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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 20th Jun 2014, 02:38
  #141 (permalink)  
 
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The warning "Stall" seems to invite some pilots to put the stick on their stomach ... So replace this "Stall" warning by another like "Noze down"
Maybe more pilots will better understand ...... if any
Simple problem .. simple solution
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Old 20th Jun 2014, 04:01
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PIO

Some basic definitions and references about control theory, stability, oscillation, gain and PID,etc.

Oscillation - Wikipedia, the free encyclopedia

Control theory - Wikipedia, the free encyclopedia

PID controller - Wikipedia, the free encyclopedia
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Old 20th Jun 2014, 14:39
  #143 (permalink)  
 
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Originally Posted by DozyWannabe
What I have more trouble understanding is the motivation behind pulling the nose up past half-stick deflection around 02:10:09 (i.e. at AP disconnect), when the PF has just been explaining to the PNF why they are unable to safely climb to a higher flight level.
You seem so sure that the PF would have had no reason to climb intentionally. I'm not so sure.

At 01:52:23, when he pointed out to the Captain: "You see the REC MAX it’s changed to three seventy five", the Captain's only reaction was to start making preparations for his rest break. Later, when he said to the PNF in the briefing at 02:00:33 "So what we have is some REC MAX a little too low to get to three seven", I can imagine him thinking "...and this doesn't seem to bother our stubborn old man at all."

From the report (2.1.1.2):
...the PF wanted to change flight level and fly above the cloud cover, while recognising that it was not possible for the moment to climb two levels. He made several allusions or suggestions on the flight levels and the temperature from 1 h 35 min 20 onwards. He even considered requesting a non-standard level 360. His various interventions in the minutes that preceded the autopilot disconnection showed a real preoccupation, beyond the simple awareness of an operational risk. Some anxiety was noticeable in his insistence.
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Old 20th Jun 2014, 14:54
  #144 (permalink)  
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Hi Dozy;
Re,
And while it may not be productive to merely wonder, as you say, the idea that 80% of a random sampling of pilots instinctively pulled up when startled by a Stall Warning
Sorry, I may be gradually losing it but where do I say, "...the idea that 80% of a random sampling...", etc? I don't believe I'd say such a thing because I don't believe the statement to be true in the first place! ;-)
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Old 20th Jun 2014, 15:11
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Sorry - ambiguous wording. "as you say" refers to your assertion that "It isn't productive to wonder".

You may not believe the 80% figure, but the stat and its source are very real and discussed earlier in the thread (Tarom A300 over Paris Orly).
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Old 20th Jun 2014, 15:55
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I agree with you
PJ2 and don't believe to the existence of such an experiment.
Originally Posted by roulishollandais#62
@DozyWanabee
1. It has been said again and again that training was a major factor in AF447. I don't remember that inexperience has been pointed as such a point. Why don't Airlines maintain the level from skilled pilots like these Vétérans ?

2. You know that math was my first learning. In that immense matter, I used "some" time in stats ! Real stats. Not what we are used to read in magazines, because stats are not very pleasant to understand nor to read... And no aviation investigation wants to give you a pleasant reading ! or a complete demonstration.

Please watch, about Airliners stall, on one hand we are reading that test pilots don't stall airlines, on the other hand we should accept that airlines pilots (likeTarom) should have done an experimentation with 80% pilots pulling the stick at any startle factor... Where are these experimentations ? they don't exist !
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Old 20th Jun 2014, 16:08
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Well from an informal sampling of USN carrier pilots, 99.999% will reduce angle of attack when receiving a stall warning and the ones that don't are generally facing an imminent collision with something solid and are trying to at least get the cockpit above the solid object before impact.
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Old 20th Jun 2014, 16:21
  #148 (permalink)  
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Ah, understand thanks. I am indeed losing it or over-interpreting...!

I read the posts earlier in the thread earlier, (and again, now) - I was looking at the "80%" figure more broadly and not in the rare specific cases cited. It's not a matter of belief, the stats are indeed there, (I was thinking training scenarios, etc).

While the sample rate is to small (Tarom, Colgan, Thomson, Turkish...are there others?) to take this statistically-seriously, I could understand the notion that it, (pulling up and in some cases not adding power), at first warning of a stall, should never occur in such a high-risk event does take us beyond statistics into a mandate to do something.

In this then, I don't think it is possible to over-train.

I believe in Gladwell's notions, (Outliers). I play an instrument which is both a cognitive and muscle-memory activity and the only way to play accurately and fast is to practise, practise, practise.

Both cognitive response time and muscle memory improve dramatically and, (if one is performing in public, which I certainly do not!), reduces performance anxiety, and startle tremendously regardless of whether it is an airplane, typing on a keyboard, playing the piano or reciting/speaking text from memory. The mind-and-muscles "go to the right place", to loosely describe it.

I know you and many here know this already - it isn't new, though Gladwell has put a refreshing interpretation on it. Here, not only was there not a correct response, (or a response to incorrectly-perceived cues) but no concept of what was about to rapidly happen to the aircraft's energy in a sustained climb. There seemed no concept or awareness of an airplane's physical state or environment. It should not be possible to get into the cockpit of a transport aircraft absent these basics.

In the light of AF447 especially, but also in view of the "80%" perspective, I wonder what our regulators consider "stall practice" these days?

I know that in Canada, once one has been initially certified for the airplane, there is no requirement whatsoever to demonstrate approach-to-the-stall or stall recovery in fly-by-wire aircraft. I have no idea what the justification is for this because it seems to imbue FBW technology with some form of magic when it's just another way of moving the flight controls. I suppose they're thinking of the Airbus protections but we all know now that a more sophisticated approach to such training needs to be done. What do the JARS have to say?
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Old 20th Jun 2014, 16:29
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Originally Posted by roulishollandais
and don't believe to the existence of such an experiment.
Originally Posted by DozyWannabe
@galaxy flier:

That figure came from this report on YR-LCA - an A300 on approach to Orly airport in 1994:

YR-LCA

(Use your browser's "Find" to look for the relevant section with '80%')
Also, PDF version in English: http://www.bea.aero/docspa/1994/yr-a...r-a940924a.pdf (Page 30, Para. 5)

and French : http://www.bea.aero/docspa/1994/yr-a...yr-a940924.pdf (Page 29, Para. 7)

The document exists, and if you believe there was no experiment to glean those statistics, then you're effectively accusing the BEA of making the figure up - a serious allegation!

[EDIT : NB. My above comment is directed only at roulis. Cheers for the clarification, PJ2!]

Last edited by DozyWannabe; 20th Jun 2014 at 16:42.
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Old 20th Jun 2014, 16:43
  #150 (permalink)  
 
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@Noske

Thank you for setting the context prior to AP disconnect of PF anxiety and a desire to climb above the weather. So apparently the PF was already biased to climb before AP disconnect. In stress such bias can be amplified.
That said why would he not verbalize his action to increase flight level to his colleague when he initiated the zoom climb. My own view is that it was a conscious action and a failure to verbalize/communicate to PNF rather than a subconscious.

Last edited by xcitation; 20th Jun 2014 at 17:32.
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Old 20th Jun 2014, 17:48
  #151 (permalink)  
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xcitation;

Re,
My own view is that it was a conscious action and a failure to verbalize/communicate to PNF rather than a subconscious.
Yes, I think so. This is consistent with all cockpit behaviour noted by the BEA - absence of SOPs and CRM at critical junctures where it counted and likely would have made a difference in the outcome.

