737 Engine cut on Vr and A/T disengages automatically. Why?

[737Andi]

Hi,
I'm currently training failures with the PMDG 737 NGXu. I'm programming an engine failure at Vr, which works fine. I'm getting a severe engine damage then. However at the same time the failure is activated, the A/T disengages automatically and when I re-activate the switch it deactivates itself immediately from alone again. I saw a tutorial video where this is not happening.
Any idea what is causing this issue?

Thank you very much!

Best regards Andi

[FlyingStone]

Wouldn't know what happens in your flight sim, but generally, the A/T is the first thing that has to be switched off with an engine failure in the 737, as the aircraft has to be flown with manual thrust, if only one engine is operating.

[excrab]

The cause must be a software issue in the simulator. In the aircraft there is no automatic disengagement of the auto-throttle, as FlyingStone says “Auto-throttle....if engaged....disengage” is the first action in the memory drills for engine fire/severe damage/separation.

[737Andi]

Thank you for your answers!!!

I received a reply regarding this topic on another forum that the A/T might be disconnecting from alone as a safety measure when the thrust output difference of the two engines becomes too big.
For example when a thrust lever gets stuck during A/T movement (example Guilin 737 flight --> https://aviation-safety.net/database/record.php?id=19921124-0&lang=de)
or an engine fails or during engine start with a very high difference between N1 of the starting engine and the unstarted one.

Hopefully you can explain this a bit more in detail. Most of you guys are real pilots so I suppose this is the best place to get a detailed answer.

Thanks!

Best regards Andi

[Denti]

That might depend on installation status. On fail operational 737s the autothrust is used in single engine ops during approach, in fact it is mandatory for autoland on one engine. And yes, the logic is perfectly happy and only moves the operating engines thrust lever.

[737Andi]

Ok..that makes sense. That would mean that the new PMDG 737 NGXu is actually simulating a non fail safe 737 that is not controlling the thrust levers separately when one engine fails??

[737Andi]

Can anyone please confirm that my assumption is correct? Thanks!