B-738 Crash in Russia Rostov-on-Don
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So, with as much nose down trim as it is possible muster and full control column forward to induce the nose over, the speed builds to a speed that the elevator becomes insufficient to overcome the stabilizer. Either that or the tail becomes effectively stalled and is unable to produce sufficient downforce...? Control is not possible until the sufficient nose up trim has been applied.
If sim recreation is correct...3100 in MCP, trying to level off with thrust initally at TOGA...so following FD to level off at incorrect MCP requiring applying lots of down stab trim. Then AT pulls the thrust off putting the aircraft in an extreme out of trim condition.
Hand flying with AT on combined with mode confusion. Very plausible.
Hand flying with AT on combined with mode confusion. Very plausible.
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Something odd in this post ....
"I was pulling as hard as I could on the yolk .... " Old King Coal telling about what happened during a sim session.
This man does not know that it is called a yoke, not a yolk?
Too, he says that the control column was fully back, "the control column [was] buried hard back in to [his] waistline" while he "was pulling as hard as [he] could on the yolk [sic], with both arms .... "
If he had the control column fully back, why should he need to pull as hard as he could, given that it's not going to move past the full aft position? It has hit the travel stop, so no need to keep pulling any harder than necessary to keep it there.
I can understand that mistrimming full nose-down might make it impossible to move the control column fully aft, but that would not be the case here; the control column is reported to have been fully aft. Why, then, should the aircraft not respond to full up elevator when it would not seem to be stalled, given the report of rapidly increasing airspeed?
Three things that do not fit: This description does not fit the way that an aircraft should normally behave; the description of the action of pulling extremely hard on a control column on the aft stop does not make sense as written; who can go through training and not know that it's "yoke," not "yolk"?
This man does not know that it is called a yoke, not a yolk?
Too, he says that the control column was fully back, "the control column [was] buried hard back in to [his] waistline" while he "was pulling as hard as [he] could on the yolk [sic], with both arms .... "
If he had the control column fully back, why should he need to pull as hard as he could, given that it's not going to move past the full aft position? It has hit the travel stop, so no need to keep pulling any harder than necessary to keep it there.
I can understand that mistrimming full nose-down might make it impossible to move the control column fully aft, but that would not be the case here; the control column is reported to have been fully aft. Why, then, should the aircraft not respond to full up elevator when it would not seem to be stalled, given the report of rapidly increasing airspeed?
Three things that do not fit: This description does not fit the way that an aircraft should normally behave; the description of the action of pulling extremely hard on a control column on the aft stop does not make sense as written; who can go through training and not know that it's "yoke," not "yolk"?
Autocorrect is the cause of many sins.
If the stabiliser is out of trim, combined with the force effect of reducing thrust, it might easily be possible to run out of elevator authority.
The MAK report makes clear that the approach was flown manually, which suggests AT off as well given Boeing guidance.
Do Flydubai use the AT ARM mode when flying manually?
Fundamentally, without seeing CVR/FDR data we are all speculating. However, as a 738 driver, I am learning things about my aircraft and thinking a lot about my flying technique. This accident is pretty much a daily subject of conversation in the flight deck.
If the stabiliser is out of trim, combined with the force effect of reducing thrust, it might easily be possible to run out of elevator authority.
The MAK report makes clear that the approach was flown manually, which suggests AT off as well given Boeing guidance.
Do Flydubai use the AT ARM mode when flying manually?
Fundamentally, without seeing CVR/FDR data we are all speculating. However, as a 738 driver, I am learning things about my aircraft and thinking a lot about my flying technique. This accident is pretty much a daily subject of conversation in the flight deck.
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Bank angle in the SIM video
In the final seconds of the SIM video, the aircraft banks over by 90 degrees prior to impact, just like the crash videos shown earlier in this thread, as it emerges from the cloud base.
Some commentors have said that such a bank angle is not possible with an extreme nose down pitch, or that it would result in a turn away from the runway, or that it would be a level CFIT anyway, despite visual evidence to the contrary.
