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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 17th Jul 2017, 20:41
  #1501 (permalink)  
 
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Concours77,
No record exists of what the instrument panels were displaying in 447....
So tell me, how do you know "we have no indications..." panels? You are misinterpreting a verbal statement about speed to fit your theory of instrument panels...

Why do you think it took so much attention and time to get the roll stopped? What do you think made the situation, once in the stall at 38K feet, not recoverable besides not recognizing they weren't in a stall?

Which memory item did the PF potentially revert to when he recognized they were out of the flight path?
pretty arrogant
Not so much so when you try to explain what needs to be done to stay safe...
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Old 18th Jul 2017, 00:11
  #1502 (permalink)  
 
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"Which memory item did the PF potentially revert to when he recognized they were out of the flight path"

Approach to stall at low altitude. What flight path? No FDs. No "indications"

You know exactly what flight path, you have the passive recordings of their four minutes of wandering. You have this knowledge. You presume to judge them because they did not?
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Old 18th Jul 2017, 03:33
  #1503 (permalink)  
 
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I do not recall discussions about stall warning triggered at 2 h 10 min 51. The first long/consecutive (not sporadic) stall warning. At that point in time, the “situation” was fully recoverable. Why didn’t happened? I think it’s interesting to see why Bonin wasn’t able recognize, or more precisely, he didn’t believed in the stall situation. It was discussed only that he was an Airbus pilot. He was accustomed to sporadic/false stall warnings, kind of immune to that specific sound. Airbus cannot be stalled in normal law, then most of the times the sporadic stall sound was inhibited automatically. No alert, no worries. But he was an experienced glider pilot. For sure he experienced the real stall condition in a glider, maybe only in a glider. The glider behaviour is completely different. You can feel the approaching of stall, clear buffet, no aerodynamic noise and 0 g. Then the nose drops abruptly towards the ground, the speed and aerodynamic noise increase very rapidly and you have to pull the stick sharply before reaching the overspeed threshold. None of these known “stall symptoms” accompanied the stall warning of AF447. No buffet, vertical acceleration ~1g and for subsequent 20 seconds the variometer indicated climb, that’s quite impossible, at least according to aerodynamic stall definition of any manual. Finally after 20 seconds (while thrust was at TOGA) variometer changed sign, it went abruptly into negative accompanied by a huge aerodynamic noise generated by the airflow around the A330 body. “I don’t have control
of the airplane at all” “I have the impression (we have) a crazy speed”
About this aspect, I’m saying that was not detailed before, the stall warning triggered when not suppose to. Also I believe this “false” stall warning is related to the following statement in the report
the threshold of the stall warning varies with the Mach, in such a way that it is triggered - in alternate or direct law – before the appearance of buffet.
About the other swisscheese hole (of the stall warning ceased for speed <60kts) , it was perfectly aligned with the Captain entering the cockpit. Then, the last chance of a fresh acknowledgment of the situation was obliterated.
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Old 18th Jul 2017, 12:56
  #1504 (permalink)  
 
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Is buffet associated with Stall possible in Normal Law? Would it matter? FA: "...should we sit?..." (Belt in) "Yes I think so...'

Captain entering cockpit was climbing an aisle at 15 degrees nose up? 1g? He said nothing except "Er... what are you doing?"

With aerodynamic noise at high level, and an arduous "climb" up the aisle, he misses the cues?
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Old 18th Jul 2017, 17:16
  #1505 (permalink)  
 
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"Which memory item did the PF potentially revert to when he recognized they were out of the flight path"
The two copilots had only been trained for the emergency maneuver at lower levels, in the course of which the pitch attitude to adopt is 10° or 15°.
Is buffet associated with Stall possible in Normal Law?
No, not on the Airbus aircraft.
I do not recall discussions about stall warning triggered at 2 h 10 min 51.
That is correct. From the CVR:
2h10min51,4 SV : Stall
2h10min52,0 SV : Stall
Neither of the pilots made any reference to the stall warning, neither of the pilots formally identified the stall situation.

