AF447 Thread No. 3
 

Is it time for a new thread ...
http://www.bea.aero/fr/enquetes/vol....mai2011.en.pdf


Link to thread #2

Link to BEA report - English - 27May11

Link to BEA report - French - 27May11

Link to Air France A330 Accident thread, now locked.

This is what I do not understand. Why would the PF pitch up whilst reacting to the stall warning? Or have I missed something?

It s also time for a new server for the bea website. :bored: The current one is smoking.

It would be preferable for you to read the (very small) report before making such silly statements. JT

Like Colgan Air 3407, perhaps?

The French-language version (which is the official one) has some differences from the English one:


http://www.bea.aero/fr/enquetes/vol....mai2011.fr.pdf

Dozy, I would not dare to say that yet, the report is very unclear. It feels as if we are presented only half the information.

AGB, could you elaborate on those differences, my French is very rusty.

@ Penko

The differences are fairly slight, and look to me to be the result of rushing the job of translation and even missing a couple of sentences altogether (not helping the flow of sense at all - the initial English copy, for example, missed the sentence about the first stall warning, with the second warning being the first one detailed.....). BEA have already slightly corrected the English version (as usual) - so, when things have calmed down a bit, I'll take a close look at both and see what, if any, substantive differences remain.

[BTW, I'm no aviator, so my only contribution will be a language-thing, as best I can.]

Thanks AGB, I'll check again tonight.

Hi Takata,

Thanks for your reply. Yes, you're right, the BEA have to keep it factual and proper. I just thought we might learn some more about communication between the pilots, which I'm sure was a bit more colourful than what has been released, and may also shed some more light on what was happening.

All in due course, I'm sure.

Agreed with, the differences noted so far don't change much of the facts.

Anyway, as per the disclaimer, french version is "the good one".
Let's see : (french/english bad[/COLOR]/english corrected)

"L’assiette de l’avion augmente progressivement au-delà de 10 degrés et il prend une trajectoire ascendante."
"The airplane’s angle of attack increased progressively beyond 10 degrees and the plane started to climb."
"The airplane’s pitch attitude increased progressively beyond 10 degrees and the plane started to climb."

"Il y a eu une incohérence entre les vitesses affichées côté gauche et sur l’instrument de secours (ISIS). Elle a duré un peu moins d’une minute."
"There was an inconsistency between the speeds displayed on the left side and the integrated standby instrument system (ISIS). This lasted for less than one minute."
"There was an inconsistency between the speeds displayed on the left side and the integrated standby instrument system (ISIS). This lasted for a little less than one minute."

That's all I found after a quick reading.

Hi,

Air France communication in reaction of the BEA communication 27 May 2011

Communiqués de presse

takata: thanks for the diagram you posted, I am unable to access the BEA report. (Will wait until this weekend when traffic slows down).

Dozy:

I think that it would be a mistake to try too hard to compare this to Colgan Air mishap near Buffalo, on the human side (significantly greater and depth of experience), and because the flight was in the cruise rather than terminal phase of flight.

I appreciate the "why the nose pitch up?" question.

Until after the weekend, I'll be scarce. I wish you all a pleasant weekend.

Type of Weather Radar used?
 

Would anyone be so kind to indicate what type and brand of weather radar was installed in AF447?Don`t forget that even though it might have been incorrect stall recovery by the pilots,how they ended up in a CB IN THE FIRST PLACE,would most likely be ,the blame of the weather radar.To me 10 000 fpm descent, might have been aided with the CB downdraft.

A few posters have commented on the THS movement, and how one idea was the pilots not moving the THS following recovery of the stall.

From my knowledge this is an auto-trim aircraft. Aside from movement of the trim wheel is there any other action that could have been done to manually reset the THS. Unlike a 737 for instance where there is a separate trim switch.

can someone explain
 

Can some professional pilot on this board please explain why any pilot would rationally want to have a nose-up attitude in a stall situation? The report said the pilots were nose-up and with a angle of attack of 35 degrees on descent (double what would cause a stall in my admittedly amateurish C152). I am 29hrs into my PPL, and have always believed/taught/executed that the first thing you do to break a stall is a nose-down (and level wing) attitude. I am a complete novice and really do not understand why/how this happened. It is a real tragedy but as a green trainee I want to learn from this.

can anyone help explain what i'm missing here?

Hi,

How it's possible that the horizontal stabilizer stay in climb position when the PF perform a dive command ?

It's auto-trim until it's not - that function/law can drop out automatically (when HAL/George gives up) and it did at Perpignan.

737 has auto-trim too - again, it can drop out automatically, after putting the trim full up - see Schipol (and at least one other incident).

he thinks he's diving
 

Maybe the reason the PF persists with a nose-up command and then resets throttles to idle is that his instruments tell him he is diving and overspeeding????

