Winnsboro, SC, USA
N502SL
MCDONNELL DOUGLAS HELICOPTER 369E
During an instructional flight while in a three-foot hover, the certified flight instructor (CFI) applied right anti-torque pedal input with the intention of simulating loss of tail rotor thrust while in a hover. The student correctly reduced throttle and both occupants agree that the helicopter contacted the ground. While neither occupant agrees as to who applied throttle control, throttle control input was applied and the helicopter became airborne with slow main rotor rpm. The CFI took the controls and attempted to cushion the landing, but the helicopter landed hard. There were no reported preimpact failures or malfunctions. After the accident the engine was placed in a test cell and operated to full power with no evidence of failure or malfunction.
On October 19, 2009, about 1430 eastern daylight time, a McDonnell-Douglas 369E helicopter, N502SL, registered to South Carolina Law Enforcement Division (SLED), was landed hard at the Fairfield County Airport (FDW), Winnsboro, South Carolina. Visual meteorological conditions prevailed at the time and no flight plan was filed for the 14 Code of Federal Regulations (CFR) Part 91 instructional flight. The helicopter was substantially damaged and the certified flight instructor (CFI) and rotorcraft- rated student (student) were not injured. The flight originated from the SLED Heliport (2SC6), Columbia, South Carolina, about 1400. The student stated that after departure the flight proceeded to FDW where he executed two normal approaches. After the second, he hover taxied to a grassy area south of runway 04/22, where he and the CFI noted the wind direction and discussed the next maneuver to be performed which was loss of tail rotor thrust while in a hover. The briefing before the maneuver included the proper recovery procedure which was to slowly reduce throttle control. While in a three foot hover the CFI announced that he was initiating the loss of tail rotor thrust and the helicopter began slowly yawing to the right. The student initiated recovery by reducing throttle and while in a two foot hover the CFI instructed him to regain the entry altitude of three feet. The student increased collective control which reduced rotor rpm and induced another right yaw. He then reduced throttle which caused the rotor rpm to deteriorate further resulting in the helicopter descending. He increased collective control to remain airborne while the helicopter slowly yawed to the right. The CFI instructed him not to let the helicopter contact the ground and he continued to apply up collective while the helicopter continued yawing to the right. As he was applying up collective he felt the CFI grasp the cyclic and collective controls and heard the rotor rpm and engine noise increase. He later stated that while it is not clear to him which of them applied power, he was fairly certain that he did not. The helicopter began a rapid right yaw possible landing briefly then becoming airborne while yawing 360 degrees and climbing to an estimated height of 10 to 20 feet above ground level. The CFI attempted to hover then announced he was rolling the throttle to idle. The helicopter then began a rapid descent, landed hard, and rolled towards the left side. He and the CFI initiated the emergency shutdown procedures and exited the helicopter. The CFI stated that he briefed the student on the emergency procedure to be performed (loss of tail rotor thrust) and also the proper response which would be to slowly reduce throttle and cushion the landing with collective control. The CFI initiated the maneuver by applying right anti-torque pedal input and the student responded by decreasing throttle. As the rotation stopped the helicopter settled and made contact with the ground with some movement. The student was uncomfortable with the touchdown and applied throttle control. Though his (CFI’s) hands were on the flight controls he was not guarding the throttle closely enough to arrest the quick application of throttle. The helicopter became airborne and began yawing very quickly to the right which was not corrected by left anti-torque pedal input. He closed the throttle which stopped the right yaw but at that point the helicopter was 7 to 10 feet and rotor rpm was insufficient to maintain flight. He applied collective and forward cyclic to cushion the landing but the helicopter landed hard causing the left skid gear to collapse. The National Transportation Safety Board (NTSB) Pilot/Operator Aircraft Accident/Incident Report submitted by the operator indicated there was no mechanical failure or malfunction. Following the accident the engine was removed from the helicopter, sent to the manufacturer’s facility to be functionally tested. With Federal Aviation Administration oversight the engine was ran and found to operate normally. The emergency procedures for loss of tail rotor thrust while in a hover, specified in the flight manual, indicate to place the twistgrip in the ground idle position and to perform a hovering autorotation.
The flight instructor's failure to monitor the simulated emergency procedure, resulting in a hard landing. Contributing to the accident was the intentional throttle application by one of the flightcrew.
Source: NTSB Aviation Accident Database
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