What happened
On 13 May 2009, a Piper PA-31-350 Navajo Chieftan, registration G-VIPW, was performing a private flight departing from Isle of Man Airport. During the initial climb, while passing through 6,000 feet, the pilot heard an unusual noise and experienced a sudden loss of power from the right engine.
Recognizing the failure via the aircraft's yaw, the pilot maintained a safe airspeed of 130 KIAS and elected not to attempt full power settings. The pilot proceeded to shut down the right engine, which included feathering the propeller, though the propeller remained unfeathered. The pilot subsequently completed an uneventful landing back at Isle of Man Airport with no injuries to the crew.
The investigation
An investigation by the AAIB examined the aircraft and the Lycoming LTIO-540-J2BD engine. The examination of the right engine cowling revealed that the No 2 cylinder had detached from the engine block but remained trapped within the cowling. The investigation found that six of the eight studs responsible for securing the cylinder had failed due to overload, while the remaining two had been stripped from the casing.
Further inspection of the engine internals revealed that the small end of the No 2 connecting rod had failed. The piston had also seized within the cylinder, requiring significant force to dislodge. The investigation also noted that the engine crankcase had previously undergone a repair at an FAA-approved facility between 1995 and 1997.
Findings
- The failure was caused by the separation of the No 2 engine cylinder from the engine block.
- The small end of the No 2 connecting rod had failed, and the resulting impacts caused damage to the engine crankcase.
- While the engine manufacturer noted that improper torque on hold-down nuts or unauthorized crankcase welding can lead to cylinder detachment, the investigation could not definitively determine the exact cause of the stud failure.
- The engine had accumulated 1,744 hours since its last overhaul, nearing its 1,800-hour TBO limit.