Air India crash fuel switches turned off

[limetrees32]

I've not found a thread on this , although it's taken me so long to search out the knowledgeable posters
on the Washington crash that there probably is one now.
But @notimagain what do you think ?

Could the issue go a litle deeper.

The switches were found to be in the on position in the wreckage. The "event" that they were switched off and on is recorded electronically, there is no video available.

Could the computer on board have an issue where it recorded "Off" and actually switched the engines off because of an electrical or software issue. The pilots they noticed this and one asks "Did you switch the engines off"? To which the other replies "I didn't". At this point they switch them on which simply resets the computer and it takes action by attempting to restart the engines, too late for the people who sadly lost their lives.

We make simple electronic circuits using £5 kits, and this sort of an issue is all too common where electrical noise or simple short circuits cause resets, I would assume that a multi billion company like Boeing has electrical check and balances. But for those interested, you may want to look at the Airbus A380 case where there was delay in production because a computer mis calculated cable length and when they assembled the wiring it was a few cm short.

He locked the other pilot out of the cockpit, and then the plane went into a nose dive. I’m not sure what other conclusion you could draw that.

There is no single ‘The Computer’ on an aircraft which is in charge of everything. There are lots of separate computer systems controlling or calculating information for different purposes which in many instances work in conjunction with each other. For example the Flight Management Computer or Air Data Computer. These are all individual components of the aircraft. But there is no computer in charge of everything. And there is certainly nothing on board a modern airliner (besides the pilots themselves) that can move switches remotely. Where you say “At this point they switch them on which simply resets the computer” I have no idea which computer you might be referring to.

Video is the only method that I know of where a physical movement can be captured to check that it indeed did happen. While anything which gets recorded is because some micrcontroller (which I referred to as a computer) received a "simple contact" to indicate an event.

Thus, to say the "switches were moved", this is deduced by a recording on a digital (or even analogue tape) device, but the signal to write this message came across a wire. There is no video (as yet maybe) to show actual movement of switches taking place.

Morning

@SuratNuJaman

Could the computer on board have an issue where it recorded "Off" and actually switched the engines off because of an electrical or software issue. The pilots they noticed this and one asks "Did you switch the engines off"? To which the other replies "I didn't"

Each engine has it's own independent computer, used to be called FADEC ( Full Authority Digital Engine Control), not sure if that's the current term but it will do for here.

There's no commonality across the engines, so on a twin the left engine has it's own FADEC, and the right has it's own FADEC.

The two cutoff commands that are being referred to were registered on the Flight Data Recorder (FDR) and were apparently separated by approx 1 second...so for your theory to stand up you'd have to have two computers suffering an identical and AFAIK unprecidented fault on the same aircraft at not quite but at almost the same moment.

We don"t know yet what exactly what was said on the flightdeck so we need to be careful with quotes. It may be significant that the Indian AAIB uses the word cutoff in their precis of the conversation, not "engines..." and cutoff is the term used on the placard beneath the fuel control switch.

Finally if I'm understanding the system correctly, based on discussion by well respected engineers on a other forum, the FDR directly senses switch position, not the signal downstream...i.e. if the FDR data says the switch is at cutoff then that is indeed the physical position of the switch....and the Indian AAIB is quoting times for switch operation based on FDR data.

The FDR senses because it receives an electric signal. And an electrical signal is suspectible to noise or even a spark.

For people who love music and buy expensive Amplifiers, the reason some Amplifiers are more expensive than others is because the expensive ones have cable routing and components to reduce "electrical noise". Electrical noise I believe even affects the top end NVIDIA cards more so because of closeness of tracks.

The 'brain fart' theory stuck with me.

Having read the sad thread about parents leaving their children in hot cats simply because their routine was different than normal and they carried on with their lives without registering the fatal mistake... could it be something like that?

Or acting out an intrusive thought?

Obviously we are speculating, and tbh I wonder why they have released only some of the information before it's all available. It's only going to make speculation worse.

People who know the internal workings of the sensors Boeing use can comment better on the type of sensor used, is it a contact, a resistance, an optical sensor?

@backinthebox

Agree with all your various pps..

I think folks are desparate to pin this on tech/computers/Boeing, rather than face the uncomfortable fact that if someone moves a switch - one that the crew must have - that cuts off fuel to the engine(s), then the engine(s) stop.

Based on what we know today, the contents of the interim report, we know what probably happened, we sure as heck don't know why.

Of course all the above might change when we see the final report.

You'll need a system specialist (try the pprune forum for that) but don't hold your hopes up that this is all or in part down to corrupt data...

May we know "one that the crew must have ", is there a video of this? The sad reality is an electrical spark causing electrical noise is unlikely recorded. But if a video surfaced of crew action then "Slam Dunk".

Obviously we are speculating, and tbh I wonder why they have released only some of the information before it's all available. It's only going to make speculation worse.

Because the rules of this accident investigation board are that a preliminary report must be released. This is very common and also happened for the Washington plane/heli crash and the Bayesian yacht, to name but two.

Any physical device when needed to be "detected" or "sensed" can only be done by Contact, Resistor (a type of contact), Optical where a beam of light is broken by a physical object, or in unusual appications by chemical means (I doubt in an aircraft they would rely on this). The contact is the "gold standard" as it is the simplest and effective.

Just wanted to add that speculation post interim report is disrespectful to the pilots.

Also a question for @notimagain Can the plane take off with the switches set to cut off? I'm presuming not. Thanks.

You are right.

If the switches were set to cutoff, the engines wouldn’t be getting fuel.

I'm on about the Fuel Control Switch..crew need those for safety and other operational reasons which I've explained I hope in sufficient detail in at least a couple of other pps.

There's no cockpit video.

You mentioned electrical issues,.sparks,.but haven't acknowledged my comment that the engines have no commonality when it comes to digital control or even wiring and that the engines didn't quite shut down simultaneously.

TBH you seem to be chasing an edge case that isn't supported by all the data we do have.

Oh I know nothing about piloting but there's a pilot on The Times comments. It was a bit technical so I might have misunderstood.

It’s really not. Speculation is natural, and understandable, given the ubiquity of aeroplane travel. Can a plane take off without the engines using any fuel? Um, no.

If the fuel is accidentally cut off to one engine, can a plane survive with fuel going to only one engine?

Yes, modern, twinjet airliners are quite capable of taking off with only one engine operating.

My goodness that's shocking 😯. Don't watch before going to sleep, or in the airport is my advice.

Basic rule is a single engine failure shouldn't cause an accident (though for info a failure at low speed on take-off is a "stop", you can't carry on).

In the case if this accident if they had suffered a single engine failure just after liftoff they should have been able to climb away.

Did anything ever go wrong when you were a pilot @notimagain

I always wonder whether we are being told the truth in these situations. But so sad for those who are involved.