What was found
PILOT REPORTED VIBRATION AFTER 2 HRS INTO FLIGHT, COULD NOT DETERMINE ORIGIN OF VIBRATION. ANOTHER PILOT PERFORMED GROUND RUN-UP AND COULD NOT DETECT VIBRATION. PILOT FLEW AIRCRAFT AND AFTER 15 MINUTES A VIBRATION OCCURRED, PILOT NARROWED VIBRATION ORIGIN TO LT ENGINE AND PERCEIVED A RT MAGNETO PROBLEM. AFTER LANDING, A MECHANIC RAN UP AIRCRAFT AND FOUND THE RT MAG ON THE LT ENGINE ROUGH. AFTER UNCOILING THE LT ENGINE FOUND NR 2 CYLINDER HAD SEPARATED FROM BARREL. ALSO FOUND ENG WOULD NOT IDLE BELOW 1400 RPM. (PTRS NR GL11200406248)