There is a F/CTL STAB CTL FAULT procedure.

It basically says to use the Pitch Trim wheel.

One of the subsections reads: If trim is locked above 8 degrees UP, pitch down authority may be insufficient for speed above 180 knots.

That might be an (far fetched) explanation for the initial pitch up. Maybe the PF had a reflex action and applied a kind of windshear/terrain avoidance maneuvre. But after a few seconds it should be clear that that is not working.

I wonder in what state the aircraft was when the AP dropped out. Was it pitching down, or up? That's crucial information.

Thanks for the reply. I agree with your basic answer - although I would not go so far as to say "any aircraft" .

I presume you are AB330 qualified therefore, second question:

The BEA release (which I have now read) seems to indicate that the position of the THS was +13 deg. (nose up).

Question: On the AB330, what is the maximum nose up deflection of the THS? Might it be +13 deg or anything close to that?

No indication that the airspeed on the PFD was inaccurate. Just that after it went out of range, the PFD came back about a minute before the standby. They were close to max cruise alt, got a stall warning and zoom climbed to 38000.
On first reading this doesn't look good!

Not A330, but A320 series qualified. On that type, the THS limits are 13.5º nose up and 4º nose down.

Just to clarify - I wasn't suggesting that's what happened, I was responding to your question as to why a pilot approaching stall would pitch up suddenly in that manner. All I meant by the example was to show that pilots have done it before.

Checkboard

Thanks for the AOA post - never flew the bus.

BOAC
regarding pilot pulling back on the stick with a stall
- seen it but not on an airliner - it is a natural reaction to a falling sensation as is sticking out a hand which leads to a broken wrist.

Re; simultaneous stall and overspeed warnings for the non ATPL holders.
Three pitots and two static sources - depends on timing and sequence of freezing up.

Similar to the Trident crash;
the crew would have faced many simultaneous aural and visual warnings.
it would be very confusing.

The philosophy at the time of the trident crash was that if the stick push fired then dump it as it would be a malfunction.

I can understand with the bus design philosophy of not being able to stall the bus that the crew disbelieved the stall warning.

One question that has not been addressed is whether the horizon on PF side was indicating correctly?

I doubt if we will ever know what the pilots were looking at.

ITCZ 12o heading change - quite normal - it's like flying through a bowl of tapioca with different sized lumps.

hopefully we will one day have 24/7 data links with all parameters including video - I suggested video for sim checks 20 yrs ago and was told why?

Can you tell what the other guy is doing?
 

Simple question, how easy is it with the side stick to know what inputs the other guy is making?

Where on earth has this idea that you can't stall an Airbus come from? It's made perfectly clear during ground school before you even get near a simulator that you can stall the aircraft, and you will stall the simulator during training. What is more of a concern is the full left and nose up sidestick input, something which would not be evident to the other pilots.

Perpignan was a test flight where they tried to kick "Alpha prot-Alpha max" at low altitude with defective AoA probes. They had no time to recover from FL380 like AF447 was. I think I do remember that those test pilots crashing in Toulouse (1994), very close from recovering from a low alt LOS with an engine stopped on test purpose, used manual ths trim. But what would be the point if they did? They would have been authorized and any other pilot forbidden.

Right, of course: it is like having a "direct law" with only manual THS trim available, with a message poping up and saying "Manual pitch trim only"... WTF!!! I won't ever use this cr@p or I'll be fired!
Your position doesn't make sense: it is not "per-design", it is not "forbidden": it is always better not to have to use it (like being in normal law instead of direct)... up to the point that you need it!
Now, how training is performed is a different issue.

I wonder what caused the first stall warning. Was it loss of airspeed or was it G-induced by the pilot trying to recover after the AP dropped out? After that warning they still managed to climb with 7000 feet per minute to FL380...
This was recovered by a nose down command, followed by nose up for the second stall warning.

Hi,

For those who understand french .. it can be interesting ...
A graphical chronology of the events commented in the BEA communication.... (from a french forum)
It's more easy to see the gap in time of no comments at all (shadow zones)

http://i.imgur.com/2HeUa.jpg

interesting similarities
 

One may want to compare this accident with Pulkovo Flight 612 accident:

- in both cases, aircraft stalled at high altitude when crossing severe turbulence;
- in both cases, pilots were perfectly aware of weather conditions and made attempts to avoid flying into the worst;
- in both cases, pilots were mainly pulling the stick (control column in case of Pulkovo 612) instead of applying proper stall recovery procedure until it was too late.

