What happened
On 17 March 2017, a Pitts S-2A aircraft, registration G-SKNT, was performing a short flight from Rednal to Sleap as part of a scheduled annual maintenance check. During ground operations, the pilot noted that while the engine appeared to be running normally, the oil pressure was fluctuating and slow to rise. These fluctuations persisted during the initial climb.
Shortly after takeoff, the indicated oil pressure dropped to zero, although engine temperature readings remained within the normal range. The pilot notified RAF Shawbury of his intention to return to Rednal due to a potential engine failure. During a turn, the engine began to vibrate and lose power, eventually ceasing to produce power entirely at an altitude of approximately 1,200 ft agl.
Unable to reach the runway, the pilot executed a forced landing in a wheat field near Cockshutt, Ellesmere. During the touchdown, the left wingtip and aileron spade struck an undulation in the ground, causing the aircraft to come to rest in an inverted position. The pilot sustained minor injuries and was able to exit the aircraft via the canopy without assistance.
The investigation
Investigators examined the aircraft and the engine following the accident. A preliminary inspection of the engine was conducted to determine the cause of the power loss. The investigation focused on the sequence of oil pressure fluctuations and the subsequent mechanical failure of the engine components.