Enemy Plane Damage

[Flanker15]

This does remind me of what often happened in Il-2 when attacking bombers.
During the attack you'd catch one or two bullets in the engine from the bombers tail gunners which you might not even notice. The hits would cause damage to the fuel line, oil line, radiator or another component of the engine. After a while the engine would start to fail as it over heated or something and you'd eventually lose too much airspeed and crash quite a while after the origonal hit.
There was usually a weird grinding noise from the engine as it started to fail or some light smoke/fuel vapor/oil but sometimes there was no warning until you started to lose engine RPM.
Presuming the engine damage model is as good as in PC Il-2 it could be this or you could just be running the throttle at 100% for too long.
After you disengage from a battle, check the oil pressure, fuel gage and engine temp for any problems.