When the Captain entered the cockpit, he stood behind but between the two pilots while he quickly scanned the situation. He got only general verbal information from the PF & PNF, so he had few clues to go by, including the position of the side stick of the PF. The one thing he did have a good view of was the trim wheels position. Normally they bounce around a little but the THS had moved to the full up position responding to the trim system and stabilizing the aircraft in the pitch axis. There was quite a bit of detailed discussion in previous Threads about the aerodynamics of the situation AF447 was in and the effectiveness of the elevators at that point. Throughout the flight, the movements of the elevator and the THS were consistent with the pilot’s inputs.

The biggest clue given to the Captain came too late: 2 h 13 min 40
PF - "But I’ve been at maxi nose-up for a while."
Captain - "No no no don’t climb."
PNF - "So go down."
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Old 18th Jul 2017, 22:20
  #1506 (permalink)  
 
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The icing event lasted 60 seconds. Ninety seconds after the Master Warning/Cavalrty Charge, the Captain came back to the flight deck. At that point, the aircraft was at its assigned altitude, the Angle of attack was forty degrees, and they were descending, rapidly.

"...What the Hell are you doing?..." So, Captain noticed the loss of control. erm, boy howdy.

There was no angle of attack indicator, and Captain evidently neglected to ascertain Bonin"s stick aft, to the stop.

A minute later, they were discussing whether they were Descending, or Ascending.

Three issues of design prevented them from recovery.

No angle of attack indicator.

No way to see stick inputs from PF.

This aircraft Stalls essentially without cues, it is benign in the STALL.

Return one of these deficiencies to the cockpit, and they do not crash.
Return two of them, and they do not STALL.

Return all three, and we would have nothing to write about.

And Air France would be out forty thousand dollars for the AoA instrument.

C'est la Vie.....



.
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Old 18th Jul 2017, 22:59
  #1507 (permalink)  
 
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Again, the stick inputs from the PF are very easy to see if you just look at them.
You would see that immediately if you sat in an airbus pilot seat.

I agree with you on the necessity for a smart aoa indicator. As well as a stick shaker if the airbus does happen to stall.
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Old 19th Jul 2017, 00:21
  #1508 (permalink)  
 
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Concours77,
This aircraft Stalls essentially without cues, it is benign in the STALL.

Return one of these deficiencies to the cockpit, and they do not crash.
Return two of them, and they do not STALL.

Return all three, and we would have nothing to write about.

And Air France would be out forty thousand dollars for the AoA instrument.

C'est la Vie.....
Problem solved, no need for further discussions...
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Old 19th Jul 2017, 00:53
  #1509 (permalink)  
 
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Neither of the pilots made any reference to the stall warning, neither of the pilots formally identified the stall situation.
They hadn’t time for a narrative in the CVR, the actions and the communications between them are enough proof.
The proof is all there: the THR levers were advanced to TOGA, two seconds after “Stall, Stall” (at 2h 10min 51). 7 seconds later PF confirmed TOGA power achieved, PNF advise for gentle maneuvers on lateral, then later both are perplex: “But we’ve got all the engines, what’s happening?”
Important remark: During this particular sequence, there was not any physical stall situation for the aircraft, only the false stall warning. This I’m trying to explain in my last two posts, here.
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Old 19th Jul 2017, 14:15
  #1510 (permalink)  
 
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Bonin initiates his first singular (unlinked in mayonnaise) Nose Down before the STALLWARN. 2:10:09.

Can you confirm that TOGA is an appropriate selection? With a full NOSE UP THS, and full thrust on engines also producing Pitch Up, how is aero flight regained? (2:10:51)

So, absent any STALL airframe response, why would they initiate a STALL "recovery"?
At the very least, keeping aft stick throughout is not consistent with STALL recovery, only a trained response to STALLWARN approach to land? That includes Added Thrust?

How is full thrust appropriate for recovery? Wouldn't NOSE DOWN and reduced Thrust be the drill? They were worried about crazy speed? They had gobs of altitude to work with?
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Old 19th Jul 2017, 14:24
  #1511 (permalink)  
 
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Originally Posted by KayPam View Post
Again, the stick inputs from the PF are very easy to see if you just look at them.
You would see that immediately if you sat in an airbus pilot seat.

