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Old 11-06-2022, 12:25 PM
JMFord JMFord is offline
Join Date: Sep 2019
Location: Keller, TX
Posts: 9
Default 912is electrical output

I'm thinking about mounting a heated pitot tube on the wing. Does the 912is generate enough amps to handle a heated pitot tube and the IFR avionics package?

If not, can you mount a B&C alternator or the Rotax additional alternator? I called Vans and they don't think it will fit in the cowling without heavy modification.
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Old 11-06-2022, 12:37 PM
jrtens's Avatar
jrtens jrtens is offline
Join Date: Apr 2018
Location: Seattle
Posts: 288

Definitely enough. The B generator which powers the main bus puts out 400 watts or around 30 amps. In fact this large output can cause a problem for the B voltage regulator on a hot day - see

For reference, with everything on - dual screens, all lights, autopilot - I am using 11-12 amps. You will use an additional
8-10 amps for a short time while the battery is topping off after start.
2019 12iS SLSA
Arlington Muni

Last edited by jrtens : 11-06-2022 at 01:47 PM.
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Old 11-06-2022, 01:26 PM
JMFord JMFord is offline
Join Date: Sep 2019
Location: Keller, TX
Posts: 9

Thanks Jon,
According the the Rotax manual:
The internal generator has two isolated coils integrated (individual generators). During the starting operation, the EMS system is powered by the battery. With sufficient speed generator B takes over this function. After the EMS system check, generator A takes over the supply of the EMS system (engine), if the switching threshold is exceeded. Generator B is then used to supply the aircraft instruments and for charging the battery.
While the engine is running, the generator B can be used for the aircraft instrumentation.
• Generator A 14.2 V/16 A (220 W nominal capacity at 20 C/68 F)
• Generator B 14.2 V/30 A (420 W nominal capacity at 20 C/68 F)

Garmin says the GAP 26-20 regulated pitot tube peaks at 12 amps when it first warms up but then only draws around 6 amps to maintain the regulated temp.

So as long as I don't turn on the pitot heat right after engine start, the math should work.

Last edited by JMFord : 11-06-2022 at 01:29 PM.
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