CONF iture

It is a 330 simulator.
The main goals were to observe the autotrim behaviour and the response to the sidestick displacement as well as the THS movement.
Next opportunity, thrust could be applied and should applied and retarded just for further observation ...

Note : At no time the USE MAN PITCH TRIM PFD MSG was displayed.
What I figure, and that's only my own interpretation, the trim stopped at 12 deg NU when the AoA reached 30 deg and ABNORMAL ATTITUDE LAW took over.

DozyWannabe

@CONF

Wouldn't that law change have been notified in the ACARS message though? I'm pretty certain that some knowledgeable people in earlier threads were certain that ABNORMAL mode was never engaged.

Clandestino

My bad, apologies. Anyway I don't think that trim played significant part in the grand scheme of things and whether A330 THS is a) too powerful b) barely meeting certification requirements c) somewhere in between is for aerodynamicist to answer.

There are acceleration graphs for all three axes in the appendix.

Acceleration graphs don't confirm that, especially longitudinal accel, at the bottom of page 111, which comes as no surprise as at high altitude a) thrust is quite lower than low down b) there's not much difference between cruise and TOGA. N1 trace is on page 108. It hovers around 100% untill 2:10:45 when TLs are pulled back. Suddenly, stall warning fires and TOGA is selected at 2:10:52. There's dip in N1 with lowest being 80% at around 2:10:50. - just as stick is pulled.


Or they were too distressed & distracted by "STALL STALL STALL STALL STALL STALL STALL STALL" to recognize they were about to stall. DozyWannabe made brilliant comment on forgetting how to recognize and deal with stall:"Like forgetting how to ride a bicycle".

No. Sidestick traces are clear. Very short excursion into nose down were way too short to affect anything. Aeroplane stalled at her apogee and never recovered.

No. Have a look at TLA (thrust lever angles) and N1. Nose drop was due to power reduction. The aerodynamic stall of horizontal stabilizer, trimmable or otherwise, is way more violent than what is seen in pitch trace.

No. TOGA was reselected.

Who said that? It was not they, it was him. He did not pull all the way, all the time but on average he pulled. He pulled when he shouldn't have. He died pulling. That's what RH sidestick trace shows. Is it non-PC to state in plain words what publicly available report has made clear through graph?


Maybe it indeed had. For the time being, I can't figure out what was the sense behind it.

CONF iture

Report 3 itself mentions that the alternate law adopted was alternate 2B and it did not change again subsequently.
In the meantime, I observe that the Abnormal Attitude Law trace is not represented in the FDR data we've been given.

From my personal experience, I have to figure why the trim stopped around 12 deg UP and why it did not later on follow my full fwd request on the sidestick ... ?

Zorin_75

Stalled AF447 did not switch to abnormal attitude law

DozyWannabe

How long did you hold it and at roughly what deflection?

RetiredF4

All quotes Clandestino

Exactly those i was refering, if you noted. But they are not incorporated in the pages 30 + 31, where they would directly show the outcome of the actions. Loadfactor finally is the vital indication what SS inputs and other factors accomplished to the aerodynamical behaviour of the aircraft.

Think it over again. Some thrust vector is pointed downward and adding to lift factor instead of longitudonal acceleration. Also indicated by the VVi increasing again and altitude gain by further 500`feet. As we had a deceleration due to continuous loss of speed, you might see a slow down of longitudonal acceleration due to thrust, but no acceleration as you seem to expect (and PF did as well!). See BEA below

Quote BEA IR3 Page 91: (bolding by me)
02:10:54 The thrust levers are positioned in the CLB detent
02:10:56 The thrust levers are positioned on the TOGA detent.
The N1 increase progressively and reach 103% at 2 h 11 min 02.
 The copilot sidestick is positioned:
- between the half-travel position nose-down and ū of the stop
position nose-up with a nose-up position on average
- between 4/5 of the stop position to the left and 4/5 of the stop
position to the right.
 The pitch attitude fluctuates between 17.9° and 10.5° (Period
of 5 seconds).
 The THS varies from -3.8° to -8.3°.
 The roll angle fluctuates between 8.8° to the left and 4.9°
to the right (Period of 5 seconds).
 The angle of attack 1 increases from 7.4° to 18.3° while the
angles of attack 2 and 3 increase from 10.9° to 22.9°.
 The CAS decreases from 207 kt to 161 kt and the Mach
decreases from 0.66 to 0.51.
 The vertical speed changes from +2272 ft/min to
-3904 ft/min.
 The normal load factor decreases from 1.13 g to 0.75 g
(at 2 h 11 min 03) then goes up and stabilises at 0.85 g.

