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AF447 final crew conversation - Thread No. 1

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AF447 final crew conversation - Thread No. 1

Old 20th Jan 2012, 16:06
  #1101 (permalink)  
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Actually a 'PIO' has little to do with the aircraft and a lot more to do with the 'P', and hence its name. I don't think 'writing it up' will work!

"I induced a PIO - aircraft u/s"
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Old 20th Jan 2012, 18:43
  #1102 (permalink)  
 
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Originally Posted by A33Zab
They...Airbus... offered the BUSS option even before AF447.
But the BUSS has not been designed to exit a fully developed stall. BUSS is not the solution either to unreliable speed indication above 25000 feet. Would the AF447 crew have attempted to select all ADRs OFF passing FL250 in order to activate the BUSS ... ? What would have been the BUSS indication ? Is it designed for 45 deg of AoA ?
I have some doubt about the BUSS ... but I have never experienced it in the simulator.
A more simple AoA indicator could be a better option maybe ...
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Old 20th Jan 2012, 19:39
  #1103 (permalink)  
 
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I once saw a chap 'PIO' his glider into the deck at Gutersloh right beside where I was standing
Glider PIO's can be due to CG out of range, eg someone accidentally leaving a ballast weight in or in my case on one flight, a loose trim tab that moved every time I moved the elevator. Too fwd a CG can lead to you running out of elevator authority and too rear can lead to too twitchy elevator!
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Old 21st Jan 2012, 00:13
  #1104 (permalink)  
 
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Originally Posted by CONF iture View Post
I have some doubt about the BUSS ... but I have never experienced it in the simulator.
A more simple AoA indicator could be a better option maybe ...
A simple AoA indicator already is an option, I believe. Just not one that many airlines seem to specify.

And if the final report recommends AoA inidcator be mandatory, it won't be the first to do so. Maybe one day the regulators will act on it.
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Old 21st Jan 2012, 01:45
  #1105 (permalink)  
 
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@stepwilk
Quote:
the first post to respond to it said it had appeared here many times (?)

Why the question mark? It -has- appeared here many times. Read the thread.
I have, I did. All of them. Thoroughly.
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Old 21st Jan 2012, 02:21
  #1106 (permalink)  
 
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BUSS - BackUp Speed Scale

But the BUSS has not been designed to exit a fully developed stall. BUSS is not the solution either to unreliable speed indication above 25000 feet.
As you said the BUSS is activated by switching off all 3 AirData sources, this action will also force the flight control Alternate Law.
Its advised to not use it above FL250 because theres the assumption there is sufficient altitude to recover an UAS.

From the FCTM:
‐ At high altitude, typically above FL 250, the cases of unreliable speed situation are mostly a
temporary phenomenon: They are usually due to contamination of the pitots, by water or ice,
in particular meteorological conditions. In-service experience shows that such a contamination
typically disappears after few minutes, allowing to recover normal speed indications.

Would the AF447 crew have attempted to select all ADRs OFF passing FL250 in order to activate the BUSS ... ?
It comes with an ECAM drill...then the question is:
Would the AF447 crew had followed the drill passing FL250?

What would have been the BUSS indication ?
The yellow AOA indicator line [Current AOA] would have been at the bottom of the SLOW side of the scale.



Is it designed for 45 deg of AoA ?
It is based on Inertial data instead of AirData and always available as long IRs not failed, since the AOA is now also available when AirData is not (e.g. CAS <60Kts) the stall warning would not have silenced.

I have some doubt about the BUSS ... but I have never experienced it in the simulator.
A more simple AoA indicator could be a better option maybe ...
Maybe, but the AOA limit (in Alternate and Direct Law) is a function of MACH, Speedbrake and Flap/Slat settings.
Then a crew needs to know its limits for MACH/CONFIG or the bug needs to be automated and that will make it more than just a simple indicator.

BTW The BUSS is not adopted for use of Speedbrake
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Old 21st Jan 2012, 07:29
  #1107 (permalink)  
 
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Far simpler is a table in the QRH to cross refer to and select AOA in the AIDS ALPHA parameter call up menu.
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Old 21st Jan 2012, 08:28
  #1108 (permalink)  
 
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RE:

a. the stall warning trigger threshold "cooks off" at a LOWER AoA and remains silent at deep-stall AoA's (i.e. any attempt to stick fwd [and thus lower the nose] triggers a quite deterrent aural stall warning – so any prudent pilot unstalling actions are thwarted).

>>Bonin: 'But I have been pulling back on the stick all the way for a while.'
>>Dubois: 'No, no, no, don't climb.'
>>Robert: 'Ok give me control, give me control.'
>>Dubois: 'Watch out you are pulling up.'
>>Robert: 'Am I?'

Perhaps "prudent pilot unstalling actions" are thwarted by the automation, but I don't see any prudent pilot unstalling actions here TO THWART!

Also, although I fly Boeing and am thus not familiar with the Windows Vista flight control system of more "advanced" aircraft, I wonder: did the pilot have authority over pitch trim, or was that removed from his crib like a dangerous toy also?

