I guess I have difficulty understanding why the software would find 3.5 minutes of maximum nose-up for the THS perfectly acceptable while all other inputs were going to hell in a hand basket. Was the processor too busy with other interrupts to check the THS or was this combination of input anomalies not part of the decision tree?

@Rob21 - they've released this note as a counterweight to apparent press leaks. It's not even an interim report, just a collection of facts they've managed to prove so far. The reason there isn't more *right this second* is because that is literally all they have.

As was stated earlier, PJ2 was in the air - odds-on he'll be back sometime in the next 24-48 hours.

:eek: So presumably you'd have preferred the software to decide this wasn't allowed and roll off the trim - despite the input from the pilot demanding nose up? You really can't have it both ways now, can you? On the one hand half the crowd here are screaming for the head(s) of the software programing team for removing so much 'authority' from the crew, and here we have a request for the software to "decide" that the crew demand was unhealthy - even if it *was* unhealthy, are you sure you want additional laws and protections? Given that the aircraft has an auto-trim system, it appears to have been operating as expected, given the commands from the crew?

Coming out of Quarantine
 

Presumably, this afternoon, you guys have been discussing the BEA "Update on Investigation". For what it's worth, I've been in voluntary quarantine since just before it came out. As soon as it appeared on the BEA website, I cut myself off completely from PPRuNe, all other media, and any contact with aviation-minded people; and that situation still pertains as I write. I deliberately progressed very slowly through the paper, taking notes and some very long stretch-breaks. There were a number of surprises. Since then, I've been mulling it over, and drafting this.

So what you are about (not/partially) to read are questions and comments arising from my own interpretation of the BEA account, uncoloured since its publication by the wisdom of third parties such as your good selves, and burdened by my limitations. No doubt, I'll have missed many points that, to you, are already "old hat". Nevertheless, here are my thoughts.

QUESTIONS & COMMENTS ARISING

(1) Why no R/H ASI parameter in DFDR? Would it be in QAR? The two recorded ASIs use pitots on the L/H side. (The PF was in R/H seat, presumably.)

(2) "From" 02:10:05, at what stage did the L/H (PNF's) ASI and ISIS ASI readings fall sharply from 275 to 60? After the two stall warnings, or before?

(3) Why did PF allow/encourage/command A/C to climb 3000ft and up to +16 pitch after receipt of stall warnings? One of the pilots had selected TOGA thrust, presumably in response to them.

(4) Why did/does the FBW system in Pitch-Alternate Law continue nose-up trimming of the THS past the stall-warning level of AoA?

(5) As the THS remained at 13 deg UP throughout the descent, is there any possibility that the THS motor stalled during down-elevator inputs? (The BEA "finding" is that "the inputs by the PF were mainly nose-up"[my emphasis of "mainly"].

(6) At about 02:11:04 (at the apogee of FL380), the L/H ASI and ISIS ASI showed 185kts. Was the R/H ASI showing a higher value – possibly due to a blocked drain-hole PLUS the climb of 3000ft?

(7) Quote from BEA: "At around 2 h 11 min 40 [6], the Captain re-entered the cockpit. During the following seconds, all of the recorded speeds became invalid and the stall warning stopped.
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."
[FONT=Verdana][SIZE=2]Why are the AoA values considered invalid below 60kts IAS when the A/C is not on the ground?
(Looks at this stage that: first the PF has mis-controlled the A/C into an inappropriate, steep climb, despite a stall warning; but now the systems are failing to inform him that he has stalled the A/C.)

(8) In the descent, why did neither pilot seem to recognise that the A/C was even in a stall, let alone a deep/super stall? Why was idle thrust selected?

(9) At 02:12:02, several thousand feet below FL350, does the PF's comment that he had no more indications indicate that his ASI reading had only just dropped to a value that he no longer believed? Is it remotely possible that, perhaps unlike the others, the drain hole of his pitot tube had blocked at the same time as the intake? During the initial climb, could he have thought that his ASI was still valid, and that he was trying to avoid an overspeed? [See (6) & (7), above.]

