What happened
On 20 July 2011, a Robinson R44 Raven II, registration ZS-JRS, was conducting a private flight in the Limpopo Province. After completing a task involving animal darting near the Vivo area, the pilot flew to Thabazimbi Aerodrome (FATI) to meet a client. Prior to departing FATI, the helicopter was refuelled with 150 litres of fuel taken from a previously used, unsealed drum.
Approximately 50 minutes into the flight en route to Pietersburg Aerodrome (FAPI), the engine began running roughly before failing completely. At an altitude of roughly 500 feet, the pilot initiated an autorotation. The aircraft descended into bushy, uneven terrain, striking a tree stump and subsequently hitting an embankment. The impact caused the helicopter to nose over and come to rest on its side. The pilot sustained minor injuries, including broken ribs and lacerations, but managed to exit the wreckage unassisted.
The investigation
SACAA AIID investigators examined the wreckage and the fuel handling procedures used prior to the accident. The investigation focused on the sequence of events following the engine failure and the condition of the fuel used during the final leg of the flight. Investigators noted that the fuel for the flight had been uplifted from a drum that was part of a pool of containers redistributed via vehicle. While the pilot had performed a visual inspection of the fuel and found it clean, the investigation looked into the potential for hidden contaminants within the unsealed drum.
Findings
- The engine failure was caused by the seizure of the No. 3 big end bearing.
- The primary cause of the engine failure was contaminated fuel likely introduced during the refuelling process from an unsealed drum.
- The aircraft's impact sequence involved striking a tree and an embankment, which led to the separation of the tail rotor assembly from the tail boom.
- The terrain at the crash site was heavily eroded, contributing to the difficult forced landing conditions.