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Preliminary report into Air India crash released

bbc.co.uk

521–530 of 924 posts

Re: Preliminary report into Air India crash released

#521

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.

I want you to guess how many traffic accidents are caused by accidentally reversing when you intended to go forward. Test your mental model against the real world. This is your opportunity.

Driving isn't trained to anywhere near the same standard.

Probably more training required to bake a cake than drive a car (hours wise).

If we had your typical driver fly a plane we'd be doomed to a lot of crashes.

Re: Preliminary report into Air India crash released

#522

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…

https://www.youtube.com/live/SE0BetkXsLg?si=LPss_su3PVTAqGCO Both of these extremely-experienced pilots say that there was near zero chance that the fuel switches were unintentionally moved. They were switched off within one second of each other, which rules out most failure scenarios. If it was an issue with the switches, we also would have seen an air worthiness directive being issued. But they didn’t, because this…

A few years ago I was working at a company that used a robotic arm when an accident occurred. The robot was powered off for maintenance but suddenly turned on, pinned a worker's arm, and threw him against a wall. His arm had numerous fractures and he had severe head injuries but survived.

The other worker in the building was in absolute shambles and couldn't understand what had happened. The CCTV footage was then checked and showed that worker looking at the other while reaching for the power switch and turning on the machine. The switch was not locked out and tagged out, but it was the only switch like it on the whole panel, large and required significant force to turn. No way to accidentally bump it, and the video showed him clearly turning the handle.

He was obviously fired, but no criminal charges were ever brought against him. He had no plausible motive for wanting the other man dead, was severely distraught over the incident. It was simultaneously obvious that he had turned the lever deliberately and had not meant to turn the leaver. A near-lethal combination of muscle memory and a confusion caused the accident. If the lever had been locked and tagged out, that probably would have interrupted his muscle memory and prevented the accident, but it wasn't.

Point is, something can be simultaneously impossible to do inadvertently, but still done mistakenly. A switch designed to never be accidentally bumped, to require specific motions to move it, can still be switched by somebody making a mistake.

Re: Preliminary report into Air India crash released

#524
post #346

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 tha…

> the pressure difference at altitude works to hold the window in place

Curious, is the pressure difference actually greater than the force of 800km/h wind pushing on the window? Or is it just for side windows?

Re: Preliminary report into Air India crash released

#525
post #448

Earlier quoted context omitted.

That's just your brain associating the bathroom with the act of brushing your teeth, and therefore doing it automatically upon the trigger of entering the bathroom. It bears no resemblance to the accidental activation of a completely different button. The other poster's correction: "it’s like brushing your teeth with razor" is apt. Touching the fuel cutoff switches is not part of any procedure remotely relevant to th…

Now I'm trying to remember if I've ever picked up my razor and accidentally begun tooth brushing motions with it. Probably! More relevantly, you seem to me to be unduly confident about what this pilot's associative triggers might and might not be.

Good analogy. Things I do every day in front of the mirror, but I occasionally attempt to squeeze some soap on my toothbrush. Or I have to brush my teeth and I find my beard foamed up. Or I walk out of the shower after only rinsing myself with water.

Re: Preliminary report into Air India crash released

#526
post #311
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…

But humans can't tell perfectly either and would be responding to much of the same data that automation would be.

I wonder if they could have buttons that are about the situation rather than the technical action. Have a fire response button. Or a shut down on the ground button.

But it does seem like half measure automation could be a contributing factor in a lot of crashes. Reverting to a pilot in a stressful situation is a risk, as is placing too much faith in individual sensors. And in a sense this problem applies to planes internally or to the whole air traffic system. It is a mess of expiring data being consumed and produced by a mix of humans and machines. Maybe the missing part is good statistical modelling of that. If systems can make better predictions they can be more cautious in response.

Re: Preliminary report into Air India crash released

#527
post #202

Earlier quoted context omitted.

Probably time to design a plane that can't be sent into terrain in seconds by flipping a switch.

Now try to design a plane that also lets you rapidly shutoff fuel to both engines in case of fire.

