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Thread: Rotax

  1. #11

    Join Date
    Sep 2017
    Location
    Raleigh, NC
    Posts
    20

    Default Rotax

    Wo, this is the first I’m learning about this potential issue with the Edge Fuel Injected engines. The Rotax 912 engines have THREE power sources built right into the engine. 3 engine driven stators. Adding an alternator would be a 4th! In the carbureted models, there is 1 stator per electronic ignition and 1 to drive the main bus for cabin power. If the voltage regulator dies, I do not believe it effects the engine at all. Someone please correct me if I’m wrong.

    Does the Edge EFI rely on the voltage regulator to be working? Are all the stators still in use? Seems like a bad idea to have a single point of failure in an aircraft engine.


    Sent from my iPhone using Tapatalk
    Brian Cass
    KF Model IV Speedster
    Rotax 912UL

  2. #12

    Join Date
    Dec 2009
    Location
    Lawrenceville, GA
    Posts
    173

    Default Re: Rotax

    Yes, it's hard to defeat the redundant ignition on the Rotax. As long as the fuel and oil keep flowing that fan will keep spinning. Even loss of coolant won't force a landing but can cook the heads.

    But the 912iS can have similar issues to the Edge. I think it does have built-in dual power sources for electrical but I saw a you-tube video of a *nice* LSA with a 912iS that had to land in a field due to an electrical problem so the system design has to be right.

    https://www.youtube.com/watch?v=XTN68B4vry8
    Last edited by napierm; 09-19-2022 at 10:30 AM.
    Building a KF IV Classic

  3. #13
    Senior Member
    Join Date
    Dec 2017
    Location
    Mapleton,UT
    Posts
    1,061

    Default Re: Rotax

    Quote Originally Posted by skyguy04 View Post
    Wo, this is the first I’m learning about this potential issue with the Edge Fuel Injected engines. The Rotax 912 engines have THREE power sources built right into the engine…
    The edge efi does not rely on the voltage regulator to run and I am not sure where you got that? I can think of many single points of failure on even the most advanced “single” engine. Single fuel source, single oil pump, single crank, single cam, single master solenoid, ect. At the end of the day still a single engine that a single failure can take it out. Point is on a efi your electrical needs to be well thought out and have multiple power sources IMO.
    Last edited by Shadowrider; 09-19-2022 at 10:15 PM.
    Dustin Dickerson

    Building 7ss STI x 2
    Oratex
    29" shock monster
    EP912STI 155hp
    Garmin
    N33TF......FLYING!
    N53TF......FLYING!

  4. #14

    Join Date
    Dec 2019
    Location
    Idaho
    Posts
    84

    Default Re: Rotax

    The stock 915is has 2 generators. One for the engine and the other for the "rest of the plane". If one fails, the engine automatically switches over to the still-good generator
    and disconnects from the "rest of the plane". If that generator fails you then can run from your main battery. The 915/912 engines need 8 amps to run everything including
    fuel pumps. So you'd use 4ah for 30 minutes of flight. The ETX-900 battery is 16ah so you could still run for a few hours on the main battery alone depending on how much load
    you can shed. The chances of 2 generators and a battery all failing at once is incredibly unlikely to happen. You probably have a higher chance of being taken out by a meteor.

    My question is do you really need that much redundancy? If you want to fly even longer you can use an ETX-1200 battery
    with a 24ah capacity which only weighs another couple of pounds. Cheaper and lighter than a backup alternator. With that
    you could stay in the air for maybe 4 hours.

    If you need more than 30 minutes to find a place to land you're probably flying somewhere you shouldn't be

    Victor
    Building SS7
    915iS
    Garmin G3x

  5. #15
    Senior Member
    Join Date
    Nov 2013
    Location
    Boise, ID
    Posts
    248

    Default Re: Rotax

    Quote Originally Posted by GAVM View Post
    I can confirm that I have fitted the EP915Eci with a constant speed Airmaster propeller to my Kitfox 5 Safari Speedster and it performs extremely well now - maybe too well! Could somebody tell how I could fit an auxiliary power system that would give me backup power for about 30 mins in case of an electrical failure.
    Talk to Thomas. He sells a second alternator.

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