On 12/03/2012 07:53 PM, Rowland Carson wrote:
> installation. But the official Rotax electrical installation diagram
> (see attached) calls for screened wires (and even for the switch
> cases to be screened) so I see no reason to invite possible
> interference by ignoring that advice!
The official Rotax electrical installation diagram assumes that you
don't have a ground connection at the switch end of your setup.
Make sure you meet that assumption, or very unpleasant things can
happen. This means that you have to double check that no ground wire,
metal bracket, or whatever is attached to the ignition switch in any way.
Also, I still feel that the risk of accidentially shorting the ignition
wire to ground (with engine stoppage as a result) is higher in a
screened wire than in an unscreened wire. Sometimes aircraft
manufacturers follow a standard approach without considering other
options, options that might be better in that specific situation.
The screened ignition wire really is a Lycosaurus thing.
Anyway, a sensible compromise might be to use the screened wire, but to
keep one of the ends of the screen disconnected, and to run a separate
ground cable to the ignition switch. This to avoid any possibility of
running ground currents through the screen, which might melt the core
and screen together, leading to engine stoppage.
If I would ever get corrosion on my battery or alternator ground
connection, I would prefer a failure of my electrical system but with
the engine still running, than the ignition screen taking over the
ground connection for a short while before melting everything together,
and giving me an electrical failure PLUS an engine stoppage.
Frans
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