What happened
The pilot was repositioning the aircraft immediately following the completion of a Phase IV inspection. Upon initiating the maneuver, the helicopter lifted off from the surface pad. Shortly after becoming airborne, the aircraft began making several clockwise revolutions. The pilot lost control of the situation, and the helicopter descended rapidly out of control. It impacted the ground with significant force and rolled over onto its right side.
The investigation
A thorough examination of the accident site and the aircraft was conducted to determine the mechanical status of the helicopter at the time of the incident. Investigators focused on the integrity of the flight control systems, particularly those related to the tail rotor assembly, given the nature of the uncontrolled rotation observed during the flight.
Findings
The investigation revealed a critical maintenance error that directly contributed to the loss of control. The number 1 tail rotor driveshaft had not been reconnected after the previous Phase IV inspection. This disconnection prevented the proper transmission of power to the tail rotor, rendering the aircraft unable to counteract torque and maintain directional control during the low-speed maneuver.
Safety message
This accident highlights the critical importance of thorough post-maintenance checks. It is essential that all components, particularly drive shafts and linkages, are verified as fully reconnected and secured before any flight operations resume after inspection or maintenance work.