NTSB Identification: ERA10TA501
14 CFR Public Use
Accident occurred Friday, September 24, 2010 in Covington, GA
Probable Cause Approval Date: 07/21/2011
Aircraft: EUROCOPTER AS-350, registration: N91DK
Injuries: 2 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this public aircraft accident report.
According to the pilot of the helicopter, the instructor simulated a hydraulics failure by “turning off” the flight control hydraulics switch, in order to perform a hydraulics-off, run-on landing as the remedial action to the simulated emergency. As the helicopter slowed over the runway, the nose yawed to the left, and the pilot was unable to correct the yaw with right pedal input. The instructor took control of the helicopter, and completed a low-level, left-hand orbit to demonstrate and complete the maneuver. As the helicopter completed the left orbit and lined up for landing, it “rolled wings level” but then continued to roll to the right and collided with terrain. The pilot said that the entire maneuver was conducted hydraulics-off, and that he felt the instructor had control of the helicopter until it rolled past wings-level to the right. The pilot added that the instructor had successfully completed a similar maneuver earlier in the day, without restoring the flight control hydraulics. According to the manufacturer's Flight Manual (Emergency Procedures) and the Flight Manual Supplement, Hydraulic Pressure Failure Training Procedures, "CAUTION: DO NOT ATTEMPT TO CARRY OUT HOVER FLIGHT OR ANY LOW SPEED MANEUVER WITHOUT HYDRAULIC PRESSSURE ASSISTANCE. THE INTENSITY AND DIRECTION OF THE CONTROL FEEDBACK FORCES WILL CHANGE RAPIDLY. THIS WILL RESULT IN EXCESSIVE PILOT WORKLOAD, POOR AIRCRAFT CONTROL, AND POSSIBLE LOSS OF CONTROL." Both the pilot and the instructor stated that there was nothing wrong with the performance and handling of the helicopter.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The flight instructor's loss of control of the helicopter during the intentional demonstration of a low speed, hydraulics-off maneuver, that was warned against in the helicopter manufacturer's flight manual. Full narrative available
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