Doze:

We luv ya, man.

I want you to code my next hypersonic space vehicle's flight control system and guarantee the system will work exactly as SPECIFIED, not DESIGNED. Jez kidding, and I feel your pain ( not really, but we're in the stag bar now and I can be honest, heh heh).

Jocularity aside.

The concern over weather seems overdone. From the BEA report, it appears climbs and dives were not done with fairly level flight attitudes as we would see in a severe updraft/downdraft or mountain wave or microburst. They seem to be directly related to pitch attitude and later, a flight path vector in a fully-developed stall. Sorry, but that's my story, and I'm stickin' to it.

Secondly, unlike several here who wish to have a "conventional" control mode, I can't see it. Even in the older jets there are dampers and limiters on the control deflections and deflection rates. Some are based on dynamic pressure, some on body rates. Last jet I flew with zero of those was in 1971. So the best I can see is a FBW backup mode that emulates the older jets we are used to as the Boeings and original Airbus.

And we don't have it!!

My biggest problem with the laws for the FBW 'bus is they try too hard to "protect" basic attitude and roll angle without emphasizing AoA. Then there are all those connections with the autopilot. I really like some of the law changes in "TOGA", wow, couldn't go around without all those, huh?

On the good side, the gee command for pitch is really neat ( versus AoA command like a normal plane), and allows for the so-called autotrim. Actually, all it does is maintain 1 gee, even in a bank up to certain limits. My jet didn't do that, so we needed to click back a notch of trim in a turn. Big deal.

On the bad side, a reliable backup law for the 'bus might consider primarily the gee and AoA for limits, while still applying body rates and maybe "standby gains' for dynamic pressure, and allow airspeed to take a lesser role ( especially unreliable airspeed).

I see far too many "notes' in the manual and combinations of failure modes that are not clearly explained unless you read all the fine print.

[JD-EE]

L337 - perhaps I need some clarification. If the air flow vector at the front of the plane changes from horizontal towards the tail into something with a vertical upwards component towards the tail and upwards would that not look to the plane as if it had just had its nose planted upwards at a higher angle of attack?

[HazelNuts39]

To get the THS up to 13 degrees requires full back pressure for several seconds. Are you sure? The BEA Update says after 2:10:51: The trimmable horizontal stabilizer (THS) passes from 3 to 13 degrees nose-up in about 1 minute ...I believe to have read somewhere that full back pressure demands 1.5 g. I further believe that the 7000 ft/min was reached after approx. 20 - 25 seconds, which would correspond to 1.2 g or less, i.e. 40% of stick travel. Stand to be corrected, of course.

[gatbusdriver]

When stationary the AoA vane, which is pivoted, will be at an angle to the ground. The vane requires airflow over it to give accurate readings, I would therefore humbly suggest that the actual airspeed required for an accurate reading is 60kts.

[JD-EE]

HN39: At 2 h 10 min 51, the stall warning was triggered again. The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs. The recorded angle of attack, of around 6 degrees at the triggering of the stall warning, continued to increase. The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight.The PF maintained nose-up inputs. So the question is whether a nose-up input not to the wall will activate autotrim or not. I suspect it will simply because the ride for the SLF would be kind of rough if autotrim only responded to a full forward or backwards stick motion.

In that case maintaining the nose-up stick input will bring THS upwards to its limits over time.

[Garrison]

L337
Quote:
Originally Posted by L337
Quote:
a big updraft would both lift the aircraft without big pitch-up, and cause the AOA to increase
AoA would decrease.
How's that then ?

An updraft would initially increase the angle of attack, and the airplane, being statically stable (one hopes) would react by pitching down in order to regain its trimmed angle of attack. What happens next depends on whether the pilot (or autopilot) attempts to hold altitude against the updraft. It is not correct, however, that an updraft ipso facto would decrease the airplane's angle of attack.

WRT the Spiegel article, the leak regarding the pilot's statement is extremely interesting, and it is hard to see why BEA would have withheld it from the interim report. Some statements in the article are incorrect, however, for instance the claim that the pax were held in their seats only by their seatbelts. At a steady rate of descent, the pax would experience 1 G.

It is unlikely that a recovery could have been made without manually trimming the THS. At high alpha the elevator is not very powerful compared with the stabilizer. That this was not done suggests that the crew were not aware of the -13 degree THS setting. Doesn't it seem unlikely that if they were aware of it, and had identified the stall, they would have been deterred from using it by their simulator training? They were about to die. Or did I overlook something in the report?

[DozyWannabe]

JD-EE : I have it on good authority that it does. If the limit of elevator authority is reached and the pilot is still commanding full back-stick, then autotrim will move the THS to comply with what is being asked.

[Gringobr]

As a professional translator, assiste in Portuguese means to watch, as in watch TV, watch a football game etc.
I am almost 99% sure it is the same in French
It does not mean help or actually assist in any way

[Mr Optimistic]

Just a little more of the CVR would help ! Presumably the CVR will show what the intent was and for some reason, legal or otherwise, someone is uncomfortable with divulging too much information. Doesn't it rather look like the initial climb was intentional: perhaps to get out of an bad icing level (with the storm below being unwelcoming) ?

[Machinbird]

Gatbusdriver
When stationary the AoA vane, which is pivoted, will be at an angle to the ground. The vane requires airflow over it to give accurate readings, I would therefore humbly suggest that the actual airspeed required for an accurate reading is 60kts.

Gatbusdriver, welcome to the fray. During your training, have you flown in ALT 2 law, or are you on the little Airbus? We are drafting all able bodied bus drivers to try to answer this question.

My personal experience with the USNavy peg, cone and vane type AOA sensors is that they would come alive in a definite breeze, perhaps 10 knots. A vane type that needed 60 knots to be reliable would be a sticky one in my book.

[spagiola]

WRT the Spiegel article ... Some statements in the article are incorrect, however, for instance the claim that the pax were held in their seats only by their seatbelts. At a steady rate of descent, the pax would experience 1 G.

True -- once the rate of descent stabilized at some -10000fpm. But shortly before that, they'd actually been climbing, so at some point there was a heck of a vertical acceleration, and for that period the description would likely hold true.

I can only hope that that moment passed quickly, because it must have been terrifying.

[Mr Optimistic]

Well if gaining vertical speed the seat will push beyong 1g to accelerate the Pax. When the vertical acceleration becomes negative the seat will push up at less than 1g. If the vertical acceleration exceeds 1g down, and only then, will Pax leave their seats and be pushed down by the seatbelt.

[Garrison]

In French assister means to witness or be present at an event.

[Machinbird]

In referring to the Speigel article.
Hüttig is not without bias in that he provides technical assistance to the victim's families and thus probably has economic interests at play.

The description of the conditions inside the aircraft on the way down are a bit overblown. Although the nose did get pretty high in the air, the maneuvers suggest that cabin environment was close to 1 g. Probably more unsettling would have been the wing drops that the aircraft experienced. Not so bad as a roller coaster ride though.

Biggest fault with the Spiegel article is that the aircraft was "doomed" when the trim ran up to 13 degrees. If the crew had run it back down to near normal, this long thread would probably not exist and there would likely not exist a victim's family group.

There are a lot of training issues sticking out of this mess, and not all of them appear to have originated with AF.

[takata]

In French assister means to witness or be present at an event.
The meaning of assister is related to context.
1. être présent (participer) = to be present at something
2. aider (seconder, secourir, concourir, dépanner) = to help someone.
Where it is quoted from?

[Garrison]

"Entre 1 h 59 min 32 et 2 h 01 min 46, le commandant de bord assiste au briefing entre les deux copilotes..."

from the BEA interim report

[sensor_validation]

The meaning of assister is related to context.
1. être présent (participer) = to be present at something
2. aider (seconder, secourir, concourir, dépanner) = to help someone.
Where it is quoted from?

The comment in the BEA statement which was translated into English as "the Captain attended the briefing between the two co-pilots" - maybe trying to read too much into the wording - would expect the Captain to lead the briefing? As JD-EE pointed out above maybe this statement just confirms there was a formal handover as required, nothing more.

[glad rag]

rubbish, but, I will persist none the less

Absolutely. :D

[Garrison]

Machinbird:
Biggest fault with the Spiegel article is that the aircraft was "doomed" when the trim ran up to 13 degrees. If the crew had run it back down to near normal, this long thread would probably not exist and there would likely not exist a victim's family group.

Agree entirely. If it's true about the Captain recognizing that the airplane was stalled, then everything comes down to that trim wheel -- unless, of course, the A330 turns out to have an unrecoverable deep stall mode, which I very much doubt. But if he said that as reported by Spiegel, why did the PF not react with an AND command? Oh, maybe that's where the AND command does occur -- but is aborted because of the stall warning. What a mess!

[Capn Bloggs]

The vane requires airflow over it to give accurate readings,
Does it? How about a system where if it is not giving a reading within 16°AoA, it signals a stall? Say it is pointing "to the ground" whilst the aircraft is airborne. What do you reckon the crew needs to know? That aircraft isn't flying ie it's stalled. It doesn't matter where the vane is actually pointing.

But in this case, just when the crew needed the most "reminding" (and who would have not been confused: VSI off the clock going down, but with speed tapes on nothing, "knowing" that only a couple of minutes before they were giving duff gen), the stall warning silenced. Had it kept screaming at them, maybe their confusion would have eventually been overcome and one of them would have stuffed the nose down to recover the thing.

[sensor_validation]

...
My personal experience with the USNavy peg, cone and vane type AOA sensors is that they would come alive in a definite breeze, perhaps 10 knots. A vane type that needed 60 knots to be reliable would be a sticky one in my book.

For lots of detail on the AoA vanes see the Perpignan crash report. The vane may indeed generate a "local angle of attack" but "As the fuselage disturbs the flow of air, these measurements
have to be corrected to obtain the aeroplane angle of attack." I wonder if its the compensations that limit the use at lower speed, but then where does the speed come from?

[milsabords]

Garrison: Oh, maybe that's where the AND command does occur -- but is aborted because of the stall warning. What a mess!

This does not look like good logic: if they have evidence that the ac is stalled while there is no stall warning, they should ignore it when it sounds again.

[falcor]

I previously asked the following questions:

If/when the plane kicked into Abnormal Law, what warning or message would have been visible or audible to the pilots?
Why was there an ACARS message about the transition to Alternate Law, but no ACARS message about any other change in Law (e.g. Abnormal or Direct)?

mm43 directed me to A340 / A330 Control: flight & laws (http://countjustonce.com/a330/a330-flight-laws.html)
but having read through that, I must be blind because I don't see the answers to my questions!

It seems that whether or not the plane was in Abnormal Law (and hence had no autotrim - making the THS "frozen" at 13 degrees unless manually adjusted) is important in understanding whether the pilots had a chance of pulling out of the stall once they started putting the nose down (after the captain returned to the cockpit).

So far, it sounds like we are inferring that it was in Abnormal Law, owing to the AoA and speed crossing the specified thresholds, but can this be shown explicitly through a message or recording? And if not, why not? It may be an important point, so it would be nice to have certainty. There appears to be no ACARS message about any law other than Alternate - does that mean that Abnormal Law doesn't generate an ACARS message...?

The other question, which some others have touched on, is whether the pilots knew they were in manual trim mode. From the "flight & laws" link above, if in Direct Law the pilots will see "USE MAN PITCH TRIM" on the PFD. Is that also the case in Abnormal Law (it doesn't explicitly say in that link)?

[MurphyWasRight]

Sensor validation:

For lots of detail on the AoA vanes see the Perpignan crash report. The vane may indeed generate a "local angle of attack" but "As the fuselage disturbs the flow of air, these measurements
have to be corrected to obtain the aeroplane angle of attack." I wonder if its the compensations that limit the use at lower speed, but then where does the speed come from?

Th 60KT limit may also be an almost arbitrary "safe" limit withe the rational that if airspeed is that low you are not flying anyway?
This would also help eliminate spurios alarms durinfg landing.

[takata]

The comment in the BEA statement which was translated into English as "the Captain attended the briefing between the two co-pilots" - maybe trying to read too much into the wording - would expect the Captain to lead the briefing? As JD-EE pointed out above maybe this statement just confirms there was a formal handover as required, nothing more.
Right. In this context, "assister" only means that he was present during the briefing. He could have either contributed to it or remained totally passive, it doesn't tell it.

You guys are again focusing on press "leaks" which doesn't look more "informed" than all the previous ones. The statement that FO2 (Pierre-Cédric Bonin) was the PF is clearly doubtful.

[HarryMann]

Why is there all this talk about being "locked in" a "super stall"? If the stick had been held forward and the trim wheel rolled AND and the plane had failed to recover, this would make sense; but none of that happened.

I've got to say Garrison, I feel that's likely true.... especially if less than TOGA thrust was also selected.

It is a very remote possibility I suppose, that the PF was under 'some impression', at a base response level, that recovery from a stalled condition does not require a consistent and nose-down pitch .

If so, it's highly unlikely that Captain M. Dubois would have followed that course of action, and must have realised having made his way to the cabin, pretty well what sort of situation they were in, irrespective of instrumentation

[bearfoil]

howdy. PF gets Stall Warnings; a warning is not the same as the real deal.
His training (prior to AB "Stall Warning Recovery" "modification") was to fly through the warning losing little if any altitude and use power to accelerate.

A warning given at the break would not be a warning, it would be an annunciation. Having never experienced a full stall, he would likely not anticipate it by definiton, as he has had no training how to recover it, so all that would happen is an unanchored 'anxiety'. In other words, one flaw in "Display" is a gotcha without recourse. Not very nice, Miss.

[Tailspin Turtle]

I have thought from the beginning that a deep stall was very unlikely, but it appears that the pilot flying managed to unknowingly stabilize the airplane in a very similar flight condition. I don't know why he changed from a perfectly good pitch and power setting to get so slow, but at that low a speed, the engines were probably providing a goodly amount of nose-up pitch (along with the stabilizer trim automatically coming in to "help" him keep the nose up) so the normal pitch down occurring at stall might not be evident. Other than airspeed, which he has reason not to trust; angle of attack, which isn't displayed?; and an aural stall warning, which is apparently inhibited, how else does he know that he's stalled? What he knows is he has the throttles pushed up, the airplane pitched to 15 degrees or thereabouts (16.5 degrees) which is a familiar number for powering out of a problem, and his rate of descent is at the bottom of the tape and the altimeter is a blur, both high-order attention getters. Who among us wouldn't be confused as to why the airplane was descending instead of climbing and desperately pulling back on the stick to make it climb like it always has before?

[bearfoil]

So his forward stick and decrease in AoA may have gotten him on the way to recovery, but do we know the decrease in AoA was not just the a/c dropping her nose after stalling?

If the Captain did re-enter and shout, or command, likely it would have been something along the lines that precipitated a "just about" recovery.

You know, this discussion, read with patience, will eventually get to within 90 per cent of the actuals.

[mm43]

Other than airspeed, which he has reason not to trust; angle of attack, which isn't displayed?; and an aural stall warning, which is apparently inhibited, how else does he know that he's stalled? That is the bit that seems to have got them totally confused.

The AoA vane plus IAS provides the stall warning. Only problem is that the IAS must be greater than 60KTS for the combo to provide the SW. The SW stopped because the IAS had dropped too low, and when they attempted nose-down and got an IAS over 60KTS, the SW started again.

Their logic told them it was the wrong thing to do, hence the persistence with nose-up on the side-stick. I wonder if the actual AoA had been available, what they would have made of it?

[beachbunny]

It's reasonably simple, actually.

The stall warning system would only work within a specific range of parameters.
( An educated guess here)

The aircraft went though the range, to the "other side", ie excessive AoA, low fwd speed. When the pilot tried applying nose down, the a/c would have re-entered the operative range, hence the stall warning sounding again. Proves he was moving in the right direction, be it elevator input, or THS, (except that it sounds like the THS had not started to wind back the other way, before the ND was discontinued)
Had the ND input continued, the rollover would have continued, (with the stall warning still sounding,) until AoA reached or passed through, the "onset" parameter. We now have control.

[mm43]

... sounds like the THS had not started to wind back the other way, before the ND was discontinuedThat's the next problem! Once the IAS has dropped below 60KTS, the aircraft is in Abnormal Law and the THS must be adjusted manually.

[takata]

That's the next problem! Once the IAS has dropped below 60KTS, the aircraft is in Abnormal Law and the THS must be adjusted manually.
Or that their AoA exceeded 30 deg (same effect = abnormal Law).
Reduce AoA, airspeed will increase, she will return to Alternate Law and the auto-trim will work again.

[matthewsjl]

From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS).

At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]".

