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Thread: Leading edge slats and Keller Flaps

  1. #41
    Steve Pierce's Avatar
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    Quote Originally Posted by skywagon8a View Post
    How many of those have been installed due to the actual performance improvements having been proven to the owners? OR have they been installed just because "every one installs them" and/or "I spent the money, so of course they are an improvement"?

    Many alterations are done "just because". I'm not saying the slats do nothing, because they do. But are they needed in all applications?
    The guys I know with them are really using them. Not saying everyone that installs them uses them to the extreme, kinda like Bushwheels. Like Bushwheels there is a certain safety factor to me having flown Super Cubs before and after the install.
    Steve Pierce

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  2. #42

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    As I understand it… the slats not only produce lift - they ALSO create a venturi effect that directs higher velocity air over the top of the wing than would normally be there.
    They do this by taking a wide “bite” of the air on the lower leading edge and forcing it through a smaller exit on top of the wing. This higher velocity air creates more lift on the wing for that speed, AND more aileron/ flap effectiveness. Especially if you put VGs directly behind the slat to organize and stabilize the flow.
    So - its not about the slat creating another wing that holds the airplane up by its PK screws, its more like an airflow enhancement.
    The screws just have to hold the load created by the extra drag of the slat.

    One thing to remember - when this higher (than normal) velocity air flows over the front of the wing it changes the center of lift forward. And then you get higher aoa.
    This is why the Pstol flaps compliment the slats so well. They move the center of lift back, and balance the wing again.
    This is also why you can put larger flaps on a slatted wing.
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  3. #43
    wireweinie's Avatar
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    Not trying to be a male appendage here, but are you guys talking about 'slots' or 'slats' on the wings? The way I ways taught was a 'slot' was a fixed gap at the leading edge of the wing. A 'slatted' wing had an entire section of the leading edge that would deploy forward to actually change the shape and size of the wing. Legit question here.

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    Last edited by wireweinie; 06-24-2022 at 04:04 PM. Reason: bad engrish
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  4. #44
    skywagon8a's Avatar
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    The slot is the gap between the slat and the wing leading edge as in this discussion. On the Cub flap system there is also a slot between the wing trailing edge and the leading edge of the flap.
    N1PA
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  5. #45

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    I was referring to a pivoting fixed slat that has a fixed amount of travel so that at its farthest point away from the wing the exit area is roughly 1/3 or less the size of the inlet area. This creates a “slot”, that redirects and speeds up the airflow over the wing.

    As far as full length slats go … I do not have a cub, and my slats are fully retractable like a helio, and full length of the wing. Full stall is just increased sink rate, no wing drop, no roll over. At least not on my wing.

    Full stall at 1,800# is 28mph on GPS, and straight forward.
    Last edited by bda; 06-24-2022 at 05:17 PM.
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  6. #46
    stewartb's Avatar
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    How many of those have been installed due to the actual performance improvements having been proven to the owners? OR have they been installed just because "every one installs them" and/or "I spent the money, so of course they are an improvement"?
    Maybe the worst mis-information post I’ve ever read. Mackey slats improve the wing, no question. Keller flaps lower the useful AOA, no question. If an average pilot flies a plane equipped with both? He’s far better in slow flight/takeoff/landing than he would be in a stock Supercub. Are some slat pilots better than others? Absolutely. That’s not the topic. An average pilot can come and go more safely at significantly slower speeds than he could in a stock airplane. Stalls? On short final you can stand on a rudder and skid around a corner. No stall. Anyone who says Mackey slats aren’t a safety improvement hasn't flown them. Add Keller flaps? They flatten out the crazy high AOA potential. To say guys might not work slats is a farse. If they’re installed? The wing is improved. You can’t fly the plane without that benefit.

    Are they perfect for everyone? probably not. Certified guys don’t have the option. And that’s a shame.
    Last edited by stewartb; 06-24-2022 at 11:56 PM.
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  7. #47
    BC12D-4-85's Avatar
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    The edited change from originally "stupidist post" to "mis-information post" informs. Stewart please tame your typing. We don't need that behavior among fellow pilots.

