What happened
On March 29, 2021, a Hughes 269C helicopter was conducting training maneuvers at the Dinslaken/Schwarze Heide airfield. The flight was being conducted by a flight instructor and a pilot preparing for a proficiency check. The crew had completed several training circuits involving autorotations and steep climbs.
During the flight, the instructor took control to demonstrate a simulated engine failure during the initial climb phase. The helicopter was climbing at approximately 50 KIAS at an altitude of about 300 ft A/GL. To simulate the failure, the instructor lowered the collective and reduced the throttle, resulting in a stable autorotative descent with the main rotor RPM within the normal range. The instructor intended to perform a power recovery by initiating a flare and applying engine power.
However, as the flare was initiated, the helicopter experienced an unexpected increase in sink rate. The aircraft struck the grass runway with low forward speed and subsequently flipped over. The impact caused heavy damage to the Hughes 269C. Both occupants sustained two minor injuries and were able to exit the wreckage independently.
The investigation
The BFU examined the wreckage and the flight sequence. On-site inspections of the controls, engine, transmission, clutch, and freewheel components revealed no evidence of technical malfunctions that could have caused the accident. The aircraft was equipped with dual controls at the time of the event. The investigation also noted that a small fire started near the engine blower and oil cooler area but was quickly extinguished by bystanders.
Findings
- The aircraft was operating within the "Dead Man's Curve" (Height-Velocity Diagram) area, where an autorotative landing is extremely difficult without risking damage or injury.
- The high sink rate during the autorotation, caused by insufficient forward airspeed, could not be adequately compensated for by the flare.
- The helicopter struck the ground hard despite the application of engine power during the recovery attempt.