I agree with you on the necessity for a smart aoa indicator. As well as a stick shaker if the airbus does happen to stall.
The Captain was between the two pilots, and behind. No visibility of Starboard stick for him. We have no evidence of PNF peeping the PF stick....

AoA. How difficult and expensive can it be to display a computed AoA parasite from the computer?

"...ERM, FORTY DEGREES AoA....!?!!...Push the Nose Down, EH?"

Airbus was granted a waiver for no pusher/shaker at certification... They had convinced the authority that the a/c would not Stall in Normal Law, and in ALTERNATE, the pilots would be ready for STALL, no passive safety device would be necessary?

Additional design deficiencies.

1. Automatic Pitch Trim Nose UP into the STALL.

2. Absence of alerting device to signify Auto TRIM into STALL.

2a. Cumbersome manipulation of TRIM by hand, to return TRIM to neutral. Once released, the TRIM moves to regain full Nose UP. Extremely inconvenient in an emergency. Enforced distraction.

3. Surprise handling change in ROLL, splitting the stick into two modes.

4. Back up Speed System not installed, optional.

5. Low Energy Alerting Program not installed, not available.

6. Slow rolling replacements of deficient speed sensors, Pitots.

Having read and reread the endless focus on PF's stubborn NOSE UP, I am including the aircraft deficiencies, in the interest of justice.

Last edited by Concours77; 19th Jul 2017 at 14:39.
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Old 19th Jul 2017, 15:27
  #1512 (permalink)  
 
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Concours77,
Can you confirm that TOGA is an appropriate selection?
It is not the correct selection at high altitudes, it is the correct selection if a stall warning is received right after TO. As I mentioned previously, I believe the pilots recalled the memory list, but not all of it, especially the part they needed to recall:

Actually, the safe conduct of the flight wasn't impacted and all the pilots needed to do was level the wings, set the thrust to 80% of N1, and set the pitch to 2.5 - 3.0 degrees. Then begin to troubleshoot using the messages received and written documentation.
Here is a listing of other flights that experienced what AF447 experienced, twelve received stall warnings:

All survived. For AF447, they are cruising along normally, engines are providing appropriate thrust, pitch is within limits, slight turbulence and then the AP and AT disconnects and the message word is speed. What could cause it to be a problem?

I think you are concentrating on items that happened as a result of not following instructions. Why didn't the pilots follow instructions they were trained to react to and follow? Why didn't the pilots remember the pitch/thrust item for the altitude they were initially at? I recall Air France had put out a written document as a result of ice clogged pitots, making the problem known to pilots and what to do if encountered. I am not sure the AF447 crew received the document or not before the incident.
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Old 19th Jul 2017, 15:48
  #1513 (permalink)  
 
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Originally Posted by _Phoenix View Post
They hadn’t time for a narrative in the CVR, the actions and the communications between them are enough proof.
The proof is all there: the THR levers were advanced to TOGA, two seconds after “Stall, Stall” (at 2h 10min 51). 7 seconds later PF confirmed TOGA power achieved, PNF advise for gentle maneuvers on lateral, then later both are perplex: “But we’ve got all the engines, what’s happening?”
Important remark: During this particular sequence, there was not any physical stall situation for the aircraft, only the false stall warning. This I’m trying to explain in my last two posts, here.
Hi Turbine,

This post prompted my response. Actions taken without communication are not appropriate, if not trained or listed in the QRH.

I'd have to check, but "What's happening....?" the aircraft is climbing wildly? So, why the hyperfocus on power? If descending, with positive Pitch, there is no Stall, at least not a traditional one.

I believe the pilots were never aware of STALL, including the Captain, and this due to the Airbus' unique flight characteristics in full STALL. The aircraft, even in descent at 10,000 fpm was controllable, pedestrian attitude (high Pitch excluded). None of the pilots insisted on ND. The only command related to PITCH was Robert: "...climb,climb,climb....!" then, Captain: "...No,No,No, don't climb..."

Even after it was discovered Bonin had held aft stick, there was no acknowledgment of STALL.