And yet:

- Pulkovo 612 was a Tu-154 aircraft, which is not FBW and is lagging almost 50 years behind A330 in terms of automation;
- One of the Pulkovo 612 pilots was a former aerobatic champion, so he probably knew something about stalls and stall recovery;
- Tu-154s have AoA indicators in cockpit, which provided meaningful and valid information throughout the accident. Also, pitots did not freeze and the airspeed indicators were also valid.

Yet it seems that in both cases pilots either did not recognize that the aircraft has entered fully-developed stall, or somehow failed to apply proper recovery procedure.

One can probably draw a conclusion that such proposed measures as "upgrading the pitots so that they never freeze" or "reducing level of automation" (whatever falls into that category) would not prevent such accidents from happening again.

Just my 2 cents.

Thank you very much, gentlemen (Checkboard, Garage Years, Lonewolf 50).

From your replys and the BEA release, I gather that the THS was within 1 deg. (+13) of its maximum nose up position - and approximately 5 deg. beyond the point at which it could be overcome by full nose down elevator (without changing THS angle). [Please correct me if this is wrong.]

One final question: Is the thrust line of the AB330 such that the application of TOGA thrust will induce a significant nose up (pitch up)moment?

Thanks
 

Wow! Super answers, and the Garage guy's reference is outstanding. Hell, I'm almost ready to try to fly the beast after a few more hours of study, heh heh. As a TV ad says, " it's so easy that a caveman can do it".

I raised the runaway trim issue, as many of us were taught to roll the plane if we had runaway nose up trim. The technique was intended to maintain a reasonable pitch attitude. For nose down, the idea was to reduce power/slow down in order to overcome the elevator trim. Of course those procedures were for "elevators" and not the horizontal stab.

As we try to digest the data and maybe cry a bit, I'll ad lib and add a war story about horizontal stabs. JT Moderator can delete if appropriate, but it explains a few things about many planes' horizontal stab designs.
++++++++++++++++++++++++++++++

So first few months at Hill we had all kindsa celebrities drop by the first Viper unit in the world. One was Chuck Yeager. And we all assembled in the main briefing room and he sat on the stage, feet on the floor, and told us war stories and answered questions. Was a magic moment, I tellya.

He got to the part about the first supersonic flight and a bit of advice from a Bell technician/aero dude. He told Yeager that once supersonic or even close to the mach that they were worried about losing elevator control due to the shock waves. So they had a manual wheel to 'trim" the horizontal stab. He told Yeager that if all else failed, to use that sucker and he might gain pitch control.

Sure enough, above the mach the elevators didn't work very well, if at all. So Yeager cranks the wheel back and forth and regains pitch control. Back below the mach all was "normal". He told us that this discovery was why North American and other folks developing the new jets went to the one-piece horizontal stab. Moving the entire thing as one piece changes the shock wave pressures and the thing acts like a "normal" jet.

Gotta love it!
++++++++++++++++++++

We now return to our regular hypothesizing and second-guessing, heh heh

You're forgetting the caveat "as long as the relevant protections are working", which is a pretty important one.

Agreed - there seems to be considerable confusion here between recommendations made by Airbus themselves versus how those recommendations are filtered down to airline training departments. If what Svarin says is true, then I'd say that's a pretty serious deficiency in that airline's training!

Someone asked me in the previous thread about what I meant by Airbus acknowledging some of the more lurid claims made about the safety aspects of the system in the early days were unhelpful, to which I'll say that their whole training and marketing syllabus changed tack dramatically in the 1990s. Rather than focusing on how easy the aircraft was to fly compared to more traditional aircraft, the focus changed to one of the systems "assisting" the pilot.

Wouldn't a warning help?
 

As someone with no aviation experience, can I ask how much a timely warning of [the likelihood of] UAS would have helped the pilots?

If it would have helped, perhaps more attention should be given to monitoring systems.

If cars can warn of hazardous road-temperatures, might not planes try to warn of ice-crystals.

Regards, Peter

PS The more I think about a "flight engineer's console", the more it seems to complement the strengths of existing FBW systems.
For example, the u/s (but not 'faulty') RA at Schiphol could have been identified by sanity and/or consistency checks, and [manually] taken out of service.

