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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 22nd Feb 2017, 14:36
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Can we say: "aircraft at altitude fly very fast. Why? They have to, or they won't fly"

Is that a different way of stating your opening above?

May I offer a way to look at high altitude performance and the Airbus logic of "Stall"?

The THS went full Nose Up, ostensibly to provide a (wing) loading the elevators could not?
The aircraft is neutral in longitudinal stability, it resists dropping its Nose, even at Stall?
The Stall Warnng is inhibited at air speeds (indicated) of sixty knots, or less?
A symptom of this aircraft's approach to Stall is "uncommanded Roll"?
Another symptom at Stall is "unresponsive controls"?

This looks like an excellent performance envelope for an aircraft at altitudes below four hundred feet AGL. An aircraft about to land.....

Do we know why the Thrust was maintained for the entire descent? Was it commanded, or Autothrottle?

Given your description of high altitude handling qualities, does the aircraft's design comport with high altitude Stall?

Did the aircraft know where it was? Did its designers consider that some excellent design features for a landing aircraft might not be optimal for a Stall at 37000 feet?

I would like to say that except for descent rate and the lack of extended landing gear, the aircraft was in excellent attitude to land?

Thanks to Machinbird, and also Phoenix...

Last edited by Concours77; 22nd Feb 2017 at 14:49.
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Old 22nd Feb 2017, 17:34
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At 30kts it doesn't compute.
A bit like reversing at 3km/h, the ABS doesn't cut in.
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Old 22nd Feb 2017, 17:43
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Hello Winnerhofer....

"A bit like reversing at 3km/h, the ABS doesn't cut in."

Why would it? The phonic sensor is live, the wheel is rotating?

Is ABS available in reverse? Why would it be?
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Old 22nd Feb 2017, 18:52
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The crew had loss of AP, a short Stall Warning, and an attitude “approaching” upset.
Also degraded to AL2B.
They entered a climb as the Auto Trim motored smoothly to full NU, where it stayed until impact.
Crew had no AoA indicator, neither did they have the optional Artificial Horizon, or BUSS.
They noted the climb, though their CRM lacked a concurrent discussion of recovery.
They tried to regain the “bird” in the display, and the F/O had desperately tried to move the FCM into “Direct Law”.
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Old 22nd Feb 2017, 19:16
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They entered a climb "as rapid as 7000 fpm" as the Auto Trim motored smoothly to full NU, where it stayed until impact. (full Nose Up. = -14 degrees)
Crew had no AoA indicator, neither did they have the optional Artificial Horizon, or BUSS.
They noted the climb, though their CRM lacked a concurrent discussion of recovery. "There was no reduction in climb rate, post discussion..."
They tried to regain the “bird” in the display, ("to "see" flight Path, or to calculate AoA is not known") and the F/O had desperately tried to move the FCM into “Direct Law”. " Possibly by defeating the FCS by opening the Breaker?"

Alterations included....

Last edited by Concours77; 22nd Feb 2017 at 19:19. Reason: Alterations by author....
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Old 23rd Feb 2017, 05:57
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Can we say: "aircraft at altitude fly very fast. Why? They have to, or they won't fly"
Is that a different way of stating your opening above?
No, that was not the intent of the post.

If Bonin had used a strategy of control such as I described, the aircraft would have arrived in Paris. Since that is not what happened, it means he used an inappropriate control strategy. The question is why?
Did he have any experience hand flying at altitude? I am thinking he did not since he was flying extensively in RVSM airspace on autopilot. If he had any exposure to hand flying, it was almost certainly in Normal Law in a simulator.

Did he have experience flying in Alternate law with Roll Direct? As I understand, the answer is no. That training was reserved for Captains.

Did he have confidence in his abilities to hand fly? Judging from his performance, he did not. CRM went immediately out the window, and his PM was clearly distressed by his performance. This is the type of situation that could be expected to create strong fear in both individuals right at the start of the non-normal event. First Bonin, then Robert.
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Old 23rd Feb 2017, 11:24
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@Concours77

http://www.pprune.org/tech-log/55547...axed-lose.html
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Old 23rd Feb 2017, 14:37
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Stability Wars: Why Did Relaxed Lose?
Winnerhofer
Perhaps you provided the link so that Concours could better inform himself.
With regard to AF447, the trim tank was full, and that meant that the CG was at or near the aft limit which provided lessened trim drag.
The down side of that CG location was that once stalled, it was easier for the aircraft to reach extremely high angles of attack.
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Old 23rd Feb 2017, 14:58
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Quote from Machinbird:
"Did he have any experience hand flying at altitude? I am thinking he did not since he was flying extensively in RVSM airspace on autopilot. If he had any exposure to hand flying, it was almost certainly in Normal Law in a simulator.
Did he have experience flying in Alternate law with Roll Direct? As I understand, the answer is no. That training was reserved for Captains."


