AF 447 Thread No. 6
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The THS kept going due lack of Pilot input. In other words, it autoed into the STALL.
That's called non-cognitive runaway TRIM. Un-commanded in the first place, but requiring a command to stop.
Arse about.
Someone, please define "TRAP".
That's called non-cognitive runaway TRIM. Un-commanded in the first place, but requiring a command to stop.
Arse about.
Someone, please define "TRAP".
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System Engineering Design Philosophy
Automation helps but can create very dangerous situations as all of us know. This danger increases when the designers creates “tools” to help the operator introducing a “partner” with high hierarchy. Protections are excellent when designed to preserve limits (e.g. Rudder Travel limiter, etc.) But can generate adverse effects not to mention the “de skilling” potential.
IMO, under stress (normal in many situations) even a designer would be confused.
All good Engineers apply confidently WHAT IS NECESSARY to implement a required function. My concern is concentrated in the Top System Engineering approach simply because impacts everything. And cannot be corrected (or tweaked) by SW or even HW fixes.
They are learning and their leadership in this area requires more R&D. My concern is if the commercial success will allow the investment in areas with clear room for improvement, as you mention.
I bring the Finite States Machines because the "partner" introduced to the crew has this structure. Very powerful and increasingly present in our lives. And because they must be well designed and normally requires evolution.
This was not the case in TAM 3054 plane and the other similar cases before.
Think you would be confused?
Make no mistake, I do not advocate a simple, direct control of the various aero surfaces such as some here believe would save the day.
My problem has always been with the "autopilot" type functions and protections that seem inherent in the 'bus FBW design and its reversion modes.
I bring the Finite States Machines because the "partner" introduced to the crew has this structure. Very powerful and increasingly present in our lives. And because they must be well designed and normally requires evolution.
This was not the case in TAM 3054 plane and the other similar cases before.
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T.R.A.P.
Trimmable Resource Automatically Positioned
PS
The designers made the algorithms. And the a/c' s really (BEA said) worked as designed.
Question:
The crew (under stress) of AF 447 and TAM 3054 did receive ADEQUATE real time indication on the IMPORTANT (auto) configs, respectively of THS (in an stalled a/c) and eng#2 PWR after touch down (landing)?
Observe in both cases i am not even suggesting this as the main cause of the accidents.
i am just commenting the danger of auto (pre programmed) functions that apparently don't respect how rich is reality faced by us. And the potentiality (risks) of complex systems to perform as K.I.C.S. mechanisms. Just the opposite intended by the designers.
C. stand for Complex
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Depends on your definition of "Automatic" - it moved because the PF commanded it to move. If he wasn't aware that he was commanding it to move, then that was a fault in his training - not the aircraft, for which plenty of documentation on the functions of autotrim in both Normal and Alternate Law is available even to non-pilots.
The designers made the algorithms. And the a/c' s really (BEA said) worked as designed.
The crew (under stress) of AF 447 and TAM 3054 did receive ADEQUATE real time indication on the IMPORTANT (auto) configs, respectively of THS (in an stalled a/c) and eng#2 PWR after touch down (landing)?
i am just commenting the danger of auto (pre programmed) functions that apparently don't respect how rich is reality faced by us. And the potentiality (risks) of complex systems to perform as K.I.C.S. mechanisms. Just the opposite intended by the designers.
C. stand for Complex
C. stand for Complex
In the case of TAM, if you only move one thrust lever to idle on a conventional aircraft, the engine controlled by the other thrust lever will continue to produce power just the same as it did in that case. It was likely there was no "confusion" on the part of the crew as to why they were using the old and deprecated method - because at least one of them knew that it stopped the aircraft faster. It was just unfortunate that in adopting that method that they made the same mistake that caused the old method to be deprecated in the first place.
I don't think systems complexity had a great deal to do with either case, notwithstanding the fact that there is no such thing as a "simple" system to control a modern airliner.
HAL and sfwe and protections
No problem here with HAL until HAL starts to get in the way of what we pilots believe, actually BELIEVE, what we need to do and HAL gets in the way because HAL is programmed to PROTECT us. 'nuf there, so on....
