What happened
On 3 April 2015, a Robinson R44 Raven II helicopter, registration ZS-HFO, was conducting a private flight near Durban, South Africa. The pilot intended to land at the Verulam Recreational Grounds for a static display; however, a large vehicle obstructing the landing area forced the pilot to orbit the field at approximately 400 feet above ground level. During this period, the engine suddenly failed.
Seeking a safe landing spot within a built-up area, the pilot identified an open polo field but had to execute a 180-degree turn. While attempting to clear surrounding tall trees, the pilot stretched the autorotation, which caused the main rotor RPM to decay rapidly. The aircraft impacted the ground with significant force in an upright position before rolling onto its right-hand skid. The passenger sustained a serious injury to their back, while the pilot suffered a minor laceration to the elbow.
The investigation
SACAA AIID investigators examined the engine and the aircraft's maintenance history. They discovered that the engine had recently undergone an overhaul following a previous incident where it was accidentally started without oil. To expedite the return to service, the engine was installed in the airframe without undergoing a standard post-maintenance bench test.
Upon inspection of the wreckage, investigators found that the fuel supply pipe, which runs from the fuel control unit to the fuel flow divider, was not properly secured. Because this component is located beneath the main transmission deck, it is difficult to inspect visually after engine installation. The investigation determined that engine vibrations caused the unsecured fitting to gradually unscrew, leading to fuel starvation.
Findings
- The engine stoppage was caused by fuel starvation resulting from a loose fuel pipe fitting.
- The fitting was not properly fastened during maintenance and began to loosen due to operational vibrations.
- The engine was not subjected to a bench test procedure following its overhaul.
- The pilot's decision to fly over a built-up area at a low altitude limited the available options for a safe autorotative landing.
- Maintenance practices were improper, specifically regarding the failure to verify the security of fittings after engine installation.