Don't have any accurate indication of what parameter, what gage on the instrument panel? :confused:

I'm posting here as the old thread disapeared.

Hi Svarin,
Well... suspiciously not surprising from you by the way you are quoting the report by removing the parts between both "nose down" orders and what happened when this THS trimming changed from +3 to +13 deg. Read it between 0210:51 and 0212:17.

For this part, the report says:
0) Stall Warning
1) TOGA applied (pitch up reaction)
2) PF maintaining pitch up during 30 seconds
3) THS moving from +3 to +13 deg.
4) Pitch increase to about +30 deg (from +10 to +40).

It looks like the PF did not order a nose down command until 0212:17 -- hence, 1 mn 26 sec without any nose down orders... no indication that he tried to override manually the THS either). The only corrective action against the positivie attitude was to select IDLE thrust. Those late nose down action started to reduce the pitch despite this +13 deg THS. (Now, why it stayed frozen here is nonetheless a disturbing issue when those nose down orders were finally applied, but it is the reason why I'm waiting for more info about any use of the manual trim wheel during the previous upset).

But, a VERY selective reading could always make one quite happy with his very "suspicious" findings!

Hi,

In the report chapter "new findings" I read:
The inputs made by the PF were mainly nose-up

I may ask to the pilots in this forum
Is this a normal behavior for recovery from a stall event ?

Hi jcjeant,
No, unless one really want to stay between alpha prot and alpha max with an High AoA protection kicking in Normal Law.
That may be the confusion if one is only trained to low alt, low speed, Normal Law stall recovery, even if both Pilots aknowledged they were in Alternate Law.
Something that need a serious investigation here.

Then why give TOGA power? The report clearly says that the pilot reacted to the stall with TOGA power and a pitch up command. That's the puzzling aspect.

Of course it crossed my mind that for some reason he thought he was diving or gaining too much speed. But then he would not add power.
It just makes no sense.

And it is not a momentary confusion either, it is a persistent pitch up command. There were two other pilots there who did not react to this inconsistent action by the PF which makes it all the more puzzling. I maintain that we are missing half the information.

Hi,

In one of the graph (point number 6) the aircraft made a turn to the right (and not a small turn!)
How that can possible as in the rapport the first PF action is a command to climb with a turn command to the left ...

What I believe the report doesn't say is what the PF instruments were saying.

In the BEA BAC 111 incident in the 70s the crew had both overspeed and stall warnings at the same time - caused by ice in the pitot and static lines.

There was somewhere over Asia a pitot ice problem just after the AF with prang similar instrument indications to the 111.

I read the post from the crew on PPrune.

The skipper stated that if it had been at night they might not have got away with it.

Speaking from my own experience only - If the choice was overspeed or stall then I would lean towards stalling as with a gross overspeed one has no chance to recover.

On early jets - 707 etc - with an overspeed you opened the airbrakes immediately - did it once in wave over the alps after returning from the call of nature and not realizing the ball park had changed.

Assuming there was not a flight control system fault then it seems as though PF didn't understand what was going on.

Which leads to a post I made last week - why don't they fit AOA instruments?

Lost my best friend in a stall which was not identified nearly 40 years ago and eff all appears to have changed.

Well, there is an AOA instrument on board: the stall warning

Hi,

In alternate law .. the trim is in "auto-trim" ?

@ silverline001 : Les Airbus A330 d’Air France sont équipés du radar Collins WXR700X. L’image radar est présentée sur les ND, superposée aux autres informations.
Source : BEA's interim #1 report, dated july 2009.

@ jcjeant : A roll command to the left is not a turn command to the left. Particularly when this roll command seems aimed to counter an aircraft roll to the right...
Are you already trying to find a reason to disregard the last BEA sayings ? :rolleyes:

My emphasis added.

We do not know that the others didn't react, as the report does not tell us either way. The report does note, however, that the PF and PNF both did something a 2:13:28 (1 minute before impact), at which point the PF handed over control to the other. So there does seem to have been some reaction.

Edited to add emphasis.

infrequent flyer: this is a wirehead question in two parts, but I'll ask anyway.

1. What parameters inform (other than sidestick command, or in mechanical back up mode the trim wheels) how the THS moves up or down?

Are the inputs into Pri or Sec that lead to THS commands (which include autotrim commands)
-airspeed?
-AoA?
-a blend/sum of both?

(Are other intertial systems inputs summed in to create the final signal? the (dated) block diagram doesn't get into the wire and signal inputs and loops).

2. As I understand the (dated) block diagram, mechanical mode (trim wheels) does not command the elevators, it commands only the THS.
(If I have misunderstood this, please advise).