SUMMARY OF KNOWN ENERGY ASPECTS (from BEA text and diagram)

02:08:07 – 02:10:05 (~15nm)
FL350 (about 37000ft amsl). Average GS ~450kts.

[FONT=Verdana]02:10:05 – 02:10:51 (~5.4nm)
FL350, then climbing steeply. Average GS ~420kts.

02:10:51 – 02:11:40 (~4.3nm)
Climbing to apogee of FL380 (about 40000ft amsl), then descending steeply through FL350, all with TOGA thrust. Average GS ~320kts.

02:11:40 – 02:14:28 (Tear-drop track-distance unknown)
Descent from (passing) FL350 (about 37000ft amsl) to sea-level, Thrust reduced from TOGA to ~IDLE by 02:12:02.

Footnote
During the couple of hours I spent reading this short report (including going back and forth), making notes, and referring to system diagrams, I made several unnecessary errors with my printer. Some sheets had to be discarded and fresh attempts made. The flight crew had less than three minutes to diagnose the problem, take action, and recover from any mistakes.

Garage Years


Quote:
At around 2 h 11 min 40 <snip>
The altitude was then about 35,000 ft, the angle of attack exceeded 40 degrees and the vertical speed was about -10,000 ft/min. The airplane’s pitch attitude did not exceed 15 degrees and the engines’ N1’s were close to 100%. The airplane was subject to roll oscillations that sometimes reached 40 degrees. The PF made an input on the sidestick to the left and nose-up stops, which lasted about 30 seconds.
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%. Around fifteen seconds later, the PF made pitch-down inputs. In the following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again.
At 2 h 13 min 32, the PF said "we’re going to arrive at level one hundred". About fifteen seconds later, simultaneous inputs by both pilots on the sidesticks were recorded and the PF said "go ahead you have the controls".
The initial altitude (FL350) and 2 minutes @ 10K/min gets you close to FL100

************************************************************ **

(My new bold) Between 2h13m32s and eor, 2h14m38s, the a/c descended ~two miles.

Just before, with ND, the AoA lessened, the pitots stopped blanking, and an a/s was presented. Still at Stall, the vertical speed was 107 knots, square with horizontal, also 107 knots. This is an AoD of 45 degrees, with full power seemingly available. So at FL100, and these numbers......If this is true, they did not "miss" by much, a recovery...?

Hmmm, maybe I misinterpreted your post. If that is the case, I do apologise.
I understood your post pointing to a non-functioning of attitude indication.
And that is where I get a bit sick and tired reading it time and again, although there is not the slightest indication that IR and thereby attitude information was lost.

And the description of the attitude during descent aboslutely points in the same direction. The attitude was always rather level. In all axis btw.
Ok there was a 40° bank at one point which the pilots tried to correct immediately. This confirms they had suitable attitude information.

Aircraft in IMC where Attitude information is lost arrive in a totally different way.
Absolutely totally different....

My feeling is the thing was seemingly somehow under control, seemingly missing only one piece in the puzzle, the trajectory.
I'm afraid these poor guys never really figured out their effective flight path and speed through the air. Being lost in warnings, seemingly benign attitude and physical sensations and strange instrument indications.

Hello all PPRuNers, I have been following this thread with great interest since tragic loss of AF447 two years ago (and other PPRuNe threads also :cool:). I am not a pilot nor I do have any connection to aviation industry whatsoever, except great passion for airplanes and flying but only as SLF. I must thank to you all as over time I did learn a lot from you and I am very grateful for that.

As I read BEA I was puzzled by THS being in almost full up position for about 3,5 minutes and not changing its position although PF made pitch-down input. Unfortunately report doesn't mention for how long pitch-down input lasted. I took my copy of A330 FCOM (not current one) and found out, please correct if I am wrong, that flight control law could have changed from ALT 2 to Abnormal attitude as angle of attack was greater than 30 deg causing no auto trim available until angle of attack decreases below 30 deg, which according to BEA report did not happen.

Is there any indication in the cockpit when this happens?

