What happened
On 5 June 2013, a Piper PA-38-112 Tomahawk, registration G-BGBN, was conducting a circuit training flight at Cranfield Aerodrome. The flight involved an instructor and a student pilot. Following a touch-and-go landing on Runway 03, the aircraft began its climb. Shortly after liftoff, the engine began running roughly.
The instructor, attempting to manage the developing issue, initially considered returning to land on Runway 21. During a turn to the left intended to steer the aircraft toward a clear area within the aerodrome boundary, the engine power failed completely. The aircraft entered a stall, the nose dropped, and the plane crashed within the aerodrome perimeter, approximately 100 m from the threshold of Runway 21. The impact resulted in 2 serious injuries to the crew and the total destruction of the aircraft.
The investigation
The AAIB investigation examined the wreckage, the fuel system, and the engine components. Investigators found that the fuel selector was set to the right tank, and while trace amounts of ethanol were detected in the fuel, the primary supply was Avgas 100LL. The engine was partially stripped, and while the mechanical and electrical fuel pumps and the carburettor were found to be serviceable, the impact damage prevented a definitive conclusion regarding the specific cause of the initial rough running.
Investigators also reviewed the maintenance records of the flying school. They discovered that undocumented maintenance had been performed on the aircraft by an individual without the required Part 66 license shortly before the accident. Additionally, discrepancies were noted in the technical logs regarding flight hours and fuel quantities.
Findings
- The most likely cause of the engine's rough running was carburettor icing, as atmospheric conditions presented a significant risk of ice formation.
- The instructor's decision to execute a turn at low altitude with a failing engine contributed to the loss of control.
- The aircraft stalled and departed controlled flight because the turn was performed at a height insufficient for recovery.
- The aircraft had been subject to unauthorised maintenance by an unqualified individual.
- There were inconsistencies in the maintenance and flight logging practices of the operator.