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Thread: Glide Ratio Model IV

  1. #1
    Senior Member Wheels's Avatar
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    Default Glide Ratio Model IV

    IS there a published or approximate or wild guess as to the glide ratio of a model IV?
    Its a parameter in the set up for Foreflight and while I don't expect to actually be that focused to my iPad, it might be nice to know.

    Im thinking Best Glide as opposed to minimum sink. I guess I can stick it at 65 mph and read the handheld version of a Garmin GPS with that feature, but, if you know, ... do tell.

  2. #2
    Guy Buchanan's Avatar
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    Default Re: Glide Ratio Model IV

    From flight test, gross weight (1200#), temperature 60F, DA ~4500', engine idling (912s): glide ratio was about 8.6 at any speed over 60 mph. (Almost constant up to tested speed of 85 mph.) I did not test engine out. For reference minimum sink was 550 fpm at 45 mph. I did not test below 45 but looking at the curve I suspect it doesn't go much lower. (See attached.)
    Attached Files Attached Files
    Guy Buchanan
    San Diego, CA
    Deceased K-IV 1200 / 912uls / 70" Warp 3cs

    gebuchanan@cox.net

  3. #3

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    Default Re: Glide Ratio Model IV

    WOW! This is why I log in and read "New Posts" daily.

    I have suspended work on my IV 1200 since hurricane Irma because of the cleanup and restoration workload. lost electric for 6 weeks, lost storage building where the Kitfox was stored but damage was to a wing and flaperon. electric restored temporarily and downed trees removed this week. Flood debris and crud left on items now pressure washed, and a replacement flaperon acquired due to the generosity of a kitfox builder. Replacing the storage barn will soak up any discretionary money so Kitfox priority slips downward. pre-formed windshield and prop were bought before storm so only paint and incidentals remain a cost, but any builder knows how those incidentals add up.

    So, I will follow the forum and get back on the project in the coming weeks. The Forum keeps motivation high.

    By the way, I have selected the two blade medium IVO ground adjust prop. Need a spinner. Any suggestions.
    Bud
    IV Speedster
    912 UL
    IVO ground adjustable

  4. #4
    Super Moderator Av8r3400's Avatar
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    Default Re: Glide Ratio Model IV

    Spinner: What look are you wanting? I really like the simplicity of my "skull cap" spinner.

    IMG_1879.jpg

    IMG_2952.jpg


    It's the 5" version. My Prince will be a similar size at the hub to your IVO medium.
    Last edited by Av8r3400; 11-18-2017 at 08:47 AM.
    Av8r3400
    Kitfox Model IV
    The Mangy Fox
    912UL 105hp Zipper
    YouTube Videos

  5. #5
    Senior Member Slyfox's Avatar
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    Default Re: Glide Ratio Model IV

    glide ratio of the 4. ha, I can tell you not much when the fan quits. now I had the experience of just that at 1000ft agl. I didn't fool too much with getting it started. I just located a nice field and went for it. sure it flew, yes it was quiet. I got down to the surface, maybe 5 off and noticed I was at 60mph. I went and pulled back for a nice landing and it dropped lock a rock. without the fan, any figures you may have for glide ratio, I say throw them out the window. these things drop below 60 was my experience. I held 90 all the way to the field I wanted to use. leveled and started to pull back at 60 and it dropped right out. so there you have it.
    steve
    slyfox
    model IV 1200-flying
    912uls
    IVO medium in-flight
    RV7A-flying
    IO-360
    constant speed prop

  6. #6
    Senior Member jiott's Avatar
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    Default Re: Glide Ratio Model IV

    I know this thread is about the model 4, but FWIW the model 7 SLSA specifies about a 10:1 glide ratio with engine out and prop windmilling, and slightly better with prop stopped. This is from the SLSA POH, which I assume is a tested number since it is a certified aircraft.
    Jim Ott
    Portland, OR
    Kitfox SS7 flying
    Rotax 912ULS

  7. #7
    Senior Member Wheels's Avatar
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    Default Re: Glide Ratio Model IV

    Awesome gouge, thank you all.
    I bought a new engine for this plane and am finally getting back on track for the install. Guy Buchanan, thank you for the graphic and info. Very helpful. As for windmilling or idle, or stopped, the term of importance is (flat nosed or flat surface drag) it changes your world. If you don't believe me, fly without your spinner for a test ... just once, your normal sink rate for landing will be out the window.
    I"ll plug in Guys numbers for reference in my
    Forflight program until I"m flying and done testing.
    Wheels

  8. #8
    Senior Member
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    Default Re: Glide Ratio Model IV

    During flight testing on my Series 5 Outback , I came up with a 10:1 glide ratio so as a rule of thumb (no wind) I figure 2 miles per 1000' AGL . I practice engine out stuff on most flights and have found as mentioned above, that you better maintain that best glide speed energy right to a low level flare or you will drop like a rock right at the end. The Kitfox is a great glider just practice maintaining your energy right to the end. Never do the old pull on the stick caus those trees look to close, that would spell trouble. A full slip in my plane will bring me down in a hurry, so higher is obviously better with that slip in my bag of tricks to make a field. Practice this stuff regularly so when the time comes it will be no big deal and you won't wet yourself. Bruce N199CL

  9. #9
    Senior Member Slyfox's Avatar
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    Default Re: Glide Ratio Model IV

    one more thing prop windmilling. Not a chance. at least with my 912uls. I had a landing spot under me. I did a spiral down to land at 90mph. that prop didn't budge. all I can say is be careful with engine stop. it does not glide like you would think. amazing how even the engine at idle how much that kitfox will not want to stall.
    steve
    slyfox
    model IV 1200-flying
    912uls
    IVO medium in-flight
    RV7A-flying
    IO-360
    constant speed prop

  10. #10
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    Default Re: Glide Ratio Model IV

    FWIW .... the attached image of Fig 12.3 is an extract from the FAA handbook "Airplane Flying Handbook", section 12; (I recommend this handbook if you don't already know about it).

    In general, I guess most of our prop blade angles are in the lower range, so we may not see much difference in drag between a windmilling and stationery prop, except if you have a very flat blade angle as in a fixed pitch prop optimised for T/O performance. That's probably getting close to a spinning solid disc. For a prop optimised for cruise, you may be better off, but then if you have an inflight adjustable, parking it at as coarse a pitch as possible following the sound of silence might be a good idea !

    For mine, L/D glide tests and engine out practice sessions on a regular basis is certainly on my to-do list when I finally get my project up and running.
    Attached Files Attached Files
    Last edited by David47; 11-19-2017 at 04:08 AM.
    David
    SS7 Builder

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