Mailing List flyrotary@lancaironline.net Message #64229
From: Andrew Martin andrew@martinag.com.au <flyrotary@lancaironline.net>
Subject: wiring
Date: Sun, 12 Aug 2018 09:41:01 +0800
To: Rotary motors in aircraft <flyrotary@lancaironline.net>

Just found the cause of an intermittent problem I've been having. Seems over the last couple of weeks I thought I had been flooding the engine on startup, Well, I had but not from what I thought. For absolute years I've never really had any issue getting the engine to start. but then just as I'm about to start flying again occasionally it would be impossible to start. turns out the ignition fuse was acting like a resistor.
Was hard to diagnose as just touching the fuse made it work so every time I put the multimeter on it it would show as ok, and volts at the coils was only ever slightly lower but obvious now at very low amps. and if by luck when the engine did start it would continue to run( guess due to extra couple of volts from alternator) so no inflight failure, but would only have been a matter of time.

Anyway now when I should be right in my test phase, I'm back trying to figure out if I need a redundant power supply for the engine. hard because of the type of failure and there are so many single point failures possible its kind of pointless trying to mitigate them all.

The problem area was the contact surface between fuse & fuse holder, Not sure if I got a dodgy fuse block or if its just the environment.
So do I duplicate the engine power bus, switches & wiring with diodes where the systems join at each component( lots a work) or just put it down as a totally random failure & just check & clean fuse panel connections as part of the annual inspection?

Andrew



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