What happened
On 28 November 2012, a Jabiru SP 2000, registration ZU-OIL, was conducting a private flight from Rustenburg Aerodrome to Springs Aerodrome. The flight proceeded without incident for approximately one hour. However, while the pilot was reducing engine power on the downwind leg for landing at an altitude of roughly 6400ft AMSL, the engine experienced sudden vibrations and ceased operation.
The pilot issued a blind radio transmission on frequency 122.4 MHz to report the engine failure before executing a controlled forced landing on Runway 02 at Springs Aerodrome. The pilot escaped the incident with no injuries.
The investigation
An investigation by the SACAA AIID focused on the mechanical state of the engine and the circumstances of the power reduction. While the aircraft airframe remained intact following the landing, the engine and propeller sustained significant damage. The engine mounting cradle was distorted, and the bulkhead behind the engine was dented.
Technical examination of the Jabiru 2200A engine at an approved maintenance facility revealed that the failure originated within the second cylinder. Investigators found that the inlet valve had made contact with the piston crown, leading to the valve severing from the connecting rod. The examination also noted that the lower portion of the piston was destroyed, along with damage to the oil rings and grooves.
Findings
- The primary cause of the engine failure was a mechanical failure of the piston No. 2 gudgeon pin wire retainer circlip, which became adrift.
- This allowed the gudgeon pin to migrate forward out of its proper position.
- The resulting displacement caused the engine to stop abruptly, which in turn caused substantial damage to the propeller and the engine mounting cradle.
- The pilot was operating with a valid private pilot license and medical certificate, and the flight was otherwise uneventful until the mechanical failure occurred.