What was found
(CAN) DURING CRUSE FLIGHT AT 400FT. PILOT HEARD A LOUD 'BANG' A/C BEGAN TO VIBRATE AND THERE WAS A POWER LOSS HOWEVER THE ENGINE WAS STILL RUNNING. A/C WAS LANDED WITH NO SUBSEQUENT DAMAGE AND ENGINE SHUT OFF. ON INSPECTION IT WAS DISCOVERED THAT SOMETHING IN NUMBER FOUR PISTON HAD FAILED CAUSING A HOLE TOPOF THE CRANKCASE. ENGINE WAS REMOVED AND WILL BE SENT TO A OVERHAUL SHOP FOR FUTHER INVESTIGATION.