CogSim

PNF.

PNF said "so, we’ve lost the speeds" then "alternate law [...]".

The airplane began to roll to the right and the PF made a left nose-up input.

initial input: left nose-up
response: The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb.
result: vertical speed, (which) had reached 7,000 ft/min

From 2 h 10 min 05 (4), the autopilot then auto-thrust disengaged and the PF said "I have the controls".

As I read it, PF taking control was a response to AP/ATHR disconnect.

PNF's assessment seems to corroborate the evidence that AP disconnect is linked to loss of airspeed: PNF said "so, we’ve lost the speeds" then "alternate law [...]".

From 2 h 10 min 05(4), 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 1: Only the speeds displayed on the left PFD and the ISIS are recorded on the FDR; the speed displayed on the right side is not recorded.
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 [...]".

The crew seem to agree with your assessment. Their actions and comments seem to ignore the first stall warning here.

Note 2 : In alternate or direct law, the angle-of-attack protections are no longer available but a stall warning is triggered when the greatest of the valid angle-of-attack values exceeds a certain threshold.

Does this mean in Normal Law stall warning is coming from airspeed?

Zorin_75

You don't seriously think that what's in the BEA note is all of the communication in the cockpit, do you?

PT6Driver

JDEE - When PF initialy reduced the VS from 7000 to 700 the aircraft had not actualy stalled. The first stall warnings were false due to the eroneous speed indications. These also led to the AP and ATHR disconects and the reversion to alternate law. Therefore his actions to reduce the climb were partialy sucessfull. If you mean his actions did not unstall the aircraft as I said they were not stalled at this point.

Later on the PF made pitch down movements which resulted in reduced AoA and increased speed - therefore the situation was recoverable.

Cog sim - the computer had nothing to do with maintaining the stall as PF was able to reduce pitch when he chose so to do.

Would anyone care to comment on how many times during their career they have experienced an uncomanded reversion to alt law?

What is the stall speed at FL380, 350, 300, 200, 100 sea level?

Some one mentioned earlier the colgan crash and I have to agree there are similarities in that in both cases the PF would apear to have reacted incorectly to impending and actual stall. - No one plans to stall for real, accidental stalls ocur when we least expect them and are probably most unprepared for them. In order to survive quick recognition of the situation followed by apropriate response.
This in turn derives from the training - if this is inadequate or inapropriate then the wrong responses follow.

Zorin_75

This means in normal law AoA protection is active (which should prevent a stall in the first place).

ask26

I think myself and theav8tr are thinking along the same lines. When it's a long flight, boredom in the cockpit and one overriding thing is there to focus the mind, in this instance the oncoming weather, all the mental ideas you have go into solving that problem.

I think the initial loss of A/P and A/T weren't the problem but a mental desire to get out of the icing layer/weather and certainly to not descend and enter even worse bad weather. Hence the initial response to climb and I believe initial pull-up actions.

Any later pilot responses to a stall warning that may have followed is another matter but I think that is one possible explanation of the primary actions taken by the crew i.e. nose -up input, and is being mistaken here as an incorrect response to the stall.

CogSim

in this statement computer = auto-trim and stall warning disappearing/reappearing below/above 60kt threshold.

What I perhaps should have said is the "computer" as defined above, was making it gradually more difficult for the crew to get out of it.

widmimabi

No that's the normal overspeed Protection but Nobody on this thread is speaking about the proper reaction in case of unreliAble airspeed : pitch and power ( about 2.5 degrees pitch and 85/100 n1) and then switch out the faulty ADR . And surely not climbing 3000 ft at Max FL , trying to stop the airspeed( the faulty one ) from accelerating

promani

"CogSim, good catch on the PF never acknowledging the PNF statements"

With only fifteen snippets of conversation released by BEA from about the last twenty minutes of recordings, maybe it is bit premature to accept that as fact

grizzled

JD-EE and CogSim,

At this stage I wouldn't put much weight on what we know of crew interactions (i.e. one crew member acknowledging or not acknowledging another's words). The words of the crew released by BEA would have been selected to provide some context (not all by any means) to assist us (the public) in understanding the most basic aspects of what happened. The how's and why's are still a long way off.

In the last 10 mins of the flight -- especially the last four -- we can be certain there was a great deal of crew interaction.

CogSim

Thank you. At least the PNF was showing enough awareness to respect the stall warning.

sensor_validation

More questions raised by the BEA report, probably impossible to answer with certainty I'm afraid

1. Would the speed reduction from M0.82 to M0.80 have been completed between 2:08 and 2:10? - if not the engine speed on auto-thrust disconnect could be below that needed for maintaining steady flight. Rudder limit consistent with FL350 and M0.80, but 'about 275 kt' a little high?

2. Is it correct to assume captain would have been PNF in the left-hand seat at T/O, so the PF was in the right-hand seat - and speeds shown on right-hand-side are not recorded?

3. Am I right in thinking that the ISIS displays the air speed from the 3rd pitot? Indicated speed falling low on both left PFD and the ISIS could then be caused by pitot ram ports blocking with drain clear - leaving possibility that the right PFD has frozen ram and drain and will indicate increasing speed with increasing altitude?

4. In the A340 airprox incident an "alpha floor" protection increased engine speed to max even when autothrust disengaged - could this have happened here, possibly at time of first stall warning.

mm43

promani
The reported conversation is "minimal" and IMO only to support the flight control inputs and disclosed aircraft response so far released.

