History of the Flight
The aircraft, a Yak-52 registered G-YKYK, was on a private flight to practise formation and tactical fighting manoeuvres with three other similar aircraft. Weather conditions were fine with clear skies, a westerly wind, and a surface temperature of 15°C. The pilot was flying straight and level at 1,500 ft en route to the intended practice area when the engine lost power; the propeller slowed but continued to windmill.
The pilot handed control of the aircraft to the rear seat pilot while he carried out a number of checks within the cockpit in an attempt to recover power. Pumping of the fuel primer gave a short burst of engine power once or twice, but there was no continued response. The pilot resumed control and prepared to make a forced landing; the rear seat pilot made a radio transmission to one of the accompanying aircraft advising of the situation.
The pilot selected a field for the forced landing and lowered the flap. The landing gear remained in the UP position, as recommended in the Pilot’s Standard Operating Notes. (On this aircraft type the landing gear does not retract fully when it is UP.) At about 50 ft agl the pilot selected the magnetos to OFF. The propeller struck the ground in a ploughed field just before the chosen landing field, and the landing gear made contact with the surface in the field margin. The aircraft continued ahead and came to rest some 140 metres into the field. The rear seat pilot turned the fuel OFF while the pilot made a radio transmission to advise the other aircraft of a safe landing; this transmission was not received. Neither pilot was injured.
Post-Accident Examination
Post-accident testing of the aircraft systems and the engine showed that the magneto system was faulty. This appeared to be due to a broken accessory drive shaft within the engine; the precise reason will be determined when the engine is stripped down for overhaul. A driveshaft problem of this nature has not been experienced before with the UK based YAK-52 aircraft.
Damage
The aircraft sustained damage to the propeller and trailing edge of flaps.