History of Flight
On 10 February 2007, a Bell 206 B helicopter (registration ZS-HDW) operated by Henley Air (Pty) Ltd. was on a private flight with the pilot and four passengers. The flight returned to Rand Aerodrome (FAGM). The pilot received landing clearance but was instructed to remain north of Runway 11/29 and west of Runway 17/35. While hovering in an easterly direction waiting for another aircraft to land on Runway 35, the helicopter began to yaw to the right. Despite applying full left pedal, the yaw continued and developed into a spin. The tail rotor struck the ground, and the helicopter came to rest upright on its skids facing north. The aft portion of the tail boom separated.
Injuries and Damage
The pilot and four passengers sustained no injuries. The helicopter sustained substantial damage to the tail boom and tail rotor. No other property was damaged.
Meteorological Information
At the time of the accident, the surface wind was 360°/10 knots, with a temperature of 25°C and visibility of 10 km or more. A left crosswind condition existed relative to the hovering helicopter.
Weight and Balance
The helicopter's weight and center of gravity were within the certified limits specified in the Pilot Operating Handbook.
Wreckage and Impact
The tail rotor blades struck the ground and the tail boom. Examination revealed that the tail rotor flapping angle measured 13.5°, exceeding the specified 12±1°. Two tail rotor driveshaft fractures were observed, consistent with a tail rotor strike.
Probable Cause
The helicopter experienced a vortex ring state and a hard landing resulted due to a loss of tail rotor effectiveness.