What happened
On June 12, 2012, a Piper J3/C-65/L-4, registration HB-OIA, was conducting a flight for the purpose of a pilot competency revalidation. The flight, which included a flight examiner, was intended to include a mandatory simulated emergency landing as part of the training program.
During the flight, the pilot initiated the simulated emergency landing procedure by reducing engine power to idle. After a period of gliding, the pilot attempted a go-around by applying full power. Approximately ten seconds into the climb, the engine suffered a complete loss of power. Facing high-voltage power lines roughly 200 meters ahead, the pilot executed a 180-degree left turn. The aircraft subsequently performed a heavy landing on a grassy field, causing the right landing gear to collapse. The aircraft slid into an adjacent cornfield, sustaining significant damage to the airframe, engine, and propeller. The two occupants escaped without injury.
The investigation
SUST examined the technical condition of the aircraft, the meteorological environment, and the actions of the crew. Investigators analyzed the fuel used, noting that while the main tank fuel met standards, the fuel in the wing tank contained volatile components that did not meet requirements. The investigation also reviewed the pilot's recent flight history, noting that neither the pilot nor the examiner had flown this specific aircraft type for over a year.
Technical inspections of the carburetor and engine found no mechanical defects that would directly cause the power loss. However, investigators performed tests simulating the closing of the fuel valve to see if it could replicate the engine failure. They found that closing the fuel valve led to an engine shutdown after a short period, mirroring the timing of the accident.
Findings
- The primary cause of the accident was a hard landing following a loss of engine power.
- Carburetor icing is considered a highly probable cause due to the prevailing weather conditions, which included high humidity and a low cloud base, combined with the use of automotive gasoline.
- A pilot error involving the accidental closing of the fuel cock instead of the carburetor heat control cannot be ruled out, especially given the lack of recent experience with the aircraft type.
- The use of automotive gasoline instead of aviation gasoline increased the risk of carburetor icing.
- The aircraft was operating at approximately 605 kg, which was 25 kg above its maximum takeoff mass of 580 kg.
- The collapse of the right landing gear was caused by the heavy impact forces during the landing.