The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs. The vertical speed, which had reached 7,000 ft/min, dropped to 700 ft/min and the roll varied between 12 degrees right and 10 degrees left. The speed displayed on the left side increased sharply to 215 kt (Mach 0.68). The airplane was then at an altitude of about 37,500 ft and the recorded angle of attack was around 4 degrees.


My read of the above is that the plane was flying fine when the autopilot/thrust kicked out due to unrelaible airspeed. No power changes are mentioned by the BEA so the thrust required for level flight at FL350 and 0.8 must have been set and being produced. The initial control input is nose up (and left roll) and a climb begins. The plane isn't stalled at this point as a) it's capable of a climb and b) the BEA confirms that the last 3m30s were in a stalled condition which puts the start of the stall at about 2h11m (the stall warn triggers again at 2h10m51s). There are some nose-down inputs mentioned at this point and it seemingly controls the climb but is still probably in a climb (and bleeding airspeed) due to the pitch and VS indicating +700ft/min.

It appears that there was a trade of speed for altitude but no actual stall until 2h11m.

Once the stall begins, all BEA references are to nose-up up inputs and the THS rolls to full nose-up. Some references to nose-down are made later but as others have commented, with full nose-up THS it's a good question how recovery would be made at that point.

[Shadoko]

Hi,

Is this "Abnormal Law" dispatched for the PF?
Doesn't be curious BEA note doesn't not mention this?

One more question:
From 2 h 10 min 05, the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row. The recorded parameters show a sharp fall from about 275 kt to 60 kt in the speed displayed on the left primary flight display (PFD), then a few moments later in the speed displayed on the integrated standby instrument system (ISIS). Why ISIS speed display goes down? Isn'it inertial? I don't understand how they can truly loose all that speed before ascending.

[JD-EE]

mm43, if it got them totally confused it's a software specification design problem. If the airspeed is less than 60kts, suddenly and the plane is 10k feet above ground for the plane's estimated location it's "obviously" stalled. It cannot fly that slow. So why isn't it continuously telling the pilot he IS stalled? (None of this about to stall warning nonsense.)

Methinks the damn good system software for the A330-200 can be improved, as can all software. And this is one good improvement. Enshrine the knowledge early so that when we DO get to autonomous SLF carriers this is one fewer problem the aircraft will face. (The communications problems should be covered as well with a "guaranteed" work around.)

[galaxy flyer]

All indications of AIRSPEED are based on air passing into the pitot tubes, processed by ADIRUs for output to the PFD or ISIS. Inertial is not used, and not usable, for airspeed.

One is not "dispatched" in alternate or abnormal law.

[NWR]

BEA knows exactly what the PF and PNF thought happened.

'At around ' 2h11min40 (why say 'around'?) the 'Captain re-entered the cockpit'

Hard to imagine him saying other than "What happened?"
And the PF and PNF will tell him and us what they perceived and their actions.

Mind you
The background stall noise on the CVR will be sounding like 0m55sec into this Tarom ROT381 AB incident:
YouTube - ‪Tarom Inccident a/c YR-LCA ROT381 Airbus 310-325 (Paris, Orly) 3D Flight Reconstruction‬‏
perhaps it said 'At around ' because only then did he speak

[JD-EE]

matthewsjl, let's add one more "fact" to your discussion, The 60kt drop in speed is very close to what calculations show the plane would lose simply trading horizontal velocity for altitude with very high efficiency.

That's a good argument for there not being an updraft. And 215kt at FL375 is almost certainly qualifying as a legitimate stall, especially considering the angle of attack registered. (That's if I've read graphs right.)

[jcjeant]

Hi,

As many commented here ... the CVR transcript is not the complete one.
On the other hand ... Air France (in a press release statement) tell they were proud of the professionalism of the crew .. it's certainly for some reasons.
Sure Air France had access to the complete CVR transcript or sound version.
So I'm in the waiting of the words of the captain (no one word of the captain after the upset in the actual BEA release)

[CONF iture]

I'm not sure if the MAC noted 29% in the note is not a typo for "around 39%". When looking at the "target CG" as it should be computed by the fuel-computer (FCMC) for a 205 tonnes ground weight aircraft, it will give a MAC around 37.75% (target). Hence, it should vary in this part of the flight between 37.25% and 37.75% (while maximum certified AFT should be above 39.75% with a 2% safe margin).

To me, 29% makes more sense than the 37% as initially estimated by the BEA in their interim report #1
Due to the heavy cargo load, it is probable that the fwd cargo hold was also fully loaded, which explain the fwd CG of 23% at take off. Considering the initial fuel distribution, the trim tank had normally 2400kg at take off time.
During the climb, an additional 2400kg was transfered to the tail for a total of 4800kg which was still there at the time of the event.

The 37% target is an ideal that can be reached only if the initial loading would allow it.

The CG was pretty much centered, at least it was not especially aft.

[CONF iture]

Sure Air France had access to the complete CVR transcript or sound version
At the present time, who has, or momentarily had, access to the full or partial data ?

some people at the BEA
then who ... ?

[grizzled]

CONF...

Here is a link to ICAO Annex 13. If you look at Chapter 5, specifically sections 5-3 to 5-5, you'll find the criteria for who can be, who should be, and who must be part of the investigation, including who can have access to all or part of the investigation material.

http://www.airsafety.com.au/trinvbil/C619icao.pdf

[jcjeant]

Hi,

Here is a link to ICAO Annex 13It's just for the organization between states ..... it's not realy instructive about who have really access to the data .... IMHO

[mm43]

JD-EE
if it got them totally confused it's a software specification design problem.Undoubtedly! It would appear that no-one anticipated an approach to a stall that wouldn't under normal circumstances be dealt with correctly. In this case it wasn't, and degradation of air-data was such that the SW operated in a negative sense, i.e. letting them think they were about to stall again, whereas if they had persisted they would have gone through the warning with a chance of recovery.

As takata has rightly pointed out, IAS greater than 60KTS AND/OR AoA less than 30 degrees are required to prevent the Abnormal Law activating. It is while in this AND/OR regime that a very clear warning needs to be given that the aircraft is stalled. IAS is useful, and AoA is useful, and it would be preferable to know each rather than being left in the dark because one or the other, or both wasn't deemed valid.

[KATLPAX]

"This is a stall. Reduce power and nose down!"

If this quote from the Der Speigel article is true, it seems a puzzling omission from the BEA report given the other quotes and seems to purposefully lead one astray(by omission). It was a definitive acknowledgement by the captain of their situation and how to react.

[Graybeard]

http://upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Faa_pitot_static_system.JPG/350px-Faa_pitot_static_system.JPG

Wiki has some info on pitot-static, but does not explain. I don't think I've seen this explained elsewhere in a long time, so I'll take a stab at making it simple.

The pitot tube captures impact air, which is sensed by an Air Data Module in the A330, and converted to airspeed. The drain tube allows water to pass without clogging the pitot. To do that, it passes air all the time.

The pitot opening is a specific size, say 5mm dia, and the drain is maybe 2mm. That makes the pitot about 20 sq. mm area, and the drain about 3 sq. mm area, for a ratio of about 7:1. This means the impact pressure at the sensor is about 14% less than actual impact pressure.

When it comes to clogging at high altitude, there are these possibilities:

Pitot clogged, drain clogged at same time: IAS, Indicated AirSpeed, will not change with change of aircraft speed, but IAS will increase with increase of altitude.

Pitot Open, Drain CLogged: IAS will increase 14%. 14% excess IAS will remain regardless of actual airspeed or altitude.

Pitot Clogged, Drain Open: IAS will decrease toward zero as the drain bleeds off the impact pressure to ambient. Increased altitude will not affect IAS.

This last situation: "On 28 October 2009, an Airbus A330-202 (A330) aircraft, registered VH-EBA (EBA), was being operated as Jetstar flight 12... (IAS decreased to about 60 Kn). The airspeed disagreement was due to a temporary obstruction of the captain's and standby pitot probes, probably due to ice crystals. A similar event occurred on the same aircraft on 15 March 2009."

The AeroCaraibe incident showed much the same behavior, so it can be expected AF447 was also the same type failure.

Comment?

[jcjeant]

Hi,

Seem's a little bit ironical ... but modern military jet fighters planes have an HUD with many interesting datas just in face of pilot eyes .. all this for assure the safety of one soul .. and some tons of metal and weapons .. and airliners have not this for assure the safety of hundred of souls and some tons of metal.

[fizz57]

Just a general thought - does the Flight Path Vector display use air data at all or is it just inertial? Would this have helped the pilots' SA in this situation?

[mm43]

Graybeard

Yesterday when posting the FDR traces for the Jetstar A330 incident, I mulled over the static port problem, then looked at the ECAM messages and realized that the sequence of events was very similar to AF447. So, getting back to the TCAS fail message, I'm starting to feel that the ALT supplied to the Transponder changed at a rapid rate, i.e. the speed correction value changed, and the TCAS determined the rate of change wasn't valid and shut-up shop.

Do you think that could fit the bill?

[jcjeant]

Hi,

Just a general thought - does the Flight Path Vector display use air data at all or is it just inertial? Would this have helped the pilots' SA in this situation?


HUD ?
A good question for gums or other jet fighters pilots here ......

[mm43]

fizz57
... does the Flight Path Vector display use air data at all or is it just inertial?Boeing use the inertial method, and Airbus use barometric vertical speed and inertial groundspeed and attitude.

[FE Hoppy]

... does the Flight Path Vector display use air data at all or is it just inertial?

Embraer (Honeywell EPIC) uses both and the procedure is to ignore the FPA with unreliable airspeed.

Hi,

Seem's a little bit ironical ... but modern military jet fighters planes have an HUD with many interesting datas just in face of pilot eyes .. all this for assure the safety of one soul .. and some tons of metal and weapons .. and airliners have not this for assure the safety of hundred of souls and some tons of metal.

HUD just repeating what's available downstairs in the cruise so doesn't offer any enhancements when IMC.

[BJ-ENG]

@ventus45


"Worth a read"


Good references - certainly worth the read..

Many thanks...

[HazelNuts39]

mm43 #844;

Airbus FPV uses barometric vertical speed and inertial groundspeed and attitude (explained in BEA report).

mattewsjl #825;

I agree entirely with your analysis. The airplane stalled after 2:10:51.

JD-EE #830;

First three sentences agreed. However at FL375, 215 kCAS, AoA=4° the airplane is not stalled: the normal acceleration is less than 1 (approx. 0.8) hence v/s is decreasing.

[mm43]

HN39
Airbus use barometric vertical speed and inertial groundspeed and attitude (explained in BEA report).
Should have read the report again! Many thanks and I have corrected the error.

[bekolblockage]

Apologies if this has already been spoken about or dismissed - I haven't been able to read all 43 pages so far.

Some of the aspects of this accident just made me recall the following passage from and incident report (although RVSM/TCAS related) involving an A340 entering turbulence over the North Atlantic.

Feel free to disregard if irrelevant.

A340 commander's report
At FL 360 the A340 was 1000 feet below the maximum cruising level displayed on the Flight
Management and Guidance System (FMGS). The commander was expecting a turbulence
encounter around 59°N 20°W and when the aircraft first entered light turbulence he made a cabin
announcement and switched on the seat belt signs. Shortly before the AIRPROX event he
experienced moderate turbulence and noticed outside air temperature changes. Suddenly the aircraft
began to climb, the Master Warning sounded and the autopilot self-disengaged as the aircraft
exceeded the speed limit of 0.86 Mach. The indicated airspeed dropped below VLS (the lowest
selectable) as the aircraft climbed and the commander took manual control of the aircraft because
neither autopilot would engage. The crew subsequently reported the incident to Shanwick on HF
radio and using their TCAS, they descended back to FL 360 in a safe area. At the time of the
AIRPROX the commander estimated the aircraft were one mile apart laterally. After landing at
New York the commander had the aircraft inspected by technical staff but no defects were found.
There were no injuries on board the aircraft.
The commander could not remember the sequence of warnings but he did recall being unable to reengage
either autopilot which prompted him to make manual control inputs. He also remembered
seeing an 'Alpha Lock' warning displayed on his Primary Flying Display.

[RealQuax]

Re http://www.pprune.org/tech-log/452836-af447-thread-no-3-a-37.html#post6483173

If I remember correctly, this chart is part of the analysis of Tim Vasquez of 2009. Is there an updated version around corrected for the now known exactflightpath? As stormcells are very narrow, it might make a substantial difference to the picture...

[sensor_validation]

@bekolblockage (http://www.pprune.org/members/46953-bekolblockage)

You have to go back more than 43 pages! The ballistic zoom-climb trajectory demonstrated by the A340 was suggested as soon as the proximity of the crash site to LKP confirmed - and the FDR plots in Appendix B of the AAIB report re-published a couple of weeks ago. But the A340 in daylight did not lose air-speeds so flight control laws and protections not the same as AF447 - but was way above safe height and must have been very close to stall at the apogee at FL 384 "where the airspeed had decayed to 205 KIAS and 0.67 Mach even though full thrust had been applied". Full thrust was from protection even though A/T off.

[edit] Note that the pitch-up and climb was auto control system induced, the recovery thanks to the pilot requiring bold inputs to break an AoA hold law. There is no mention in the report of stall warning so pitch and AoA correctly managed in the recovery.

There is some uncertainty on these forums as to what/when triggered the pitch up. The A/P kicked off due to overspeed in clear-air turbulence - pitch up seems more likely due to protection against overspeed than the stated "corrected or phase-advanced angle of attack" "excursion beyond alpha prot"?

[BJ-ENG]

@NWR

Thanks for the Tarom ROT381 video link.

The BEA incident report (24 September 1994) makes for an interesting comparison with the current discussion.

http://www.bea.aero/docspa/1994/yr-a940924a/pdf/yr-a940924a.pdf

Of particular interest are the crew comments, CVR readout (p12-13), and the analysis, sections; Incident Sequence, Analysis of the Stall Protection Logic, and Conclusions (p26-34).

[CONF iture]

Just a general thought - does the Flight Path Vector display use air data at all or is it just inertial? Would this have helped the pilots' SA in this situation?
ACARS messages tell that the FPV (bird) has been selected, but the bird on both PFDs disappeared.

Was it available at all, initially ?
Was it followed ?
Was it reliable ?


BEA, the data ...

[mm43]

RealQuax

The Tim Vasquez profile chart is probably as good as it will get. At this time we don't know if the aircraft had deviated clear of the main Cb cells, but its position along the track was a little different than that portrayed in the original chart. The whole ACARS sequence took place in the arrowhead centered on 3°N and the time at 3°N was 02:10:30z (or thereabouts).

[sensor_validation]

...
The AoA vane plus IAS provides the stall warning. Only problem is that the IAS must be greater than 60KTS for the combo to provide the SW. The SW stopped because the IAS had dropped too low, and when they attempted nose-down and got an IAS over 60KTS, the SW started again. ...

That 60 kts again --- why would a blocked pitot and open drain stick at this value? It seems to me that the IAS system outputs 60 kts (or is it 60.001?) when UAS detected, so that protections/warnings that are disabled at low speed are not disabled with UAS.

So if there's any airspeed indicated above or below precisely 60kts its a real live reading, (and if 2 out of 3 agree it is validated and used in protections/warnings) - is this documented?

You can build AoA indicators with pitot style pressure measurements using the fact that the pitot under-reads when not pointing directly into the air-stream, but it must need careful calibration - if simply varying as the cosine of the AoA AF447 would have been indicating nearer 100kts during the descent?

[bekolblockage]

Thanks for that. I must try to keep up!

[sirgawain123]

What puzzles me is the idling of engines (not just thrust reduction: IDLING)

When was it commanded? (At least 2min26sec before impact ?) Who commanded it? believing to be overspeeding, or as a resort to recover a stall that wasnt expected to recover just by sidestick pitch-down commands?

It would have been bettter to release nothing for the shake of releasing a comprehensive interim report, that releasing latest BEA may27th report, where it is quite obvious that they purposedly censor very relevant information that they surely hold!

[HazelNuts39]

sensor-validation;

IAS reflects the difference between pitot pressure and static pressure. Both sources are 'disturbed' at extreme angles of AoA and sideslip. I wonder if BEA has taken possible static source errors into account when quoting altitudes. These should be checked with IRS and/or GPS data.

[sensor_validation]

sensor-validation;

IAS reflects the difference between pitot pressure and static pressure. Both sources are 'disturbed' at extreme angles of AoA and sideslip. I wonder if BEA has taken possible static source errors into account when quoting altitudes. These should be checked with IRS and/or GPS data.