Sidestick traces show a command to change loadfactor, and would be deflected whatever deemed necessary. And as the loadfactor was well below 1 g (although due to increasing sinkrate) and aircrew not aware that they stalled, there was obviously no reason to increase the unloading further. I give them that credit. We know now that they should have pushed further.... though.

So you are saying, that adding power had no noticable effect, reduction had a big one? Generally you are right, i didīnt take the power change into my equation. Lastly it may have been a combination of both, as the engines with that pitch attitude produce a direct lift vector with part of the thrust.

I disagree. TOGA was selected 02:12:33. Recheck BEA IR3 page 113.

Between 02:11:45 and 02:12:30 THS and elevators had been full down, so SS input, whatever it was, had no aerodynamic effect as it didnīt change any flight control deflection. We can take those out of the equation for any pitch /AOA or loadfactor changes.

Power was idle until 02:12:10, when CLB was selected
Power was CLB until 02:12:33, when TOGA was selected.
Power change to CLB could only have an influence after 02:12:15, considering some conservative spoolup time from idle to CLB.

The G-load change however started already at 02:11:52 from 0.7 g to 1 g at 02:12:00 to 1.1 g at 02:12:10. The pitchdown had resulted in an decrease of AOA, thus wing and THS and elevators got more effective again.

The SS graph does not indicate, what the reason for the overall pulling was. For that we have to look deeper and take the reaction of the airframe into account. Those are the position of the flightcontrols (as those are only indirectly positioned by the SS) and the loadfactor, as that one shows the final reaction to the inputs and is the only feedback (as there is no direct one) the crew had available (by instruments and by feel).

We have to open up our mind to grasp the unpossible and the unthinkable and have to put aside for a moment the obvious. Then we are prepared to dig deeper, to put ourselves in the Cockpit of AF447, in the LH or RH seat or in between / behind like the captain. As long as we make up our mind based on own trained behaviour, based on public oppinion and based on some own agenda (not saying that you do), we will not be open enough.

We also have to get rid of this permanent A vs B bashing or old vs new comparing. We have to think about every aspect of possibilities regardless who invented and designed it. It is hindering and distracting and it is without weight. Anytime i get dragged into that A vs B scheme by an answer to one of my posts, i feel uneasy with the response. Sometime iīve got the feeling that by doing so some posters try to categorize the contributions and make them thus more or less trustworthy.

I for myself believe, that in the FDRīs is still a lot of truth hidden. The compilation of the vital stuff (Speed,Thrust, altitude, VS, AOA, G, SS, elevator, THS and cockpit communication into one graph and with better resolution will give us a better grasp on things. Unfortunately iīm too dumb to fiddle with those and make them myself.

DozyWannabe

@Franzl:

Allowing two F/Os, neither of whom had been trained in manual flying at altitude, to cross the ITCZ unsupervised with a known type-wide problem regarding UAS resulting in enforced manual control is in the realms of the unthinkable to start with - would you not agree? It's almost priming the system for an accident eventually!

Of course I'm talking with the benefit of 20/20 hindsight here, but even given that it has to be considered a spectacularly bad move. What are the "unthinkables" you are considering?

You make a good point regarding perception of acceleration, however if I've read the existing documents right then neither of these pilots had the fast jet experience you do that required this knowledge, and I'd venture to say that the only thing they'd be told to do regarding perception of acceleration and G would be to ignore it and concentrate on the instruments.

RetiredF4

No, i would not agree. You want to pull my leg with such BS.

You need no fast jet expierience to feel the difference between 1.0 g and 0.8 g. My 75Kg would be 60Kg. And that reduction from natural 1g was not for a second like in turbulence (recurring short frequenced loading and unloading, feeling like bumps), but for much longer time .

In our jet we did the extension maneuver (unload and accelerate out of a dogfight) with 3.5 unit AOA equaling around 0.5 g. Most guys in training did stop the maneuver too early after felt 10 seconds, when only 5 had passed and at the beginning didnīt do the unload further then 0.7G

Concerning the "ignore it" passengers and CCīs would beat the hell out of you after .8 gīs for some seconds. Therefore it would be natural that they tried to keep it to the minimum in amount and time possible like they would do on any flight.

Your first comment shows some sarcastic talking, and the last one that you have very limited ideas concerning flying itself.

If that comment now offends you, so be it.

DozyWannabe

@Franzl:

I'm not being sarcastic at all!

I'm asking as simply as I can whether you think putting two people in the flight deck who are not trained to fly manually at altitude, when the type they are flying has a known issue that significantly increases the odds of them having to fly manually at altitude, could be considered a bad idea.

