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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 28th Feb 2017, 13:50
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To be frank, I don't rate Learmount much.
He's long long passed his sell-by date.
I think this was ghost-written.
This is the full version no editing.
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Old 28th Feb 2017, 15:01
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Phoenix

Here,

"ERR, what are you doing?!" and stall warning miraculously went silent."

When the Commandant du Bord entered the cockpit, finally, only one of the three had any experience flying this airliner in Alternate Law 2b. Bonin.

In that sense, he was "senior" in "type". Robert had criticisms, but made no attempt to take control from Bonin.

I have a theory about this phase of the flight.

gums,

"- The jet has really great aero to get into a stall without obvious shaking, buffet, wing rock and so forth."

I think that is intended as a compliment.... I think it is actually an indictment.

As most experienced pilot in 2b, Bonin may have gained sufficient mastery to understand the jet was comfortable in Stall. The "sweet spot" as it were. Attempts to lower the nose caused the Stall Warn to activate and may have actually re introduced "buffet", a signal that lowering the nose was the "wrong" thing to do.

Whatever buffet there was was likely encountered when the aircraft "began a recovery", iow, there was buffet on either side of the Stall, entry, and escape.

Did Bonin purposely defeat the Stall Warn (by pulling back the stick) to demonstrate to the Captain they were not as bad off as might be surmised? Thinking they were on the "right side" of the Stall?

I think none of these three experienced aviators had ever actually flown in Roll Direct before this flight. Or experienced the "great aero" that may have led them to their demise...

As to the THS: There seems to be no discussion in the report of the logic that produces Automatic trim into and through the Stall, which also served to make recovery difficult, if not impossible.

Airbus has no duty to discuss this issue. Bringing it up is not necessary, and would only serve to put into question the design. In the record, on the CVR, Robert is quoted: "loss of Protections," or similar. That is sufficient to satisfy the duty Airbus has to inform pilots of a particular design feature. There is no liability to provide a Protection if it is known that none are available in this flight Law? Inhibiting AutoTrim would IMO qualify as a protection...
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Old 28th Feb 2017, 16:00
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Originally Posted by Concours77
When the Commandant du Bord entered the cockpit,
With respect, sir, their names are:
David Robert, Pierre-Cedric Bonin, Marc Dubois (the captain)
As most experienced pilot in 2b, Bonin may have gained sufficient mastery to understand the jet was comfortable in Stall. The "sweet spot" as it were.
Bonin, also a glider pilot, was experienced enough to know that He Does Not Want To Be Stalled and that Being Stalled Means That You Aren't Flying, You Are Falling. My provisional conclusion was that Bonin was never aware -- in the cognitive sense -- that the aircraft was stalled. (until perhaps some seconds before impact). I have seen nothing to make me revise that conclusion. We discussed at length, in previous threads, the issue of the trained maneuvers, which is stall prevention focused with the cue of a stall warning. Stall recovery was not a training maneuver for the A320 type. Please note that, when you are stalled, your stall prevention procedures most often are not going to solve your problem but your stall recovery procedure usually will. (I spent a few years teaching spins and stalls, half of a lifetime ago).
Attempts to lower the nose caused the Stall Warn to activate and may have actually re introduced "buffet", a signal that lowering the nose was the "wrong" thing to do. ... Whatever buffet there was was likely encountered when the aircraft "began a recovery", iow, there was buffet on either side of the Stall, entry, and escape. ... Did Bonin purposely defeat the Stall Warn (by pulling back the stick) to demonstrate to the Captain they were not as bad off as might be surmised? Thinking they were on the "right side" of the Stall?
What brand are you smoking? I'd like a taste.
Based on the feedback/cueing Robert was providing to Bonin as the latter tried to get his hand flying up to scratch, Bonin's instrument scan was somewhere between slow and non existent, and it is difficult to ascertain whether or not he was trying to follow the flight director or to try and keep the AH level ... go back and read the reminders/feedback Robert is providing. Bonin is Behind The Aircraft from a few seconds after he announces that he's go the controls, and as I read the timeline, something like six seconds after he starts to manipulate the side stick the first stall warning voice message is logged in the CVR.
2 h 10 min 06,4 Bonin | I have the controls
2 h 10 min 11,0 SV | stall
Have you read the full report and all of the appendices?
Have you read the tech log forum discussions (here at PPRuNE) that began with the release of the first CVR, and the subsequent FDR, information that came out in one of BEA's interim reports. While there's a bit of noise, there is some superb exposition on how that system works, and where some of the "gotcha" bits are.
I think none of these three experienced aviators had ever actually flown in Roll Direct before this flight.
That was discussed at length, and speculated over, during the series of threads on this crash. One more opinion is now offered. The discussions on training took up a lot of space in the PPRuNe threads.
As to the THS: There seems to be no discussion in the report of the logic that produces Automatic trim into and through the Stall, which also served to make recovery difficult, if not impossible.
If you keep pulling the stick back, and the flight control surfaces keep trying to do what your control inputs call for, the THS isn't going to change its orientation since it keeps trying to trim to account for the latest commands to the elevators.