@10,000 ft/min I don't think any correction to text required! But sure any indication will be unsteady and oscillating depending on which port in use pointing which way and how in detail they are combined/ filtered. Google finds this schematic from globalsim.web:-

http://www.globalsim.web.id/publicservice/AF447/A330PitotStatic.jpg

[milsabords]

Machinbird: Only problem with this concept is that what happens to the water droplets that inertially fly through the outflowing air at the pitot inlet and accumulate.

The pump control will increase the inside P to maintain the target air flow, therefore water will eventually be pushed out. If this is a transient situation the apparent IAS spike could be filtered by software.

If it would last longer then the pump control would reach its max value w/o generating the target air flow, and the logic would send a "pitot clogged" signal instead of delivering an erroneous speed value. Hopefully one or two of the other tubes would still work.

[MartinM]

I have been reading through this long thread. Very interesting discussion.

What always was omitted and this is something I am unsure what happened and maybe someone can recall this.

The AP disconnected automatically, but what happened before? What actually made the AP disconnect.

If we go back in history, and I am still not certain what this fact is trying to tell us, please let me tell you this.

I plotted the position of the wreck and the position where the Tail was found. The Tail actually was found 70Km northeast of the location of the wreck. While the sea current where at that day were going northeast to south. How the heck did the Tail get so far away from the wreck assuming that it was still sitting on the tailcone on impact.

Second thing that makes me a bit confused. The 36G arm in the rudder of the recovered tail, was actually found broken. Please keep in min that the 36G arm is not the fixation on the aircraft but the hinge between tail and rudder. This special arm can withstand 210'000 nm of force. The tail cone would have acted as buffer between the tail and the aircraft body. Due to this I cannot think that there was enough force to break it.

Bringing these two elements together makes me assume that the tail was already ripped of the plane earlier. While in deepstall? No. But at what point in time. Maybe exactly at the point when the pilots were doing a right turn. Remember, the FDR said, pilot gave stick input to the left and up. At the same time, ACARS reports a failure of the RTLU. Well, I would say, tail gone, RTLU gone. Logical response of ACARS to report it as failed ;)

As BAE has not release exact coordinates of the flightpath, it makes it hard to overlay with the other position. fact is, they turned back before the decent and due to this the theory looks valid to me.

Opinions?

[takata]

Hi sensor_validation, bekolblockage, everybody,
A340 AIRPROX;
You have to go back more than 43 pages! The ballistic zoom-climb trajectory demonstrated by the A340 was suggested as soon as the proximity of the crash site to LKP confirmed - and the FDR plots in Appendix B of the AAIB report re-published a couple of weeks ago. But the A340 in daylight did not lose air-speeds so flight control laws and protections not the same as AF447 - but was way above safe height and must have been very close to stall at the apogee at FL 384 "where the airspeed had decayed to 205 KIAS and 0.67 Mach even though full thrust had been applied". Full thrust was from protection even though A/T off.
Full thrust was not from protection. The report messed up stuff.
Alpha_floor (as quoted in report) is inhibited above Mach 0.53 if I remember correctly.
Autothrust was disconnected by the crew: they should have received a THRUST LOCK signal (no ALPHA LOCK as reported).
Thrust increased from under 70% N1 (where the autothrust settled it because of the overspeed event before manual disconnection: overspeed protection is first managed by the autothrust) to 100% N1 in a short while. It is unclear if it was due to manual action (I guess it was because N1 was previously stable around 90% before turbulence encounter).

In this case, the climb (and pitch increase) is related to this sharp thrust increase (4 engines at 100% N1), being not countered by nose down imput from the PF.
Autopilot was first disconnected due to overspeed (it was not due to Alpha prot).
This TCAS event just added to the confusion.

Stick pitch axis data on the graph seems also inverted (or alpha_prot kicked at the top of the climb, but it is hard to see it without any AoA data track pictured on the graph - quite disturbing as to suport the AAIB comments).

[Graybeard]

mm43: Yesterday when posting the FDR traces for the Jetstar A330 incident, I mulled over the static port problem, then looked at the ECAM messages and realized that the sequence of events was very similar to AF447. So, getting back to the TCAS fail message, I'm starting to feel that the ALT supplied to the Transponder changed at a rapid rate, i.e. the speed correction value changed, and the TCAS determined the rate of change wasn't valid and shut-up shop.

Do you think that could fit the bill?

Thanks for the question, MM. Jetstar did not get a TCAS Fail, did it?

The companies that build the TCAS also build the ATC Transponders. Like I wrote before, if you're going to insert such a reasonableness filter into the ATC/TCAS system, you would put it in the transponder, as it's just as important to report correct altitude to other aircraft as it is to have your TCAS using correct altitude.

Besides, failed altitude input should cause TCAS to report OFF, not Fail, but I'm not 100% sure of that at the moment. Selecting ALT to OFF on the ATC/TCAS control panel will for sure result in TCAS OFF.

[MurphyWasRight]

mm43:

As takata has rightly pointed out, IAS greater than 60KTS AND/OR AoA less than 30 degrees are required to prevent the Abnormal Law activating. It is while in this AND/OR regime that a very clear warning needs to be given that the aircraft is stalled. IAS is useful, and AoA is useful, and it would be preferable to know each rather than being left in the dark because one or the other, or both wasn't deemed valid.


Any system that pressents "conclusions" to a user without access to the underlying raw data is inherently problematic, especially if there are unknown interactions. (Unknown or untrained for by the users).

Even if the raw data is suspect it should still be presented with a warning.

One analogy for the stall warning action would be an "idiot light" in a car without an oil pressure gauge that signals low oil but goes out if you overspeed the engine.

BTW: For a good example of bad outcome caused by sending "data invalied" rather than "possible error but here is best guess" see the
report for the destruction of the maiden flight of the Arieane5 launcher.

[sensor_validation]

Hi sensor_validation, bekolblockage, everybody,
A340 AIRPROX;

Full thrust was not from protection. The report messed up stuff.

Alpha_floor (as quoted in report) is inhibited above Mach 0.53 if I remember correctly.
Autothrust was disconnected by the crew: they should have received a THRUST LOCK signal (no ALPHA LOCK as reported).
Thrust increased from under 70% N1 (where the autothrust settled it because of the overspeed event before manual disconnection: overspeed protection is first managed by the autothrust) to 100% N1 in a short while. It is unclear if it was due to manual action (I guess it was because N1 was previously stable around 90% before turbulence encounter).

In this case, the climb (and pitch increase) is related to this sharp thrust increase (4 engines at 100% N1), being not countered by nose down imput from the PF.
Autopilot was first disconnected due to overspeed (it was not due to Alpha prot).
This TCAS event just added to the confusion.

Stick pitch axis data on the graph seems also inverted (or alpha_prot kicked at the top of the climb, but it is hard to see it without any AoA data track pictured on the graph - quite disturbing as to suport the AAIB comments).Hi takata,

As discussed earlier, there was no fault found with the controls at the time, the issue investigated was the near-miss. What is clear is that the pitch up in the A340 was after A/P and A/T disconnect, and before any sidestick input, but curiously I now see the stab was moving. The pilot inputs to Mach Speed setpoint before A/T disconnect or manual throttle after are not shown. If the pitch up caused by manual throttle change (CAS had fallen significantly) - is it not true a twin engine A330 has more excess thrust than a four engine A340 (both are certified to take-off with loss of one engine)?

[gums]

The flight path marker in the A-7, F-16, F-15, F-18 and Space shuttle shows inertial velocity vector. Watch the space shuttle landing tonight and you'll see it NASA TV should use a lot of the HUD video as it will be dark outside for normal TV coverage. Sucker shows exactly where you will impact the ground if within the field of view. On one night landing they showed it until the craft lowered the gear. Also showed it a lot when a buddy of mine ( Lindsey) had a decent cloud layer to penetrate.

Scales on left and right show altitude and airspeed. Other guidance symbols are also present.

The A-7 showed inertial vertical velocity on same "thermometer" scale as the altitude. It also displayed an AoA symbol all the time. If inertial went bat sh^%$, it used doppler and basic attitude to provide a reasonable vector, actually a doggone good one. Altitude was either radar or baro. Spped was dynamic pressure as per the steam gauge.

F-16 could display IAS/CAS or TAS or GS. It only displayed the AoA symbol with gear down, but we had other indications of AoA. Altitude was baro until we got the LANTIRN birds and later models.


The good thing about the flight path marker in a fully developed stall is that it is "pegged" at bottom of the HUD field of view or even below it!! In the Viper it would have an "X" over it to tell you it was invalid being outta the field of view.

[takata]

Hi Martin,
The AP disconnected automatically, but what happened before? What actually made the AP disconnect.
AP, ATHR, flags on PFD, etc. all disconnected at 0210:05 due to unreliable airspeed processed by the PRIMs (Flight control computers)... this is the root cause of everything. The system switched to ALTERNATE LAW (PROT LOST) at this point because two or three pitots displayed a variation of airspeed above 30 Kt during one second. As this event lasted more than 10 seconds, ALTERNATE LAW would be definitive until the end of the flight, but autopilot and autothrust could have been re-engaged later if two calculated airspeed would be considered valid again by the PRIMs.

There is absolutely zero doubt that this is why AP went off.

I plotted the position of the wreck and the position where the Tail was found. The Tail actually was found 70Km northeast of the location of the wreck. While the sea current where at that day were going northeast to south. How the heck did the Tail get so far away from the wreck assuming that it was still sitting on the tailcone on impact.
Do you remember also that the floating wreckage was found drifting 6 days later?
The "Tail" was not found: it was the vertical stabilizer part of it... This piece wasn't drifting alone but with the main floating wreckage, including something like 3,000 pieces of this aircraft and 50 bodies.

Bringing these two elements together makes me assume that the tail was already ripped of the plane earlier. While in deepstall? No. But at what point in time. Maybe exactly at the point when the pilots were doing a right turn. Remember, the FDR said, pilot gave stick input to the left and up. At the same time, ACARS reports a failure of the RTLU. Well, I would say, tail gone, RTLU gone. Logical response of ACARS to report it as failed
As BAE has not release exact coordinates of the flightpath, it makes it hard to overlay with the other position. fact is, they turned back before the decent and due to this the theory looks valid to me.
Opinions?

Come-on!
RTL (rudder travel limiter) fault is related to RTL airspeed function that was invalid due to PRIMs rejection! (you can't set a value limiting RTL deflection without a valid airspeed)... NOT that it was ripped off!!! There was 36 cases discussed in BEA reports about "unreliable airspeed" and each had the same RTL fault. All this aircraft landed with their vertical stabilizer!!! This fault could be cleared once the airspeed will stabilise and be considered valid again by the PRIMs.

Please, go read the BEA previous interim reports; they won't write again everything that was already validated as "facts" in each subsequent publication (like this last note). They will only write about any new findings that could invalidate/correct anything previously established (and so far, nothing appears contradictory to what was already established).

[robertbartsch]

So the nose-up input was likely caused by the incorrect assumption that AS was too high; right?

If a stall was being caused by too much AS, wouldn't there be other physical indications (wing shutter, nose over, etc.) to confirm this?

[thermalsniffer]

After spending two years looking at the ACARS messages there some questions I would like to ask the regulars that may be relevant---or not?

1. 2:12:51WRN/WN0906010212 341040006NAV ADR DISAGREE. It is my (probably incorrect) understanding that this message came earlier in other similar events. Is this late in the sequence here and not as a result of the initial problems but occurring at the apogee of the climb and 2nd stall?

2. In the new BEA note, why the first stall warnings at the initial event since stall is based on AoA?

3. 2:13:45WRN/WN0906010213 279002506F/CTL PRIM 1 FAULT and
2:13:51WRN/WN0906010213 279004006F/CTL SEC 1 FAULT
Obviously, not mentioned in the BEA note, were these then a result of failure and not shutdown?

[bearfoil]

robert bartsch (and takata)

2h10m05s. Unreliable a/s.

This is an ACARS message, not a DFDR trace. Something was bollux with IAS in the cockpit to generate the maintenance entry into log.

Takata, you are assuming that ACARS report is real time, and by inference that ACARS reports simultaneously with fault. Impossible.

The Speeds were reported for time 'x' prior to loss of PRIM.


"So the nose-up input was likely caused by the incorrect assumption that AS was too high; right?"

"If a stall was being caused by too much AS, wouldn't there be other physical indications (wing shutter, nose over, etc.) to confirm this?"


Here, rb suggests the pilot may have alertly already responded to bunk data. The ACARS report a/p dropout first, not UAS. If the PF was aviating in Normal Law for a time certain prior to AD hash, his pull and roll would be indicated as correct. He could also manipulate the stick with impounity, and let the protections sort out life on the edge of Stall or wing drop.

Just because our Pilot responded to overspeed doesn't make him wrong.

Overspeed and turbulence may have killed the autopilot, instead of UAS. Although you have said that UAS is without question true.

[takata]

So the nose-up input was likely caused by the incorrect assumption that AS was too high; right?
a) If incorect airspeed was displayed on RHS (not recorded), it would be droping like the two other sources. Hence, why this assumption?
b) First emergency signal was a "stall warning"... not overspeed.
c) PF initial reaction was contrary to a) & b)... unless those signals were duely ignored because of an unknown factor, or that he thought to be the right thing to do in response to a) and b)... and this could have been in case of CFIT alert in Normal law (except thrust settings, but TOGA should kick automatically by alpha_floor function). What make me think it could be an explanation is that it is also exactly what the PF did after the stall warning at 0210:51 (he manually applied TOGA and pitched up).

If a stall was being caused by too much AS, wouldn't there be other physical indications (wing shutter, nose over, etc.) to confirm this?
High speed buffet would take an increase of airspeed above (real) Mach 0.88-0.89 and they were still flying at 0.80. There is no mention of any particular turbulence severity that could have caused a real overshooting of MMO. On the other hand, switching to ALTERNATE would also reduce the MMO limit displayed on PFD down to Mach 0.82 (putting the limit much closer to their real airspeed)... hence, what if the pilot saw that gauge high limit moving close to its airspeed, if it was actually rightly displayed? Could he interpret the warning being an "overspeed" instead of "stall" (even if voiced)?.

[takata]

Hi bear,

I knew it!... no surprise.
This doesn't fit with your own "theories" and you now need to make up few of those "facts".


2h10m05s. Unreliable a/s.

This is an ACARS message, not a DFDR trace. Something was bollux with IAS in the cockpit to generate the maintenance entry into log.

Takata, you are assuming that ACARS report is real time, and by inference that ACARS reports simultaneously with fault. Impossible.
Well, certainly not!
ACARS message are not displayed in realtime, they are stamped to the nearest minute.
There is 14 messages dispatched for 0210, all processed by the CMC between 0209:51 and 0210:50:
2:10:10 -.1/WRN/WN0906010210 221002006 AUTO FLT AP OFF
2:10:16 -.1/WRN/WN0906010210 226201006 AUTO FLT REAC W/S DET FAULT
2:10:23 -.1/WRN/WN0906010210 279100506 F/CTL ALTN LAW
2:10:29 -.1/WRN/WN0906010210 228300206 FLAG ON CAPT PFD SPD LIMIT
2:10:41 -.1/WRN/WN0906010210 228301206 FLAG ON F/O PFD SPD LIMIT
2:10:47 -.1/WRN/WN0906010210 223002506 AUTO FLT A/THR OFF
2:10:54 -.1/WRN/WN0906010210 344300506 NAV TCAS FAULT
2:11:00 -.1/WRN/WN0906010210 228300106 FLAG ON CAPT PFD FD
2:11:15 -.1/WRN/WN0906010210 228301106 FLAG ON F/O PFD FD
2:11:21 -.1/WRN/WN0906010210 272302006 F/CTL RUD TRV LIM FAULT
2:11:27 -.1/WRN/WN0906010210 279045506 MAINTENANCE STATUS EFCS 2
2:11:42 -.1/WRN/WN0906010210 279045006 MAINTENANCE STATUS EFCS 1
2:11:49 -.1/FLR/FR0906010210 34111506 EFCS2 1,EFCS1,AFS,,,,,PROBE-PITOT 1X2 / 2X3 / 1X3 (9DA),HARD
2:11:55 -.1/FLR/FR0906010210 27933406 EFCS1 X2,EFCS2X,,,,,,FCPC2 (2CE2) /WRG:ADIRU1 BUS ADR1-2 TO FCPC2,HARD

First message was recieved at 0210:10 (AP OFF).
The BEA note said that it disconnected at 0210:05 (from CVR "Alarm"/DFDR data AP status, I presume).
We know that it takes about 6 seconds to process an ACARS (due to protocole limitations).
This is obviously fully consistant with "everything started at 0210:05"... before this point, the flight was totally uneventful beside crew conversations about weather avoidance, small offset and speed reduction to Mach .80.
Now, if you want to absolutely shed the doubt by making up particular "events" prior to 0210:05, that's your call but not mine.

