What happened
On 20 April 2000, a Bell 206B helicopter, registration ZS-RHP, was engaged in private flight training near Phokeng, close to Rustenburg. The pilot was performing a series of quick stop maneuvers. During the eighth and final attempt at this maneuver, the aircraft's lower tail fin and stinger assembly made contact with the ground.
This impact caused the tailboom assembly to bend upward. As the boom moved, the main rotor blades struck the structure, effectively severing the tailboom from the rest of the aircraft. Following the separation, the helicopter rotated 180 degrees. The momentum caused the aircraft to slide backward on its skids, which ultimately resulted in the skids breaking off from the airframe. There were no injuries or fatalities reported in the incident.
The investigation
SACAA AIID investigators examined the sequence of the maneuver and the structural failure of the airframe. The investigation focused on the altitude at which the quick stop maneuvers were being executed and the resulting attitude of the aircraft relative to the terrain. The physical evidence at the site confirmed that the tail rotor assembly struck the ground before the main rotor blades intersected the tailboom.
Findings
- The primary cause of the accident was that the pilot performed the maneuver at an insufficient altitude above the ground.
- The high nose-up attitude required for the quick stop maneuver left inadequate clearance for the tail rotor assembly.
- The impact with the ground initiated a chain of structural failures, including the upward bending of the boom and the subsequent severing of the tailboom by the main rotor blades.