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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 14th Jun 2017, 14:23
  #1481 (permalink)  
 
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Fear of Fear. Bonin's initial actions were not delayed by time spent in assessment. It is easy to say, "...the aircraft Nose was down, and it was in right roll..." So. Immediate inputs? Perhaps. Was stress level high?

It is common for our "survival" response to react quickly, to not allow a situation to "get away from us...." Additionally, abnormals are almost always experienced in the sim, where the expectation is for quick solutions....

It is not uncommon for one to act quickly, precipitously, to avoid fear "taking over".

The A330 does not Stall like a glider... Not at all like a glider.

A question other than "How could the pilot input so much nose up?":

How did he keep it right side up, directionally stable the entire time? The Stall Is benign, so much so....

Not only does it stall gently, it is so easy to fly whilst Stalled....

Is Recovery from Stall in the A330 more frightening than descending right side up at 7000 fpm? Does it present such an intimidating prospect in recovery that falling is the preferred option? Is recovery impossible, regardless the altitude available?
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Old 30th Jun 2017, 18:04
  #1482 (permalink)  
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https://www.wired.com/story/boeing-a...ane-autopilot/

“Airbus tries to avoid human error; Boeing tries to take advantage of human capability.”

“AF447 is the quintessential example of what can go wrong with automation,” says Balog. .

The flight crew didn’t understand the automation system, they simply trusted it.

The captain could have saved the flight with a few simple actions, but made exactly the wrong decisions.
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Old 12th Jul 2017, 22:15
  #1483 (permalink)  
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https://blogs.crikey.com.au/planetal...-france-af447/
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Old 12th Jul 2017, 22:24
  #1484 (permalink)  
 
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An incident in which pilots will inexplicably pull on their stick at cruise altitude, climb and be saved from a stall and dive to the ground* only by the airplane's protections is actually very very common.

Multiples occurences per year. My best estimate would be around 15-20 worldwide.


*When a crew comes to a point where their actions on the flight controls cause a transition from normal flight to stalling without them noticing this transition, they generally are unable to recognize and save the situation on their own.
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Old 13th Jul 2017, 22:34
  #1485 (permalink)  
 
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Well

There are precise values in attitude, both in rate and deflection, that trigger a definition of "Jet Upset".

It is arguable 447 was beyond those values almost immediately post Auto Pilot drop. Seconds after loss of AP came the first Stall Warn from the aircraft. One assumes an aircraft alerting an aerodynamic Stall is beyond Upset, and closing in on Loss of Control (Stall, By Definition).

Perspective.
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Old 15th Jul 2017, 02:58
  #1486 (permalink)  
 
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Originally Posted by FLEXJET View Post
I am a bizjet guy, EASA/FAA. While in cruise, I usually see a GS range of 380/620KT.

In the case of AF447, while stalling for 3 minutes, would you agree that their GS was much below that range?
Would you agree that a quick look at the OFP will give the expected and accurate GS to be compared with?

The crew checked engine parameters but I never read in the report that GS was mentioned or discussed.
I am just wondering if checking / discussing / comparing GS could have reversed this tragic fate, i.e. could have made someone finally push the stick (again, Airbus design, sorry to insist...).
Considering their heading wandered more than 180 degrees off planned, I say that no, a quick look at their flight plan would not give a GS useful for comparison.

I maintain that the FPD is for immediate, basic aircraft control type information. Am I gonna stay right side up, hit the ground, or go off course?
Anything beyond that is clutter. GS is generally for navigation problems. Should the unique occasion arise that would make it useful for more immediate aircraft control due to an unusual circumstance, I think that if a pilot has the mental space to make meaningful use of that information, he has the mental space to look one screen over.
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Old 15th Jul 2017, 15:51
  #1487 (permalink)  
 
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did you mean "PFD"? Relying on GS, or including it in scan, is arguably ridiculous, given the "g", other instrument indications, and loss of altitude. The VSI is sufficient? It too, is "airspeed"? They knew without looking at GS that they were in deep ess?
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Old 16th Jul 2017, 02:13
  #1488 (permalink)  
 
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Originally Posted by _Phoenix View Post
His glider experience didn't helped with the stall of a swept wing, at cruise altitude.
The stall warning was not triggered continuously during the stalled condition, but it was triggered when not suppose to. I believe this aspect was never discussed.
It certainly was discussed by me and by others.

Granted they had screwed up massively and persistently. Granted they had entered a part of the (non) flight envelope no-one could reasonably have expected a pair of ATPLs to ever explore. I grant you all that and more. But still...

- Push forward and you get a stall warning
- Pull back and the stall warning stops

No flight control and instrument system should ever present that behaviour to a pilot.
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Old 16th Jul 2017, 16:52
  #1489 (permalink)  
 
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Ranger One.