Surely it will come as no surprise that I'm in agreement with that line of argument, and that probably goes for many others lurking in the background - particularly those of us that were used to hand-flying subsonic jets at the same speed and altitude as AF447 in the cruise. But we seem to be going over familiar ground...
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Old 23rd Feb 2017, 15:40
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With regard to AF447, the trim tank was full, and that meant that the CG was at or near the aft limit which provided lessened trim drag.
The down side of that CG location was that once stalled, it was easier for the aircraft to reach extremely high angles of attack.
Maybe the trim tank was full but i believe the CG was not near the aft posn. Due freight in fwd hold (i am told)
In the airline I flew the 332 with the trim in the cruise was around 38 to 39 which is getting nearly full aft.
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Old 23rd Feb 2017, 16:41
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The BEA Final Report states that at the time of the accident the CG was 28.7%
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Old 23rd Feb 2017, 17:07
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Icepack and Owain, thank you both for the correction.
From the BEA final report (English version),
The balance corresponding to the aeroplane’s takeoff weight and shown on the final
load sheet (after LMC) was 23.3% of the MAC (mean aerodynamic chord), which was
within the limits.


The recorded data indicates that at the time of the event, the aeroplane’s weight was
205.5 tonnes and the balance was 28.7%, which was within the limits.
From a A332 CG chart, the max inflight aft CG for 205 kg x 1000 (is that the same as 205 tonnes?) is about 39%, so obviously much more aft CG was available to AF447.
The trim tank was apparently able to move the CG aft ~5%. Probably Owain can provide a more complete estimate.
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Old 23rd Feb 2017, 17:20
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Originally Posted by Chris Scott
Surely it will come as no surprise that I'm in agreement with that line of argument, and that probably goes for many others lurking in the background - particularly those of us that were used to hand-flying subsonic jets at the same speed and altitude as AF447 in the cruise. But we seem to be going over familiar ground...
Yes, familiar ground until we get to this part of the statement:
Originally Posted by Machinbird
Did he have confidence in his abilities to hand fly? Judging from his performance, he did not. CRM went immediately out the window, and his PM was clearly distressed by his performance. This is the type of situation that could be expected to create strong fear in both individuals right at the start of the non-normal event. First Bonin, then Robert.
I think that if we look within ourselves, we will agree with this statement also, and that is an opening into a discussion of fear in the cockpit.
Again, by fear, I do not mean screaming fits, mearly the physiological response to fear.
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Old 23rd Feb 2017, 18:33
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Machinbird

The TO CG was 23.3%, so that would tie up with your approx. 5% from the trim tank.
Yes, 205kg x 1000 is 205 tonnes. Trim tank holds 4800 kg which would give a bit more than 5% shift at 205T
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Old 24th Feb 2017, 19:00
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FIGHT/FLIGHT RESPONSE

First, thank you Owain Glyndwr for the confirmation of the A332 trim tank aft cg contribution.

I believe it is necessary to discuss the physiological fear response to understand the human side of what happened to AF447. The most universally recognized name for this response is the Fight or Flight response.

Since we are not issued an FCOM for "Human Being, MK1 Mod0, we have to pick up our understanding of the special operating modes of this highly complex device through personal experience and personal curiosity. Just as our aircraft can surprise us as it switches control laws unexpectedly, your own body can surprise you with unexpected and unrequested automatic mode shifts. The Fight or Flight Response is one of those mode shifts than catch you out if you are not prepared for it.
An explanation of Fight or Flight response can be found here:
The Fight or Flight Response - NeilMD.com
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Old 24th Feb 2017, 23:31
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NeiMD

Machinbird,

I haven't studied it, but I have given it a speed read. Thanks Evelyn Wood.

I might not be on the same page as you are relative to fear on the flight deck of AF447.

The thrust of the book after a quick look is that "fight or flight" is deep within our DNA, a relic of the survival default when facing the "saber tooth tiger". Its prescription is to "blunt" the reflex, since there are no longer "saber tooth tigers" challenging our survival, and there are ways to relax and reason around the "sub saber tooth" realm of modern challenges.....

So what do flight crew have to deal with that is actually a "saber tooth moment"?

Asseline knew he was going to crash into the trees, he didn't lose it, he crashed, and survived.

