Accident Overview
On 14 February 1994, at approximately 1410 local time, a Piper PA-28-181 Archer, registration HB-PLS, operated by Motorfluggruppe Thun, was involved in an accident at Thun airfield. The aircraft was being used for a private training flight.
Preflight and Takeoff
During the preflight inspection, the pilot drained fuel from three designated drain points: the two fuel tanks and the strainer located on the left side of the engine cowling. No anomalies were noted. The takeoff from runway 32 was normal.
Engine Failure and Emergency Landing
As the aircraft was climbing and approaching the end of the runway, the engine suddenly stopped. The pilot immediately pushed the nose down and turned right to perform an emergency landing in open terrain. Near the ground, the aircraft stalled. Initial ground contact was with the right main landing gear and the right wing tip, followed by the nose wheel and propeller. The aircraft slid for approximately 40 meters before coming to rest about 120 meters to the right of the runway centerline.
Damage and Injuries
The aircraft sustained severe damage to the wings, landing gear, propeller, engine, and forward fuselage. There was minor ground damage. The pilot, who held a valid private pilot license with 481 hours total flight time (122 on type), was uninjured.
Investigation Findings
Examination revealed fuel residue on the left side of the fuselage and left horizontal stabilizer. The area of the strainer drain was damaged in the impact, but traces on the engine cowling indicated that the drain had been open at the time of the crash. A similar incident involving the same aircraft had occurred on 14 December 1988, where after takeoff the engine failed due to an open strainer drain. Tests on an aircraft of the same type demonstrated that with the strainer drain open during climb at full power, the engine would stop after approximately 30 seconds.
Fuel quantity after the accident was measured at 12 gallons in the left tank and 14 gallons in the right tank; the tank selector was positioned to the left. Both the mechanical fuel pump and the boost pump functioned normally.
Probable Cause
The accident was due to the pilot leaving the strainer drain open during the preflight check and exceeding the minimum lift speed during the emergency landing after an engine failure shortly after takeoff.