What happened
On 31 May 2008, a Pilatus P2-05, registration G-BLKZ, was conducting a private flight from RAF Waddington to Spanhoe Airfield. After climbing to 2,000 ft and establishing cruise power, the pilot noted a slight vibration that rapidly escalated into heavy vibration. During this period, oil began leaking from the right-hand cylinder. Shortly thereafter, the engine ceased functioning entirely.
In an attempt to avoid power lines and uneven terrain, the pilot executed a slight left turn and lowered the flaps. During the descent, a piece of the engine cowling was displaced and struck the windscreen. The pilot performed a forced landing at Heath Farm, near Barkston Heath. Upon impact, the aircraft landed with a heavy, nose-down attitude, causing the landing gear to collapse. Both the pilot and the passenger sustained minor injuries and were able to egress the aircraft unassisted.
The investigation
An inspection of the Argus AS 410-A2 engine revealed a golf-ball-sized hole in the crankcase. Investigators discovered that parts of the crankcase were loose within the engine cowling. A subsequent examination by a maintenance organisation determined that both connecting rods on the third cylinder bank had failed. The failure originated at the gudgeon pin of the first rod, which subsequently caused the destruction of the second rod. While the pistons were found to be free to move within the cylinders, there was no evidence of lubrication failure; instead, some blueing on the crankshaft was attributed to the mechanical impact of the rods hitting the cylinder walls.
Findings
- The engine failure was caused by the failure of both connecting rods on the third cylinder bank.
- The initial failure occurred at the gudgeon pin of the first connecting rod.
- The engine type is known for requiring delicate handling and has a documented history of connecting rod and piston failures.
- The aircraft sustained substantial damage to the propeller, landing gear, and underside.