Sportsman STOL Kit Features for Homebuilt Wings

The dominant cause for fatalities in kit planes I've reviewed, is low & slow while: making turns, abrupt control movements, high engine power, wind gusting or wind drop-out near stall speed.

http://www.ntsb.gov/investigations/accidentreports/pages/aviation.aspx

For conventional gear / tail draggers, the center of gravity is behind the landing wheels, contributing to a tendency to want to ground loop.


The Sportsman STOL Kit will not allow a stall, just about in any attitude and power setting. Also in some PiReps there are reports of a more stable landing after touchdown due to the Sportsman STOL Kit and increased control surface authority.

Created a related Group:
https://www.homebuiltairplanes.com/forums/group.php?groupid=39


I did not originally build my Kitfox.

By what procedures am I required to follow, to make untested changes to my aircraft?

and

Does anyone have experience with a Sportsman STOL Kit in a certified aircraft, or better, in a HBA?

 

From their web site, it seems that the Sportsman STOL Kit is (another) leading edge cuff that modifies the airfoil of Cessna aircraft. To incorporate that on a homebuilt, just build a wing that either has the same modified airfoil, or select another airfoil with the same characteristics.

If HBA STOL is of interest to you, look into Just Aircraft's Super STOL.

FWIW, I had a Cessna A152, which is heavier than a standard C152. A chapter member had a C152 with a STOL kit (don't remember which one, but it used cuffs as well as vortex generators) that performed no better than the heavier A152.

Fatal stall-spin accidents in airplanes, HBA or type certificated, STOL or otherwise, usually are due to poor judgement and or poor piloting skills.


BJC

 

I agree with everything you say about flying skills.

I'm looking for insights related to a non-builder making modifications to my kit built aircraft, that was purchased from someone else.

I modified my original post, because I did a poor job in making that readable. Thanks for both your insight about STOL and for helping me rephrase what I am looking for.

 

Your Operating Instructions have the instructions on modification. There are different versions; the newest is the least restrictive, so it might be good to have them updated by the FSDO if they are older. The test area if not the same as the Operating Instructions needs to be changed by the FSDO too.

 

The rest is getting out the tools and doing what you want.

 

It would help if we knew what type of airplane and possibly what airfoil it uses. Many airplanes designed for slow flying and landing use the same basic airfoil, so there may be someone who knows of an example that someone has experimented with before. Bob Barrows original version of the Bearhawk wing has a NACA airfoil with a modified leading edge incorporating a cusp for slow flight. Steve Wittman designed a movable leading edge that could be incorporated into your existing wing design. Wing fences, and other devices are easy to add.

View attachment Whitman leading edge.pdf

 

The Sportsman STOL leading edge cuff upgrade is almost unanimously accepted as the best of all the Cessna leading edge STOL cuff modifications. It was originally designed by a highly trained Lockheed aerodynamicist (Marvin Davis), and when he died the program was taken over and put into production by Marshall Quackenbush at California City. When Marshall passed away his son Alan Quackenbush sold the rights to Stene Aviation who now sells the kits.

An overwhelming percentage of Cessna owners swear by it, and this includes a large number of the people in Alaska who fly their C-180 and 185 airplanes all day / every day in the most demanding conditions anywhere. This modification is (again, almost universally) considered to add a great deal of safety, low-speed controllability, and a reduction in stall speed (or higher AoA).

If you have a Cessna type aircraft, adding the Sportsman STOL upgrade is virtually guaranteed to make you happy you have it when you are flying at the slow end of the envelope. But the Sportsman STOL does NOT increase the speed (you may even lose 1-2 mph).

However, as has been mentioned, no aircraft modification or safety feature has ever been shown to successfully combat stupidity.

And the biggest thing you have to realize is that it was designed for only one family of aircraft/airfoil. Increasing the camber of the wing, it will certainly affect (increase) the pitching moment, and influence a lot of other factors. There are a lot of folks here who can quantify that.

So the bottom line is that you cannot just install a leading edge cuff on any airplane (HBA or certified) without looking at whether the tail volume/area is still large enough, the wing torsional structure is stiff enough, etc. etc.

 

With some effort, people could be designing and building airplanes that don't have stall-spin tendencies. However, making planes that stall-spin has become normal for some reason. It is a bad design characteristic that has just become accepted and the burden placed on the pilot to stay away from the danger zone built into the airplane. I say the poor judgement comes in during the design phase of the airplane long before any pilot gets around to inputting any of their own poor judgement.

 

To be faired and balance, there where several cuff mods on the Cessna already when Davidson included his, which was very similar to the ones Cessna was providing on their wings after 1972is (don't have the details) . While I don't doubt some performance gains... and as I said before, people don't go out saying their purchase of the most expensive set of clubs did not improve their game, else why buy it. onder:

Anyhow, if you are really discussing performance gain ons Cessna, the RSTOL is a better (and much more accepted mod in ALASKA) than the Sportsman STOL kit. Here is what a very knowledgeable person said about the RSTOL vs the others...

I hope everyone enjoys their new set of golf clubs they got themselves for Christmas... I sure will!!! :gig:

Merry Christmas y'all