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Thread: Full Flap Use

  1. #1
    Senior Member jiott's Avatar
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    Default Full Flap Use

    I just built and am now flying off the 40 hours of my SS7. I am also a fairly new pilot with 160 hours total (in a Kitfox). Training in Boise with Stick & Rudder in their SS7 SLSA I always used full flaps for landings. On my kit built SS7 the full flap position is much more aggressive than the SLSA, and it was recommended to me by many on this forum and also John McBean that I use 1/2 flaps for landings until I become very familiar with the airplane-so that is what I have been doing.

    Landing with 1/2 flaps is OK, but I miss the steeper approach angle that I got used to with full flaps on the SLSA. I did try some mock landings at altitude with full flaps in my own SS7, but the nose down pitch is so great that it is impossible to trim for a 60 mph approach speed and you come in with a lot of back stick pressure.

    Short of taking my center console apart and cutting another flap detent notch between the 1/2 and full flap positions (which some guys are doing), what else can I do to get the steeper approach angle for short fields? What other wisdom or suggestions are out there? Are there any dangers in just using full flaps and holding the back pressure to carefully hold approach speed?

    I would highly recommend that those of you still in the building process cut that extra notch before you rivet on the flap detent bracket.

    Jim

  2. #2
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    Default Re: Full Flap Use

    Learn how to slip your airplane. An aggressive slip will bring you down at over 1000 fpm on a steep angle, with the added benefit of better visibility to see those tree tops you are dropping in over at the approach end of the runway. Do lots of practice at altitude to get a good feel for them before using them on final. They will feel awkward at first , but once you get comfortable with them, I suspect you will use them all the time. Slips are a great tool to be proficient at for the safe Kitfox pilot. Go out and have fun. Bruce

  3. #3
    Senior Member Dave S's Avatar
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    Default Re: Full Flap Use

    Jim,

    The advice to use slips for step descents is right on.

    I found that the additional stall speed reduction from 1/2 to full flaps on our S7 was inconsequential....little more than 1 mph while 1/2 flaps from retracted flaps gives a 5 MPH stall speed reduction so the full flap setting gives a little, but not much advantage.

    IMHO - Flaperons extended as flaps reduce stall speed; but, do not add drag like the barn doors on a cessna do.......that's what slips are for and a kitfox performs slips like no other plane I have flown....just have to practice.

    While I do landings and takeoffs retracted, half & full, I find myself primarily using half flaps most of the time for most operations. For landing, I will use full flaps if there is little wind and no gust conditions.

    My experience has been that full flaps and somewhat variable/changing winds require a lot of attention to fairly obvious amounts of adverse yaw when jockying the alierons to compensate for the winds while half flaps not anywhere near so.

    Cheers,

    Dave S
    KF7 trigear
    Last edited by Dave S; 11-13-2013 at 07:37 PM.

  4. #4
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    Default Re: Full Flap Use

    If you don't use full flaperons, don't start. If you do, you might want to
    think twice about it. This is why:

    I can't say it will EVER happen to anybody else, but I had what I am sure was
    a tailplane stall with my Series 5 at altitude when playing with full flaperons
    (22 degrees) and did a tail over nose forward tumble ... I'm sure there are
    skeptics who might think it didn't happen, or say I imagined it ... In any case
    it DID happen to me and I'm lucky to be typing this.

    I'll never know exactly what caused it, but I know exactly what it did when
    it happened and I'm not going to go try to reproduce it ever.

    N85AE now has a mechanical block that prohibits any more than 11 degrees of
    flaperons. Going tail over nose on short final would be a very bad situation. I
    don't even want to experience it at altitude again.

    The plane flies like total crap with full flaperons anyway, and the roll control
    is really screwed up so I can't see any good reason to use them. The 11
    degree position is fine, and I use it regularly.

    I would seriously suggest NOT using 22 degrees, and learn to slip. It will sink
    like a brick with a forward slip.

    Regards,
    Jeff Hays
    N85AE, Series 5, IO-240B

  5. #5
    Senior Member Slyfox's Avatar
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    Default Re: Full Flap Use

    the kitfox has flaps. hmmmm.

