What happened
On 7 November 2009, a Vans RV-8, registration G-XSEA, was performing aerobatic manoeuvres when the pilot noticed the engine oil pressure warning light illuminate. Shortly after, the engine began to run roughly as oil pressure plummeted from normal levels to between 3 and 7 psi.
At the time of the failure, the aircraft was approximately 3 nautical miles from its home strip, flying at an altitude between 1,200 and 1,500 feet. To avoid landing in a field, the pilot opted for a downwind glide approach to land uphill at High Easter Airfield. During the approach, the aircraft crossed a hedge at the runway threshold at a speed roughly 15 knots above normal approach velocity.
As the pilot attempted to avoid a hedge and ditch the aircraft at the end of the runway, the left landing gear ran off the grass strip and sank into a cultivated field. This caused the gear to break away, and the left wingtip and propeller struck the ground, bringing the aircraft to a halt. The pilot sustained minor bruising.
The investigation
Investigators examined the engine's oil system, which was designed to support unlimited inverted flight. The system utilizes a gravity-operated shuttle valve to direct oil from either the sump or the breather port to the high-pressure pump, depending on the aircraft's orientation.
Data retrieved from the electronic flight and engine instrument system confirmed that the pressure drop occurred during the aerobatic manoeuvre. An inspection of the engine showed that all oil remained in the sump, with no evidence of external leaks or oil contamination in the crankcase breather vent.