I'm betting it was discussed. Just at the first STALL WARN from the aircraft, was Bonin's stick forward? His very first Pitch input (post AP loss) was Nose Up, but seconds later, as the aircraft climbed, could the SW have activated based on erroneous indicated (calculated AoA) airspeed? In spite of correct elevator input?

I have never associated the first SW with the much later reversed activations of the alert. If his first Nose Down was met with the STALL STALL, could it have set the stage for repeated and chronic Nose Up, which eventually put them in the Ocean?

One can "learn very quickly" under extreme stress.

At Captain's entry to the cockpit, the Horn ceased. Had false adaptive behavior caused Bonin to pull to silence the alarm? Very counter intuitive, but the Aft Stick is itself very counter intuitive?

Has anyone ever synched Bonin's stick with the timing of the SW?

Last edited by Concours77; 16th Jul 2017 at 17:03.
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Old 16th Jul 2017, 18:25
  #1490 (permalink)  
 
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Originally Posted by _Concours77
Has anyone ever synched Bonin's stick with the timing of the SW?
Have you actually bothered to read the accident reports?
Page 29, 30 & 31.
https://www.bea.aero/docspa/2009/f-c...90601e3.en.pdf

Last edited by Goldenrivett; 16th Jul 2017 at 18:44.
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Old 16th Jul 2017, 19:04
  #1491 (permalink)  
 
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Ranger One:

I think you need to go back and carefully review the BEA Final Report:

https://www.bea.aero/docspa/2009/f-c...p090601.en.pdf

There, I believe you will see that the first stall warning occurred almost immediately after the autopilot disconnected, the cause being ice crystals in the pitots and had nothing to do with any PF stick input. The auto thrust went to thrust lock nearly at the same time. While the two pilots were trying to diagnose what was happening a gust caused the aircraft to start to roll, and the PF spent a good deal of attention and time attempting to stop that roll. Then you can read what took place after that.

Keep in mind you are posting on Thread #12. The previous 11 threads are easily accessible and contain a great deal of information and discussion, some coming from experienced A-330 pilots, engineers and fly-by-wire experts in other aircraft. There is also significant discussions and information as to what reliable data and protections were available as the transitions to alternate law and alternate 2 law occurred.

A recent question was if the aircraft was recoverable once it was in the stall. The answer is, nobody really knows for sure as it has never been examined in the way it happened using an A-330 aircraft from that altitude. However, there are two reports of attempted recovery in flight sims that resulted in the idea recovery was possible if the stall was recognized early and the stick was pushed all the way forward and held for a fair period of time. As I recall, the recovery occurred at about 22 to 25K feet and some other caveats were noted to keep from stalling again...
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Old 16th Jul 2017, 20:15
  #1492 (permalink)  
 
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Goldenrivett.

At 2:10:09. Bonin pushes stick forward.
At 2:10:10 STALLSTALL
At 2:10:11 (at 52 kts.) Bonin pulls back,
At 2:10:12 STA.....

Bonin does not push forward again except in "mayonnaise".

Thanks for reviewing this with me.

Turbine D.

"...two pilots were trying to diagnose what was happening a gust caused the aircraft to start to roll, and the PF spent a good deal of attention and time attempting to stop that roll. Then you can read what took place after that...."

If memory serves the attitude of the a/c just after the loss of Auto Pilot was 15 degrees right roll, minus two degrees ND. That is almost five degrees too low, and 15 degrees more than level wings. So it did not "start to roll" whilst the two pilots were "diagnosing" their situation?

Your diagnosis of the cause of STALLSTALL is not germane, and is meaningless to the pilots at the time. The warning happened just after Bonin input Forward stick. The STALLSTALL may not have been related to the input, but was concurrent with it. Similarly, the 52 knots was a nonsense, but absolutely may have been related to the warning....we aren't discussing your conclusions, only what might the pilots have done relative to what was happening That they could experience

Last edited by Concours77; 16th Jul 2017 at 20:33. Reason: grammar, spelling
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Old 16th Jul 2017, 22:32
  #1493 (permalink)  
 
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Concour77,
Your posting:
If memory serves the attitude of the a/c just after the loss of Auto Pilot was 15 degrees right roll, minus two degrees ND. That is almost five degrees too low, and 15 degrees more than level wings. So it did not "start to roll" whilst the two pilots were "diagnosing" their situation?
From the Final Report:
The first disturbances in speeds 1 and 2 occurred at about 2 h 10 min 04, causing the autopilot to disconnect, which was signalled by a visual and an aural (cavalry charge) warning. The crew did not necessarily perceive these transient losses of speed information and the associated losses of altitude.

