What kind of fire???
Are we talking an engine fire, or a cabin fire, or what???
"17 minutes and the aircraft will be rendered useless...."
Certainly, we've seen this with cabin fires, electrical fires in the cabin, etc., but not with unextinguishable engine fires.
The Air Canada DC-9 that landed in CVG proved this...If I remember correctly, from the time the lavatory fire was discovered until the time they landed, was 20 minutes....and, this turned out to be too long.
Can anyone cite an instance where the engine fire was unextinguishable, and the aircraft burned up inflight, causing it to crash, etc., etc? I can't recall, but perhaps someone can.
The basic premise of having a takeoff alternate (in the event that weather minima preclude a return for landing) takes into account these things....
1. If some pregnant woman in the back has her water break....go to takeoff alternate.
2. If an engine fails (on a twin-engine aircraft), go to takeoff alternate.
3. If an engine is on fire...extinguishable or unextinguishable...go to takeoff alternate.
4. If you have some other type of uncontrollable fire that will, in the opinion of the commander, threaten (with time the main consideration) the safety of the aircraft...for example, an unextinguishable galley fire, or an unextinguishable cabin electrical fire, or an unextinguishable lavatory fire, etec., etc., AND YOU KNOW IF YOU PROCEED TO YOUR TAKEOFF ALTERNATE, YOU WON'T MAKE IT IN TIME, do what you must do.
However, I, again, ask, when has there ever been an unextinguishable engine fire (except for maybe on something like a twin Cessna...I don't know) that caused the aircraft to burn up? (This is not a rhetorical question. I really want to know.)
Some aircraft, today, are capable of doing single-engine auto-lands, and certainly this is a consideration. But, this is for an ILS. What if your departure airport has only a VOR approach (or, worse yet, only an NDB approach)?
So, you take off from an airport that has only a VOR approach...the weather is below landing minima for that approach...but the weather is above takeoff minima. You take off, but with a takeoff alternate.
I'd hate to attempt a single-engine approach and landing to an airport with only a VOR approach with weather below minima for that approach...unless I had no other alternative....that is, unless I knew we wouldn't make it to the takeoff alternate.
Yes, it's true, the commander can deviate from any and all rules as he feels necessary to safely get the aircraft on the ground in the event of an emergency.
PantLoad