What happened
On 23 May 2001, a Cessna F150L, registration G-AZLY, was conducting a training flight near Shildon, Durham. The flight, which originated from Teesside, was intended to be a one-hour session focused on practicing emergency procedures and drills. The crew consisted of an instructor and a student.
During the flight, the instructor demonstrated engine fire procedures and subsequently instructed the student to perform a practice forced landing. After selecting a suitable landing area and performing the necessary cockpit checks, the aircraft began its descent. As the aircraft transitioned to the final approach with 10° of flap extended, the instructor initiated a go-around to maintain clearance from rising ground. Upon applying full power to climb, the engine suffered a sudden and unexpected loss of power.
Following the engine failure, the instructor assumed control of the aircraft. After verifying that the fuel, mixture, and carburettor heat settings were correct, the crew identified an alternative landing site and notified Teesside Radar of their intentions. The aircraft landed in a field of wheat. Due to the dry ground, short crop, and an upward slope, the aircraft was brought to a stop before reaching a perimeter fence. There were no injuries to the crew and the aircraft sustained no damage.
The investigation
Technical examination of the Continental Motors O-200-A engine identified significant internal damage. Investigators discovered that both valves in the front left cylinder had failed, with fragments of the valves lodged in the piston. The investigation established that a failure in the stem radius of one valve head caused it to detach, which then struck and destroyed the second valve head.
Furthermore, the investigation found that the rear left cylinder was experiencing low compression due to a burnt exhaust valve. It was determined that this condition had likely been present for a period of time. The engine had surpassed 1,800 hours since its last overhaul and was nearing a scheduled 50-hour inspection.