    Gary
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  8. #48
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    Gary,
    We had two Helio's at Valhalla Lodge one on wheels and one on floats. They are fantastic airplanes, however because the slats are spring loaded so controlled by your forward speed, they work perfectly in the three point position. However on floats that is NOT the case, by the time you are on the step your deck angle is so flat to be in the slippery spot on the floats, you have sorta hung yourself as the slats have retracted into the leading edge
    So you basically have a 2300lb; 295 hp Tcraft (similar wing profile) With big flaps.......... So it's still about same as a good 206 on 3430's........ The exception to this is in 'bigger waves' and lite, because of the "ramping effect" of the wave T/O could be done while riding up the front side of a wave while the slats were still fully extended. Showing the true potential
    of the wing working correctly. While speaking with Dennis Branham (old time Helio family in Alaska) about this problem; with slats on floats, he told me, they had explored the possibility of a rear strut that could be shortened for T/O and extended for climb and cruise. But could never figure out how to do that. LoL
    I have some old movies of Helio T/O from 80's in Nushagak River using the waves as ramps and you could
    Get off in 100/150' as you went out thru the top of the wave because of the high AOA you had and slats doing their job! Of course the slats work the same for landing on
    floats as on wheels; So that's not an issue. But most folks that have not flown them; have no idea, how increadably soon, you can start a STEEP turn in a Helio, to avoid an obstacle, You can be in a very short spot, with tall trees at end, or steep rising terrain, and if there is a gap either side to escape; the Helio can turn very steep safely, where other wings can NOT. Hope this helps
    with the floatplane question.
    And when Pete says he beat Bob Bryant in the Helio, he forgot to mention he also beat the " hottest Cub" in Maine
    As well !!!! Moral of the story: Don't mess with Pete in a "Twin Bee"!!!
    E
    Last edited by TurboBeaver; 06-25-2022 at 07:25 AM.
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  9. #49
    Steve Pierce's Avatar
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    Quote Originally Posted by stewartb View Post
    Maybe the worst mis-information post I’ve ever read. Mackey slats improve the wing, no question. Keller flaps lower the useful AOA, no question. If an average pilot flies a plane equipped with both? He’s far better in slow flight/takeoff/landing than he would be in a stock Supercub. Are some slat pilots better than others? Absolutely. That’s not the topic. An average pilot can come and go more safely at significantly slower speeds than he could in a stock airplane. Stalls? On short final you can stand on a rudder and skid around a corner. No stall. Anyone who says Mackey slats aren’t a safety improvement hasn't flown them. Add Keller flaps? They flatten out the crazy high AOA potential. To say guys might not work slats is a farse. If they’re installed? The wing is improved. You can’t fly the plane without that benefit.

    Are they perfect for everyone? probably not. Certified guys don’t have the option. And that’s a shame.
    Really Stewart? You can't find a better way to say what you said? Pete didn't say they didn't work but that is besides the point. Good information but the delivery sucks.
    Steve Pierce

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  10. #50
    flagold's Avatar
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    Quote Originally Posted by stewartb View Post
    Maybe the worst mis-information post I’ve ever read. Mackey slats improve the wing, no question. Keller flaps lower the useful AOA, no question. If an average pilot flies a plane equipped with both? He’s far better in slow flight/takeoff/landing than he would be in a stock Supercub. Are some slat pilots better than others? Absolutely. That’s not the topic. An average pilot can come and go more safely at significantly slower speeds than he could in a stock airplane. Stalls? On short final you can stand on a rudder and skid around a corner. No stall. Anyone who says Mackey slats aren’t a safety improvement hasn't flown them. Add Keller flaps? They flatten out the crazy high AOA potential. To say guys might not work slats is a farse. If they’re installed? The wing is improved. You can’t fly the plane without that benefit.

    Are they perfect for everyone? probably not. Certified guys don’t have the option. And that’s a shame.
    Anyone who ever witnessed the famous (in France) test pilot of the 60's & 70's jump off in virtually zero feet, climb and immediately flutter down to virtually the same spot for a landing in a 150 hp (underpowered) SOCATA Rallye understands the value of slats and flaps in unison. He was absolute master of it.

    Previous posts about adding to the effectiveness of the wing are also correct. You have added to the surface area - you have more lift.

    Wing slats on a Rallye 235C:

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    Slats on a Helio

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    In both cases - take away the slats irregardless of the leading edge shape and you have decreased the area of your wing. Install slats and you increase the wing area of your wing. Nothing for you guys to get in a big flap about - it is as simple as that.

    Safe flying.
    Last edited by flagold; 06-26-2022 at 09:38 AM. Reason: Rallye 235C not G - Dang Cateracts will have both removed in 2 weeks . . .
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  11. #51
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    I'd explore adding mechanizing to the Helio slats but only for floats. Easily said likely hard to do. The early Helios had an overhead hand crank to deploy the flaps. Maybe incorporate a similar method (or electrical or added spring loading?) to positively deploy the slats (some or all of the four units?) when desired (as noted by Turbo above to prevent their premature retraction). Then, if needed retract/disable the positive slat extension mechanism and let them float in position as originally intended. Having ridden in them but never flown, it was explained to me by Hap Hanlon the pilot/owner that they did well when slow but at some point they need to retract to reduce drag to allow climb and cruise. Nose down and increased speed does that. So maybe that's why their float use is limited for some.