[bearfoil]

takata

ami. "...AP, ATHR, flags on PFD, etc. all disconnected at 0210:05 due to unreliable airspeed processed by the PRIMs (Flight control computers)... this is the root cause of everything. The system switched to ALTERNATE LAW (PROT LOST) at this point because two or three pitots displayed a variation of airspeed above 30 Kt during one second. As this event lasted more than 10 seconds, ALTERNATE LAW would be definitive until the end of the flight, but autopilot and autothrust could have been re-engaged later if two calculated airspeed would be considered valid again by the PRIMs.

There is absolutely zero doubt that this is why AP went off..."

Everything never happens at once. If that were so, there would be no time. What happened prior to 2h10m05s to cause "..all disconnected at 2h10m05s?"

[GarageYears]

2. In the new BEA note, why the first stall warnings at the initial event since stall is based on AoA?

Could it be because of this:

From 2 h 10 min 05 , the autopilot then auto-thrust disengaged and the PF said "I have the controls". The airplane began to roll to the right and the PF made a left nose-up input. The stall warning sounded twice in a row.

Previous more knowledgeable folk have stated the stall AoA angle at FL350 is not a large number (my brain has 6 degrees stuck there, but I am far from sure).

[bearfoil]

Is the Stall Warning also inhibited at normal cruise speeds? Hopefully not, and Stall warning can certainly happen at "high speed", Speed isn't what causes Stall, it is Angle of Attack.

[takata]

Everything never happens at once. If that were so, there would be no time. What happened prior to 2h10m05s to cause "..all disconnected at 2h10m05s?"
Bold doesn't make you bolder.
Nothing before 0210:05.
And yes, at 0210:05, the speed function was simply invalidated by the PRIMs after a 1 second check out of its limit range... that's all!
It is all you need to have the following sequence of ACARS (and more).
- First dispatched: those are the cockpit effects (warnings) without failure.
- Root system failures are at the end of the ACARS list for the whole sequence: Pitots fault and this ADIRU faults.

CMC needed to crosscheck what systems caused the failures (internal, external, etc.) before dispatching the failure ACARS while cockpit effects are immediatly processed once they occured. The following time sequence is due to the protocole as the messages are queued and dispatched one by one. It will be clear from the DFDR tracks that all those warnings were basically simultaneous and that any delay in warning would be caused by priority order functions.

For example, there is a small delay between AP OFF and ATHR OFF because the later is retardated for not confusing both cockpit alarms sounding.

[HazelNuts39]

A tentative time-history of altitude and airspeed based on total energy is shown in this TEplot (https://docs.google.com/leaf?id=0B0CqniOzW0rjZTJiNDlmNWUtY2NmYS00YTUwLTlhYTQtYjQxZWE zM2NkYjYx&hl=en_GB&authkey=CIDUn-8O). Imagination mostly, of course, but more or less consistent with the datapoints in BEA's Update.

[MurphyWasRight]

takata:

On the other hand, switching to ALTERNATE would also reduce the MMO limit displayed on PFD down to Mach 0.82 (putting the limit much closer to their real airspeed)... hence, what if the pilot saw that gauge high limit moving close to its airspeed, if it was actually rightly displayed? Could he interpret the warning being an "overspeed" instead of "stall" (even if voiced)?.



Very interesting point, if the PF was scanning the "gap" between MMO and speed more than absolute values he may well have perceived a jump in airspeed when ALTERNATe mode was entered rather than the drop in MMO.
Pity that one very relevant parameter (PF arispeed display) was not recorded on DFR.

[jcjeant]

Hi,

A revised graphic chronology ......

http://peloche.smugmug.com/Travel/Airplane-views/i-B97QLCv/7/O/AF-447-O.png

[sensor_validation]

...A revised graphic chronology ......

Highlights lots of gaps we haven't been told about - but plotting ACARS messages at receipt time only shows when aircraft attitude able to communicate with satellite - not when they were generated.

[grizzled]

jcjeant...

Re my response to CONF's question about access to investigation information, you wrote:


It's just for the organization between states ..... it's not realy instructive about who have really access to the data .... IMHO


Without going into too much unnecessary detail, I have a lot of experience with both Annex 13 and many of the State investigative agencies that are bound by its requirements (including BEA).

First, Annex 13 is not "just for the organization between states"; it is the document that States (including France) must comply with, as the basis for how to conduct investigations (supplemented or modified by State legislation and any differences filed with ICAO).

With specific reference to your statement about "who really have access to the data", BEA can, of course, include any other party they wish as part of the investigation. They can also release any portion of the data to any party they wish (an example might be a specialised psychologist to review and comment on crew voices under stress), in which case BEA would place confidentiality restrictions (as per Annex 13) on that person with regard to the information they have received.

Lastly, apart from the BEA investigation, there is a French legal investigation underway, and there will of course be other legal actions arising out of this accident. Who will have access to the CVR and DFDR data for those purposes is a matter for French (and possibly other State)courts.

[grizzled]

MurphyWasRight...

Re your post #864: :ok:

[alf5071h]

Some ‘Human – Technical’ thoughts … … and questions, … mainly questions.

It is widely assumed that the event was triggered by ice particle blockage of the pitot tubes. With all three blocked it is also likely that the TAT probes suffered blockage, probably simultaneously; ref previous events and see VH-EBA (not simultaneous), #692 graphic and report link.

If the ‘sudden failure’ of airspeed (an erroneous low value) was accompanied by an erroneous low altitude (as with VH-EBA), then the indicated altitude deviation could also attract the crew’s attention. Would the altitude alerter sound?
Thus with apparent simultaneous failure of all air data and logical auto-flight disengagement, the crew’s initial thoughts might have been of a system failure – a technical issue.

The PF took the controls, but with the perception above, may have concentrated on altitude. In every day operation there is significant focus on altitude – ‘beware altitude bust’, TCAS, interview, loss of license, etc; these could easily be hidden (subconscious) operational and social pressures which might have influence the initial action; pitch up to recover the assigned altitude, back stick and follow-up trim.
I assume that the trim datum is still attitude (flt path?) and zero control input. Would the control law be attitude or flight-path stable with these system errors. If flight-path, how is flight-path computed, inertial or with air-data mix, and if air-data and the air-data is erroneous … … ?

Would the FD still be active, if so, in which modes and what command might be shown?
We should recall the many discussions of how modern crews depend on the FD; a general low experience level of basic instrument flying. Was an erroneous FD command followed resulting in an inappropriate manoeuvre?

Would an abnormal TAT (rising towards zero, based on previous events, A/B and other aircraft types) affect any other instrument display systems of flight guidance computation?

If airspeed was erroneous, and the altitude is also affected by this and also possibly from ‘abnormal’ temperature, what about Mach, and any residual protections (MMO pitch-up bias), i.e difference between computed Mach (and rate) vs computed MMO.
From what has been describes so far it may be impossible to take any of the quoted air-data values as representing the true condition of the aircraft; except perhaps the vane derived AOA. What source of information does the FDR record, is this always the same as what the crew will see?

Roll deviation might be considered a separate but confusing issue. If the YD ‘froze’ (fail-safe) with air data ‘failure’ (as designed?), then an offset rudder would induce roll and a permanent roll bias, but its effect varying with actual airspeed – need to use rudder. But who uses rudder in normal (symmetric power) flight?

With these distractions and concerns of system failure, then any more speculation about crew thought and behavior would be unjustified without further data.
However, the trim position is a dominant issue, and without awareness of this offset, basic flying could be difficult and probably added further confusion.

At a late stage, nose down control action did effect a pitch change and an apparent speed increase (a semblance of stall recover but with the confusion and aerodynamic complications of mis-set trim). The speed increase was sufficient to reinstate the previously inhibited AOA driven stall warning; probably further confusing the mental picture – nose down pitch apparently caused a ‘stall’ ??? … what next; undo what you have just done, back stick? Perhaps this is normal (to be expected) human behavior.
Also, think about how the industry discusses stall – some thread discussion, education, and training. Virtually every aspect is speed related – stall ‘speed’, warning ‘speed’, stall displayed on a ‘speed’ tape, the importance of gaining / maintaining ‘speed’; even if a crew had been taught that the stall warning was AOA driven and that the aerodynamics of a stall involve AOA, is this information recallable, or would ‘speed’ dominate our thoughts.

There is much more to come, much to be learnt, and probably all intermixed in technical, human, and social system (operational/organizational) interactions.
At this early stage, we might consider how crews are educated / trained, and what is currently expected of them. How might everyday operation influence encounters with a very rare and unusual events? Are modern norms based on a remarkably benign (safe) operation so that it is now unrealistic to expect extremes of experienced-based innovative behavior? Has the industry overlooked ‘change’, and retains old, inappropriate assumptions?

To reassure any PAX Ppruners (and the media), the industry remains very safe. Incidents such as this are very rare and the assumed precursor (high confidence) – ice particle blocking is generally understood. Safety action is in place – changing the type of pitot tube, manufacturers have refreshed crew dills for loss of airspeed and stall recovery, and operators are applying these training aspects. The industry is not (must not be) complacent; a thorough and tenacious investigation is underway from which we expect ‘lessons to be learnt’; but it’s still up to us to learn.

[takata]

Highlights lots of gaps we haven't been told about - but plotting ACARS messages at receipt time only shows when aircraft attitude able to communicate with satellite - not when they were generated.
You meant that ACARS at reciept time only shows when the CMC was able to dispatch them thru the satellite link.

ACARS sequence/order/time is due to the processing time logic, being queued, and to protocole limitations as nothing (so far) is indicating that she could have reached an attitude that would broke the satellite link: up to +20 deg pitch and +/-40 deg bank angle combined should make any ACARS sending possible every time from the begining to the end.

Now, it is also possible that the satellite could be, at one point, busy with other aircraft sendings (as there is not so many satellites above this place and the total bandwith was not illimited). That is also how I interpreted the BEA quote "that the satellite link could be broken" (due either to aircraft attitude or satellite not available for login).

[wes_wall]

Wondering what the proceedure syllabus AF uses for application of TOGA. Would assume that at some point, the airplane would wish to climb, and that the THS would move to nose up.

Begs the question also, is there any system , irrespective of whatever Law may be active, which effects the THS if and when TOGA is enabled?

[DozyWannabe]

Begs the question also, is there any system , irrespective of whatever Law may be active, which effects the THS if and when TOGA is enabled?

Only if the A/P was enabled, which in this case it wasn't.

[MartinM]

sensor_validation Quote:
Originally Posted by jcjeant http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/buttons/viewpost.gif (http://www.pprune.org/tech-log/452836-af447-thread-no-3-a-post6485275.html#post6485275)
...A revised graphic chronology ......

Highlights lots of gaps we haven't been told about - but plotting ACARS messages at receipt time only shows when aircraft attitude able to communicate with satellite - not when they were generated.



Actually there are two time stamps. The first on is the sending time stamp. The second one, within the message, is the time of the generation.

[JD-EE]

HN39 #847: "First three sentences agreed. However at FL375, 215 kCAS, AoA=4° the airplane is not stalled: the normal acceleration is less than 1 (approx. 0.8) hence v/s is decreasing."

That brings us back to spurious stall warnings, doesn't it?

[takata]

Actually there are two time stamps. The first on is the sending time stamp. The second one, within the message, is the time of the generation.
Not exactly: the first one (precise stamp, like 0210:10) is the time stamp at "reception" of the ACARS. The only clue about the sending time is that it takes about 6 seconds to be processed between the aircraft and the satellite (both way). Hence, it was sent about 6 seconds before the receipt time stamp (an acknowledgement "successfully sent" is recieved by the aircraft 2 seconds later). By this way, it was assumed that the aircraft had crashed at the earliest at 0214:28 because the last recieved ACARS (0214:26) was processed up to the "successfully sent" return acknowleged by aircraft.
Now, the BEA confirms that she crashed in the same second at 0214:28.

[tubby linton]

Readers of thisforum may want to refer to fcom page 3.01.20p4a which shows a graph for determining high and low speed buffet

[takata]

Hi JD_EE,
That brings us back to spurious stall warnings, doesn't it?
Right. This first stall warning seems to be due to a change in stall function (it is mach based above Mach 0.75) to AoA based function. Unreliable airspeed seems to affect everything like static pressure, which is mach sensitive, AoA indication which is mach sensitive... Then when you lose the mach function for a while, this become a real issue. Beside, the stall warning is kicking above VSw1g with some margin for taking into account any possible overshooting.

[mm43]

MurphyWasRight; Grizzled;

Re post #864... :ok:

HN39;

Thanks for the TE Plot.

[DJ77]

Takata, re the A340 AIRPROX, you wrote:
In this case, the climb (and pitch increase) is related to this sharp thrust increase (4 engines at 100% N1), being not countered by nose down imput from the PF.


Hmm, the flight controls were in normal mode and no sidestick controller input was made until 28 sec. after AP diconnection when they were already a thousand feet above their assigned level.

I thought that in normal law, compensation for thrust variation was provided.

Anyway, except for human factor aspects, this incident appears unrelated to AF447, this one being in ALT law.

[HazelNuts39]

That brings us back to spurious stall warnings, doesn't it? Why would that be? At M=0.8 stall warning is set to occur (see 2nd Interim Report) at approx. AoA=4°, alpha-max = 5°, and the real stall is probably between 6° and 7°. The second stall warning occurred "around 6°" at M=0.68, where alpha-max=7.3° and stall probably beyond 9°. I suspect that people who stubbornly maintain that these stall warnings are 'false' don't really understand what they mean. An intermittent warning such as may occur due to AoA- and hence g-variations due to turbulence may be considered 'inappropriate' since it doesn't require recovery action from the crew, but that doesn't mean it is false. It means that the AoA has temporarily exceeded the stall warning threshold.

Takata,
the stall warning threshold has to maintain a certain margin below alpha-max which defines the 1g stall speed. For all Mach numbers greater than 0.275 alpha-max reduces with increasing Mach, and therefore also the stall warning threshold AoA. Just take a look at the FCOM page presenting Vs1g (https://docs.google.com/leaf?id=0B0CqniOzW0rjMjhkNzY2NTUtZDk3My00MGRhLWI1MGMtMTNjN2Y 5MWI0M2U5&hl=en_GB&authkey=CMWNxvMD).

[Lonewolf_50]

Amazing amount of material posted in the last few days. I was out of town, :E and so did not FOD the thread.

A thought on AoA probes and 60 knots.
My personal experience with the US Navy peg, cone and vane type AOA sensors is that they would come alive in a definite breeze, perhaps 10 knots.
A vane type that needed 60 knots to be reliable would be a sticky one in my book.
Aye, but here is a thought: if the mission designed approach and takeoff speeds are typically 150 kts and more, maybe the design criterion can accept them not being as swift as the nautical brand at less than half of the operating speeds? :confused:

Two thoughts I see bubbling up, the answers to which are not clear to me.
Once they were in Abnormal Attitude Law, the Stab (THS) Trim remained where it was last. (In this case full nose up)

From the "flight & laws" link above, if in Direct Law the pilots will see "USE MAN PITCH TRIM" on the PFD. Is that also the case in Abnormal Law?

Is there an unambiguous answer to those nested questions?

What I don't see from the latest BEA narrative is how many attempts to move the stick down, or move the nose down, were in play. Two are mentioned. Was that all?

This related to an earlier observation: a continuing attempt to move the stick down (though they mention some instances of stick movement toward nose down, the event flow is hard to discern) to unstall also runs into temporal distortion and its effects on pilots handling upsets.

Many pages ago, one of our posters pointed out that he was suprised to learn how long it takes for his inputs to unstall one of the big jets. With that in mind, was the crew in AF 447 (if and when they finally figured out "we are stalled!") not aware of how long it takes to get the AoA to start increasing again for the position they were in when "we are stalled and falling" became evident?

We may never know. CVR might tell.

Aside/musing. (Not sure how applicable this is to the mishap underdiscussion).

FWIW, from a pilot, but not an Airbuss 330 pilot.

If I command the nose down or up with the stick, and the nose does not go up or down, there is something horribly wrong, and I am by definition, in a condition known as out of controlled flight.

I am using a very simple definition of out of controlled flight.

You are in the aircraft, you make inputs with the stick and rudder and throttle, and the plane does not respond as you command it to. (Or, as you expect it to). Recovering from out of controlled flight is a skill set that relies on the flight controls working as they are known (or designed) to work in response to your inputs, so you have to get to that state. As an emergency or recovery procedure, out of controlled flight recovery means taking a set of steps that gets you to the point where the flight controls respond to your inputs to go up, down, left, right, etecetera. It often takes time and altitude to get through those steps.

