What happened
On 20 February 2000, a Yakovlev YAK-50, registration G-BWYK, was being prepared for flight at North Weald Airfield, Essex. The pilot had completed preparations for start-up and intended to taxi to the airfield's live side for refueling. As part of the standard procedure to check for hydraulic lock, the pilot manually pulled the propeller through nine blades.
After returning to the cockpit to prime the cylinders with fuel, the pilot began pulling the propeller through to compression. During this process, the engine unexpectedly ignited. The sudden movement of the propeller caused the pilot to be struck on his right elbow, which knocked him off his feet. As he fell, he was struck a second time on his upper right thigh, resulting in significant injuries.
The investigation
The investigation was based on an accident report submitted by the pilot. It was established that the pilot had set the parking brake but had failed to verify the position of the magneto switch before proceeding with the manual start. Upon the arrival of assistance, it was confirmed that the magnetos were in the 'on' position.
Findings
- The pilot sustained serious injuries, including a broken femur, a severe open wound, and abrasions to the head.
- The engine ignited because the magnetos were left in the 'on' position during the hand-propping process.
- The Yakovlev YAK-50/52 lacks an idle cut-off mixture control, meaning the engine must be stopped by switching off the magnetos.
- Despite extensive flying experience, the pilot omitted the critical check of the magneto switch position before pulling the propeller.