Originally Posted by
galdian
Wasn't being specific about the fire cause, just interested in any thoughts of pro's/cons in restarting.
I'm assuming the 777 same as 737 with 2 bottles that can be fired in sequence as/if required.
If you'd had a fire but only fired one bottle - why wouldn't you try a restart?
If you'd had a fire and had fired BOTH BOTTLES to extinguish? Now the question gets more interesting.
Apologies if the 777 is a very different system to the 737.
It's similar - one bottle each side which can be fed to either engine (it's pretty standard Boeing design philosophy).
I suppose it's a judgement call, but best case you're looking at something around 100 mile glide range for a complete power loss at cruise altitude (obviously dependent on how high and how heavy, but 100 miles is a good rule of thumb). But if you previously shut one engine down and you've already dropped down to the engine out cruise altitude then your potential range will be quite a bit less. So if you don't have sufficient range to make a runway, restarting the 'fire' engine is at least worth consideration. If the fire warning went out shortly after shutdown (without firing a bottle), there is a good chance it's a pneumatic leak or possibly even a false alarm where there is little harm in restarting (the detection systems have gotten better, but we did a study during the 777 development on fire warnings - the number of false alarms was roughly the same as the number of actual engine fires).
OTOH, if you had to fire both bottles to eliminate the fire warning, restarting that engine could well just make things worse.