What happened
On July 12, 2010, a Robinson R22 Beta II helicopter, registration OK-BIG, was conducting flight training at Kyjov Airport. The flight involved an instructor and a student pilot performing advanced autorotation exercises. Following a series of successful maneuvers, the instructor decided to demonstrate the change in the aircraft's reactive torque by simulating an engine power reduction while hovering at an altitude of approximately 3 to 4 meters.
During this maneuver, the student pilot correctly compensated for the torque change, but the helicopter began to descend rapidly. Although the instructor attempted to restore power by adjusting the collective, the engine RPM failed to increase sufficiently to arrest the descent. The aircraft struck the ground with significant force, causing the left skid to break. The impact caused the main rotor blades to strike the ground, destroying them and resulting in the helicopter capsizing onto its left side. Both occupants escaped the aircraft without injury.
The investigation
The ÚZPLN investigation examined the flight sequence, the mechanical condition of the aircraft, and the qualifications of the crew. Investigators confirmed that the student pilot and instructor were both fully qualified and met all medical and regulatory requirements for the flight. The aircraft was found to be airworthy, with all maintenance inspections up to date.
Technical examination of the governor (part B286-2) revealed that the component was functioning correctly, responding appropriately to both increases and decreases in power. No mechanical failures in the control systems were identified. The investigation also noted that the high ambient temperature on the day of the accident likely contributed to the difficulty in maintaining engine performance during the power reduction.
Findings
- The instructor chose to perform an unstandardized maneuver involving a power reduction at an altitude of only 3–4 meters, a procedure not required by the training syllabus or described in the flight manual.
- The altitude chosen for the demonstration was inappropriate, leaving insufficient margin for error when the engine failed to regain RPM quickly enough.
- The instructor's attempt to restore power following the reduction was unsuccessful because the engine lacked the necessary time to accelerate and the torque required to maintain rotor RPM at a high angle of attack.
- High ambient temperatures likely negatively impacted the engine's ability to respond to the power demand.