What happened
On June 8, 2019, at approximately 21:00 hours, a Sport EIT2 aircraft, registration LV-X511, departed from the Belén de Escobar aerodrome in Buenos Aires for a general aviation test flight. The aircraft was being operated by its owner, who was conducting the first flight test of a recently installed in-flight variable-pitch propeller system.
During the initial climb, the pilot attempted a left turn at low airspeed. During this maneuver, the aircraft experienced a loss of thrust, leading to a loss of control and a subsequent impact with the terrain. The impact destroyed the airframe and the propeller, and the pilot sustained fatal injuries. The aircraft came to rest inverted approximately 140 meters northwest of the runway heading.
The investigation
The JST investigation focused on the mechanical integrity of the newly installed propeller system and the regulatory status of the aircraft. Investigators examined the propeller hub, discovering insufficient torque on the bolts connecting the hub body and a broken pivot bolt on one of the blades. Microscopic analysis of the damaged bolt revealed surfaces consistent with an overload of tension, with no evidence of progressive fatigue.
Technical examination of the control mechanism revealed that the propeller pitch control lacked stops to limit the angle between 0 and 90 degrees. Furthermore, the control cable sleeve was not properly secured to its mounting clamp at the time of the accident. This lack of securement rendered the control ineffective, meaning movements of the cockpit lever did not translate to the propeller blades. Due to aerodynamic and centrifugal forces, the blades likely moved toward a 0-degree pitch, significantly reducing thrust.
Findings
- The aircraft was not operating in compliance with current regulations, as the major modification to the propeller system had not been reported to the ANAC, which invalidated its airworthiness certificate.
- The propeller control system lacked mechanical stops to limit the pitch range.
- The propeller control sleeve was improperly secured, preventing effective operation of the pitch mechanism.
- The system lacked a way to lock the propeller at a specific pitch setting.
- The aircraft suffered a loss of thrust during the climb due to an uncommanded variation in propeller pitch.
- The pilot attempted a return turn to the runway without sufficient altitude, resulting in an aerodynamic stall and loss of control.