You don't feel descent, only acceleration. You will feel the initial downwards acceleration but once travelling at a steady speed there is nothing to feel.

A question for the AB pilots:

Is there an elevator offload to the stab? By this I mean does the aircraft auto trim in the direction of input to centralise the elevator? and would a prolonged nose up pitch input lead to the stab auto trimming itself nose up?

studi wrote :

No.

Was the stall recoverable?
 

Neglecting for the moment how the aircraft entered the stall, do the A330 pilots here believe such a stall was recoverable, allowing for the THS trim (correctable? ), cruise aft CG, and aircraft weight and altitude?

Possibly recoverable, or routinely recoverable?

Is this ever practiced in sim? ( guessing not, hoping it is )

Am I the only one here thinking that the climb was not induced by the pilots but by some sort of ill functioning protection?

moi aussi.


But the question is what were his instruments telling him?

If the static was blocked he would not have known that he was climbing.

If there was some pitot pressure and he climbed with blocked static then that would have indicated a reduction in IAS.

But it is still hard to believe with a correct horizon that he would pitch up.


Having declared a mayday with a hitherto unknown flight control malfunction on a classic aircraft I have a lot of sympathy for those who have to deal with modern aircraft - just spent two hours trying to get my computer to recognize my printer - unsuccessfully!

Despite AF resent history my money is on more than icing, pilot training and pilot error.

Manual pitch trim (3)
 

takata wrote :

Regarding manual pitch trim, the design and associated training is thus :

Normal law : auto-trim. Dont touch it or fail the test and get fired. 99.9999% of the time for airline pilots. Protections have ultimate authority on control surfaces (hard protections). Eliminated at the start of the accident event sequence.

Alternate law (1 & 2) : auto-trim, which means dont touch it either. No specific PFD, ECAM, whatever, indication regarding manual pitch trim. Rarely trained for. Some protections remain, with a less assertive authority (soft protections). According to factual report, this was how the airplane flew its last minutes. Requires at least one working PRIM.

Direct law : PFD amber warning USE MAN PITCH TRIM. Similar to conventional airplane, direct stick position to control surface position. According to factual information, this law was not triggered. No protection. Rarely if ever trained for, except initial training towards type rating (box-ticking mentality). Requires at least one working SEC.

Mechanical backup : PFD red warning MAN PITCH TRIM ONLY. Basically, sidestick becomes useless. Remaining only manual pitch trim wheel and mechanical rudder, which could give you a reasonable fighting chance depending on actual circumstances. According to factual information, not triggered. Trained once, upon type rating training process (box-ticking mentality). Main condition is all five FCCs lost (3 PRIMs, 2 SECs, all off. Did not happen.)

For the sake of almost completeness :
Other laws : abnormal attitude law, flare law, ground law, ground/air blending laws... These (apart from abnormal attitudes) are quiet transitions, appear every day, and would be perhaps considered subsets of Normal law. No cockpit indication that these sub-laws are triggered. Conditions that activate them can be found in the FCOM. Probably irrelevant to our current matter, apart perhaps from abnormal law but this was not reported.

Assuming that such a significant event as any additional flight law change would have been reported by BEA. Subject to revision as more information becomes available.

I thought it was all going to make sense today...
 

I was wrong. I can't understand how a pilot could pitch his a/c up 2500 feet without realising it. He knew he had UAS but surely he didn't think he had unreliable altitude? 7000 feet per minute upwards after you get a stall warning? What happened in the 11 seconds between the AP disconnect and the pilot's realisation that he had UAS? Did he pitch up, get a stall warning or did he get a stall warning and then pitch up? What was the engine speed at this time? What BEA has done here is worse than useless. They have tried to provide details to quash rumours but by providing less information than is necessary to properly understand what happened. I think they should have either given out everything or nothing.

The only protection I know of that would do anything like that is one that applies to the autopilot when the aircraft makes a sudden vertical maneouvre opposite the direction commanded. If the autopilot was already disconnected by that point then it's unlikely that protection mode would have been commanded.

Of course - that's how trim, and auto trimming works. A constant input on the stick (or from the autopilot) is trimmed out using the Trimmable Horizontal Stab.

The aircraft (with the possible exception of the pitot tubes) was fine - the situation should have been routinely recoverable.

