Jabiru UL-D, G-JAAB, 12 September 2007
Jabiru UL-D, G-JAAB
During flight the pilot noticed the sudden onset of vibration from the engine. Whilst on the approach to a field for an emergency landing the engine stopped. Examination of the engine revealed that the No 3 cylinder exhaust valve had failed in fatigue and that the remaining three exhaust valves had fatigue cracks in the same areas as the No 3 valve had failed. The engine had operated for 121 hours since it was manufactured and had Jabiru Service Letter JSL 002-1 titled ‘Jabiru Engine Economy Tuning’ embodied. During this investigation the cylinders and pistons from another Jabiru engine, that had been fitted to a Thruster microlight, were sent to AAIB following a failure of No 1 cylinder exhaust valve. The metallurgical examination of all four exhaust valves indicated a very similar failure mode and fatigue cracking as those from G-JAAB. The engine had operated for approximately 300 hours since it the valves were replaced and had Jabiru Service Letter JSL 002-1 titled ‘Jabiru Engine Economy Tuning’ embodied. Two Safety Recommendations are made to the Australian Civil Aviation Safety Authority.
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