History of the Flight
After a normal departure from Isle of Man Airport, the aircraft was climbing through FL60 when the pilot heard an unusual noise and the right engine suddenly lost power. The pilot identified the failure from the right yaw of the aircraft and decided not to set full power on both engines due to the noise from the right engine. He shut down the right engine and carried out an uneventful landing. The pilot reported no difficulty flying on the left engine. All engine indications had been normal during takeoff and climb, with power set at 35 inches manifold pressure, 2,400 rpm, and mixture at 30 USG/hour.
Aircraft Examination
The left forward section of the right engine cowling had split apart, revealing that the No 2 cylinder had detached from the engine but remained within the cowling. The left side of the cowling was coated in oil. The failed end of the connecting rod had been crushed in subsequent impacts with the piston while the engine continued to turn. The big end of the connecting rod was still securely attached to the crankshaft.
Maintenance History
The failed engine was a Lycoming LTIO-540-J2BD six-cylinder piston engine, last overhauled by the manufacturer in April 1998, accumulating 1,744 hours at failure (TBO 1,800 hours). The No 2 cylinder had been replaced on 3 November 2006 at 1,280 engine hours as a cylinder kit due to a worn exhaust valve guide, and had accumulated 464 hours at failure. Two WDC numbers on the crankcase indicated a repair by an FAA-approved facility between 1995 and 1997; no further records were available.
Engine Examination
Six of the eight studs retaining the No 2 cylinder had failed in overload, and two had stripped from the casing. The small end of the No 2 connecting rod had failed. The No 2 piston was seized inside the cylinder; a force of 2,000 lb was required to free it. The piston appeared to have seized due to distortion from multiple impacts from the failed connecting rod, with a large piece of the sidewall broken off. All three piston rings were broken in half. No evidence of overheat distress was found on the piston sidewall or cylinder bore. The piston gudgeon pin and connecting rod small end inner surface were in good condition.
Analysis
The engine manufacturer stated that similar cylinder separations had been seen, often resulting from insufficient or excessive torque on hold-down nuts, or improper crankcase weld repairs. The manufacturer had not approved weld repairs, but the FAA had approved several facilities for such repairs, including the one that had performed an unspecified repair on this crankcase. The manufacturer indicated that a potential consequence of a weld repair near a cylinder is softening of the hold-down pad area, leading to loosening of nuts. The No 2 cylinder had accumulated 464 hours; if torque were incorrect, failure might occur sooner or later. Visual examination of the crankcase near No 2 cylinder did not reveal obvious evidence of welding. A further inspection was tasked but results were not received at publication. There was insufficient evidence to determine the cause of the cylinder separation.