Climbing with blocked pitot results in the airspeed displayed increasing from the speed displayed when the blockage occurred, not decreasing.

In the Perpignon disaster, from the final report:

[emphasis and notes mine]

No - you yourself provide the quote from the BEA that indicate it was initiated by the crew (my bold):

From my read of the above, the pitch up command pre-dates the Stall Warning (though we do not have a well defined timeline to understand exactly the second by second sequencing).

We can see that the initial Pitch Up demand led to the climb, ultimately reading 7000ft/min, prior to the Pitch Down command which slowed the climb rate to 700ft/min, however, it seems by then significant airspeed was lost.

The text that follows in the report seems to be the most perplexing:

At this point we've seen a half-heart attempt to use pitch-down, which may just have been the solution. But that appears to have been abandoned. Pitch up demands then remain, until very late in the sequence, at which point the vertical speed was already at -10,000ft/min with an angle of attack stated to be +40degrees - the stall was full developed and they ran out of altitude.

Re-reading the report is a sad and sobering task. I simply do not understand the initial pitch-up demand. All that seemed warranted was a correction due to the initial right roll? However there is no mention of any throttle demand at the point where the first pitch up command was provided, so presumably airspeed is bleeding off from this moment on. TO/GA thrust was eventually selected 46 seconds after AP and AT disengagement. Too late.

@ studi, Svarin, blind pew and those who think "that the climb was not induced by the pilots but by some sort of ill functioning protection":

May I kindly ask:
- what protection you refer to / could you elaborate on why/how it's been triggered (with AP&ATHR OFF since 2 h 10 min 05, and ALT2 law active since 2 h 10 min 16 at the latest)?
- why/how do you seem do discart the followings?

I prefer not to guess how other aircraft systems work, hence the question.

From this we can deduce that the THS movement was in response to the pilots input and not a cause of the initial climb or final stall event.

You don't feel acceleration but might be sensing the lack of it :

Descending at ~10.000fpm isn't it an aproximate rate of free-fall?
Could you relate this very situation with a 0-G maneuver (on the A300-0G)?

The report says 40° of angle of attack at some point even if pilots are trained to recognize a stall situation (on light aircrafts)
Wouldn't that be disturbing when flying in the "goo" with no airspeed, a pitch up indication, possibly a left bank angle but heading increasing ?

One of the copilot even says to the captain :
"We do not have any valid information..."

With all the workcharge, failures and warnings and wrong infos (speeds) one might become sceptical and "untrusty" over his Attitude indicator.
Moreover, nobody knows what the RH PFD was showing. Even if I tend to think they were both showing more or less identical values

Actually, it's a bit quicker than a parachutist at terminal velocity in free fall - but a parachutist at terminal velocity is experiencing 1 G, not 0 G, (they are effectively lying on a bed of air - but internally feeling the same as lying on a real bed.)

Extraction of actions from narrative
 

An attempt at extracting a logical flow from the narrative. Ellipses (...)
indicate portions I removed for clarity, items such as inline explanations,times and displayed speeds. <comment> are my thoughts.
Bold indicate possible action/reaction chains.

...
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 airplane's pitch attitude <corrected from AOA> 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 airplane was then at an altitude of about 37,500 ft and the recorded angle of attack was around 4 degrees.
<almost regained control?>
...
the stall warning was triggered again. < by the AOA greater 6 degrees?, mentioned later>

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. < as result of sustanined nose up input?>
...
The PF continued to make nose-up inputs. The airplane's altitude reached its maximum of about 38,000 ft, its pitch attitude and
angle of attack being 16 degrees.
...
During the following seconds, all of the recorded speeds became invalid and the stall warning stopped.

<possible "well that worked" reaction by PF who was ignoring displayed speeds at this point anyway? >
...
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 was subject to roll oscillations that sometimes reached 40 degrees.
<falling like a leaf but only sensing side to side not down since steady state,not trusting displayed vertical rate?>

The PF made an input on the sidestick to the left and nose-up stops, which lasted about 30 seconds.
...
(both said) "we have no valid indications". At that moment, the thrust levers were in the IDLE detent
...
Around fifteen seconds later, the PF made pitch-down inputs. Inthe following moments, the angle of attack decreased, the speeds became valid again and the stall warning sounded again.

