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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

#341

Post by ExoticPearTree »

macintux wrote: post #245
747fulloftapes wrote: post #139

Earlier quoted context omitted.

The landing gear lever is rather prominently featured in the 787 in a panel central to the cockpit layout so that either pilot can easily reach it. For decades and across many manufacturers, the landing gear lever has traditionally featured a knob that deliberately resembles an airplane wheel. It's very hard to mistake it for anything else. It's actuated by simply moving it up or down. The fuel control switches are b…

> This idea strikes me as even more unlikely than someone shifting their moving vehicle into reverse while intending to activate the window wipers. I suspect you've never driven an older vehicle with the shifter on the steering column.

> I suspect you've never driven an older vehicle with the shifter on the steering column.

Or a new Mercedes ;)

Re: Preliminary report into Air India crash released

#342

Post by michaelmrose »

p1mrx wrote: post #217
pixl97 wrote: post #142

Earlier quoted context omitted.

When your engine catches on fire/blows apart on takeoff you want to cut fuel as fast as possible.

Proposed algorithm: If the flight computer thinks the engine looks "normal", then blare an alarm for x seconds before cutting the fuel. I wonder if there have been cases where a pilot had to cut fuel before the computer could detect anything abnormal? I do realize that defining "abnormal" is the hardest part of this algorithm.

If engine_status == normal and last_activation greater than threshold time

    warn then shut off
Else Shut off immediately End

Override warning time by toggling again.

Re: Preliminary report into Air India crash released

#343

Post by michaelmrose »

lxgr wrote: post #311
p1mrx wrote: post #217

Earlier quoted context omitted.

Proposed algorithm: If the flight computer thinks the engine looks "normal", then blare an alarm for x seconds before cutting the fuel. I wonder if there have been cases where a pilot had to cut fuel before the computer could detect anything abnormal? I do realize that defining "abnormal" is the hardest part of this algorithm.

If the computer could tell perfectly whether the engine “looks normal” or not, there wouldn’t be any need for a switch. If it can’t, the switch most likely needs to work without delay in at least some situations. In safety-critical engineering, you generally either automate things fully (i.e. to exceed human capabilities in all situations, not just most), or you keep them manual. Half-measures of automation kill peop…

If the warning period is short enough is it possible it's always beneficial or is 2-3 seconds of additional fuel during a undetected fire more dangerous?

Re: Preliminary report into Air India crash released

#344

Post by michaelmrose »

macintux wrote: post #244
zahlman wrote: post #159

Earlier quoted context omitted.

This is a place that puts "Hacker" in the name despite the stigma in the mainstream. Given the intended meaning of the term, I would naturally expect this to be a place where people can speculate and reason from first principles, on the information available to them, in search of some kind of insight, without being shamed for it. You don't have to like that culture and you also don't have to participate in it. Making…

For me it's mainly about intent/unearned confidence. If someone is speculating about how such a problem might be solved while not trying to conceal their lack of direct experience, I'm fine with it, but not everyone is. If someone is accusing the designers of being idiots, with the fix "obvious" because reasons, well, yeah, that's unhelpful.

I don't think most think they know better but it's frankly fun to speculate and this is a casual space rather than the serious bodies tasked with actually chewing over this problem in earnest.

Re: Preliminary report into Air India crash released

#345

Post by Aurornis »

prepend wrote: post #228
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…

I once worked with a software engineer who would do things and then bald face lie about it. This reminds me of that person. Me: “The build is breaking right after you checked in. Why did you do that?” Him:”I did not do so.” Me: “The commit shows it as you. And when I rolled back everything builds.” Him:”It must have been someone else.” That person was really annoying.

I’ve worked with some chronic liars. They would deny reality no matter how much evidence you had.

The weirdest thing was how often it worked for them. In each case their lying eventually caught up with them, but in some cases they’d get away with lying for years.

It’s amazing how often someone would have clear evidence against what they were saying, but the people in positions of authority just wanted to de-escalate the situation and move on. They could turn anything into an ambiguous he-said she-said situation, possibly make a scene, and then make everyone so tired of the drama that they just wanted to move on.

Re: Preliminary report into Air India crash released

#346

Post by tzs »

maxbond wrote: post #295

I just want to call out that, whatever the facts of this case, pilot heroism is way more common than pilot murder. This is off the top of my head, so don't quote me on the precise details, I'm probably misremembering some things. But a few of my favorite examples: - British Airways 5390: An incorrect repair causes the windshield of a plane to be blown out mid flight. A pilot is nearly sucked out. The head flight atte…

> British Airways 5390: An incorrect repair causes the windshield of a plane to be blown out mid flight. A pilot is nearly sucked out.

This one is a good illustration of how better design can help prevent accidents or make them less severe.

The error the maintenance people made was that when they replaced the window and the 90 screws that hold it on 84 of the screws they used were were 0.66 mm smaller in diameter than they should have been.

The window on that model plane was fitted from the outside, so the job of the screws was to hold it there against the force of the pressure difference at altitude. The smaller screws were too weak to do that.

If instead the designers of the plane had used plug type windows which are fitted from the inside then the pressure difference at altitude works to hold the window in place. Even with no screws it would be fine at altitude. Instead the job of the screws would be to keep gravity from making the window fall in when the plane is not high enough for the pressure difference to keep it in place.

My vague memory of the Air Emergency episode on this (AKA Air Crash Investigation, Air Disasters, Mayday, and maybe others depending on what country and channel you are watching it on) is that after this accident many aircraft companies switched to mostly using plug windows on new designs.

Re: Preliminary report into Air India crash released

#347

Post by yallpendantools »

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…

[dead]

Re: Preliminary report into Air India crash released

#349

Post by mrlongroots »

michaelmrose wrote: post #327
Epa095 wrote: post #211

Earlier quoted context omitted.

But from the audio recording it seems like one pilot is noticing them bering in the CUTOFF position, and asking why (and moving it back). If the switch was actually in RUN, but some other issue caused the signal to be sendt, the pilot would see it beeing in the RUN position, not CUTTOF.

Are they looking at the physical switch or data about the state of the engine displayed in some other fashion?

This is very clearly EAFR data, so the logical/electrical switch state. Nothing about the mechanical state of the switches has been mentioned, except a picture that shows their final state to be in the RUN position (which makes sense given the relight procedure was ongoing).

From what I understand, the relight procedure involves cycling these back to CUTOFF and then to RUN anyway. So it is not clear if they were mechanically moved from RUN to CUTOFF preceding the loss of thrust, or cycled during relight.

Re: Preliminary report into Air India crash released

#350

Post by Velorivox »

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…

This is highly reminiscent to me of this case. [0] The co-pilot accidentally hit the wrong switch and then quietly corrected his mistake later, without resetting the previous switch (which led to feathering).

[0] https://en.wikipedia.org/wiki/Yeti_Airlines_Flight_691

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