May we eliminate reference to Bonin's glider time? It was unhelpful at best, since the A330 in this instance gave not one single aerodynamic clue of Stall. The "buffet" claimed in the report was unnoticed or unremarkable, since they had been in turbulence, sufficient to direct CC to "buckle up'.....
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Old 19th Jul 2017, 16:07
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One item I haven't seen in all these discussions is the flight directors. The report says that they disappeared along with the autopilot disconnection, and then reappeared and disappeared several times again. Crucially, the first time it reappeared it commanded 6000 fpm up, and the remaining times 1400 fpm up. Given the general FD overdependance talked about often on these forums, combined with the tunnel vision and stimulus-ignoring that happens during task saturation, this supplies a very big and easy puzzle to the "inexplicable" issue of why the PF kept pulling up.

I read this a while ago, and wondered why the FD would command this without being told to by the pilots. Just now I went back into the report, and that question is answered in section 1.6.9.2, which says that if they were not turned off manually, and reappear automatically when the computer data becomes valid again, they come back in HDG and VS modes. I'm sure this is common knowledge among Airbus pilots, which I am not. I can only assume that the VS value commanded is that which is what the airplane is doing the moment when they reappear.

So, if the plane was momentarily combing at 6000 fpm in a totally unsustainable zoom climb, it'll keep guiding the pilot to that climb regardless of the plane's ability to do that. And if the wide-eyed and overloaded pilot reduced his ability to observe (and interpret) all the pertinent display values, and reverted to trained habit (following the FD) then there's the recipe for the disaster that happened.

On learning this, I immediately thought that this is a terrible design wrt. human factors. The FDs, if off, should not come on again without their mode being explicitly set by the crew, according to what parameter the crew wants the FD to guide them to. Here, the "lock in the present VS" premise obviously failed the crew, who I'm sure were not aware of (much less in desire of) what they were following. Airbus pilots, has this been changed? What is the current behavior of the system in this case?
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Old 19th Jul 2017, 17:46
  #1515 (permalink)  
 
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Again, the stick inputs from the PF are very easy to see if you just look at them.
You would see that immediately if you sat in an airbus pilot seat.

...............As well as a stick shaker if the airbus does happen to stall.
Not necessarily. At night and if the cockpit is dark, it is not so easy to see - especially if the tray table is out. Also, if you are expecting a pilot not to hold full back-stick, (why would he?), you would not look for it. This is why, in my opinion, the real cause of the problem was so baffling to the other F/O and the Captain. Neither of them expected that Bonin would be holding full back-stick, so they did not even look for it.

Linked controls and/or some sort of side-stick position indicator on the PFD would have alerted the crew to Bonins' actions.

Another thing that troubles me is that this scenario is not being demonstrated in the SIM. I had it 'done' to me in the SIM by a very good TRE, and it opened my eyes. It is all very well doing a few minutes of high level manual handling and a few more minutes of low level stall training, but not the same thing as actually experiencing what these poor chaps had.
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Old 19th Jul 2017, 19:56
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Vessbot

All aircraft, not just Airbus, will have Flight Directors and Autopilots that, by default, initiate in HEADING HOLD and (present) VERTICAL SPEED. Those modes are the only ones that can start from scratch (meaning present conditions).
All other modes need certain parameters to be established ALREADY to continue the guidance along that condition.

Concours77
You are misinterpreting non-sensical exclamations by the AF447 crew as technical realities.
That crew talked about "the screens being crazy" - that is a very unprofessional observation for pilots. Those "screens" are displays that portray a multitude of information from many different, independent sources.
True, the speed indication was weird for a short while, the altitude indication dipped a bit at the very beginning, but the ATTITUDE INDICATION, that is THE MOST IMPORTANT CONTROL INSTRUMENT in INSTRUMENT FLYING, was indicating with perfect precision what was happening.
A transport aircraft at cruise altitude is flown with the nose about 3 degrees above the horizon, for a climb a maximum of 1 degree higher, for a descent about 1 degree lower, for an idle descent about on the horizon, but NEVER, NEVER NEVER at 15 degrees above the horizon.
The communication between the co-pilots was all about CLIMBING or GOING DOWN, but NEVER ABOUT THE PITCH ATTITUDE that was required.
Note, that by zooming up untill all speed was bled off, the climb automatically was turned into a descent (GO DOWN), but the way in which they went down was not a wise one.
The captain had the bad luck to enter the flight deck just as the ALTITUDE was about 35.000 ft again, just the same value as when he had left the flight deck, so he had completely missed the zoom climb and the susequent drop down. The co-pilots could tell him nothing useful, so it took a while for him to figure out wat the rapidly decreasing altitude indication really meant.

