DW
 

Hi DW, being evasive?

I described a flight phase as opposite to another flight phase (like one being close to the ground) where autotrim could help in Alt2 even at the extremes of the flight envelope (i´m not saying it would). My above statement stays. Should have explained to you, looks like.


Is it of relevance to this discussion? You may accept, that I look at it from an operators point of view. If the system is able to prevent trimming into a stall in ALT1 and Direct Law, it should be able to design one, that can do the same in ALT2.

But you did not answer my question.


You don´t need to explain how it is done, the technical aspect does not matter to the operator. Graceful would be logical, but this degradation is not.

is exactly my point. Let Pete know, that autotrimming into a stall is no good idea, like Pete knows in Alt1 at Vprot and in direct law. Implement it, however you do it.

The original sense of trim is to aleviate loads on the system after a flightpath change / change of loadfactor has been achieved (long term).

FCPC will always try to hold a load factor demand, by using elevators in short term and autotrim in longterm. How to disable the elevators during manual trim? With SS, I know, but if properly used manual trim would not have been necessary in the first place.
But if the system would have reverted to manual trim like in ALT2 at Vprot or like in Direct LAW, THS would not have been trimmed Full NU by the FCPC via SS inputs.

You know very well that i´m fully aware about the functioning and the necessity of autotrim and do not question it. I even find it a clever and well thought out system. But the situation developing in ALT2 with AF447 was not being expected somehow and needs to be addressed and changed. It works in Alt1 at Vprot, why not do the same in Alt2? Nobody seems to be concerned to hinder autotrim in Direct Law, but you explain it would be difficult for the crew if autotrim would be hindered in Alt2 when predesigned values (aoa, speed, Trim value, take whatever would suit yourself) are reached?

You are going flying? Pull on the stick and start trimming while pulling (hope you have your chute with you. No need to use a Ouija board.

Overall design has to follow function, not vice versa.

Yep. Yokes may or may not be better, but they provably do not cure the problem.

That report was also referred to way back in this thread: http://www.pprune.org/tech-log/17316...ver-stall.html

Post #18 (from Old Smokey) on that thread is particularly precient regarding the stall training issue. Since then, Colgan, Perpignan, Schipol, 447 etc. and finally in 2011 maybe something is getting done about stall training.

Some other bits from the report:

So that was 1996, and 1997, and now in 2011:

Is the industry going to lear from history or repeat it...

Dropping autotrim in direct law already possibly killed several at perpignan, and similar change (although different system) probably contributed at schipol. I wouldn't say there is no concern about it.

The big problem with what you suggest is that the plane is in Alt22 because it doesn't have trustworthy values for speed, aoa and possibly other airdata. So what should it stop trimming based on ?

The whole reason the protections drop out is because it has been held to be more dangerous to "protect" based on invalid (or not trusted) data, than to hand full unprotected control to the pilot. I suspect this is a certification issue. Boeing FBW is exactly the same (not sure about the newer bizjets).

That whole assumption may need to be challenged now - possibly we're reaching the point where safety will be improved by systems overriding / protecting pilots even based on known-bad airdata. Be careful what you wish for...

Wrong - in fact opposite.

Stall warning shouldn't happen if everything is working, but in fact can and does happen in normal law. If it does, at least in some (possibly all) cases it is a signal to the systems that something is wrong (maybe airdata), and normal law will then drop out.

So, SW more or less inhibits normal law, not the other way round.

I'm disappointed that no one commented on this comment! Goes back to the earlier link posted relative to the pull reflex.
When the wings rock, you have to reduce AOA if you want to be in charge of a flying machine. Otherwise, you are just a passenger.
I thought all real pilots knew that instinctively.:rolleyes:

Thrustworthy values
 

Exactly on that, not having thrustworthy values.
With thrustworthy values the protections would stop the trim reaching special values , without those values it will continue to trim also it can cause harm.

Where is the logic?

