What happened
On 4 August 2020, a Hawker Sea Fury T Mk.20, registration G-INVN, was conducting a second post-maintenance test flight near Duxford when the engine suffered a sudden failure. The flight, which included a passenger, proceeded normally through various maneuvers until the aircraft was near Cambridge. The pilot then observed a rapid rise in engine oil temperature, followed by fluctuating oil pressure.
As the engine began to run roughly and emit smoke, the engine speed surged significantly beyond takeoff limits before the engine eventually seized. The pilot, facing a rapid descent and limited options, performed a forced landing in a ploughed field near Harston, Cambridgeshire. During the landing, the aircraft struck the ground, bounced, and slid into a hedgerow, causing the airframe to break into three sections. Both the pilot and the passenger sustained serious injuries, specifically broken vertebrae.
The investigation
The AAIB examined the wreckage and the engine components to determine the sequence of failure. Investigators found extensive internal damage within the Pratt & Whitney R2/800-CB3 radial engine. Specifically, the investigation identified a breakdown in the rear master rod bearing. Analysis of the oil and filter elements revealed various metallic particles, including aluminium, silver, lead, indium, and iron.
While the investigation could not pinpoint the exact moment the damage began, it noted that smoke was visible from the exhaust during the morning's takeoff, suggesting the engine was already exhibiting symptoms of distress. The investigation also reviewed the pilot's actions, noting that his simulator training and prior mental rehearsal of emergency procedures were instrumental in maintaining control of the aircraft during the descent.
Findings
- The engine failure was caused by the failure of the rear master rod bearing.
- The breakdown of this bearing released debris and increased friction, which overwhelmed the oil cooling system.
- Contamination of the oil system was identified as the most likely cause of the initial bearing damage.
- The pilot's decision to maintain airspeed and select an appropriate landing site prevented more severe consequences.