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AF 447 Thread No. 12

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AF 447 Thread No. 12

Old 28th Jul 2017, 22:05
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What would it take, once the "mush" was established, for the crew to think aft stick was crucial?

1. Any Nose Down would create: instantaneous acceleration and a large increase in vertical speed, down.
1a: shedding gobs of drag and introducing instability, esp. Roll.

2. Less noise (much less), but a worsening of roll reversals.... "Watch your lateral!!"

3. Reinvigoration of the STALLWARN.

What would Attitude look like, on the panel, if it was accurately reporting the decrease in Pitch?

If it was erroneous and showing too low to begin with, the only response possible would be aft stick, increasing Pitch, improving stability, with an increase in aerodynamic noise level.

More so than Stall discussion (there was none), the only remark was about Pitch.

Curious why Captain would report Pitch? At less than two seconds to impact?
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Old 28th Jul 2017, 23:48
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Curious why Captain would report Pitch? At less than two seconds to impact?
For a person who suspects he about to meet his maker, and doesn't know exactly how he got in that fix, that action is about the only choice left. It is too late to put the nose down and gain speed. From the Captain's viewpoint, if the plane was (possibly) actually flying, and the control system was (possibly) mis-behaving, then how else could you hope to level out/reduce the rate of sink.

Only problem was, as we know from our use of the retrospectoscope, they were deeply stalled and setting a climb attitude was like re-arranging the chairs on the deck of the Titantic.
Totally Useless!
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Old 29th Jul 2017, 14:35
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I agree. My sense of his (final) comment was that it was a "reset" of "SA". On the chance the VSI was duff, the stubborn attitude was bogus, etc.
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Old 29th Jul 2017, 14:51
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Originally Posted by Centaurus
It should not be forgotten that the original concept behind flight director use was that it was an aid to instrument flying and nothing else.

Unfortunately over the years, that concept has morphed [...]
I am not sure it is the concept that has changed, but rather the users and their understanding of the concept. A workload reduction tool does something for you, but it is actually just a small change of interpretation/perspective between that and a tool that tells you what to do.

<begin rant (sort of)>

I think this is an inherent problem in human interface design - you are designing for an extremely adaptable animal, not just a moving target but an unpredictable one. It is also a generational issue, each generation trains the next - what is designed, successfully, as a workload reduction for the first generation (who lived without it) becomes a crutch for the next (who know how to live without it, but haven't had to) and for subsequent generations it becomes their master, because they have never even known of a life without it.

In aviation the generations are actually quite long - aircraft last for decades, aircraft _designs_ last for decades longer, but in other fields you can see this effect go through every stage in a handful of years. Particularly true in software where product UI can change radically between releases, in maybe less than a year, and where customers have users training users with the whole staff turning over every couple of years. In fact I didn't do UI when I did flying software, and it was only after seeing this sort of thing happen in other fields that I looked back at Children of the Magenta Line and really understood how widely it applies.

If there was some way to strip the aviation-specific language out of Children of the Magenta Line and generalise while keeping the impact of the talk, I would make that video mandatory viewing for any user or customer who asks for UI changes to make stuff "easier" or "reduce workload" (by which they almost always mean "so we can use fewer, cheaper, less trained people").

<End of rant, back to lurking>
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Old 29th Jul 2017, 15:12
  #1545 (permalink)  
 
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Originally Posted by Infrequentflyer789
I think this is an inherent problem in human interface design - you are designing for an extremely adaptable animal, not just a moving target but an unpredictable one. It is also a generational issue, each generation trains the next - what is designed, successfully, as a workload reduction for the first generation (who lived without it) becomes a crutch for the next (who know how to live without it, but haven't had to) and for subsequent generations it becomes their master, because they have never even known of a life without it.
Hit the nail on the head!
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Old 29th Jul 2017, 16:38
  #1546 (permalink)  
 
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The danger is in the immediacy and the necessity to adapt to an environment that does not care about the interface.

Where the operating system meets intuition, that is the conflict. For too long the industry has travelled a road that frequently overlooks and diminishes the skills needed for intuitive operation in (thankfully rare) emergent conditions.

It is at its most apparent in the relinquishing of a traditional dependence on craft.

447 is instructive...

"Do nothing, read a newspaper..." OK. One cannot have it both ways: leave it alone, or utilize skills that have become vestigial and are dismissed as unnecessary.

One cannot claim a system (an aircraft) can be operated by minimally trained operators, then savage said operators when clearly old skills would have helped, and they were lacking.

Especially so when the system enters a mode that is not known, and recovery is not traditional....(or trained).