Haynes lost his vertical Stabiliser along with his number two fan. He not only didn't panic, he enlisted help to make a certain crash survivable. They found a dead heading Captain, and had him lie down and work the "steering" (differential thrust, manual.)

Perpignan? Captain knew they were gone, but he kept pulling the stick, pissed off he couldn't get more "g".

Sullenberger? Amazing. So where do we look for what you diagnose as panic?

Colgan. Captain heard a Stall Warn, because the bug was not reset after De-Ice was switched off, a faulty and premature alert.

He lost it, though he had a good twenty knots to lose before the actual Stall. He pulled, because his training was to "lose minimum altitude" at Approach to Stall. When that ate up his margin, the stick pusher volunteered to help, but he kept pulling, likely forgetting the pusher was the good knight, ready to save them.

That qualifies as panic that killed.

I don't see panic on AF 447, nor do I see evidence of flee or fight, a sub set of panic. I see anxiety, lack of confidence, confusion.... All things that can be overcome if the level of training and personal development is sufficient.

I would like to recommend a book by a friend of mine, Sylvia LaFair.
"Pattern Aware"

We can learn to trust our calm and qualified self. The pilot is a computer, well in advance of any Valley branded mother board.

Making best use of the equipment is what flying requires. Pilots have skills that are impossible to reproduce in any computer, abstract thought, intuitive problem solving, and very nearly the kind of calm detachment that comes with the actual computers only advantage, emotionless RAM.
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Old 25th Feb 2017, 22:35
  #1357 (permalink)  
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Flug AF 447 - Kollaps der Team-Struktur im Cockpit könnte Airbus-Absturz ausgelöst haben
Flight AF 447
Collapse of the team structure in the cockpit could have triggered Airbus crash
In June 2009 an Airbus from Air France crashed across the Atlantic and killed 228 people. The reason for this was frozen sensors, but now crises investigate the disaster again: they see fundamental problems with the handling of people with highly automated board technology.
June 2009, flight AF447 on the way from Rio de Janeiro to Paris. The Air France aircraft has been in the air for over three and a half hours and is already far out across the Atlantic. The captain is resting. In the cockpit of the Airbus the two copilots. Outside stockfinstere night. Suddenly the autopilot turns off.
"I have control," says the copilot. But that will change drastically in the next seven minutes. Important exterior sensors of the Airbus are frozen. That's why the instruments spin! They indicate that the aircraft loses a lot, but this is not true. The copilot at the wheel believes the error message and rips the machine up. But now the airbus nose is too steep. It threatens the dreaded flow tear, a complete loss of the lift.
Giving gas and nose down! That would be appropriate now. But the alarm and the instrument display are contradictory. Is the machine now rising or falling? The pilots keep the climb, there is a flow break. Even the captain, back in the cockpit, can no longer avert disaster.
Lack of emotional distance to the onboard computer
"The last few seconds are characterized by the fact that people have only tried to take over the control by means of the joysticks, but this was not coordinated at all, which can be traced using the flight recorder evaluations," says Gordon Müller-Seitz. He is a professor of strategy and cooperation at the TU Kaiserslautern. One focus of his research is on crises arising when dealing with technologies at the interface between man and machine. Therefore the interest in flight AF447. Müller-Seitz shares with an expert colleague, French study scientist Olivier Berthod from the Freie Universität Berlin: "When the machine no longer reacts as usual, the emotional stress for the copilot is so great that everyone is just as bored to pay attention to what The onboard computer. At this point, organized action collapses."
"The breakdown of the team structure, the communication structure - that would be what was interesting in the case," says Gordon Müller-Seitz. He and Olivier Berthod are now presenting a new analysis of the misfortune and come to the conclusion that this is a fundamental problem in the way people deal with highly automated technology. The pilots lacked a critical distance to their onboard computer. In a confusing situation they were fixed on the instruments instead of pausing and thinking together what was going wrong at the time.
"It is all the more important," says Gordon Mueller-Seitz, "that the people - we would call it - have a certain vigilant, attentive neutrality with regard to technology Master of the situation, and that was not the case, because the interplay between the man and the machine broke. "
It was indeed dark and the pilots practically on the way. But would not they have had to feel what their machine was doing?
"This was also the reason for the fact that it was an Airbus aircraft, because the Airbus cockpit and the instruments did not convey a sense of how much the flight was actually flying. When one had flown a Boeing aircraft in comparison, You would have felt the movements from the outside, because they are electronically transmitted and simulated while you were simply in a closed cockpit in the Airbus. You did not know how to move, whether up or down Down, because it was night."
As a consequence of the crash, pilots are now training in their simulators the failure of the autopilot in cruising altitude. And Olivier Berthod emphasizes that the number of accidents with Airbus machines has not increased, but decreased. Nevertheless, the ability to work in the cockpit should be better trained, as he recommends:
"It's always easy to sit down at the desk, but we think that in critical situations, pilots should understand themselves as a team rather than a team, looking for a solution together, which should be a standard procedure and trained."
The new study has quickly moved around in aviation circles. And the researchers were already given first invitations to lectures before pilots.
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Old 26th Feb 2017, 00:40
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Quote from Winnerhofer (post #1345) :
"They entered a climb as the Auto Trim motored smoothly to full NU, where it stayed until impact."

