Max
At 300 hours the Airmaster controller on G-IANI indicated an open circuit
(all three controller indicators flashing red). After unbolting the brush
unit from the gearbox it was apparent that the middle brush had worn down to
the point were it no longer contacted the slip ring. The other two brushes
appeared to be about half worn. I could not find any rough area on the
middle ring which would explain why one brush had worn more than the other
two.
I replaced the brush (with the spare provided with the prop) which involves
dismantling the brush unit and soldering in the new brush. I have recently
(at 360 hours) removed the bush unit and checked the brushes. The middle
brush shows no sign of a high wear rate. The other two brushes show little
additional wear and I estimate will last to about 800 hours total time.
I contacted Martin at Airmaster to discus this failure. He told me that
this does occasionally happen. Airmaster has the brushes manufactured to a
specification but they have no way of checking individual brushes for its
wear characteristics. So unfortunately some brushes are slightly softer and
wear more rapidly. If you know what to look for you can spot this as more
black dust will be around the slip rings and hub.
Ian Rickard G-IANI XS Trigear, 300hours
Europa Club Mods Specialist
e-mail g-iani@ntlworld.com
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