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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

#231

Post by YetAnotherNick »

decimalenough wrote: post #11

> The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off. So the fuel supply was cut off intentionally. The swi…

Reminds me of 2017 Las Vegas shooting. The perpetrator looked and acted completely normal till the day of shooting and all his issues like anxiety or losing money was nothing far from ordinary. And what seems all of a sudden did a well planned shooting and didn't bother to leave a note or tell his story.

Re: Preliminary report into Air India crash released

#232

Post by magicalhippo »

ummonk wrote: post #22
alephnerd wrote: post #14

Earlier quoted context omitted.

> It's difficult to conclude anything other than murder-suicide. Is it possible it could have been an accident or a mistake by one of the pilots? How intention-proofed are engine cutoffs?

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.

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.

Re: Preliminary report into Air India crash released

#233

Post by WalterBright »

bgwalter wrote: post #25
decimalenough wrote: post #11

> The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off. So the fuel supply was cut off intentionally. The swi…

Does the Flight Data Recorder consider the physical position of the fuel switches or does it get the information from some fly-by-wire part that could be buggy? The conversation would suggest that the switches were in CUTOFF position, but there is also a display that summarizes the engine status. There is no conversation that mentions flipping the switch to RUN again. EDIT: Why is there no Cockpit Video Recorder? The…

I've had discussions on HN with people who insisted that having a video camera always pointed out the control tower at the runway was some sort of impossibility. Despite every 7-11 having such a system.

This would leave accident investigators with a lot of work to do to try to figure out how a collision happened.

Re: Preliminary report into Air India crash released

#234

Post by apical_dendrite »

userbinator wrote: post #193
ceejayoz wrote: post #15

Earlier quoted context omitted.

Both switches, at slightly different times? Seems pretty unlikely.

A rodent chewing on wires. Vibration-induced chafing. Tin whiskers causing an intermittent short. There are many possibilities, those came to mind first.

We know that the switches physically moved from the run to the cutoff position because one of the pilots noted that they were in the wrong position. We know that they were moved back to the run position because they found in that position. I don't understand how a short could explain that - it really seems like someone would have had to physically move the switches.

Re: Preliminary report into Air India crash released

#235

Post by TylerE »

the__alchemist wrote: post #106
mdavid626 wrote: post #45

Earlier quoted context omitted.

Well, can you move it back, when accidentally activated?

Yes, and it restarts the engines, but it takes on the order of seconds; too long at that altitude. One of the pilots did that, but it was too late.

More like 30 seconds. Just throttling an already running engine up from idle (which is quite a bit above zero throttle in most respects) takes seconds.

Re: Preliminary report into Air India crash released

#236

Post by somat »

ggreer wrote: post #126
lazystar wrote: post #44

Earlier quoted context omitted.

still, it at least shows that there's been issues with the locking mechanism in the past. inadvertently bumping something that was assumed to be locked is a simpler theory; i find it hard to believe that a murder suicider would take this route, when the china nosedive option is easier, faster, and has a higher chance of success.

The preliminary report says the switches were triggered a second apart, so it would have to have been faulty switches and two inadvertent bumps. That seems unlikely to me.

Within a second apart. If I read the report right. The time resolution of the recorder?

And yes, it does sound like it was probably intentional. I would still like to see an engineering review of the switch system. Are they normally open or normally closed, In the end the switch instructs the FADEC to cut the fuel, but where does the wiring go in the meantime? what software is in the path? would the repair done before the flight be in that area?(pilot defect report for message STABS POS XCDR), and perhaps compromised the wires?

Re: Preliminary report into Air India crash released

#237

Post by bigDinosaur »

cjbprime wrote: post #156
russdill wrote: post #124

Earlier quoted context omitted.

There is no possible way to confuse these two actions. There's a reason a wheel is attached to the gear lever.

> There is no possible way to confuse these two actions. This is obviously an overstatement. Any two regularly performed actions can be confused. Sometimes (when tired or distracted) I've walked into my bathroom intending to shave, but mistakenly brushed my teeth and left. My toothbrush and razor are not similar in function or placement.

If someone confused their steering wheel for the brake you'd probably be surprised - there are indeed errors that are essentially impossible for a competent person to make by mistake. No idea about the plane controls, though.

Re: Preliminary report into Air India crash released

#238

Post by sandspar »

cosmicgadget wrote: post #43
lazystar wrote: post #17

Earlier quoted context omitted.

https://ad.easa.europa.eu/ad/NM-18-33 well hold your horses there... from the FAA in their 2019 report linked above: > The Boeing Company (Boeing) received reports from operators of Model 737 airplanes that the fuel control switches were installed with the locking feature disengaged. The fuel control switches (or engine start switches) are installed on the control stand in the flight deck and used by the pilot to sup…

Is it easy to inadvertantly move both switches in such a scenario?

The switches are spring-loaded, notched in place, and have a rubber knob on the top. A pilot must squeeze the knob, remove the switch from its ON notch, press the switch, click it into the OFF notch, then release the knob.

Doing it accidentally is impossible.

Re: Preliminary report into Air India crash released

#239

Post by XorNot »

cosmicgadget wrote: post #61
heisenbit wrote: post #38

Earlier quoted context omitted.

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 al…

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.

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.

Re: Preliminary report into Air India crash released

#240

Post by refulgentis »

YetAnotherNick wrote: post #231
decimalenough wrote: post #11

> The aircraft achieved the maximum recorded airspeed of 180 Knots IAS at about 08:08:42 UTC and immediately thereafter, the Engine 1 and Engine 2 fuel cutoff switches transitioned from RUN to CUTOFF position one after another with a time gap of 01 sec. The Engine N1 and N2 began to decrease from their take-off values as the fuel supply to the engines was cut off. So the fuel supply was cut off intentionally. The swi…

Reminds me of 2017 Las Vegas shooting. The perpetrator looked and acted completely normal till the day of shooting and all his issues like anxiety or losing money was nothing far from ordinary. And what seems all of a sudden did a well planned shooting and didn't bother to leave a note or tell his story.

Free memento mori: you're both free-associating.

There's 0 reason to conclude murder-suicide, there's an infinitude of things that could have the same result, and both pilots denied it to eachother: how is that presented as proof?

I hope I don't need to explain why the fact no one knew in advance the Las Vegas shooter was going to shoot has ~0 similarities with the situation as we know it, and banal similarities with every murder.

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