What happened
On 11 August 2012, a Zenith CH 701 aircraft, registration ZU-DOK, was conducting private flight operations at Emoyeni Airfield in KwaZulu-Natal. After completing several successful circuits and landings, the pilot prepared for another circuit with a passenger on board. Following a brief delay at the holding point, the aircraft took off from runway 15.
Shortly after rotation, at an altitude of approximately 40 feet, the engine began running roughly before losing power entirely. The pilot attempted an emergency landing back on the active runway. During the forced landing, the aircraft struck the ground hard at the end of the runway, causing the nose gear to collapse. The aircraft then bounced and overshot the runway, coming to rest near the perimeter fence. While the aircraft sustained significant damage, including a separated left wing and damaged propeller, neither the pilot nor the passenger sustained any injuries.
The investigation
SACAA AIID investigators examined the wreckage and the engine's maintenance history. The investigation focused on the engine's fuel system and the circumstances surrounding the power loss. Technical inspections of the engine revealed that the fuel pipelines were routed near the hot section of the engine without adequate insulation. Furthermore, the investigation found that the fuel system lacked a fuel return line, a component specified in the Rotax 912 LSU operator's manual to prevent vapor formation.
Findings
- The engine power loss was caused by fuel vapour lock.
- The fuel lines were positioned near the hot exhaust manifold without proper insulation.
- The absence of a fuel return line prevented the removal of vaporized fuel from the system.
- Heat buildup in the fuel lines, exacerbated by a short 10-minute rest period between flights and ambient temperatures of 24ºC, led to the vaporization of fuel.
- The aircraft stalled at an altitude too low to allow for a successful recovery.