What happened
On April 29, 2018, a Robinson R44 II helicopter, registration PR-LNL, was performing a flight to balance the main rotor blades at the Aeródromo Nacional de Aviação (SBNV) in Goiânia, Brazil. The flight followed maintenance work performed to replace a cylinder in the engine due to low compression.
While returning to the hangar after the maintenance flight, the pilot performed a maneuver known locally as a "bailarina" (a 360-degree turn while maintaining forward movement). During this maneuver, as the aircraft encountered a tailwind, the rotation speed increased, leading to a loss of control. The helicopter struck the taxiway approximately 2 meters above the ground, resulting in substantial damage to the aircraft. The pilot and a mechanic on board were uninjured.
The investigation
CENIPA investigators examined the aircraft's mechanical condition and the engine's performance. The investigation confirmed that the pilot was properly licensed and medically certified for the operation. The aircraft's airworthiness certificates were valid, and all maintenance logs, including engine and cell records, were up to aeronavigation standards. All applicable Service Bulletins and Airworthiness Directives had been implemented.
To rule out mechanical failure, the engine was subjected to a 25-minute bench test. The engine operated normally at various RPM levels, including its maximum manufacturer-specified rotation, without any detected issues in fuel supply, ignition, or oil pressure. Furthermore, inspections of the main rotor blades showed that the damage was solely a result of the impact and not due to pre-existing structural defects.
Findings
- Inappropriate control inputs during the unauthorized maneuver.
- Errors in pilot judgment regarding the execution of the maneuver in tailwind conditions.