Preliminary report into Air India crash released

You have to pull the switches out (against a spring) to be able to move them over a notch and flip them. Not really something you can just mistake for another switch or bump into by accident.

I'd liken it to turning off the ignition by turning the key while driving your car. Possibly something that could happen if you're really fatigued, but requires quite a mental lapse.

Report says the switches went to cutoff one second apart from each other. Can a human do the physical operation on two switches that quickly?

There's a good photo of them here; https://theaircurrent.com/aviation-safety/ai171-investigatio...

You can do them both with one hand.

The timing is really curious.

08:08:35 Vr

08:08:39 Liftoff

08:08:42 Engine 1 cut-off

08:08:42 Engine 2 cut-off

08:08:47 minimum idel speed reached

?? One pilot to other: why cut-off. Other: Did not do it

08:08:52 Engine 1 run

08:08:52 Engine 2 run

1 second to switch them both off and then 4 seconds to switch them both on. No one admitted to switch them off. They are probably going with fine comb over the audio and also the remains of the chared switches.

Looks like the engines react very quickly to cut-off so it is not clear whether the question about the cut-off is prompted by a glance to the switches or the feel of the airplane.

The big question is whether the switches were moved or something made it seem as if the switches were moved.

Are you completely sure you can considering that they are spring loaded and they are like 7-10cm apart judging by the size of other controls?

Well in the murder-suicide scenario it makes sense for the culprit to turn them off as quickly as possible. The longer time to turn them on could plausibly be a struggle or simply needing to fly the plane while reaching for each switch individually.

I don't understand your question. I have done this myself, am I completely sure?

If you do them both with one hand, would they not be moved at the same instant rather than 1 second apart?

They require a per-switch motion, so unlikely.

Did you mean to say you can activate the switches with one hand simultaneously? That is probably what the above commenter assumed you meant. Since lifting and twisting two switches simultaneously with one hand seems challenging.

It didn't happen simultaneously so this is irrelevant.

It is relevant to the interaction I replied to.

Above commenter said _quickly_, not simultaneously

Is there just one set of switches? Or do both pilots have their own set?

Is it possible to rest the switch on the notch? Does the switch make contact if the switch is in the RUN position but the switch is not completely down?

That is, is it possible they flipped the switches over to RUN but did not seat the switches properly, and instead leaving them on top of the notch, with later vibration causing the switches to disengage?

Just trying to think of some semi-plausible non-active causes.

Assuming the person trying to kill themselves and a plane load of people would respond in an expected way to inquiry is also just a mistake.

It's not a rational decision, so there's no reason to expect rational decision making or explanation on the output.

You’re the only one who said “simultaneously.”

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 operation.]

snypher: I am confused by the response.

Me: [Tries to facilitate clarification]

See above.

> This is ambiguous and could be read as "one hand, simultaneously"

Not within the context of the thread.

Context is both these switches being turned off with a 1 second gap. Doing it with one hand simultaneously would possibly explain it, otherwise it doesn’t seem relevant.

Only one set.

> Looks like the engines react very quickly to cut-off so it is not clear whether the question about the cut-off is prompted by a glance to the switches or the feel of the airplane.

The workload is pretty high during the takeoff phase. The engines react right away when fuel flow is stopped. The engine displays can have some lag before data is updated.

Relighting an engine at low speed is not feasible - most need 230-250kts IAS before attempting the operation. Maybe you could do it if the APU was still running and could provide compressed air, but it takes about 20-30 seconds to start up amd then probably 5-10 more to spool up to full thrust. I am speculating here a bit, but the pilot did not have enough time to save the plane even if he did everyting right and as fast as humanly possible.

All this aside is overshadowed by the limited amount of time the pilot flying (I would assume the captain in this case since there was only one ATPL pilot in the cockpit) had to troubleshoot the issue of a dual engine failure - as this is what would have felt to him - during takeoff.

I wonder if they could theoretically rest on top of the notch, not fully locked into either position and flip accidentally. No idea how the switches behave when not all the way up or down, but the notch looks pretty long and flat so it could be possible.

Those switches are the size of a thumb. No one is moving those - separately, mind you - and not realize what is going on.

Too many are willing to accept the Bart Simpson excuse of "I didn't do it" at face value.

Something like this could maybe happen to one switch, it's unlikely but possible. But two independent switches at the same time?

Good point, that is very unlikely. I was just wondering if it's possible at all.

> I would assume the captain

The report states the FO was pilot flying.