Quote:
Originally Posted by Lyman
According to the traces of THS in IR#3, it was parked for 43 seconds. How is a graph different due language in the accompanying text?

HazelNuts reports:
In IR#3, look on page 42 of the english version or page 44 of the french version. That graph was erroneously included as Figure 64 in the english version of the final report, the intended graph can be downloaded separately from the BEA site.

Erroneously included? Or Erroneous?

What does the new graph depict? The reason I ask, is there have been several
Items, removed and replaced, prior, and I tend to go with the original information, unless there is a written and authenticated correction.

For instance, in the original thread on the "ARM 36 G" the included image showed no damage to the end of the strut, it was completely different from what the text of the explanation offered. With the final report, a different image is provided, one with "damage" that more closely matched the text offered from the beginning. Moreover, that image changed in the course of time, to include "better" resolution of the damaged area, whilst the rest of the "photo" was unchanged.

I do not wish to imply any thing at all, but I'll cite the original, when I can.

Rgds.

Firstly - going from "interim" (which is another way of saying draft, preliminary etc.) to "final" implies that the "final" version is the one with correct data. That's the same if you're talking about aviation, legislation, engineering specifications or even creative writing.

Don't think for a second that the data in the interim report went straight from the flight recorders into the statistical/graphing software (which looks to me to have been MS Excel) - it will have been copy/pasted and moved around several times in both cases. The likelihood is that there was a mistake transferring the data that ended up in the interim report that was not picked up in the proof-reading, then later corrected in the final report and annexes/appendices.

In fact the apparent low resolution of the appended DFDR traces in both cases looks to me like the PDF conversion was performed by someone who wasn't aware that the resolution would be degraded to such an extent (or the correct settings to compensate).

The correct Figure 64 is actually quite interesting. It shows the longitudinal, lateral and vertical components of wind during the first minute, the simulation including the effect of those winds (IR#3 did not include those) and the simulation with wind but without pilot action.

Noted. That leaves the two different images of the "Arm 36". Actually three, counting the morphed fasten seat. Interesting...This photo was available from the beginning, since it recovered to the warehouse as part of the VS/Rudder.

Are there different images, and why?

I'll search the other computers, I have all three pictures......

Thank you to Dozy and HN for patience and data....

Which is in itself a significant achievement - the computations involved would have required some very heavy number-crunching.

But in mine it didn't for the THS.
Also, my full fwd action on the stick did not change the attitude, were the elevators moving in the full down position, I would expect so but cannot guaranty it as I didn't check the flight controls page.

Why would they try in a simulated session as a sim is not representative of real life.
Our sim experiences were for fun only, we did report what we saw, that's it.

The tremendous amount of messages and interest around the THS show that adequat information is clearly needed in the official documentation or through the BEA reports as last ressort.
You have demonstrated already your misconception.
I, as an Airbus pilot, would need to know much more.

THS time response
 

In a limited defense of DOZE, I submit:

Other than the aft cee gee problem that we had with the Viper, I agree. Holding stick forward for a few seconds should see the "auto trim" kick in to allow reducing stick fwd/back pressure, just as if you rolled the trim wheel. Secondly, you don't want a short time constant on the auto trim. A few seconds, like 3 or 4, should be about right. Otherwise, you could have a "computer-assisted PIO", as if the auto-trim reacted in a tenth of a second, heh heh. Can also average the stick inputs for a few seconds and not require a constant 1.3 gee or -0.85 gee command. Ahhhh, the wonders of a FBW system.

I agree with several here that the auto-trim did not help, but I agree with those that maintain it was not the major contributing factor. No doubt trimming nose down using the wheel would have helped, but that didn't seem high on the priority of the PF. And the nearly constant nose up command seems to me to be the most damning crew action.

I am becoming upset with the "personal" stuff I have seen lately.

If anyone wants to attack me, then I already have my kevlar flak vest on and NOMEX shirt.