1- AoA at 6 degrees and increasing + STALL warning
How is it possible the THS was still trimming up ?
What's wrong here ?

2- As both recorded IAS became consistent again, did the FDs reappear ?

3- BEA, give us all but not that so little !

Chris:

I believe Pitch Attitude protections are lost in Alt1 law and I remember a note about stall protections being 'override-able' in Alt law.

See: A340 - A330 Control: Flight & Laws

About fifteen seconds later, simultaneous inputs by both pilots on the sidesticks were recorded and the PF said "go ahead you have the controls".

Why would he relinquish control ? Is there some dialogue we are missing ?

No acknowledgement from PF.

First sign of PF identifying problem with indications.
PNF acknowledges.

Let's step back.
 

Surely the point in having more than one crew member is so that the PNF can say either:
1- What the fxxx are you doing or;
2- What the fxxx is IT doing depending on whether your are requesting the right or wrong inputs and getting the right or wrong responses from the system.

So, in the Bus, can the PNF or jump seat occupant see what the PFcommanded with the stick? If not, do not expect them to be able to call you on it.

Could someone who flies this confirm the simple question
"Can you tell what the other is doing?"

Frankly I am impressed with the self restraint of a PNF who waited 27k feet before deciding to put hands on. I stop being a team player way before that:confused:

That's a very calm sounding FD considering what's going on. The report of the CPT 'shouting' sounds more like it. Think the FD communications may be a bit too dramatic to release without other context and explanation.

GarageYears; Perhaps you misunderstood my question. I was inquiring whether maximum nose-up for 3.5 minutes was considered acceptable by the software and whether or not the PF should have been made aware of that fact (although he probably had more than enough software output to handle). The pilot should be making the final decision but when a computer puts a flight control in an extreme position for a considerable time (not directly by his command) it might be helpful for him to know what he's fighting.

The data from the DFDR will undoubtedly find its way to a sim in the future. What might the outcome had been if the PF had not touched the sidestick at all and allowed the a/c to ride out the uas. Presumably in that night, the movement of the trim wheel and subsequent lack of movement back would not have been a high priority.

Mr. Optimistic...

The answer is yes. Lots. Without any doubt.

KMD - Do you know of any aircraft in which a computer will override the pilots trim command input in that manner? The computer did not put the flight control in an extreme position, the pilot put the THS there through the continued application of nose up stick. The auto-trim did exactly what it was designed to do and which any Airbus pilot would be expecting.

That begs the question what were the criteria used in the editing process. Clearly they must believe whatever was released presents the event without too much distortion.

kmd:

Yes, I guess I was a little spicy there - apologies for barking! I understand where you're coming from now - I suppose the question is "how does the crew know AT ALL where the THS is pointing?". And as a supplemental to that, should there be some (obvious) indication when the THS falls outside of some nominally "normal" range? Presumably 13 degrees up is not a common demand....?

The thought that occurs to me - and take it as it is, a wild-arsed guess - is whether the Captain managed to regain his seat at that point. We know there were some large rolls on the way down, but whether that would have presented a major obstacle to him doing so either because of excess deck angle or G is unknown at this point.

It also rather scotches the idea that the PF was unaware of any control inputs made on the other side, because whatever he saw, whether it was the occupant of the LHS moving the stick or the "DUAL INPUT" warning, he was immediately aware that the stick was being moved and relinquished control via the switch at the base of the LHS sidestick, just as protocol states.

The level of arcane systems knowledge this crew needed to dig up in the heat of battle in order to solve the riddle it was faced with is frightening. Having the return of the stall warning triggered by an appropriate control input would have been fiendishly difficult to comprehend under the circumstances. So sad that at this late date new knowledge of our craft is still being written in blood.

Folks,

There has been much discussion about what was released today. What is more important, IMHO, is what has NOT been released today. Specifically, the full record of the CVR. There is no question in my mind that there is a whole bunch of communications between the PF, PNF and Capt (when he got back to the flight deck) during that 4 minutes of total confusion.

