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Daydreaming About Flaps

............Also, words have meanings. A split flap is different than a slotted or double slotted flap.

That's exactly what I was thinking as I was reading down this thread.
As I understand it, a "split flap" is like what the Cessna Airmaster has.
I would call the Performance flaps a double-slotted or "compound" flap.
Semantics, I know, but it really helps everyone understand things if we all use the same (correct) verbiage.
 
I'm always impressed by the energy and ingenuity of the people on this site. Always trying to build a better mouse trap - and sometimes doing it, like Keller flaps. Just the same, I gotta hand it to those "engineer types" at Piper way back when. 70 years later and we're still bustin' a gut trying to make near perfect even better. :)
 
I can tell you that the force to actuate the Keller flaps is huge compared to my old stock flaps. This is on a one-off Cub/Cruiser hybrid that I built. The Airframes Alaska supplied manual says to not deploy full flaps over 70MPH. I decided to not deploy any flaps above 65. I have three detents in the flap ratchet pawl. The last detent will extend the flaps to the maximum angle. The position of my flap handle is not ideal and it requires that to get full deployment the handle ends up behind the pilot. The force required to get the last notch makes it almost impossible to get. I even tried slowing the airplane to 45 and the force is still extremely high.

Since my airplane is experimental, The didn't supply the doublers required by the STC. I was and still concerned that this should be a necessity on all kits. There is a huge load on the flap hangers with these flaps.

Testing that I did with the second notch did produce significantly lower stall speed and deck angle. The manual states max deployment angle of 50 degrees on the second section. With the second notch I get 30 degrees and that is where I did my testing.

BTW: Bill Rusk is right about what I call a point of diminishing returns when you install slat and slotted flaps. Consider where each is designed to work. The flaps are designed to work at lower angles, whereas the slats work at higher angles.


There is definitely a higher force to pull full flaps with the Keller flaps with the shortened flap handle and It's difficult to get the leverage for the final notch. I had Dan Byker, Byker Aviation, Hawarden Iowa, fabricate a grip to fit over the flap handle - works great!

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Did you have the shortened handle with the stock Piper flaps?

No the shortened flap handle is only STC'd with the Keller flaps. There is no STC for the shortened flap handle with the stock flaps - if you want to keep to the rule book :lol:
 
I'm always impressed by the energy and ingenuity of the people on this site. Always trying to build a better mouse trap - and sometimes doing it, like Keller flaps. Just the same, I gotta hand it to those "engineer types" at Piper way back when. 70 years later and we're still bustin' a gut trying to make near perfect even better. :)

those guys before and during ww11, got my utmost respect. the first one mustve taught a lot of lessons. mind boggling the inside of a radial engine.
 
I was just trying to determine if you had an increase in flap handle force to deploy the Performance STOL (Keller Flaps) vs the stock flaps. I have not noticed a significant difference between the two as far as force to pull the handle. I have not shortened any of the handles on the airplanes I have installed the flaps on. Some may have been shortened previously.
 
I was just trying to determine if you had an increase in flap handle force to deploy the Performance STOL (Keller Flaps) vs the stock flaps. I have not noticed a significant difference between the two as far as force to pull the handle. I have not shortened any of the handles on the airplanes I have installed the flaps on. Some may have been shortened previously.


The shortened handle is much better in a left crosswind for sure, but it is just more awkward to get that last notch in as you pull back to the seat. With the grip on the flap handle you can use the palm of your hand to push the flap button not your thumb. I think with the shortened handle there is definitely more force than the stock handle. It was difficult to get the last notch in above 50 MPH before I put the grip on the handle. Now 60 is no problem - 62 is too fast for them and no real reason to even pull them at 60 but it's nice to be able to. They are placarded not to pull above 70 - you would need a pretty big set of "guns" to pull it at 70 anyway.
 
Hmm, I guess I am just use to the short handle or I wonder if some airplanes take more force. I have been deploying the first notch at 70 and then as I slow down another notch and then the last. I will have to look at the speeds at which I pull each notch.
 
What is the actual white arch/flap operating speed in an -18? For some reason I haven’t paid much attention to the others I’ve flown and mine lacks a little in the placard department
 
Models PA-18S and PA-19S, 2 PCSM (Normal Category only), Approved May 9, 1950:
Model PA-18S "125", 2 PCSM (Normal Category only) Approved October 25, 1950:
Model PA-18S "135", 2 PCSM (Normal Category only), Approved May 15, 1952:
Model PA-18AS "125", 2 PCSM (Normal Category only), Approved July 1, 1953:
Model PA-18AS "135", 2 PCSM (Normal Category only), Approved July 1, 1953:
PA-18S "105" (Special), same as PA-18S with the exceptions as listed in NOTE 3.

Flaps extended (with Item 601) 80 mph

Model PA-18 "150", 2 PCLM (Normal and Utility Categories), Approved October 1, 1954; Model PA-18A "150", 2 PCLM (Normal and Utility Categories), Approved October 1, 1954.

