What happened
During a training flight at Okotoks Air Park in Alberta, an instructor and a student were performing practice autorotations in a Hughes 269C helicopter. The flight was intended to prepare the student for an upcoming commercial rotary wing flight test. After successfully completing several maneuvers, the student attempted a 180-degree turning autorotation but approached the intended landing area significantly short of the target.
As the student initiated a flare, the helicopter's tail rotor blades struck a paved access road. This impact caused the tail rotor drive shaft to twist and uncouple from the transmission, leading to a rapid loss of directional control. The helicopter climbed to approximately 50 feet above ground level, began rotating in the opposite direction of the main rotor, and then pitched nose down into a crash. Both the instructor and the student sustained minor injuries and were sprayed with fuel from a punctured tank, but they were able to exit the aircraft independently. The helicopter sustained substantial damage.
The investigation
The investigation focused on the actions of both crew members during the final descent. Investigators examined the flight history, noting that the student had previously completed five successful autorotations during the same flight. The investigation also reviewed the mechanical state of the Hughes 269C, finding it was properly maintained, certified, and within weight and center of gravity limits. The weather conditions at the time of the accident were light and variable with no contributing meteorological factors.
Findings
- The student pilot misjudged the altitude and distance from the intended landing area during the practice autorotation.
- The student initiated a steep flare and failed to level the helicopter before touchdown.
- The instructor failed to take timely corrective action to prevent the tail rotor strike.
- The instructor's decision to allow the maneuver to continue may have been influenced by the student's recent successful maneuvers, suggesting potential factors of complacency or reduced vigilance.
- The impact with the ground caused the destruction of the tail rotor blades and the subsequent loss of control.