My personal opinion is that it's an incredibly bad idea with the benefit of 20/20 hindsight, and I was genuinely interested in yours.

As for fast jet experience, I wasn't saying that you'd need it to feel the difference, but that I'd expect that you'd need that experience to know instinctively what to do about it, and that the evidence so far suggests that neither of these guys, nor the Captain, had that experience.

Maybe they were instinctively trying to unload, but what little flying experience I have was underpinned with the proviso that your body can and will lie to you about your physical orientation and as such one should ignore it and trust the instruments in front of you.

I don't see how that could be misconstrued as anything other than an honest question and opinion. Just because someone has accused me of arrogance on another thread for having the gall to tell an actual pilot that the sidestick does not control the autopilot doesn't mean it's true!

grity

@RetiredF4,
you can think the rest of the day over the stall time after 2:11:12... but

again the mistake was one minute earlyer after the first tuch of the SS 2:10:07, a few sec after the end of the AP, mayby in a shock the first one ore two sec half pull.... the start of the zoom climb....

but not this pull was the problem, no, the problem was that the PF (and/ore the PNF) did not trust his correct instruments, he was not in the possition to decide if the instruments show him right ore wrong datas..... so he did not realise his climb, the falling speed etc

and for this decision if a instrument is realible ore not, it plays not a role if the values are analog or digital, no, you need a history ore the pathway of the values, and it can not be that it is impossible to show this devolution of datas (of the speed...of the altitude...) with pixels on a monitor in a manner that a pilot is in the position to decide correct. so in this case the PF was not in the position to decide correct.

the stall and the time behind was all later....

RetiredF4

We discussed the training or the lack of it at length, not only in this thread but in several others. To ride that old horse in comment of a serious issue from myself is sensless. You know my answer to these obvious issues long time ago. Your question is not honestly, it is there to distract.

My fast jet expierience isnīt even necessary in the discussion, its again a distraction you use. It is obvious, that any pilot flying with passengers unstrapped in the back tries to avoid g loads less then 1g, and when they are unavoidable when initiating a descent, to do it as sensible as possible. Therefore to shove the stick forward and thus to increase this unloading when already 0.8 (20% less than normal) are felt is expecting too much (also in the hindsight it would have been correct).

You dont get it? Read the loadfactor trace in the timeframe iīm talking about (my previous posts), they where unloaded, although due to other reasons and therefore didnīt increase the unload any further. Therefore the stick position (my assumption).

If you really want to bring your personal expierience into this, then look up the area of loadfactor protection in ALT2, what inputs (speed, aoa, or whatever) are being used, at what values this protections kick in and how it changes with different speeds, and how this protection would work out.

That could be usefull.

Otherwise i think we waste time with each other and others start getting bored. Therefore i will quit answering to such posts.

CONF iture

Maybe mm43 would help at this ... He is pretty good.

sensor_validation

I have seen this mentioned before, and I could design an auto-trim function that had this undesired behaviour - which shows same symptoms as classical "integral wind-up". If the controller doesn't know the output is limited it continues to ask for higher values, and then has further to fall before output comes back in valid range. Surely a correct implementation would include 'integral limiting' or 'desaturation' which would mean mean it would start trimming down soon after fwd input.

OK465

If the dynamics were unchanged, why would one expect the aircraft to require re-trimming?

Clandestino

Since it is: sine (aeroplane pitch + thrustline pitch) x thrust / mass, it is minor. It is also impossible to detect on Nz graph. All IRS accelerometers are strapped to aeroplane and therefore airframe referenced, not ground referenced.

Yes! I'll qualify that in a second.

Yes, but that pitch down was concurrent with thrust reduction! Next two were concurrent with elevators merely moving away from full nose-up! This aeroplane wanted to fly! Combined effort of engines, THS and elevator were needed to keep her stalled - as her attempts to pitch down into flying envelope have attested.

Agreed. They don't show why, just what.

Penetrating as deep as it was possible with my limited means, I could find no fault in BEA's statement that aeroplane performed as designed & certified. Technical path has been well explored and not many pieces of puzzle found there.

Eeerm... not quite. It's impossible to avoid loads below 1G when leveling off or going into descent. I try to be as smooth as my George and he's limited to 0.7G

It uses no air data whatsoever. It's what it says on the box: load factor protection and you just need vertical accelerometer for it to work. Airframe referenced vertical, that is.

Moderation is keyword. No use in opening mind so wide that the brains fall out.

...and discard impossible, implausible, improbable and just plane goofy ones.

