Originally Posted by
smarthawke
If the aircraft is used for flying training or private hire etc, it can continue to be run 'on extension' which is to 20% past TBO - so that is an additional 400 hours or 2.4 years (2400hrs and/or 14.4 years).
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At the Canadian flying school where I occasionally help out, Transport Canada has approved a TBO extension to 3500 hrs for the C 172. To date every engine has made it. Engines don't fail just because they are old and there is no reason not to keep running the engine until it tells you it is unhappy.
Of the 3 engines I know of that suffered catastrophic failures, 2 were less than 20 hours from overhaul. Both failures occurred because of assembly errors. The other one was operated by someone who thought all engine maintenance was optional
