Additional Alternator on 912is?

[Geek]

Looking for some experience in adding an additional alternator to a 912is. I am looking at the 30 amp one from Edge Performance but know there is another one that is interfaced to the engine with a fan belt and believe it actually fits inside the cowling without mods. Specifically looking at what kind of penalty in horsepower do I pay when using either one.

Thanks ahead of time

Gary

[efwd]

Gary, you must have quite an extensive list of power consuming items. I thought I was loaded up, I don't need a second alternator for my 912is.

[Geek]

Eddie, Thanks. This is exactly the kind of input I was looking for. One thing I have learned working on aircraft electrical systems is that there is the theoretical load in the books and the real load when actually operating. My experience is that the latter one is less than what the enginerds quoted cause they were required to put in some safety margins. So I was looking for some real experience numbers. With your set up, how much current is your electrical system indicate that it's pulling?

I went through the loading listed in the books and got some "nominal" numbers (again engineers adding some safety numbers even when not at full load). Here's what I got

Garmin system (not transmitting the radio came in at 6A.
Landing, Nav and Strobe lites take 10.6A
Boost pumps (9A per pump) 18A

So that was a 35A pull. Before everyone jumps in to point this out, yeah I realize that these aren't pulling their loads at the same time and that the battery itself will make up the deficit and go back to getting a charge as the load comes off - a non event really. But that 30A alternator actually only puts out about 28A at higher RPM so regardless, that alternator will be running at almost full capacity just in normal flight. I also have a heated pitot tube that while I don't expect to use it that much or be flying at an altitude where it's cold enough for it to pull a full 20A, it will pull 10A if I do use it. Back when Orville and Wilbur were teaching me to fly, I was taught to turn on your pitot heat if you fly into rain and while I don't expect to operate that much in rain - it wouldn't be the first time if it does. Last but not least I am not really a fan of the Rotax system that will take over the 30A alternator if the 18A alternator that it uses to drive its critical systems dies. Again, I do realize that if it didn't, the fan in the front of the aircraft will stop turning which is bad. Sorry for the long winded answer but it just seems like I could avoid all this with an alternate alternator and the stock 30A could be my back up. But I'm still in the thinking process.

Again thanks for the input.

Gary

[109JB]

When I did my load analysis for my 912UL, I found that the conventional landing/strobes drew a bunch. I opted to replace with Kuntzelman LED nav/strobe lights that draw about 2 amps total. Also, I've seen some people calculate loads based on peak currents or what the breaker requirements are. Really need to use the running or average currents that the component manufacturer lists.

[3 tracks]

Geek Do you know the 30 amp from Edge will not fit between the flywheel and the engine mount . Without cutting the cross bar out of the mount. Maybe Dustin will chime in to ,that's what I had to do when I insalled there EP912 STI.

[Geek]

When I did my load analysis for my 912UL, I found that the conventional landing/strobes drew a bunch. I opted to replace with Kuntzelman LED nav/strobe lights that draw about 2 amps total. Also, I've seen some people calculate loads based on peak currents or what the breaker requirements are. Really need to use the running or average currents that the component manufacturer lists.

Good info on the lights. They are certainly bright but something has to drive them to get that. The numbers I was listing were the nominal numbers from the Garmin book. The radio for example had something along the lines of 1.5A when receiving, 3.8A average when transmitting and 7.5A peak. I used the 1.5 number because the others are a short amount of time and that's where we get to the part about letting the battery take care of the short term high current draw and then charge it back. Guess my real draw towards the extra/higher amp alternator is having one that isn't running full out and not having an electrical system that can be taken over without warning by the Rotax. The battery back up is another option I'm looking at. That at least would give me about an hour and half (without the lights) to still have avionics and find a place to land and fix the issue.

Geek Do you know the 30 amp from Edge will not fit between the flywheel and the engine mount . Without cutting the cross bar out of the mount. Maybe Dustin will chime in to ,that's what I had to do when I insalled there EP912 STI.

Dustin and I have talked. What a great asset he is and really willing to give you the value of his experiences. I am aware of the interference between the engine mount and the alternator (thanks to Dustin). That cross bar is a required support if you have a nose wheel configured aircraft. I understand removing it for a tail dragger is not a problem and believe I read somewhere that John McBean had verified that.

Thanks all for the inputs.

Geek