What happened
On 01 June 2007, a private flight departing from Klerksdorp Aerodrome (FAKD) for Rustenburg experienced a critical mechanical failure shortly after takeoff. While climbing at approximately 300ft, the pilot of the Jabiru SP, registration ZU-CIP, noticed a vibration originating from the front of the aircraft.
In an attempt to return to the runway, the pilot initiated a turn, which caused the vibration to intensify. During this maneuver, the propeller detached from the engine. To prevent the engine from over-revving, the pilot reduced throttle and managed a descent. The aircraft subsequently made a hard landing on the grass adjacent to the runway, causing the undercarriage to collapse and the fuselage to sustain damage. Both the pilot and the passenger escaped the incident without injury.
The investigation
SACAA AIID investigators examined the wreckage and the maintenance history of the aircraft. The investigation focused on the circumstances leading to the propeller's departure from the engine. While the propeller itself was not recovered, making physical testing of the bolts impossible, investigators reviewed manufacturer correspondence and maintenance logs.
It was noted that the pilot, a qualified mechanic, performed much of the aircraft's minor maintenance. However, the investigation found that the aircraft's maintenance intervals were dictated by annual inspections rather than the specific hourly intervals required for propeller bolt tension checks. Furthermore, the checklist used by the approved person during the most recent annual inspection did not include a detailed inspection of the propeller mounting.
Findings
- The propeller separation was caused by the loosening of the fastening bolts.
- Environmental factors, specifically changes in humidity and temperature, likely caused the wooden propeller's thickness to vary, leading to the loss of bolt tension.
- The pilot was unaware of a manufacturer service bulletin (JSB 009-1) which mandated specific inspections of the propeller bolts after the initial 25 hours of engine use and every 50 hours thereafter.
- The aircraft's low annual flight hours meant that the required inspection intervals were not reached between scheduled annual inspections.
- The landing gear failed upon impact due to the high rate of descent during the hard landing.