It seems to me that the SIM has exactly replicated the event as recorded on CCTV, so why is that? And if so there ought to be a lesson for all.
Some commentors have said that such a bank angle is not possible with an extreme nose down pitch, or that it would result in a turn away from the runway, or that it would be a level CFIT anyway, despite visual evidence to the contrary.
It seems to me that the SIM has exactly replicated the event as recorded on CCTV, so why is that? And if so there ought to be a lesson for all.
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The bank in the simulator video starts when the pilots turn the control wheel to the right.
Are they replicating the exact flight recorder findings, or are they flying the simulator the way it appeared to have happened?
Big difference.
Are they replicating the exact flight recorder findings, or are they flying the simulator the way it appeared to have happened?
Big difference.
Why, then, should the aircraft not respond to full up elevator when it would not seem to be stalled, given the report of rapidly increasing airspeed?
chuks...you are running with several misconceptions.
The stab trim moves the entire horizontal stabilizer. The elevator is about a tenth the surface area. Therefore the tail can be "flying up" with the elevator deflected fully up.
Also, probably not pertinent in this case but airspeed has a indirect effect on a stall. A wing can be stalled at any airspeed. One can also accelerate a stall on a wing or tail by having enough surface deflections to disrupt airflow such as when a stabilizer is deflected in the opposite direction of the elevator.
The stab trim moves the entire horizontal stabilizer. The elevator is about a tenth the surface area. Therefore the tail can be "flying up" with the elevator deflected fully up.
Also, probably not pertinent in this case but airspeed has a indirect effect on a stall. A wing can be stalled at any airspeed. One can also accelerate a stall on a wing or tail by having enough surface deflections to disrupt airflow such as when a stabilizer is deflected in the opposite direction of the elevator.
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There are pilots around today who know how to work an aircraft, but they don't know how the aircraft works.
The whole issue of "Trimmable Horizontal Stabilisors" is a perfect example of this.
If you have managed to move the THS from where it needs to be, to somewhere else- you have entered a world of ****, and will remain there until you have recovered the situation by putting the THS back to a more appropriate position.
The THS is big. The elevators, not so much.
THS set for "big nose down?" You can pull as hard as hard as you like on the thing that moves the elevators, and you might even recover, but you'll be hauling back until that THS is in its rightful position.
THS set for "big nose up?" Houses will initially get smaller, but not for long.
That powerful THS is what gives our aircraft the ability to be safely trimmed for take off with all sorts of different loads.
Get it out of position in flight and the best you can hope for is paperwork and awkward interviews.
The whole issue of "Trimmable Horizontal Stabilisors" is a perfect example of this.
If you have managed to move the THS from where it needs to be, to somewhere else- you have entered a world of ****, and will remain there until you have recovered the situation by putting the THS back to a more appropriate position.
The THS is big. The elevators, not so much.
THS set for "big nose down?" You can pull as hard as hard as you like on the thing that moves the elevators, and you might even recover, but you'll be hauling back until that THS is in its rightful position.
THS set for "big nose up?" Houses will initially get smaller, but not for long.
That powerful THS is what gives our aircraft the ability to be safely trimmed for take off with all sorts of different loads.
Get it out of position in flight and the best you can hope for is paperwork and awkward interviews.
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Just questions, not necessarily misconceptions, because that narrative raises more question than it answers.
For me it starts with this "yolk/yoke" business, which I have encountered previously. It's a red flag, although it might also be something of no real significance. After all, "On the internet, nobody knows you are a dog."
I understand how the pitch trim works by moving the stabilizer, thank you. It was one of the first things they taught me, along with that that thing you yank on is called the "control yoke." In this scenario, though, the trim is grossly out, set for (full?) "nose-down," yet the PF is able to pull full "nose-up" against it, when the aircraft does not respond to that because of the trim being set nose-down. That implies that the trim had to be rapidly re-set, what, full nose-down during the go-around? Who does that, and why? Too, you are pulling with all your might against the pitch trim, without bothering to operate the pitch trim switch which is right there on the yoke? That should be reflex, I would think.
