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Thread: Rotax 912 100hp limiting for short field take-off and climb?

  1. #1

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    Default Rotax 912 100hp limiting for short field take-off and climb?

    I know this question has almost been beaten to death, but I feel like it hasn't quite been answered in the way that I like; thus I will be more specific.

    If one were to build an STI kit and install a 100hp 912 (injected or carb) with CS prop in the aircraft, would that plane be limited in its take-off and climb performance to a point that one might say "darn I wish I would have installed a 914"?

    I know that there are a million factors in this question so I will narrow it down to avoid rabbit holes. Pilot skill and comfort arenít the main limiting factor. Fuel burn and speed arenít an issue. Only stock Rotax engines are being considered. This plane would almost exclusively be used for backcountry/mountain/off-field flying. The plane would ideally have the capability to operate within reason on hot days at high altitudes in the west (Rockies, Cascades, Sierras, high desert, etc.). The plane would could be loaded with 2x200lbers and minor bags or it could be light on fuel with 1 SOB.

    Some follow up questions to further capture the spirit of this question:
    Would there be strips in Idaho that would be out of reach due to the engineís capabilities?
    If a friend had 160hp super cub, would the 100hp 912 be enough to keep up?
    If a friend had a carbon cub, would the 100hp 912 be enough to keep up?

    Iím in principle asking if one needs a turbo and/or an extra 15-35hp to have a killer bush plane. It would be helpful to hear from people who have flown the 100hp and have met its limits.

    Best of Luck,
    Roger

  2. #2
    Senior Member efwd's Avatar
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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    Ive flown my KFS7 with a 912iS heavy. 400# up front minimal weight in the baggage area. Fixed pitch and at 2000ft DA it took off great from pavement. If I had an IFA prop it would exceed 1000ft/min climb. Mine is not a STOL wing. It seems that you have the cash to enable you to even contemplate the 914 so given those additional criteria you site (hot, high, confined space), IMHO, I would spend the money. I find I will not be doing that much back country landing so I like my set up. I would love to have the IFA prop though. Keeping it LSA though. Good Luck
    Eddie Forward
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    SS7, 912iS, Garmin G3X

  3. #3

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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    This question is a no brained. I fly a 100hp Kitfox and I love it. But I wish I had more power. Not because I need it but because I want it!

  4. #4

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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    Very helpful thoughts. I might as well put a turbine!

    I have a feeling that I would always want more power. How badly would you say that you wish you had more power? Is it a "gosh that was scary. I wish I had more power"? Or a "I wish I had more power because that would be totally awesome"?

  5. #5
    Senior Member aviator79's Avatar
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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    If you can afford a turbocharged engine with a CS prop, you will love it. However, Stick and Rudder operates with a 912iS/airmaster equipped airplane with a standard Super Sport wing all day long in the Idaho Backcountry, and Paul L. is not a small guy, so they fly pretty heavy. I think you'll find few strips out of your reach without the turbo, and with practice, you'll keep up with cubs just fine. Scott Noble flies a 912 with Airmaster and lands on some pretty short gravel bars with his cub buddies just fine. That said, he's eyeing a turbo for his next engine.

    You'll definitely never say "Man, I wish I didn't have this turbo".
    --Brian
    Flying - S7SS

  6. #6

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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    Quote Originally Posted by rwoneill View Post
    Very helpful thoughts. I might as well put a turbine!

    I have a feeling that I would always want more power. How badly would you say that you wish you had more power? Is it a "gosh that was scary. I wish I had more power"? Or a "I wish I had more power because that would be totally awesome"?
    I took off from Bruce Meadows (6400í) on a warm day and only got 4-500 fpm. I have a stock 912 and an Airmaster prop. It wasnít unsafe. Just have to be more patient. I want more power because I want more power. Iím used to flying jets that have way more thrust than is required and itís has spoiled me!

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    desertdave's Avatar
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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    Quote Originally Posted by GuppyWN View Post
    Iím used to flying jets that have way more thrust than is required and itís has spoiled me!
    You couldnít have said it better. To quote Jeremy Clarkson, ďMORE POWER!!!!Ē
    Dave
    KitFox 6 Nosedragger

  8. #8
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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    ďI wish I had less powerĒ said no one....ever!
    Dustin Dickerson

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

  9. #9

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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    All very helpful.

    Clearly more power is better but it seems like it can be done without. It's not whether or not I want more power (who doesn't?). It's whether I need more power to have a capable machine. More power is worth a lot of hamburgers.

    I'm thinking I will just fly the pants off of a 912 with an IFA prop and go big on the second engine. More power will be had, just maybe not today!

    Still undecided on fuel injection but leaning heavily in favor of it.

  10. #10

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    Default Re: Rotax 912 100hp limiting for short field take-off and climb?

    Can I steal the thread for a question or two?

    The original question he had was pretty spot on with what I wanted to know also as I am doing research. The replies were great. Now I was wondering the good and bad for going with fuel injection vs.carbs I have never flown a injected plane yet and have don some research but any first hand knowledge is welcome.

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