Robinson Helicopter R22 BETA N1152W accident near Farmington, Connecticut

Probable cause

The pilot's inadequate compensation for wind during a high-power, low-speed downwind turn, which resulted in a loss of control due to loss of tail rotor effectiveness and settling with power. Contributing to the accident was the pilot’s decision to land downwind.

NTSB analysis

The helicopter slowed as it approached the landing zone on a modified right-base turn to the north. Gusting wind from the south had prevailed for most of the day and was present at the time of the accident. As the pilot turned to "enter the landing area," he felt a “bump” in the tail rotor control pedals. The pilot added that he applied left pedal to compensate for a right yaw, and the helicopter immediately "started to rotate" at an increasing yaw rate with full left pedal applied. The pilot stated that the rotation stopped when he pushed the collective control "full down" and applied aft cyclic. The helicopter then descended through the trees and collided with terrain. Examination of the wreckage revealed no evidence of pre-impact mechanical anomaly.

U.S. Army guidance listed high gross weight, high-density altitude, low indicated airspeed, power droop, and right downwind turns as factors that may contribute to a loss of tail rotor effectiveness (LTE) and described vortex ring state, or settling with power, as a condition in which the helicopter loses lift and settles in its own downwash. Federal Aviation Administration (FAA) guidance cautioned pilots to remain vigilant to power and wind conditions and stated that low airspeed, out-of-ground-effect (OGE), and high-power-demand flight conditions were conducive to LTE. Additionally, FAA guidance described unanticipated right yaw in helicopters, or LTE, as a critical, low-speed aerodynamic flight characteristic, which could result in an uncommanded rapid yaw rate that does not subside of its own accord, and, if not corrected, could result in a loss of aircraft control. When operating at airspeeds below effective translational lift, pilots should avoid OGE hover and high-power demand situations, such as low-speed downwind turns. Contributing factors for LTE include high gross weight/high density altitude, low indicated airspeed, power droop, and right downwind turns. Therefore, the pilot’s performance of a high-power, low-speed downwind turn during gusting wind likely caused the LTE.

Text from the NTSB. Open the NTSB docket for ERA12LA282 for the full record.