What happened
On the morning of 8 November 2006, a Sycamore MK I gyroplane, registration ZU-CCY, departed from Rhino Park Aerodrome on a private flight toward Machadodorp. Shortly after takeoff, while maintaining an altitude of approximately 500 feet, the aircraft's main rotor blades detached from the rotor mast. The sudden loss of lift caused the aircraft to plummet into an open field roughly three miles from the aerodrome. The impact was severe, and a post-impact fire erupted, destroying the aircraft and resulting in one fatality.
The investigation
An investigation by the SACAA AIID examined the wreckage and the history of the aircraft's recent modifications. Investigators found that the engine had been functioning normally at the time of impact, as evidenced by the condition of the propeller and gearbox. However, the investigation focused heavily on the aircraft's rotor head assembly. It was discovered that the aircraft had undergone significant, unapproved modifications to its rotor head to reduce vibration.
Technical examination revealed that several components had been altered or improperly installed. Specifically, the main rotor bolt had been machined, a spacer had been reduced in size, and a required washer was missing from its proper position. Furthermore, the investigation established that the assembly process lacked proper oversight, as no maintenance manuals were utilized and no dual inspection was performed during the installation of the new rotor head.
Findings
- The primary cause of the accident was that the main rotor blades separated from the rotor mast because the bearing sleeve had been assembled upside down.
- A major, unapproved modification was performed on the aircraft after an Authority to Fly had already been issued.
- The assembly of the new rotor head was conducted without the use of a maintenance manual or parts catalogue.
- Critical components, including the rotor head, were modified without a formal Modification Approval from the appropriate authority.
- The installation of the new rotor head was completed without a dual inspection, representing a significant safety deficiency.
Safety action
- It is recommended that modifications to critical aircraft components be performed by the original manufacturer.
- The implementation of serial numbers for components used on non-type certified aircraft is recommended.
- The CAA should introduce measures to ensure that Authorities to Fly are issued strictly to registered owners rather than unregistered owners.