With the greatest respect.
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Old 29th Jul 2017, 19:20
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I think this is an inherent problem in human interface design
Problem solved. Bombardier CSeries designed the FBW as an energy-based control system that mimics the basics of how pilots learn to fly. When trimmed out, the aircraft will attempt to maintain that speed despite changes in power. If the power is lower than needed, the aircraft will descent, and vice versa, but the speed will attempt to remain constant, naturally. Bombardier modified the C* (C-star) FBW design control system to be speed-stable, meaning that the pilot is kept in the loop to maintain a speed set by using the trim switches at the top of the sidestick: “It's much more intuitive and flies much more like a conventional aircraft,” says Dewar. Compared to the Airbus FBW, where you trim to an attitude and it holds it, here you trim to an airspeed.”
Just watch the stick movements in video below:

CS300 Multicam Cockpit Landing
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Old 29th Jul 2017, 19:56
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Originally Posted by _Phoenix
Bombardier modified the C* (C-star) FBW design control system to be speed-stable,
This is what's also in use by the 777 and 787. C*U
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Old 30th Jul 2017, 14:27
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Compared to the Airbus FBW, where you trim to an attitude and it holds it.
Really? No! you don't trim at all. The aircraft does and that too not the attitude but maintains the flight path. It's not the same as attitude. It doesn't hold the attitude.
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Old 30th Jul 2017, 14:37
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That got Bonin in trouble...The commanded flight path in manual was up, up, up.

And it took all the aircraft had in trim to hold. In ascent, and in descent.
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Old 30th Jul 2017, 15:08
  #1551 (permalink)  
 
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Trouble

No, not the aircraft brought Bonin into trouble, Bonin brought the aircraft into trouble.

Everyone who pulls and holds full back stick in an airliner will bring that airliner down - works in any type, from any manufacturer.

Want to see the list again?
A B-727 with blocked pitot tubes in the nineteen-seventies.
A B-757 of Birgenair with blocked pitot tubes, where the autopilot maintained nose up and the autothrottle powered back (to keep the false speed indication below the limit)
MD-82 over Venezuela in 2005 and MD-83 over Mali in 2014.

Works whether the aircraft is equipped with Fly By Wire, or with "old fashioned cables", with interconnected yokes, or non-connected sidesticks, gues what, would even work in a single seater with only one set of flight controls, works with or without auto trim function; by the way, even a non-Airbus aircraft autotrims as long as the autopilot is in control, and, as in Mali, that could be up until the stall and wingdip.
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Old 30th Jul 2017, 15:51
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Poor grammar, Bonin indeed, not the A/C.

You miss one thing. The A330 is so adept and docile, it maintains the flight path through stall, without change in attitude, not consistent with its advertised fbw? So it morphs from flight path stable, to attitude stable in Stall, no? At least functionally, if not by design...

This is more the responsibility of the THS, to maintain good manners at +40 AoA?

"...by the way, even a non-Airbus aircraft autotrims as long as the autopilot is in control, and, as in Mali, that could be up until the stall and wing dip.."

Yes but AP was not flying. Manual flight for Bonin. Also in manual, the goal is to remain stable, to maneuver, not to cruise. Why Auto Trim for manual flight? The goal is maneuverability and stability, which demands equal authority in Pitch, not Nose Up or Down bias. Certainly not in low energy flight?

Airbus has added LEAP, an important safety improvement.... (Low Energy Alerting System)
Would an alert of low energy (STALL) separate from the STALLWARN have helped?

Last edited by Concours77; 30th Jul 2017 at 16:14.
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Old 30th Jul 2017, 16:52
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Airbus has added LEAP, an important safety improvement.... (Low Energy Alerting System)
Would an alert of low energy (STALL) separate from the STALLWARN have helped?
It is not called LEAP. It's just called low energy warning. It is not available in Alternate law that's what AF447 was in. Nothing would have helped Bonin. He and his partner were simply not trained appropriately enough to deal with the situation and were overwhelmed. They put the aircraft in a region where no commercial aircraft is tested. It futile to discuss this incident.
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Old 30th Jul 2017, 20:07
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With great respect, commercial jet aircraft are indeed tested, laboriously and especially in this region.

Approach to Stall cannot, must not be left untested, nor can an aircraft be certified to carry passengers without demonstrating standard recovery responses.

It could be suggested that seven seconds past loss of AP began the long approach to the Stall, a Stall which is unlike other aircraft, and in no way "standard".

In the eight years and change since this horrific accident, literally all the discussion here is limited to hind sight, sensitive ego, and grandiosity.

The data is clear, but its impact on the crew virtually unknown.