INSERT: Alaska airlines THS accident not relevant here, as it was a clear mechanical problem and the crew tried everything in the book and some neat techniques until all was lost..
The 'bus reversion sequence appears to preserve many "autopilot" functions until all else turns to worms ( old fighter pilot phrase, so excuse me). Fer chrissakes, the jet seems to be very docile and has inherent spin resistance and such. There should only be two "laws" - autopilot and manual. The Otto limits could also be the "manual" ones, but the pilot inputs would be from the pilots and not some confuser. So retain the overspeed and AoA warnings. Let the pilots fly as they wish, but don't allow HAL to keep trying to "protect" them.
Problem with the 'bus is after A/P disconnects for whatever reason the pilot may think he/she has the "protections" that existed just a second before. Not so. The "autotrim" function still is active, and the alpha prot feature can be confused or even disabled when HAL decides that air data is unreliable.
What the pilots need is something to hang their hats on when the autopilot functions and all the layers of "protections" are invalid.
To Doze:
Many of the sfwe-illiterate pilots, and even anti-sfwe folks can provide bad inputs to the sfwe folks. I have some great war stories about the shuttle folks when NASA implemented the HUD for that beast. My roomie helped get the one you all saw a few months ago on its last landing.
As a systems engineer that wrote the spec for the sfwe folks to implement I always explained our rationale. I was open to tweaks and helpful features. But I basically used the state machine concept that RR has crowed about. And I am a disciple of the finite state machine for many implementations, especially those involving nuclear weapons and flight control systems.
We can discuss this issue privately, or we can create a new thread.
INSERT: Alaska airlines THS accident not relevant here, as it was a clear mechanical problem and the crew tried everything in the book and some neat techniques until all was lost..
The 'bus reversion sequence appears to preserve many "autopilot" functions until all else turns to worms ( old fighter pilot phrase, so excuse me). Fer chrissakes, the jet seems to be very docile and has inherent spin resistance and such. There should only be two "laws" - autopilot and manual. The Otto limits could also be the "manual" ones, but the pilot inputs would be from the pilots and not some confuser. So retain the overspeed and AoA warnings. Let the pilots fly as they wish, but don't allow HAL to keep trying to "protect" them.
Problem with the 'bus is after A/P disconnects for whatever reason the pilot may think he/she has the "protections" that existed just a second before. Not so. The "autotrim" function still is active, and the alpha prot feature can be confused or even disabled when HAL decides that air data is unreliable.
What the pilots need is something to hang their hats on when the autopilot functions and all the layers of "protections" are invalid.
To Doze:
Many of the sfwe-illiterate pilots, and even anti-sfwe folks can provide bad inputs to the sfwe folks. I have some great war stories about the shuttle folks when NASA implemented the HUD for that beast. My roomie helped get the one you all saw a few months ago on its last landing.
As a systems engineer that wrote the spec for the sfwe folks to implement I always explained our rationale. I was open to tweaks and helpful features. But I basically used the state machine concept that RR has crowed about. And I am a disciple of the finite state machine for many implementations, especially those involving nuclear weapons and flight control systems.
We can discuss this issue privately, or we can create a new thread.
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INSERT: Alaska airlines THS accident not relevant here, as it was a clear mechanical problem and the crew tried everything in the book and some neat techniques until all was lost..
The 'bus reversion sequence appears to preserve many "autopilot" functions until all else turns to worms ( old fighter pilot phrase, so excuse me). Fer chrissakes, the jet seems to be very docile and has inherent spin resistance and such. There should only be two "laws" - autopilot and manual. The Otto limits could also be the "manual" ones, but the pilot inputs would be from the pilots and not some confuser. So retain the overspeed and AoA warnings. Let the pilots fly as they wish, but don't allow HAL to keep trying to "protect" them.
With all due respect, I find "confuser" as infuriating as "HAL". If I started using derogatory terms for pilots in the same manner I'd be banned before too long. I go out of my way to show respect to the pro flyers on here, and I don't think it's unfair to request a bit of common courtesy in return.
