FZ981 -- 61 die; plane explodes after crashing at high speed on landing

[HJ1an]

Btw, here's another 737 accident in highly similar circumstances.. landing attempt, TOGA, near-vertical dive into ground, going by past occurances. Of course, it may be entirely different scenario in this one, but one can't help notice the similarities.. even the peak alt of 700 meters (according to the report, or 2296 feet) is almost similar.

*Update, it was half of the FlyDubai peak alt (4000+ft). I remembered wrong.


https://en.wikipedia.org/wiki/Tatarstan_Airlines_Flight_363

[KL-666]

I'm curious if there are any such lessons for pilots to NOT take over the AP during such scenarios

This is an impossible proposition. Autopilots disconnect themselves for tons of reasons in any phase of the flight. Roughly speaking one can say that they do when they have diverted too much from the planned trajectory. Then the pilot should get the plane back on track and from there on try the autopilot again.

In this supposed high energy climb the autopilot could have easily busted the target altitude, even with full trim down. A perfect moment to tell the pilot: i lost it, you fix it.

As long as autopilots mishandle planned trajectories, pilots must be able to fly every phase of the flight in any circumstance. Whether they choose it themselves or the autopilot forces them to by quitting.

Kind regards, Vincent

[HJ1an]

So you're saying that if the AP cuts out at whatever trim it's using - it'd just give it back to the pilot as is, and the pilot is expected to retrim, stabilize, and whatever else the aircraft, at an awkward position that the plane is in? And if it's too close to the ground and the pilots can't quite catch it quickly enough, then "tough luck" ?

[KL-666]

That's how it works and there is not much that can be done. An autopilot can not decide whether it is safe to fly a 1000 feet too high for a while. So it hands over to someone that can make such decisions.

[edit]
Neither is it possible to predict any trim setting that is convenient for the pilot. As a matter of fact, any other trim setting than it is in at the moment of handing over can bring the plane in a very dangerous position.
[/edit]

Your description of being surprised about the configuration the autopilot has left you in is incorrect. At airlines where flying is taken seriously, it is mandatory that at least one of the pilots "flies" with the autopilot, monitoring it's every move. And by not intervening he is agreeing with the moves of the autopilot as if he does it himself. No surprise possible at such airline.

On the other hand there are airlines that allow their pilots to flick on the autopilot and go doing other things themselves. Such pilots (if you can even call them that) can get caught with the plane in a surprising configuration and crash. You only have to think of Turkish in Amsterdam, and there are many more. A minor defect on one of the 3 altimeters is no excuse for not monitoring. It is a pilot's job to know in what situation his plane is at all times, and to intervene immediately if the autopilot does not do as he expects.

Btw. these descriptions of different training levels at airlines are not meant to say anything about Flydubai. I do not know in what category they are.

Kind regards, Vincent

[HJ1an]

That's how it works and there is not much that can be done. An autopilot can not decide whether it is safe to fly a 1000 feet too high for a while. So it hands over to someone that can make such decisions.

[edit]
Neither is it possible to predict any trim setting that is convenient for the pilot. As a matter of fact, any other trim setting than it is in at the moment of handing over can bring the plane in a very dangerous position.
[/edit]

I've always though it would be wise for the AP to return to a more neutral setting before letting go. In FG, I have a real hard time flying in the dark in calm nights. What more in stormy weather with the AP going nuts. I know I cannot handle it, for I lack the experience (plus limited views out, and unergonomic controls(ie keyboard) . However, it doesn't make me confident in self driving machines for the future.

On the other hand there are airlines that allow their pilots to flick on the autopilot and go doing other things themselves. Such pilots (if you can even call them that) can get caught with the plane in a surprising configuration and crash. You only have to think of Turkish in Amsterdam, and there are many more. A minor defect on one of the 3 altimeters is no excuse for not monitoring. It is a pilot's job to know in what situation his plane is at all times, and to intervene immediately if the autopilot does not do as he expects.

True, but it is exactly what causes people to lapse in concentration, because they are not doing their job, or it is a redundant one when they might need to do something else , ie. radio or monitoring fuel or whatever. If both pilots are preoccupied with something else relevant to what they were doing at that very second, but the AP decides to lose it at an awkward postion also at that very second, the amount of work being thrust to these pilots to reorient their bearings would be substantial. In the case with the Turkish Airlines, I've always wonder if they could listen to the engines winding down as an indicator, or feel a obvious drag - because they are right at the front and new engines are so quiet, they completely missed it entirely until far too late - remember such scenarios take just seconds to ruin their days. Also wonder the same thing for BA 777 that had both engines fail during landing, the difference, of course, is that one they caught it in time.