Anyway, there is little to re-argue/re-hash that isn't in The Threads, so returning to lurking while awaiting something new and interesting.
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Old 20th Jun 2014, 18:38
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Originally Posted by xcitation
That said why would he not verbalize his action to increase flight level to his colleague when he initiated the zoom climb. My own view is that it was a conscious action and a failure to verbalize/communicate to PNF rather than a subconscious.
I'm not denying it's a possibility - but on the other hand, if the control input was an entirely conscious move to get to a higher FL, why did he not level out at a sensible point and instead continue to drag the aircraft up towards "coffin corner"?
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Old 20th Jun 2014, 18:52
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Paradoxically .... unconscious can do things consciously !
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Old 20th Jun 2014, 18:55
  #154 (permalink)  
 
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Bias

@DW
why did he not level out at a sensible point and instead continue to drag the aircraft up towards "coffin corner"?
Excellent point. I think this is where bias comes in. When all you have in your hand is a hammer everything looks like a nail. To him he had pre-occupied his mind with getting higher to fix the problem. Then after AP disconnect he got confirmation bias coupled with an endorphin rush. I think this is the gremlin that we referred to as startled. As a pilot it is critical to understand that the brains perception can become biased during stress. This is effect amplified by modern highly automated cockpits.

Last edited by xcitation; 20th Jun 2014 at 20:17.
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Old 20th Jun 2014, 21:28
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While I certainly wouldn't disregard the possibility noske brought up, I had a quick look back at the report because I was sure I was forgetting something - which turned out to be this:

Originally Posted by BEA Final Report (EN) p.169
The relief crew did in fact inherit some decisions to make. From 2 h 01, the PF mentioned the subject of the ITCZ, turbulence and the choice of flight level in his briefing to the co-pilot who joined him as relief for the Captain. From 2 h 04 to 2 h 08, after the Captain’s departure, the two co-pilots discussed the ITCZ again. The PF repeated his idea of climbing to level 360, without doing so. Acknowledging this non-solution, he warned the cabin personnel of imminent turbulence. After changing the gain on the weather radar from “calibrated” to “max”, the PNF then suggested as of 2 h 08 min 03 a route alteration, which the PF willingly executed.
Therefore there exists the possibility that the "problem" as you describe it - namely the weather/turbulence situation and how to avoid it, may have been considered as solved in the mind of the PF with the PNF's lateral course change.
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Old 21st Jun 2014, 04:53
  #156 (permalink)  
 
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Therefore there exists the possibility that the "problem" as you describe it - namely the weather/turbulence situation and how to avoid it, may have been considered as solved in the mind of the PF with the PNF's lateral course change.
Solved? I don't think I'd give that interpretation a very high probability.

Crews usually consult on the best route through weather. The process has enough variability that you would never consider a weather problem solved until it is behind you. Best you can hope for is to achieve the least hazardous route.
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Old 21st Jun 2014, 06:46
  #157 (permalink)  
 
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Semantics seems to strike again...

Solved? I don't think I'd give that interpretation a very high probability.
For Gods'sake Sir, I think it's possible that the "overpedantic " gentlemen had a slip of mind with "solved" and would better used "dealed by..' or "treated by..."
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Old 21st Jun 2014, 16:26
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NOT semantics. This relates to the mind state of the person flying. While picking your way through weather, if the person flying consideres that an instantaneous choosing of the apparent best heading has completely taken care of his weather problem and he can relax and think about other things, then he probably doesn't even belong at the controls.
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Old 21st Jun 2014, 19:35
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We can therefore consider in addition to other possible causes for the persistence of pulling (and the uncommon pitch of 12-15° followed), the initial intention to avoid the storm by climbing, pursued simply omitting to move the throttles and to let the other guy know what he intended...
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Old 21st Jun 2014, 19:43
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@M'bird:

Where do I say that "instantaneous choosing of the apparent best heading has completely taken care of his weather problem and he can relax and think about other things", or words to that effect?

Maybe it's because I've been reading Dr. Al Diehl's book on human factors recently, but I'm talking more from a psychological perspective than a practical/piloting one. Of course a minor course correction isn't going to completely solve the weather problem - and I doubt the PF thought so, but generally I find that people tend to get their stress levels elevated more when they perceive that there's a problem and nothing is being done about it, and while it doesn't exactly go away, it does tend to subside somewhat when they recognise that attention is at least being paid to solving the problem.

Incidentally, I completely recognise what you're saying about USN carrier pilots, but I think sending every trainee airline pilot to go shoot carrier landings before giving them their ATPL is probably overkill...
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