Problem with the 'bus is after A/P disconnects for whatever reason the pilot may think he/she has the "protections" that existed just a second before. Not so. The "autotrim" function still is active, and the alpha prot feature can be confused or even disabled when HAL decides that air data is unreliable.
What the pilots need is something to hang their hats on when the autopilot functions and all the layers of "protections" are invalid.
Many of the sfwe-illiterate pilots, and even anti-sfwe folks can provide bad inputs to the sfwe folks. I have some great war stories about the shuttle folks when NASA implemented the HUD for that beast. My roomie helped get the one you all saw a few months ago on its last landing.
We can discuss this issue privately, or we can create a new thread.
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Some people here seem to be ascribing far more complexity and "intelligence" to the aircraft systems than is actually present.
This is leading them into the trap of blaming the designers for not considering rule A (do not trim up if AOA >X, Alt = Y, airspeed = Z) which apparently is perfectly obvious (with hindsight from an armchair - 3 real pilots on the night didn't find it obvious...). Thinking the designers screwed up because the system is too complex, they demand it be made simpler, not realising that it is already far simpler than they realise, and far too simple to implement the rules they've asked for.
The autotrim simply moves THS, limited by stops, to unload the elevator - with a bit of hysteresis thrown in (probably thresholds on elevator displacements and time).
The pilots may stop / override autotrim, and other systems on the plane may stop autotrim. Various protections may stop (or limit) the autotrim, and the higher level mode/law state may switch those protections on or off, or switch off autotrim itself (off in direct law).
Autotrim did what the pilots asked simply because that is what it does, and nothing told it to stop. It didn't look at the pilot input and the AOA and the current law/state and decide it oughtto move because law=alt even though AOA > stalled.
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THS didn't auto into the stall either. Look at the traces. Stall was achieved with elevator alone.
Inadvertently stall a big jet and you've already got a big chance of dying (odds are bad enough even in GA). Do it with no outside visual reference, some already broken instruments and in turbulence in middle of a cb... and your chances are probably <10% at best (at an optimistic guess). By the time the THS started moving, they were already well into a trap and needing a miracle.
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Quite where gums gets his information on AF training procedures I am not sure, but he sounds awfully certain.
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Common factor - suprise auto dropout. Let's hit the pilot with stall warning and at the same time disconnect the biggest pitch control surface from the stick, so the pilot needs two controls for pitch where a moment ago it was just one...
Is that really the best user interface ?
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Originally Posted by IF789
Is that really the best user interface ?
- Auto trim under Auto pilot
- But Manual trim under Manual flight
If the pilot quits trimming when he should not … then he might have to pay the price but let’s not pretend to build the perfect aircraft that will solve all.
As a pilot I need a simple tool I can understand and trust.
Don’t make it more clever than necessary.
Train me properly on it.
Thank you, Conf.
When I read the 'bus "manuals" and such that we have had provided here, I see a plethora of reversion "laws" that are not really "laws". They are simply less restrictions on bank angle, pitch attitude, a few AoA functions and associated "warning" chimes or whatever, and the beat goes on.
My main point is that the pilots need both understanding of the system and the flying/handling characteristics of the jet when they aren't sitting there "managing" systems. So Conf's statement rings home to this old pilot. Some of us are not anti-computer or anti-FBW or anti-anything. We just need to know when we have control or HAL is getting in the way.
The "basic" control laws of the 'bus must be made clear, and there just seems to me that those basic laws are not well-known amongst the crews, and the warnings and advisory stuff does not reflect the actual aero condition of the jet when it loses a sensor or two.
BTW, I use the term "HAL" because it implies some artificial intelligence on the part of the basic FBW system design I have seen in the 'bus manuals we have had linked to here. And I don't like it.
There are "limits" and "protections" but I am not sure that the system clearly distinguishes which is which as far as the pilot understands.
