What happened
On 10 July 2003, a Schweizer 300C helicopter, registration HB-XQF, was conducting a VFR training flight in the Waadtländer Alps. The crew, consisting of a trainee pilot and a flying instructor, had been performing various mountain outlandings at elevations up to 1600 m/AMSL. The flight then proceeded to the Planachaux area at an elevation of approximately 1925 m/AMSL.
After two successful landings on a small ridge area, a third approach was attempted. During this final approach, the aircraft required increased power to maintain the necessary flight path. This demand caused the engine speed to drop from the normal operating range of 3000–3200 rpm down to 2800 rpm. Unable to maintain control, the instructor took over the controls and attempted to maneuver away from the peak toward sloping terrain. However, the rotor speed could not be recovered. The helicopter struck the ground at a low forward speed with the nose pointing downslope, subsequently catching in a cattle fence. The impact caused the aircraft to roll several times, resulting in the tailboom being severed. The trainee pilot sustained serious injuries, while the instructor suffered minor injuries.
The investigation
The investigation examined the aircraft's performance capabilities and the crew's decision-making. It was noted that while the aircraft was within weight and center of gravity limits, the performance data provided in the pilot's flight manual for hover out of ground effect (HOGE) was overly optimistic. The investigation also reviewed the engine speed fluctuations during the critical phase of the approach and the effectiveness of the instructor's intervention.
Findings
- The primary cause of the accident was the crew losing control of the helicopter because the approach was attempted without adequate power reserves.
- The crew failed to comply with recognized performance limits for the high-altitude environment.
- The flying instructor's intervention to correct the flight path occurred too late to prevent the loss of control.
- The engine speed dropped below the required 3000 rpm threshold during the power-demanding phase of the approach.