I guess we would need to be told how OKC "found it quite easy to produce a set of (seemingly innocuous) control, power, and trim inputs that would lead to the outcome that [he] experienced," such that "any sufficiently experienced B737 pilot could probably easily replicate the same, with a little imagination."
In other words, a go-around results in a fatal impact at a 40º nose-down angle with increasing airspeed at zero thrust because of control, power and trim inputs. That's a pretty alarming scenario because I can not imagine what those "inputs" from a "sufficiently experienced B737 pilot" might be. I think we need to be told a bit more about that, because this seems to be a very implausible narrative, just on the face of it.
Strange things do happen; there have been other crashes that require reading the final report to understand how they could have happened, when that was because of very strange control inputs on the part of the crew. (That Colgan crash near Buffalo is probably the worst example of that, when even the accident investigators had no real answer to why the crew flew the airplane as they did, when their strange control inputs caused the crash.) Here we have an equally strange scenario being presented in a veiled manner, out of fairness to the official inquiry (?). Okay, if you say so!
Another thing: I doubt that professional accident investigators pay very much attention to posts made here, but non-pilot members of the public, and some reporters too, probably do read these posts.
I just watched that clip from the sim reenactment, linked above and mentioned below, and found it completely uninformative. We need to be able to read the instruments, see the pitch trim settings, and see the PF control inputs in order to understand what we are being shown there, other than "a crash." What is the point of making such a video as that one?
For me it starts with this "yolk/yoke" business, which I have encountered previously. It's a red flag, although it might also be something of no real significance. After all, "On the internet, nobody knows you are a dog."
I understand how the pitch trim works by moving the stabilizer, thank you. It was one of the first things they taught me, along with that that thing you yank on is called the "control yoke." In this scenario, though, the trim is grossly out, set for (full?) "nose-down," yet the PF is able to pull full "nose-up" against it, when the aircraft does not respond to that because of the trim being set nose-down. That implies that the trim had to be rapidly re-set, what, full nose-down during the go-around? Who does that, and why? Too, you are pulling with all your might against the pitch trim, without bothering to operate the pitch trim switch which is right there on the yoke? That should be reflex, I would think.
I guess we would need to be told how OKC "found it quite easy to produce a set of (seemingly innocuous) control, power, and trim inputs that would lead to the outcome that [he] experienced," such that "any sufficiently experienced B737 pilot could probably easily replicate the same, with a little imagination."
In other words, a go-around results in a fatal impact at a 40º nose-down angle with increasing airspeed at zero thrust because of control, power and trim inputs. That's a pretty alarming scenario because I can not imagine what those "inputs" from a "sufficiently experienced B737 pilot" might be. I think we need to be told a bit more about that, because this seems to be a very implausible narrative, just on the face of it.
Strange things do happen; there have been other crashes that require reading the final report to understand how they could have happened, when that was because of very strange control inputs on the part of the crew. (That Colgan crash near Buffalo is probably the worst example of that, when even the accident investigators had no real answer to why the crew flew the airplane as they did, when their strange control inputs caused the crash.) Here we have an equally strange scenario being presented in a veiled manner, out of fairness to the official inquiry (?). Okay, if you say so!
Another thing: I doubt that professional accident investigators pay very much attention to posts made here, but non-pilot members of the public, and some reporters too, probably do read these posts.
I just watched that clip from the sim reenactment, linked above and mentioned below, and found it completely uninformative. We need to be able to read the instruments, see the pitch trim settings, and see the PF control inputs in order to understand what we are being shown there, other than "a crash." What is the point of making such a video as that one?
Last edited by chuks; 10th Apr 2016 at 04:43.
Is it typical for pilots to move the controls (as evident in the simulator video) this vigorously in all sorts of directions when manually flying? Coming from the helicopter world, where small deliberate control inputs are the norm, the erratic nature of the controls movement in that sim flying comes as a complete surprise.