Otherwise, I would prefer to see a more "professional" dialogue, as the name of this forum implies.

How long did you hold it for?

In this case it really needs to be a positive and sustained movement (just as it would be on the yoke in a traditional setup). I don't know the circumstances of your experiment, but in ours I was fixated upon trying to follow the ADI and the trim wheel simultaneously - almost as if I had my right eye and left eye trained in different directions. On the second attempt I followed the ADI and the standby altimeter and V/S (as the only way to simulate similar conditions involved failing the ADIRU on my side).


It can't realistically simulate aircraft behaviour outside of the tested envelope, but it will always be faithful in terms of system behaviour, which ultimately was what we were trying to prove.

Maybe, but as far as I can tell the "tremendous amount" of messages seem to be coming repeatedly from the same 4 or 5 posters.

The BEA's remit (like any other accident investigation body) is to report on facts derived from recorded data applying to the incident. In order to establish those facts, experiments are performed to test the circumstances in which the recorded data makes sense.

If those experiments don't apply to the data from the incident then the information derived from those experiments doesn't end up in the report.

As I said earlier, prior to a lucky break in which a faulty B737 rudder PCU reversed itself following thermal shock with no fatalities, the US NTSB was forced to publish a report on UA535 as having no conclusive data - they were about to do the same with USAir427. Investigative agencies can only publish relevant data which can be proved scientifically.

No matter what your personal opinion on autotrim is, the fact is that it did not perform contrary to the way it is supposed to and as such has no place in the report.

Misconception of what? (and I sincerely want to know). You tell me I'm wrong, yet there are plenty of posters (including line pilots) who say I'm not.

Hi,

What about ......
Incidence more of 30°
Unusual position (law)
THS frozen

DW
In first place I dunno why a BEA report (if I take in account your criteria) as the BEA already tell in a interim report that the plane acted as per design ..
So nothing who din't work as it was supposed to ...
Seem's the BEA report is only pointing and investigating the pilots actions (hence the human factor group created especially for)
paradoxically.. many recommendations concern the plane .....

If I may add to DW's reply: It should not be assumed that the simulation was done in a training simulator. More likely it was done in an engineering simulator, or perhaps just in a computer.

Not sure what you're getting at
Abnormal Attitude Law was never triggered
No evidence to suggest that because no input was ever made that would have moved it.

The BEA's remit concerns the events of the accident (technical, human and procedural). They may have confirmed that the aircraft behaved as per spec by the time of IR#3, but the Human Factors team required a lot longer to attempt to draw positive conclusions about the crew's behaviour.

The BEA are "pointing" at nothing (nor have they ever done so) - they have simply produced a report which states that based on the information they have, this was the likely sequence of events. Where conclusive evidence exists, they have outlined it - and where evidence is inconclusive, they have explored the possible reasons for it.

One of the unfortunate side-effects of the Continental approach to accident investigation is that the BEA - who are responsible for a purely factual approach to the investigation - are frequently misattributed to be behind the later legal and criminal findings.

My guess would be that the systems behaviour testing was performed at a Level D sim in Toulouse, and the aerodynamic behaviour was simulated on a "big iron" setup normally used for design work.

HN39 post 1233
Hazlenuts, I think you mis-understood the intent of my post. It was a hypothetical what would have happened if the aircraft dropped to Direct Law instead of switching to Alt2B? My conclusion was that the aircraft would not have been easier to fly, but that the likelihood of disaster was significantly less.

PF would still have rocked his wings, and he would have pulled his nose up as he did before, but as the aircraft slowed, he would have had to pull much harder to hold the nose attitude, or he would have had to trim.

But trimming nose up means intentionally selecting a lower speed. That would have required a conscious decision on his part. The aircraft would have actually told him it was getting slow by the amount of nose up effort required to hold the nose up.

The aircraft crashed because PF did not understand what was going on, not because it was difficult to fly. Autotrim masked the loss of speed.

