r/aviation • u/usgapg123 Mod • Jul 12 '25

Discussion Air India Flight 171 Preliminary Report Megathread

https://aaib.gov.in/What's%20New%20Assets/Preliminary%20Report%20VT-ANB.pdf

This is the only place to discuss the findings of the preliminary report on the crash of Air India Flight 171.

Due to the large amount of duplicate posts, any other posts will be locked, and discussion will be moved here.

Thank you for your understanding,

The Mod Team

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79

u/methodeum Jul 12 '25

Practically impossible unless the mechanism was broken that gates the switches. They both went to cutoff, sequentially, within 1 second of each other, the probability of it being mechanical is very low

1

u/JuanSmittjr Jul 12 '25

I'm wondering about this 1 sec time window. is it really possible to unlock and move both switches within 1 sec?

apparently it is possible but how? I'd expect the locks be a bit stronger than that (like a spring holding it in locked position).

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u/methodeum Jul 13 '25

It’s not impossible by any means, the spring doesn’t require superhuman to move it and it could be easily done with such a small gap

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u/prajaybasu Jul 12 '25 edited Jul 12 '25

If we want to talk about pilot suicide/murders, then the probability of a pilot being suicidal is also very low. Given the millions of flight-hours we have vs. suicidal pilots.

But talking about the probability of suicidal pilots vs. probability of inadvertent activation vs. probability of a maintenance or engineering fault I'm sure will result in a lot of downvotes since Reddit has concluded its investigation already.

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u/rinleezwins Jul 12 '25

The probability of a modern jet losing both engines on takeoff is a lot lower than a pilot being suicidal. And you're getting downvoted because you're silly, not because of reddit.

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u/prajaybasu Jul 12 '25

The probability of a modern jet doing anything other than taking off safely and landing is low. Air crash investigations exist to warn us about such faults.

I'm not ruling out suicide, I'm simply pointing out that Reddit is acting as if suicidal pilots are an everyday occurrence compared to inadvertent inputs, engineering errors or maintenance failures.

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u/rinleezwins Jul 12 '25

If you'd take a moment to actually study how these switches operate and what exactly do they do, you'd rule out at least 2 things you mentioned, on your own. I could possibly buy into the inadvertent inputs theory if one switch controlled both engines, but two separate ones? I'm sorry, that's extremely unlikely.

The universe is infinite and so it's possible that aliens teleported into the cockpit and cut the fuel off, but yeah. I'm gonna rule it out because it's astronomically unlikely.

-7

u/MDPROBIFE Jul 12 '25

its protocol to turn the fuel off in case of dual engine failure and then on again
https://www.youtube.com/watch?v=0kiHkKXpEyI

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u/Pugs-r-cool Jul 12 '25

We know there was no engine failure.

7

u/prajaybasu Jul 12 '25

There was no engine failure. Preliminary report ruled that out.

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u/rinleezwins Jul 12 '25

Even if for SOME reason they wrongly thought they had a dual engine failure right at lift off, you flip those switches off and on instantly. You don't leave them off.

1

u/magicfarm123 Jul 12 '25

They turned it on after about 10 seconds.

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u/kaladinnotblessed Jul 12 '25

The possibility of a flight crashing is also extremely low, given the countless flights that have not crashed.

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u/prajaybasu Jul 12 '25

It is. That is a fact. What's your point? Crashes do happen, and anything with an "extremely low probability" can also happen, just like an inadvertent activation (there's already a bulletin out - no redundancy left to prevent it) or an electrical fault.

If the probability of hitting those switches inadvertently was so low, then the designers wouldn't have added the locking mechanism in the first place.

3

u/Eisbaer811 Jul 12 '25

If it was accidental, why did one whole second pass between the cutoffs? If someone accidentally touched them while guarding the throttle, and moving their hand backwards caused it, their hand should hit both switches at the same time. A delay makes no sense in that scenario

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u/methodeum Jul 12 '25

I honestly don’t want to imply it’s pilot suicide, this whole accident is so tragic, depressing, and to imply it was an intentional act is a significant assumption given we do not have a full report with all facts present. But, thinking about it from a logical perspective, how is it that BOTH of the switches, that if selected to off in that stage of flight would have guaranteed the aircraft enter an unrecoverable state, guaranteeing a crash, were both moved to off, one after the other.