Not quite...

The function of any auto-trim system is to remove the necessity for the PF or AP to continue to command the deflection of a primary flight control. In this case the auto-trim is concerned with pitch control, and adjusts the incidence (angle) of the THS (trim-able horizontal stabiliser) to enable the elevators to return to neutral in a few seconds after they have been deflected to comply with a command from the pilot or AP for a pitch-change (actually, in the case of C*, a change in normal G).

So in AF447 the THS "motored", as designed, in reaction to persistent pitch-up inputs from the PF's sidestick; inputs which were inappropriate once the aircraft had returned to the correct indicated altitude and which led in due course to an aerodynamic stall. That was allowed in turn to progress to a deep stall which the crew did not identify as such.

Quote from Machinbird:
"CRM went immediately out the window, and his PM was clearly distressed by his performance. This is the type of situation that could be expected to create strong fear in both individuals right at the start of the non-normal event.
I think that if we look within ourselves, we will agree with this statement also, and that is an opening into a discussion of fear in the cockpit."

Yes, I concur with that.
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Old 26th Feb 2017, 02:18
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Summarizing Neil on Fight or Flight

I have cherry picked the Neil piece for physiological information that might be applied to AF447. Neil's emphasis was on preventing and controlling over-activation of of the fight or flight response. In AF447, we had an accute invocation of that response. Normal emergency training is intended to give a direction to our actions, thus avoiding stress inducing situations.
Excessive stress creates an automatic protective reaction within the body that initiates nerve cell firing and chemical releases (adrenaline, noradrenaline & cortisol) to prepare us for running or fighting.
When our fight or flight system is activated, we tend to perceive everything in our environment as a possible threat to our survival. By its very nature, the fight or flight system bypasses our rational mind—where our more well thought out beliefs exist—and moves us into "attack" mode…….Our thinking is distorted. We see everything through the filter of possible danger. We narrow our focus to those things that can harm us. Fear becomes the lens through which we see the world.

Has the fight or flight response become counterproductive?

In most cases today, once our fight or flight response is activated, we cannot flee. We cannot fight. We cannot physically run from our perceived threats. When we are faced with modern day, saber tooth tigers, we have to sit in our office and "control ourselves.

How do we elicit the relaxation response?

Because the relaxation response is hard-wired, we do not need to believe it will work, any more than we need to believe our leg will jump when the doctor taps our patellar tendon with a little red hammer. The relaxation response is a physiologic response, and as such, there are many ways to elicit it, just as there are many ways to increase our pulse rate (another physiologic response).
1. 1. Focus on a word or phrase that has a positive meaning to you
...........................
3. Deep diaphragmatic breathing exercises, with a focus on the breath, can trigger the relaxation response.
(The last two items are methods that might be practical in a cockpit while managing an emergency.)
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Old 26th Feb 2017, 15:32
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From Chris Scott:

"The function of any auto-trim system is to remove the necessity for the PF or AP to continue to command the deflection of a primary flight control. In this case the auto-trim is concerned with pitch control, and adjusts the incidence (angle) of the THS (trim-able horizontal stabiliser) to enable the elevators to return to neutral in a few seconds after they have been deflected to comply with a command from the pilot or AP for a pitch-change (actually, in the case of C*, a change in normal G)."

A question? I asked Owain Glyndwr at one point why the graph in the report of the THS movement looks "smooth"? Yet the graph of the stick trace looks anything but? The trace is full of bumps, up and down....

If the THS moves as a result of pilot command, wouldn't the system itself be representative of the pilots "choppy" stick movement?

Owain Glyndwr responded that he did not have the integration constant, so could not comment why the graphs were "seemingly" disparate?

Wouldn't this work have been done by the report? It would seem obvious to show the system worked as designed? If it is in the report, please disregard my question....
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