I still maintain that too many "limits" are embedded in the reversion sequences that are not necessary for safely flying the jet when we have such a simple failure as pitot-static system problems. We don't need a direct control of the elevator or ailerons/spoilers as if we were flying a P-51 70 years ago. I see too many "protections" embedded in the control laws of the 'bus that are not necessary for basic flying the jet, and they can cause confusion for the pilots when sierra happens.
I am not sure that all the 'bus "limits" were specified by pilots. My gut feeling is that the FBW design offered an opportunity to do "neat" things, and the sfwe folks went with a few suggestions. The emphasis upon auto-everything except putting on the brakes after touchdown and steering the jet to the ramp bothers me.
When I read the 'bus "manuals" and such that we have had provided here, I see a plethora of reversion "laws" that are not really "laws". They are simply less restrictions on bank angle, pitch attitude, a few AoA functions and associated "warning" chimes or whatever, and the beat goes on.
My main point is that the pilots need both understanding of the system and the flying/handling characteristics of the jet when they aren't sitting there "managing" systems. So Conf's statement rings home to this old pilot. Some of us are not anti-computer or anti-FBW or anti-anything. We just need to know when we have control or HAL is getting in the way.
The "basic" control laws of the 'bus must be made clear, and there just seems to me that those basic laws are not well-known amongst the crews, and the warnings and advisory stuff does not reflect the actual aero condition of the jet when it loses a sensor or two.
BTW, I use the term "HAL" because it implies some artificial intelligence on the part of the basic FBW system design I have seen in the 'bus manuals we have had linked to here. And I don't like it.
There are "limits" and "protections" but I am not sure that the system clearly distinguishes which is which as far as the pilot understands.
I still maintain that too many "limits" are embedded in the reversion sequences that are not necessary for safely flying the jet when we have such a simple failure as pitot-static system problems. We don't need a direct control of the elevator or ailerons/spoilers as if we were flying a P-51 70 years ago. I see too many "protections" embedded in the control laws of the 'bus that are not necessary for basic flying the jet, and they can cause confusion for the pilots when sierra happens.
I am not sure that all the 'bus "limits" were specified by pilots. My gut feeling is that the FBW design offered an opportunity to do "neat" things, and the sfwe folks went with a few suggestions. The emphasis upon auto-everything except putting on the brakes after touchdown and steering the jet to the ramp bothers me.
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Also, CONF is a long-time hater of everything the 'bus stands for, so of course he's going to say that. To clarify for CONF, here's the supposedly "ambiguous" list of trim auto/manual status:
Normal : Auto
Alternate : Auto
Direct : Manual
RR_NDB claims that the Airbus system is an example of "Top [Down] Engineering", whereas in fact I was told it was a classic example of Top-Down specification with Bottom-Up implementation - meeting in the middle, which a lot of engineers claim is the most effective way to do things. The whole idea behind the "Laws" was to present a relatively easy set of mnemonics for pilots to understand the aircraft status - as such the A320 was the first airliner to attempt to address the problem of a non-normal situation increasing workload on the pilots in a 2-crew flight deck.
In the days of 3-crew operation, the Flight Engineer was expected to know the systems intimately, along with all the failure mode combinations and settings to maintain safe flight when those failures occurred. The only reason Alternate Law has sub-modes is because that knowledge of the systems is coded into the FCU logic - I'll say it again here - all a pilot really has to remember about Alternate Law is that there are no hard protections and that more care has to be taken to ensure flight envelope limits are not exceeded. If that's too complicated for the average pilot to understand, it's a wonder any pilot ever passed their IR*.
The implementation was "Bottom-Up" in the sense that Direct Law is the first layer of abstraction, providing straightforward control of the surfaces via digital means. Alternate was the next layer, roughly analogous to the old A300/A310 protections which activated only when the pilots let go of the controls. Normal was the third and final layer, which added the advanced FCU protections that made the Airbus FBW series seem like such an advance - when it was in fact only an iterative improvement over the previous generation.
Even the supposedly more "pilot-centred" B777 has more than just "manual" and "autopilot" modes, and again as I've said before, the force-feedback logic is itself far more complicated under the hood than anything in any of the A320's systems.