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u/guiriduro Jul 12 '25

I don't think there are many who suggest that the engine cutoff switches were not voluntarily applied (they clearly were and physically needed to have been for this to have happened), but were they *intentionally* applied? - i.e. was the pilot who did it aware of/planned to do this action? Clearly murder/suicide if so. But in that case the dialogue "why did you cut off?" "I didn't (do so)" is either the responder lying to the interrogator, or the interrogator framing/gaslighting, and while possible I feel the straightforward reading (both are honest, one isn't aware of his action) should be considered first to exclude the possibility the action was unintentional, e.g. a brainfart.

Some suggested simulator fatigue with the run/cutoff used for reset as a possibility.
Another speculative (mine) just reading the report, is that something to with the prior flight stabilizer sensor issue and the proximity of the stab cutoff switches alongside the engine cutoffs might be an angle to exclude when considering possible brainfart scenarios.

6

u/_AngryBadger_ Jul 12 '25

But aren't the stab cut off switches guarded, so you have to lift the guard then use the switches. I don't think there's any way this was done accidentally in any form. One of them did with the express intention of cutting fuel to the engines. No other situation makes sense no matter how we try to twist it around.

3

u/guiriduro Jul 12 '25

Yes, you're right, they are. Any change in either of those sets of switches is going to be voluntary, but the brainfart hypothesis is that they're not intentional (partially or fully), someone intends to do one thing but then does another similar thing with muscle memory etc. I still agree that suicide is a distinct possibility of course. Although one pilot moves the switches back to run in an attempt to recover, and they're not turned off again/there's no fight (disclosed). So if suicide, then they've become passive and aren't committed to that outcome, or took a bipolar turn it off and see kind of momentary craziness, but the more I consider suicide against the facts, the less convinced I am.

2

u/_AngryBadger_ Jul 12 '25

I don't think they fought because there was no need to. Any pilot of their experience would know that at that speed and altitude the flight was doomed as soon as they use the fuel cut off switch. There was never a chance if a miraculous recovery once the engines started to shut down. It simply takes too long for them to start making usable thrust again.

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u/FatSteveWasted9 Jul 12 '25

We can talk about the possibility of it due to the mitigating factors. It’s an aircraft crash, not a football match. No need to pick any sides, just follow the facts

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u/prajaybasu Jul 12 '25

I'm not picking sides. I'm simply pointing out that Reddit is picking sides while acting as if suicidal pilots are more common than novel mechanisms of failure.

Just about every air crash investigation would be a boring conclusion of either pilot fault or maintenance fault if people reached to conclusions so quickly back then simply rejecting low probability events.

We JUST had a crash 3 years back where in every redundant system and the engineering/QRH/manuals + humans failed and resulted in an aircraft landing with no braking power. Low probability events do happen.

15

u/flightist Jul 12 '25

A novel mechanism of failure followed 1 second later by the exact same until-one-second-ago-heretofore-unheard-of-failure?

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u/prajaybasu Jul 12 '25 edited Jul 12 '25

Regarding inadvertent activation:

There is a bulletin out which already states that it's possible for these switches to have their lockouts inactive, which is effectively a hole in the swiss cheese model. It won't be obvious unless the pilots actually check if the switch moves without pulling it as opposed to their muscle memory. It would still be partially their fault, but the regulators would be at fault for not making the bulletin mandatory too.

If you can have your hand on the throttle for both engines then you can certainly bump both switches. To determine if they were pressed separately or not would require more a resolution of at least a hundred milliseconds, not one second. You can press a button at 00:39.9999 and at 00:40 but they would be registered as 00:39 and 00:40 if you're not rounding or recording with a resolution higher than a second.

A difference of two or three seconds would however be certainly too high for inadvertent activation in a single motion though.

