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Aviation Accident

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NTSB Identification: GAA19CA063
14 CFR Part 91: General Aviation
Accident occurred Sunday, November 18, 2018 in Knox City, TX
Probable Cause Approval Date: 09/26/2019
Aircraft: Robinson R44, registration: N4167Y
Injuries: 4 Uninjured.

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 helicopter pilot reported that, while conducting a photography flight about 70 ft above ground level, the helicopter's heading was 190┬░, and the airspeed was less than 9 knots. With a 10-knot tailwind, the helicopter began to settle with power. The pilot increased the collective and applied forward cyclic to increase the airspeed, but the helicopter continued to settle and impacted the ground hard.
The helicopter sustained substantial damage to the main rotor system and fuselage.
The pilot reported that there were no mechanical malfunctions or failures with the helicopter that would have precluded normal operation.
The pilot reported that the wind about the time of the accident was from the north at 10 knots.
According to the Helicopter Flying Handbook, Chapter 11, page 11-10
When recovering from a settling with power condition, the pilot tends first to try to stop the descent by increasing collective pitch. However, this only results in increasing the stalled area of the rotor, thereby increasing the rate of descent. Since inboard portions of the blades are stalled, cyclic control may be limited. Recovery is accomplished by increasing airspeed, and/or partially lowering collective pitch. In many helicopters, lateral cyclic combined with lateral tailrotor thrust will produce the quickest exit from the hazard assuming that there are no barriers in that direction. In a fully developed vortex ring state, the only recovery may be to enter autorotation to break the vortex ring state.

The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
  • The pilot's failure to maintain adequate airspeed with a tailwind, which resulted in the helicopter settling with power, and his subsequent incorrect collective application while attempting to recover, which resulted in a loss of helicopter control due to a loss of tail rotor effectiveness.