[legoboyvdlp]

Meanwhile, according to Kommersant’s sources, the recorder revealed that flight FZ981 had made two attempts to land in automatic mode, and since a veering squall wind hampered the second attempt, the pilot decided to make a third approach for landing in manual mode.

One of the pilots pressed the TOGA (Take off. Go around) button and turned off the autopilot, writes the daily.

Anonymous experts Kommersant talked to believe the pilot did not manage the diving rudder and horizontal stabilizer, which steer the plane in opposite directions – down and up, respectively.

When the pilot pulled up, he put both the rudder and stabilizer in a sharp climb mode, somewhat fighter-jet style, plus enacted the TOGA regime’s retracted flaps, decreasing ascending force. As a result, the aircraft lost speed and got into the beyond-stall angle of approach. All this led to an uncontrollable dive, the experts believe.

Those "experts" don't know so much about planes. Diving rudder, indeed. Oh and, my AA949 took off like a fighter jet. So did the 757 I once took EWR-BFS. Retracted flaps, descreasing ascending force.

[HJ1an]

Those "experts" don't know so much about planes. Diving rudder, indeed. Oh and, my AA949 took off like a fighter jet. So did the 757 I once took EWR-BFS. Retracted flaps, descreasing ascending force.

Haha, "diving rudder". Sounds like a journalists' creativity. Assuming he meant trim, or he was writing a submarine article before this one. I never had a flight where it took of like a fighter jet (there wasn't a reason to , e.g. mountains in front etc). If it did, I would not be a happy customer.

From the description it's a stall, in very highly similar circumstances with the other Russian incident Tatarstan Airlines. Isn't trim a bit awkward and slow to use - both in flight sims AND real life? I don't recall seeing it used much in TV or documentaries, but the very few that I do see them using it, they pretty much had to shuffle the thing like the scroll wheel of a mouse..

[KL-666]

Monitoring is not done by subjective listening to engines or so. It is an instrument scan of the most important items on the pfd: speed, horizon, altitude and vertical speed. If any of these change in an unexpected way then something is wrong, and it should alert the pilot to take action. Other items are looked at too, but they are not so important as these 4 parameters.

The pilot responsible for scanning can do other things like handling a checklist with the other pilot. But he can never let himself get preoccupied with something else. His preoccupation is scanning. The sequence for him is: scan, flick a switch, scan, flick another switch, scan, etc... This is adequate enough to detect any anomalies in the trajectory in time. Where it goes wrong is that some pilots think they can work through something like a whole checklist without scanning once. Then a problem can develop for over a minute and longer. If only the Turkish pilots had done their job and scan, they would have immediately noticed the unexpected decay in airspeed and the unusual pitch up, instead of letting it develop unnoticed for over a minute.

The trim wheel is (almost) never used. There is a switch on the yoke to drive that thing electrically. When used, the trim wheel starts to spin and make a loud clicking/rattling noise. So when the autopilot uses excessive trim, you will notice that immediately too. There is no issue with electrical trim being slow. If you watch the trim wheel spinning you can see how fast it is.

Trim usage during take off:
https://www.youtube.com/watch?v=-X01uY0bJs0

The leaks from the investigation are contradicting now. The first suggests a high energy climb and the second a stall (low energy). Though FR24 data is very unreliable in detail, it can point to a general tendency. It's data points to high energy climb. All in all there is not enough information and the wording of the articles does not make them sound very credible either. In a few weeks there will be some official data the investigators have said.

Kind regards, Vincent

[jwocky]

Wouldn't the h-stabs be quite up for that climb? They say, they were trimmed full down, so how could the plane climb that steep with trim full down?

[HJ1an]

Wouldn't the h-stabs be quite up for that climb? They say, they were trimmed full down, so how could the plane climb that steep with trim full down?

The assumption was that the plane was extremely lightweight - with only 61 people on board and very low on fuel, with under wing engines configuration, a TOGA at nearly full power would create an extremely steep nose up climb by how the plane was designed alone and that the AP would have to compensate by trimming it downwards, probably fully.

At least, that's my understanding of it.