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912 alt output

N162RV

N162RV

Active Member
While at SNF I was talking to a technican from Lockwood about the 912 electrical system and he indicated that the output of the altenator was 18.5 amps max and really should stay at no more than 14 amp contast.

Anybody know what the load would be on the -12? Not to mention adding AP and lights....
 
Scott,
I did a quick estimation of the max load from the published equipment list plus 2 AP servos and an LED Position/Strobe setup(AVEO Flash) and came up with a max load of 11.7 amps. I used the max power draw instead of normal, so this number would represent all the equipment operating at max all at once. (Both AP servos moving, transmitting on comm, transponder transmitting, Dynon backup battery charging, strobes flashing, etc.). Fuel pump is not in estimate.
 
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the alternator is running the ignitions as well, isn't it?

Our AirCam has two 912 ULS engines, and is equipped with whelen nav/strobes, Apollo (now garmin) transponder, GX-65 NavComm, ps engineering intercom, an electric turn coordinator, and EIS engine monitors. The landing lights are a pair of Autozone driving lights.

Also two facet pumps which are on in the pattern.

With everything on, voltage will sag at idle. The lights collectively are the biggest draw, but we have two alternators.

On a -12, if considering lights, I would look real hard at LEDs and/or HID.
 
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I know my dynon is running on 3 amps, the ap runs on about that. If you have leds you should be ok. Now, if you plan on using a heat vest for winter ops, you might need to turn them off once you land. Seems the rotax standard alt. is not so good at idle. At least mine runs a little lower on the ground. If I have my strobes and heat vest on, the radio sometimes doesn't transmit very well. I just turn one or the other off and I'm good.
 
Some pilots flying Rotax 9XX engines have learned that the Ducatti regulator is a weak (and expensive) link. Keeping the current load low (say less than 10 amps) helps a lot and providing a flow of cooling air over it is also helpful.

Gilles in France has a very informative article on his website about the Ducatti regulator and his analysis of it.
http://contrails.free.fr/index_en.php

I'm posting this just for information purposes. There are many flying with no problems.

Jim Butcher
Europa XS Rotax 914
 
h&jeuropa said:
Gilles in France has a very informative article on his website about the Ducatti regulator and his analysis of it.
http://contrails.free.fr/index_en.php
Click to expand...

That's very informative, thanks for posting it. Here is a direct link to the article on his website: http://contrails.free.fr/elec_ducati_en.php

I talked to an LSA owner last week who was highly interested in full electrical system redundancy for his VFR-day-only airplane. Maybe the thing I didn't catch is that the Rotax regulators live hard and short lives?

I wonder if B&C makes a regulator that will work for the Rotax...

mcb
 
Matt.

No, B&C doesn't have a replacement regulator. There is a German regulator that is supposedly better but the manufacturer doesn't care to export to the US. Gilles mentions it on his website.

For experimentals, Rotax makes a aux alternator and the B&C vacuum pad alternators will fit. I think the RV12 cooling shroud prevents the fitting of any vacuum pad device.

In my Europa, I devised a crankshaft driven alternator provides about 35 amps and works fine.

Jim Butcher
Europa XS
Rotax 914
 
I talked with Van at Sun n' Fun. He showed me the nav/strobe lights proposed for the RV-12. The are AreoLED's, Pulsar exp. model. They draw 2.5 amps @ 12vdc. That is with strobes in use. You can see these at www. AreoLEDS.com.
 
flyeyes said:
the alternator is running the ignitions as well, isn't it?
Click to expand...
Yes and no. The ignitions are run off the alternator, but from separate coils - it's not part of the 12V output.

Remember that output is very much a function of RPM, so with all your avionics and (for example) a 100W landing light, the battery is going to be discharging.

TODR
 
I have one installed

I have installed one and did modify my cowling, but no bump. See my post from earlier this year. The Cowl is longer and used a prop extender with a 3 blade. Also modified the mounting bracket lowering it so it would fit under the cowl.

http://www.vansairforce.com/community/showthread.php?t=85230

I built my 12 as an EAB not a ELSA. I use the 40 amp as the primary and the Rotax Gen as the backup. They are controlled by the vertical power and manually turn on and off. If needed I flip to the Rotax Gen and can shed the load by turning off the 2nd EFIS and other equipment as needed.
 
Gen 2

Another alternative (Tho Expensive..!) SportairUSA have a rear bolt on Alternator that Piggy backs on the Original Eng Alt. & puts out 26 Amps looks like a list price of $3575 USD............also a souped up Rotax 912 engine!
Have a look..!
 
2nd Alternator Required???

With the future installation of ADS-B equipment into the RV-12 cockpit, will the standard single alternator output continue to handle the additional load requirements and remain within operating limits, or will a second alternator be required?
 
No one but vans has the load calcs in detail. But go to this thread and check the links from it. http://www.vansairforce.com/community/showthread.php?t=80077. There is an EAB with dual Skyview in the UK with no problems. The CTLS is dual Skyview plus lights plus other stuff including electric flaps on the standard system. The RV12 Skyview mod electrical distribution avionics connector box comes standard with the option for plugging in a Garmin 496 or similar and an ADSB box in addition to that. I am not worried at all about adding an ADSB box and intend to. There is a thread about a wiring mod to measure the actual output being used in flight -which would be really interesting - but I don't think anyone has done that.
 
Bill H & mrt890,

Thanks for the info. I am just beginning my research on the 912 engine and systems.

Regards,
 
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