What happened
On October 16, 2001, a Bell 206L helicopter, registration ZS-HIB, was conducting a test flight at Rand Airport following maintenance work on its fuel control unit and gearbox. The flight, which included the pilot and two ground engineers, proceeded normally for approximately 45 minutes. As the pilot attempted to turn toward the helipad near the control tower for landing, the aircraft suffered an unexpected loss of engine power.
In response to the power loss, the pilot initiated an autorotation and steered the aircraft toward a grassy area adjacent to Runway 17. During the touchdown, the right-hand main skid struck a rainwater furrow in the ground. This impact caused the helicopter to bounce, leading the main rotor blades to strike the tail boom.
The investigation
Investigators examined the wreckage and the maintenance history of the aircraft. The helicopter had recently undergone a mandatory periodic inspection in August 2001. The investigation focused on the mechanical state of the fuel system following the recent repairs to the fuel control unit and gearbox. Physical examination of the aircraft components at the accident site revealed a specific mechanical failure in the pneumatic assembly.
Findings
- The primary cause of the engine failure was that a nut assembly on the fuel control to governor tee pneumatic tube ‘B’ had vibrated loose.
- This loose connection resulted in insufficient fuel flow, leading to the engine shutdown.
- The loss of power occurred during the landing phase of a test flight.
- The structural damage to the Bell 206L, including the tail boom, main rotor blades, tail rotor, and stabilizers, was a direct result of the impact with the ground and the subsequent rotor-to-boom strike.
- There were no injuries to the three occupants on board.