From a pilot and human factors point of view, and the flight regime the cockpit crew found temselves in ...

Given the flight regime they were in, and considering the likely concerns about not overspeeding or going to fast in turbulent air present due to envirnonemt, the crew was in the condition for a surprise upset:

You don't expect to be stalled, which means you have to spend "x" seconds (or fractions thereof) overcoming the denial stage, and getting to the action stage. (Responding to your training and knowledge of your equipment and situation).

That some of the cues were either ambiguous or at odds with previous training looks to have led to counterintuitive responses ... but we don't know what PF was seeing.

Further thought on aerodynamics and degree of stall.

If the answer to the two nested questions is "no visual alert" and "yes, you need to take over manually to get THS to work the nose attitude to your advantage" then there is a possible training improvement to be harvested.

To the question of ineffectiveness of elevators, as aircraft speed decreases, due to V^2 ... the slower you are in the airstream, the more pronounced the effect of THS overwhelming the elevators in pitch control. (I hadn't considered the masking due to high pitch/AoA). Does this make sense, in terms of me understanding that characteristic of the flight controls?
The deeper into stall you go, particularly if THS running most of the way up was a factor, the harder it is to unstall with your stick control.

Maybe my math on that is off, and it washes out and is a linear relationship.

Yes, pitch and power brigade, the basics are important.

[CONF iture]

Thanks for the reference grizzled.
So is it correct to say that for the time being the data belong to the BEA and the BEA has the liberty to give access to the parties that could provide expertise for the good of the investigation ?
I believe, us, as people of what is called a 'free society' should have access to those data. There is a lot of expertise on the net too ...
Anyway, what would be the downside to publish them ?

[JD-EE]

HN39 #894
That is why I used "spurious" rather than false. I thought 215kt and 4 degrees would likely calculate into an imminent stall, if stall warning pays attention to speed at all. (Off hand I'd be surprised if it didn't in my non-pilot naivete.)

That suggests that things broke down with that stall warning at 37500 feet. The PF appears to have made an inappropriate action, full throttle and pull up - the apparently prescribed action to take before a stall. But it never seemed to help but the PF kept the stick back fatally long even as the thrust was, at some time, reduced to idle. It was at idle at 2 h 12 min 02, and TOGA at 2 h 10 min 51. That's all I can extract from the report.

It would also be nice to know how long and how much "up" was asserted at 2 h 10 min 05. That could tell a lot more of the story just in itself.

[mm43]

Graybeard;
Jetstar did not get a TCAS Fail, did it?You are right, it didn't.

I was aiming more at the ALT erroneous speed correction component, and its rate of change which may have been too much for the TCAS. The problem right now is we don't know whereabouts in the 0210 minute the NAV TCAS FAULT occurred, and it could be related to a combination of the speed error correction and the zoom climb, i.e. both were heading in different directions. Or the changes occurring between valid and invalid data.

Here's a clearer copy of the VH-EBA FDR print-out (http://stafflink.co.nz/a330/images/VH-EBA-fdr-graphic-2.png) for reference.

[takata]

Hi DJ77,
Hmm, the flight controls were in normal mode and no sidestick controller input was made until 28 sec. after AP diconnection when they were already a thousand feet above their assigned level.
I thought that in normal law, compensation for thrust variation was provided.
Well, in fact, even in Normal Law, it is not really able to compensate for thrust change as it is described in the A330 FCOM (3.04.27):
http://takata1940.free.fr/A330_NOR%280%29.jpg

Anyway, except for human factor aspects, this incident appears unrelated to AF447, this one being in ALT law.
Certainly, beside human factor aspects. But maybe it is an issue that those human factors appears to be seriously challenged when several crisis are declared at the same time (TCAS event/turbulence/overspeed for this A340 crew).

[matthewsjl]

That suggests that things broke down with that stall warning at 37500 feet. The PF appears to have made an inappropriate action, full throttle and pull up - the apparently prescribed action to take before a stall. But it never seemed to help but the PF kept the stick back fatally long even as the thrust was, at some time, reduced to idle. It was at idle at 2 h 12 min 02, and TOGA at 2 h 10 min 51. That's all I can extract from the report.

Well, immediately before that stall warning, we know that the aircraft was climbing. The report states the rate of climb had been reduced and the VS was recorded as +700ft/min. The altitude was reported as FL375.

The report is clear that the descent started 3m30 before the end of the recoring - so that would be 2h10m58s. So, my guess is that there was about 7s between the warning and the actual stall.

Now, they reached a max altitude of FL380 - so there was some climb energy left before the actual stall and we know the two immediate actions at the stall warning by the PF were TOGA and nose up sidestick.The engines would have taken time to spool up. I reckon that they were too close to the stall and the nose-up at the warning pushed them into an actual stall.

[DJ77]

Takata, tks for pointing me to FCOM3

[PJ2]

mm43, graybeard;

The TCAS has numerous system inputs. One of the inputs is the stall warning system. I think the NAV TCAS FAULT message was triggered by a programmed inhibition of the TCAS warning.

When certain other systems require a higher priority in terms of pilot attention and aircraft systems/performance/energy, they inhibit warnings which would compromise such priorities. Here, the priority would be aircraft energy to recover from a stall, so a TCAS warning is set aside as the lesser danger and is inhibited during such an event. The AUTO FLT REAC W/S DET FAULT warning has the same source.

The BEA Second Report seems uncertain regarding the source. Even though the second reason, (altitude differences > viability of data) makes a bit more sense than the electrical notion, the above reason should be examined as possible or dismissable. The inhibition isn't strictly a fault and if the two messages, (stall/TCAS) were ever "in competition" for attention/energy, perhaps the TCAS would simply remain silent.

Anyway, just thinking...always hazardous!

[etudiant]

Ignorant question. It has been surprising that the PF control input almost throughout this incident has been NU. Could it be related to the bank that he appeared to be offsetting pretty much throughout as well? The note in the basic control law that suggests keeping the nose up in a tight turn was interesting to this layman.

[BarbiesBoyfriend]

Looks to me that the initial climb may have been due to a combo of flight through uplifting air, pilot induced pullup to avoid wx or possible a/c induced pullup due high speed, perhaps only flight director commanded if AP already OFF.

It's hard to see why else they would do that initial pullup and there seems to be a precedent in that other 'airprox' uncommanded pullup.

After that, when they ran out of energy, it seems clear that no-one on the FD realised that 'nose down' on the sidestick wouldnot be enough. They needed to trim.

Ah.....'trim' the basis of good piloting! Completely ABSENT in Airbus normal ops.

I mean, if you NEVER trim, how are you expected to realise that you are badly out of trim?

[SaturnV]

According to the victims association, the Ile de Sein has recovered 75 bodies, bringing the total bodies recovered to about 125.

Not clear whether this concludes this phase of the recovery process, or whether Ile de Sein has retrieved any parts of the plane (other than seats).

Also nothing said on whether there would be any future attempt (phase) to recover other parts of the plane.

[Graybeard]

Good thought on the Stall Warn priority, PJ2, but Windshear Warn, GPWS Pull Up and GS Warn will merely silence the TCAS audio and put the TCAS in to TA, Traffic Advisory mode while the Warn is active.

IIRC, Stall Warn will not silence the TCAS, as they may go hand in hand. At any rate, it will not cause a TCAS Fault. Stall Warn could possibly take priority over the GPWS, but I'm not certain of that. I'll dig.

[PJ2]

Graybeard, yeah, I think you're right...the "fault" makes no sense. I'll dig too.

[takata]

Ignorant question. It has been surprising that the PF control input almost throughout this incident has been NU. Could it be related to the bank that he appeared to be offsetting pretty much throughout as well? The note in the basic control law that suggests keeping the nose up in a tight turn was interesting to this layman.
It doesn't look like if they attempted a "tight turn" in normal law. The bank oscillation was certainly due to AP going off with an induced right roll momentum that should have been trimmed by rudder corrections. The control law switch to alternate caused the roll axis to be direct (and sensitive) as the controls are powerfull (hence, stick moving left and right).

Read below, effect in roll direct and trimming the rudder:
http://takata1940.free.fr/A330_ALT%280%29.jpg
http://takata1940.free.fr/A330_ALT%281%29.jpg
http://takata1940.free.fr/A330_ALT%282%29.jpg
http://takata1940.free.fr/A330_ALT%283%29.jpg

[BarbiesBoyfriend]

Takata.

What about trimming?

Was the trim wheel moved?

[Smilin_Ed]

Ah.....'trim' the basis of good piloting! Completely ABSENT in Airbus normal ops.
I mean, if you NEVER trim, how are you expected to realise that you are badly out of trim?

Do I understand this correctly:
1. Auto Trim continues to function even though the autopilot has disconnected?
2. There are no trim buttons on the sidesticks?

[A33Zab]

As in the BEA report is stated 'uneventfull' before 0210:05'
and then suddenly Pitot Probes clogged due to ice.

I'm wondering why the ice detection system didn't trigger an ICE DETECTED (0,5 mm ice aggretion within 60 sec.) WARNING MESSAGE?

Can accept that within the timeframe a SEVERE ICE DETECTED (7 times 60 sec.) is never shown.
I can also imagine that the visual ICE Indicator between the windshields is not in direct view during all the mess,
but the ICE DETECTED message should have been there!



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

[takata]

Hi BarbiesBoyfriend,
Takata.
What about trimming?
Was the trim wheel moved?
Why should I bother to answer you after your very informative first post here. You obviously posted without even reading a couple of pages from this thread, don't you?
Read it.
All the questions you asked (airprox, trim, etc.) were already answered, some of them only a couple of post ago, some further back.

[DozyWannabe]

Do I understand this correctly:
1. Auto Trim continues to function even though the autopilot has disconnected?
2. There are no trim buttons on the sidesticks?

1. Yes - Autotrim is part of the FBW systems as opposed to the A/P and A/THR systems.
2. No, but there's a big manual trim wheel just like on the other airliners in exactly the same place. The questions being raised involve training to use it.

I'm wondering why the ice detection system didn't trigger an ICE DETECTED (0,5 mm ice aggretion within 60 sec.) WARNING MESSAGE?

In that part of the atmosphere what you're dealing with is not ice as it is generally considered, but supercooled water. This is water that is below freezing point, but still liquid because it has almost zero contaminants. Stick a big piece of metal into that water and it freezes into ice in less than a second. This was demonstrated in the BBC/NOVA documentary.

[takata]

Hi Dozy,
In that part of the atmosphere what you're dealing with is not ice as it is generally considered, but supercooled water. This is water that is below freezing point, but still liquid because it has almost zero contaminants. Stick a big piece of metal into that water and it freezes into ice in less than a second. This was demonstrated in the BBC/NOVA documentary.
More likey, some very small ice crystals (which are not detectable by radar) and not supercooled water at this level flight (which is detectable).

[BarbiesBoyfriend]

Takata

I've not seen much on how the Airbus normally trims for you. But I might have missed a bit here and there.

I think that while Airbusses design is great when it's all working , it's notso when in ''not normal' mode.

But hey, what do I know?

Sorry to disturb you.

Call me 'old fashioned' but I prefer to look after the trimming myself, and I'm used to doing so- unlike the AF447 pilots.

Frankly, I think the Airbus is the aircraft the erodes piloting skills more than any other. Anyone care to disagree?

[kilomikedelta]

The MBA's that run commercial aviation to generate maximal shareholder value would rather not have any bodies on the flight deck. Silicon Valley assures us that cybernetics transcends human behavior in anomalous situations so that pilots are an unnecessary expense. Hull losses are a cost of doing business the bottom line impact of which is mitigated by aggressive legal action and publicists smoke and mirrors. How many airlines have failed because of accidents or flight crew errors? How many airlines have failed because of MBA incompetence? How many airlines were reborn under a different corporate name with the same MBAs managing them to carry on the pattern?

[PJ2]

Frankly, I think the Airbus is the aircraft the erodes piloting skills more than any other. Anyone care to disagree?
Please....can we just keep to the topic at hand and not launch yet one more 'eroding skills' discussion...it's been done to death and never resolves a thing.

Sorry, BBB, but dang, it gets a tad tiresome and will only produce another round of A vs B, Colgan vs the FAA and whatnot.

I flew (almost always manually to cruise, the descent, approach and landing) the A320, then A330/A340 for fifteen years. One doesn't lose one's skills, one permits flying skills to be lost, and THAT is a professional standards matter, not an airplane, airline, regulator or other matter. Disconnect the damn airplane and the autothrust and stay familiar with the airplane.

There's far too much blame about "loss of skill" directed elsewhere when the real one responsible for any loss of one's skills and professionalism is in the mirror. If your airline wont' let you hand-fly because they like automation, to hell with them and their MBAs, fight them on it!

Take a look at the stats: we've had far too many fatal accidents resulting from the most basic failure of all and which we're trained to avoid and prevent from Hour One in our first flight...stalling the airplane. If the training isn't there in the syllabus, demand it.

Sorry, but enough is enough.

[takata]

Takata
I've not seen much on how the Airbus normally trims for you. But I might have missed a bit here and there.
I think that while Airbusses design is great when it's all working , it's notso when in ''not normal' mode.
Would you pull up to max deflection while trimming down your nose at the same time?
Certainly not.
If their THS was trimmed close to max (+13/14 deg), it was because autotrim followed their NU imputs. Once AoA overshoot +30 deg, autotrim was not working anymore: it could only be applied manually by the trim wheels (see my post above and parts about trimming manually in direct law).

Basically, it means that they didn't aknowledge to be in a developped stall at the first place, hence, trimming down was not their main issue: their lack of nose down imputs certainly was before they reached such an high AoA while falling from FL380.
Even so (without manual trim imputs), elevators (if not fully stalled) should have had enough power to recover below +30 deg AoA (due to low airspeed) and autotrim would then follow their nose down imputs. When and how much did they try? we still don't know yet from the release of informations.

[BarbiesBoyfriend]

PJ.

OK. After this I'll never mention it again.....but...the trimless Airbus helps its pilots all the time trimwise, right up til when it stops. And then it leaves them precisely where?:rolleyes:

I know you can practise 'manual flight' in an Airbus just like any other a/c, but please don't forget a bus ain't like a non-bus. In many ways.

Takata, to answer your first question, of course not, but the pilot held the stick back, the bus trimmed the tail 'nose up' (almost to max) and then stopped trimming.

So now, the pilot had to manually reverse, using his manual trim wheel that he never uses, a trim input that he never made!

Youre second point, that they ought to be able to push over even with the tail trimmed for full nose up I dispute (but only from experience of non-buses, so dismiss it if you like. These tails are really powerful though).

Third point, if implied, 'why not stick full forward til impact'. I'm as baffled as we all are.

I see you are from Toulouse.
I just think the bus rather isolates its pilots from what's actually happening. That's just an opinion.

[DozyWannabe]

Silicon Valley assures us that cybernetics transcends human behavior in anomalous situations so that pilots are an unnecessary expense.

Uhh... No we don't.

(At least this Brit working for a Silicon Valley firm doesn't!)

PJ2 - Don't sweat it, they'll get to the bottom of this sooner or later, anything anyone says now is just conjecture. :)

BarbiesBoyfriend - The trim wheels are there and if airlines aren't training the pilots when and how to use them correctly that is not Airbus's fault. Old school "communion with man and machine" was lost as soon as the first widebodies came along, maybe even earlier - even the old 747 Classic, DC-10 and L-1011's feel was entirely artificial.

[galaxy flyer]

Anyone,

Is "auto-trim" a feature of the B777? I think auto-trim is a function of Airbus' design which does not trim to hold a sped, but trims to maintain a set flight path. Nothing wrong with that, but different.

Gums

Any comments on the Viper's auto trim?

GF

[kilomikedelta]

Dozywannabe; The take home message by management from engineering to the board room is that the glass is full. Now it's time to discuss board compensation.

[DozyWannabe]

@KMD - I say again, not in real-time safety-critical software engineering you don't. You're getting generic corporate/sales culture (which I've ranted about on this very forum at great length some time ago) and the work that many very talented and safety-conscious people have done to make modern aircraft as safe as they are badly confused.

[PJ2]

OK. After this I'll never mention it againBBB...this is a conversation between mature adults, both pilots. I'm not about to control what people do or say. I'm asking for a little forebearance in terms of the discussion, which, because you are a regular here, you know that the topic has been done, over and over again and gets us nowhere; the airplane is what it is and it seems to work well for those that fly it.

The thread was beginning to settle down into serious discussion, and I could see it taking off once again on another familiar tangent.

On your second observation re a "bus ain't a non-bus" , you've never flown the Airbus so you can't comment on it with any foundaton of knowledge or experience.