Using a lowest common denominator design strategy, dropping to Direct Law instead of Alt 2 B would actually improve the pilots understanding of where the aircraft was in its flight envelope. I'm betting he would not have rolled in more nose up trim if it was under his direct control.

MachinBird, I almost agree. I totally agree with the intent of your post and you did understand my earlier post. If we're talking about any other transport category in my knowledge, their speed stability would have required more elevator force to hold the nose up. We both understand what that means I think. The Bus, however, offers no control feedback, therefore the pilot would never know how much effort was required to maintain the stall.

That is my gripe with the Bus, not the fact that it auto trims, or how it auto trims, but that it isn't speed stable in trim. Multiple tens of thousands of pilots around the world fly multiple tens of thousands of airplanes and the vast, vast majority of those airplanes are speed stable.

What I find surprising is that the only crew that couldn't deal with the Airbus and UAS was a Bus only crew. You might have thought that some of us old steam gauge cable control dinosaur pilots with more time trimming on short final than some ab initio pilot would have been the ones to mess it up. Cheers.

Something to think about.

A line pilot almost never applies any significant amount of nose down elevator. I fly narrowbody Bus's, not widebodies, but I spent some time observing my own last five legs and even though I flew one leg from sea level all the way to FL290 and leveled off there, I only pushed three times. Once to smooth out the flight path upon flap retraction, once to accelerate at FL100, and once to level off at cruise. Not one of those nose down inputs required more than a minimal forward SS input. Each input require approx 1/8th the available forward stick travel.

If the pilot is a gear up , autopilot on, kind of guy: or a minimums autopilot off, kind of guy. It is very likely that any significant amount of forward SS is a very foreign situation.

PS, no I don't stir mayonasse, nor make quick hits on the SS. I apply continuous pressure and I hand fly extensively.

Edit, after further thought, I did make many minor corrections to pitch during the climb and each was smaller in SS deflection than the three I recount above. Be that as it may, any forward SS movement make in normal flight is extremely minor.

Machinbird,

It wasn't clear to me that you were discussing direct law. Thanks for clarifying.

EDIT::
Agreed, but he didn't need to trim to stall the airplane, the stickforce SS on stop would have been the same, and that did not deter him.

As EMIT points out on the other thread, in the end the human factor is stronger than the technology.

I simply can't believe what I am reading.

From whatever cause the airframe gets so badly trimmed that it goes into a slow speed fast sink condition.

We are calmly told that the way out is to apply a total of ten seconds full nose down before any beneficial effect is seen.

Not exactly intuitive, and unlikely to be discovered amongst all the other similarly improbable actions.

The aircraft simply should not permit this to happen. There is no justification for the THS to move so far so quickly. If it had been rate limited, at an appropriately slow rate, it would not have put the airframe in such an impossible state.

Or can anyone think of a reason why the autotrim would have to respond so dramatically in steady high altitude cruise?

CVR revisited
 

On the one hand, the sterile, "What's it doing now?" of the CVR may accurately reflect the nature of the conversation in the cockpit on this fateful flight. Furthermore, it may actually shield the pilots from greater criticism than that to which they have already been subjected. On the other hand, as an interested observer since Thread 1, I'd like to know if the pilots conducted themselves in the sterile manner depicted, or if they screamed profanitiy-laden abuse at each. My desire is not prurient, rather, the tone of the conversation will, in my opinion, yield a degree of context that is very much lacking in the report as presented.

Hi mike-wsm,
The stab trim simply supported the elevator control as they responded to the real reduction in airspeed. The PF attempted to fly outside the envelope. If he had maintained at FL 350, the real airspeed would not have changed much, and the stab trim would not have had to move.

Ratty, friend,

Yes, understood. But that does not answer my question. I suggested rate restriction and asked for reasons why rate restriction would be unacceptable.

Final report, 1.1 History of the flight: