What happened
On May 1, 2016, a Robinson R22 Beta helicopter, registration PR-YMO, was conducting a low-altitude observation flight over the municipalities of Viamão, Alvorada, and Gravataí in Rio Grande do Sul, Brazil. The flight, which began at Belém Novo Aerodrome, involved a pilot and one passenger.
Approximately 35 minutes into the flight, while performing an out-of-ground-effect (OGE) hover at an altitude of approximately 200 feet over a rural area in Viamão, the aircraft experienced a sudden change in aerodynamic conditions. The pilot reported feeling a gust of wind accompanied by immediate vibrations in the pedals. The aircraft subsequently entered a right-hand spiral descent, losing directional control. The pilot attempted to execute a go-around by reducing the collective; however, due to the low altitude, the aircraft struck the ground in a grassy area of a farm.
The impact caused substantial damage to the Robinson R22 Beta, including a broken windshield, a damaged right skid, and deformation of a main rotor blade. The pilot sustained serious injuries, including two fractured vertebrae and a fractured pelvis, while the passenger sustained minor injuries.
The investigation
CENIPA's investigation focused on the aerodynamic phenomena occurring during the hover and the pilot's response. Investigators analyzed meteorological data, which indicated a prevailing northwest wind at approximately 7 knots. The investigation established that the aircraft's position relative to the wind—specifically a tailwind component—caused airflow to strike the vertical stabilizer and the tail rotor blades, leading to Loss of Tail Rotor Effectiveness (LTE).
The investigation also reviewed the pilot's experience and adherence to manufacturer safety protocols. While the pilot held valid licenses and medical certification, they had relatively low recent flight frequency, with only 2.5 hours of flight time in the preceding 90 days. Furthermore, the investigation compared the pilot's actions against the Robinson Helicopter Co. Safety Notice (SN-34) and the R22 Pilot's Operating Manual, which provide specific emergency procedures for tail rotor loss of effectiveness.
Findings
- The aircraft was positioned with the tail facing the wind, creating conditions conducive to LTE.
- The pilot's decision-making and piloting judgment were inadequate for the specific risks of OGE hovering in these wind conditions.
- The pilot attempted a go-around maneuver that was not possible given the insufficient altitude remaining.
- The pilot did not strictly follow the established emergency procedures for managing tail rotor loss of effectiveness, such as reducing power immediately to minimize torque.