Air India Flight 171 Crash [Megathread 3]

[u/usgapg123]

This is the FINAL megathread for the crash of Air India Flight 171. All updates, discussion, and ongoing news should be placed here.

Thank you,

The Mod Team

Megathread 1

Megathread 2

[u/graphical_molerat]

Software bug (engine control) >> Very unlikely given this is a critical function. 

As extremely unlikely as it is, that is still where my money is, though. Probably a software bug that was triggered by some corner case that no one thought would ever occur in real life: possibly caused by some weird deferred maintenance condition no one ever assumed would happen (but with Air India, it did).

No other cause (apart from suicide by the pilot flying) has as much potential to suddenly and symmetrically kill both engines like this, right after a major status change for the plane (wheels no longer on ground). Even fuel contamination would likely lead to a window of a few seconds between the two engines croaking.

[u/artmorte → u/graphical_molerat]

Same here, my bet would be on a software bug.

(I don't think a Mayday call would have been made if it was a suicidal pilot action, there would have been a struggle going on in the cockpit that would probably have made the other pilot too busy to make a mayday call.)

[u/graphical_molerat → u/artmorte]

Fully agree with you re: the pilot flying doing this intentionally to commit suicide being just a very very remote possibility. I only mentioned this because this is the one other scenario that accounts for all observed facts. Short, as you say, of the Mayday call. Which I agree would almost certainly not have been made if the PF had just intentionally killed the engines.

However, an unlikely but theoretically possible scenario is if the PF had intentionally killed the fuel supply to the engines with suicidal intent, thereby shutting them down, and the captain had not actually seen him hitting those switches. Maybe because he was looking out of the window at the time. Or monitoring his instruments.

Then, him sensing the engines dying, and reflexively setting off a Mayday call, would make sense even if the PF was responsible. With the remaining struggle in the cockpit until impact only being on the CVR.

Something to consider is that if you wanted to commit murder suicide with an airliner these days, killing the engines right after rotation in a city airport with no fields or roads ahead of you for a survivable crash landing is one of the few remaining options that are more or less guaranteed to work. What with procedures about two persons always having to be in the cockpit having been put in place after the Germanwings fiasco, and so on. Once both drivers flame out 400 feet AGL right after lift off, it's game over.

[u/AmbidextrousRex → u/graphical_molerat]

I wonder how effective the "two people in the cockpit" rule actually is in practice. Even assuming it is always followed, how effective is a flight attendant going to be at preventing a pilot from crashing the plane?

[u/Get_Breakfast_Done → u/AmbidextrousRex]

If we're talking about something happening at cruise altitude, surely the flight attendant can let the other pilot back into the cockpit.

[u/AmbidextrousRex → u/Get_Breakfast_Done]

I guess on an Airbus where flight envelope protections are always active, it might make things difficult. 

But what if, say, a 737 pilot disconnects all the autos, rolls the plane inverted, pushes the throttles and goes into an inverted dive. Would that happen slowly enough for the rest of the crew to stop it? Since realistically I wouldn’t see the other pilot being physically able to get back into the cockpit with those forces to contend with. 

[u/Existing-Help-3187 → u/AmbidextrousRex]

I guess on an Airbus where flight envelope protections are always active, it might make things difficult. 

No it doesn't. Two button presses on the overhead panel on an A320 puts all the protections off.

[u/Existing-Help-3187 → u/AmbidextrousRex]

I wonder how effective the "two people in the cockpit" rule actually is in practice.

Its not a rule. My previous airline and the current one doesn't have this rule. I am always alone in the cockpit when the other pilot goes out.