What happened
On 22 April 2008, a Robinson R44 Raven II helicopter, registration ZS-MZS, departed from a farm in Hoedspruit, Limpopo, bound for Nelspruit. Shortly after takeoff, the pilot noticed an increase in cylinder head temperature and a low rotor RPM alarm. The pilot performed a precautionary landing on the R531 public road. After conducting inspections and finding no immediate issues, the pilot attempted to continue the flight.
During the subsequent takeoff, as the aircraft transitioned into flight and gained speed, the low rotor RPM alarm sounded again. The helicopter lost altitude and the main rotor struck wooden pallets stacked on a stationary truck parked near the takeoff site. The aircraft then crashed into the ground, resulting in damage to the fuselage, skids, and rotor components. One passenger sustained minor injuries.
The investigation
SACAA AIID investigators examined the aircraft's fuel system and discovered that the fuel in the tanks was a different color than the required Avgas 100LL. Laboratory analysis by the SABS confirmed that the helicopter had been refueled with Grade GP5 Aviation Turbine fuel instead of the authorized Avgas 100LL.
The investigation found that the pilot had refueled using a 200-liter sealed drum purchased from a local distributor. While the drum was labeled as Avgas 100LL, the contents were actually turbine fuel. The investigation also noted that the pilot had purchased three such drums, which had expired three weeks prior to the accident.
Findings
- The primary cause of the power loss and subsequent forced landings was the use of an incorrect grade and type of fuel.
- The fuel supplier provided a drum that was incorrectly labeled, containing turbine fuel instead of Avgas.
- The pilot failed to verify the fuel grade via color or other appropriate methods during the refueling process.
- The aircraft was within its maximum certified takeoff weight at the time of the accident.