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Thread: Drooping Ailerons / Top Cub STOL

  1. #1

    Join Date
    Dec 2012
    North Pole AK
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    Drooping Ailerons / Top Cub STOL

    I recently had to remove the Top Cub STOL kit from my plane due to an inability to find replacement parts and other reasons that don't belong here. I have about 700 hours in my cub over about 3 years with the system and this is the first summer without the system so I thought that I would share my experience with the system. So far I have about 100 hours without the system. My cub also has the leading edge cuff and VGs.

    I love it and I miss it.

    First the bad
    Cross winds are a handful which everyone knows to be a weakness of the system, but let me elaborate. More specifically gusty crosswinds are hard to handle. I have maintained a high level of proficiency in the plane and I don't think I would have any more difficulty handling a strong crosswind with or without the system. Gusty crosswinds are much harder to correct for with the system since the roll rates are certainly reduced, but I simply carried more speed or used less flap in the past during these situations, which I'm certain results in landing a little longer than a stock cub. Take away the gust and it outperforms a stock cub on landing and takeoff.

    I have found that "popping" the flaps at the right point on the takeoff roll reduces my takeoff distance considerably, especially at higher weights. I begin the takeoff roll with full forward stick and trim and no flaps and then at a point that I have learned in my plane I pull full flaps. With the drooping system this point is much more critical. If you pull too early it greatly increases the takeoff roll due to the increase in drag.

    Climbout performance is greatly reduced. The climb angle of any airplane is a pure function of excess thrust. With the droop you have more drag; therefore, less excess thrust and your climb angle suffers. I have attempted to mitigate this by retracting flaps in ground effect when possible.

    With full droop and near approach speeds in turbulent air it can require top rudder to level the wings while maneuvering to final. This is very disconcerting but is mitigated by either maintaining excess speed until established on a final or delaying pulling full flap/droop until on final.

    Now the Good

    3-5 mph on final. Yes the system seemed to let me fly about 3-5 mph slower on final.

    Lower deck angle for the same speeds. In general, trailing edge devices lower the deck angle of a plane while leading edge devices increase the deck angle for a given speed. My visibility over the nose was much much better with the drooping ailerons all while flying several mph slower. This may be what I miss the most.

    At max gross on a hot day my takeoff distances seem to have increased about 10% regardless of technique. Every year I have "validated" my takeoff data in the spring. I go to the same strip, load the same stuff and mark the runway. I bring observers to record the data and with one flight test completed so far this was the result, but it is too early to say 10% as a valid figure.

    My Conclusion:
    If you learn the system and stay proficient it will give you more performance out of your cub under most conditions. The best solution would be a selectable droop. I've heard that one exists for experimental cubs??? I'm planning a kit plane at some point and I'd be interested in installing a system that would let me select aileron droop on/off.

  2. #2
    Steve Pierce's Avatar
    Join Date
    Mar 2002
    Graham, TX
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    I believe that Jerry Burr has a drooping aileron system in his Cub that can be disconnected if you just want the flaps only for reasons you have posted. I wonder the difficulty of certifying the system in that configuration?
    Steve Pierce

    Everybody is ignorant, only on different subjects.
    Will Rogers

  3. #3

    Join Date
    Sep 2003
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    You guys should visit the J-3 Cub forum. All they do is add VGs and get a 15 mph reduction in landing speed.

    We had a bit of trouble with aileron effectiveness with the cuffed wing, but I understand VGs might have corrected that. I have not flown a Cub with drooped ailerons, but the Robertson 185 was great fun! I got to take the factory course. I would do that again in a heartbeat.

  4. #4
    Gordon Misch's Avatar
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    Dec 2003
    Toledo, Wa (KTDO)
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    get a 15 mph reduction in landing speed
    15 indicated, right? In my 12 at those low speeds a difference of 10 indicated is only a couple by GPS. For that reason I don't think the lift coefficient is going up very much with the increased AOA, I think that a major effect of the VG's (and in my case the cuff also) is high AOA tolerance. Just thinking out loud here; don't really know - -

    And how high off the ground are the mains when the tailwheel touches?!!

    N4328M KTDO
    My SPOT: (case sensitive)

  5. #5

    Join Date
    Sep 2003
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    It's not me - I sense very little change when VGs are added. It is others - and they are saying their GPS backs it all up. If it were true, I would be able to cut my takeoff and landing distances in half, assuming I am not saying "momentum" while jumping on the brakes.

    My Cub lands at around 38 mph. Fifteen off of that is 23. I would kill for that speed on short final. My thousand bucks would be on its way to Micro as we speak.

  6. #6
    Bill Rusk's Avatar
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    Jan 2003
    Sandpoint, Idaho
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    Second post and an excellent one at that. Thank you for taking the time to make that well written assesment. DW on the site here had a selectable droop system. He has since gone to the Keller flaps and removed the droop system. I believe he is working on a LE cuff now.

    Best regards

    Very Blessed. "It's not an obsession, it's a passion"

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