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I posted this on the Corvair website but thought someone on this site might have some thoughts.
In WW's manual it calls for a direct wire from the battery to the A/B switch for the pumps and coils.
That means that either A or B will always be hot, unless the switch is in the center "OFF" position. If the switch is on the B side when the engine is shut down, you would have current flowing through the mechanical points if they are in the contact position when the engine stops.
Would it be best to put an “ON-OFF
” switch in this line, or rely on the center off position of the A /B switch?
That would work as long as you don't shut the engine down with the mixture control and forget to switch the A-B to neutral position.
I have Bob Nuckolls book, just need to take time to set down and read it.
The main reason aircraft have "always" been shut down with the mixture is because of the magneto ignition. If the mags are hot because of a bad "P" lead or because the last pilot forgot to shut off the mags, the engine wants to start if you move the prop. With the electric (rather than magneto) ignition in the Corvair (and in Rotax engines for that matter) when the ignition is switched off the engine will not fire if you move the prop. For that reason WW (and Rotax) recommend that you shut it down with the ignition switch(s). If you add another switch into the circuit you are just adding another possible failure point, in my opinion. There is no reason to shut down with the mixture as far as the health of the carb or anything goes, it just has "always" been done that way to add a layer of safety because of the magneto ignition.