Chuks, you're doing a pretty good job of misreading OKC's post.
1. Yoke/yolk. Could be a typo, could be an auto-correct problem, could be that he really didn't know the spelling is different. You know that many pilots aren't the most educated bunch don't you?
2. He is not saying that any experienced 737 pilot could get themselves into the situation he described, he's saying that they could figure the situation out easily enough so he doesn't need to spell out the details of what he did. Presumably he used nose-down trim to help with an aggressive level out (light weight, low level, high power) with full power and then pulled the power back to keep the speed under control resulting in a grossly out of trim aircraft.
3. He also said that he deliberately did not trim to fix the problem because he was trying to replicate the mistake a tired crew may have made.
4. I agree that the concept of not saying exactly what he did so as not to compromise the investigation is just bizarre. But you know what? I know pilots who believe the moon landings were faked. The odd bizarre idea someone has does not necessarily negate the thrust of what they're saying.
1. Yoke/yolk. Could be a typo, could be an auto-correct problem, could be that he really didn't know the spelling is different. You know that many pilots aren't the most educated bunch don't you?
2. He is not saying that any experienced 737 pilot could get themselves into the situation he described, he's saying that they could figure the situation out easily enough so he doesn't need to spell out the details of what he did. Presumably he used nose-down trim to help with an aggressive level out (light weight, low level, high power) with full power and then pulled the power back to keep the speed under control resulting in a grossly out of trim aircraft.
3. He also said that he deliberately did not trim to fix the problem because he was trying to replicate the mistake a tired crew may have made.
4. I agree that the concept of not saying exactly what he did so as not to compromise the investigation is just bizarre. But you know what? I know pilots who believe the moon landings were faked. The odd bizarre idea someone has does not necessarily negate the thrust of what they're saying.
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Chucks, I was reading your comment where you ask, who trims down during goaround and why.
You have to realize, that the power has a huge influence on pitch.
I think what happened is quite simple. They added a lot of power during the goaround. It is normal and expected. Than the nose goes up a lot during the power application. So you have to push a lot to keep the nose at 15 degrees or to get it down to this 15 degrees, in case you slept through it. Next think you are leveling out very rapidly, because you had set up your goaround altitude low or started the goaround from an intermediate altitude. Than you need to power back a lot. You are trimmed for nose down due to trying to keep the pitch at 15 with a lot of power and all of a sudden your nose dips down due to power coming rapidly off in order to level out. Add to it the chronique inability of airline pilots to scan instruments coupled with tiredness, somatographic illusion and being behind the aircraft due to a lack of training as was mentioned in previous post.
I think we will see many of such accidents in the future. With the lack of training airline pilots are becoming like a sheep with no survival instincts. They cannot think one step ahead of the aircraft. Everything is a surprise to them.
And doing the 2 previous goarounds fine, while on autopilot and the last one badly because of manual flying... what is so difficult to understand it went wrong? High energy goaround keeps killing pilots with lack of instrument scanning ability, period.
You have to realize, that the power has a huge influence on pitch.
I think what happened is quite simple. They added a lot of power during the goaround. It is normal and expected. Than the nose goes up a lot during the power application. So you have to push a lot to keep the nose at 15 degrees or to get it down to this 15 degrees, in case you slept through it. Next think you are leveling out very rapidly, because you had set up your goaround altitude low or started the goaround from an intermediate altitude. Than you need to power back a lot. You are trimmed for nose down due to trying to keep the pitch at 15 with a lot of power and all of a sudden your nose dips down due to power coming rapidly off in order to level out. Add to it the chronique inability of airline pilots to scan instruments coupled with tiredness, somatographic illusion and being behind the aircraft due to a lack of training as was mentioned in previous post.
I think we will see many of such accidents in the future. With the lack of training airline pilots are becoming like a sheep with no survival instincts. They cannot think one step ahead of the aircraft. Everything is a surprise to them.