I've said many times here that where the airplane deserves critical assessment, and I've done lots of that over the decades, then I''m all for solid feedback based upon knowledge. But to be fair, and to be taken seriously in discussion, one has to go beyond what others say about the airplane, and know for oneself, the subject of criticism. The airplane is nowhere near as different as you have the impression, an impression gained through hearsay, not actual experience. The incident/accident record of the airplane is adequate proof of this.

The trim, and its availability to the pilots of AF 447, has been discussed at length as has standard responses to the stall. If managements of airlines, in their wisdom fail to teach about the airplane and, either through parsimony or the illusion that 'these airplanes fly themselves', fail run a sufficiently robust recurrent training program to ensure a depth of knowledge and that training precludes hand-flying and system knowledge, (vice Need-to-know nonsense), then that needs to be firmly resisted and changed. There is plenty of evidence now in place for change, beginning with those up front.

[kilomikedelta]

Dozywannabe; I think we're on the same wavelength. Risk management has a different definition in engineering and corporate culture. Engineers apply a risk factor to their equations to protect the applications of their work, MBA's try to see how much risk they can get away with before they declare bankruptcy and then create a new corporation to try it again. How many MBAs have died as a result of their aircraft management decisions? K

[Capn Bloggs]

One doesn't lose one's skills, one permits flying skills to be lost, and THAT is a professional standards matter, not an airplane, airline, regulator or other matter. Disconnect the damn airplane and the autothrust and stay familiar with the airplane.

There's far too much blame about "loss of skill" directed elsewhere when the real one responsible for any loss of one's skills and professionalism is in the mirror. If your airline wont' let you hand-fly because they like automation, to hell with them and their MBAs, fight them on it!

Take a look at the stats: we've had far too many fatal accidents resulting from the most basic failure of all and which we're trained to avoid and prevent from Hour One in our first flight...stalling the airplane. If the training isn't there in the syllabus, demand it.

You're being a bit harsh. There are companies that DO NOT PERMIT less than full automation. Pilots can "fight" all they like and achieve nothing. Read a few pages back where Airbus pilots were being slapped if they touched the trim wheel.

Do you really expect a bright-eyed, bushy tailed sprog to jump up and down on a training course demanding more stall training in the supposedly uncrashable Airbus?

[Machinbird]

I'm still hoping some with Airbus A330/340 experience will be willing to discus their experiences with Alt 2 Law. This version of Alternate law is a 'Roll Direct' mode of operation.
How much training do pilots get in this mode?

If the aircraft was laterally imbalanced when you assumed control, wouldn't you have a heck of a time keeping the wings level? (Particularly if you are one of those AB pilots who routinely flies cruise with feet on the floor.)

I can see some serious potential for interference with proper pitch control until the aircraft is trimmed up with the rudder.

[JD-EE]

PJq - re your note to DozyWannabe is there a distinct display for the pilots when the plane is actually stalled rather than facing an imminent stall? If not, wouldn't that be a worthwhile addition to the software?

[PJ2]

Capn Bloggs;

Yes, it is a bit harsh, isn't it. It's how this matter, (the intoxication with automation), which I and many here and elsewhere, have been writing about since the 90s, is going to get resolved.Do you really expect a bright-eyed, bushy tailed sprog to jump up and down on a training course demanding more stall training in the supposedly uncrashable Airbus?
You're setting up a straw man argument and answering your own question. Of course I don't expect it. We both know that one person cannot change policies or world-views of large organizations (which depend upon "group-think" for continued existence), but I think it is realistic to expect the matter to be addressed maturely and through due process within the applicable groups and pilot organizations. There is sufficient material and evidence now upon which to base change. In fact, agree with the wisdom of such change or not, it is occurring in the US and in Australia; I can't speak for Europe.

Regards,

PJ2

[takata]

I know you can practise 'manual flight' in an Airbus just like any other a/c, but please don't forget a bus ain't like a non-bus. In many ways.
That is why one need to be qualified to fly it!
But, you can also be sure that some are more qualified than others, same with any other type. In AF447 case, it is very likely that the PF was more qualified on this type and sector than the two other pilots taken together (including the Captain, also qualified for Caravelle XII, Boeing 737 and manual trim wheels).

Takata, to answer your first question, of course not, but the pilot held the stick back, the bus trimmed the tail 'nose up' (almost to max) and then stopped trimming.

Right. She stopped auto-trimming. It happens when the system believes the attitude "abnormal" (+30 AoA or speed below 60 kt, or pitch > +60... or because they used the manual wheel, or because the load factor was < 0.5 g... we still don't know yet! In any case, it is writen in the PFD "USE MAN PITCH TRIM" where you can't miss it (see PFD drawing above).

But the very relevant fact is that they pulled up during the first minute of their stall in order to reach such a THS setting. Then, they had two and half minutes left before impact and we still have not a single clue in order to understand at which point they finally acknowlegded their full stall situation.
After this point, I wonder if that would have made any difference if the trim wheel was auto or manual, that this aircraft was A, B or C...
Until we know more about what confused the pilots, jumping in and claiming that everything was linked with the trim wheel (they were not used to) doesn't make any sense. You won't use it if you dont think first that pushing the stick will help you to recover.

So now, the pilot had to manually reverse, using his manual trim wheel that he never uses, a trim input that he never made!
What do you specifically know about their training with manual trim or direct law?
Did you read anything about it?
How many pilots already stalled an aircraft without autotrim?
Quite a few, no?

Youre second point, that they ought to be able to push over even with the tail trimmed for full nose up I dispute (but only from experience of non-buses, so dismiss it if you like. These tails are really powerful though).
Well, be sure that I dont know it myself but Airbus is stating that below 185 kt, elevator control is powerfull enough to override a jammed THS above +8 deg. After 185 kt, it is not so easy. Beside, while being at +13 deg, when those nose down imputs were applied, the AoA reduced... then, it was still effective to a certain point.
I see you are from Toulouse.
I just think the bus rather isolates its pilots from what's actually happening. That's just an opinion.
Yes, I'm from Toulouse, which mean that I prefer Rugby over Football (soccer). And that's just an opinion.
S~
Olivier

[LoboTx]

Unless I skipped a page somewhere, I've not seen this posted. Apologies if it has been.

75 additional bodies recovered from Air France crash after 2 years - CNN.com (http://www.cnn.com/2011/WORLD/europe/05/31/france.jet.crash/index.html?hpt=hp_t2)

This is contrary to decisions I thought were made weeks ago. Surely it's been posted and I missed it ?

[takata]

If the aircraft was laterally imbalanced when you assumed control, wouldn't you have a heck of a time keeping the wings level? (Particularly if you are one of those AB pilots who routinely flies cruise with feet on the floor.)
It takes a hand in order to trim the rudder.

You're being a bit harsh. There are companies that DO NOT PERMIT less than full automation. Pilots can "fight" all they like and achieve nothing. Read a few pages back where Airbus pilots were being slapped if they touched the trim wheel.
Your source is quite moot: this guy is a troll (ask him for full details and proofs about his claim). I don't know who is behind that but there is a bunch of guys around repeating always the same stuff which is mostly posted from one single source (internet) which belongs to some anti-airbus crusaders. Hence, this is fully circular as we always end at the same point, in this case, the very same url.

[Machinbird]

Takata
It takes a hand in order to trim the rudder.Yes, but before that, it takes a recognition of why the WING is heavy.

[takata]

Hi Machinbird,
Yes, but before that, it takes a recognition of why the WING is heavy.
Oscillations doesn't specifically mean an heavy wing after switching to direct roll. Read the part of the FCOM I posted above and you'll see that it is mentioned that you may have to re-trim the rudder in order to stabilize your roll axis.

[gums]

@ Galaxy:

The Viper "auto trim" seems identical to that of the Airbus except for the bank angle and pitch attitude corrections. Actually, not a bad idea for a heavy, but a bit clumsy for the fighter plane requirements. So we trimmed for gee as set using a trim wheel or the thumb hat switch on the stick ( HUD showed instantaneous gee to a tenth of a gee). We could trim for zero gee and during a fight let go of the stick and get less induced drag to "extend" or gain energy.

The 'bus computers add to the basic one gee gee command for a bank angle. So in 30 deg of bank it trims for 1.15 gee or so. Same for pitch - a 30 deg climb would be trimmed for about 0.87 gee, otherwise pitch would continue to increase if still trimmed for one gee.

Neither the Viper or the 'bus trim for attitude, best I can tell from the manuals.

Some folks seem to misunderstand the airspeed/altitude displays and such when talking about the HUD.

BARO DATA IS NOT USED FOR THE FLIGHT PATH VECTOR in any application I have looked at except a "poor man's" FPM (flight path marker - that little airplane doofer)

What it is used for is the speed/altitude part of the display - those "thermometer" doofers on each side of the display. Same for vertical velocity, which could be baro or inertial, depending on a switch. Some planes only show baro VV. Some planes can show radar alt versus baro, and the beat goes on.



I read a symposium presentation by some dude about the Airbus HUD installed in some variants. Thing sounded like a poor man's HUD, and I can't understand a modern plane without a cosmic, large field-of-view HUD, especially for landing and takeoff. Ask 'bird about a night cat shot off the boat without a HUD. The FPM showing your vector was above the horizon was very "comfortable". It also helped getting back onboard at the very end of the task, although flying the meatball was as good or better.

In the AF447 situation, an inertial FPM would have been invaluable showing the crew their flight path with respect to local level. After all, you can have the nose up at 16 degrees and still be falling like a rock! Think I saw that number last week.

HUD "pitch lines" are also easy to read and use. So setting a 3 degree glide path or climb is a no-brainer.

PLZ try to watch the shuttle landing in an hour or so, and you can see a real HUD in action.

Otherwise, I'll hunt down some You Tube sequences to show mine. Haven't digitized my LEF failure landing but it is a good one to see how the thing helped me land.

[galaxy flyer]

Thanks, gums I had read a magazine description of the Airbus and Falcon 7X FBW system as being flight path stable, that is, it holds a flight path, but expressed as G-stable makes better sense.

I used the crude HUD in the A-10 and loved it, as a new toy. Now, in the Global, the HUD is wide-angle, has EVS, and is invaluable for all flight regimes, especially night visuals; using EVS, figuring out if you will clear that cloud deck; single engine work.

[Machinbird]

Oscillations doesn't specifically mean an heavy wing after switching to direct roll. Read the part of the FCOM I posted above and you'll see that it is mentioned that you may have to re-trim the rudder in order to stabilize your roll axis. Takata, Can I have the pillow you sleep on?

From the brief description BEA provided, the guy flying was bombarded by more stimulus in his few minutes holding the stick than most drivers get in an entire flight.
Do you really expect him to recall the words from FCOM in that short a time period unless he actually practiced such an eventuality as he experienced that night?

Everyone has been real quiet about their experience in Alt 2 law except the test pilots.

Do you think any really constructive training was accomplished in Alt 2 law prior to this accident? (And by really constructive, I mean the kind that makes you both think and sweat.)

[alex_brin]

Hi this is a question from a lay point of view,
Tim Vasquez's weather analysis seems to show that the flight passed through a smaller portion of the storm came to a clearing which perhaps caused the captain to think they had cleared the storm? when in fact they were just about to enter a larger portion which then caused the pitots to ice up causing the autopilot to kick off. Would the captain have gone to take a rest if he had known the larger part of the storm was yet to come? — and if not, why isn’t there more accurate information in flight at night when they have no sight visuals? Is it true that it is easier to know with greater certainty about storms when flying over land vs sea, because there are more sightings?

The records seem to show that the flight just before and just after chose not to go through this storm, but around. Is there any truth to a report I read at the time, that this flight (in trying to save gas) was cut so close they didn’t have the option, in terms of enough fuel, to go around the storm?

Just wondering.

It seems that if the captain was on deck, by this remark,"This is a stall. Reduce power and nose down!" he might have been able to save the flight, unless there are other factors impacting the situation which aren’t clear. I think from the discussion here there are far too many reasons why the situation might have been confusing to assess in the few minutes they had once the chain of events began. Some might know what to ignore and what to attend — though certainly having the stall warning go again when the needed action was begun certainly was no help in the short time to assess and respond. Clearly changes are needed to avoid many parts of the sequence which caused this — the freezing of the pitots, perhaps better weather analysis or clarity of weather conditions, not ever assuming in training that basic air tools would never be needed because a computer system now takes over those roles, when that system can turn off and require pilots to fill in at any time (or at least, always at a time unexpected), with pilots having both a need to know all that the system is doing for the pilot and to have it spelled out quickly and clearly, as well as an ease and comfort with all these tools and sequences, so life and death decisions can be made with clarity and accuracy in unexpected circumstances on what might otherwise be a routine flight. Since the flight just before and after diverted — was there pressure to go through weather unnecessarily?

If there is any question about conditions, is there truly the free choice option to go around the weather, as did the flights just before and after, rather than through (to save gas or time); — or at the least — there should not be any pressure to make such a safety decision based on gas related issues, if there is any truth to that (?) Was that an impact here to not simply choosing to be safer and go around?

[Should passengers be putting more pressure on airlines regarding weather decisions to give pilots more breathing space and freedom to make needed choices? (or at least not to be pressured to go towards questionable conditions, if this is indeed happening?) Is this an issue?]

At each of these earlier levels, the flight would never have been put in this situation — on the other hand, there are so many factors impacting the pilots’ decisions once the sequence began, it seems these problems simply need attending to and if not this flight, another would have brought them to the fore.

I wanted to mention these less technical observations, simply because as a passenger now, I’ll always wonder if simple logic is being waved or honored, not so much by pilots at the time, but the myriad of technical choices made beforehand — which perhaps is at the heart of much of the concern about this loss.

Please forgive the very lay point of view, but profound interest to this sad incident.

[MartinM]

I understand that the NPF says, "we have lost the speeds, alternate laws then"

According to the checklist, I don't get the point why the PF, which was FO No2, the one with the least flight experience, pulled the side stick.

As we know from the FDR data, the climb was commanded and not coming from an updraft turbulence.

By pulling the stick he induced a vs of 7000, which exceeds the max of the aircraft by 1000 ft/m. 6000 is max.

Secondly, the A330, same as the A320 are equipped with two GPS systems apart from the pitot tubes. Even if all of them have failed, the still could verify GS on the ADIRS panel overhead and in MCDU.

He pushes the throttle handle into TOGA which is according to the checklist alternate at that time. Somewhere I read that this is revised now.

I exercised this yesterday on an A320 sim @FL360. TOGA will not initiate a climb at 7000 ft/min. And he PF managed to reduce to 700 ft/min as per FDR data. Why the heck would he still climb. We are not talking about a propeller engine that generates dramatic updraft at full throttle.

CB ceiling was up to FL550. Clearly not over-flyable. I really don't get the point why the PF pulled on the sidestick.

I did already once a deep stall an the A340 sim at FL390. I am was unable to recover. I was falling out of the skies. No matter how far forward I pushed that stick, the nose never got down to recover as I can do on the F18. My deep stall, was nose up with about 20°

Off-Topic, because was asked.
Now for all those asking about my flying experiencing. I have only Level-D sim experience and MS Flight Sim. I have 6 hours on A340 Level D and 2hrs on F-18C Level D. I am not a pilot. And realtime flying experience on MS FS about 4000+ hrs A320/A330.

[deadheader]

An observation, and a question:

By arguing against further Automation in Aviation you are inadvertantly making the case FOR further automation in avation.

To suggest automation is the wrong direction means that you have chosen to ignore the bigger picture - the overall safety situation - and, by doing so, have behaved in a flawed way, a flaw that wouldn't have been displayed in the behaviour of, for example, a machine.

To put it another way, by allowing prejudice to influence your opinion on automation, you are actually proving that automation is ultimately the only answer.

The only question is, therefore, will you realise this and choose to work 'with' progress, thus maintaining an input (pun intended) and helping to shape the future of aviation, or will you continue to resist progress, thus act as a catalyst for the very thing which you resist?

[MartinM]

Ventus45 wrote:


Pretty strong statement.
Convict the PF and hang him out to dry ?
What FDR data - we don't have any solid (hard / actual) data (evidence) yet - not re "the actual dynamic resonses of the aircraft" to those SS inputs - we only have "implied" outcomes.

I have to disagree your honour.
Would a rational pilot deliberately go for such a zoom ?
I doubt it your honour.
I fact, your honour, I am convinced, that there were other than PF influences, both external (air mass) and internal (systems - fbw autonomous inputs, and law effect confusion).

With regards to your SIM experiments, my gut feeling is that since it is a known fact that the SIM's don't have validated algorithms for outside the certified envelope, although such experiments may be interesting (even fun) to do, what (if any) value can you attribute to them ? Without flight test validation, what have we got, Garbage in - Garbage out.

