What happened
On 13 August 2005, a Mooney M20J, registration N201YK, was conducting a private local flight originating from Archerfield. During the flight, the pilot noted that the engine began running roughly as the aircraft approached the airfield. Shortly thereafter, smoke emerged from the engine compartment, accompanied by the smell of smoke within the cockpit.
In response to the deteriorating engine performance, the pilot diverted the aircraft toward a large field adjacent to the airfield, which was deemed suitable for an emergency landing. Before the aircraft could reach the airfield, the engine suffered a total failure. The pilot deployed the flaps and landing gear and executed a forced landing in the field. The aircraft touched down more than halfway into the field and came to a stop after approximately 170 metres. There were no injuries to the pilot, and the airframe sustained no damage.
The investigation
The AAIB investigated the circumstances surrounding the engine failure and the aircraft's maintenance history. The investigation revealed that the aircraft had been out of service for approximately three years prior to the incident. During this period of storage, there was no documented evidence in the engine logbooks of essential preventive maintenance, such as periodic ground running or engine inhibition.
While the pilot initially suspected a loss of oil due to a hole in the crankcase, subsequent information suggested a more significant internal failure. Specifically, evidence indicated that the crankshaft had failed, causing a connecting rod to penetrate the crankcase. The AAIB intended to perform a metallurgical examination of the engine; however, the engine had been shipped to a supplier in the United States before the investigation could take place.