The extended discussion in the PPRuNe threads arrived at a number of very sharp folks concluding that you'd need to make a nose down command -- and hold it for a while -- so that the THS would move (albeit slowly) in the other direction away from a trimmed position that was "pro stall."
In the record, on the CVR, Robert is quoted: "loss of Protections," or similar. That is sufficient to satisfy the duty Airbus has to inform pilots of a particular design feature. There is no liability to provide a Protection if it is known that none are available in this flight Law? Inhibiting AutoTrim would IMO qualify as a protection...
In what flight regime? Inhibiting auto trim might also create handling problems.

Last edited by Lonewolf_50; 28th Feb 2017 at 16:18.
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Old 28th Feb 2017, 16:44
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"From the pilot’s point of view, the fundamental change in the A320 was the addition of flight envelope protection (FEP), which all aviators hope – and most would like to believe – they will never need."

Lol.
If you knew how often they come into play

"Pilot mental appreciation of how the FBW laws work in practice seems to be just a matter of familiarity. Manual flying in the A320 series feels perfectly intuitive, so it should not matter whether the pilot thinks of a pitch-up displacement of the sidestick as a demand for a proportionate elevator deflection, or as a demand for a proportionate increase in vertical g (which is how the FBW system delivers it), because the effect is identical: the nose-up attitude increases as demanded by the pilot. Likewise, it should not matter whether a pilot displacing the sidestick to the left is demanding a proportionate aileron deflection or a proportionate rate of roll, as the effect is identical."

Let's totally disagree on that.
If you fly, especially at a high altitude, without consideration for whether or not you're in normal law, you're in for a sur-prise !
My opinion is it should be made very obvious whether the A/C is in normal law or not, with HUGE red signals when it is not. The small amber and red crosses are, imho, not enough.

Simple example : windshear recovery.
ATPL theory tell us you should pull up to the stick shaker. Airbus FCOM replaces stick shaker with full back stick, thanks to alpha protection.
Now try to apply this normal procedure when in direct (or even just alternate) law and tell us if stalling during a windshear recovery help or if it didn't.
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Old 28th Feb 2017, 17:24
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Quote from _Phoenix
"Now, at 2h10m41s apparently Bonin was in control, he checked from his memory, UAS items: (THR) "yeah we’re in climb" then corrected the pitch to 5-7 deg, all seemed stabilized, but was only an apparent calm, before the disaster. Pilots had no physical cues whatsoever about the aircraft dramatic loss of speed and energy(3) "

Hi, I don't know your background, so I don't want to seem patronising. It may or may not be surprising for you to imply that lowering the nose to a pitch of between +5 and +7 degrees would be a sufficient correction. In fact, it would remain outside the acceptable envelope of pitch at that altitude.

To illustrate the point, the cruise TAS of an A330 is - let's say - 480 kt. That's 8 nm/minute, or 48640 ft/min. Starting from level flight (pitch around +2.5 deg), a pitch-up of just one degree gives a VS of about +800 ft/min. Pitching up to +6 at cruise altitudes would give an INITIAL VS of about +2800 ft/min. But even at Climb thrust the aeroplane would be simply trading kinetic energy for altitude. The climb rate would be completely unsustainable, so the IAS and Mach would decrease rapidly, and consequently the VS also.

The initial pitch-up remained uncorrected, and was the first bad move that led to this tragedy - as you know. Of course you are referring to a later phase, by which time nearly all the surplus kinetic energy had been squandered. This would have been evident to any jet pilot experienced at hand-flying climbs at high altitude. The clue would have been in the altimeter. IIRC, they had earlier discussed the possibility of climbing (gently) by 2000 ft, and had decided the aircraft was a bit too heavy. Yet - inexplicably - Bonin had mishandled a "zoom" climb of about that amount.

Finally if the aircraft was flying level, a pitch of +6 would give an AoA of +6, and the wing would probably be stalled, depending on the Mach. Some people contributing to this thread are simply unaware of the limitations of jet-transport handling near the top corner of the flight envelope.
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Old 28th Feb 2017, 17:26
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In the record, on the CVR, Robert is quoted: "loss of Protections," or similar. That is sufficient to satisfy the duty Airbus has to inform pilots of a particular design feature. There is no liability to provide a Protection if it is known that none are available in this flight Law? [B]Inhibiting AutoTrim would IMO qualify as a protection...[B]


Lone wolf:
"In what flight regime? Inhibiting auto trim might also create handling problems."

In the Stall...where the THS "created handling problems." Point being, the THS performed as you describe, and as advertised....

