What happened
On 17 September 2001, a student pilot was conducting a second solo training flight in an Enstrom F28C, registration ZS-RCF, at Wonderboom Aerodrome. The flight was intended to be a circuit between the aerodrome and the nearby helicopter training area.
As the pilot transitioned from the approach phase into a hover, a series of improper control inputs occurred. The pilot advanced the throttle without simultaneously adjusting the collective pitch lever, leading to an increase in engine RPM. In an attempt to correct this, the pilot reduced engine power and lowered the collective pitch. During this sequence, the pilot appeared to lose control of the aircraft and became unresponsive to the controls. Consequently, the helicopter underwent a leftward yaw of approximately 360 degrees and struck the ground at a high vertical descent rate near Runway 06.
The investigation
SACAA AIID investigators examined the aircraft and the circumstances surrounding the flight. The investigation confirmed that the pilot was a student with 45 total flying hours on the type and held a valid license. The weather conditions at the time were clear with good visibility (CAVOK) and light winds from the northeast.
Technical inspections were performed on the aircraft's components, specifically focusing on the overrun clutch. The inspection revealed that the clutch was in serviceable condition, ruling out mechanical failure of that specific component as a factor in the accident.
Findings
- The primary cause of the accident was the application of incorrect flight techniques during the transition to a hover, specifically advancing the throttle without adjusting the collective pitch.
- The pilot's subsequent reaction to the rising RPM—lowering the collective pitch—further destabilized the aircraft.
- The pilot experienced a period of being "frozen" on the controls at approximately 60 feet above the ground, which prevented necessary corrective actions.
- The resulting loss of directional control and high descent rate led to the hard landing and substantial damage to the Enstrom F28C.