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Aviation Accident

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NTSB Identification: CEN15FA003
Nonscheduled 14 CFR Part 135: Air Taxi & Commuter
Accident occurred Saturday, October 04, 2014 in Wichita Falls, TX
Probable Cause Approval Date: 07/23/2015
Aircraft: BELL HELICOPTER TEXTRON 206L 1, registration: N335AE
Injuries: 3 Fatal, 1 Serious.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The pilot reported that he was making an approach to a hospital helipad into light wind at night when he chose to go around because he felt that the approach was too high and fast. The pilot lowered the helicopter’s nose, added power, and raised the collective, and the helicopter then entered a rapid, “violent” right spin. A review of the last 43 seconds of the helicopter’s flight track data revealed that, as the helicopter approached the helipad, it descended from 202 to 152 ft and decelerated from a ground speed of about 9 to 5 knots before it turned right. The pilot attempted to recover from the uncommanded spin by applying left antitorque pedal and cyclic, but he was unable to recover, and the helicopter then spun several times before impacting power lines/terrain. Postaccident examination of the helicopter and the engine revealed no mechanical anomalies that would have caused the helicopter’s uncommanded right spin. The helicopter was under its maximum allowable gross weight at the time of the accident, and the wind was less than 4 knots. 
Federal Aviation Administration guidance states that the loss of tail rotor effectiveness could result in an uncommanded rapid yaw, which, if not corrected, could result in the loss of aircraft control. The guidance further indicates that, at airspeeds below translational lift, the tail rotor is required to produce nearly 100 percent of the directional control and that, if the required amount of tail rotor thrust is not available, the aircraft will yaw right. Therefore, it is likely that that the pilot did not adequately account for the helicopter’s low airspeed when he applied power to go around, which resulted in a sudden, uncommanded right yaw due to a loss of tail rotor effectiveness.
 
 


The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
  • The pilot’s failure to maintain yaw control when he applied power to execute a go-around at a low airspeed in dark, night conditions, which resulted in a rapid, uncommanded right yaw due to a loss of tail rotor effectiveness.