Please note that failures of display screens are also monitored situations, monitored by ECAM that is, and the flight data showed no abnormality at all in that respect.
Note that I have used capital letters to write things like ATTITUDE, because people do often, in postings, confuse the word with an L and a T with the version with double T, and that is quite a crucial difference for a pilot flying on instruments.
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Old 19th Jul 2017, 21:03
  #1517 (permalink)  
 
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Vessbot,
One item I haven't seen in all these discussions is the flight directors. The report says that they disappeared along with the autopilot disconnection, and then reappeared and disappeared several times again.
The appropriate question is, why didn't they turn them both off? The reason why they should be off is because they are being fed erroneous data that the pilots should not respond to.

Air France A330/A340 Abnormal Procedures

“Unreliable IAS” in force at the time of the accident

PF AP..........................OFF
CP FD1 and 2................OFF
PF A/THR......................OFF
PF Set Thrust................CLB
PF Set Pitch..................5º
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Old 19th Jul 2017, 21:24
  #1518 (permalink)  
 
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Originally Posted by EMIT View Post
Vessbot

All aircraft, not just Airbus, will have Flight Directors and Autopilots that, by default, initiate in HEADING HOLD and (present) VERTICAL SPEED. Those modes are the only ones that can start from scratch (meaning present conditions).
All other modes need certain parameters to be established ALREADY to continue the guidance along that condition.
What I'm saying is that if turned off automatically for whatever reason (such as invalid air data in this case), it should stay off until manually set. Do you see the problem with coming on commanding VS 6.0 at the performance ceiling of the plane?
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Old 19th Jul 2017, 21:54
  #1519 (permalink)  
 
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Originally Posted by Vessbot
it should stay off until manually set
That was the BEA recommendation in 2012.

See Page 210. https://www.bea.aero/docspa/2009/f-c...p090601.en.pdf
4.3.7 Ergonomics
The crew did not de-activate the flight directors and did not call out any changes in
FMA mode. It is not sure that they noticed the appearances and disappearances of the
flight director crossbars. It is likely that the crew did not know of the mode changes
when the flight director became active again, reading and assimilating the displays on the FMA in dynamic and stressful conditions not being instinctive or natural.
It seems that requiring an action from the crew to re-engage this automatic system
would, on the one hand, lead to a consistency with the autopilot and the autothrust,
and on the other hand stimulate a check on the modes and the consistency of the
commands presented at the time of the re-engagement.
Consequently, the BEA recommends that:
€ EASA require a review of the re-display and reconnection logic of
the flight directors after their disappearance, in particular to review
the conditions in which an action by the crew would be necessary to
re-engage them; [Recommendation FRAN-2012-047]
Further, even if it is not sure that the crew followed the orders from the flight director
while the stall warning was active, the orders from the crossbars were in contradiction
with the inputs to make in this situation and thus may have troubled the crew.
Consequently, the BEA recommends that:
€ EASA require a review of the functional or display logic of the flight
director so that it disappears or presents appropriate orders when the
stall warning is triggered. [Recommendation FRAN-2012-048]

Last edited by Goldenrivett; 20th Jul 2017 at 09:50. Reason: Typo
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Old 19th Jul 2017, 22:10
  #1520 (permalink)  
 
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Problem

Originally Posted by Vessbot View Post
What I'm saying is that if turned off automatically for whatever reason (such as invalid air data in this case), it should stay off until manually set. Do you see the problem with coming on commanding VS 6.0 at the performance ceiling of the plane?
The problem that I see is in regarding the Flight Director as a COMMAND (as in a command that has to be followed blindly).
I command the aircraft to go where I want it to go, and if I have properly managed my autoflight system, that system will suggest attitudes to me that will be pretty close to, and possibly a refinement of, what I am already doing.

Any other approach to flight guidance is rubbish.
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