What happened
On 15 July 2006, at approximately 15:05 UTC, a Robinson R-22 BETA 2, registration EI-EHB, was involved in a training incident at Cork Airport. The aircraft, operated for aerial work, was being prepared for a solo cross-country flight. After completing standard pre-flight inspections, including a hover check and a spot turn, the pilot requested departure clearance from Air Traffic Control. While holding position and adjusting the aircraft's orientation to monitor the runway and surrounding traffic, the low rotor RPM warning horn activated alongside its corresponding warning light.
In response to the alarm, the pilot lowered the collective lever, which led to a heavier than normal landing on the grass adjacent to the runway. The pilot was able to shut down the engine and exit the aircraft without injury. The aircraft sustained minor damage, specifically a bent rear cross tube on the skid assembly.
The investigation
The investigation focused on determining the cause of the rotor RPM drop and the subsequent hard landing. Investigators examined the aircraft's mechanical condition following the event. An engineering inspection of EI-EHB revealed no mechanical failures, such as magneto issues or stuck valves, that could explain a loss of power. The investigation also reviewed the pilot's experience level and the procedures outlined in the manufacturer's operating handbook.
Findings
- The primary cause of the incident was likely pilot inexperience, as there was no identifiable mechanical fault to account for the drop in rotor RPM.
- It is possible the pilot inadvertently moved the throttle, causing the RPM to decrease.
- The investigation noted that the pilot's actions did not align with established recovery procedures, which mandate that a pilot must simultaneously increase throttle and lower the collective to recover RPM regardless of the cause of the warning.