Of the 3 fire warnings in flight I have had, all were found to be false indications from detector and wiring faults. Still I would have to find good reason not to act on a fire warning and shut it down.
In the situation you describe, I would shut it down and fire both bottles and then continue flight OEI to the nearest landing site where I could safely get visual. Descending towards mountains in IMC with an aircraft still capable of flight is madness in my opinion, and I would only do this if I knew for certain that we were on fire and unable to contain it.
My logic would say this:
If it were a real fire, then hopefully two bottles have extinguished it and even if they haven't it should hopefully burn itself out before breaching the engine bay. (Remembering that those engine bays are required to be able to contain a fire for a period of time to meet certification standards.)
If it were a spurious warning, oh well all I have done is shut an engine down and some maintenance is required.
In my view, the chance of a real fire continuing to burn with nothing but a fire warning as the only indication is highly unlikely.
"Rules are for the obedience of fools and the guidance of wise men." -Harry Day.
Last edited by the coyote; 4th Jan 2016 at 03:15.
Reason: Quote