Last edited by Concours77; 28th Feb 2017 at 17:37.
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Old 28th Feb 2017, 17:56
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Concours77

Mon Cher Concours77,
Here are the missing pieces of what really happened on the flight deck.
1) Remember that Bonin only had a Frozen Licence.
2) This is why Dubois asked him as he left the flight deck: "T'as le PL, toi?
This is a strange question.
When I hail a taxi, I do not ask the driver if has a licence.
He asked because he knew damn well that Bonin only had a Frozen Licence.
The BEA confirmed this.
The BEA also hashed the DFDR.
An argument ensued following Bonin's answer which is more than just "Oui".
This is where Robert had just entered.
3) All 3 crew failed their recency in 2007.
4) Bonin was a F/A who in 2008 was fast-tracked on to the RH-seat due to
pressures from the Unions.
F/As were exempted from psychometric testing.
In 2008, there were 30 F/As who were fast-tracked at AF.
5) Dubois himself a former F/A only knew too the story as he had become CM1
very late and reluctantly so.
6) The least incompetent was Robert but he was the odd-man-out in Rio as the
other 2 had their respective partners with them.
7) Dubois was standing the whole time because Bonin's wife was in the observer
seat.
8) The whole CRM was just lopsided from the beginning.
Dubois was listening to classical music and commenting an article about tax
havens.
9) Bonin had no idea what ozone and St Elmo's were nor where the Equator was.
https://www.youtube.com/watch?v=jM3CwBYX-ms
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Old 28th Feb 2017, 21:06
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Commandant de Bord is abbreviated CDB.
It is not du but de.
I know French is difficile but that should be your next challenge.
It also gives a way better understanding of AF447.
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Old 1st Mar 2017, 04:06
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Hello Chris,

Yes, that pitch was too much in the coffin corner. But possible he targeted a pitch around UAS procedure: FL100 and up -> 5 deg/CLB (annexe.06)
However, the background of the subject is that "Pilots had no physical cues whatsoever about the aircraft dramatic loss of speed and energy" (apart the altitude reading, that came too late)
You know well that the pitch control movement of the sidestick is normal load factor or g command. The elevator movement is followed by the stabilizer to automatically trim the airplane to a neutral, 1g, stick-free stability. Naturally, if kinetic energy (speed) decreases then the Lift < mg, hence nose goes down (CG within limits). The natural longitudinal flight path was override by FBW trim setting change for constant flight path attitude, as initially commanded.
Airbus considers that no additional alerts about low speed/energy situations is needed at high altitude because large altitude loss due to stall cannot occur on Airbus Fly-By-Wire aircraft.
Well this accident proved that all the sky is not enough.
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Old 1st Mar 2017, 17:49
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For Phoenix,

- "The jet has really great aero to get into a stall without obvious shaking, buffet, wing rock and so forth." gums

"Airbus considers that no additional alerts about low speed/energy situations is needed at high altitude because large altitude loss due to stall cannot occur on Airbus Fly-By-Wire aircraft.
Well this accident proved that all the sky is not enough." Phoenix

Are these quotes related? The jet ended up with full authority (HS) Nose Up, and full thrust on both engines. (One assumes elevators were still available, though not of equal "authority..")

Are those two conditions conducive to maintenance of "horizontal" aspect? Failing one, or both, would the jet have dropped its nose and become easier to recover a controllable flight path?

Does that relate to an approved (regulatory) performance at Stall? I ask because you state "Airbus considers...no additional alerts (cues?)....(are) is needed at high altitude....etc.)?

Because what is suggested is even though the aircraft may be stalled, "no large altitude loss can occur on Airbus FBW"

I guess I'm putting you on the spot. This aspect of the accident, IMO, is not addressed.

I think that if most posters are satisfied that "the aircraft performed as commanded", then the investigation is not complete. So many legitimate conclusions are foreclosed with the lack of design consideration discussion, regulatory expectations, and a solid basis for "safety takeaway" is not possible?
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Old 1st Mar 2017, 19:42
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I think that if most posters are satisfied that "the aircraft performed as commanded", then the investigation is not complete. So many legitimate conclusions are foreclosed with the lack of design consideration discussion, regulatory expectations, and a solid basis for "safety takeaway" is not possible?
Concours,
Yes, the aircraft did perform as designed, however in retrospect there was room for improvement. Aside from the pitot system that was overly sensitive to ice crystal blockage, the stall warning shutting down while the aircraft was still stalled, and the THS continuing to run in the aircraft nose up direction after aircraft reached a stall warning AOA, (in Alt 2b), there were a number of human interface factors that should be addressed. The crew was slow in recognizing the change in flight laws, they stopped hearing the stall warning due to the stress of the moment, and, frankly, the method of presenting altitude on the PFD is not as friendly as an old fashioned steam gauge altimeter, thus leading to slow understanding of just how fast they were falling and what levels they were passing. Some means of better telling, under stress, what the other crew member is doing with the controls is probably appropriate since that was a factor in at least 2 accidents.