Infrequentflyer789

Yes, SW inhibits Normal Law, then. Do you have a thought as to the relevance of degrade at the Initial SW just after handoff? Are you convinced the ADRdoubled out and that was the immediate cause of ALT2? The SW had no effect? Any chance that the SW chirped and was silenced as in Protection? Which? If any?

Logic is that when computer is half-blind and/or confused, it will hand over the responsiblity for staying inside flight envelope to the usually superior analysis and decision making skills of the real pilots.

It cannot logically limit trim to "safe" values if it no longer knows what those values are.

Autotrim didn't down this a/c - it was stalled by elevator alone and elevators were held nose-up all the way down. There was no diagnosis of stall let alone recovery attempt.

In contrast, the cessation of autotrim when things start to go wrong is a least a contributory factor in some crashes, if not a killer.

@Franzl

Autotrim is a separate system from the protections and the autoflight, as such under manual control and without protections it does exactly what the pilot commands. It does exactly what it says on the tin and trims automatically in the same way that manual trim is applied on older aircraft - there have never been any hard limits on manual trim wheels, why should there be one on their modern automatic descendents?

In this case we have one incident where possibly as a result of panic or poor training the PF commanded the autotrim - *after* the aircraft had already stalled - into an inappropriate position. I can say with some confidence that had the PF realised what was happening and pushed forward for an equivalent time to the amount he had previously been pulling back, the trim would have righted and control would have been regained. One incident in however many tens or hundreds of thousands of flights that this type and it's sister ships have made safely and without incident every day.

As such, it's far more realistic to train pilots to understand what the autotrim does as part of their type conversion (over and above never making and holding large control inputs for more than a second or two) than it is to redesign a system that works as well, if not better that it's manual predecessors and end up sacrificing pilot authority in the process.

@infrequentflyer789 - While you are correct in asserting that one should not hear the Stall Warning in Normal Law, and as such hearing it is an indication that something has gone wrong - as I understand it, the warning and annunciator system is not directly connected to the flight control logic - so it is never switched off or suppressed by anything directly. The FCU is a network of loosely-coupled, real-time processes with a degree of redundancy built in - not a monolithic, closely-coupled design.

Hi DozyWannabe,
FCOM: DSC Aircraft Systems, 27, 20, Alternate Law:
"In addition, audio stall warnings (crickets + “STALL” synthetic voice message) is activated at an appropriate margin from the stall condition."

This seems to suggest that the "Stall" warning is only activated when Normal Law is no longer active.

Stall warning is also active in normal law. The threshold for activation is at 23 degrees AoA, which is far beyond what should ever be experienced in normal law.

I always read "activate" as "will sound" in that sentence as opposed to "becomes available". Would be nice to get some confirmation.

DW
 

Autotrim is commanded by the FCPC´s, not by the pilot. The pilot is ordering a loadfctor and the FCPC commands the elevators (short term) and THS trim (long term) to achieve and to maintain this loadfactor.
That is quite a difference to your saying and to older conventional aircraft. The FCPC will trim the THS all the way nose up with the stick untouched, if in 1 g flight (like in a climb) the speed decays. We discussed that before more then once.

And it is an operating difference as well. Trimming by turning a wheel is a deliberate act to trim, whereas automatic trim by the FCPC is a programmed syytem behaviour. Wether that is a seperate system or an incorporated one is of no relevance at all. Therefore there can be measures incorporated to prevent the trim reaching values, which are insane in FL350. There are enough data available after a pitot failure (altitude, attitude, AOA, GPS data, you name some more) to compute a normal trim zone (with trimming by the FCPC) and one where the pilot should decide wether he really wants the trim that far up by turning the wheel.

I remeber only those, where the trim beforehand wound all the way NU and ceased in the full NU position. If you refer to those, then it would have been better beforehand that the trim stayed in normal trim region.

If ceasing of trimming action in ALT1 is not a bad thing, i cannot follow the argument, why it would be bad in ALT 2.

What trim values are reached in normal operation except takeoff and landing?
Is Full NU a player above FL100 in any kind of normal maneuvering? In which one?

Yeah, I know. I simplified a bit. SW doesn't directly inhibit anything, but once stalled it is likely that airdata discrepancies will start to show up due to the stall, and trip the plane out of normal law. That's assuming the SW is valid.

It's probably possible to take a broken bus and fly to SW in normal law and then recover without leaving normal law. Not sure I'd want to be in the back when someone tried it though. The guys at Perpignan were in direct law within 10secs of SW - see p112 (english version) of final report.

@rudderrudderrat:
See the traces on page 112 of the Perpignan report - SW clearly in normal law.

@Franzl

You're comparing apples with oranges here, or to be more literal, comparing the conventional, or "way we used to do it" method with the method on the FBW Airbus series, which is intended to be used in a completely different way - unless something has gone so seriously wrong with the aircraft that a drop to Direct Law is necesssary.

The FCPCs may command the physical movements, but it is the pilot that commands the FCPCs in manual flight. As the speed decays under Normal Law, the elevator/trim effect is limited by the AoA protections. Under all load factor laws (i.e everything above Direct) - even without protections, as the speed decays the control mode gradually transfers from "G" command to pitch command, meaning that the autotrim will not trim to stall with stick neutral due to decaying speed alone.

In this case the autotrim was commanded to move as it did to support the demands on the elevators made by the PF, who was - possibly for reasons we will never know - holding the thing between 50-100% back for the majority of the accident sequence. It was for this reason as well that the speed decayed, so in effect both the pitch and airspeed factors of the extreme angle of attack leading to and during the stall sequence were because of the consistent back-pressure on the stick, and for no other reason that I can see.

Yes, but it didn't, because (in the cases that come to mind) something else was broken.

It would have been better if the broken thing wasn't broken, but it was. Thereafter the loss of autotrim, coupled with lack of crew re-trim, caused deaths. Having got to that situation, it would have been better if autotrim had stayed engaged so that the trim did not impede the recovery.

In Alt1 there is data available (known-good) that is not available in Alt2. Acting on known-good data is not a bad thing. Acting on known-bad data is.

As to what trim values are normally used, I don't know - but I doubt the designers put the mechanical end-stops where they are without reason. If no more than, say, 9deg nose up was ever needed, then the stop would have been at 9deg not 13.

Airbus went to great lengths to design their FBW system to fly like a normal airplane. But in reality, the FBW Bus's do NOT FLY LIKE NORMAL AIRCRAFT. Auto trim proves that point. The Bus trims for "G", and normal aircraft trim for speed.

Airbus, EASA, FAA, etc, could fix all our problems with flying these computer games with one simple directive; change the training syllabus to state the opposite of what it states at present. Change "it fly's like any other airplane", to " it fly's like NO other airplane"........and train accordingly. Every Airbus pilot should be exposed to degraded flight characteristics at every training event, in addition to all other required maneuvers.

Not sure your're right there. Perpignan traces show exactly what you say can't happen.

I think you'll find that as speed decays, more elevator / trim will be needed to maintain stable attitude, and autotrim will happily provide it - up to the stops.

Sequence I see in traces is:

UAS -> A/P drop & Alt law -> stick-back -> elevator up -> acceleration up -> AOA up -> SW

Causality is not in doubt.

@if789

Wasn't the pitot-static system effectively completely hosed in the Perpignan case though (the systems must have been very badly compromised)? I must confess I didn't have an opportunity to follow that one closely at the time.

To summarize Perpignan:
Perpignan accident was enabled when two AOA sensors froze at a low angle of attack while at altitude due to water intrusion. Crew later attempted to demonstrate activation of Alpha protect as part of a functional check flight of the aircraft and went well past into a full stall, autotrimming nearly full nose up in the process. Aircraft dropped into Direct Law (no autotrim) and crew was too busy to notice. High power setting plus nearly full nose up trim caused the nose to rise uncontrollably until stall. Did not pull out from the resulting nose down attitude.

The hated and feared autotrim, or not
 

Have been on the sideline too long watching defense of a poor control law reversion sequence versus a defense of a poor crew.

Gums' view is there is a lotta blame to spread about.

Take the auto trim, and I do not like that term.....

- When normally flying the jet, HAL tries to reduce required stick displacement from neutral in order to achieve 1 gee that is corrected for pitch. So at 30 degrees pitch, the thing tries to achieve 0.87 gee with hands-off the stick. If I don't read that part of the manual correctly, lemme know.

- If the pilot is commanding more than one gee ( corrected for pitch), then HAL trims the THS to reduce the required stick displacement, or am I wrong on that as well? I see no AoA command when looking at the manuals, but I see some "protections" and warnings that hinge upon AoA.

- If I am at a 15 degree pitch attitude and let go of the stick, then what does HAL do to maintain 0.96 gee as my speed decreases? Does HAL trim the THS for more nose up?

- Then there's AoA sensors that are ignored because the speed is below 60 knots. So how is the stall warning considered valid when the AoA was being ignored? What the hell are you going to use if airspeed indications are unreliable? Maybe replace all the stuff on the LCD screen with a crosshair and dot, then tell the crew to "center the do"t, huh? BEAM ME UP!


Deeply stalled, deep stall, just plain stalled..............

In a plane with a super wing design and great directional stability, then it is easy to be stalled and not spin or have severe wing rock. Buffet could be very low and/or masked by the local weather conditions.

I do not defend the AF crew for the continuous nose up commands, but I can understand the confusion once the jet was "deeply" stalled and various warnings were being presented.

The facts now present clear proof that one can stall the 'bus without going into a spin or having severe wing rock or buffet. Anyone disagree?

The facts do not show that a recovery from the flight condition I just mentioned is impossible, especially with a fully trimmed THS.

Show us the pitch moment versus AoA/CG graph.


I only joined this discussion because I had FBW experience way before the 'bus and was interested in the plane. I also thot I could add perspective from lessons-learned 15 years before the A320 flew.

If I am off base here, or considered a dinosaur that still insists upon mechanical feedback to my stick or wheel or yoke, then tell me to stay quiet.

gums. fwiw, I think you are in the money. As one of a rare few who continue to focus on the cause, rather than the effect, I for one appreciate the lead up to STALL that you discuss. For good or ill, and regardless of 'Blame', this a/c STALLED first, then it died. I like your basics approach, and 'ancient' pov.

if789. At what AoA did the first STALL WARN activate? To me, it seems a bit notable that at cruise, the STALL WARN activates. Since it occurs in such proximity to the a/p loss, my question would be what prompted the autoflight to approach Vs? Was it legit? Had the speeds gone south and the WARN was bogus? Was the vane compromised at this point? Thanks.

Affirmative on the stability part. As for buffet, there might have been some:

@DW
 

Read my posts, and read yours. I did not start comparing, that has been yourself.

I might not know the design of the system, but i can get a grasp on how it functions looking from the pilots side. And from that point of view i find the necessity to stop trimming beyond a certain value, if protections are not available. As mentioned before, there are a lot of data available which could be used for such an safety feature.

That is exactly what happens, and i cannot understand, how anybody can feel good about it. We have been through this ordeal moons ago, but DW likes to forget about that.

Surely these guys "got off the wheel" before it had a chance to turn full circle.

The Stall Warning is just that, and if it was to serve its designed for purpose, the PF/PNF would be expected to acknowledge it and take appropriate action. They didn't, and the wheel turned and got them in the a*se. So in that respect you can't blame the SW.

The PF not understanding that the pitch operates the same way in Normal Law and Alternate Law, but one "is protected" and the other is "not protected" is also a mystery. The PNF more worried about getting the CPT back to the FD than calling the ECAM and getting the QRH out is an even stranger mystery. This accident didn't happen in a vacuum - it happened to a flight that was under the control of two "apparently" competent pilots.

Granted there are issues that have validly been raised in respect of the SS visibility, but they are secondary to the human factor failures that we are currently aware of.
The aircraft did as it was told - abeit the "wrong" thing, but it can't be "strung up" for that, with one proviso - there needs to be a means of preventing THS auto trim runaway once CAS/AoA/FPA have gone AWOL.

Lets face it, the pilots had control and the aircraft knew no better than to obey them.

Control
 

To have control there has to be an understanding how things (trim, stall warning, LAW, aerodynamics) work.
Lets face the fact, that this knowledge probably was not present with the crew of AF447. And unfortunately the discussions in this and the former threads show, that it is not a single case problem.

There! You have effectively answered yourself; autotrim is good thing as long as one know how it works, applicable to any aeroplane system and one is required to know that by air law and the basic DNA-ingrained law of self preservation. With AF447 crew it was not just that they forgot about autotrim - they never verbalized what in the hell they thought was going on and what they thought they should do, indicating the rabbit-in-the-headlights defence posture. In the end, what CM2 did with the stick is what killed them. So far, investigators have published nothing that would indicate THS would not go nose down if only stick(s) were pushed forward.

I have to make very long&imprecise shot here: I suppose that in former life you were jealous of Bitburg based Ego drivers, with right hand gloves that didn't show wear at thumb.

Translation: F-15 has autotrim. How can anybody fell good about it? Very easily, I'd say.

So far, no official word has been provided on the matter. No certification authority concern. No accident investigation opinion. I do not consider mutual congratulations of anonymous posters, praising each other on understanding how Airbus is dangerous to be reliable.

clandestino
 

Hi Clandestino,

I have a chuckle on this one, like it actually. I still have some left hand gloves in good shape and missing the right ones with holes in the thumb.
I was flying in the backseat of an F15 double seater 1990 in a low level mission, and didn´t even recognize its autotrimming.

But to make my position clear: I stated several times and do it again here, i have nothing at all against a fine autotrim system. So its a bit unfair of you to put blame on me for not recognizing the advantages of FBW and its asociated systems.

I agree with that, never did otherwise, and i knew somebody would jump on it. My concern is not about blame (neither to the pilots nor to the airframe), but about prevention. This trimsystem can be improved in the mentioned area without decreasing its overall performance, thus eliminating one hole in the different layers of cheese.

Why not talk about it and why not work on a change? Is it pride or neglicence, costs or arrogance which keeps us from recognizing, that there was a crew who was obviously not familiar with the behaviour of the aircraft despite their training, their hours of experience and their legal licences? Im pretty sure, there are others out there who learned a lot out of this accident and try to improve their knowledge base, but others will not and will never and might fall to the same situation.

Why not improve the autotrim system? There are accidents (not this one alone) where a correct functioning autotrim, not understood by the crew, contributed to the outcome of the happening. That should tell us not only that knowledge and training has to be improved, but that we also should improve the system to prevent that such misinterpretations proliferate into full accidents.

The statement, that they shouldn´t have got in this situation beforehand is correct, but it is not the way to look at the things in accident investigation and accident prevention and in view of flight safety. The task is not to close the hole in the first layer of cheese, but to take care of all known holes.

Not expressing disagreement with your suggestion that this aspect merits revisiting, but could you please explain the implication that it contributed to 'this one'.

Hazelnuts39
 

I might try.

At 02:10:51 the stall warning sounded. AOA was 6°, pitch was 10°, elevators about 5° noseup, THS at -3° NU. At that point the stab trim starts taking over the load of the elevators and the THS trim starts to move uninterrupted to full NU position within the next minute. During this time period the SS was in the average NU, but never full NU (max NU was 13°, 5 times it was up to 8° ND. Note, that the elevators stayed at max 10° NU until 02:11:35: Then they moved further down and reached their 30° NU at 02:11:45 and about the same time the THS reached the full NU limit. (see the FDR in the BEA interim 3 report).

Would this THS trimming had been prevented upon the sounding of the stall warning, the elevators alone would have imho not been sufficient to keep the nose up in the stall over the following period. This THS is a mightiy thing and gave the crew the tool, to transfer their unfortunate SS commands into some kind of establishing the aircraft deep into the stall region.

The nose woud have dropped early in the stall, maybe the AOA would have been considerably lower and thus permanent stall warning available, the speed drop would have been less and all this could have finally helped in an recovery (which unfortunately was even not attempted).

I´m not saying, that this would have prevented the outcome at all, but it might in another situation on another day with a different crew.

There is a bottom line in that conjecture, one I posted a very long time ago. It hasn't to do with competence of pilotage, but with common sense from the supposed brilliance of the design. "Just like a "Conventional" Aircraft", is buspeak for "Let's throw a bone." Arrogant.

Had the a/c STALLED earlier, without the authority of that monster slab, there would have been a great deal more energy retained, and the Nose would have fallen dramatically, imo.

Instead of MUSH, the pilots would have had at least one emphatic cue. Wait, let's make that two, with proper Buffet. Whether at that point the flight recovers is moot.

But it's worth an honest discussion.

RetiredF4;

Thanks for your elaborate explanation, with which I partially agree, but not quite. The airplane stalled a few seconds before 02:11:00, when the THS had hardly moved. The longitudinal control law imposes a certain pitch rate in response to the SS demands. If the THS had not moved, that pitch rate would have required a larger deflection of the elevator, but the pitch rate and hence AoA achieved would not have been significantly different, until the elevator reaches its stop. As to the THS being 'a mighty thing', that is true, but should not be exaggerated. According to Owain G's post, 10 deg of THS is equivalent to 15 deg of elevator. Therefore I agree that the effect of less THS as the airplane got deeper into the stall would have been somewhat lower AoA's, but that's about it.

Retired F4, I did not mean to infer that we shouldn't be discussing the Airbus flight controls in general or autotrim in particular; quite the opposite - it absolutely needs to be discussed to gain understanding. Given your experience and information you posses, your points are very valid and true. However, methinks that your perspective is somewhat lacking breadth. It is indeed true that having autotrim stop at stall warning would make AF447 behave differently - whether it would significantly affect the outcome is open to conjecture. Problem is we don't have infinite amount of cheese to patch up all holes. Patching up one, more often than not opens other holes. As DP Davies has beautifully demonstrated when analyzing pushers, every safety system is potential killer and risks an benefits have to be weighed carefully, especially cases of "operating when not needed" vs. "failing to operate when required". Before AF 447 there was nothing to suggest that autotrim concept as applied to FBW Airbi is flawed and I guess that even after final report is out it won't change.

It actually is but is not be-all and end-all. Obedient trim has good chances to be listed as one of fifity-something or more contributing factors but we shouldn't concentrate solely or it or ignore it completely. Balance has to be struck somewhere, not necessarily in the middle. As I see it, it was just a footnote in the history of certain crew that became (in)famous through spectacular error.

The biggest problem I see in discussions regarding the unwholesome fate of AF447 is that we are faced with horrible picture of three pilots who forgot how to fly in the midair so we are amusing ourselves with tiny technical details just to avoid to step back and face the sheer ugliness of the event.

Did I just blame the deceases pilots for the calamity? On purely technical grounds: no! I don't care a little bit about earthly theories of fault and blame but I do want that whatever daemon of the air got our unlucky colleagues gets caught and dissected and we won't be able to catch it if we put our traps in the places it doesn't visit.

It's not technical, it's in our heads.

Clandestino
I don't know much time you have in tactical jets, but you have enough chutzpah to have come to aviation that way. This is not a criticism by the way.

The performance of the autotrim system in this corner of the flight envelope likely does not meet certification requirements. Certifying this feature in Alt 2 at the stall was probably not envisioned in the initial requirements due to the high anticipated reliability of the airspeed system. It fell under the category of too improbable to worry about. Today we know that line pilots actually bumped into this corner of the envelope.

Despite Owain's assertions about relative power of the elevator versus HS (and I believe he is quite competent in this field) he was not working with the best data and his results may be slightly skewed.

Consider the Perpignan A320 and how throughly the THS overruled the elevator. Different aircraft, but designed by the same team with similar design philosophy.
Yes it is possible to stall the Bus in ALT2 using just elevator and thrust as we saw demonstrated by AF447, but who can say, had the trim had been limited, whether or not the crew would have seen the airspeed come off the peg a bit during one of their nose down trials and continued their nose down efforts.

THS running full nose up is a potential serious hazard and needs to be guarded against better. How to do that is one for the engineers (design type not wrench type) to puzzle out, but judging from what has recently transpired with the type, it may save two or more aircraft in the future. Expecting training to handle the problem completely is not realistic. If we see nothing in BEA's final accident report addressing this problem, then you should be concerned.

SS inoperative
 

When reviewing the FDR traces for my last contribution i stumbled on the the bottom lines on page 108 of BEA interim report N. 3.

At about 02:11:40 their is a spike indicating FO SS inoperative and a longer one shortly thereafter with Captain SS inoperative. It happens the same time, the THS and elevators reached Full Nose up. At the end the same indication Capt. SS inoperatie shows up again.

WHat would have caused this indication? Has it something to do with the priority button?

Machinbird, in re training:
The THS can be limited in movement by using the hand wheel in the cockpit. If it goes up too far it can be moved back down to where the pilots want it, since it appears that hands on the wheel overrides anything HAL tells it to do ... at least while the hand is on the wheel. ;)

Some threads ago, one of our Airbus 330 experienced pilots indicated that touching of the trim wheel in some sim training sessions was incentivized against. (Training note: This looks to fall into the realm of something called negative training, as in not correctly incentivizing a proper course of action, or incentiving against a given course of action).

Yet another Airbus 330 experienced poster here, Mikelour IIRC, described some unusual attitude training he encountered where using the trim wheel was one of the best ways to deal with it, though some crews had to be coaxed into using that resource, see above for possible reasons for that.

There seems to be some professional disagreement within the AB community, and the people who train the crews for various companies, on what is and isn't appropriate use of the trim wheels.

I don't think that changes the response to your concern:

if THS runs amok, you can manage it with your hand. What seems to add joy to this drill is the fact that when you aren't moving the wheel, depending on what HAL has in mind, HAL may move THS on his own cognizance once you reposition it. This point was also made by some of our Airbus veterans.

Good fun, and no sitting on your hands in an Airbus cockpit! :ok:

Actually it is zero and I got into professional aviation through kind of integrated course. I'm an aviation buff that got very, very lucky to have both pictures taken by me and pictures of me posted on !!!!!!!!!!!!!!. Don't concentrate on who is behind the nick but rather on what is written in the post.

Given your previous post, I think you might be mistaking the description of flight test method with certification requirement.

It did not run away, it was commanded to trim by FC computers.

Or kill two or three in the process if all implications of having such a system don't get well thought out and crew gets caught out by losing autotrim when they don't expect it.

Neutral is 1G demand, full in clean is 2.5G demand. assuming linear sidestick response (I don't know whether it's precisely linear but during my time on bus it sure felt like it), half stick would be 1.75 G demand - impossible to meet below 1.38 Vs so with all air data rejected as unreliable and inertial reference available, both elevators and trim would try to meet it no matter what. That's why they ran to their limits.

Except "don't do that", I can't find official reference what would happen if you try it. When we tried it out on the 320 sim, it simply ran to position demanded by FCCs when released.

There is another method of stopping the nose-up trim: push the stick forward.

Yes. FO SS inop means capt's priority button pressed and held an v.v. There's also latch out if priority button is held long enough but given the traces, it wasn't the case here.

read what the guy (Machinbird) said - who said 'away'?? It is "running full nose up is a potential serious hazard" that is the problem.

By the time it got to stop, aeroplane was truly stalled and flight controls were trying to satisfy 2.5G demand which, as we all should know, is impossible to achieve below 1.58 Vs. Demand was given using RH sidestick. Do you dispute that or rather you believe that actual problem is dumb computer obeying supposedly intelligent human which got confused? Do you really want more intelligent computers recognizing when thinking in cockpit has stopped and taking over? IIRC one of the main complaints on PPRuNe was: Airbus computer doesn't let me to do what I want, sob, sob.

Well, on AF447 computers got confused by losing all three speed references so "decided" not to interfere with pilot's demands. That's what is meant by very technical expression "ALT2".