What happened
On 12 March 2010, a Bell 206B helicopter, registration ZS-HFG, was conducting a private scenic flight near Glenside Private Aerodrome in the Winterton district of KwaZulu-Natal. The flight, which included the pilot and three passengers, was orbiting a farmstead to allow a passenger to capture aerial photographs.
While flying at approximately 150 feet above ground level and a speed of 30 knots, the aircraft experienced a sudden, uncommanded 90-degree yaw to the right. In an attempt to regain control, the pilot increased the collective pitch. However, this action instead intensified the yaw, leading to a series of uncontrollable rotations. During the sequence, the helicopter struck a tree, causing the tail boom to break, and subsequently impacted the ground in an open field. While the aircraft was destroyed, the accident was considered survivable; the pilot and two passengers escaped without injury, though one passenger sustained a minor injury consisting of a laceration to the forehead and eye.
The investigation
SACAA AIID investigators examined the wreckage and the pilot's training records. The investigation confirmed that the aircraft was well-maintained, with all mandatory inspections up to date, and was operating within its certified weight and balance limits. No mechanical or structural failures were identified as the cause of the initial yaw.
Meteorological data indicated that while weather conditions were generally fine, the wind direction relative to the aircraft's heading created a high-risk environment for aerodynamic instability. The investigation specifically looked into the phenomenon of Loss of Tail Rotor Effectiveness (LTE) and how the pilot's inputs influenced the aircraft's behavior during the emergency.
Findings
- The primary cause of the accident was the pilot's use of an incorrect recovery technique following the initial yaw, which served to aggravate the loss of tail rotor effectiveness.
- The aircraft was positioned in a flight regime—low airspeed, low altitude, and high power—where the relative wind caused main rotor disc vortex interference, making the helicopter susceptible to LTE.
- The pilot possessed limited experience on this specific helicopter type, with only 62.4 hours on type.
- There was a lack of specific training regarding LTE phenomena and proper recovery procedures in the pilot's training history.
Safety action
- It is recommended that the SACAA Testing Standards Department instruct Approved Training Organizations (ATOs) to ensure that all helicopter pilot training programs include dedicated, sufficient instruction on LTE and the necessary recovery actions.