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Old 21st Jan 2012, 08:34
  #1109 (permalink)  
 
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Originally Posted by ChrisJ800 View Post
Glider PIO's can be due to CG out of range, eg someone accidentally leaving a ballast weight in or in my case on one flight, a loose trim tab that moved every time I moved the elevator. Too fwd a CG can lead to you running out of elevator authority and too rear can lead to too twitchy elevator!
The usual cause of PIO landing a glider is insufficient airbrake.
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Old 21st Jan 2012, 10:56
  #1110 (permalink)  
 
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Originally Posted by A33Zab
It is based on Inertial data instead of AirData
Is that inertial data + raw AoA, or does the BUSS not use AoA vane angle at all?
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Old 21st Jan 2012, 14:35
  #1111 (permalink)  
 
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A33Zab,

First, thanks for the documentation as the information on the BUSS is IMO seriously insufficient. A video animation for anyone who operates such equipment should be readily available ...

If I get you right, the green - red scale is fixed on the PFD, green always in the middle. Only the Current AoA line is moving.
Now, is it possible for the AF447 scenario, that the Current AoA line would not have been visible at the bottom of the SLOW side of the scale as the CAS was already well below VLS, and the red lower area is for a CAS above VLS ?

Its advised to not use it above FL250 because theres the assumption there is sufficient altitude to recover an UAS.
The QRH leaves no latitude at all - It is a 2 cases scenario - Either you're above FL250, either you're below.
If above, you're good for a 4 pages QRH procedure ...
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Old 21st Jan 2012, 15:03
  #1112 (permalink)  
 
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@HN39:

For the BUSS it is Inertial Data + the AOAi (Indicated AOA) which IMO is identical as what you call the 'Raw AOA'.

Last edited by A33Zab; 22nd Jan 2012 at 11:05.
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Old 22nd Jan 2012, 02:31
  #1113 (permalink)  
 
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>>Bonin: 'But I have been pulling back on the stick all the way for a while.'
>>Dubois: 'No, no, no, don't climb.'
>>Robert: 'Ok give me control, give me control.'
>>Dubois: 'Watch out you are pulling up.'
>>Robert: 'Am I?'
All three were clueless. Bonin flew that plane into a stall condition, not on purpose but it doesn't matter really except that he did. Robert became more preoccupied/obsessed on giving the controls back to the captain instead of taking charge of the airplane and the situation. The captain arrived too late and the plane had already stalled and time-left was fast becoming shorter.

I can accept that only the captain had received the training to escape stall conditions but that doesn't mean the other two didn't know/hear/read/test about them. How can you get an air pilot license without completely know about airplane stalls? How could they possibly ignore the First time "Stall + Calvary" warning? Not the second or third one or even less the 70+ time. How one pilot, after hearing the warning for the first time asked: What is that? and the other one didn't reply?

How do three professional pilot lose sight of altitude until 28,000ft were gone-by? Then another 6,000ft? Then, at less than 4000ft, one of them realized the possibility of death.

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Old 22nd Jan 2012, 07:53
  #1114 (permalink)  
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I can accept that only the captain had received the training to escape stall conditions
- I sincerely hope you are wrong!
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Old 22nd Jan 2012, 23:37
  #1115 (permalink)  
 
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Every airline I flew with all pilots knew how to fly as well as the captain. I know things have gone downhill but hope not too far..
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Old 22nd Jan 2012, 23:49
  #1116 (permalink)  
 
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Not being able to tell your crew to push the SS down because you are stalled is an obvious fix but they probably wouldn't have known how to do it. They seemed to not understand the fundamentals of stall recovery. Push down. Works every time. At least for me.
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Old 23rd Jan 2012, 00:56
  #1117 (permalink)  
 
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Originally Posted by A33Zab
The yellow AOA indicator line [Current AOA] would have been at the bottom of the SLOW side of the scale
I was looking at the FCOM and things are described a bit differently :

Actual Speed Reference Line (Yellow) :
This fixed reference line next to a yellow triangle, indicates the aircraft’s current speed.
So that yellow line stays in the middle and probably and hopefully the GREEN area with the target speed (GREEN triangle) remains visible at the top of the scale whatever the current stall speed/AoA is.

For the Red SLOW area :
This red area indicates the speeds that are lower than the stall speed.
Those checked on the 380 probably know more as the BUSS seems to be standard equipment.
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Old 23rd Jan 2012, 01:12
  #1118 (permalink)  
 
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bubbers44 -
Not being able to tell your crew to push the SS down because you are stalled is an obvious fix but they probably wouldn't have known how to do it. They seemed to not understand the fundamentals of stall recovery. Push down. Works every time. At least for me.
Hey, bubbers44.....maybe they were from the "school" where they were taught that if you pull back, you go up, and if you pull further back, you go down !!!
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Old 23rd Jan 2012, 05:09
  #1119 (permalink)  
 
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Hey, bubbers44.....maybe they were from the "school" where they were taught that if you pull back, you go up, and if you pull further back, you go down !!!
No, obviously they were NOT from that school. But they should have been.
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Old 23rd Jan 2012, 12:17
  #1120 (permalink)  
 
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Okay, first the disclaimers; not pilot – engineer. Not aeroplane engineer – CT/MRI Scanner engineer/SLF so, comparable technology. Yes, I have read most of the threads devoted to AF447, but they keep overtaking me. Although fascinating, I have to say it’s a damned laborious business for an outsider, because of the inevitable TLAs (three letter acronymns).

