N4085TRobinson Helicopter R22 BETA · 1991

The solo student helicopter pilot reported that he was practicing takeoffs and landings to a taxiway, and that he was preparing for a steep approach. The steep approach required more left pedal, which resulted in the helicopter being "out of trim (right yaw)". A tailwind accelerated the right yaw. He attempted to recover, but added "insufficient left pedal", the helicopter spun, and landed hard. The helicopter came to rest on the left side.

The helicopter sustained substantial damage to the windshield, fuselage, and tailboom.

The student pilot reported that there were no preaccident mechanical failures or malfunctions with the helicopter that would have precluded normal operation.

The automated weather observation station located on the airport reported that, about 34 minutes before the accident, the wind was from 290° at 3 knots. The same automated station reported that, about 26 minutes after the accident, the wind was from 030° at 6 knots. The helicopter was approaching a taxiway parallel to runway 17.

Federal Aviation Administration's Helicopter Flying Handbook, FAA-H-8083-21A, contains a section titled "Weathercock Stability" which stated:

In this region, the helicopter attempts to weathervane, or weathercock, its nose into the relative wind. Unless a resisting pedal input is made, the helicopter starts a slow, uncommanded turn either to the right or left, depending upon the wind direction. If the pilot allows a right yaw rate to develop and the tail of the helicopter moves into this region, the yaw rate can accelerate rapidly. In order to avoid the onset of LTE in this downwind condition, it is imperative to maintain positive control of the yaw rate and devote full attention to flying the helicopter.