can you tell me how the right engine/prop is placed into "HOTEL MODE" for ground use as a pseudo apu?
It is done via a guarded swith on the overhead panel, ac needs to be on ground,gust lock engaged and prop #2 feathered.
If that had been a part of this accident there would also have been a prop brake unlock warning.
The prop bake is not capable of stopping an unfeathered propeller, it will destroy the propbrake itself by heat, and possibly cause a eng fire warning too.