As an engineer who has had to design fire containment zones, the 2000 degree, 15 minute rule is a correct assumption - this is the FAA definition of fireproof.
The airflow computational modelling techniques around these days can give you lots of insight as to the ability for a defined compartment to sustain a fire (does the cooling air flow overpower the mix?). You still need to perform an FAA sanctioned concentration test to get your ticket but the tools available should get you to within one test instead of a series of expensive, iterative tests
I was always taught that the sensing elements had a certain delay, as do the crew, hence the time scale.
It was assumed the procedure would be to power back (not shut down) determine if the warning goes away (a broken HP line would be one conclusion) and if not, shut off the fuel. If this doesn't put the fire out, the first shot of the bottle should be pulled.
Does this go with or against operators SOP's ??
It will be interesting to hear the users views on the subject
