It is astonishing why different operators choose to operate the same system differently. Surely the manufacturers have a standard method. I've flown for both philosophies. When we asked for an explanation it usually turned out to be whim of the CP; rarely the manufacturer's recommendation.
Explanations for waiting 30secs.
"the discharge tubes would be blocked by too much discharge, so no advantage in flow rate of extinguishent."
Not waiting:
"allows max rate of discharge of extinguishent, even if the tubes are blocked in the first instant."
"avoids distraction during a critical situation: avoids forgetting if distorted by events."
Pays yer money takes yer choice.
What might be more a grey area is what to do, ref' evac, if the fire goes out. Someone said evac as soon as the bottles have been discharged: others say ask the firefighters, who should be outside, what they can see. IMHO the tower would be too far away. In the B737 EVAC QRH the whole procedure is written without a break. What do guys thing about re-checking the situation half way thought the QRH - e.g. fire warning plus outside information - before ordering the evac?
Does anyone have an SOP to cover the scenario or is it always down to Captain's discretion?
Last edited by RAT 5; 6th March 2016 at 13:08.