Air India Crash

[adam cool dude]

I thought the same, but it could be possible that they both failed at the same time due to something like a big enough jolt, eg, maybe moving the flaps handle a position or whatever

I would presume that a pre-flight checklist would determine that the locks are working and operational. For them to then both fail simultaneously after a pre flight check is 1 in a million.

This is obviously under the presumption that they actually do a pre-flight check to confirm the locks are working which imo is madness if they don't.

 

[MOOGLEYS]

I wouldn’t trust much on the initial report Boeing and even the ntsb like to blame the Aircrew. Look at the 747 Cargo door issues was aircrew up until one opened on the ground, Could never have been a fault with the aircraft both Boeing and the ntsb claimed. It took family of the victims to prove otherwise.

I’m sure there is more to this but who knows if it’s ever fully revealed unless it happens again.

 

[robj20]

Yeah watching the video a couple pages back, it doesn't seem like a great idea to place them directly below the thruster

Don't they group controls of a similar nature together

 

[robj20]

I’m sure it’s already been asked, but presumably the flight data recorder only sees voltages when switches are opened or closed? Could it be a freak electrical issue I wonder? Is there any scope for the switches to physically remain in the run position but the electrical signals to call for shutdown?

Not all switches operate like that on an aircraft, couple of our switch panels operate using PWM. 5v 90% duty cycle specifically, inverted for off.

 

[esmozz]

I've just scanned the report but not had a chance to digest it properly however I'll add a couple of thoughts.

The fuel cutoff switches are identical to ones on newer versions of the 737-800 and 737 Max aircraft and I've operated them many times. They are gated and in order to operate them you need to pull the switch up, move over the gate before releasing it. You need to do this in order to either move the switch up (on) or down (off).

In my opinion there is simply no way any kind of mechanical failure could cause both switches to inadvertently move position. If they are moved then it must have been an action by either pilot.

It is worth noting that it is entirely possible to move both switches with one hand, within a second of each other.

There were never going to be any good answers about what happened, but clearly now pilot suicide is on the table. It was always a possibility. I personally thought it was a credit to the tenor of this thread that, out of respect for the dead that this was not endlessly speculated on, nor were the names of the dead pilots besmirched needlessly.

That's clearly not the case anymore but I would just add a note of caution. The investigation still has a long way to run. And there are other explanations that could still be true. Suicide (and lets call it what it is in this case, mass murder) is a deliberate act. It's possible this was the result of some kind of neurological condition - a stroke, if you like. Or something similar. There have been cases where this has happened in the past, where a pilot has started acting irrationally or made involuntary movements due to the sudden onset of a medical condition of that nature.

 

[NickK]

The theory that was being thrown about a lot yesterday was that because it required two hands it must have been done by the pilot monitoring (as the pilot flying had his hands full). With the switches being flipped back by the pilot flying (with a single free hand hence them moving four seconds apart).

Or, the same problematic switches that have caused problems on the 737 were also used on the 787 and on this particular Air India flight. The answer seems to be yes.

It says in December 2018, the US Federal Aviation Administration issued a Special Airworthiness Information Bulletin (SAIB) highlighting that some Boeing 737 fuel control switches were installed with the locking feature disengaged.

While the issue was noted, it wasn't deemed an unsafe condition requiring an Airworthiness Directive (AD) - a legally enforceable regulation to correct unsafe conditions in a product.

The same switch design is used in Boeing 787-8 aircraft, including Air India's VT-ANB which crashed. As the SAIB was advisory, Air India did not perform the recommended inspections.

So it looks like there was an advisory to replace the switches that didn't have a lock, Air India didn't check and so that Air India flight could have had the disingaged switch locking installed. If so it looks like they can be accidentally switched off or switched off by vibration if there's no locking mechanism to prevent it.

 

[esmozz]

Or, the same problematic switches that have caused problems on the 737 were also used on the 787 and on this particular Air India flight. The answer seems to be yes.



So it looks like there was an advisory to replace the switches that didn't have a lock, Air India didn't check and so that Air India flight could have had the disingaged switch locking installed. If so it looks like they can be accidentally switched off or switched off by vibration if there's no locking mechanism to prevent it.

I just don't believe both of them could switch through mechanical failure within 1 second.

The switches were recovered from the aircraft in the run position, i.e. the last position they were recorded to be in. So it's safe to say the impact didn't inadvertently move them - I doubt vibration could.

 

[danlightbulb]

The fuel cutoff switches are identical to ones on newer versions of the 737-800 and 737 Max aircraft and I've operated them many times. They are gated and in order to operate them you need to pull the switch up, move over the gate before releasing it. You need to do this in order to either move the switch up (on) or down (off).

In my opinion there is simply no way any kind of mechanical failure could cause both switches to inadvertently move position. If they are moved then it must have been an action by either pilot.

It is worth noting that it is entirely possible to move both switches with one hand, within a second of each other.

What level of force is needed to move the switches and overcome the detent? Are we just talking a very minor thing, or is there quite a physical exertion (in the context of fingers and wrist of course) to lift and move the switch?

