Electrically dependent management question ?

[Larry DeCamp]

I conclude your management philosophy will/should affect system design. Assuming the alternator is lost, and you have two batteries, will you get the most duration by killing the second ignition (current draw) or using up all the battery you have on board with two ignitions ? I currently have two Pmags and can hardly perceive when one is grounded in flight. Your thoughts appreciated?

[Ironflight]

In the dual P-Mag case, it makes no difference what you do with your electrical system/battery/alternator once the engine is running above about 700 rpm - each P-Mag is generating its own power, and will run the engine until you run out of gas - even if all the battery electrons are gone.

[Toobuilder]

If "time aloft" (duration) is the requirement, and assuming fuel will outlast the batteries, then less electrical load will equal more duration.

I'm assuming the pmag reference is only used as the indicator of your observation of engine performance on a single EI.

[Larry DeCamp]

Sorry Paul, I was not clear. Tool builder addressed my concern. There is a lot activity currently regarding electrically dependent system design. So for me,(day VFR), I think Toolbuilder’s conclusion can support a relatively simple system. That said, it concerns me about buying a second hand homebuilt in the EI / EFI era. Even the electrically skilled RVer’s differ in system design.

[rleffler]

Why would buying an used aircraft cause more concern? Especially if the price is right. If you don't like what they did, just change it.

I had a friend that recently purchased a RV-4. He's about ready to completely redo some of the electrical system due to a not optimal configuration.

bob

[Larry DeCamp]

You are making my point from 180 degrees away. If you are not qualified to make the judgement your friend did, then what? And another thought I wanted to share is documentation. In this environment (as opposed to steam gauges and magnetos), system documentation should be fairly complete and understandable. I am proposing that elegant documentation ( including fault analysis ) and workmanship will significantly enhance marketability or compress the tire kicking phase for knowledgeable buyers.

[rleffler]

Originally Posted by Larry DeCamp

You are making my point from 180 degrees away. If you are not qualified to make the judgement your friend did, then what? And another thought I wanted to share is documentation. In this environment (as opposed to steam gauges and magnetos), system documentation should be fairly complete and understandable. I am proposing that elegant documentation ( including fault analysis ) and workmanship will significantly enhance marketability or compress the tire kicking phase for knowledgeable buyers.

If you're not qualified to perform the analysis and you don't have a friend that is qualified, I would think hard about purchasing an EAB is the correct decision. Otherwise you are putting quite a bit of blind trust with the original builder, and if applicable, any subsequent owners.

I fully agree about documentation and ensuring it's current. Not just schematics for the electrical system, but data wiring schematics as well. Also, not to over look transponder checks, pitot-static checks, maintenance records, etc.

One of the things that initially caught me off guard as a Technical Counselor, was the amount of calls that I get from folks that have absolutely no clue about how things work in their aircraft.

If you purchase an EAB, you better have the expertise to understand all the systems, or have a close friend, or trusted A&P that does. Otherwise you are taking on some unknown risk. If you don't have the expertise, you need to find a mentor to help you through the process.

In the case of my friend, the 2nd owner rewired the power and didn't document his work. The only information my friend received was that he used a Nuckoll's schematic. Now my friend has to play detective. He purchased the Nuckoll's book and determining if it's a Z-11 and if so, is it wired per the original schematic or are there deviations. He's teaching himself in the process, but he does have access to several SMEs to provide advice.