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DEFECT REPORT
Engine Mounts
Strut Braced Drifter
Airframe 250 HRS TTIS
Engine 250 HRS TTIS
Following a one hour flight where no anomalies were found in
the B/F inspection the aircraft was parked in the hangar. A very
discernable tilt of the engine was observed when viewed against
the hangar vertical columns.
A closer inspection revealed a complete collapse
of both Left Hand engine mounts.
The left picture shows the L/H side Engine
mounts viewed from front to rear. The rear engine mount bottom
portion had totally collapsed and the front one had disintegrated
but still in place.
The R/H side engine mounts were still
serviceable.
Above is a view of the L/H front and rear engine
mounts and a serviceable R/H engine mount. The spacer tube for the
engine mount bolt is also pictured.
The engine mounts were replaced with spares held from another
similar drifter.
I noted that the spacer tube from my spares were 12.55mm OD and
a loose fit through the mount, whilst the ones I removed measured
13.09mm OD and a tight fit.
Likely analyses would indicate that either:
- the neoprene compound was defective or affected by heat as
both were in the vicinity of the exhaust.
- Possibly, the increased OD of the spacer caused stressed
in the material that caused it to peel back the way it did.
The rapid onset of the problem without prior warning signs is a
cause for concern. Had it been a lengthy flight severe vibration
would have been a likely outcome.
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