What happened
On 10 February 2022, a private flight departing from Robertson Aerodrome (FARS) encountered a critical mechanical failure while traversing the Cape Peninsula. The aircraft, a Jabiru 430 with registration ZU-IKI, was en route to Morning Star Aerodrome under visual flight rules. While cruising at approximately 1500 feet above ground level, the pilot experienced a loud bang followed by an immediate loss of engine power.
The sudden engine stoppage was caused by the propeller detaching from the engine flange, which subsequently caused the engine to over-rev. The pilot issued a MAYDAY call and attempted an emergency landing on a road within the Cape Point Nature Reserve. During the landing sequence, the aircraft's left wing struck roadside vegetation, causing the plane to ground-loop and come to rest in the fynbos. The pilot and passenger sustained serious injuries and were transported to a hospital by ambulance.
The investigation
An investigation by the SACAA AIID examined the wreckage and the aircraft's maintenance history. While the engine was found to be functioning normally upon inspection, the propeller itself was not recovered for analysis. Investigators noted that the aircraft had undergone periodic inspections at various intervals, including a recent check at 94.3 hours, which included torque setting verifications. Based on the timing of the last inspection, it is estimated that any loss of bolt tension likely occurred within the 9 hours of flight preceding the accident.
During the post-accident examination of the engine compartment, investigators discovered a cordless electric screwdriver and a socket left inside the engine bay.
Findings
- The primary cause of the accident was the propeller detached from the engine in-flight due to a likely loss of tension in the mounting bolts.
- The detachment caused the engine to rev excessively, making a controlled flight impossible.
- The pilot's pre-flight inspection was insufficient, as evidenced by the presence of tools left in the engine bay.
- Weather conditions were favorable and did not contribute to the event.
Safety action
- Maintenance providers and operators are encouraged to strictly adhere to manufacturer manuals by verifying the torque of propeller bolts during 100-hour service inspections.