I stated the bare bones of my theory on the upset in a previous post at http://www.pprune.org/6361157-post3246.html
What has so far been released "from the BEA" has not caused me to change my mind re the prime scenerio, except to refine the "slow flat spin" part into a ""stalled mush" with slow right yaw" (as we now know the aircraft did a right 270 on the way down, and of the PF's long held left stick, apparently attempting to pick up the right wing, which, by the way, none of the bus drivers have explained or even addressed yet).

The BEA have released very time porous information for what was a very time dynamic event, nowhere near good enough.
A simple spread sheet (or simple delimited text file) with only nine columns of data would give us all that is needed (all of which they have) and would be very useful.

How about it Mr BEA ?
Hereby formally request a list of (from just before the actual upset to impact) 300 seconds (second by second, line by line) worth of data covering:-
"g_vert-u/d" "g_lat-l/r" "pitch_attitude-u/d" "roll_attitude-l/r" "SS-u/d" "SS-l/r" "pedal-l/r" and "AoA".
Who are your calling "your honour"?

The A330/340 level-d sim is at least as good as the real aircraft when it come to manouvers and flight controls. Yes, agree. Maybe forces and turbulences have differences compaired to the situation you might encounter outside in real live. In the end it is a flight deck sitting on hydaulic legs.

I was not trying to blame the PF at this stage. I did not say hang him. All I try is to figure out what made him pull after disconnecting the AP. But obviously there is no real data around to get a conclusion on this.

Yes, maybe BEA will release at some point further details of the FDR and CVR. A reconstruction of the instrument situation would be interesting.

[Right Way Up]

The level-d sim is at least as good as the real aircarft when it come to manouvers and flight controls.

So you know that the A320/A330 sim you have used has "valid" data for deep stalls?

Not exactly sure how the sim can be better than the aircraft, unless it is used as a toy!

[MartinM]

So you know that the A320/A330 sim you have used has "valid" data for deep stalls?

Not exactly sure how the sim can be better than the aircraft, unless it is used as a toy!
No, sure. I was not intending to refer to the deep stall. I was more related to Ventus45 saying that the SIM is not good enough.

The SIM can simulate failures and things alike, no? I can stall the SIM and it happened. Don't know why it happened but anyway I screwed it up at that point. Never analyzed it. I was there for fun. Remember?

At least I can say that the Airbus will not pitch up 7000 ft/m if protections are active. No matter how hard i pull or push on the stick.

I am very unsure if the were in ALT1 or ALT2. Based on the ACARS, with two ADR failed, it's supposed to be ALT2.

[sensor_validation]

...At least I can say that the Airbus will not pitch up 7000 ft/m if protections are active. No matter how hard i pull or push on the stick...

Can you recreate the 2000 A340 airprox zoom climb from FL360 to FL384 at up to 6,000 ft/min ?

[Right Way Up]

At least I can say that the Airbus will not pitch up 7000 ft/m if protections are active

What protection will stop the aircraft climbing at 7000fpm?

[MartinM]

What protection will stop the aircraft climbing at 7000fpm?


Under Normal Law, there is a pitch attitude, as well as a bank angle protection and some other too, like a-floor, ...

Input on the SS that exceeds the Normal Law parameters, will not be executed by the flight control computers. Thats my easy way to explain it. Maybe someone can explain it in a more technical correct way.

[tubby linton]

Stalled AF447 did not switch to abnormal attitude law
By David Kaminski-Morrow ([email protected])


Investigation into the accident sequence of Air France flight AF447 has revealed that the Airbus A330 did not enter the abnormal attitude law after it stalled, despite its excessive angle of attack.
The abnormal attitude law is a subset of alternate law on the aircraft and is triggered when the angle of attack exceeds 30° or when certain other inertial parameters - pitch and roll - become greater than threshold levels.
Alternate law allowed AF447's horizontal stabiliser to trim automatically 13° nose-up as the aircraft initially climbed above its assigned cruising altitude of 35,000ft.
The stabiliser remained in this nose-up trim position for the remainder of the flight, meaning that the aircraft would have had a tendency to pitch up under high engine thrust.
Crucially the abnormal attitude law - if adopted - would have inhibited the auto-trim function, requiring the crew to re-trim the aircraft manually.
After stalling, the A330's angle of attack stayed above 35°. But while this exceeded the threshold for the abnormal attitude law, the flight control computers had already rejected all three air data reference units and all air data parameters owing to discrepancy in the airspeed measurements.
Abnormal law could only have been triggered by an inertial upset, such as a 50° pitch-up or bank angle of more than 125°. "That never occurred," says French accident investigation agency Bureau d'Enquetes et d'Analyses.
The BEA is still attempting to explain why AF447's crew failed to rescue the aircraft after it climbed to 38,000ft and stalled. The pilot's control inputs were primarily nose-up, despite the stall condition.
There has been no indication that the aircraft switched into any other control law, other than alternate, during the accident - suggesting that auto-trim was available throughout the descent.
Failure to realise a need for manual re-trim was central to the loss of an Airbus A320 over the Mediterranean Sea about six months before the AF447 crash.
The auto-trim had adjusted the horizontal stabiliser fully nose-up but, during a flight envelope test involving near-stall, the aircraft switched control laws and inhibited the auto-trim.
Without manual re-trimming, the aircraft pitched up sharply as the crew applied maximum thrust. It stalled and the crew lost control.
In its conclusions over the accident the BEA highlighted the rarity of the need to trim manually, which created a "habit" of having auto-trim available made it "difficult to return to flying with manual trimming".
"One of the only circumstances in which a pilot can be confronted with the manual utilisation of the trim wheel is during simulator training," it said. "However, in this case, the exercises generally start in stabilised situations."
In the wake of the A320 accident, near Perpignan in November 2008, the BEA recommended that safety regulators and manufacturers work to improve training and techniques for approach-to-stall situations, to ensure control of an aircraft in the pitch axis.
Stalled AF447 did not switch to abnormal attitude law (http://www.flightglobal.com/articles/2011/06/01/357394/stalled-af447-did-not-switch-to-abnormal-attitude-law.html)

[BarbiesBoyfriend]

Sensor validation/ MartinM.

It will certainly climb at 7000'/min if its in a sufficiently powerful updraft, indeed it could be hard to stop it doing so.

That climb must have been a combo of pilot input, weather and maybe aircraft input if speed too high.

[Right Way Up]

MartinM,

I think you'll find the aircraft can climb at more than 6000fpm and remain in normal law!

[MartinM]

Sensor validation/ MartinM.

It will certainly climb at 7000'/min if its in a sufficiently powerful updraft, indeed it could be hard to stop it doing so.

That climb must have been a combo of pilot input, weather and maybe aircraft input if speed too high.


Yes, agreed.

[MartinM]

I think you'll find the aircraft can climb at more than 6000fpm and remain in normal law!


Maybe, yes.

[Chris Scott]

Salut encore takata,

Am catching up, currently only 40 hours behind in this plethora of mess ages...

Re the time-stamp on the ACARS warning/failure messages:

is it your understanding that the timing is to the nearest whole minute? For example, does a time-stamp of "0210" mean that the event was generated between 02:09:31 and 02:10:30 (inclusive)?

Up until I read one of your posts this week, I was assuming that a time-stamp of "0210" would mean that an event took place between 02:10:00 and 02:10:59 (inclusive).

On the off-chance that you spot this post, ;) I would appreciate your clarifying this important (30-second) ambiguity.

[takata]

Hi Chris,
Nice to see you.
Salut encore takata,
Am catching up, currently only 40 hours behind in this plethora of mess ages...
Re the time-stamp on the ACARS warning/failure messages:
is it your understanding that the timing is to the nearest whole minute? For example, does a time-stamp of "0210" mean that the event was generated between 02:09:31 and 02:10:30 (inclusive)?
Yes, the "nearest minute", is what I thought:
02:10 = 02:09:31 - 02:10:30.

But after reading you and checking again the French report it is writen: "précis à une minute près".... not what I remembered "à la minute la plus proche".
Hence, it is more probably what you said:
02:10 = 02:10:00 - 02:10:59

[jcjeant]

Hi,

About all those posts on "blaming the pilots or not" "blaming the constructor or not" "blaming the airline or not" (on the basis of available fragmented informations so far ..)
A straight report will be
If the pilots are in fault on the AF447 ... the case is simple and the final conclusion of BEA will not contain any recommendations concerning the aircraft.
If the pilots are not at fault .. and so it will be recommendations concerning the aircraft
But I'm sure it will be not so straight ... and certainly it will be recommendations about the pilots and airline (training SOP .. etc...) and recommendations for the constructor(s) and recommendations for the regulators
Seem's to me a usual and honest scenario and it will be no different for the AF447 case.
So .. it will be also many food for the court of justice
Nobody will go out white from this accident.

[A33Zab]

Tubby:


The abnormal attitude law is a subset of alternate law on the aircraft and is triggered when the angle of attack exceeds 30° or when certain other inertial parameters - pitch and roll - become greater than threshold levels.
........
Abnormal law could only have been triggered by an inertial upset, such as a 50° pitch-up or bank angle of more than 125°. "That never occurred," says French accident investigation agency Bureau d'Enquetes et d'Analyses.



From the BEA report:


"The angle of attack, when it was valid, always remained above 35 degrees."


More questions to answered by BEA!!!


From the AMM:


"Abnormal attitude law,
This FCPC law is engaged when certain aircraft parameters exceed pre-determined values.
This law ensures that the flight control law will never hinder aircraft recovery.

The laws available are:
- in roll: the yaw alternate law,
- in pitch: an adapted Nz law, without autotrim.

After aircraft recovery, and until landing, the laws available become:
- in roll: the yaw alternate law,
- in pitch: the Nz law (with recovered autotrim)"

"The Nz law is such that the aircraft response is quasi independent of aircraft speed, weight, and CG location.
If both ADIRUs are failed, the Nz law is kept, but with limited pitch rate and gains.
A consolidation of the vertical acceleration and pitch attitude rate is then performed via the two accelerometer units."


From the FCOM:


"An abnormal attitude law in pitch and roll is provided, if the aircraft is in flight and in any of these
conditions :

– Pitch attitude > 50° nose up or 30° nose down

– Bank angle > 125 °

– Angle of attack > 30° or < − 10°

– Speed > 440 knots or < 60 knots

– Mach > 0.96 or < 0.1



The law in pitch is the alternate law without protection (except load factor protection) and without auto trim.

In roll, it is a full authority direct law with yaw alternate.
After recovery, the flight controls laws are:
In pitch : Alternate law.




In roll : Direct law with yaw alternate law."



I think we already all concluded that it did enter -abnormal attitude law- but only after THS was auto-positioned in 13 ANU, and never recovered from this law.

[sensor_validation]

Stalled AF447 did not switch to abnormal attitude law

I don't see this statement from BEA - not even from an alleged "source close to the investigation". About as reliable as the media reports who was PF in which seat? The BEA report states that the "The inconsistency between the speeds displayed on the left side and on the ISIS lasted a little less than one minute" and 2 out of 3 means they agree - even though we don't know what RHS was displaying.

Maybe possible abnormal attitude law not triggered because of the cross-link between real and indicated airspeed and AoA - at high AoA IAS much lower than TAS, and low IAS suppresses use of AoA?

[Lonewolf_50]

Takata, it may take a hand to trim the rudder, but if you are a pilot, you are taught to fly with your feet. (I understand that some people are taught to stop doing that ... ) The point of the trim (particularly if we are discussing manual trim versus auto trim) is to set a new rudder position so that you don't have to keep making smaller and smaller inputs.

From the diagrams I have, there are rudder pedals on the Airbus 330.

Using your feet to move the rudder is a skill taught from Hour Zero in anyone's flying career ... a skill that appears to atrophy with disuse. :mad:

[takata]

Hi tubby,
Stalled AF447 did not switch to abnormal attitude law (http://www.flightglobal.com/articles/2011/06/01/357394/stalled-af447-did-not-switch-to-abnormal-attitude-law.html)
Thank you for posting this. IMO, it changes everything.
Their source is the BEA and I presume that it is a very serious matter if the BEA informed them at this stage of "no switching to abnormal attitude"= no trace of it in the DFDR. Those technical informations are too precise for being another "rumor".
It means that autotrim was available all the way down.
It means also that:
a) either they never really pushed the stick in order to recover as the THS did not move back.
b) The THS was jammed (but they should be able to say it).

Consequently, a) being much more probable, it would also mean that they never acknowlegded the real situation (being stalled).
My opinion is that one may make a serious mistake (bad reflex, etc.) but it doesn't fit with 3 pilots confronted to a situation lasting four and half minutes.

I'm pretty convinced now that there was an unknown factor involving instruments that fooled the PF, hence more specifically the Right Hand Seat which is feeded by ADIRU2. Also, by deduction, the pilot flying was David Robert, 37, with 6,547 flying hrs including 4,479 on type. He was by far the more experienced A330 jockey on the deck and was PF from take-off. His reaction was immediate, he was not asleep, and he should have been fooled by something.

[MartinM]

From the diagrams I have, there are rudder pedals on the Airbus 330.


Yes. And those pedals are used as wheel brakes too, on ground, of course ;)

Rudder Trim, is a small knob on the center pedestal console, while elevator trim is a large trim wheel besides the Throttle.

[takata]

Hi Lonewolf,
Takata, it may take a hand to trim the rudder, but if you are a pilot, you are taught to fly with your feet. (I understand that some people are taught to stop doing that ... ) The point of the trim (particularly if we are discussing manual trim versus auto trim) is to set a new rudder position so that you don't have to keep making smaller and smaller inputs
Your comment is irrelevant with the point I was making about trimming the rudder for addressing the sensitive roll axis being direct. It takes a hand, nothing more. Read again what I was talking about before jumping in.

[Lonewolf_50]

Yes, Martin, I also gathered that from the cockpit and flight controls layout available in the public domain.
Read the part of the FCOM I posted above and you'll see that it is mentioned that you may have to re-trim the rudder in order to stabilize your roll axis.
takata, I'll suggest to you that pilots know that because that is part of flying.

The mental and congnitive process, when you are doing this on instruments (which I presume AF 447 crew were, as it was night and the Wx was bad) is to set an attitude in balanced flight and trim to hold that attitude in all three axes. (Plural of axis)

What I was taught and used to teach was to trim nose and rudder first, aileron last, to avoid cross trimming, but such technique is probably model dependent.

[hetfield]

Victims' families want to ground A330/340 fleet.

Air-France-Absturz: Hinterbliebene wollen Airbus-Flotte stoppen - SPIEGEL ONLINE - Nachrichten - Panorama (http://www.spiegel.de/panorama/0,1518,766039,00.html)

[tubby linton]

A33Zab,I have emailed the journalist from Flight about the article.I will let you know the basis of his story when I have it

[RealQuax]

..there is no such thing as elevator trim.

[takata]

takata, I'll suggest to you that pilots know that because that is part of flying.
Again, I was addressing (only) the specific case of reversing from Normal law to Alternate (not general flying skills here, this is type/law related). This could explain the initial oscillation in roll that would be fixed by re-trimming the rudder due to this axis protection being released as it went direct.
Take it easy.

[MartinM]

Takata wrote:

I'm pretty convinced now that there was an unknown factor involving instruments that fooled the PF, hence more specifically the Right Hand Seat which is feeded by ADIRU2. Also, by deduction, the pilot flying was David Robert, 37, with 6,547 flying hrs including 4,479 on type. He was by far the more experienced A330 jockey on the deck and was PF from take-off. His reaction was immediate, he was not asleep, and he should have been fooled by something.


No.Incorrect. Co-Pilot No2 was PF starting 1:55 according to BAE report may. Taken from the CVR. He took over Captains seat, left at 1:59.


A 1 h 55, le commandant de bord réveille le second copilote et annonce « […] il va
prendre ma place ».

Entre 1 h 59 min 32 et 2 h 01 min 46 Le commandant de bord quitte le poste de pilotage.


PF had 800+ hrs on this type.
NPF was David Robert

At 2h11, the captain took again the pilot seat. This was already in the decent.

Vers 2 h 11 min 40 , le commandant de bord rentre dans le poste de pilotage.


I deliberately took the french version, as the english translation contains some differences

[Denti]

But the captain wasn't the pilot flying if i read the report correct, he was the PNF on that sector and the copilot 2 took over his place, as PNF.

[Meikleour]

MartinM: If I can make a small contribution to this thread. I have flown the A330 in ALT 2 LAW after a twin ADR incident due to icing conditions.
What surprised me was how "twitchy" the aircraft was, especially in roll. The handling was much harder than I had experienced in the simulator during training. We however continued to have valid ADI indications with which to fly attitude + power whilst trying to sort out the very numerous ECAM warnings plus alternating "Stall, stall" + overspeed warnings (spurious of course)
Why the crew should have applied pitch up inputs is a mystery to me unless it was a response to a perceived large overspeed but then why leave the power up?