My sources are almost exclusively what I have read on here and only from those whose posts appear the most authoritative. No newspaper or media reports were used in the making of this post, which, is in the form of either unresolved thoughts or questions arising from information read here. I suppose I’m really just trying to summarise what I have understood from this mass of data and in the hope that it will help others.

I was looking back at a draft I wrote to contribute to the first AF447 thread (but never did) when weather, the avoidance of it and the location of the wreck were the main topics, as so few facts were then known. And, my goodness, how this and other threads have moved on? Now, a remarkable three years later, the Flight Data Recorder and the Cockpit Voice Recorder have been found, against all expectation, and analysed to reveal what appears, to this Engineer SLF, a frankly terrifying set of circumstances.

Through choice or lack of planning, AF447 flew – at 35,000ft – near to a large, complex storm cell that other aircraft had avoided. This, directly, lead to icing of the pitots and temporary loss of ‘Air Data’ – information from the air outside – which meant loss of accurate air speed indication.

This condition lead inevitably and almost immediately to the autopilot and autothrottle releasing the aeroplane into the hands of the two F/Os remaining in the cockpit after the Captain went off for his legal, though given the circumstances of weather, ill advised, rest break. Nevertheless, an ‘Unreliable Air Speed’ condition was never formally declared in the cockpit and no ‘procedure’ instigated.

Although the aeroplane had been straight, level and surprisingly stable – given the proximity of the storm – concern about overspeed was immediate and the PF (the least experienced F/O) throttled back and pulled back on the side stick. This instigated an almost 2000ft/min climb which continued – with the speed dropping all the time – to circa 38,000ft.

The PNF (the most experienced F/O) meantime was trying to make sense of what was happening as air data intermittently became ‘valid’ then ‘invalid’ again. All this time PF was pulling back on the sidestick almost, but not quite continuously. At or near the top of the climb, with speed bleeding away quite dangerously, PF hit TOGA – basically firewalling the throttles to a pre-set power output – which always pitches the aeroplane nose up unless counteracted, adding to the already dangerous Angle of Attack. The speed thus reduced still further and, with the stick still pulled back, the wings stalled and the aeroplane began to descend, very nose up.

PNF became very concerned, but equally confused as to what was happening, even though the altitude and vertical speed indications were working on his side, although ASI was not always valid. The stall warning operated, but neither pilot acknowledged it and no obvious action was taken immediately. As the speed dropped still further – below 60kts? – the stall warning stopped because it had fallen below its ‘authority band’. When PF several times released the sidestick, the aeroplane tried to level out and the speed temporarily rose, causing the stall warning to again sound as it re-entered its authority. This warning again drove PF to pull back on the sidestick, confusing PNF still further, if possible.

When the Captain returned from wherever in the aeroplane he had been, he elected to take the centre seat, not the LHS controls. He asked a number of questions, the answers to which served only to confuse any readings he might have taken from the instruments. During this time, PF was still pulling back on the sidestick and it was pretty much in this state that the aeroplane hit the sea at between 7000 and 10,000ft/min.

Apart from the initial blocked pitot/ Air Data failure – a condition experienced by 36 other aircraft of the same type – there was no other failure of an aircraft system.

I am no pilot, although I have flown light aircraft and have had a deep interest in aeroplanes and flying since I was eight, but even I know that pulling back continuously on the elevator control will, eventually kill you. I remember being deeply impressed by the low speed pass into steep, turning climbout of an early FBW Airbus at Farnborough, because I knew then, that to do what that pilot had just done in almost any other aeroplane, would certainly kill him. But I also know doing that at low altitude is quite a different thing from doing it at almost the maximum height for the weight.

In my really quite humble opinion, the Captain did not assert enough clear thinking authority and was quite ill advised to leave the cockpit when he did, but did not cause the accident. PNF had probably figured out what was happening, but could not square the symptoms with what he thought PF was doing. He assumed - and more or less had to assume – that PF was doing all the right things to control the aeroplane and when he did take control, a quirk of the stall warning system prompted PF to effectively snatch back control and keep pulling back. When the Captain returned, he too couldn’t even begin to understand what PF had been, and still was, doing.

The software protocols of the Airbus – an otherwise beautiful machine – have again been called into question and I don’t suppose for a moment the boys and girls in Boeing’s design/ build teams are going to say; “Tell you what, how ‘bout a sidestick upgrade for the 773, the 748 and the 787?” any time soon. For interested SLF, this accident is a very, very worrying revelation.
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