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From: "Rumburg, William" <william.rumburg@cdicorp.com>
To: 'Brent Regan' <brent@regandesigns.com>, Lancair List
	 <lancair.list@olsusa.com>
Subject: Magnetos
Date: Fri, 21 Apr 2000 12:46:13 -0400
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> Sounds like you have been reading too much marketing information. The only
> real performance advantage to electronic ignition is the ability to
> advance
> the timing at low power settings and this is only on non turbocharged
> engines. A magneto is an elegant, self contained, 3 moving part solution
> to
> the ignition problem.
	OK...I have to speak up....
	   Magnetos are not invincible, they can and do fail. In fact, they
fail about once every thousand hours on average. What saves you is that
there are two of them, with no common mode, so the chance of two failing at
one time is 1/1000 x 1/1000 or 1/1,000,000.
	   I have dual electronic ignition, each with it's own timing
mechanisim plugged into a magneto drive. They are as completely independent
as magnetos, except for a common voltage source. A small, dedicated battery
eliminates failure due to a single voltage source. It's charge is maintained
by connecting it to the charging system through a diode. The electronic
ignitions are then switched to the dedicated backup battery with a simple
Emergency Power switch, whose operation is checked before flight. 
	   Electronic ignition's hotter spark ignites the flamefront more
positively than the weaker magneto spark. It sets to 0 degrees for starting
and senses both RPM and manifold pressure to adjust across the wide range of
optimal spark advance for aviation conditions. 
	   Magnetos are dinosaur relics of the 1930's.
	   Given all this, you could just as well sit around and worry about
a Martian Spaceship catching you in a tractor beam. A retired Lear Jet pilot
once told me that everything isn't redundant "God only gave you one heart"
	Bill Rumburg
	N403WR  (Sonic bOOm)
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