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Aviation Accident

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NTSB Identification: GAA18CA508
14 CFR Part 91: General Aviation
Accident occurred Friday, August 24, 2018 in Corvallis, OR
Probable Cause Approval Date: 03/18/2019
Aircraft: Robinson R22, registration: N4085T
Injuries: 1 Minor.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

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 then spun and landed hard. The helicopter came to rest on its left side.
The helicopter sustained substantial damage to the windshield, fuselage, and tailboom.
The student 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.
The Federal Aviation Administration’s Helicopter Flying Handbook, FAA-H-8083-21A, contained 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 [loss of tail rotor effectiveness] in this downwind condition, it is imperative to maintain positive control of the yaw rate and devote full attention to flying the helicopter.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
  • The student helicopter pilot’s inadequate torque pedal application during practice approaches with a tailwind, which resulted in a loss of yaw control and a subsequent hard landing.