 

[Jokester]

I just don't believe both of them could switch through mechanical failure within 1 second.

The switches were recovered from the aircraft in the run position, i.e. the last position they were recorded to be in. So it's safe to say the impact didn't inadvertently move them - I doubt vibration could.

The report seemingly indicated that the pilots attempted to restart both engines on discovering the fuel cut off switches were in the off position, one engine was already running up and the 2nd was attempting to relight apparently.

 

[esmozz]

What level of force is needed to move the switches and overcome the detent? Are we just talking a very minor thing, or is there quite a physical exertion (in the context of fingers and wrist of course) to lift and move the switch?

The mechanical action is different of course but I'd say the level of force required is similar to that of opening a car door - maybe a little greater. You can easily do it with one hand.

 

[Uther]

Surely if it was pilot suicide wouldn't the pilot that closed the switches be trying to prevent the other pilot from turning them back on, and maybe some swearing in the cockpit related to that?

 

[Jokester]

"Possible brain fart of the century" Mentour Pilot said last night on his live stream.

People do things like that, I know somebody that inadvertenly pushed an emergency shutdown pushbutton on an oil platform without thinking.

 

[LiE]

This is a helpful image from BBC.

 

[200sols]

Or, the same problematic switches that have caused problems on the 737 were also used on the 787 and on this particular Air India flight. The answer seems to be yes.



So it looks like there was an advisory to replace the switches that didn't have a lock, Air India didn't check and so that Air India flight could have had the disingaged switch locking installed. If so it looks like they can be accidentally switched off or switched off by vibration if there's no locking mechanism to prevent it.

Having both switches simultaneously switching to the cut off position because of vibration or anything like that is incredibly unlikely.

 

[Penfold101]

I've just scanned the report but not had a chance to digest it properly however I'll add a couple of thoughts.

The fuel cutoff switches are identical to ones on newer versions of the 737-800 and 737 Max aircraft and I've operated them many times. They are gated and in order to operate them you need to pull the switch up, move over the gate before releasing it. You need to do this in order to either move the switch up (on) or down (off).

In my opinion there is simply no way any kind of mechanical failure could cause both switches to inadvertently move position. If they are moved then it must have been an action by either pilot.

It is worth noting that it is entirely possible to move both switches with one hand, within a second of each other.

There were never going to be any good answers about what happened, but clearly now pilot suicide is on the table. It was always a possibility. I personally thought it was a credit to the tenor of this thread that, out of respect for the dead that this was not endlessly speculated on, nor were the names of the dead pilots besmirched needlessly.

That's clearly not the case anymore but I would just add a note of caution. The investigation still has a long way to run. And there are other explanations that could still be true. Suicide (and lets call it what it is in this case, mass murder) is a deliberate act. It's possible this was the result of some kind of neurological condition - a stroke, if you like. Or something similar. There have been cases where this has happened in the past, where a pilot has started acting irrationally or made involuntary movements due to the sudden onset of a medical condition of that nature.

I’m glad we’re still going here - the third thread on the subject over on PPRuNe has now been locked for over zealous speculation…

 

[Trifid]

The fuel cutoff switches are identical to ones on newer versions of the 737-800 and 737 Max aircraft and I've operated them many times.

Are the cut off switches used to turn off the engines in normal operation? And then part of the start up routine? Could they have been improperly returned back to the run position so as to easily be disengaged during flight?

 

[esmozz]

I’m glad we’re still going here - the third thread on the subject over on PPRuNe has now been locked for over zealous speculation…

Never liked that forum. I used to post on there but haven't done so for many years. Undoubtedly there is a lot of knowledgeable people there but I suspect there's more than a few Walther Mitty types as well.

 

[esmozz]

Are the cut off switches used to turn off the engines in normal operation? And then part of the start up routine? Could they have been improperly returned back to the run position so as to easily be disengaged during flight?

In a nutshell, yes. They are used as part of normal operations to start and stop the engines at the beginning and end of each flight.

It's hard to imagine a way in which they both could be disengaged within one second without somebody doing it.

 

[esmozz]

There is one thing that doesn't quite sit right with me, and its probably nothing but although the engine switches were switched to cutoff within one second of each other - it took 4 seconds between switching one back to run, followed by the other. That would seem like an age in that situation.

Believe me - if you needed to, you could flip both those switches back to run in less than a second.

It's probably nothing or just a consequence of the incredibly chaotic situation but just seems a bit odd.

 

[Werewolf]

In a nutshell, yes. They are used as part of normal operations to start and stop the engines at the beginning and end of each flight.

It's hard to imagine a way in which they both could be disengaged within one second without somebody doing it.

I'm fairly sure there was one a while back where they found that part of the cause was because a pilot's watch (or something similar) caught on an engine control whilst he was reaching for something else. There have been some very strange causes of crashes involving accidental disengagement of controls and sometimes IIRC it's taken someone getting into the same version of the aircraft wearing the same items as the pilot to test out a wild theory that was hinted at in the recorders.

IIRC that resulted in a modification to the controls for that aircraft, unfortunately my googlefu is weak so i can't find it.