How about actual switch covers (and switches that are not located right in the same area as stuff you are using routinely) instead of a glorified detent? Though I suspect this would also succumb to muscle memory

What about up on the overhead panel where the other engine start controls are?

Or (at the cost of complexity) you could interlock with the throttle lever so that you can't flip the cutoff if the lever isn't at idle

Also the fire suppression system is a different activation (covered pull handles I think)

Re: Preliminary report into Air India crash released

#528
post #504

Earlier quoted context omitted.

The idea would be something that is ONLY operational after V₁ and until some safe height. Or maybe a design that prevents both switches being off (flip flop?) for X minutes after wheel weight is removed? Again, it’s probably pointless but it’s an interesting thought exercise. Suicidal pilots are apparently more common than we’d want.

> Again, it’s probably pointless but it’s an interesting thought exercise. Coming up with ad-hoc solutions is easy, especially the less you know about a complex system and its constraints. I'd say it's not an interesting exercise unless you consider why a solution might not exist already, and what its trade-offs and failure modes are. Otherwise, all you're doing is throwing pudding against a wall, which can of course…

That’s the whole fun part - come up with an “obvious” solution and the try to figure out the problems or risks it would cause.

For example, an obvious solution is that the switch can't be changed from "RUN" to "CUTOFF" when the throttle isn't at idle - this could be done with a mechanical detent because they're right next to each other. Simple!

But now you've introduced additional failure modes - throttle sticks wide open and the engine is vibrating and needs to be shut down - so maybe you make it that the shutdown switch can work for ONE engine at any throttle position, but if TWO get turned off, both throttles have to be off, but that introduces ...

Re: Preliminary report into Air India crash released

#529
post #371

Earlier quoted context omitted.

https://www.youtube.com/live/SE0BetkXsLg?si=LPss_su3PVTAqGCO Both of these extremely-experienced pilots say that there was near zero chance that the fuel switches were unintentionally moved. They were switched off within one second of each other, which rules out most failure scenarios. If it was an issue with the switches, we also would have seen an air worthiness directive being issued. But they didn’t, because this…

Maybe as the PIC was guarding the lower end of the throttle he rested the rest of his hand on the panel cover below the throttle and, while pushing forward on the throttle, let the side of his hand slide down right onto the switches, the likeliness of which would have been exacerbated by a rough runway or a large bump. It's unlikely the left and right part of his hand would have contacted the cutoff switches at the s…

Nope. First of all, the FO was the “pilot flying” and thusly controls the throttle. The fuel shutoffs are on the left side, well clear of the range of motion throttle operation for the right seat.

If the Captain were controlling throttles, it for some reason he could contort his wrist to accidentally open the red cutoff switch guards, the switches themselves move in the opposite direction of the pivot of the switch guard. And to have that happen to both switches — one second apart. That would be astronomically (not to mention anatomically) improbable: you can’t have your hand on the throttle and also be dragging your arm on the switches unless the pilot has an extra elbow.

Further more, the 787 has auto throttles, at takeoff the pilot advances the throttles to N1, then all the way through climb out the auto throttles control the throttle unless manually disengaged.

Also a “bumpy runway” wouldn’t do anything because if those switches were activated on the roll out, the engines would shut down almost immediately: that’s the point of those switches to kill fuel flow immediately not minutes later.

And no there isn’t a report of the safety locks not working properly on the 787. The report to which you are referring was in 2018 and that was an issue with a very few 737 switches that were improperly installed. The switches didn’t fail after use, they were bad at install time. Exceedingly unlikely that a 787 was flying for 12 years with faulty switches. (Notwithstanding the fact they they are completely different part numbers.)

The 787 that crashed had been in service since 2013 which means if that were a problem in that plane, however unlikely, with hundreds of thousands of flight hours, inspections, and the 2018 Airworthiness Bulletin — that problem would have been detected and corrected years ago.

Re: Preliminary report into Air India crash released

#530

Earlier quoted context omitted.

But they don't look protected or hard to switch?

The pilot is toggling the switch on. Toggling it off presumably requires more power and is multiple actions.

You move those switches down apparently. I don't think so.
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