What happened
On 19 March 2018, a Robinson R22 Beta helicopter, registration ZS-HAI, was conducting a private flight at New Tempe Aerodrome. After completing pre-flight inspections and engine start-up, the pilot established the aircraft in a low hover, approximately five feet above the ground, to perform necessary checks.
While the aircraft was hovering in ground effect on Runway 2LL, the pilot heard a loud bang originating from the rear of the helicopter. The impact caused the aircraft to yaw to the left and begin a descent. The pilot reacted by lowering the collective pitch, allowing the aircraft to land safely on the runway. Upon inspection, the pilot discovered debris on the runway and confirmed that the fan-wheel assembly had suffered a failure. There were no injuries to the pilot, though the aircraft sustained substantial damage.
The investigation
SACAA AIID investigators examined the aircraft and the failed component. The investigation included a metallurgical examination of the fan-wheel assembly, which was conducted by the National Transportation Safety Board (NTSB) Materials Division in the United States.
Records indicated that the aircraft had a total of 1,059.2 flight hours. The most recent mandatory periodic inspection (MPI) had been completed at 988.6 airframe hours, approximately 70 hours prior to the incident. The investigation confirmed that the pilot was properly licensed and medically certified for the operation.
Findings
Technical analysis revealed that the failure of the fan-wheel assembly was caused by a fatigue crack on one of the blades. This crack had propagated near the weld at the leading edge of the blade, eventually leading to the structural failure of the assembly while the helicopter was in a low hover.