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Date: Sat, 05 Aug 2006 15:20:53 -0400
From: Chad Robinson <crj@lucubration.com>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: Alternator failure quits engine
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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