Flaps extended 85 mph

Models PA-18S and PA-19S, 2 PCSM (Normal Category only), Approved May 9, 1950:
Model PA-18S "125", 2 PCSM (Normal Category only) Approved October 25, 1950:
Model PA-18S "135", 2 PCSM (Normal Category only), Approved May 15, 1952:
Model PA-18AS "125", 2 PCSM (Normal Category only), Approved July 1, 1953:
Model PA-18AS "135", 2 PCSM (Normal Category only), Approved July 1, 1953:
PA-18S "105" (Special), same as PA-18S with the exceptions as listed in NOTE 3.
Flaps extended (with Item 601) 80 mphModel PA-18 "150", 2 PCLM (Normal and Utility Categories), Approved October 1, 1954;
Model PA-18A "150", 2 PCLM (Normal and Utility Categories), Approved October 1, 1954.
Flaps extended 85 mph Model PA-18S "150" and PA-18AS "150", 2 PCSM (Normal Category only), Approved
October 1, 1954.

Flaps extended (with Item 601) 80 mph
 
Hmm, I guess I am just use to the short handle or I wonder if some airplanes take more force. I have been deploying the first notch at 70 and then as I slow down another notch and then the last. I will have to look at the speeds at which I pull each notch.

I would say that the first notch is no different from short handle to long handle in force required to pull. It's that last notch that's the problem with the short handle.



White arc for standard is 85 MPH

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I think the increased pull force with the Keller flaps and short handle is a good thing. It reminds me I need to be a bit slower.
 
I had to lengthen my flap handle because the loads were too high to easily release the 110" long flaps after take off.
 
I agree with you. My Cub has extended squared off wings with 110" long otherwise stock flaps and a smooth wing leading edge extended skin on floats. It routinely operates comfortably in and out of a 1000 foot long pond with 30 foot tall trees on each end. It can clear the trees on take off by the 2/3 mark. It would be able to operate in a no obstacle 600 foot pond. Why add weight and drag for the possibility of losing cruise speed? There are a couple of PA-12s here on wheels which have difficulty keeping up. It has demonstrated 28 mph on the gps with no wind before landing tail low in the water. Slats alone would only raise the nose more, landing water rudders first (not a good idea). It's the forward section of the floats which are stressed for landing loads.

View attachment 41624

Pete, when I see a post from you, I rarely don't read it because of all of your consistent well thought out remarks. But, I do think that
slats would allow you to safely slip at a much higher decent rate coming over the trees. This would allow you to touch down much sooner. Coming in over 60 foot trees, I can touch down in the same airplane 50 feet shorter. Slats allow you to do full rudder travel slips and lift the nose slightly. Decents of 2000 fpm are possible. If you do a full rudder slip, in a non slat equipped aircraft, and lift the nose, at a large decent rate, you may not only stall, but likely flip inverted.

There is nothing that says that if you have slats you have to hold that high angle of attack all the way to touchdown. Slats work great on a float plane, if you have obstacles to clear.

For take off, use the slats to get off sooner and then hold the plane a foot off the water and accelerate to a much higher speed, until close to the object, and then climb over it at a high angle of attack. This is much safer than dragging along at max angle of climb.

Thanks again for your comments Pete.

Jonny
 
Slats can cause drag. Hello pilots and the Flight Manual warn about increasing airspeed to stow them if that's an option to improve rate of climb. I've seen them do that as a passenger. Fixed slats?

Gary
 
Jonny, Thank you for the kind remarks. I don't doubt that slats will do everything you mentioned. I've flown several different types of planes with slats for many thousands of hours and do understand their advantages and disadvantages. For me, I would only want slats on my Cub if they could close up and blend in to the wing as they do on the Helio Courier. Cubs are notoriously slow in cruise and I don't like slow unless it is during landing. In my mind, if my Cub were to cruise as slow as 100 mph something is wrong. It will do 120 mph on floats at the expense of burning more fuel. I usually loaf around at 21.5"/2400 rpm and 105 -108 mph, 8 gph. 2000 feet per minute with slats in a slip is plenty for most tight spots as long as you can arrest that descent to make a decent landing. My clean wing Cub will slip at high rates of descent without danger or difficulty and still make a comfortable landing. I have no idea what the rate is as I'm not looking at any instruments during that phase of flight. I have found no tendency for it to depart controlled flight under those circumstances and I do fly it on the edge. It talks to me. I can feel when it is getting close to being a bad boy. It has never given me pause to wonder, WTF why did it do that? My Cub floats like a T-craft, so much so that I had to increase the flap angle to 56 degrees to get the desired descent angle. The pond in the picture is the smallest and most difficult pond around here in which I would want to land. It can be done without slipping and is easy with the prop angle set at an intermediate setting. If the pitch was set at a climb setting it would blast out of there like a cat with it's tail on fire and the braking action from the low pitch would also help it landing.

If you want to see how fast a B-727 comes down with full 40 degrees flaps, you should try slipping it. Works great if you find yourself too high and can be done without anyone else knowing that you are slipping.
 
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