Fire warnings - an intellectual debate on this contentious subject
The AW139 is unusual insofar as the Flight Manual provides an additional line in the proposed drill for Engine Fire In Flight that really needs further explanation but that explanation, it appears, is absent. That line says "Confirm engine fire". The lack of explanation has led to ambiguity in the way the drill should be interpreted. It appears that the consensus at the ATO is that the drill should always be completed as printed regardless how you answer the question posed by that line - is there a real engine fire..... or not?
Here is an interesting intellectual puzzle. Imagine two AW139's flying around IMC over the mountains, there's no radar service available and the cloud goes all the way down to the mountain tops and halfway to the valley bottoms.
Both aircraft have an engine fire warning and the crews begin the drill as per the QRH. One captain proceeds to adopt the 'as taught' procedure and arrives at the end of the drill with no more fire extinguishers but the light remains on. He knows that this could mean the fire is still burning or it could mean that it was a false warning and there never was a fire. Either way he is duty bound to follow the QRH drill or suffer the consequences of a subsequent legal case should his attempts at survival be only partially successful and passengers die as a result. He must now obey the strict instructions in the QRH to LAND IMMEDIATELY. This requires a descent 'at once' and implies that any risk is a lesser risk than staying airborne. Although he has doubts about the sense of his actions he is committed to obeying the book rather than his instincts. He begins a descent towards the mountains and trusts to luck.
The second captain has spent hours debating this very subject and his mind is prepared for a different analysis. Upon reaching that line in the drill the captain calls a halt and asks for help from crew and pax in confirming that there is a genuine fire. There are no signs on the instrumentation, no smells, no signs no smoke (actually ionic emissions) being detected in the baggage bay. Both pilots take turns to loosen their harness and open their doors to peer outside, no external smoke or flame visual from the engine bay area. He knows that if he takes the drill beyond that critical line he will be committed to the possibility of a forced descent as he too is a believer in the discipline of the checklist and if he gets to the line that says LAND IMMEDIATELY then he too will make a forced descent. He waits, still no signs of fire other than the lights. He's descends to MSA in preparation and LANDS AS SOON AS POSSIBLE. At any stage he is prepared to extend the drill beyond that critical line should the fire turn out to be real.
Who was right?
G