[* - Note to those for whom English is a second language - what I'm actually saying here is that I don't believe that the average pilot would find the flight control law system on the Airbus FBW series too complex to understand.]
Last edited by DozyWannabe; 2nd Oct 2011 at 13:54.
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Hi,
Always interesting to visit the BEA site
The last communication at 30 September : (in french)
http://bea.aero/fr/enquetes/vol.af.4...re.2011.fr.pdf
The BEA said that he is the sole authority to provide information on a
investigation it has opened following an accident or incident
It seems presumptuous ....
Or maybe it is a warning to employees of BEA (from which the majority of leaks come)
The BEA notes that repeatedly working papers relating to
safety investigation with information being uncommitted,
covered by professional secrecy are disclosed to the media, for
other than safety investigation.
BEA read Pprune .. ? or this .. ?
AF447 « AF447
Always interesting to visit the BEA site
The last communication at 30 September : (in french)
http://bea.aero/fr/enquetes/vol.af.4...re.2011.fr.pdf
Le BEA constate que de façon récurrente des documents de travail relatifs à des
enquêtes de sécurité en cours contenant des informations non validées,
couvertes par le secret professionnel, sont divulgués auprès des media, à des fins
autres que l’enquête de sécurité.
C’est pourquoi, le BEA rappelle aux acteurs concernés que :
- le seul objet de ces enquêtes de sécurité est d’établir les circonstances précises
et de déterminer les causes de l’accident ou de l’incident et d’en tirer des
enseignements de sécurité ;
- l’enquête de sécurité nécessite un travail long et rigoureux conclu par la
publication d’un rapport final.
Les affirmations partielles, erronées et sorties de leur contexte rapportées aux
journalistes, tant que l’enquête n’est pas terminée, donnent lieu à des
interprétations et spéculations, qui ne peuvent que troubler le public et engendrer
la polémique entre les acteurs concernés.
Le BEA rappelle qu’il est le seul habilité à donner des informations sur une
enquête qu’il a ouverte à la suite d’un accident ou d’un incident.
enquêtes de sécurité en cours contenant des informations non validées,
couvertes par le secret professionnel, sont divulgués auprès des media, à des fins
autres que l’enquête de sécurité.
C’est pourquoi, le BEA rappelle aux acteurs concernés que :
- le seul objet de ces enquêtes de sécurité est d’établir les circonstances précises
et de déterminer les causes de l’accident ou de l’incident et d’en tirer des
enseignements de sécurité ;
- l’enquête de sécurité nécessite un travail long et rigoureux conclu par la
publication d’un rapport final.
Les affirmations partielles, erronées et sorties de leur contexte rapportées aux
journalistes, tant que l’enquête n’est pas terminée, donnent lieu à des
interprétations et spéculations, qui ne peuvent que troubler le public et engendrer
la polémique entre les acteurs concernés.
Le BEA rappelle qu’il est le seul habilité à donner des informations sur une
enquête qu’il a ouverte à la suite d’un accident ou d’un incident.
The BEA notes that repeatedly working papers relating to
safety investigation with information being uncommitted,
covered by professional secrecy are disclosed to the media, for
other than safety investigation.
Therefore, BEA reminded stakeholders that:
- The only purpose of the safety investigation is to establish the precise circumstances
and to determine the cause of the accident or incident and to draw
safety lessons;
- The security screening requires a long and rigorous concluded by the
publication of a final report.
The claims partial, inaccurate and out of context to reported
journalists, until the investigation is not over, give rise to
interpretations and speculations, which can only confuse the public and lead
the controversy between the parties concerned.
The BEA said that he is the sole authority to provide information on a
investigation it has opened following an accident or incident.
safety investigation with information being uncommitted,
covered by professional secrecy are disclosed to the media, for
other than safety investigation.
Therefore, BEA reminded stakeholders that:
- The only purpose of the safety investigation is to establish the precise circumstances
and to determine the cause of the accident or incident and to draw
safety lessons;
- The security screening requires a long and rigorous concluded by the
publication of a final report.
The claims partial, inaccurate and out of context to reported
journalists, until the investigation is not over, give rise to
interpretations and speculations, which can only confuse the public and lead
the controversy between the parties concerned.
The BEA said that he is the sole authority to provide information on a
investigation it has opened following an accident or incident.
investigation it has opened following an accident or incident
It seems presumptuous ....
Or maybe it is a warning to employees of BEA (from which the majority of leaks come)
The BEA notes that repeatedly working papers relating to
safety investigation with information being uncommitted,
covered by professional secrecy are disclosed to the media, for
other than safety investigation.
BEA read Pprune .. ? or this .. ?
AF447 « AF447
Last edited by jcjeant; 2nd Oct 2011 at 13:34.
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Originally posted by gums :
The emphasis upon auto-everything except putting on the brakes after touchdown and steering the jet to the ramp bothers me.
The emphasis upon auto-everything except putting on the brakes after touchdown and steering the jet to the ramp bothers me.
They even invented a "brake to vacate" gadget on the A 380 to "program" the runway exit point after touch down.
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infrequentflyer789
You're not wrong, and I know what you're saying. For the moment, consider that the Pilot flying after a/p loss was working his theory "I think we have some crazy speed.."
Repeating how the aircraft behaves with its trim doesn't help an understanding.
From the releases and FDR data, we believe the a/c was NOT oversped, and all the UP elevator was the pilot's.
He made a mistake. A mistake he appears to have held on to for the rest of the flight. We know this because at the very last, when the Captain tells him "Climb", he says "But I have held back stick for some time."
You want to go straight to "What Morons"? Feel free, but the a/c is part of the crash, and how she gets along with her crew is (seems) to be the cause of this crash.
More important is what caused the PF to believe the a/c was fast. Guessing won't do, and chiding a dead man solves nothing.
FYI. The 54 seconds of STALL annunciation comes from the DFDR. Call me old fashioned, but until I hear it on the CVR I consider the jury to be OUT.
No offense, but proof is needed.
We know that the a/c recovers from STALL with elevators DOWN and full UP THS. So if the elevators are effective, why did someone decide that on the way up, Trim was necessary? And should be Auto?
You're not wrong, and I know what you're saying. For the moment, consider that the Pilot flying after a/p loss was working his theory "I think we have some crazy speed.."
Repeating how the aircraft behaves with its trim doesn't help an understanding.
From the releases and FDR data, we believe the a/c was NOT oversped, and all the UP elevator was the pilot's.
He made a mistake. A mistake he appears to have held on to for the rest of the flight. We know this because at the very last, when the Captain tells him "Climb", he says "But I have held back stick for some time."
You want to go straight to "What Morons"? Feel free, but the a/c is part of the crash, and how she gets along with her crew is (seems) to be the cause of this crash.
More important is what caused the PF to believe the a/c was fast. Guessing won't do, and chiding a dead man solves nothing.
FYI. The 54 seconds of STALL annunciation comes from the DFDR. Call me old fashioned, but until I hear it on the CVR I consider the jury to be OUT.
No offense, but proof is needed.
We know that the a/c recovers from STALL with elevators DOWN and full UP THS. So if the elevators are effective, why did someone decide that on the way up, Trim was necessary? And should be Auto?
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Originally Posted by DozyWannabe
Also, CONF is a long-time hater of everything the 'bus stands for, so of course he's going to say that.
Behave your comments please.
Or is it supposed to be the ultimate argument when things don’t go your way ?
Working on the Airbus is my job, maybe I have some credential to appreciate what could be better on it.
Do not take it too personal if critics are formulated towards Airbus.
To clarify for CONF, here's the supposedly "ambiguous" list of trim auto/manual status:
Normal : Auto
Alternate : Auto
Direct : Manual
Normal : Auto
Alternate : Auto
Direct : Manual
Put as many laws as you like but leave to the pilot to trim when he’s manually flying.
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