This vintage Russian-built Yakovlev Yak-50 (G-YAKK) lost all oil pressure while on a flight out of Carlisle Airport in northern England in April 2010. The pilot considers turning around to his origin, but as oil begins leaking into the cockpit, the engine seizes and stops turning, he decides to put her down in one of the countryside’s many large, flat fields, landing in the small village of Bothel.
The cause:
On examining the engine, the pilot identified that the oil pressure adjustment valve was missing from the oil scavenge pump housing (Figure 1). It was found in the lower cowling with no evidence of the expected wire locking. He believed that the valve had worked loose and fallen out during the accident flight, causing the oil loss. The aircraft had recently undergone extensive maintenance which included an overhaul of the oil scavenge pump assembly. Initial flights following this work revealed a small oil leak in the area of the pump, which at the time, was thought to be have been remedied by an engineer tightening the small vertical bolts adjacent to the pressure adjustment valve.
He seems uninjured in the video, but reportedly visited a hospital later for an undisclosed injury.
