What happened
On 28 April 2021, a Hawker Sea Fury T Mk 20, registration G-RNHF, was conducting a private training flight near RNAS Yeovilton, Somerset. During the flight, the pilot noticed a drop in oil pressure and subsequently declared a PAN PAN call, turning the aircraft back toward the airfield.
As the aircraft was performing a base turn for landing on Runway 04, the Bristol Centaurus XVIII engine suffered a sudden and complete seizure. The failure was accompanied by violent vibrations through the airframe. Because the engine seized, the pilot was unable to feather the propeller, creating immense drag. This resulted in an extremely high rate of descent, making it impossible to reach the runway threshold. The aircraft struck a telegraph pole and a house before impacting the ground approximately 0.5 nm from the runway. While the aircraft was destroyed, both the pilot and the passenger managed to escape the cockpit without serious injury.
The investigation
The AAIB examined the wreckage and the engine components to determine the cause of the failure. The investigation revealed that the rear crankpin bearing had overheated, causing the white metal bearing layer to melt. This overheating led to the bearing sleeve spinning on the journal and caused liquid metal embrittlement (LME) of the rear master rod big end. The resulting cracks caused the master rod to fracture, leading to the destruction of the rear cylinder row components and the eventual seizure of the engine.
Investigators also reviewed the maintenance history and the availability of technical data. It was noted that the maintenance organisation lacked access to certain critical modification leaflets for the engine, which could have provided a more complete picture of the engine's modification status.
Findings
- The primary cause of the engine failure was the overheating of the rear crankpin bearing, which triggered a chain of mechanical failures including the fracture of the rear master rod.
- The suddenness of the engine seizure and the high rate of descent prevented the pilot from completing the emergency checklist or reaching the runway.
- The investigation could not establish the specific reason why the rear crankpin bearing initially overheated.
- There were difficulties in accessing essential technical modification data for this historic engine type.