Incident Description
On 26 September 2019, at approximately 14:45 UTC, a Piper PA-11 aircraft, registration LV-YQF, was parked at Ezpeleta Aerodrome, Buenos Aires. The aircraft was being prepared for a local instructional flight with an instructor and a student on board. During the engine start procedure, the student stood in front of the aircraft while the instructor was seated in the rear cockpit. The student manually rotated the propeller to engage the magnetos and start the engine. The first attempt failed. According to the instructor, the student then attempted to reposition the propeller by turning it in the normal direction of operation without first ensuring that the magnetos were off. The instructor tried to alert the student, but the engine started, and the propeller struck the student’s left leg. The student reported that he had intended to turn the propeller in the opposite direction, as he had done in a previous lesson. The incident occurred in daylight under good weather conditions.
Injuries and Damage
The student sustained a minor cut on his left leg. The impact was partially attenuated by a mobile phone he carried in his left trouser pocket. The propeller blade sustained damage. After the incident, the student received medical attention at a nearby hospital.
Operational Context
The aircraft was assigned to an aero club and used for flight instruction under Argentine Civil Aviation Regulations (RAAC) Part 141. The aero club was in the process of adapting to obtain its corresponding certificate at the time of the incident. The club had developed a checklist for normal procedures based on another aircraft of the same model, which was used for the LV-YQF operation. The checklist only contemplated the procedure with the pilot inside the cockpit for engine start. The aircraft’s flight manual included procedures for before starting the engine (chock wheels or apply brakes) and for cases where the engine does not start (turn ignition key to off).
Investigation Findings
Interviews with both the instructor and the student were conducted. The instructor stated that the procedure began with verifying that the aircraft was "contact on, throttle reduced, and brakes set." After the first unsuccessful start attempt, the student moved the propeller without confirming that the magnetos were off. The student’s account differed: he indicated he turned the propeller in the opposite direction to prepare for a second attempt, as he had practiced before. The investigation noted that the mobile phone in the student’s pocket reduced the severity of the injury.