Kind of weird, there historically have been similar 'do it the old school way because its more reliable' fallbacks for other things in air transport. What happened to the planes that were mid flight when this bug occurred?
Right, but what I mean is that it shouldn’t be possible to skip those steps and have things coincidentally work because of the state the plane was left in. I’m not a pilot or even much of an aviation geek, so maybe I’m misunderstanding the description of this incident, but it sounds to me like this crew did what they always do, and that normally works fine, but this time it didn’t.
Wait, are you saying that the aircraft actually exhibited the same failure in the prior flight but the pilot overrode it, and then they let it take off again without warning the new pilots?
I think it's worth reporting on because this particular issue is known to everyone... you need to cycle the power on the planes every 3 days or else the reset themselves. it's crazy that a modern plane needs to have that happen but it does. the most likely situation is that the plane didn't get shutdown and happened to occur at a level flying situation and the pilots probably freaked out and overflew the plane which got it into upset territory. the plane was trimmed and would have been fine if the pilots(likely) didn't do what they did.
"- A component of the main electric trim system became inoperative. Our pilots ran the appropriate checklist, which included manually trimming the aircraft. They returned to MIA and landed uneventfully. The issue was not related to MCAS."
Indeed. This was a part failing on an aircraft in flight. It landed without incident, and was likely never in any sort of danger. Losing electric trim is an annoyance but also trims safety margins by, as I understand it, making autopilot impossible. So, it's good that they returned.
If this had happened on a 767 or A320 we'd never have heard about it.
One wonders, when the prior flight landed with the stab trim system switched off, who switched it back on before the next departure? And was there no question raised as to why it was off?
It's not normal to have that system switched off at any time. There are even guards over the switches to ensure they are only operated deliberately.
"...if the pilots turned the switch off, turning off much more than just the MCAS (as there's no switch "just turn MCAS off, keep the rest on"), but then the plane was already not possible to save (it was only 1000 ft above the ground!) and they turned the switch back on, hoping for obtaining more power/possibility to trim, and the faulty MCAS kicked in again (despite being the reason for the switch cutoff before) and even sped up the crash, then the pilots in fact did absolutely all that was possible to do..."
If this is indeed what is announced, I sincerely hope the responsible parties for making the decision to go through with MCAS in this way are paid well in jail time.
ET302’s crew (the second Max crash) also knew about the plane’s fault mode and almost saved the craft. If they’d have continued to command nose-down manually [after correctly executing the runaway trim disable checklist memory items and then re-enabling the power to the offending system in order to command aircraft-nose-down trim for a short time], they’d have almost surely flown the airplane back to base.
It was Boeing’s fault, but the crew almost saved it and inexplicably re-enabled the fault after correcting it. They were so close…
That would be the autopilot disconnect button or, in this case, the trim switch, the pressing of which is the correct immediate response to this occurrence, followed by the disabling of the system using switches on the center pedestal. While it's certainly hazardous for Boeing to knowingly expose pilots to this occurrence, I'm also conflicted by the fact that they failed to respond properly. The procedure is similar on Boeing, Airbus, Embraer and Bombardier aircraft. Standardized, in a way.
> Turning it off with the STAB TRIM CUTOFF switch turned it off.
> The pilots in the second crash did not follow that procedure.
"At 05:40:35, the First-Officer called out 'stab trim cut-out' two times. Captain agreed and First-Officer confirmed stab trim cut-out."[1]
However they were unable to correct the trim of the aircraft without help of the electrical systems (still being on full takeoff power didn't help).
So around 3 minutes later stab trim cutout was switched back to normal. Pretty much the moment they did that the aircraft pitched down hard, the situation becoming unrecoverable within seconds, followed by the aircraft impacting the ground.
There were possibly ways to save the aircraft (reduce aerodynamic forces that prevented trim by hand by, for instance, reducing thrust), but those weren't detailed in any ADs.
Mid-flight, "Hi, this is the captain. We're terribly sorry, but the plane will now be going into a 5 hour reboot mode. We flew through a rain cloud in the sun. Do not be alarmed when the lights turn off and the engines cease."
Your speculative scenario has actually happened, but on a significantly less computerized Boeing 737, in 1978.[1]
In that case, the aircraft touched down, reversers were deployed, a runway obstacle (a snowplow) appeared, and the pilots attempted to go around. They got airborne and cleared the obstacle, but as they lifted off, the "squat switches" on the main gear opened. One of the reversers was still deployed, and with the squat switches open, was no longer powered, and could not retract. The aircraft was uncontrollable, and crashed.
In that case, shutting down the reversed engine would likely have been preferable, although if we're doing counter-factuals, telling the snowplow driver about the airplane's revised arrival time is your go-to move, I think.
I recall an "Aviation Disasters" episode where the cause was the pilot was interrupted during his takeoff checklist, and skipped setting the flaps to takeoff position.
- I’ve just taken off, and am going through the after take off checklist: Set the airspeed, power, climb rate, heading, talking to ATC, planning the next stage of the flight
- Perhaps I’ve just raised the flaps and the plane starts behaving erratically
- My first / immediate thought is that my previous action led to an undesired aircraft state.
- I work from that point on
- I touch the electronic trim as habit, which resets the system briefly, and all seems well for a few seconds. I don’t know that the system reset itself.
- It goes all weird again all on its own
- Now I’m even more confused
Etc
Edit: I'm a low time private pilot flying a LSA, I genuinely don't know the procedures or processes in place for a 737, but I can empathise with their situation as I know how quickly things can go start going amiss in a plane.
Does it really help so if the procedure is the same but the critical element, the cut-off switch changed function? I'd say no, in that case procedure had changed. If it would have just been some kind of human error, like Air France 447, it wouldn't have grounded the whole fleet for the time being.
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