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-   -   AF447 wreckage found (https://www.pprune.org/tech-log/447730-af447-wreckage-found.html)

DouglasFlyer 31st May 2011 11:43

jcjeant is right!
Sorry for the wrong expression: should have read "only controlled" instead of "only controllable".
Manually moving the pitch trim wheel overrides the auto trim.

Patty747400 31st May 2011 11:50

Quote from Air France:

"The crew, made up of three skilled pilots, demonstrated a totally professional attitude and were committed to carrying out their task to the very end and Air France wishes to pay tribute to them."

I'm not ready to put all the blame on the pilots. However, a statement like this at this time makes me think they have hired "Bagdad Bob" as their press officer. Is this just French arrogance or do they know something we don't?

Elledan 31st May 2011 11:57

On a Dutch news site here ( Inmiddels 77 lichamen uit ) the following claim is made (translated into English):

The pilots wanted, thus becomes clear from the 'current conclusions' from the investigation into the two black boxes of the plane, to fly over a lightning storm, but were prevented from this because it wasn't possible due to the temperature to fly to that height.
Reading this kind of surprised me, as I didn't have the impression that they wanted to fly over the storm, but it would explain why they suddenly went into this steep climb.

000tfm000 31st May 2011 12:01

Apologies: I posted essentially the same message as this a bit later (below) - not having noticed that there would be a delay pending moderation.

Zorin_75 31st May 2011 12:08


"The crew, made up of three skilled pilots, demonstrated a totally professional attitude and were committed to carrying out their task to the very end and Air France wishes to pay tribute to them."

I'm not ready to put all the blame on the pilots. However, a statement like this at this time makes me think they have hired "Bagdad Bob" as their press officer. Is this just French arrogance or do they know something we don't?
Whatever the investigation will reveal, there can't be any doubt whatsoever that these men did everything they could to save the plane. Now the task should be to find out why that wasn't enough. Not to put blame but to learn.

jcjeant 31st May 2011 12:10

Hi,


I'm not ready to put all the blame on the pilots. However, a statement like this at this time makes me think they have hired "Bagdad Bob" as their press officer. Is this just French arrogance or do they know something we don't?
When I read the Air France statement .. I ask myself (already posted)
Why Air France will make such statement ? .. as maybe the final report will go in a contrary way .....
Maybe they know more on the CVR-FDR that what we know ?

AAIGUY 31st May 2011 12:12

had they done NOTHING or atleast followed the Unreliable Airspeed Abnormal Checklist and turn to the GPS page for speed and Alt..

No they weren't hero's. If (and I say) the BEA report is correct they were idiots.
Like the A340 crew in YYZ

Patty747400 31st May 2011 12:18

"there can't be any doubt whatsoever that these men did everything they could to save the plane."

So you mean sitting with the stick pulled fully back for 3,5 minutes while you are descending with 10000 fpm demonstrates a "totally professional attitude"?

What I'm saying is, if AF know more than we do, they might have a point. But, from what we know so far... absolutely not.

Just as I won't put all the blame on the pilots before I have the final report you should be careful to completely clear them of responsibility. Can we agree on that?

000tfm000 31st May 2011 12:34

Stall warning system a contributory factor?
 
To me as a lawyer with an interest in aviation safety, the preliminary report implies that the design of the stall warning system may have been a major contributory factor in this accident.

The PF was confronted with conflicting signals as well as degraded instruments. Nevertheless, at quite an early stage, his inputs commanded nose-down pitch. He appears successfully to have initiated a recovery. What he needed to do, was to develop this response further.

However, the stall warning system did not recognise this. It did not encourage the PF to develop his solution further. On the contrary, it sounded a stall warning. This is essentially because it could not reward the improving trend which the PF had initiated: it could only recognise the threshold above which the stall warning should be available (<60knots = stall warning unavailable; >60knots = stall warning available).

A correct interpretation of the stall warning would possibly have been difficult in any situation. Particularly in the difficult conditions which must have prevailed at the time, the PF may well have inferred that there was a causal connection between the stall warning and his most recent command: ie, nose-down. Naturally, he would have wished to reverse the cause. So he would command nose-up instead.

What is worse, the PF would now have learned by experience that commanding nose-down pitch would "cause" a stall warning. He would have been reluctant to try it again.

Therefore, my tentative view is that the stall warning at this stage in the attempted recovery gave precisely the wrong message to the PF. It may well have been an important step in the "critical path" of the accident.

I think we should not rush to blame the pilots: the term "pilot error" sometimes disguises the degree to which "human error" has been induced by automatic systems.

CJ Driver 31st May 2011 12:50

Late but hopefully useful
 
This thread is galloping forwards so fast that I'm replying to something three pages ago, but it was only a few hours ago, and it needs answered because it is another daft blind alley.

Someone said:

I can't believe anybody would certify an airliner that is stalled but the stall warning mutes because the pitot static system senses less than 60 knots. That is nuts.
I think you will find that is completely normal, and even a microsecond of thought will tell you why. Think "parked on the taxiway". There's a strong chance the wing is fully stalled, but we'll supress the stall warning until we've got some speed up, thank-you.

