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Preliminary report into Air India crash released

bbc.co.uk

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Re: Preliminary report into Air India crash released

#741

Post by twoodfin »

SAI_Peregrinus wrote: post #629

Assuming this is a murder-suicide and not a mistake or malfunction somehow, it's very damning of the FAA's policy to revoke the pilot's licenses of anyone seeking treatment for mental health issues. This was in India and thus not FAA jurisdiction, but it still would be a case where an untreated mental health issue lead to hundreds of deaths. By making pilots choose between their careers & medical treatment (since the…

For anyone who didn’t already know, this concern is a key plot point in the second season of HBO’s “comedy” series The Rehearsal.

Personally, found it simultaneously one of the greatest and most insane seasons of television ever. YMMV.

Re: Preliminary report into Air India crash released

#742

Post by efitz »

padjo wrote: post #380
efitz wrote: post #336

It’s interesting to see how many people are bending over backwards here to avoid coming to the obvious conclusion. If this was pilot suicide, it’s a terrible thing. If it was somehow an error (which seems very unlikely) or two defective controls (which seems even more unlikely), then it remains a tragedy. But I don’t need to do mental gymnastics to come up with implausible hypotheticals. This comment stream on HN is…

It’s nowhere near an obvious conclusion. A failure with the locking mechanism or muscle memory confusion are just as likely, and probably other theories I’m not thinking of. More investigation is clearly needed, which is why this is called a preliminary report.

Muscle memory? That’s grasping. How many times have you been pulling onto the highway and accidentally turned off your ignition?

I’d buy “mechanical defect” if it was only one switch. Two? At the exact same time? During takeoff? Nope.

Re: Preliminary report into Air India crash released

#743

Post by mr_toad »

dyauspitr wrote: post #160
rogerrogerr wrote: post #100

Earlier quoted context omitted.

And fuel cutoff is _two_ down motions? That's the death knell for this theory, imo.

Sometimes I drive all the way home without being aware of what I did in between.

One time I almost drove to work instead of the shopping mall, because driving to work was basically subconscious. But my car doesn’t have safety features designed to stop me doing that. And I never did it twice in a row.

Re: Preliminary report into Air India crash released

#744

Post by invalidator »

interestica wrote: post #675
WalterBright wrote: post #626

Earlier quoted context omitted.

> The computer overrode the inputs. This is incorrect. The manual stabilizer trim thumb switches override MCAS.

Are we not in agreement? MCAS overrode the inputs and the thumb switches could override MCAS?

MCAS autonomously adjusts trim downward. The trim switches override MCAS, but when released, MCAS can resume trimming down again. The trim adjustments don't "override" the pilot's elevator inputs (MCAS has no direct control over the elevators), but they can make the controls so heavy that it's impossible to pull up.

Re: Preliminary report into Air India crash released

#745

Post by oncallthrow »

ankit219 wrote: post #695
jeswin wrote: post #640

Here's another point of view: https://x.com/BDUTT/status/1944012769323626682 The four Indian pilots on her show are clearly not convinced that the pilots are to blame. As they mention, it's important to know what else was spoken in the cockpit. Quite possible that there's more, and that might have implicated the pilots. However, if that's not the case, this is a very poorly worded report.

This is BBC, they have a history of being uncharitable when it comes to reporting on their erstwhile colonies. Jumping to a conclusion about pilot's fault when the recorded dialogues show both had no idea who cut it off (leaving ground for a possibility of some malfunction) is irresponsible, especially when the report could have been worded better without needing to reach a definitive conclusion. Both pilots have a l…

Where in the BBC coverage are the pilots blamed? Sounds like you might have a bit of a chip on your shoulder, and indeed it sounds like you are the one who is biased towards a particular conclusion (namely that the Indian pilots bear no blame).

Re: Preliminary report into Air India crash released

#746

Post by cosmicgadget »

JumpCrisscross wrote: post #293
cosmicgadget wrote: post #272

Earlier quoted context omitted.

Jesus... joey: Can you switch them quickly? snypher: You can do them with one hand. [Ed. This is ambiguous and could be read as "one hand, simultaneously". In fact, doing it with one hand non-simultaneously would be a weird claim to make of a simple knob. See also ajb's comment below.] zihotki: Really? They are not close together and have a spring mechanism. [Ed. Seems to believe snypher is claiming simultaneous oper…

> This is ambiguous and could be read as "one hand, simultaneously" Not within the context of the thread.

Are you kidding? You don't understand that 'simultaneous' is <1 second?

Re: Preliminary report into Air India crash released

#747

Post by WalterBright »

interestica wrote: post #675
WalterBright wrote: post #626

Earlier quoted context omitted.

> The computer overrode the inputs. This is incorrect. The manual stabilizer trim thumb switches override MCAS.

Are we not in agreement? MCAS overrode the inputs and the thumb switches could override MCAS?

The pilot's inputs are the thumb switches, and they override MCAS.

Additionally, the stab trim cutoff switch overrode both MCAS and the thumb switches.

Using both easily and successfully averts MCAS crashes, as proven in the first incident (there were three, but only two are reported on).

Re: Preliminary report into Air India crash released

#748

Post by mr_toad »

narmiouh wrote: post #727
potamic wrote: post #471

Earlier quoted context omitted.

> On Jul 12th 2025 (UTC) India's media report that the investigation is NOT focussing on a human action causing the fuel switches to appear in the CUTOFF position, but on a system failure. Service Bulletins by Boeing issued in year 2018 recommending to upgrade the fuel switches to locked versions to prevent inadvertent flip of the switches, as well as the FAA/GE issued Service Bulletin FAA-2021-0273-0013 Attachment 2…

The one thing automatic system failure theory can't explain is whether there is a reverse connect from the machine back to the switches where if the machine decides to cut off fuel, would the physical switches toggle to cut-off or stay in run position while the fuel is actually cut off, this would require an actuator setup to flip the switches from inside the system which there is no documentation of if that is even…

Do your lights control your switches?

Re: Preliminary report into Air India crash released

#749

Post by WalterBright »

invalidator wrote: post #744
interestica wrote: post #675

Earlier quoted context omitted.

Are we not in agreement? MCAS overrode the inputs and the thumb switches could override MCAS?

MCAS autonomously adjusts trim downward. The trim switches override MCAS, but when released, MCAS can resume trimming down again. The trim adjustments don't "override" the pilot's elevator inputs (MCAS has no direct control over the elevators), but they can make the controls so heavy that it's impossible to pull up.

If MCAS is running the trim, the thumb switches override it.

MCAS affects the stabilizer, the thumb switches affect the stabilizer, the cutoff switch affects the stabilizer.

The elevators are controlled by the control column and the autopilot.

> The trim switches override MCAS, but when released, MCAS can resume trimming down again.

That is correct. That is why the procedure is to return the trim to normal with the thumb switches, then turn off the trim system. That's it. That's all there is to it.

> but they can make the controls so heavy that it's impossible to pull up.

Almost right - the trim has more authority than the elevators. The trim's ability to travel far is to provide great ability to get out of trouble. I don't really know what factors the aerodynamics guys used to calculate the max travel required. I do know there is a travel limiter on it (as I worked on that, too!) which reduces the max travel at higher speeds, because otherwise it can rip the tail section off, which is a big no-no.

There are sooo many constraints on the design of an airplane I sometimes wonder how anyone manages to make one that works at all. The Wright Bros calculated that their machine would fly, and it did, barely. Their contemporaries did seat of the pants design, which is why they failed.

Re: Preliminary report into Air India crash released

#750

Post by nelox »

yason wrote: post #672

It is known that the switches cannot effectively be flipped by accident. It is known that the switches were set to "cut-off" because they were then later restored to "run", so it was not an electrical fault (i.e. switches pointing to run but reporting cut-off). Pilot dialogue and engine telemetry confirms the cause of power loss was fuel cut-off. The question I can't help but think is how did the pilot realize it was…

Maybe the pilot who cut-off the fuel was the one who asked “why did you cut-off?”. Knowing full-well the conversation is recorded in order to fool investigators, lay blame and confuse his colleague.
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