  6. #6
    Senior Member Dave S's Avatar
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    Default Re: Full Flap Use

    Jim,

    One point I forgot to mention is that our plane is set up with the trim assist kit that John sells for the plane......that helped considerable with trimming the back pressure off on approach with flaps. In my opinion, the trim assist kit is a great addittion.

    Another point for all of us to keep in mind is that each builder's kitfox is not going to be identical - heavier or lighter engines, swept wing or not, more or less power. Some with the battery in the tail.

    Our plane has the manual trim tabs on the elevator while others have the electric trim on the horizontal stabilizer.

    All of the potential variables may or may not have an effect on handling characteristics and that is what we figure out in steps while doing phase 1 testing for our individual airplanes.

    Sincerely,

    Dave S
    KF7 trigear
    912ULS Warp Drive

  7. #7
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    Default Re: Full Flap Use

    I too vote for slips. I didn't use any flaps the first two years i flew my kf 4. I relied solely on slips to lose altitude steeply. Might of had something to do with the fact that I learned to fly in a Champ and it doesn't have any flaps. I just recently starting using about 1/4 flaps to smooth out my landings. i slip with a Little flap on too. it drops like an express elevator. Lot of fun.

  8. #8
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    Default Re: Full Flap Use

    I too had the spring assist kit, however I'm not a fan of it either, so I
    removed it as well. The reason why is that the pressure you are removing
    from the stick is telling you something (i.e. that there's a load on the tail)
    with the variable incidence tail (which mine has) it is a much better idea
    to just hold that pressure and "trim it out". this gets the tail flying where
    it wants wants to be. If you have elevator deflection to the point where
    you feel a significant pressure on the stick, that's telling you that the tail
    is not a long ways away from stalling. You really should NOT be using
    your arm plus a spring.

    My tailplane stall occurred shortly after I installed the spring assist kit,
    and I was flying the plane pretty aggressively at altitude (8000 ft. AGL)
    my guess is that some combination of the amount of elevator deflection
    I was holding (assisted by the spring) to overcome the 22 degrees of
    flaperon and probably a momentary airflow disruption over the tail caused
    it to stall thus creating the a$$ over tea kettle phenomenon to occur.

    Regards,
    Jeff Hays

    Quote Originally Posted by Dave S View Post
    Jim,

    One point I forgot to mention is that our plane is set up with the trim assist kit that John sells for the plane......that helped considerable with trimming the back pressure off on approach with flaps. In my opinion, the trim assist kit is a great addittion.

    Another point for all of us to keep in mind is that each builder's kitfox is not going to be identical - heavier or lighter engines, swept wing or not, more or less power. Some with the battery in the tail.

    Our plane has the manual trim tabs on the elevator while others have the electric trim on the horizontal stabilizer.

    All of the potential variables may or may not have an effect on handling characteristics and that is what we figure out in steps while doing phase 1 testing for our individual airplanes.

    Sincerely,

    Dave S
    KF7 trigear
    912ULS Warp Drive

  9. #9
    Senior Member jiott's Avatar
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    Default Re: Full Flap Use

    I appreciate all the good comments. I do have the spring assist kit. I also have learned to forward slip and agree it is a great way to lose altitude fast and do use it quite a lot. However, a slip is not a stabilized approach and I was just hoping for a steeper stabilized approach if possible. The full flap position just seemed to be perfect on the factory SLSA. If the full flap position on the kit version is so unuseable, as most of you seem to be saying, I wonder why it is even available on the kit. There must be some benefit to it somewhere. I would like to hear from someone who does use it and when and why. Maybe John M would weigh in on this?

    The ass over teakettle story really has me spooked from even experimenting with it.

  10. #10
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    Default Re: Full Flap Use

    I've never heard of it happening to anybody else, so I think I'm the lucky one.
    I talked to John at Kitfox, and he claimed to have tried to replicate it with no luck. Mine is nose heavy with the IO-240B so with 22 degrees, and the elevator
    deflection I had in with the trim assist, etc. I think there was a heavy downforce
    load on the tail and some burble made it pop. It might be impossible in a 912
    version of the plane with the lighter nose.

    I use slips all the time, the plane just loves to slip. I always fly a high approach
    to be safe, and drop it in with forward slip. Just relax pressure and it straightens
    right out.

    Regards,
    Jeff

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