Originally posted by tsv
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Boeing Crash in Russia
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Originally posted by Gabriel View PostMaybe, could be, that they didn't disconnect the AP and they were fighting it in some way and then when they disconnected it the plane was badly out of trim (due to the AP trimming opposite to the pilots' inputs). Still can't close the sequence, but there could something along this theory.
Have to research this when I can find the time.
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One of the interesting factors in the Perm crash in 2008 was that the Pilots had not really had sufficient conversion training from the TU-134 to the B737-500. And at least one of them didn't have great English either. When they got off course and were also unexpectantly asked to change to a different approach (due to a Lufthansa flight departing in the opposite direction to normal) they really struggled to catch up with the plane. They did not have enough time to do their check lists and enter new parameters into the flight computer. Their problems were complicated by them having issues with Asyncronous Throttles which they had not been trained to manage properly. Slowly but surely their situation deteriorated until they totally lost Situational Awareness and all control of the Aircraft.
I am interested to know what Aircraft the Tatarstan Air Pilots were trained on and how thorough was their conversion course. And also their proficiency in English. Boeing and Airbus Aircraft are (reportedly) very easy to fly when things are going normally but if you have to troubleshoot under pressure when you don't completely understand the Aircraft things can go wrong - quickly.
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Originally posted by Evan View PostI was thinking the exact same thing except that maybe the AP disconnect was uncommanded and unexpected. I don't know the 737 as well as the A320 but perhaps the AP disconnected at stickshaker or because the situation exceeded AP capability in a badly out of trim state and the pilots were caught off-guard. Disorientation and a hard nose-over which might have given them a sensation of increasing pitch. It really stinks of a trim issue and a sudden transition from autoflight to me. Hasn't something like that happened before? Maybe it wasn't a Boeing...
Have to research this when I can find the time.
In another example, the throttles were retarded by the AT (I don't remember why) and the AP kept adding nose-up trim to keep the GS. At some point (late) the pilots noticed the slow speed and high pitch and started a GA. It should be pointed that the trim was even more nose-up than needed to fly at that slow speed, because normally you'd have thrust which, with the underslung engines, already provides some nose-up "trim" (read pitching moment) so you need less nose-up stabilizer trim.
The thing was that the pilots initiated the go-around (AP/AT off, TOGA, nose up, flaps 15, gear up) and at the same time the stickshaker triggered. So the plane was trimmed for just the stickshaker AoA with the engines at idle and flaps 30, which means an even a higher AoA with the engines at TOGA and flaps 15 (flaps 30 provide more nose-down pitching moment due to the increased camber and drag below the CG). That, combined with a still deteriorating speed, rendered the elevator ineffective to lower the nose even with full forward yoke. The airplane (always with the pilots holding full forward command) pitched up, slowed down, stalled, pitched way down, accelerated a lot in the fall, and only then (and luckily before hitting the ground) there was enough airflow for the elevators to recover the effectiveness and control the pitch. However, as the speed kept increasing, the pilots again had problems to control the pitch up and only then it occurred to them what should have occurred as soon as full nose-down elevator was not enough to prevent the plane from pitching up the first time: apply nose-down trim, and the situation was finally controlled and stabilized in a normal climb, repositioning for a second approach, and normal landing. Scary, uh?
I'm trying to think a scenario where the opposite would happen (severe nose-down trim that catches the pilots by surprise), but I couldn't figure one yet, besides the obvious trim runaway.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View PostI'm trying to think a scenario where the opposite would happen (severe nose-down trim that catches the pilots by surprise), but I couldn't figure one yet, besides the obvious trim runaway.
An unlikely scenario, but at this point most scenarios seem unlikely!Be alert! America needs more lerts.
Eric Law
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Originally posted by elaw View PostThis is parlour talking of course, but how about if they were above glideslope, the AP was engaged and trying to capture the glideslope, and the pilot is pulling back on the yoke, trying to extend the glide or starting a go-around maneuver (not realizing the AP is engaged)? The AP keeps adding nose-down trim trying to reach the glideslope until suddenly the flying pilot realizes the AP is on, lets go of the yoke to turn it off, and down goes the nose?
An unlikely scenario, but at this point most scenarios seem unlikely!
1- Why would the pilot let of of the yoke? To turn it off? The AP disconnect button is right there on the yoke, and there is a good reason for that.