When I read this report today (and as I reread it again), I did not think for a moment that it includes anywhere near the total cockpit dialog.

More fascinating than ever. There have been some guesses here that are now proven to be very close to what actually happened.

Without attempting or wishing to accuse/blame the pilots - I wonder if what we have here is a tragic misinterpretation of events?

The Captain returned to the cockpit, but did not feel it vital to assume control - this surely suggests that as far as they believed, the situation was under control.?

Could the pitch up commands have SIMPLY been in response to a belief that the descent was due to being nose down - as others have said - to pitch up BELIEVING that the aircraft is stalled is surely the last thing that you would wish to do - conversely if you believe airspeed is OK then you would naturally 'pull up' to arrest descent.

This theory does not take account of what, if any indications the pilots were (or not) receiving - they either beieved the stall warnings (when they came) or did not. It is hard to believe that any pilot would make a control input (even if it is wrong) UNLESS they believed it was the correct course of action.

So the nub is: simple mistake?

Speculation of little value.
 

Dialog and data missing in copious amounts.

Owing to the lack of meaningful disclosure by the BEA, speculation is fairly useless at this time.

Interflug A310 Incident approaching Moscow in 1991 comes to mind.

ASN Aircraft accident Airbus A310-304 D-AOAC Moskva

From GarageYears Link:
and

So with the double ADR fail even Vsw prot would be lost thereby effectively losing basically all stall protection.

It has to be noted that Alt1+2 are Load Factor Demand laws with Auto trim.
So pulling Nose- Up sidestick command would cause Auto trim to trim Nose-up even above the stall.
I do not see anything indicating in the description of the laws preventing that in the situation AF was in.

+1

:ok:

It sure is interesting how the detail drops off after AP/AT disconnect and the zoom climb.

Interflug:

Different type (advanced autopilot, but no envelope protection), different set of inputs entirely.

If I remember correctly, what happened there was that immediately after selecting TOGA, the PF in that case felt that the climb gradient was too steep, so he instinctively pushed forward on the yoke to get the nose down. This led the autopilot to apply up elevator and trim to counteract the yoke force. The PF then re-applied forward yoke pressure and the AP responded again with opposite (nose-up) inputs. The oscillations this caused led to the aircraft pitching up almost to the vertical before control was regained.

What we have in this case appears to be deliberate nose-up commands applied by the PF in response to the loss of speed information - for reasons as yet uncertain. There was no autopilot to counteract those inputs as it had tripped out due to loss of speed data. Everything else that happened on the flight deck at this point is unknown, so all we know for certain is the trajectory the aircraft took. It's obvious that the BEA want to get this right rather than rush a report, so I for one don't see why we shouldn't let them get on with it - those that are complaining about lack of information at this juncture seem to be almost childishly impatient.

Hi,

I understand that
Nevertheless the question was not about the first input .. but about a timing (3.5 minute)
3.5 minutes at 13° climb (about the max obtainable) position for the horizontal stabilizer with many other parameters complety jammed
How manage this by software (protection) is another story
Just a tought.

hello gents
a small question, does anyone know if any of the crew on this unfortunate had any time on older generation types? i dont want to start some sort of pissing contest but i do think the type of experience is relevent- lets not forget 5000hrs on one type is exactly that but 5k on 4 or 5 types must be worth 10k on on type yes or no?


gs

Pitch up
 

Henra, maybe I got it wrong but I understood from the report that the aircraft was in a pitch up attitude of 16º when it reached 38.000 ft.

Level attitude would not be something around 4 or 5º ?

I understand that a good attitude indicator should indicate pitch variations of, at least, one degree. Sixteen degrees on the A-330 attitude indidator is not very noticeable?

Yellow Pen; I'm not in the aviation software business so I'm not familiar with the details of any particular aircraft system. I have some experience in software writing and crisis management. I'm just asking why the software would accept the THS being at its limit for so long.

CapCafre:
A simple question for Airbus pilots:

Until today were you aware that the stall warning could go away if a stall developed to the point that indicated airspeed dropped below 60KT?

And that it would return as you recovered?

Peter H
As far as I can say, the requirements are very different: your car warns you about the external temperature, which would be useless for an airplane flying in an air mass at -50°C and below. The problem seems to be associated with ice particles having a very specific size; if they are smaller, they will be easily processed by the pitot heating system; if they are too big, they will not enter the pitot tube. Thus a suitable warning device would have to accurately predict ice crystals size in a timely fashion, say 20 seconds. With a plane flying at 300 m/s, that requires being able to monitor the size of ice particles having a diameter of a few millimeters as far as 6 km away, possibly through several layers of ice crystals having a different size. I can't imagine a way to do that with the technology currently available.

@ studi (#117 page 6) : Thanks for answering :)

OK so this one, I presume (*) :
"A nose up command is introduced any time the airplane exceeds VMO/MMO to keep the speed from increasing further, which CAN be overridden by the sidestick." (source)
My problem with accepting this hypothesis is that as far as we know, the indicated speed was not exceeding VMO/MMO. In fact, it was the contrary if the last BEA note is to be trusted.

(*) another (low) speed stability function exists, but this one commands a nose down input, not the case here.

Uh oh, I don't agree. They may have made a (fatal) mistake, i.e. not recognizing the situation. Are they to be called "totally inapt" for that? I'm not sure.
What were the conditions ? Why did they seem to loose all confidence in all of their "indications" (after having firstly correctly recognized a problem with the -sole- speed) ?
I don't know and some parts of the story are still missing.

MurphyWasRight's post #119 is for example very interesting with the stall warning on/off/on and the possible consequences of that on the PF's mind.

KMD - Apologies, I thought you were a pilot. I would speculate the software allows the THS to remain at it's upper limit because thats precisely what the pilot was commanding. There's got to be an approved upper limit to THS position somewhere, and if it's approved then having the THS at that position is not necessarily unsafe. There are numerous failsafes to counteract THS runaway or uncommanded movement, but if none of these failsafe triggers have been activated and the pilot is commanding nose up THS movement then as far as the machine is concerned it's situation normal. When an Airbus enters alternate law it's because the computers don't have sufficient information to reliably keep the aircraft within the normal flight envelope protections. I would suggest the more sensible option in that situation is to err towards greater control authority for the pilot.

center of gravity
 

Would that stall happen (the plane having no aft-forward velocity before a "natural nose down") with a "more forward" CG ?

I mean: Wouldn´t the plane go nose down before the a/c aft-forward speed got so low even with the HS trying a "pitch-up" if the cg was properly set ?

• China Airlines Airbus Industrie A300B4-622R, Nagoya Airport April 26, 1994
• Bournemouth Airport, U.K. - A Thomsonfly (now known as Thomson Airways) Boeing 737-300 with 132 passengers on a flight from Faro in Portugal to Bournemouth in England, September 2007
• An Air New Zealand Airbus A320-200, registration D-AXLA (ZK-OJL), test flight GXL888T from Perpignan (France), Nov 2008
• Turkish Airlines Boeing 737-800 at Amsterdam's Schiphol Airport, February 2009

etc etc All aircraft which crashed (or very nearly so) because the pilots failed to realise that the trim had been set full nose up, and couldn't understand why they lost pitch control.

Generally airline stall recovery training doesn't use or show a set up with the trim set this way - it is usually an artificial "OK, we are going to stall ... disengage the autopilot and slow the aircraft down, and stop trimming to allow for the recovery..."

Khashoggi
Don't forget there is a judicial enquiry engaged: maybe communicating too much info about the cockpit conversations could be considered a violation de l'instruction (early disclosure of judicial information) ?

Who knows what was happening in the office (cockpit). Unreliable airspeed indications, stall warnings and watching the altimeter winding down.

My feel is the overwhelming urge to pull up to address the reality of loss of height.... being led to believe they must be in a dive, not dropping like a brick due to being held in a stall.

No time, confused data and three pilots possibly adding to the confusion.
We grieve for all on board.:{