In 15k sep over 40 years;
Engine no response from pfl, ended up in a field with my instructor on basic flight training.
Dropped valve, put a/c down in a field.
Engine trying to stop at altitude, landed and engine caught fire, carb fault.
Section of piston broke off in c152, quick landing as i rejoined airfield.
Holed cylinder and short cct and landing.
Then nothing for the last 20 years until;
Recently cracked cylinders requiring quick landings.