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al p wick wrote:
Lot's of value to cross posting stuff like this Ed. When we look at auto
conversion history, it's clear that loss of electrons is one of the top
10 causes for dead stick. We know there are patterns to failure causes.
If our plane crashes, it will be a repeat of something from history.
Good points, Al. IMHO, good electrical system design doesn't receive the attention it deserves in automotive conversion installations. There's plenty of discussion about cooling and fuel system design, but very little about wiring. I believe electrical design is every bit as important, if not more so because it will stop an engine entirely - at least with inadequate cooling you can DECIDE to try to run the engine at partial power to help you reach a field. Aircraft engines aren't so sensitive because they have gravity-fed fuel and magnetos, but we can't afford to ignore this in automotive conversions.
Alternators are common failure items even in cars, and their failures should be planned for, and, (your favorite topic Al!) monitored for during flight. It's simple to detect this via a current meter on a shunt from the alternator, so crashes due to this problem should be very avoidable.
It's not enough to simply have a backup alternator. You need a solid electrical system design that allows you to: 1. Detect the problem quickly, and 2. Follow an established response plan, routing power to crucial devices, without compromising flight safety by inventing solutions in mid-air. With a good electrical system design, you can easily achieve 30-60 minutes of engine run time even if the alternator fails, and if your battery/batteries are big enough, that could be several hours. Bob Nuckolls (on the Aeroelectric list the post originally came from) is a big advocate of this.
This rant is not to say that you should never expect to lose power. Wiring faults or damage, massive overloads (lightning? rare but possible), or just device failures (lose your ignition computer and where are you?) can all stop your engine. But, an alternator failure doesn't have to be one of them.
Regards,
Chad
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