Flight Event
During flight, the pilot heard and felt a bang from the right side of the airplane. He observed that the right engine nacelle had a hole and the engine was on fire. The pilot secured the engine and diverted to a nearby airport. While on final approach for landing, the engine fire reignited. After landing, the pilot taxied clear of the runway, shut down the left engine, and egressed. The engine fire continued to burn, consuming the right engine and a majority of the fuselage.
Examination
Post-incident examination revealed that the right engine's No. 2 cylinder was displaced from the engine case but remained attached via the injector manifold vent tube and injector lines. All eight of the No. 2 cylinder's attach bolts were broken off at the case. The connecting rod cap was found lodged in the bottom of the piston. One connecting rod bolt was broken off flush in the connecting rod; the top portion was not located. The other connecting rod bolt remained in the connecting rod cap with the nut also not located. One side of the lower connecting rod flange was bent back towards the piston, capturing the nut and the remaining portion of the broken bolt. Neither bearing half could be identified in the remaining material. Numerous impact marks were noted on the piston, cylinder, and case.
Maintenance Records
A review of maintenance records found that the engine was last overhauled about 4½ years before the incident and had accrued about 900 hours since that overhaul.
Probable Cause
Based on the available information, it is likely that the nut that secured one side of the connecting rod cap became loose, resulting in the separation of the cap and subsequent damage to the No. 2 cylinder. Since the nut could not be located, the reason it did not remain secure could not be determined.