whereas if you only have a tailpipe you wouldn't have any indications at all?? Correct?
Not correct, the crew, if monitoring on shutdown
, would see a rise in EGT, on most engines I know, the EGT thermocouples are at the back and would indicate a rise in temperature due to the fire in the back.
Is a tail-pipe fire a bit like a combustion engine back-firing, with unburnt fuel getting through to the exhaust?
Sort of but not quite, it is fuel in the exhaust for whatever reason, a backfire in a combustion engine is something different, this would probably equate to a surge in a Gas Turbine engine.
