What happened
On 24 December 2006, a Bell 206B helicopter, registration ZS-HUC, was involved in an incident near an agricultural smallholding in Cullinan, Gauteng. The pilot, who owned the aircraft, was conducting a series of recreational flights to provide children from a local orphanage with an aerial experience.
The takeoff was performed from a cleared area on a smallholding, heading north into a northwest wind. The takeoff area was bounded by a paddock fence to the left and several large trees to the right. During the final flight of the day, which included three young passengers, the aircraft entered forward flight. As the helicopter transitioned into flight, a powerful gust of wind from the west pushed the aircraft toward the right. The pilot was unable to compensate for this sudden lateral movement, causing the main rotor blades to strike a Blue gum tree. The pilot managed to execute a forced landing in an open field ahead of the impact site. There were no injuries to the four occupants.
The investigation
Investigators examined the aircraft's maintenance history and the environmental conditions at the time of the event. The aircraft had undergone a Mandatory Periodic Inspection (MPI) less than 20 flight hours prior to the incident, and the maintenance was performed by a certified organization.
Regarding the meteorological conditions, while the pilot noted that wind gusts had increased alongside rising temperatures, the investigation looked into the specific wind limitations for the aircraft. Consultations with Bell Helicopters' Flight Safety division revealed that the Pilot’s Operating Handbook (POH) does not specify formal crosswind or wind limitations for this model, though tools such as hover ceiling charts and wind azimuth diagrams are available to assist pilots in assessing controllability.
Findings
- The primary cause of the rotor strike was the pilot's failure to apply sufficient left cyclic input at a rapid enough rate to counteract the sudden western gust.
- The pilot had been operating in known gusty conditions but likely did not anticipate a gust of such significant magnitude.
- The aircraft sustained damage to the main rotor blades that exceeded economical repair, and the event necessitated a sudden stoppage inspection of all dynamic components.