On 10/14/2015 01:50 PM, Mike Stirewalt via KRnet wrote: > It's coming down and > getting back up in the air again when conditions are stressful - that's > when you need something substantial. If you are stuck on a ramp > somewhere in Wyoming in winter, for instance, lets say it's 2 AM > (airplanes do fly at night you know) with a piss-ant battery the nearest > Auto Zone might as well be on Mars, you aren't going anywhere.
I think you've completely missed the point. Both Larry and I have "substantial" primary batteries, as well as alternators. The chances of both of those failing within a single flight is practically nil. The alternator will power the systems forever, and the main battery will do so for at least a couple of hours, which is plenty of time to land safely. On the extreme slight chance that BOTH the alternator and the primary battery fail, the secondary battery provides adequate duration to make a safe landing. There is simply no need to have TWO heavy "substantial" batteries in the airplane. If any part of the electrical system is compromised, I'm not silly enough to take off at 2am in the middle of winter in Wyoming. I'll go get a nice warm hotel room and fix the problem in daylight, preferably in a heated hangar. Although you do so somewhat insultingly with your "don't have a clue" comment, you are correct about designing the electrical system to support the purpose of the airplane. If you have a simple day VFR flyer, a single battery and alternator is plenty (although my Luscombe buddy would say you don't even need that). I have a fully equipped day/night IFR aircraft, with an all glass panel and electronic ignition (on half, mag on the other half), with a redundant electrical system offering three independent sources of electricity. If I thought that wasn't adequate, I'd add a second alternator (less weight than a second large battery, and provides electricity far longer), but realistically the chances of all three of my existing power sources failing on a single flight is so vanishingly small that it isn't worth considering, IMHO. -Dj -- Dj Merrill - N1JOV - EAA Chapter 87 Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/ Glastar Flyer N866RH - http://deej.net/glastar/
