What happened
On October 27, 2002, a private flight was underway from Kyalami toward Krugersdorp Aerodrome when the pilot of an Elisport CH-7 Angel, registration ZU-ASU, noticed a significant drop in engine performance. While flying near the MTN Dome, the pilot descended to roughly 500 feet above ground level and attempted a right-hand turn to locate a suitable landing area. During this maneuver, the engine suffered a complete failure.
As the pilot attempted an auto-rotative landing from approximately 300 feet, the aircraft encountered overhead power lines directly in its flight path. The main rotor blades struck the lines, causing the pilot to lose control of the aircraft. The helicopter subsequently struck the ground in an open field near Honeydew, approximately 40 meters past the power lines. The impact ruptured the fuel lines, causing the wreckage to ignite. The pilot sustained one serious injury to his back but successfully escaped the burning wreckage before help arrived.
The investigation
Investigators examined the wreckage and the circumstances surrounding the power loss. An eyewitness reported seeing the helicopter at an altitude of approximately 200 meters, noting a rapid decrease in engine RPM and a loss of altitude prior to the collision with the lines. The investigation focused on the mechanical state of the two-cylinder engine following the impact and the sequence of events leading to the loss of control.
Findings
- The primary cause of the accident was an engine failure caused by a cold seizure.
- One of the two piston assemblies in the engine had seized while in a cold state, which initially caused power deterioration and eventually led to total engine failure.
- The pilot was unable to maneuver the aircraft to avoid the power lines due to the sudden loss of power and the necessity of the descent.