In addition, the crew’s mental resources were already taken up by turbulence avoidance maneuvers and the plan to climb during the minutes that preceded the autopilot disconnection.

When the autopilot disconnected, the roll angle increased in two seconds from 0 to +8.4 degrees without any inputs on the sidesticks. The PF was immediately absorbed by dealing with roll, whose oscillations can be explained by:
ˆ A large initial input on the sidestick under the effect of surprise;
ˆ The continuation of the oscillations, in the time it took to adapt his piloting at
high altitude, while subject to an unusual flight law in roll (direct law).

Following the autopilot disconnection, the PF very quickly applied nose-up sidestick inputs. The PF’s inputs may be classifed as abrupt and excessive. The excessive amplitude of these inputs made them unsuitable and incompatible with the recommended aeroplane handling practices for high altitude ight. This nose-up input may initially have been a response to the perception of the aeroplane’s movements (in particular the reduction in pitch angle of 2 associated with the variation in load factor) just before the AP disconnection in turbulence. This response may have been associated with a desire to regain cruise level: the PF may have detected on his PFD the loss of altitude of about 300 ft and loss of vertical speed of the order of 600 ft/min in descent. The excessive nature of the PF’s inputs can be explained by the startle effect and the emotional shock at the autopilot disconnection, amplified by the lack of practical training for crews in fight at high altitude, together with unusual fight control laws.

Although the PF’s initial excessive nose-up reaction may thus be fairly easily understood, the same is not true for the persistence of this input, which generated a significant vertical flight path deviation.

There remain a number of possible explanations:
ˆ The crew’s attention being focused on roll, speed or on the ECAM;
ˆ The initiation, more or less consciously due to the effects of surprise and stress,
of the action plan (climb) desired by the PF prior to the autopilot disconnection;
ˆ The attraction of “clear sky”, since the aeroplane was flying at the edge of the
cloud layer;
ˆ A saturation of the mental resources needed to make sense of the situation, to
the detriment of aeroplane handling;
ˆ The presence of turbulence that may have altered perception of aeroplane
movements in response to his inputs.
In answer to your final comment, the things they could have done, was to correct the roll, adjust the pitch angle and pause, doing basically nothing, until diagnosing the problem rather than reacting immediately to something not understood.
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Old 17th Jul 2017, 00:22
  #1494 (permalink)  
 
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Please read again my short post of attitude, STALL-STALL, IAS, and Stick movements.

They are listed with their appropriate time.

Please go to page 29 of the Final Report, and check my accuracy....

Please review the first report from the BEA from the recorders, to check my attitude recollections. It was there that Nose Down was first reported. It exonerates Bonin's first move: NOSE UP.....

This is the timeline from the Final Report.

"At 2:10:09. Bonin pushes stick forward.
At 2:10:10 STALLSTALL
At 2:10:11 (at 52 kts.) Bonin pulls back,
At 2:10:12 STA....."

I was suggesting that his ND input was interrupted by the STALLWARN. As Ranger One has suggested, and I agree, an Aircraft should NEVER signal a STALL that is not happening...

Bonin's first conclusion post AP loss may have been informed by the WARNING. If so he may have assumed crossed controls. If so, it was reinforced later on, many many times...If so, it would explain why there was no discussion of the STALLSTALL later, amongst crew.
Or he may have disregarded the Warning, and not trusted it again.

Why is the Report silent about his ND input being interrupted by STALL STALL just seconds after manual flight begins?

One thing the Captain said would fit with a general agreement about the STALL WARN being accurate? but later suspected? "...TRY CLIMB!..." Why would the Captain suggest a move against the (assumed) inability to recover? He was suggesting it as a desperate, counter indicated action. How do we know this? Bonin: "...We have tried everything..." The Captain had assumed the Aircraft was not responding to commands?
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Old 17th Jul 2017, 07:59
  #1495 (permalink)  
 
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Concours77
Why is the Report silent about his ND input being interrupted by STALL STALL just seconds after manual flight begins?
I suggest you read the accident reports before posting.

Page 89. https://www.bea.aero/docspa/2009/f-c...p090601.en.pdf
"The activations of the warning picked up by the CVR were identified as occurring
at between 2 h 10 min 10.4 and 11.3 and between 2 h 10 min 13 and 13.4. The
short duration of activation did not make it possible to detect it from the “Stall
warning” parameter, but the FWC 1’s “Master warning” parameters were triggered
on one point at this time. However, this warning should have continued until about
2 h 10 min 15.5, and then have been triggered again between 2 h 10 min 17 and 19.
The disabling of this warning was probably due to the fact that, between 13.4 and
15.5 and then between 17 and 19, and possibly at other times, the three Mach values
were abnormally low (three Pitot probes iced up). The warning triggering threshold
then suddenly increased to values of about 10, much greater than the recorded
angles of attack, which led to the warning stopping.

