OK. What about an APU fire warning 2 hours into the cruise?
I had one about an hour after takeoff in a 727. (For you 72 drivers here I'll bet you already know what happened.) We were at cruise and the fire bell sounded, my well meaning and just out of recurrency school co-pilot immediately canceled the bell. Well, no real problem I guess, except no fire light was illuminated on the fire warning panel on the instrument panel.
So my co-pilot and the FE are staring at the fire panel waiting for a fire light to illuminate. To be honest it has not sunk in yet on what has happened to me either. I tell the co-pilot to test the fire system to see if any of the bulbs had burned out, very doubtful as with dual bulbs in the lights, he does and all the lights illuminate.
Hum I think, then 'click' in my mind. I look back at the APU control panel and yep, sure enough the APU fire light is on and the APU is still running. I make sure that essential power is not being power by the APU and inform the FE that he left the APU on and to shut it down.
His immediate response was, "I turned it off before takeoff!" I replied that if so, we just had the first auto-start of an APU in Boeing history. So then he grabs the start-run switch and places into off. Of course nothing happened because the gear is up. As I am explaining this to the FE, the co-pilot grabs the throttles and starts to pull the power off. I, being an inquisitive type of person, inquired as to why he was reducing power. He replied that he was slowing down so we could put the gear down.
At this point I don't whether to laugh or cry.
Very patiently I explained to the two of them that we do not have to put the gear down (not that it would have helped to put the gear down anyway, as the APU control for the start-run control panel is on the squat switch), to put the power back to cruise and for the FE to pull the APU fire handle and see if the light goes out. He did, it did and we carried on.
When we landed the APU started and ran just fine. As there never was a fire, just an overheat condition. And yes, I inspected the APU before we started it after we landed.
To be fair, in training we had always been taught that the first indication of the APU being left on was a 'Wheel Well' fire warning, but obviously not always the case.
Oh, when we got back to home base I told the Chief Pilot that we needed to go back to the Dalfort (Braniff) school, as the new one was not doing a very good job.