Zorin_75 31st May 2011 12:58


So you mean sitting with the stick pulled fully back for 3,5 minutes while you are descending with 10000 fpm demonstrates a "totally professional attitude"?
First of all paying tribute to those men is not a matter of arrogance but of decency.
No, what I'm saying is at that point, to them pulling on that stick appeared to be the best way to save the plane.
Considering what we know now (which is, as has been said numerous times, still very little), that was likely not the case and probably the final report will prove us, sitting in our comfy chairs, right and those men who died that night wrong.
But what then? It's so easy to shrug it off, label them as idiots and go back to business, while learning from their mistakes will be work and will cost money. But I think we owe it to them.

jackx123 31st May 2011 13:01

Patty: agree totally.

as another earlier post pointed out. At 350, flight controls neutral and correct trust setting should get you out at lower alt with faulty IAS. not rated on 330 but sure as hell works for most other tubes with wings that I flown in the past.

Capn Bloggs 31st May 2011 13:14


Originally Posted by CJ Driver
Someone said:

Quote:

I can't believe anybody would certify an airliner that is stalled but the stall warning mutes because the pitot static system senses less than 60 knots. That is nuts.
I think you will find that is completely normal, and even a microsecond of thought will tell you why. Think "parked on the taxiway". There's a strong chance the wing is fully stalled, but we'll supress the stall warning until we've got some speed up, thank-you.

Ever heard of a squat switch?

ATC Watcher 31st May 2011 13:16

Great Post Zorin_75.
You're absolutely right.

Zorin_75 31st May 2011 13:16


the preliminary report implies that the design of the stall warning system may have been a major contributory factor in this accident.

The PF was confronted with conflicting signals as well as degraded instruments. Nevertheless, at quite an early stage, his inputs commanded nose-down pitch. He appears successfully to have initiated a recovery. What he needed to do, was to develop this response further.

However, the stall warning system did not recognise this. It did not encourage the PF to develop his solution further. On the contrary, it sounded a stall warning.
First mention of a nose down input is here:

2 h 10 min 16:
(...)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) (...)


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.(...)
Around fifteen seconds later, the speed displayed on the ISIS increased sharply towards 185 kt;it was then consistent with the other recorded speed.



So IAS was well above 60 kt at this point. The stall warning simply meant they were going into a stall.
The only time a reappearing stall warning due to nose down / increasing IAS is mentioned is much later:

At 2 h 12 min 02, (...) 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.


But the report doesn't say anything at all about the PF's reaction to that warning.

JCviggen 31st May 2011 13:22


What is worse, the PF would now have learned by experience that commanding nose-down pitch would "cause" a stall warning. He would have been reluctant to try it again.
That is probably true on a basic pshychological level...but shouldn't a pilot have a bit more of a grasp on the physics of flying? Why would lowering the nose in this case cause a stall warning? And even without the stall warning sub-60kts, the altimeter was still winding down in spectacular fashion with engines at full and the nose up for a good amount of time. I know about heat of the moment and all that but its amazing the amount of time that passed without the full stall becoming apparent to them.

cwatters 31st May 2011 13:35

@ costamaia



@CWatters

Quote:
Why wasn't full power applied?

Wasn't it?
From the BEA 27 May report (http://www.bea.aero/fr/enquetes/vol....i2011.en.pdf):
"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 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%."
I meant later when they still had a high rate of descent..


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.
...although I admit it doesn't mention what they did with the throttles after that.

fboizard 31st May 2011 13:40

BEA report unclear
 
I am French, so I have the happiness to read the BEA report in the text.

It is very confused and incomplete. Don't trust it too much and don't exhaust yourself trying to make a coherent theory from it.

For example, there is not enough informations to understand why the A330 climbed and stalled at 38 000 ft :

> the pilot gives «ordres à cabrer» (pitch-up orders)

> then the PF gives «ordres à piquer» (pitch-down orders)

and then «le PF mantient ses ordres à cabrer» (the PF keeps giving pitch-up ordres)

Obviously, there is something missing here : when did the PF resume his pitch-up orders after having tried the pitch-down orders ? And why ?

The whole report is like this : ill-phrased, hardly understandable and lacunar.

Be careful when you use this report : I thing some very important informations are missing (or withheld ?).

cwatters 31st May 2011 13:47


Its probably been said before in the last 55 pages but,

If you lose sensible airspeed and altimeter indications, disregard all and fly attitude and zero bank angle for normal cruise flight with relevant manual throttle setting. Been there, done that.

Try it in the sim.
Does that work if you start in the stalled condition with high rate of descent and 40 degree AOA? Will it accelerate out of the stall at cruise throttle?

Graybeard 31st May 2011 13:49

Optional, or Mandatory
 
Shogan1977, from Der Spiegel:

Quote:
The manufacturer Thales was well aware of the catastrophic consequences of a failure of the speed sensors as early as 2005. At the time, the French company concluded that such a failure could "cause plane crashes."

A total of 32 cases are known in which A330 crews got into difficulties because the speed sensors failed. In all the cases, the planes had pitot sensors from Thales, which were significantly more prone to failure than a rival model from an American manufacturer.

But none of the responsible parties intervened. In 2007, Airbus merely "recommended" that the sensors be replaced. Air France took that as a reason not to carry out the costly work -- and it even got official blessing for doing so. The European Aviation Safety Agency wrote that it currently saw "no unsafe condition that warrants a mandatory modification of the Thales pitot tubes."
Money is in play here, I'm sure. Typically, if the component maker or airframe builder make a Service Bulletin mandatory, they pay for it. If the SB is optional, the airline pays. I've known airlines who refuse to pay for SB that are to correct defects, regardless.


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