What is so unbelievable about the picture of pilot pulling and pulling until the earth catches up with his stalled aeroplane and smites him? We have been losing aeroplanes to it for last century or so - trainers, transports, combat ones. Wolfgang Langewiesche has described the phenomenon accurately back in 1944. Heck, even your long time ago predecessor, Adolf Galland, managed to write off a training glider in such a manner. He survived spinning in because his glider had low wing loading and he kept the stick planted fully back until the impact, so he hit in fully blown spin, rather than in post spin recovery dive. Lady luck also lent her hand. Lucky for him, not so for those who would later stay for a split second too long in the reticle of his Me109.

First, I'm interested in why does it happen at all. When we solve that, then it's the question how did it manage to rise its ugly head in AF447's cockpit.

bubbers44

I know this is taking us away from the current rhetoric but wouldn't two competent pilots encountering ordinary weather conditions at night with an autopilot disconnect because of IAS loss not be able to keep the ac straight and level for a few minutes? The captain, who seems the only competent instrument pilot, was required by regulations to take his rest. Normally flying the long hauls from south america it is divided evenly so all pilots get equal rest. We had the extra pilot figure out the times usually depending on who was flying the trip on when each took their breaks. Our airline had competent FO's in the other two seats so didn't worry about the difficulty of that leg.

I guess airlines hiring low time pilots out of pilot mills can't do that now.

infrequentflyer789

Yes, and I don't see why it should not be there, even if it is a flat line. Perpignan report has it shown (well, the idividual pitch/roll law transitions are). That report also has better quality images of the traces.

My bet would be on abnormal attitude law - entered based on AOA threshold. However, it would depend on how you got to the stall - presumably something was failed to drop you out of normal in the first place, can you tell us what was failed ?


Abnormal attitude law apparently doesn't give the "use man pitch trim" warning, but does inhibit autotrim, (and yes, that makes no **** sense to me either) which would fit with what you saw.

447 didn't trigger abnormal attitude because the ADRs, providing the AOA values, were already rejected by the FCPs due to the previous failures.

Perpignan did show the "use man pitch trim" warning (whether they saw it or not, who knows) because they failed all the way to direct law first. After that they then ended up back in abnormal attitude (which also doesn't make a lot of sense to me - pretty sure direct law is already full authority bar g-load protections, so why if already in direct would you need to switch laws to enable a recovery).

I guess after schipol, bournemouth, perpignan, etc., trimming needs to be part of stall / attitude recovery, whatever type you are on. Autotrim-stops-trimming (after trimming up into stall) is not a type specific problem or mfr or fbw specific (I don't think the 737 gives a warning on it either ?). I don't think it's going to be an easy one to solve (by engineering) either.


Also Conf, out of interest, presumably you flew alt-law in cruise in this sim - how did you find the pitch-normal / roll-direct combination ? As a non-pilot looking at the engineering of it, the control laws look mostly like sensible degradation, but that combination stands out as ugly - fly a different way in each axis! Is it really that bad hands-on, or is it ok ? [Clearly PF on 447 didn't find it ok....]

RetiredF4

Im waiting.

Just read my post again. I was referring to an increase in g load beginning at 02:11:52 until 02:12:30 from 0.7G to 1.1 G, when power was in idle and elevators had been and stayed full down. No power change there, that started later. And yes, it wanted to fly, did i tell anything different? Did i tell it wanted to stall?

Iīm interested in the "why", and as anybody can have a reason to do something or to donīt do something, the answer might be in the interactions of PF input and AC reaction as felt and understood by the crew.

I didnīt tell anything about a faulty A/C, i try to get a grip on what happened, what the crew saw and felt, what the FDR schows in regard to SS input against elevator and THS reaction, and how the aircraft reacted to those. You see my motive in looking for something wrong with the aircraft, i can assure you this is not the case. I try to understand at the moment and iīm not content with your explanation that 3 pilots just f*ed up badly.

Now you are also selective quoting and answer to those selective quotes. Here is my complete sentence, in bold, what you left out.
It is obvious, that any pilot flying with passengers unstrapped in the back tries to avoid g loads less then 1g, and when they are unavoidable when initiating a descent, to do it as sensible as possible.

A bit unfair, isnīt it? Or was it because i didnīt mention the level off? Picky?

On which box? Which values?

Getting personal now. Out of arguments? Or just tired? then dont answer.

It might be normal for you that such things happen, and they may actually happen. I lost friends who rejoined into the mirror picture of a lake in Labrador, everything might happen. Case closed.

You wont find that answer, because you found the culprit already. And when you are not willing to look how it happened and thereby find out what caused the pilots to act like they did (like i and some others try to do), then you wont find out why it happend and you can can close the case.

CONF iture

Nice admission for someone who fought so hard to state otherwise …