Accident Overview
On November 17, 2020, a Piper PA-11, registration LV-YNN, operated by Aeroclub Luján, departed from Luján aerodrome for a general aviation training flight. About twenty minutes into the flight, after completing a simulated emergency procedure, the pilot attempted to apply power but received no response from the engine. The flight instructor took control and executed a forced landing in an unprepared wheat field near Open Door, Buenos Aires. After touchdown, the aircraft traveled 19 meters before the main landing gear wheels became entangled in the wheat, causing the nose to dip, the propeller to strike the ground, and the aircraft to capsize. The accident occurred in daylight under good weather conditions.
Investigation Findings
A visual inspection of the aircraft revealed a defect in the throttle cable. The outer sheath of the cable had broken due to contact with the engine exhaust. The sheath was not properly secured, resulting in friction and subsequent wear. When the throttle control was moved, the sheath would open and the cable would come out sideways, preventing effective transmission of motion. Repeated attempts to operate the throttle produced no response.
Maintenance records indicated that the aircraft was equipped in accordance with current regulations and procedures at the time of the accident. However, it could not be determined whether the throttle command was properly secured after the last inspection or if subsequent work affected its fixation.
The aircraft was assigned to Aeroclub Luján, a Type III Civil Aeronautics Instruction Center (CIAC) based at Luján aerodrome. At the time, the CIAC had five aircraft and four qualified instructors.
Analysis
The investigation determined that the engine's failure to deliver power upon demand was caused by the throttle movement not being transferred to the carburetor butterfly. This resulted from the absence of clamps on the throttle control cable, which allowed engine vibrations to wear and cut the sheath protecting and guiding the cable to the carburetor. The sheath rupture prevented effective throttle input.
Conclusions
- The engine did not deliver the required power after a simulated emergency, preventing the aircraft from maintaining its flight path.
- The instructor took control and performed a forced landing in an unprepared wheat field.
- During the landing roll, the aircraft capsized because the wheat became entangled in the main landing gear wheels.
- The throttle cable installation lacked clamps, causing the sheath to rub against the engine exhaust pipe.
- The sheath protecting and guiding the throttle cable experienced a rupture that prevented effective cable movement when the throttle was operated.
- Contact with the exhaust pipe and engine vibrations caused the sheath to cut.