What happened
On 12 March 2017, a Jabiru UL, registration ZU-FIC, departed Margate Aerodrome on a private flight destined for Cato Ridge Airfield. Approximately twelve minutes into the flight, the pilot noticed a loss of airspeed. In an attempt to troubleshoot a potential fuel issue, the pilot activated the fuel pump, but the aircraft's performance did not improve. Upon reducing power to idle, the pilot discovered that the propeller had detached from the engine.
While flying at roughly 1,800 feet above ground level, the pilot managed to establish a steady glide and targeted a road cutting through a sugar cane field in Sizela for an emergency landing. During the touchdown, the right main landing gear became trapped in a furrow and broke away. This caused the aircraft to veer right and strike an embankment, leading to the collapse of the nose gear. Both the pilot and the passenger sustained minor injuries.
The investigation
SACAA AIID investigators examined the engine and the propeller attachment mechanism to determine why the propeller had separated. The investigation established that the engine had 383.8 hours of total time and was within its manufacturer-specified overhaul limits.
Crucially, the investigators found that no dowel pins were installed in the assembly. Without these pins, the propeller flange bolts were forced to absorb the entire shear force. This resulted in the failure of the flange bolts, causing the propeller to shear off during flight.
Findings
- The primary cause of the propeller separation was the failure of the propeller attachment bolts due to the absence of dowel pins.
- The aircraft's landing was unsuccessful in preventing structural damage because the right main wheel struck a furrow in the field.
- While the engine was not yet due for a mandatory overhaul, the manufacturer's manual recommended updating the engine configuration to include 8mm dowels during full overhauls or bulk strips.
Safety action
Following the incident, the aircraft owner, Shadow Lite CC, planned to issue a service letter recommending that all owners implement the dowel upgrade immediately. Additionally, there was a recommendation for the Director of Civil Aviation to review the manufacturer's service bulletin and consider issuing an Airworthiness Directive to mandate the installation of these dowels.