Interesting comment on the old training aid I am referring to:

Regardless of pilot inputs, the computers will prevent :
- excessive maneuvres

- exceedance of the safe flight envelope

Another puzzling combination, in addition to the already mentioned ones,is that with the application of TOGA they gave a pitch Up input, and when they applied IDLE power they gave a pitch Down input...I don't get it, it's the inverse of what you might expect: TOGA application makes sense in a stalled condition together with a pitch down input, and IDLE application makes sense in a overspeeding condition where pitch Up might be required. Something is missing or I'm missing something.

Don't know yet - very likely will be part of the detailed technical investigation.

Some possibilities (from my basic understanding of the engineering)

a) because auto-trim has been lost, it's not there in all laws (not clear this is what happened in this case)

or

b) because autotrim went wrong - possibly due to invalid speed input to gain

or

c) because maybe the pitch-down input was brief and/or could be satisfied without moving THS

Remember the pilots went hard pitch up (to the "stops"), then briefly pitch-down, quite possibly the attitude never reached level let alone "dive". BEA states that "angle of attack decreased" following the pitch-down - therefore the it appears the a/c was still responding to pitch controls (and in the right direction, but at what rate?). Shortly after, the pilots comment about reaching FL100, and there are further control inputs - not specified, but possibly pitch up again...

Another consideration:

BEA: "The airplane was subject to roll oscillations that sometimes reached 40 degrees."

From http://www.airbusdriver.net/airbus_fltlaws.htm:

No requirement to change pitch trim for changes in airspeed, configuration, or bank up to 33 degrees.

Not clear what those two taken together mean - maybe autotrim stopped temporaily due to the roll angles.


Note: there is still insufficient information to say the aircraft and flight control systems are in the clear, but equally not enough to show they are to blame. We do know, however, that the aircraft didn't pitch-up and stall on its own - pilot inputs were made. I'll leave those to the heavy pilots to discuss.

I think there is vital information not presented in the report. In particular the position of the thrust levers is only given at a couple of points. We know PF dialled in a lower speed because of turbulence and shortly afterwards AT disengaged. How long after this point did the PF touch the throttle levers to increase thrust? I don't think we are told. Later, after the first stall warning, the engine levers at at TOGA. It would be very useful to see a graph of engine N1 over the whole period.

An explanation was that the right wing stalled, due to lack of speed, and then the PF tried to counter it by rolling to the left, but it is useless or will make the things worse.
Until you are using the manual wheel which is overriding it.
Recorded (and displayed) speed dropped (LHS and stand-by) due to ice, down to 60 kt (false) during one minute and come back to 215 (real), then 185 (real). They heard those stall warnings... no overspeed.

I don't think many have experienced a stall in a turbulent cell before. Recognizing that the aircraft had indeed stalled might have been very difficult at night (as Blind Pew referred to earlier) and with all the alarms going off. (And agreed, the stall warning should have been a primary indication but that was preceeded by other alarms.) Once established in the stalled state, the aircraft still had roll control and may have been fairly stable in that state with no further stall breaks, causing confusion as to the correct action to perform. Nowhere in that report do I see any overspeed reference so why forward stick was not applied is very odd unless the effects of vertigo were so convincing. THS up trim to 13 degrees up (whether done by the system or manually) definitely needs to be analyzed and understood.

Afraid you are crediting me with more detailed knowledge than I actually have.

Short answer - I don't know, but it is one of the questions on my mind too...
I strongly suspect that airspeed is in there somewhere, but what value is used when airspeed is known-invalid, I have no idea.



And the concierge can fly it too... :suspect:

All missing the big caveat "as long as everything works normally" (and actually, even then the concierge quote is rubbish). Drop out of normal law and all that no longer applies.

There's a stall warning at 2:10:51, then the report notes that the stall warning horn stopped at 2:11:40, the clear implication being that the horn was sounding throughout the intervening period. So the instruments could not have been telling the PF he is overspeeding, as the instruments clearly thought he was stalling -- and saying so.

So it seems more likely he did not believe the instruments. Or is it possibile he misinterpreted the protections the current law was providing? If he thought he still had stall protection, would commanding pitch up be a way of trying to tell the aircraft: I don't want to lose altitude, and I'm relying on you not to let me stall?

L@zerdog, what you described looks like a hybrid between a spin and a spiral.
Spin in the goo, in a CB? :eek: Ouch. (EDIT: Capn Bloogs, thanks, not in a cb, but in the goo nonetheless)

Load factor. This is only a load factor law supposed to maintain 1g flight by small adjustement of the horizontal stab trim (and it is only commanded by the PRIMs).

Press can't read English or French...
 

The rubbish has started in the "press" - front of dailymail website (my bold):

So, no one (as there's only one pilot, singular) at the controls, heavy turbulence, engine failure. :ugh: