Air Asia Indonesia Lost Contact from Surabaya to Singapore
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Many thanks, Safetypee and RDMII, for enlightening discussion. SP: "unless there is a change in safety views and processes"; RMDII: "change in approach concerning the question, Why do "accidents" still occur?" What would such a change - or changes (plural) - look like? (and if that question seems impertinently stated, then, is it even a useful question to ask, "is the present system moving in the right direction for such change or changes to occur?")
The "How Complex Systems Fail" article (the link to which SP provided) is at least 15 years old - can't help but wonder, how have any more current analyses looked at the overall complexity construct?... any differently, or differently in ways relevant to the general subject matter of the thread?
Also couldn't help but note a slight, not objection, but "reservation" about seeing ICAO Annex 13 as an "oversight" process or method relative to nationally-authorized safety boards or agencies (but it's not too important to discuss further right now).
Reading comments by RDMII & Safetypee over again, was reminded of the not-too-long ago ICAO Loss of Control In-Flight Symposium (May 20-22, 2014). Exclusively in the interest of contributing, possibly, to the discussion of safety improvements (however difficult those may be to identify, enunciate and make happen), much info apparently very relevant to observations by prior posters is listed in the Symposium program and Key Outcomes (presentation powerpoints also can be accessed - though lacking the intensity of videos of flight parameters - slides only).
The program for the Symposium:
http://www.icao.int/Meetings/LOCI/Do...enda_FINAL.pdf
and Key Outcomes:
http://www.icao.int/Meetings/LOCI/Do...20Outcomes.pdf
The "How Complex Systems Fail" article (the link to which SP provided) is at least 15 years old - can't help but wonder, how have any more current analyses looked at the overall complexity construct?... any differently, or differently in ways relevant to the general subject matter of the thread?
Also couldn't help but note a slight, not objection, but "reservation" about seeing ICAO Annex 13 as an "oversight" process or method relative to nationally-authorized safety boards or agencies (but it's not too important to discuss further right now).
Reading comments by RDMII & Safetypee over again, was reminded of the not-too-long ago ICAO Loss of Control In-Flight Symposium (May 20-22, 2014). Exclusively in the interest of contributing, possibly, to the discussion of safety improvements (however difficult those may be to identify, enunciate and make happen), much info apparently very relevant to observations by prior posters is listed in the Symposium program and Key Outcomes (presentation powerpoints also can be accessed - though lacking the intensity of videos of flight parameters - slides only).
The program for the Symposium:
http://www.icao.int/Meetings/LOCI/Do...enda_FINAL.pdf
and Key Outcomes:
http://www.icao.int/Meetings/LOCI/Do...20Outcomes.pdf
Control law reversion, etc
@ Phoenix.......
Good video links.
The point about "direct" is that the computers still bias your control stick deflection or pressure using some math function.
Is one degree of stick deflection equal one degree of elevator deflection? If not, what is the ratio?
Is ten pounds of stick force about like we used to feel with the fully hydraulic systems ( no mechanical linkages, just hydraulic pressure to move an actuator) that used pneumatic and spring doofers to provide a bit of feel. And BTW, are the stick movements at the same pressure regardless of how many degrees they move?
I have no problem with the test pilots using some DIRECT implentation initially, then going to the NORMAL mode. But I have no idea of the gains or control input ratios to control surface movement or even how fast they move ( rate of surface movement).
Hooray for Bombardier. I like their approach.
But I still wannna see some charts and graphs.
Good video links.
The point about "direct" is that the computers still bias your control stick deflection or pressure using some math function.
Is one degree of stick deflection equal one degree of elevator deflection? If not, what is the ratio?
Is ten pounds of stick force about like we used to feel with the fully hydraulic systems ( no mechanical linkages, just hydraulic pressure to move an actuator) that used pneumatic and spring doofers to provide a bit of feel. And BTW, are the stick movements at the same pressure regardless of how many degrees they move?
I have no problem with the test pilots using some DIRECT implentation initially, then going to the NORMAL mode. But I have no idea of the gains or control input ratios to control surface movement or even how fast they move ( rate of surface movement).
Hooray for Bombardier. I like their approach.
But I still wannna see some charts and graphs.
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If it's not possible to link sticks mechanically, disallow for dual input mode altogether. Too much complexity. One stick has control, the other is blocked, in order to make it clear for the respective pilot, that he has no control.
In case of takeover-button conflict, the captain gets priority.
In case of takeover-button conflict, the captain gets priority.
@WillowRun, even with some heartening views expressed at the symposium there are few indications that the industry is changing, excepting perhaps some aspects of SMS.
The reluctance to change could represent the difficulty in changing culture, which conventionally might take a generation. In that respect 15 yr old thoughts could still be valid, more likely they represent exceptional forward thinking. For more recent views see Cook and Hollnagel, refs.
Ah, Annex 13 ‘Oversight’ – perhaps ‘Overarching Standards and Practices’ is better.
One ‘change’ initiative, amongst others is the awkwardly termed ‘Resilient Engineering’ - to build resilience (and how to spring forward, not back to an original positon).
The fundamental concept seeks a different way of thinking about safety – safety is not something to have, but that which is done. Furthermore, safety thinking should be against the backdrop of what happens in every-day situations – the successes, and most importantly to view humans as an asset, not as a hazard. Also, by comparing ‘work as done’ against ‘work as imagined’, any gaps in safety assumptions could be understood.
With understanding and improving the ‘successes’ there should be less opportunity for the failures. Unfortunately this assumes that the industry does not demand more activity, in more complex operational system, and the need to work near to the edge of established safety boundaries.
Distantly this can reflect the gap between researches seeking to better understand human behaviour (know-what) vs the industry’s need for the ‘know-how’ to enable current academic views to be implemented, an aspect which is reflected in some symposium presentations (inconsistent HF, CRM, TEM, training).
The change of view above is often defined as ‘Safety 2’, unfortunately with the potential for misinterpretation as a replacement for what we do now – Safety 1. I subscribe to the concept of “Safety 1 and Safety 2”. S1 has enabled today’s successes and should not be totally rejected, but in order to progress – high reliability organisation, complex operations, etc, S1 and S2 could provide the means for managing the uncertain nature of modern operations and reducing the potential for major accidents. Additionally, S2 thinking in areas of S1 may add unseen safety advantage, particularly in the ‘safety – commerce’ balance which could be overly subjected to S1 type commercial thinking.
A practical aspect RE starts with Learning, and then cycling though Responding, Monitoring, and Anticipating. The cycle can be entered at any point, i.e. Learn from accidents, Monitor the Responses made based on what has been learnt, which could provide the Anticipation to avoid or minimise the effect of future events, even to the point in not being exposed to situations which could not have been foreseen – we never know - uncertainty.
The points of learning should not require massed evidence or deep understanding; they could be questions about what is done ‘normally’, individually or collectively. Thus relating to this accident ‘what is the normal cruise seat positon’, ‘can full control be achieved from this position’, ‘is the SOP to follow the FD overstated’, ‘how is the FD interpreted’, ‘should we leave our seat to switch systems’, trim, etc.
With answers to these then the responses the required safety activity should be clearer, quicker, and pertinent to operations opposed to time-delaying regulation and training.
Resilience Engineering.
Introduction to S-I and S-II.
Resilience Analysis Grid.
The Resilient Organisation.
From Safety 1 to Safety 2
and for roulishollandais, et al; Non-Newtonian View of Accidents.
The reluctance to change could represent the difficulty in changing culture, which conventionally might take a generation. In that respect 15 yr old thoughts could still be valid, more likely they represent exceptional forward thinking. For more recent views see Cook and Hollnagel, refs.
Ah, Annex 13 ‘Oversight’ – perhaps ‘Overarching Standards and Practices’ is better.
One ‘change’ initiative, amongst others is the awkwardly termed ‘Resilient Engineering’ - to build resilience (and how to spring forward, not back to an original positon).
The fundamental concept seeks a different way of thinking about safety – safety is not something to have, but that which is done. Furthermore, safety thinking should be against the backdrop of what happens in every-day situations – the successes, and most importantly to view humans as an asset, not as a hazard. Also, by comparing ‘work as done’ against ‘work as imagined’, any gaps in safety assumptions could be understood.
With understanding and improving the ‘successes’ there should be less opportunity for the failures. Unfortunately this assumes that the industry does not demand more activity, in more complex operational system, and the need to work near to the edge of established safety boundaries.
Distantly this can reflect the gap between researches seeking to better understand human behaviour (know-what) vs the industry’s need for the ‘know-how’ to enable current academic views to be implemented, an aspect which is reflected in some symposium presentations (inconsistent HF, CRM, TEM, training).
The change of view above is often defined as ‘Safety 2’, unfortunately with the potential for misinterpretation as a replacement for what we do now – Safety 1. I subscribe to the concept of “Safety 1 and Safety 2”. S1 has enabled today’s successes and should not be totally rejected, but in order to progress – high reliability organisation, complex operations, etc, S1 and S2 could provide the means for managing the uncertain nature of modern operations and reducing the potential for major accidents. Additionally, S2 thinking in areas of S1 may add unseen safety advantage, particularly in the ‘safety – commerce’ balance which could be overly subjected to S1 type commercial thinking.
A practical aspect RE starts with Learning, and then cycling though Responding, Monitoring, and Anticipating. The cycle can be entered at any point, i.e. Learn from accidents, Monitor the Responses made based on what has been learnt, which could provide the Anticipation to avoid or minimise the effect of future events, even to the point in not being exposed to situations which could not have been foreseen – we never know - uncertainty.
The points of learning should not require massed evidence or deep understanding; they could be questions about what is done ‘normally’, individually or collectively. Thus relating to this accident ‘what is the normal cruise seat positon’, ‘can full control be achieved from this position’, ‘is the SOP to follow the FD overstated’, ‘how is the FD interpreted’, ‘should we leave our seat to switch systems’, trim, etc.
With answers to these then the responses the required safety activity should be clearer, quicker, and pertinent to operations opposed to time-delaying regulation and training.
Resilience Engineering.
Introduction to S-I and S-II.
Resilience Analysis Grid.
The Resilient Organisation.
From Safety 1 to Safety 2
and for roulishollandais, et al; Non-Newtonian View of Accidents.
Alarming...
Although overspeed is not desirable in a modern transport jet, it is much less harmful than stalling it.
Talk to test pilots and certifying engineers. Modern transport jets are deliberately flown into heavy overspeed situations, and they are just fine compared to being in a fully developed stall with 40° AOA and falling like a stone.
If I could pick 50kt overspeed or 40° AOA I would always choose overspeed.
Talk to test pilots and certifying engineers. Modern transport jets are deliberately flown into heavy overspeed situations, and they are just fine compared to being in a fully developed stall with 40° AOA and falling like a stone.
If I could pick 50kt overspeed or 40° AOA I would always choose overspeed.
In contrast, all Part 25 aircraft have to demonstrate safe stall characteristics, and there's no reason why AoA should develop to 40° unless you hold the aircraft into the stall. Even then it should be recoverable with the published technique for your type.
Let's all be REALLY careful what we post on this professional forum, and REALLY careful what we read and believe. Let's base ourselves on the facts. Seriously.
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Let's all be REALLY careful what we post on this professional [rumor] forum, and REALLY careful what we read and believe.
Better advice of immediate use for those pontificating to those reading would be to be "REALLY careful" when flying with fully aft stick.
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Flying in alternate law
Can someone who actually flies a bus tell me
Are you trained /practiced in flying in alternate law at cruise altitude?
Is there any policy that says pilots should / should not recieve this training?
Why/ Why not ?
Are you trained /practiced in flying in alternate law at cruise altitude?
Is there any policy that says pilots should / should not recieve this training?
Why/ Why not ?
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Overspeed vs Crazy AoA.
Surely there are too many variables to say which is preferable:
how much energy a/c has, are the engines at idle and how long until they can be safely spooled up without providing a pitch moment due to under slung turbines, is pilot 2 whisking mayo, how much altitude above and below, traffic, terrain, wx, aircraft hot high and heavy, are we in a war zone.
Surely there are too many variables to say which is preferable:
how much energy a/c has, are the engines at idle and how long until they can be safely spooled up without providing a pitch moment due to under slung turbines, is pilot 2 whisking mayo, how much altitude above and below, traffic, terrain, wx, aircraft hot high and heavy, are we in a war zone.
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SOLUTION
There are only two realistic solutions to the problems we are having in aviation with perfectly flyable planes crashing and killing the pour souls on board.
1.The PIC must be highly experienced and well-trained in all scenerios.By this I mean at least 7-10000 hours in general, and a comprehensive simulator syllabus.
2.The F/O might be low hours meaning only 200-300, that is okay but must have a significant simulator training syllabus as well, not the cheapskate rubbish now being accepted.
In order for these things to happen a lot of money needs to be allocated.What we have now is just crap.The airlines know it and the regulators are just going along with it, both have a lot blood already on their filthy hands.
1.The PIC must be highly experienced and well-trained in all scenerios.By this I mean at least 7-10000 hours in general, and a comprehensive simulator syllabus.
2.The F/O might be low hours meaning only 200-300, that is okay but must have a significant simulator training syllabus as well, not the cheapskate rubbish now being accepted.
In order for these things to happen a lot of money needs to be allocated.What we have now is just crap.The airlines know it and the regulators are just going along with it, both have a lot blood already on their filthy hands.
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In my opinion the problem is not that mystical or of serious systemic deficiency requiring drastic modifications but of insufficient knowledge of effects of flight controls in alternate law. With all protection removed applying and holding full back stick is very dangerous and totally unwarranted. In alternate law at lower levels even with EGPWS warning you don't do it. If this is done with sufficient speed the aircraft will do a loop. With rate of roll doubling pilots action on roll should be very gentle. At higher cruise levels to do all this is sheer madness. In alternate law you never, ever pull and hold back stick. If this simple thing was instilled during training and flying these accidents would never have happened. Following are my inputs to some of the suggestions by members:
At cruise levels let alone alternate law but it is simply not possible to even fly manually due to RVSM.
Having only experienced PIC is ridiculous because one has to start as inexperienced to get experience.
In AB FBW in direct law computers do not modify pilot inputs, it is a linear direct relationship between stick and elevators. Except max elevator deflection is function of C of G.
About shiny red button, fear of pilots using it is not unreal. If they can reset forbidden CBs then nothing prevents them practicing in direct law by using the button and erroneous activation of a protection can be handled in alternate law. Why is it so difficult to understand that in alternate law you never use the side stick to any extreme, leave alone pulling the stick back and holding it there? which is what started it all.
In Airbus FBW there is only one way to take over controls and that is by pressing the take over button. One needs to develop the habit.
At cruise levels let alone alternate law but it is simply not possible to even fly manually due to RVSM.
Having only experienced PIC is ridiculous because one has to start as inexperienced to get experience.
In AB FBW in direct law computers do not modify pilot inputs, it is a linear direct relationship between stick and elevators. Except max elevator deflection is function of C of G.
About shiny red button, fear of pilots using it is not unreal. If they can reset forbidden CBs then nothing prevents them practicing in direct law by using the button and erroneous activation of a protection can be handled in alternate law. Why is it so difficult to understand that in alternate law you never use the side stick to any extreme, leave alone pulling the stick back and holding it there? which is what started it all.
In Airbus FBW there is only one way to take over controls and that is by pressing the take over button. One needs to develop the habit.
Last edited by vilas; 16th Dec 2015 at 09:03.
phylosocopter #3818, an interesting thought, where it would be logical to assume that pilots would have some exposure to alternate law. Yet the law is only an ‘alternate’ and does not, as AFAIU, pose any great difficulty in control; more so with protections in place.
A different question could ask if crews have been exposed to the situations where their apparent inability to fly in alternate law was noticed, but these are very rare and often unforeseeable. Why attempt to train every 1 in 10-9 event, which represents impossible reactive safety, we never catch up. Why not ‘ask’ (determine) how many pilots inappropriately (foreseeably) pull CBs in flight.
A different approach is to consider the problem at a higher level. The informative presentation Managing Startle gives some well-constructed views of the human issues, but even then solutions to the ‘how to’ problems of imparting and refreshing knowledge, teaching and practicing SA, and need to plan ahead, are not outlined.
The underlying problem appears in both teaching relevant knowledge – ‘know what’ (but who decides on what is relevant), and the much more difficult acquisition of ‘know-how’ skills, when and where to use the knowledge.
From a previous post, you can provide knowledge of how to ride a bike, but you have to do ‘it’ to be skilful. What is the ‘it’ in flying (not the hands on bit) that is so elusive, perhaps we have to get on our metaphorical bikes to find out.
A different question could ask if crews have been exposed to the situations where their apparent inability to fly in alternate law was noticed, but these are very rare and often unforeseeable. Why attempt to train every 1 in 10-9 event, which represents impossible reactive safety, we never catch up. Why not ‘ask’ (determine) how many pilots inappropriately (foreseeably) pull CBs in flight.
A different approach is to consider the problem at a higher level. The informative presentation Managing Startle gives some well-constructed views of the human issues, but even then solutions to the ‘how to’ problems of imparting and refreshing knowledge, teaching and practicing SA, and need to plan ahead, are not outlined.
The underlying problem appears in both teaching relevant knowledge – ‘know what’ (but who decides on what is relevant), and the much more difficult acquisition of ‘know-how’ skills, when and where to use the knowledge.
From a previous post, you can provide knowledge of how to ride a bike, but you have to do ‘it’ to be skilful. What is the ‘it’ in flying (not the hands on bit) that is so elusive, perhaps we have to get on our metaphorical bikes to find out.
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Originally Posted by vilas
In alternate law at lower levels even with EGPWS warning you don't do it.
Apply full back stick, just don't hold it when approaching the stall speed or buffet is coming.
In alternate law you never, ever pull and hold back stick.
...
Why is it so difficult to understand that in alternate law you never use the side stick to any extreme, leave alone pulling the stick back and holding it there?
...
Why is it so difficult to understand that in alternate law you never use the side stick to any extreme, leave alone pulling the stick back and holding it there?
Or are they too many laws in the Airbus world ... ?
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CONF iture
You don't apply full back stick in alternate law but steadily pull up to stall warning, by stalling you won't avoid ground contact. In alternate law You pull full back stick if you want to do a loop which in absence of pitch attitude protection is possible. I have made points very clear and you haven't added anything. In any case your opinions about airbus are more visceral than technical. You seem to be supporting the unnecessary rapid full pitch inputs in these accidents and suggesting revolutionary changes in aircraft design which are not going to happen.
You don't apply full back stick in alternate law but steadily pull up to stall warning, by stalling you won't avoid ground contact. In alternate law You pull full back stick if you want to do a loop which in absence of pitch attitude protection is possible. I have made points very clear and you haven't added anything. In any case your opinions about airbus are more visceral than technical. You seem to be supporting the unnecessary rapid full pitch inputs in these accidents and suggesting revolutionary changes in aircraft design which are not going to happen.
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As I'm sure the poster of the above knows, Part 25 certificated aircraft are tested for structural behaviour (flutter) up to VD/MD, but not above. Above VD/MD all bets are off and the designer has no more data for you. Flutter can develop in seconds and can be catastrophic in only a few more. To take the A320 as an example, MD is approximately MMO+20 knots at FL390. If you allow your aircraft a '50 knot overspeed', then you are not only conducting experimental flight test, you're doing a research programme that's unlikely to end well.
VD/MD of the A320 is 381kt / M0.89. As we usually don't fly over 340kt / M0.80, and we were talking the high level case, '50kt overspeed' is a rough ballpark just to show that you can go very far on this side of the performance.
In reality you will have an extremely hard time to bring your aircraft to such an overspeed in high level. It needs considerable pitch down plus engines at full steam to accelerate that fast (if I remember correctly we talk about a pitch down of 7.5° compared to the pitch before plus full thrust but certification pilots will sure correct me on that).
If you cruise happily along with AP/FD/ATHR on and suddenly the alarm bells go on or your plane is throwing ECAM failures at you, there is ZERO need to be ****-scared about overspeed. If you are overspeed, it won't be in any lethal way, just gently fly your plane out of it. No need to pull the stick fully backwards.
In such a situation, while you pull GENTLY out of the overspeed, AOA should be your concern, because it doesn't take a lot of degree pitch up to stall at such levels.
Once you are in the fully developed stall (high AOA due to low forward speed due to huge drag due high pitch), it takes a lot of pitch down to make your wing fly again (you basically have to pitch down nearly to your flight path vector), then a lot of time to accelerate again to a speed that supports level flight, and again a lot of time to gently change your flight path from rapid dive to level flight. I don't want to image how many thousands of feet that takes.
Last edited by 1201alarm; 16th Dec 2015 at 21:31.
@ conf and vila
If the DIRECT law has a completely linear plot from zero stick/elevator to full deflection, then how does cee gee come into play? Show me the plot of deflection/stick pressure versus control deflection. 45 degree line? Is a degree of stick equal to a degree of elevator movement? Maybe it's 1:2 or 2:1 or whatever.
I have to agree that full stick deflections are not always the way to go even in NORMAL laws. I also point out that the two 'bus crashes we have dissected appear to indicate very little buffet or shaking or such that many of us here were used to in other jets.
TNX 1201, you sound like the crowd that thinks "don't just do something, sit there"
If the DIRECT law has a completely linear plot from zero stick/elevator to full deflection, then how does cee gee come into play? Show me the plot of deflection/stick pressure versus control deflection. 45 degree line? Is a degree of stick equal to a degree of elevator movement? Maybe it's 1:2 or 2:1 or whatever.
I have to agree that full stick deflections are not always the way to go even in NORMAL laws. I also point out that the two 'bus crashes we have dissected appear to indicate very little buffet or shaking or such that many of us here were used to in other jets.
TNX 1201, you sound like the crowd that thinks "don't just do something, sit there"
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Hey Gums, see the graph in reference below at page 112.
http://www.bea.aero/docspa/2008/d-la...a081127.en.pdf
At the bottom of page, the flight law switched from normal to direct = "intuitively" alternate law + landing gear extended, between 15:45:15 to 15:45:40. See the purple and green curves are proportional, however the elevator is at 75% (12.5 deg out of of 17 deg) for stick at full ND.
Note: Interesting for pitch in alternate law, the stick to elevator relationship, is opposite ?!
As per FCOM, the pitch in direct law is a direct stick-to-elevator relationship (elevator deflection is proportional to stick deflection). However, maximum elevator deflection varies as a function of CG. No protections are available.
http://www.bea.aero/docspa/2008/d-la...a081127.en.pdf
At the bottom of page, the flight law switched from normal to direct = "intuitively" alternate law + landing gear extended, between 15:45:15 to 15:45:40. See the purple and green curves are proportional, however the elevator is at 75% (12.5 deg out of of 17 deg) for stick at full ND.
Note: Interesting for pitch in alternate law, the stick to elevator relationship, is opposite ?!
As per FCOM, the pitch in direct law is a direct stick-to-elevator relationship (elevator deflection is proportional to stick deflection). However, maximum elevator deflection varies as a function of CG. No protections are available.
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Originally Posted by vilas
You don't apply full back stick in alternate law but steadily pull up to stall warning
As instructor you pretend to be, that you disseminate false information is a bit disturbing.
Originally Posted by gums
I have to agree that full stick deflections are not always the way to go even in NORMAL laws.
And of course Direct law is something else totally ...
I know ... many laws !
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Re decoupled sidesticks and possible involvement on AF447 and AirAsia, it was already mentioned in this thread the new G500 and G600 will have "active sidesticks" which are electronically coupled.
I just saw this brief video that explains it:
https://www.youtube.com/watch?v=vXhCJYWvwd0
The system is made by BAE. I wonder what the cost/risk/complexity would be to retrofit this to an Airbus?
Commercial Active Sticks - An Active Role | BAE Systems | United States
However this FlightGlobal article says BAE has no plans to offer it as a retrofit option:
https://www.flightglobal.com/news/ar...-aircr-411455/
I just saw this brief video that explains it:
https://www.youtube.com/watch?v=vXhCJYWvwd0
The system is made by BAE. I wonder what the cost/risk/complexity would be to retrofit this to an Airbus?
Commercial Active Sticks - An Active Role | BAE Systems | United States
However this FlightGlobal article says BAE has no plans to offer it as a retrofit option:
https://www.flightglobal.com/news/ar...-aircr-411455/
1201,
Thanks for that clarification. I certainly agree with you that a heavy pull on the stick at high altitude to avoid an overspeed is inadvisable. But let's not underplay the risks of exceeding VD/MD. And I'm talking about a real overspeed here, not a falsely indicated one in the unreliable airspeed case.
The Part 25 VD/MD tests require the dive to be held for 20 seconds, which isn't that long really, and at less than full power. The testing is one aspect of determining VD/MD, but be clear that the aircraft won't have been flown above that speed.
The extreme AoAs reached in the Air Asia and AF cases were the result of pulling and holding the aircraft into the stall. A correct recovery flown at the point of stall warning, or even at the stall itself, will not lead to such AoA, or to huge altitude losses.
What I'm saying is that the stall case is recoverable, but that the result of flutter probably won't be.
You're not Buzz Aldrin, by any chance?!
Thanks for that clarification. I certainly agree with you that a heavy pull on the stick at high altitude to avoid an overspeed is inadvisable. But let's not underplay the risks of exceeding VD/MD. And I'm talking about a real overspeed here, not a falsely indicated one in the unreliable airspeed case.
The Part 25 VD/MD tests require the dive to be held for 20 seconds, which isn't that long really, and at less than full power. The testing is one aspect of determining VD/MD, but be clear that the aircraft won't have been flown above that speed.
The extreme AoAs reached in the Air Asia and AF cases were the result of pulling and holding the aircraft into the stall. A correct recovery flown at the point of stall warning, or even at the stall itself, will not lead to such AoA, or to huge altitude losses.
What I'm saying is that the stall case is recoverable, but that the result of flutter probably won't be.
You're not Buzz Aldrin, by any chance?!