Without the modifications experience, I still agree with Cannon, Kurt, and Hotrod 180 about time in the airplane, money for gas, and especially iterations. Use the time and gas to find the capability of whatever airplane and especially yourself. The just a bit heavier 180/182 verses 150/170/172, Comanche or Arrow verses Cherokee, Pawnee verses Cub, and such airplanes don't seem comfortable with faster than book low ground effect takeoff and slower than book power pitch approach at first, but their power to weight compared performance is similar. It takes time to get comfortable and time and gas is best spent getting a little better each time rather than just repetition.

if it’s within your budget (meaning no where did you say it’s either this upgrade or fuel) install it. I’ve never heard anyone say it’s crap remove it, then spend the fuel money flying the wing you will have not a wing you won’t.

I have no intention of ever installing it on mine.

Ive heard of guys regretting VG installs on their Cessnas as well as Husky’s. They work great some airplanes and not so great on others.

Kurt

G44 wrote:Ive heard of guys regretting VG installs on their Cessnas as well as Husky’s. They work great some airplanes and not so great on others.

Kurt

We have VG’s on a Sportsman equiped C180J with the O520. We did them separately, a long time ago. VG’s do as advertised. They do reduce the stall a few knots. They definitely improve the responsiveness of the control surfaces (Aileron, elevator and rudder) at slow speeds. They smooth out the bumps in turbulence (why, I don’t know). You would need Bush Wheels to get enough angle of attack to get any meaningful STOL advantage. I view them as a safety item. If I stuff up on a strip somewhere with a big load staggering of the end they will keep me flying a bit longer. They are not expensive. Apart from all that, they are a PITA.

Good evening all. I’m new to the forum and we are currently shopping for our first tail dragger, a Cessna180. Being new to both this particular airframe and the forum, I have a great many questions. I have been, obviously mistakenly, of the impression that the Robertson STOL, the Sportsman STOL and the Horton STOL were three different takes on the leading edge cuff. Following this thread however, it appears that some have installed the Sportman cuff on an airframe already equipped with the Robertson STOL. My previous understanding of these mods was obviously “well off-course”. I fully understand the benefits of modification to the leading edges of the wings, but please help this neophyte in the “tail-dragger-backcountry” world understand the true differences and how, for example, the Robertson STOL and the Sportsman cuff work together and in harmony to produce better STOL performance.

Thanks in advance and Happy Thanksgiving to all, yes even our Canadian friends. Hell, we’ve all got plenty to be thankful for.

Blue skies

BadBilly wrote:Good evening all. I’m new to the forum and we are currently shopping for our first tail dragger, a Cessna180. Being new to both this particular airframe and the forum, I have a great many questions. I have been, obviously mistakenly, of the impression that the Robertson STOL, the Sportsman STOL and the Horton STOL were three different takes on the leading edge cuff. Following this thread however, it appears that some have installed the Sportman cuff on an airframe already equipped with the Robertson STOL. My previous understanding of these mods was obviously “well off-course”. I fully understand the benefits of modification to the leading edges of the wings, but please help this neophyte in the “tail-dragger-backcountry” world understand the true differences and how, for example, the Robertson STOL and the Sportsman cuff work together and in harmony to produce better STOL performance.

Thanks in advance and Happy Thanksgiving to all, yes even our Canadian friends. Hell, we’ve all got plenty to be thankful for.

Blue skies

First, the Horton, Bush, Owl, and probably a few other "STOL Kits" were essentially just a re-contoured leading edge cuff, added to the wing to slightly change the camber of the wing, thus at least slightly improving low speed handling and at least slightly lowering stall speed. I know....a lot of "slightlys" in there, but frankly, the "improvements" afforded by those kits were pretty minimal. Some (but not all) of these kits also included a set of "stall fences" on the top of the wing, located at the aileron/flap juncture. The purpose of these was to slow or interrupt the progression of the stall across with wing as the stall propagated from wing root towards the tip, and to keep the ailerons effective as long as possible as you approach the stall.

Second, the goal of all of these modifications is to allow the airplane to fly at a higher angle of attack, therefore at a slower speed than a stock wing. Slower approach speeds MAY permit shorter landings, and maneuvering in tighter spaces.....please note the caveat there, however. May is a huge word in this context.