Instead of a curiosity about how this aircraft entered and stubbornly sustained a docile and passive Stall, the "analysis" is quite limited in scope.

No discussion of the certification of AB FBW, and how they achieved a waiver of safety devices? Shaker? Pusher? No discussion of what the flight path result derived from related to handling in LOC (gentle? No natural Nose Down, etc.)

No review and analysis of Mr Winnerhofers video of the AB Stall training video?

Crickets.

It is troublesome, the willingness to post "Don't go there....it's futile..."

Futility was in evidence in their descent, with ten thousand hours, collectively, of Time in Type?

But you are correct, it is futile, and I've completed my responsibility....

Thank you for your patience, and kindness in responding to my concerns....
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Old 30th Jul 2017, 22:00
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Originally Posted by Concours77
With great respect, commercial jet aircraft are indeed tested, laboriously and especially in this region.

Approach to Stall cannot, must not be left untested, nor can an aircraft be certified to carry passengers without demonstrating standard recovery responses.
Pretty sure that the "untested" region he's talking about is the ~40 deg AOA deep stall that the plane was in, not "approach to stall"


Futility was in evidence in their descent, with ten thousand hours, collectively, of Time in Type?
I would not expect them to be any more capable of recovering from the situation with that ten thousand hours of experience, than their first hour in the plane. After all, what would have happened in the intervening 9,999 hours to better prepare them? 9,999 standard takeoff and approach profiles? A few million stick back inputs where the airplane reliably went up as a consequence, each and every time? A couple of dozen recurrents in the sim where they applied power and held the nose in place in a "minimum altitude loss" type stall recovery? Yeah right, those hours made them worse, not better, prepared than a freshly minted private pilot.

It's not time in type that matters, but time in stall.

Last edited by Vessbot; 31st Jul 2017 at 16:27.
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Old 31st Jul 2017, 00:30
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"...It's not time in type that matters, but time in stall..."

Without question, and without disagreement. Likely no A330 crew will realize, or come to rely upon, the bizarre disguised Stall Entry of 447.

Gliders? Pitts? Extra? That time similarly makes for counterintuitive response to 330 Stall Entry....no change in Pitch, buffet easily confused with turbulence, and partial loss of roll control.... Full Nose Up trim without command (in manual), etc.

Perhaps better to enlist PPLs to fly this family? At least the Stall would be no less baffling to them. Perhaps retire them out of type after 2000 hours?

I thank you for your feedback, for I believe too much is left unsaid, the conclusion too pedestrian.

This was a challenge for any crew, that the holes lined up so well is their fate. Even a maladjusted seat and deployed armrest deserves some weight. All counter points neglected in the interest of peace...
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Old 31st Jul 2017, 06:37
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When I converted onto the A330, prior to this accident. Stalls done on the simulator were conventional. Holding s/stick back in alt law caused buffet and then a significant nose drop.
I am therefore not surprised that this unfortunate crew did not recognise the stall.
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Old 31st Jul 2017, 11:25
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Approach to Stall cannot, must not be left untested
Approach to stall? At FL370 if you yank the stick back the aircraft will be in region where it is not tested. That is why airbus forbids practicing deep stalls in Sim because there's no data available to make realistic simulation.
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Old 31st Jul 2017, 12:55
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if airbus likes their alpha prot so much maybe they should just enable it despite of lost pitots.
not sure how feasible that is though.

also having 2 very different roll behaviors obviously was a problem and major time consumer for the pilots. don't know either why roll input can't stay at roll rate ... the internal gyros where not affected afterall. either you unify the behavior of the aircraft or you need quite a bit more training for what are essentially two very different feeling planes.
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Old 31st Jul 2017, 14:58
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Originally Posted by vilas
Approach to stall? At FL370 if you yank the stick back the aircraft will be in region where it is not tested. That is why airbus forbids practicing deep stalls in Sim because there's no data available to make realistic simulation.
From the report, Bonin's second brisk command in Pitch was Nose Down. Halfway through stick travel to neutral, the STALLWARN activated. He did not create the first SW by "yanking stick back". That is an airborne myth.

Please see Winnerhofer's post of the Stall training video issued by the company.

No Nose Drop, just loss of altitude from level. How long into Stall does "deep" Stall occur? From your comment, untrained deep Stall with gentle unremarkable entry is without precedent, by design.


Unfamiliar? An unobtrusive and untrained passive entry to Stall might confuse anyone? It is without contradiction that Stall was rejected by crew.

Once in very high AoA, any Nose Down produces remarkable acceleration and negative g. Sufficient to cause reversal by pilot of ND command. The record shows this? Add to this the return of STALLSTALL, and recovery is foreclosed, demonstrably....
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