As mentioned by other posters - the need to manually trim the THS forward is an area that is often seen to be missed by crew undertaking unusual attitude recovery training, especially from very high nose up attitudes and is, in my opinion, one of the few `real gotchas` about the aeroplane.

[sensor_validation]

@MartinM

I'm with takata all the way - are we reading the same document?

[takata]

Hi Martin,
No.Incorrect. Co-Pilot No2 was PF starting 1:55 according to BAE report may. Taken from the CVR. He took over Captains seat, left at 1:59.
There is nothing in the French report saying that.
. At take off, Captain is PNF from his LHS; FOx is PF from RHS.
. At 0159, Captain go to rest and FOy takes his place (LHS) as PNF.
. AP2 is engaged, meaning that the aircraft is flown from RHS.
=> If the PF was FO2 at take off, FO1 would have taken his RHS (but he didn't).
It means that the PF at take-off was FO1 from his RHS (David Robert).

The ambiguity (and press belief) is due to this sentence "le commandant de bord réveille le second copilote"
But it takes to be a French native speaker to understand correctly that it doesn't mean "2nd Officer" but the other co-pilote (as they are two on board, it could be either copilot).

[beachbunny]

Takata,

Quote: His reaction was immediate, he was not asleep, and he should have been fooled by something.

Do you not mean, "he should [B]not[B] have been fooled by something?

A thought has crossed my mind, bearing in mind that we are talking about iced up pitots, maybe static systems, could it be that their altimeters were not unwinding like one would imagine, with a 10,000 fpm descent, and that their VSIs were also not responding to the descent? Possibly even showing a climb, when they were actually descending.

As I've mentioned earlier, a prolonged nose down input should have brought them out of the stall, but why would you do that, if there was no indication that the sea was getting closer...

[MartinM]

There is nothing in the French report saying that.
. At take off, Captain is PNF from his LHS; FOx is PF from RHS.
. At 0159, Captain go to rest and FOy takes his place (LHS) as PNF.
. AP2 is engaged, meaning that the aircraft is flown from RHS.
=> If the PF was FO2 at take off, FO1 would have taken his RHS (but he didn't).
It means that the PF at take-off was FO1 from his RHS (David Robert).

The ambiguity (and press belief) is due to this sentence "le commandant de bord réveille le second copilote"
But it takes to be a French native speaker to understand correctly that it doesn't mean "2nd Officer" but the other co-pilote (as they are two on board, it could be either copilot).


rgr on this. Missleading in the german and english translation and i misread this in my french knowledge.

[tubby linton]

I just received this from the Flight journalist:

This information – that the aircraft did not switch into abnormal flight law – has been confirmed by the investigating authority.

[ttcse]

Meikleuor
"Why the crew should have applied pitch up inputs is a mystery to me unless it was a response to a perceived large overspeed but then why leave the power up?"

I'm wondering if at that point they believed they were in a serious downdraft.

Also, the only transcript of events I've seen must be omitting cockpit conversations. There is too little talking.

[spagiola]

Incorrect. Co-Pilot No2 was PF starting 1:55 according to BAE report may. Taken from the CVR. He took over Captains seat, left at 1:59.

Quote:
A 1 h 55, le commandant de bord réveille le second copilote et annonce « […] il va prendre ma place ».

First, "Prendre ma place" can refer simply to the captain's physical position, ie his seat, not necessarily to his role.

Second, you forget that the captain was PNF. So even if the new arrival did take over the captain's current role, he would have become PNF.

There's enough ambiguity in the French version that your interpretation is possible, but to this native French speaker it seems more natural to read the report as saying that the initial PF remained PF.

Note, for example that it is the PF that conducts the briefing for the new arrival.

[BluJet]

New here as a writer. Read almost every article on this tech-log thread#3. Thank you, for all the good ones!

@takata
post #931
Your deduction concerning the PF omits that the 800hr F/O was not qualified to fly in the L/Hseat (see first BEAreport). So for me, it could have only been the 32year old, 800hr F/O who was PF.
your post #908 and #934
whereas I appreciate most of your posts and your efforts to get the"specialists" back to the ground I want to make a few comments.
We train to use the rudder(trim) mostly for engine out and crosswind landings on transport category aircraft. Especially after some accidents, where airplanes had been taken apart by misuse of rudder. I know the FCOM suggests to do so in some cases, but had that improved their situation? The chances of making it worse are much greater. (I totally agree with post #937).

I dont know whether you are pilot (maybe engineer?) but if you have a chance, watch pilots performing the F/CTL check on ground after engine start. you will often find that few are moving elevator only, respectively ailerons only when performing this check. In other words there is a good chance (especially under stress and during turbulence) that you also move parts of flight-controls which you did not intend to move in the first place. And, as you wrote, those ailerons are powerful in ALT2.
Please don't get me wrong! I really appreciate your work!



The friday BEA report really makes me sick, the new discussion about whether the aircraft was in ABNORM ATT LAW or not is a good example. If not, why did they not provide this information on friday?
A lawyer would probably state that this report would imply "circular reasoning".

[sensor_validation]

@tubby

And the French BEA now put out official releases via a reporter based in London?

[Machinbird]

Meikleour

MartinM: If I can make a small contribution to this thread. I have flown the A330 in ALT 2 LAW after a twin ADR incident due to icing conditions.
What surprised me was how "twitchy" the aircraft was, especially in roll. The handling was much harder than I had experienced in the simulator during training. We however continued to have valid ADI indications with which to fly attitude + power whilst trying to sort out the very numerous ECAM warnings plus alternating "Stall, stall" + overspeed warnings (spurious of course)
Why the crew should have applied pitch up inputs is a mystery to me unless it was a response to a perceived large overspeed but then why leave the power up?


Thank goodness. Someone with A330 with Alt 2 law experience.

Meikleour. If you had been handed the aircraft in Alt 2 law, with substantial lateral imbalance (probably due to a rudder trim change), how do you think the aircraft would have flown then?

[takata]

Do you not mean, "he should [B]not[B] have been fooled by something
Sorry, poorly expressed. I meant consequently, he was fooled by something, as of course, he should not have, being fully alert and experienced.
In fact, I'm thinking that his persistance to do the same mistake all the way down would not find an explanation if his possibly wrong initial reaction was not inverted at some point, when considering all the time it takes and the two other pilots.

Very puzzling. If the THS did not trim down, there was no nose down.
I have no explanation so far and I wonder if this is not the reason why the BEA is refraining from publishing a lot more up to this point. It could take them a very long work to sort all this mess out.

[MartinM]

BlueJet wrote:

Your deduction concerning the PF omits that the 800hr F/O was not qualified to fly in the L/Hseat (see first BEAreport). So for me, it could have only been the 32year old, 800hr F/O who was PF.
your post #908 and #934


This literally confirms my assumption

PF was the Co-Pilot No.2 with 800hrs on an A330.

There is another part in this while dialog which made me assume that PF has less experience, which does not mean he was a bad pilot.

At some point in the CVR transscript it gives me the impression that the PNF knew better in what situation they were.

And from the ranking, it would make sense to me to sit the higher rated co-pilot on the captain seat.

[grity]

Lonewolf 50 Themental and congnitive process, when you are doing this on instruments (which I presume AF 447 crew were, as it was night and the Wx was bad) is to set an attitude in balanced flight and trim to hold that attitude in all three axes. (Plural of axis)

What I was taught and used to teach was to trim nose and rudder first, aileron last, to avoid cross trimming, but such technique is probably model dependent. i understand that this is a target way to continue the flight, trim to hold altitude and speed as before

but with high altitude und UAS is it not much saver due to more aerodynamic stability to set trim for an auto-stable slow descent (flightpath mayby -3 deg?) with not so much trust, lower risk of unexpected climb, searching a lower FL with a major speed range, thinking about the CG ..... is it not much more essential to recover stability than constant altitude

[BOAC]

I am now of the view that the BEA 27 Mai release was bordering on mischievous - almost as if they were looking to see if they could fill PPRune with pages of posts (in which they succeeded).

Why did they miss out the obvious discussion early in the event when the a/c started climbing like a rocket above OPT and probably above MAXALT? Any pilot, even just out of training and on line, would know that that could well be be a one-way ticket to the bottom of the Atlantic, and so where is the "What on earth are you doing" from PNF or "I cannot control the attitude" from PF or whatever? Are we to infer from this omission that
a) It did not happen OR
b) That to tell us is less important than the CVR confirmation that they have duff airspeed, which we already know from ACARS?

What are the BEA playing at?

Last question for AB people - does the reported lack of abnormal law mean a software error here or is it possible the AoA vanes had gone west too? The altimeters/VSIs too? For heaven's sake, was the Pitot heat actually working?

[MartinM]

Another irritating and concerning thing at FL100, when both pulled on the SS simultaneously, I have the bad feeling that they saw the ocean coming close. I think that was just a last try to save something without too much hope.

Back to the technical stuff. AFAIK there is only one SS active at a time. You have to push a button to take over.

Is Alternate Law 2 allowing dual SS input or were they eventually already degraded to mechanical law?

[Clandestino]

All I try is to figure out what made him pull after disconnecting the AP.The right person to answer that would be capt Marvin Renslow as he's the only one known to perform the similar feat. Unfortunately, neither he nor his F/O are able to tell us what were they thinking as their aeroplane pitched up and stalled.

It's debilitating fatigue, suckers!

@BOAC: 1. agree with your view on BEA "report", 2. We'll have to wait for proper report, with full DFDR traces and CVR transcript, to see whether it was simple software mess-up or not 3. pitot heat was almost certainly on - high altitude ice sticks to heated parts, like probes and engine compressors.

[737-NG]

Translating from French means the Captain comes INTO the cockpit but he was no in his seat!

[takata]

Hi BluJet,
Your deduction concerning the PF omits that the 800hr F/O was not qualified to fly in the L/Hseat (see first BEAreport). So for me, it could have only been the 32year old, 800hr F/O who was PF.
Yep, I didn't catch that!
About the rudder, I should have expressed something wrongly but I didn't remember what! Then, my intention was obviously not perfectly understood.
Thanks anyway for you nice comments and informative imput.

[paull]

PNF took over at 2:13:32 + 15seconds, i.e. 41 seconds before the end and perhaps between 7000-7500 feet.
Even if you did all the right things, when is the latest you can act?
How would that differ if the trim was neutral?

Well, this is Tech-Log :)

[Graybeard]

Meikleour (http://www.pprune.org/members/183752-meikleour)

Join Date: Jul 2007
Location: uk
Posts: 161


..If I can make a small contribution to this thread. I have flown the A330 in ALT 2 LAW after a twin ADR incident due to icing conditions. ...



Was this event reported and investigated after landing? Do you have FDR traces that would help understand AF447?

[Capn Bloggs]

Back to the technical stuff. AFAIK there is only one SS active at a time.
Wrong. They sum. Google Airbus Sidestick.

[robertbartsch]

The new report is missing any discussion between the crew related to the stall condition. As written, it appears they did not know for 3.5 minutes that the plane was stalled.

Is that possible?

[sensor_validation]

@Blujet, takata et al.

With respect to who was flying from where do you now challenge the previous 'agreement' between PJ2 and Lemurian summarized in this old post?

http://www.pprune.org/tech-log/449639-af-447-search-resume-part2-71.html#post6452307

[DozyWannabe]

Wrong. They sum. Google Airbus Sidestick.

They sum *if used together*, this is true. But using the sidesticks together is not normal procedure and the systems will notify the crew with a "DUAL INPUT" annunciation.

Correct procedure dictates that upon passing of control from one seat to the other, immediately following or simultaneous with the "I Have Control/My Aircraft" callout, the stick selector button at the base of the stick is pushed. There is no reason to have two pilots on the sidesticks at the same time.

The evidence so far suggests that but for a second or so, this procedure was followed correctly.

@BOAC : I think the BEA "note" was released purely to alleviate the press "leaks" that were proliferating prior to release. Far better for us internet folks to be speculating with a limited amount of real data (which I suspect is all that they had confirmed at the time) rather than trying to sift through a mountain of press twaddle, don't you agree?

[BOAC]

How much height would you need to fix it? - more than that. In my military days it was a given that if you were not starting a successful recovery from a spin (mentioned because of similar descent rates ONLY!) by 10,000 ft you ejected. I suspect it would have been significantly higher for this a/c - 10,000 fpm gives you 1 minute only and I suspect the wings would have come off or the g limited so it would have crashed form 10,000ft. Purely a ball park guess - if a correct attitude change had not been made by 20,000 ft it would be a done deal.

[spagiola]

PNF took over at 2:13:32 + 15seconds, i.e. 41 seconds before the end and perhaps between 7000-7500 feet.
Even if you did all the right things, when is the latest you can act?

We are not told what, if anything, the new PF did after the handover, but the strange thing is that this handover does not appear to have changed much, as vertical velocity at impact (41 seconds later) was still over -10,000fpm.

[BOAC]

a mountain of press twaddle- I have never considered the 'media' here - I am referring to the 'selective' release of inter-crew conversation from the CVR, no doubt, not the media.

[RealQuax]

@MartinM, please! Respecting, that non-pilots and even non-experts can add good and valuable inputs to this discussion: Leave answers to questions about technical subtleties of the A330 to the ones who either fly her or know her intimately.

Me, having 10.000hrs+ on A330/A320 am still stunned about what happened there and am still learning a lot of specificities, which I didn't know yet about my aircraft and the environment, I am operating in.

As Regards those who criticise BEA for their restrictive publication-policy:
Having negotiated company agreements regarding data protection for my fellow pilot-brothers in my company and the association:

I pretty much appreciate the strictly factual way they publish: We see what crap newspapers and self-nominated experts already read out of these factual reports and publications. If it was me involved in such an accident, I would really appreciate that it is the real experts, officially tasked by the text, at least spirit of ICAO annex 13, who get the detailed informations, stick to the facts and publish only those after due consideration which explain what happened in order to help making aviation safer.

[MartinM]

@Captn Bloggs: Thanks for the refresher.

There is no obvious advantage to go on dual-input


During normal operation both side sticks are active and associated signals are algebraically added; however, flight control parameters are not exceeded during dual side stick inputs. The pitch control of the electronic flight control system is a load demand system. In clean configuration, maximum pitch up command is +2.5 G and maximum down command is -1.0 G

[BOAC]

Is that possible? - missed the last 50 pages?:ugh:

[takata]

With respect to who was flying from where do you now challenge the previous 'agreement' between PJ2 and Lemurian summarized in this old post?
No. At first glance, this is how I deduced that the RHS would be occupied by the FO1 (David Robert) and Blujet shed a doubt on the LHS qualification issue.
From what Lemurian already said, based on AF operations, it was almost certain that FO1 would be PF or PNF (with Captain PF) always from RHS and that the FO2 would take the LHS at cruise as PNF when the FO1 was PF.

This was confirmed by PJ2 also:

Yes, understand - the procedures I am familiar with are the same, except perhaps that for the Relief Pilot position, AF uses First Officers who are licensed to sit in the RHS? Regardless, at some point, the F/Os doing the relief for one or the other two crew members will have to sit in the LHS but this would only be in cruise flight. By your statement I believe you mean that F/O's are not allowed to sit in the LHS for takeoff or landing, and that is the way I am familiar with. The Relief Pilot does not sit in either the LHS or RHS until the aircraft is in the Cruise phase of flight...that would be top-of-climb to top-of-descent.

Consequently, the LHS qualification for this part of the flight should not be taken into consideration: PF could actually have been FO1 (Robert) from RHS with FO2 (Bonin) as PNF from LHS, while the Captain was resting.

[EDLB]

Even if you did all the right things, when is the latest you can act?
How would that differ if the trim was neutral?

If the THS would be in neutral position my gues is that they stood a chance even at 7500 feet MSL. The total velocity unfortunately mostly downward was enough to fly and create lift, if they only where able to get the nose down in the flight pass direction. Sort of in the downward part of a loop. Would not even be a real high G maneuver. They where only in a stall not in a spin.
Unfortunately the THS was still in a 13 degree upward position and if it takes a minute for the THS to get to neutral then they had no chance at all even at 15000 feet.

My 2 cents

[rgbrock1]

RealQuax wrote:

Me, having 10.000hrs+ on A330/A320 am still stunned about what happened there and am still learning a lot of specificities, which I didn't know yet about my aircraft and the environment, I am operating in.

Sir. As captain of the A330 have you ever yourself experienced pitot tube icing and, if so, what happend and how did you react?