And doing the 2 previous goarounds fine, while on autopilot and the last one badly because of manual flying... what is so difficult to understand it went wrong? High energy goaround keeps killing pilots with lack of instrument scanning ability, period.
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I am not misreading anything, just asking logical follow-on questions.
For one thing, the pitch trim switches are placed right there on the yoke, when it's logical that someone who has just trimmed down-down-down is now going to trim up-up-up. That's not quite the right way to fly the aircraft, no, but that's what someone might do who's over-using the trim; he's now going to use the same thing to get himself out of the mess that he had previously used to get himself into that mess.
It's completely unrealistic for OKC to tell us of a scenario where he is pulling with all his might against the trim without bothering to re-trim using switches that are right there on the yoke. Who would do that, especially given that they would have been using those same switches shortly before to re-trim the aircraft? It is not as if the PF is going to suddenly forget to use the same secondary flight control, pitch trim, that he already had been using, is it? This is not, at first glance, a realistic scenario, so that we need to be told more about how it's supposed to have come about.
Yes, you could set up your aircraft to crash by trimming full nose-down on a go-around at low altitude while also going to idle thrust, but then the first question would seem to be, why not simply correct those settings?
For one thing, the pitch trim switches are placed right there on the yoke, when it's logical that someone who has just trimmed down-down-down is now going to trim up-up-up. That's not quite the right way to fly the aircraft, no, but that's what someone might do who's over-using the trim; he's now going to use the same thing to get himself out of the mess that he had previously used to get himself into that mess.
It's completely unrealistic for OKC to tell us of a scenario where he is pulling with all his might against the trim without bothering to re-trim using switches that are right there on the yoke. Who would do that, especially given that they would have been using those same switches shortly before to re-trim the aircraft? It is not as if the PF is going to suddenly forget to use the same secondary flight control, pitch trim, that he already had been using, is it? This is not, at first glance, a realistic scenario, so that we need to be told more about how it's supposed to have come about.
Yes, you could set up your aircraft to crash by trimming full nose-down on a go-around at low altitude while also going to idle thrust, but then the first question would seem to be, why not simply correct those settings?
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For all those scratching their heads about how OKC - and the YouTube video - got the aircraft into that nose down attitude, where even full back stick was ineffective:
Have another look at that YouTube video. Make sure you have the sound on. There is a certain sound that starts at 0:39 and only ceases at 0:50.
That sound explains everything - and could very likely be exactly what also happened on FZ981. If you don't know the significance of it, you probably should be doing a little less posting and a little more reading.
There was no stall. The autopilot disconnects upon TOGA - when single channel - which is SOP for FlyDubai. This has been brought up many times in this thread.
FFS, chuks, forget how the poster spells that word. He is referring to the control column. With enough AND trim, you can pull the CC to its rear stop with no apparent effect on the flight path. You should know this.
Something you don't appear to appreciate about human behaviour, chuks, is that when under extreme stress, humans don't necessarily respond the way they would when calm.
AtomKraft, excellent post!
Have another look at that YouTube video. Make sure you have the sound on. There is a certain sound that starts at 0:39 and only ceases at 0:50.
That sound explains everything - and could very likely be exactly what also happened on FZ981. If you don't know the significance of it, you probably should be doing a little less posting and a little more reading.
The way I read this video (it is very blurry so it is only my best guess) - he is overpowering the autopilot making it disconnect ... which ends with a stall
For me it starts with this "yolk/yoke" business
Too, you are pulling with all your might against the pitch trim, without bothering to operate the pitch trim switch which is right there on the yoke? That should be reflex, I would think.
AtomKraft, excellent post!
Last edited by FGD135; 10th Apr 2016 at 05:41.
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The autopilot disconnects upon TOGA - when single channel
Last edited by olasek; 10th Apr 2016 at 05:51.
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If the crash cause is a wrong THS setting and subsequent incorrect reaction to its effect (elevator only withount readjusting the THS) then they must include fatigue as the main cause of the disaster, as it is the only thing that explains such a succession of mistakes in a pair of otherwise competent pilots.