Lyman

HazelNuts39

Quote:
Maybe slightly but, IMHO, with full nose-up elevator maintained, not enough to unstall the airplane. I don't expect the airplane to have the straight-wing characteristic of a nose drop that can't be arrested.


The object of my earlier response was not recovery from Stall, but the alerting effect of an elevators only Nose Drop earlier in the sequence. My contention is that the THS' effect was counter to certification requirements, it disallowed an earlier and standard response of a Stalling airframe.

One cannot escape the fact that Autotrim, in this instance, would never be allowed in any aircraft, if it took away the standard dependence on both buffet, and Nose Drop


Besides, recovery from Stall requires the use of normal controls only, and nothing else. Having to depend on trim to recover, or avoid, is not allowed....

DozyWannabe

It can if you hold it there, and it was held there most of the way down.

Obviously there's a limit to how useful sim experience is outside of the envelope, but with consistent stick-forward it is possible to counteract the autotrim with plenty of time to spare - if it is noticed.


I suspect it was analyzed - and summarized in terms of the difficulty of pulling out of the stall if not trained to recognize it in the report. Accident reports tend to summarize rather than detail every experiment performed to the Nth degree - otherwise they'd routinely run into thousands of pages.

Case in point - the NTSB did not include the details of their experiments on the 737 rudder PCU in the original reports on UA535 and USAir427 because they could not prove a link. Only when a link was proven years later were those reports revised.

Well, they did put a hard autotrim limit on the A320 - it'd be a tragic irony if they didn't do it on the widebodies in response to pilot complaints regarding lack of full authority.

The BEA of course. Airbus are at more risk from a lack of transparency as opposed to secrecy.

Lyman

BEA were hobbled after the memo they released that AIRBUS used to proclaim "There is nothing new to suggest any mechanical malfunction on the aircraft..."

That colored the reports, and prevented BEA from countering AIRBUS later.

Airbus have the full record, the complete CVR, DFDR etc. yet you are to suggest they do not control the outcome? Only BEA have also the records. The ones who do not disclose, create no more havoc than those who allow the suppression of information....satisfaction short of all the information is the sign of a partisan, a benefactor, even.

From CONFiture
"Most probably - But the limit of efficacity for the elevators alone is reached earlier, and the stall cannot develop in such a pronounced way."

My proposal is that the THS prevented a STALL, allowing entry into what can best be described as a MUSH.... Whatever you call it, it bore no resemblance to a normal STALL. Further confusing the pilots....

jcjeant

Normally (at least I hope) legal experts appointed by the judge hearing the case must also be in possession of all these evidences (includes access to parts of the plane recovered and postmortem analysis)
If this is not the case (which I do not think) it would be a very serious problem
(how do appraisal work if there is no evidence and documents to appraise? )

Lyman

Jcjeant...

Howdy. You say:

"If this is not the case (which I do not think) it would be a very serious problem
(how do appraisal work if there is no evidence and documents to appraise? )"

Spot on. Who determines why a plaintiff shall have documentation, and prevent it from the public at large? It is absurd, the plaintiffs have been harmed, and the rest of us subject to the same harm! There is no compelling need to hide any of it, if it is allowed to be had by some. The plaintiffs will hear it, it is their entitlement, and having heard it, will have broken the dam for the rest of us.

Hearts cannot break twice.....it would be the wish of those lost, that those responsible NOT be allowed to hide like cowards.....

DozyWannabe

How? There's nothing to stop them saying different if contradictory evidence comes to light (again, see UA535 - it took years, during which time a final report was released by the NTSB that considered the evidence inconclusive).

Let's look at that point from another angle - how would hiding problems benefit Airbus?

Er, nose-high attitude leading to loss of control in pitch and bank with a rapidly unwinding altimeter? Sounds a lot like a stall to me...

Lyman

Er, nose-high attitude leading to loss of control in pitch and bank with a rapidly unwinding altimeter? Sounds a lot like a stall to me...

The pitch was not lost, and bank was controlled.... And it remained nose high....

"but it was the pilot who held it nose high".......no one knows, it was the pilot who held the stick back, and the THS that held the nose.

The thing that concerns is the lack of the only two airframe warnings available, buffet and Nose drop. Besides, what matters is what PF thought, not you nor I...

DozyWannabe

The nose came down while he was pulling up - if that's not loss of control, then what is? And the bank was not controllable via aileron once the stall had begun

It is possible to counteract THS with elevator (albeit with significantly reduced authority), however the THS was in the position it was because the pilot had held the stick back for so long.

According to the CVR, both were in evidence - but then it seems to me that you will always find something else to be "concerned" about whenever your current concern is disproved.

Wouldn't you say it's an indication of running out of plausible arguments when one demands proof of something that it impossible to prove?

jcjeant

Again I agree .. but ...
hiding problems .. does not mean not to address them ...
Everything is a matter of doing it gently .. without alarming that matter ..
Seen from this angle .. this can be beneficial for Airbus ...
There is an appropriate expression in French
On lave son linge sale en famille
Wash your dirty linen in the family circle

DozyWannabe

@jcj:

Not at all - McDonnell Douglas tried that in the '70s and the black mark it left on their reputation and that of the DC-10 was never truly erased.

To my mind there was never been an "under the radar" update in terms of either hardware or software to a FBW Airbus type.

jcjeant

If Airbus make some modifications on their aircraft after the AF447 accident (related to) ... this will be the explicit recognition that their plane(s) had problem (s) (was not sure) before the accident ...
So in effect .. this will not be beneficial for Airbus and may have unfortunate consequences for Airbus at the trial (even if their answer is "we don't know before")
And it's in contradiction with their former declaration in the press ...

Lyman

According to the CVR, both were in evidence - but then it seems to me that you will always find something else to be "concerned" about whenever your current concern is disproved.

Show us where. Both stall cues please. From the CVR. Not the DFDR. In evidence, and acknowledged by the pilots....

DozyWannabe

Not really - the report acknowledges pre-existing faults with the pitot tubes, which is the reason Airbus was charged alongside AF.

Not true - the declaration was notably specific, and stated that there was no *mechanical failure* over and above the pitot tube problem that was already known. There was no mention in that declaration of possible contentious design issues or unforeseen human interface problems. The statement did not state that the aircraft was perfect - merely that it behaved as designed. Whether that design still stands up in the face of the other evidence is open to question.

The presence of the cues versus acknowledgement by the pilots are two separate issues, as I'm sure you well know. The CVR proves that they missed several obvious cues - both electronic and aerodynamic.

This is not to say that they were bad pilots, simply that they were in the wrong place at the wrong time.

RetiredF4

So you agree now, that the NU trim should have been designed to stop like it does in the A 320. That is a big advance in this discussion.

You have evidence for your assumption concerning the cause of this change in design? Afaik there might be lot of other reasons, why do you suggest it was caused by pilot input?

BOAC

- I have missed that fact - can you elaborate a little please? Does it have the necessary option to deliberately over-ride as I proposed months ago following PGF?

- unless you have evidence that control in pitch was 'lost' I think that line is misleading. I think you are confusing a known aerodynamic shift in CP with 'loss of control'? I understood from the report that they were in fact able to maintain a high nose attitude in pitch with side-stick/THS and/or lower the nose occasionally with side stick? Is that not 'control', even if 'up' was the wrong 'control'? Am I wrong?

Carjockey

@Lonewolf

It's nice to have and I suggest that yes, you have to have.

If your instruments go haywire then at least you have another very valuable point of reference.

As stated previously, pilots are reliant on their flight instruments. If your instrument readings are questionable than a visual back-up on engines and control surfaces (via CCTV) surely cannot be a bad thing.

The Kegworth accident is an excellent example. If the pilots had been able to visually verify which was the problem engine, the accident could have been avoided.

OK465

I find it somewhat interesting that for a short time there were only three pilots in the world who have ever actually performed this particular maneuver...

We have the DFDR traces of short term snippets of SS movement and resulting aircraft response without any long term validation nor an AOA ever below 30 degrees...

PPRuNe has 2 or 3 pilots who have objectively and insightfully described their experiences with this maneuver as actually performed in an A330 simulator...

yet we have a plethora of posters who have never touched an A330 SS who 'know' exactly how it must have been.

Lyman

I have looked at my logbooks, and I can say that I have experienced roughly three hundred Stalls, always on purpose, and never alone.

Maybe half that number of Spins, again, always on purpose, and never solo.

I have no idea, what the 330 is like. If I have suggested I have even a clue, I am deeply sorry. I will say that I have experienced controlled descents with a Stalled wing (s), but that is not pertinent either. I know.

Bottom line. Virtually none of the conclusions expressed here give me comfort. I think the pilots are given short shrift, and through time, innuendo, slur, and lazy data have cemented their legacy. And that is so wrong.

DozyWannabe

On the A320 the autotrim stops (at about 6 degrees nose up if I recall correctly), and if you need more trim than that it must be wound on manually with the wheel - so the wheel in effect becomes the override mechanism.

Perhaps I should have been clearer - while a degree of control was possible throughout the sequence, the fact that the nose dropped (due to stall) when the command given was nose-up - i.e. for that short period not responding to the controls - meant that the aircraft behaviour was consistent with stall.

I neither agree nor disagree - I don't have the evidence to support a case for one design being better or worse than the other.

I didn't suggest that was the cause (as you point out, I don't have the data) - I said it would be ironic (in the tragic sense) if the design change was a response to criticism based on perceived lack of authority.

Think of it as a bit of whimsical conjecture, not a serious claim.

Organfreak

DW say:
3 degrees