The "fix" for the accident seems to have been more in the aircrew training direction rather than in making improvements in the actual aircraft. Those presently flying the aircraft are in a better position to say how comfortable they are with the training adjustments that were made subsequent to the accident.
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Old 2nd Mar 2017, 02:04
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Originally Posted by Concours77
Lone wolf:
"In what flight regime? Inhibiting auto trim might also create handling problems." In the Stall...where the THS "created handling problems." Point being, the THS performed as you describe, and as advertised....
When you are carrying passengers, you aren't supposed to be stalling the aircraft, so that handling parameter is hardly what my "what flight regime" question was aimed at.

I repeat: what we learned during that overly extended discussion is that before that accident, stall prevention was the trained response, not stall recovery. "stall handling" doesn't enter into it.

Nothing further, out.
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Old 3rd Mar 2017, 02:39
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I ask because you state "Airbus considers...no additional alerts (cues?)....(are) is needed at high altitude....etc.)?
Actually, it is an excerpt from an FAA report:
lessonslearned.faa.gov

I see Manchinbird answered graciously to your question. In general, I embrace same views, but a small exception though. Instead of startle effect, I see "rabbit between headlights effect"
I like Airbus. It is a marvel, aerodynamics, endurance and safety, all great. However, FBW laws need to be simplified and "improved". It can be done quietly through a substantial software revision. I think the best is Bombardier's approach, with only two control laws, normal and direct. FBW philosophy is a combination of the older guys, the series C = A+B. Side-stick as Airbus, but C*U flight laws as Boeing, also in addition, Bombardier brings original cutting edge innovations regarding the human-automation interaction and the situational awareness.
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Old 24th Mar 2017, 16:26
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40 Questions Rejected By Investigating Magistrates:
http://www.association-af447.fr/wp-c...experts-DA.pdf
There will be no FURTHER counter-submissions as well re-assements prior to court date:
Crash du Rio-Paris : une enquête difficile - Le Parisien
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Old 1st May 2017, 18:40
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New documentary for 01 June 2017
https://www.scoopnest.com/fr/user/W9/856828133810556929
W9 reconstitue le crash du vol Rio-Paris
Can be watched for free online just by signing on.
6play : Replay W9 et direct des émissions et séries
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Old 1st May 2017, 19:48
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Could you please keep us posted when it becomes available ?
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Old 2nd May 2017, 10:04
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I'm not defending the incompetence of the handling pilot in this incident. But if you're an armchair flight simulator jockey you need to understand a few points about Airbus FBW at high levels.

For a start, despite what Airbus tells you, you're in a different subset of Normal Law. At low speeds (<220 knots) side stick directly commands elevator in the first instance, and then a feedback loop integrates a load factor demand. Without this the lag at low speed would be unbearable.

At higher speeds side stick directly commands load factor, but due to the higher speeds response is far quicker, and the effect more pronounced. Handling the aircraft at high flight levels is actually quite challenging if you don't want to make the passengers sick.

Even small load factors and pitch changes can have a pronounced effect on flight path. Couple this with the startle effect and a hamfisted grip on the controls and you have an aircraft out of control very quickly.

If you've never flown the aircraft manually in (or to) the cruise (and you'd be astonished at the number of people who haven't, blaming RVSM), I urge you to try it.
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Old 2nd May 2017, 11:21
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At low speeds (<220 knots) side stick directly commands elevator in the first instance

-> that's probably because under 220 knots in cruise there is every chance that you're already in alpha protection law
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Old 2nd May 2017, 16:44
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Even small load factors and pitch changes can have a pronounced effect on flight path.
So, leave the stick alone till you figure out what changes in pitch you want. Startle or otherwise they effected huge change in pitch but never checked the result.
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Old 3rd May 2017, 17:18
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Hello Vilas,

"...So, leave the stick alone till you figure out what changes in pitch you want. Startle or otherwise they effected huge change in pitch."

Yes, cerrtainly. In reading the CVR, two things are very notable.

No Pilot commented on PITCH, ever. The one and only comment on Pitch was by Captasin DuBois, two seconds before Impact... The PM only spoke "...You go UP, so go DOWN..." PITCH unaddressed. Bonin only: "...but I have been pulling back..."

(DuBois) "...PITCH, TEN DEGREES..." the last words spoken, but should have been first....?

The second even more remarkable absence is this: None of the pilots mentioned the word STALL. Ever. There were two mentions of STALL, by the aircraft itself, seconds after the loss of Autopilot.

As the Captain returned to the cockpit, the aircraft had stalled, and the Pitch was around fifteen degrees NU. That makes it a steep climb up the aisle, no? Yet he says nothing about orientation or attitude?
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