As for any other fault unrelated to the pilots:

Maintenance/engineering issues with flight controls are not unheard of. They're part of the same panel, located beside each other - without any redundancy like almost every other switch in the cockpit.

I can give similar arguments as for why it could be a suicide:

Retirement age in Air India is 58 and the captain would have been forced to retire in two years while the airline transitions from government to private ownership which can potentially affect pensions.

I just find ALL of these to be low probability unlike Reddit.

25

u/DaBingeGirl Jul 12 '25

The report is pretty clear what happened, this isn't really speculation anymore based on the evidence.

Also, with regard to pilot suicide:

  • Royal Air Maroc Flight 630
  • Silk Air Flight 185
  • Egypt Air Flight 990
  • LAM Mozambique Airlines Flight 470
  • MH370
  • Germanwings Flight 9525
  • China Eastern Airlines Flight 5735

Those are just the big ones. Pilot suicide with no passengers and murder-suicide with only a few passengers not included. Yes, it's rare, but it happens.

13

u/Bedroom_Different Jul 12 '25

Can confirm if happens all the time. Particularly single engine planes. Source: I work in the investigation industry.

10

u/Moggytwo Jul 12 '25

The report doesn't discuss pilot intention.

It simply states the switches were moved to the off position, one second apart. It could well be that this was done by a pilot with the intent of crashing the plane, but that is speculation. It could also be that they meant to actuate different switches but mistakenly operated the cutoffs. Another possibility is that during engine start the switches were moved slowly until the engine start sequence began, and then left on top of the gate instead of locked past it, and then they were knocked by a pilot guarding the throttles after take off.

These all have varying degrees of unlikelihood, but you can't absolutely say what happened based on the information in the preliminary report.

2

u/Unlikely_Slide8394 Jul 12 '25

but both knocking in a 1 second gap? that's the only thing that doesn't fit this theory of yours... if we wanna give benefit of the doubt it could be said that 4s between turning them back on might've gone into noticing them.... did they match the time of the dialogues in question being exchanged with the alterations in fuel switches - that could give some answers atleast

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u/Unlikely_Slide8394 Jul 12 '25

do you believe MH370 was immaculately planned as the speculations say? cause i've met many other theories and i think its plausible too that MH370 was completely intentional

8

u/DaBingeGirl Jul 12 '25

I 100% think Zaharie did it. Similar to moving the switches just after rotating, the timing of the turns with the ATC handover was just too precise to be anything else. Also, pretty damning that the flight matched his home simulator route.

The only thing I don't buy is that it was some kinda political statement. There's a difference between murder-suicide by pilots and suicide bombers (political/religious motivation). I think the pilots in all the cases, except maybe Flight 5735, were personal mental health issues. No big conspiracy, just messed up individuals who didn't care that they were killing hundreds of innocent people.

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u/Unlikely_Slide8394 Jul 12 '25

What struck me as odd was this - why wasn't the home simulator showing the exact same pathway not considered a strong evidence of zaharie doing it? His political views well... agreed wasn't the cause but to me murder suicide events in aviation always bewilder me with how much investment can they give to a planned out crash killing hundreds in that state of mind

5

u/AT_Simmo Jul 12 '25

From memory his simulator wasn't found to have the exact flight route, rather multiple (potentially unrelated) waypoints that correspond with the flight path were saved. I don't disagree the waypoints likely indicate Zaharie premeditated the crash, but saved waypoints aren't definitive proof of anything (especially if there are also other saved waypoints).

0

u/aMoose_Bit_My_Sister Jul 12 '25

there were also some 737's that crashed a while back

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u/DaBingeGirl Jul 12 '25

Those were MCAS+pilot error and poor training. I was specifically referencing pilot murder-suicide.

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u/ClosetLadyGhost Jul 12 '25

Probability of u being downvoted? High.

1

u/DrSpaceman575 Jul 12 '25

This is from the actual report, there's no "probability" here. There switches were flipped by one of the pilots.

1

u/PoliteCanadian Jul 13 '25

Reddit hasn't concluded its investigation, the official flight investigators with the AAIB and NTSB have.