2- The pilot would have been already fighting the out-of-trim condition before turning the AP off. So the fact that the plane is out of trim when the AP is disconnected shouldn't take him by surprise.
But as you've said, all speculations and whatever happened there, chances are it will be something odd anyway.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Please watch this documentary. It is excellent and provides great insight.
It is a little dated but not enough to take away from what is happening with the "little Flots."
P1: http://youtu.be/TSK2gLDpOYY
P2: http://youtu.be/zGocQXX3sSU
P3: http://youtu.be/G9mzefejoZ8
P4 :http://youtu.be/c1uZVnN037YI do work for a domestic US airline, and it should be noted that I do not represent such airline, or any airline. My opinions are mine alone, and aren't reflective of anything but my own knowledge, or what I am trying to learn. At no time will I discuss my specific airline, internal policies, or any such info.
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Originally posted by Gabriel View PostInteresting. We'd have a puzzle since apparently the pilots disconnected the AP and manually flew the GA, managing to reach 2300ft and 25deg nose up before nosing over and diving vertically.
Maybe, could be, that they didn't disconnect the AP and they were fighting it in some way and then when they disconnected it the plane was badly out of trim (due to the AP trimming opposite to the pilots' inputs). Still can't close the sequence, but there could something along this theory.
AP status, trim angle, control inputs and the like should all be there in the FDR.
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Originally posted by Gabriel View PostThe odd things about this scenario are:
1- Why would the pilot let of of the yoke? To turn it off? The AP disconnect button is right there on the yoke, and there is a good reason for that.
2- The pilot would have been already fighting the out-of-trim condition before turning the AP off. So the fact that the plane is out of trim when the AP is disconnected shouldn't take him by surprise.
But as you've said, all speculations and whatever happened there, chances are it will be something odd anyway.
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Originally posted by TheKiecker View PostGabriel , do I get a gold star and a slap on the back for my logical INSIGHT ?I do work for a domestic US airline, and it should be noted that I do not represent such airline, or any airline. My opinions are mine alone, and aren't reflective of anything but my own knowledge, or what I am trying to learn. At no time will I discuss my specific airline, internal policies, or any such info.
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Originally posted by TheKiecker View PostGabriel , do I get a gold star and a slap on the back for my logical INSIGHT ?
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by TheKiecker View PostWould the yoke pull forward if it was trimmed to nose down viciously quick ? Not much altitude to play that game.
Now, I don't know how "powerful" the trim of the 737 is or if it can be overridden with the yoke.
In any event, the fact that the trim is moving is very evident and impossible to miss. The trim motor make a quite loud and very characteristic high-pitch whining noise and you have two big black wheel (one at each side of the central pedestal) with white marks turning and making a clacking noise as it does. These wheels are the things that you rotate to adjust the trim manually. (these trim wheels have a nick name at least in Spanish which is the equivalent: The bacon slicer machine).
There is one emergency for which every pilot trains (and no, this is no guarantee) which is precisely the trim runaway. The electric trim is switched off, the airplane is first controlled with the yoke (fighting the out-of-trim situation) and then the trim is corrected with manually rotating the trim wheel.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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Originally posted by Gabriel View Post
I'm trying to think a scenario where the opposite would happen (severe nose-down trim that catches the pilots by surprise), but I couldn't figure one yet, besides the obvious trim runaway.
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Originally posted by Evan View PostTrim at GA is nose up, underslung engines are adding upward pitch, therefore flight director is dictating the exact, correct, totally resonable and safe attitude?
1) Flight directors are really smart- so unless it's some sort of Microsoft blue screen computer error with the flight director, I don't think so.
2 (and your idea is doubly wrong) the flight director tells you what the attitude of the plane should be, not what the control inputs should be.
If the engines are pushing the nose up too much the flight director will provide a target that is the correct nose up attitude...you have to figure out the control inputs....and if you go nose down....the flight director still shows that perfect nose up attitude.Les règles de l'aviation de base découragent de longues périodes de dur tirer vers le haut.
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Thanks 3we for preventing a Gabriellian post. Now it's enough with a...
As 3we said.
--- Judge what is said by the merits of what is said, not by the credentials of who said it. ---
--- Defend what you say with arguments, not by imposing your credentials ---
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