Aircraft Information
The accident involved an Aerostar SA Yak-52, registration G-BVMU, serial year 1994. It was powered by a single Ivchenko Vedeneyev M-14P piston engine. At the time of the incident, the aircraft was being operated on a private flight.
History of the Event
On 17 August 2001, at approximately 1700 UTC, a 54-year-old private pilot (647 total hours, 2 on type) had just completed two conversion training sorties with an instructor at Little Gransden. The aircraft was refueled for the pilot's first solo flight to Shipdham Airfield. The pilot initially declined the instructor's offer of assistance but later accepted. He told the instructor that the magneto switches in the rear cockpit were ON, and the instructor reminded him to ensure the front cockpit switches were OFF.
The pilot primed the engine, and the instructor called out the starting checks: "Brakes ON, Air ON, Mags OFF." The pilot confirmed these settings. The instructor then began turning the propeller by hand. After pulling through about six blades, the engine fired and continued running. The propeller struck the instructor's right hand, causing a serious injury. The pilot shut down the engine and vacated the aircraft to assist.
Conclusions
The pilot could not be certain what caused the engine to start, but he listed several possible factors: the front cockpit magneto switches might have been left ON after the previous shutdown; he might have switched them ON instead of OFF due to unfamiliarity with the clockwise-off configuration (compared to American switches); or the engine might have fired due to compression while still hot from the previous flights. The instructor noted that it was unlikely the cylinder head temperature exceeded 70°C.
The instructor reported hearing the starter solenoid open as he was turning the propeller, implying that the pilot had pressed the Start button, which would have initiated the "shower of sparks" ignition mechanism. However, the pilot was adamant that he had not pressed the Start button.
Investigators were unable to determine the exact mechanism that caused the engine to fire. However, once it fired, the engine could only have continued running if both front and rear cockpit magneto switches were ON.
The aircraft sustained no damage, and the pilot was uninjured.