There is much unexplained data dealing with PRIMS/SECS (per ACARS) that may lead to different explanations at a later date.

wes_wall

MM43 quote: I notice a number of regular posters are quiet, which is to be expected

I have purposefully remained silent after reading the BEA report, which is very short on detail, and which unfortunately goes along with what I expected. The French are very careful to paint any picture which might point a finger at National interests. Now, don’t take this as conspiracy related, just factual based on previous investigations. To date, they have only thrown us a bone, factually and judicially correct, but still lacking the meat which completes the actions of airplane and crew that suffered the results. What transpired during the deafening voids in the explanation sing out louder that then statement. More to come I sincerely hope. For those of us who made our living in their seats, and for those still sitting there, can probably build a defendable position on what happen, and why. We can now only hope that the evidence released and reported will be true, and will thereby accelerate the needed corrections. Until then, I fear the airplane will fly under a cloud of doubt, rather than on top where it rightfully belongs.

takata

Hi bear,
I do seem to remember that you had posted a very clear question.
I simply tried to answer it.
If you do think that "30 seconds of full back deflection" is not "continuous back stick", what is it?
Read yourself. You didn't ask for an explanation, but doubted that it was even written in this report.
Barking with dogs after those AF pilots is not in my mentality as I'm also looking for some reasons explaining those unfortunate PF imputs.
My perspective is different than yours as I'm looking for other factors. I would like to know how many trainings this pilot ever did involving a high altitude stall without any protection vs. recovering from a low altitude stall with full flight envelope protection. I guess he did a lot of the later but maybe, never practiced the former.
The danger is obvious as both case could use opposite imputs and a pilot only trained to one form may have reacted instinctively by the opposite move. Full back stick deflection would give Alpha_floor/Alpha_Max in one case and a full stall on the other case. All it would need is a pilot unaware that the protections won't kick in (ie. Perpignan).

GarageYears

[quote]GY, maybe this answers some questions?

Quote:
At 2 h 10 min 16, the PNF said "so, we’ve lost the speeds" then "alternate law […]". Note 1: The angle of attack is the angle between the airflow and longitudinal axis of the airplane. This information is not presented to pilots.

Note 2 : In alternate or direct law, the angle-of-attack protections are no longer available but a stall warning is triggered when the greatest of the valid angle-of-attack values exceeds a certain threshold.

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
This is the important part: "The PF made nose-down control inputs and alternately left and right roll inputs."

The PF did indeed stick the nose down. It didn't work.

This is what caused the climb:

Irrespective of the stall warning that followed the aircraft was ALREADY in the climb that appears to have sealed it's fate. Remember STALL is a function of AoA (are you sure you understand this?).

The pitch-down stick down movements were effective, and may have saved the aircraft if continued however for some reason they were not and airspeed at this time was (presumably) bleeding off due to AoA.

Anyway it's a shame, because I'm loosing respect for some posters here since some fairly basic data points are being glossed over to make some other story match the end result.

BananaAir

No mention of the PICs negligence in leaving the flight deck prior to entering an area of severe CB activity. He had to have known that there was severe CBs in the area was there from his briefing and from listening to other aircraft deviating. Any flight over the ICTZ has a great chance of experiencing monstous CBs!
The fact that the relief pilot and the SIC made attempts to call him back to the flight deck signifies that they were overwhelmed with what they faced.
In hindsight, a 200+ mile deviation left or right of the CBs that night would have saved all the lives on that plane. As to why they didn't do this is anyone's guess.

promani

mm43

Yes I agree with you there 100%. After 2 years BEA only gives a little information, that I think to myself that they are playing games. Just teasing us. But I know that is not true. Just the way they do things.
Pity the US was not investigating this accident. Then all would be revealed, or at least most, whether or not the judiciary was involved. Oh well 2 months to go....

jcarlosgon

After the accident I went through stall, UAS, training in the sim, as per Airbus syllabus.

I was kindly allowed an extra exercise at FL350, about 170 tons, CG around 30%, about one year ago. Pull up from FL350, all 3 ADRs off, kept it at 15 degrees up till it stalled, à la B707/27/37, A310, in gone years.

THS went full back, don’t remember the figure, and sidestick was released, N1 at 85% (A/THR off). The nose came down to about -5 and went back up to +10. Rate of descent was between about 6K fpm and zero, or slight climb (sim is an A330 with PW engines, 85% is slightly above needed N1 for turbulence at M 0.80).

Recovery was done by pushing forward. The surprise, for me, was not the amount of force on the stick to keep that nose about 3 degrees down, in order to get the THS in a comfortable position, about 3 up, at, oops, about 20000’. The surprise was how so long it took. The flight controls never went from ALT to Direct Law.

Shame, I did not try it with full THS up and full forward stick in Direct Law.

Someone posted, my thanks, that stall training is done with stab trim not behind normal (scheduled) IAS for the configuration. That happened to me, even in the military. No problem at the time, no A/P, no autotrim. Problem later, with “moving stabilizer” stall, with A/P ON (B707, 727,737, A310). Same with autotrim aircraft, A320/330, if not properly handled. Check out the OEB concerning Radio Altimeter wrong reading to zero, versus stabilizer trim during go around, as well.

Let’s wait for a more complete report, CVR and flight data.

promani

BananaAir

"He had to have known that there was severe CBs in the area was there from his briefing and from listening to other aircraft deviating."

How do you know what he knew? Are you aware of the flight crew's experience on that sector, and the rotations performed? What the captain knew and what he should have known, may be two different things.

DozyWannabe

@wes_wall : The BEA these days is a very different organisation than it was in 1988. I think it's only fair that we give them a chance to get to grips with the data and release information as they see fit.