Am Montag, 23. November 2015 17:58:58 UTC+1 schrieb Bruce Hoult:

Is it noisy in gliding flight?

It makes very little noise.

Does it increase engine noise? (perhaps not as I think the engine is on the mast with the doors closed when running?)

The engine is on a mast.

Is that not a firewall?

Why would an engine stowed away in the engine compartment catch fire?! And if it could, why is there no fire sensor installed? So no, it's not a fire wall.