< return of stall warning was confusing since it coincided with actual improvement? Perhap led to nose up command? >
...
About fifteen seconds later, simultaneous inputs by both pilots on the sidesticks were recorded
<would be usefull to know the inputs and if they matched>
and the PF said "go ahead you have the controls".
The angle of attack, when it was valid, always remained above 35 degrees.

From the BEA report: about 15 sec after 2:10:51 (ie about 2:11:06), the two recorded speeds (LHS and ISIS) are once again the same, and remain the same for the remainder of the flight. To me, this sounds like the pitot probe problem cleared (ice melted or was dislodged?) at that point, and did not recur. The speeds then are noted as becoming invalid again (eg at 2:11:40 just after the captain arrives, until 2:12:02 + about 15 sec), but the report pointedly notes that they would do so whenever they fall below 60KT.

That's over three whole minutes in which they apparently had functioning speed indicators (a little after 2:11 up to impact at 2:14:28). They also had plenty of altitude, as this is about the same time they reached their maximum altitude of 38000.

By then the THS is trimmed nose up 13 degrees. Between 2:11:40 (when we are told N1 is almost 100%) and 2:12:02 (when we are told throttles are already at idle and N1 is 55%), the throttles were retarded.

At about 2:12:02+15, the PF commands pitch down, pitch is reduced, and speeds become valid again (ie climbing above 30KT).

Impact didn't occur until over whole two minutes after pitch down was commanded. Apparently not enough pitch down as the aircraft remained nose high (AOA at least 35 degrees), descending very rapidly. Did the PF stop pitching down? Or was he continuing to pitch down, but failing to drop the nose because of the up trim on the THS? The report says nothing about pitch commands after 2:12:02+15 except to note that, in general, pitch commands were "mostly up" after AP disengagement.

To my mind, it's those last three minutes, and particularly the last two, that need to be explained. There was an initial upset, and a reaction to that which led to a stall, but by about 2:11 the speed indications were apparently valid.

Was the crew confused or fixated on the wrong problem? If we knew more about what they were saying, it might be possible to figure it out. I can't imagine that nothing was said in these whole of the last two minutes beyond the brief exchange noted at 2:13:32.

Did the resumption of the stall horn once the speeds once again become valid after commanding pitch down (at 2:12:02+15) confuse the PF into thinking he was doing the wrong thing?

Perhaps it might also be worth noting that by 2:11:40, the aircraft was already dropping at -10000fpm, and that it would have almost exactly this vertical velocity when it hit, some three minutes later. This suggests there may have been little vertical acceleration during this period, perhaps lulling the pilots into thinking they were in stable flight? Yet they did note that they were dropping through FL100.

Lots of things are just not adding up.

[edited for grammar and to correct error on min speed at which speed is considered invalid; 60KT, not 30KT (see BEA report, note at bottom of p.2 of French version]

Murphy, as you broke that down, you end up part way through the sequence with this progression:

"I push the stick forward, I am now stalled again, I need to pull the stick back" which is a valid response in inverted flight.

:confused:

In re roll oscillations: is that characteristic of an AB in a stall, or a symptom of the usual auto trim/auto correct dampening functions dropping off, or a combination of the latter and a pilot seeking a stable condition?

(Recalling SAS off flying and how sensitive it is to inputs ... )

AoA/Pitch
 

Corrected by BEA to "The airplane’s pitch attitude increased progressively beyond 10 degrees (...)" (See current PDF)

LW50:
Interesting point, could the pilots have been -that- disoriented?
(I have no knowledge/opinion either way.)

If I parsed the narrative correctly (would much rather look at the DFR data) the stall warning returned when the speeds were again deemed valid by the system.

I am not a pilot, but have some knowledge of vectors and physics.

It seems to me that the critical fact is that the plane was pitched up, but the pilot input was to command nose up. It it possible that this incongruous situation was the result of a huge discrepancy between pitch (which is relative to the horizon) and AoA (which is relative to the apparent wind vector)?

If, for example, the plane was caught in a draft of wind from below (which might explain some of the altitude gain), wouldn't the AoA indication be negative -- and the pilot's response be to command nose down -- even while the plane's pitch was positive? Or is my thinking garbage? Don't worry about being harsh with me, I don't claim to be an expert. :)

Quick question: on what basis does the BEA reports that the speed measurement became valid again at 2:12:21 ?