What happened
On 30 June 2008, a Denney Kitfox, registration G-BSSF, was conducting a local area flight near Humberside Airfield, Lincolnshire. The flight plan included a navigation exercise and a practice forced landing (PFL) before returning to Northmoor Airfield. The weather conditions were favorable, with good visibility and light winds.
After completing the navigation portion of the flight, the pilot notified air traffic control of the intention to perform a PFL. The pilot selected a suitable area and initiated a descent by closing the throttle. During the climb following the successful completion of the landing exercise, the engine suddenly ceased operation. The engine began running roughly with erratic RPM and severe banging noises, leading to a total loss of power. The pilot transitioned to a gliding attitude and issued a MAYDAY call.
Unable to find a suitable landing site other than a field covered in crops, the pilot selected a large cereal field. Using 5 degrees of flap to manage groundspeed, the aircraft touched down. After a ground roll of approximately 14 metres, the aircraft nosed over and came to rest in an inverted position. There were no injuries to the pilot or the passenger.
The investigation
Investigators examined the engine and found that oil levels and fuel supplies were sufficient at the time of the accident. The examination revealed that the crankshaft had failed approximately halfway along its length, specifically near the rotary valve shaft drive gear.
Records indicated that the Rotax 582 engine had been in use for 519 hours since its manufacture in 1990. While the owner was operating the engine 'on condition' and monitoring bearing wear, the manufacturer's maintenance schedule mandates a general overhaul—which includes a crankshaft replacement—after 300 hours of operation or five years.
Findings
- The engine failure was caused by a breakage in the crankshaft.
- The engine had exceeded the manufacturer's recommended 300-hour interval for a general overhaul.
- The failure was consistent with the service life and history of the engine components.