Comment by bombcar
3 days ago
It's interesting to try to imagine a device that would prevent that, without causing more issues.
My preliminary idea is a "fuel bladder" for take-off that inflates with enough fuel to get the plane to a recoverable altitude, maybe a few thousand feet?
Or you simply interlock the engine cutoff with the thrust lever position, any position other than idle prevents shutdown. This all goes through the flight computers already.
If there’s a fire or similar problem the fire handles will cut off fuel without the normal shutdown procedure, but the normal switches only need to be used at idle thrust.
I wonder if Airbus has this logic, since their philosophy is to override the pilot commands if they’d endanger the aircraft (which has its own issues of course) where’s Boeing will alert the pilots and still perform the action. I don’t have access to that information.
According to AI, Airbus places these switches on the overhead panel, so that alone would make it harder to inadvertently move them. Apparently, Airbus "protections do not extend to mechanical or FADEC‑controlled systems like the engine‑fuel shutoff valves. If you deliberately pull and flip the ENG MASTER lever to OFF, the FADEC will immediately close the LP and HP fuel valves and the engine will flame out. If you then return the lever to RUN (and you meet relight conditions), it will automatically relight."
And that's why you don't trust AI.
As another commenter said the Airbus engine start/stop controls are located behind the thrust levers, and according to the A350 operations manual which I got my hands on there are two conditions required for the FADEC to command engine shut down: Run switch to off, thrust lever to idle.
So if that's correct on an Airbus aircraft you can't just switch off the engines when they're commanded to produce thrust. This also seems to be backed up by the difference in the guards for those controls in the Airbus cockpits.
Well, AI is plain wrong. Fuel cutoff switches on Airbus are in the same position as in Boeing planes, below the throttle.
I think engine fires are still more common than suicidal pilots and inadvertant fuel shutoff activations.
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.
It’s a pointless exercise though - if one of the pilots wants to crash the plane, there’s almost nothing that can possibly be done. Only if someone can physically restrain them and remove them from the controls.
There’s always going to be many ways they could crash the plane, such a feature wouldn’t help. The pilots are the only people you can’t avoid fully trusting on the plane.
3 replies →
> 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 be fun.
1 reply →
The flip flop thing is a neat idea since a single engine can typically maintain level flight and two burning engines is rare.
> My preliminary idea is a "fuel bladder" for take-off that inflates
Will the bladder be marketed by Kramerica Industries?