NTSB Identification: IAD05LA122.
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Accident occurred Friday, August 12, 2005 in Saulsville, WV
Probable Cause Approval Date: 07/31/2006
Aircraft: Enstrom 280C, registration: N5691B
Injuries: 1 Serious,1 Uninjured.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
While on approach to the landing area, the pilot could not see a windsock, and based his estimation of the wind by watching leaves on the trees. As he approached the landing area at a "normal to steep angle," and while stabilized at approximately 40 knots indicated airspeed, about 100 feet above the ground, the helicopter began a slow, un-commanded yaw to the right. The pilot responded by applying left anti-torque pedal; however, the helicopter continued to yaw to the right. The pilot observed that the engine and rotor rpm were "out of the green," but felt that he could not enter an autorotation due to a power line that was below. He instead increased the throttle, and the helicopter continued to yaw to the right. About 10 feet above the ground, and after about 270 degrees of yaw, the helicopter descended rapidly and impacted the ground, seriously injuring the passenger. Examination of the helicopter following the accident revealed that the tail rotor had sustained impact damage to both blades, and that the tail rotor drive shaft was fractured at the coupling hub. Examination of the fractured portions of the coupling hub revealed signatures consistent with a torsional event, such as a tail rotor strike, and no evidence that the fracture surfaces were rubbing against each other under power. According to Federal Aviation Administration Advisory Circular 90-95, loss of tail rotor effectiveness (LTE) events typically occur in a low airspeed flight regime while maneuvering, such as on final approach to landing. Any maneuver that requires the pilot to operate at high-power, at low airspeed, and with a left crosswind or tailwind, creates an environment where unanticipated right yaw may occur. Additional factors that can influence the severity of the onset of LTE include increases in gross weight and density altitude, low indicated airspeeds, and power droop. Recovery from an LTE event should include the application of full left pedal, while simultaneously moving the cyclic forward to increase speed, and altitude permitting, a reduction in power.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The pilot's inadequate remedial action following a loss of control during the landing approach. Full narrative available
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