    Gary
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  12. #52

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    I got to fly in the Monster cub last week and it is a Beast!! Thanks LITECUB!! The slats let you get super slow and still be stable. Even with big flaps the AOA on landing is very high so you have to pick your touchdown spot early and note something off to the side for reference. Not really much different then getting a Pacer real slow. The big advantage of the slats is how slow you can go and still be stable! Hitting you spot is harder but can be done. I am normally not a fan of the shocked tail spring but with the extended fuselage and high AOA it works well to protect the tail. I have a set of slats for the new project but I am looking for a fast cub so will nut plate the leading edge and add if needed. What we really need is a retractable slat for the cub. Why not a simple Hadley Page style, 1/8 thick that just lays on top the leading edge Put the hinge above the slat with a cover. Now we would have fluke bumps and a retractable slat. https://blog.gridpro.com/a-whale-of-...n-wing-design/ https://www.eaa.org/airventure/eaa-a...91-years-young Lots of smoke today so just being a keyboard pilot. DENNY
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  13. #53
    BC12D-4-85's Avatar
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    A local experimental PA-18 has fixed LE slots with extended stock form flaps - Dakota Cub style. After watching that plane on conventional gear and others here with slats and big flaps, if on floats so far (based solely upon Post #4 I'd choose the former fixed configuration. I'm hoping someone with slats will float their plane and then we can learn more about their behavior or benefit in that mode.

    Gary
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  14. #54
    skywagon8a's Avatar
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    Quote Originally Posted by DENNY View Post
    Now we would have fluke bumps and a retractable slat. https://blog.gridpro.com/a-whale-of-...n-wing-design/ DENNY
    I saw an airplane with leading edge bumps as described in your link. I seem to remember it being at Birchwood or perhaps Merrill? It was orange in color, never saw it fly.
    N1PA

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    BC12D-4-85's Avatar
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    It was at Birchwood. Parked in front of my IA's hanger the owner had a PHD in aeronautical engineering if I remember his degree correctly. He had also built a plane that looked like a flying squirrel. I think it is still in a local garage somewhere around here. DENNY
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  17. #57
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    Seen at Afton today, I may have posted on this some time ago (?) but still pretty cool. No slats BTW.

    Only 100 yards across the highway, is a huge farm supply biz that sells EVERYTHING, and opens at 9 on a Sunday. I flew the 65 miles from my place to get some 18 G wire terminal ends, and breakfast of course, rather than drive the 15 miles into Pocatello on a weekend, makes sense to me.
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  18. #58
    skywagon8a's Avatar
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    Quote Originally Posted by courierguy View Post
    Seen at Afton today, I may have posted on this some time ago (?) but still pretty cool. No slats BTW.

    Only 100 yards across the highway, is a huge farm supply biz that sells EVERYTHING, and opens at 9 on a Sunday. I flew the 65 miles from my place to get some 18 G wire terminal ends, and breakfast of course, rather than drive the 15 miles into Pocatello on a weekend, makes sense to me.
    Make sense to me too.

    New experimental model A1c-200. https://registry.faa.gov/AircraftInq...umberTxt=806wt
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  19. #59
    Steve Pierce's Avatar
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    Airframes accidently sent me drawings and the P-STOL flap hangars for the Husky instead of Aviat. I was sworn to secrecy.
    Steve Pierce

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  20. #60
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    This is the Norden, by Zlin, a LSA type with a Rotax, electric retractable slats.
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  21. #61
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    Wonder if the hinges will bolt on like a cub kit. I saw airframes came out with husky aluminum struts


    This one has slats..

    https://aviataircraft.com/wp-content...heet_n55wy.pdf

  22. #62
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    Quote Originally Posted by RaisedByWolves View Post
    Wonder if the hinges will bolt on like a cub kit. I saw airframes came out with husky aluminum struts


    This one has slats..

    https://aviataircraft.com/wp-content...heet_n55wy.pdf
    Took some pictures of it at the Texas STOL Round-up at Hondo, TX several years ago. https://photos.app.goo.gl/vd2ivV8Q9Crw2xKD8
    Steve Pierce

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  23. #63
    flagold's Avatar
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    Quote Originally Posted by Steve Pierce View Post
    Took some pictures of it at the Texas STOL Round-up at Hondo, TX several years ago. https://photos.app.goo.gl/vd2ivV8Q9Crw2xKD8
    Those are automatic?

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