The pilots turned off the autopilot for takeoff due to a known bug.
Flying manually the pilots made an error when setting the required
thrust that nearly caused the plane to run off the runway without
getting off the ground?
Is that correct?
In which case it seems like pilot error.
Not an expert, but it seems very clear to me that autothrottle is not intended to disengage when you press the takeoff/go around button. The whole point of that button is that you press it when you need to take off or go around and the plane attempts to set itself to a configuration where as long as you point the nose in the right direction then that should happen.
But it does rather sound like it was an expected behaviour. The system has a history of nuisance disconnects, the manufacturer recommends that you reject takeoff when that happens, and for some reason instead of doing that, the crew reacted to the disconnect warning by pressing the button again and, at that point, trusting that it was engaged and working. My reading of that is that the plane regularly has an A/T fault that can be fixed by simply pressing the button again, so this crew has developed a habit of doing that, but this time it was a different fault with different behaviour that their usual fix didn't work for, and they just failed to notice.
The report is clearly limiting itself to describing the difference between what actually happened and what the procedures say should happen, rather than speculating about what the pilots were thinking, but that's the only way it makes sense to this very much not expert that you shouldn't pay too much attention to.
> As a reminder, Turkish Airlines flight 1951 crashed in 2009 due to a faulty radio altimeter which set the autothrottle to idle before they touched down.
Was it due to interference? Otherwise this seems specious.
I don’t think we have enough information to make that statement yet. Could be they forgot to set flaps, could be they miscalculated TO speeds, could be they misconfigured auto throttle...
As usual, need to wait for investigation and report.
Where's the "autothrottle" in the EAD you quote? From the article we all comment:
"Jacobsen points out that the FAA’s emergency directive after the Lion Air crash lists the procedure pilots should follow — but omits the instruction on the autothrottle and fails to mention that it could malfunction."
The way I understand it, that's the new information in the article to which you respond with quoting... exactly the very EAD which obviously lacks any mention of it, confirming the claims from the article.
Well, the autopilot was disabled, and the flight director (which at a 1 sentence level is a visual indication of what the autopilot would do) was trying to keep the plane level at the configured altitude
The flight director did the right thing — displayed how it would manage level flight
The pilot did the wrong thing - copied the misconfigured flight director instead of flying the plane
> The fly-by-wire system malfunctioned and the pilots got confused.
The Wikipedia summary of the investigation report sounds quite a bit different.
It says there was an intermittent malfunction that could be cleared by following a procedure, which was done three times during the flight, with no impact on flight safety (AIUI). The fourth time, instead of following procedure, the pilot toggled the flight computer's circuit breaker, which he is not allowed to do in flight, which reset the flight computer completely, disabling various automated systems that they would now have to re-start, which they did not do. Then the plane entered a stall and due to communication issues pilot and co-pilot gave contradictory control inputs which resulted in no control input to the plane.
> Airspeed dropping while the autopilot tries to maintain altitude is another. This can result in a stall and complete loss of control under the wrong circumstances.
This happened to me in X-Plane (sim) the first time I used autopilot. I had dialled in a rate of climb the plane couldn't maintain. Very hard to recover from a stall when the elevator trim is set fully nose up.
1. The pitot tubes froze (this was already a known possibility) and this particular plane was scheduled to replace those tubes;
2. When the speed metrics became unreliable, system didn't do anything uncommanded, disengaged autopilot gracefully, notified the pilots and handed control over to them;
3. Stall warnings went off and one of the pilots continued to pull on the stick (this baffled other pilots I heard speak about this too because this is the exact opposite thing to do during a stall)
4. It's clear from their exchanges in the cockpit that this particular pilot was very nervous during the whole thing.
What's complicated about that? I can't see how a computerised system could have helped here. Computer had no reliable grounds to make a decision and it did exactly what it should and what should have neen expected by the pilots at the time.
"The pilot of Flight 610 appears to have [pressed that switch] repeatedly to bring the nose up, but the MCAS reactivated each time, as it was designed to do, forcing the nose back down, and the pilot had to repeat the process again and again."
This is getting quite wierd. The captain had 6000 hours of experience, the pilots knew what the problem was, they had ten minutes to solve it, and they had started to do the right things. All good so far. Then, something went wrong. But what?
> So, not much information why the computers sent conflicting commands and also why the engines power down in such a situation.
I think shutting down the engines is probably the safest option when this sort of thing happens. You could argue they should stay in the present setting, but what would happen if one engine were at 0% and another 100%?
Most aircraft are pretty good at gliding even without power, and I'd assume a deadstick landing is part of the pilots training. In 2001, TS236 flew unpowered for 19 minutes before making an emergency landing (on a runway) with only minor injuries:
> The purpose of a single button would be to put the plane in a known, easy to reason about state, even if it's not the most stable or the easier one to fly.
The "known" is the problem there. The pilots there were continuously misinformed about the plane speed due to that iced measurement devices. That is what plane "knew" and what the pilots "knew" in the storm.
The autopilot handed over control to human, but then human drove it too high (the "law" here means "mode of operation"):
"The pilot continued making nose-up inputs. The trimmable horizontal stabilizer (THS) moved from three to 13 degrees nose-up in about one minute, and remained in that latter position until the end of the flight."
"A second consequence of the reconfiguration into alternate law was that stall protection no longer operated. Whereas in normal law, the aircraft's flight management computers would have acted to prevent such a high angle of attack, in alternate law this did not happen. (Indeed, the switch into alternate law occurred precisely because the computers, denied reliable speed data, were no longer able to provide such protection—nor many of the other functions expected of normal law).[55] The wings lost lift and the aircraft stalled"
> one of them (the co-pilot, IIRC) didn't realize it
But the co-pilot definitely knew that the autopilot disengaged:
"The first officer, co-pilot in right seat, 32-year-old Pierre-Cédric Bonin"
"At 02:10:05 UTC the autopilot disengaged" ... "As pilot flying, Bonin took control of the aircraft via the side stick priority button and said, "I have the controls.""
"On 5 November 2014, Lufthansa Flight 1829, an Airbus A321 was flying from Bilbao to Munich when the aircraft, while on autopilot, lowered the nose into a descent reaching 4000 fpm. The uncommanded pitch-down was caused by two angle of attack sensors that were jammed in their positions, causing the fly by wire protection to believe the aircraft entered a stall while it climbed through FL310. The Alpha Protection activated, forcing the aircraft to pitch down, which could not be corrected even by full stick input. The crew disconnected the related Air Data Units and were able to recover the aircraft."
1. Zig Zaging flight path between legitimate waypoints after transponders were turned off, plus some pronounced altitude changes suggest that Autopilot was not engaged.
2. Pilots turned off transponders before their last communication.
A) The autothrottle disengaged due to the bug, and the throttle defaulted back to some previously set value, without the pilots knowledge.
B) The pilots disabled the autothrottle to avoid a bug, and also failed to set the throttle correctly.
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