Larry, you wrote: << Looking back, I think I've been flying on borrowed time the last flight or two. I've noticed my small back up battery didn't look right on the volt meter but everything was working o.k. My main battery is so hefty that I've been starting the engine and running the pumps and the radio on it without recharging for at least an hour or two now. The lesson here is a gradual failure will give you hints if you bother to pay attention. If something doesn't seem quite right it probably isn't. >>
You need a low voltage warning indicator. It gives you immediate annunciation of a failed alternator. There is approximately a 1.5 volt difference between a fully charged battery and the output of your alternator. This difference, 14 volts down to 12.5 volts gives you a transition to monitor for safe flight. Typically the low voltage warning will go off around 13 volts so that when your alternator fails, you have a fully charged battery to complete the current flight safely with battery only operation. You can build you own low voltage warning indicator for $10 worth of parts using a schematic supplied by Bob Knuckles at his web site http://www.aeroelectric.com or you can purchase a fully assembled product from him if you desire. He has a book "Aeroelectric Connection" that you can purchase or you can download the pdf for free. It is a wealth of information that you can use to keep your bird safe. The most significant section of the book deals with his philosophy of reliability. He doesn't propose that we strive for zero failures, because failures will happen. He builds a case for designing an electrical system that provides the ability to safely complete each flight to the exhaustion of available fuel on board. A combination of information and pre-planned proceedures leads to overall system reliability and safety of flight. This makes the alternator failure a maintenance item rather than a flight safety issue. Hope all goes well with the alternator repair so that you can fly to the Gatering. See you in 5 days! Regards, Bob Lee N52BL KR2 Suwanee, GA USA 92% done only 67% to go!
