I thought when they design helicopters they are to follow a set of regulations in their design criteria that says something like this:
§ 29.861 Fire protection of structure, controls, and other parts.
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Each part of the structure, controls, and the rotor mechanism, and other parts essential to controlled landing and (for category A) flight that would be affected by powerplant fires must be isolated under §29.1191, or must be—
(a) For category A rotorcraft, fireproof; and
(b) For Category B rotorcraft, fireproof or protected so that they can perform their essential functions for at least 5 minutes under any foreseeable powerplant fire conditions.
So surely the helicopter MAY NOT fall out of the sky in the extra minute to climb to say 500 ft! But then again I believe some common sense may be the deciding factor to keep us alive. if I do smell smoke or burning or if the smoke has penetrated the cabin then I will not hesitate to apply the Fire Drill straight away. If the smoke is so thick and toxic that the pilots are likely to be intoxicated by continue flight (even though I have the speed and altitude) I may elect to ditch/ land immediately.