After 2 h 11
Analysis of the parameters showed that the stall warning stopped concomitant with
the invalidity of the three angles of attack, and was triggered again when at least one of
them became valid again. In view of the extreme values of angle of attack experienced
by the aircraft, the change to the threshold as a function of Mach was secondary.
The stall warning triggered again ten times after 2 h 11 min 45; a correlation was noted
between this triggering and a pitch-up input by the PF on two occasions, between
2 h 12 min 52 and 2 h 12 min 57 then between 2 h 13 min 52 and 2 h 14 min 02."

NB. Airbus has since redesigned the stall warning logic.
"STALL WARNING enhancement: Stall warning will work when:
Undetected erroneous computation of pitot
Pitot out of the airflow
Pitot obstructed by ice or any foreign material at any speed (function now possible below 60 kts)"
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Old 17th Jul 2017, 14:53
  #1496 (permalink)  
 
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I see nothing in your post about the source of my question. Perhaps de rigeur in an accident report, but this is about discussion.

PF input a deliberate and singular ND (no Mayonnaise) one half second before hearing the STALLSTALL, then a deliberate NU at which time the Warning ceased.

Interesting? No?

"What was that?"

My continued thesis is that the aircraft came to grief because the recovery was foreclosed by immediate and exaggerated handling, which was in most cases the reverse of what was indicated to the pilots.

That an aircraft can come to grief from sub standard instrumentation and seemingly random handling is cause for a concern perhaps more in depth than a data sheet?

Not a report, a discussion....
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Old 17th Jul 2017, 16:37
  #1497 (permalink)  
 
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Sorry I'll repeat previous posts. From report: "we have no indications" still wonder what Bonin meant by that! Had he even got a PFD? ( I lost 5 of 6 screens in an a320 which granted only lasted 15 secs or so. The sign off in the tech log to my entry was "impossible"
Still think most pilots would have scr**** up on this one. & yes I wasA330 rated.
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Old 17th Jul 2017, 19:12
  #1498 (permalink)  
 
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"...We have no indications..."

The last eyewitness to the instrument panel, the only record we have.

There was no instrument panel. All was dark.

It doesn't take any extensive imagination, the comment would explain why there was no (poor) CRM. There wasn't anything to discuss...
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Old 17th Jul 2017, 19:37
  #1499 (permalink)  
 
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Original Post by Concours77: My continued thesis is that the aircraft came to grief because the recovery was foreclosed by immediate and exaggerated handling, which was in most cases the reverse of what was indicated to the pilots.

That an aircraft can come to grief from sub standard instrumentation and seemingly random handling is cause for a concern perhaps more in depth than a data sheet?
On Airbus A-330 & A-340 aircraft, there were somewhere between a dozen or eighteen incidents at high cruise altitude where pitot tubes became clogged with ice crystals and A/Ps and A/Ts disconnected leaving those crews in the same position as the crew in AF447. In each instance, with the exception of AF447, the flight crews were able to address the situation correctly and flew on landing safely. Their key to success was recognition of the problem and instituting a plan to counter the abnormal problem they were handed. Each successful crew functioned well as a team.

In the AF447 situation, the crew never figured out what the problem was, didn't function well as a team, never developed a plan to counter their experience after A/P & A/T disconnect and never referred to available instructions had they had a clue of the problem at hand. Airbus designs aircraft that can be safely flown by pilots that understand the FBW systems and are astute in recognition of changes in flight control systems from normal to alternate (not normal). So given what transpired after the AF447 episode started, the non-recognition of the problem and how the crew responded, there was no recovery possible in the remaining time allotted. The aircraft responded to sensor information and pilot input as it was intended to do. As I have said before, there is a wealth of discussion and information contained in previous threads beyond the more recent postings in this Thread. It would be worth your while to explore the many items that have been discussed in detail. Here is one example coming from an Airbus pilot:
The difference between the crash and a crew who knows what's going on and how to deal with the situation more elegantly ...
AF 447 Thread No. 10
Refer to Post # 576
You can get to Thread No. 10 by going to the first post in this Thread No. 12
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Old 17th Jul 2017, 19:53
  #1500 (permalink)  
 
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"...The difference between the crash and a crew who knows what's going on and how to deal with the situation more elegantly..." ....pretty arrogant.

Were each of these aircraft equipped with "..we have no indications..." panels?

No record exists of what the instrument panels were displaying in 447....

Alot taken for granted, at crew's expense herein...
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