Robertson developed a system for older Cessna aircraft and some other brands (the Twin Comanche was also modified by Robertson) which took a different approach. Robertson STOL on early Cessnas also added a wing leading edge cuff, very similar to the Bush/Horton/etc cuffs, BUT in addition, the Robertson kit's primary function was a mechanism which droops the ailerons with flap extension. This, effectively, provides for full span flaps. The aileron droop isn't just a simple droop system: When flaps are selected to 10 degrees, the ailerons droop a few degrees, something like three degrees (sorry, been a few years and I don't recall the exact deflections, but the important thing is the relative amounts of droop). Then, at 20 degrees of flap, ailerons droop a bit more, like five degrees. At 30 flaps, the ailerons reach their maximum droop, I think 7 degrees, and finally, at full (40 degrees) flaps, the ailerons actually retract slightly, back to say, five degrees. Again, unless you're rigging them, the exact number of degrees of droop isn't that important, but the ratios are. Robertson also included stall fences on the top of the wings on most kits.

The Robertson kit on the Cessna 185, for example, was actually flight tested and DOCUMENTED to reduce stall speed from ~ 54 knots to 37 knots.....which is an amazing, and easily demonstrable difference.

The downsides: The Robertson kit is fairly complex and requires some significant rigging to get it right. It also adds some weight, which is not insignificant, since there's the weight of the cuff, the additional pulleys, brackets, etc, AND a substantial addition of lead balance weights to the balanced ailerons.....like a lot of weight there.

At some point, Cessna recognized that there were a lot of these "STOL" kits out there that were essentially just a leading edge cuff, that re-contoured their leading edge, and in the late 70s or so (someone will correct me, this is a ball park), Cessna introduced their "Camber Lift Wing". Essentially, that wing simply changed the shape of the basic Cessna wing to duplicate (or close anyway) the shape of the older wing with one of these cuffs attached. The Camber Lift Wing leading edge was cambered, in other words, to improve slow speed handling and reduce stall speed. That said, look at the flight test documented stall speeds of the earlier wing airplanes vs the camber lift wing equipped airplanes and you'll find little difference there. Assume your own conclusions.

But, because Cessna had effectively duplicated a part of Robertson STOL's modification (the leading edge droop), Robertson simply dropped the addition of the cuff from their kits for the newer Cessnas.

At some point, a smart aerodynamics engineer who worked for Lockheed's "Skunk Works" program developed what has become the "Sportsman STOL" kit. The Sportsman kit is primarily a leading edge cuff, although the change in camber of that cuff is much more aggressive than the old Horton/Owl/Bush/etc cuffs. So, the Sportsman cuff actually increases the wing surface area noticeably, and the "drooped" leading edge is more prominent. Also, the Sportsman kit includes aileron gap seals, which help the ailerons remain effective will into the stall. This kit does not incorporate "stall fences" on the top of the wings.

Look at the wing leading edge on a Cirrus aircraft or a new Kodiak. Those airplanes are equipped with what is now called "MOLE" technology, which is essentially a "stepped" leading edge, with the outboard section of the wing leading edge (the section immediately forward of the ailerons) "stepped". If you look at the camber of those outboard sections, they're similar in shape and serve the same purpose as the Sportsman cuff. In other words, they delay the stall of that portion of the wings...the purpose in these airplanes isn't so much STOL performance overall as to keep that outboard section of the wing and the ailerons effective at slow speeds.

The Sportsman kit does significantly decrease stall speeds, and significantly improves slow speed handling. Frankly, I've never met an aircraft owner who installed a Sportsman kit on his or her plane that wasn't significantly impressed with the slow speed handling of the plane. Not so with the earlier, much less aggressive Owl/Horton/Bush/etc kits. Those kits undoubtedly do slightly improve slow speed control, but the effect is small enough as to be difficult to measure, frankly.

Now, add a Sportsman kit to a Robertson equipped airplane.....and you gain the advantages of both systems, including a significant decrease in stall speed, MUCH better control at slower speeds, etc.

In fact, one of the things that many pilots don't like about the RSTOL kits is that the drooping ailerons somewhat decrease aileron effectiveness with flaps deployed....like when you're landing/taking off. That's because the amount of aileron travel is restricted because of the droop.

This is a minor issue in most situations, but can be limiting in a gusty crosswind, for example, when taking off. There are ways to operationally mitigate this effect, but not to eliminate it, with a standard RSTOL kit. In fact, next time you hear someone talk about doing that, ask them if they've ever flown a deHavilland Beaver or Otter.....both of which droop their ailerons with flap deflection, in a manner similar to the Robertson aircraft.

BUT, add the Sportsman kit to an RSTOL equipped airplane, and those aileron gap seals give you back quite a bit of the aileron effectiveness that was lost with the RSTOL kit. Not all, but a good bit.

In fact, I know of some operators of Cessnas who've removed or disabled the aileron droop on their RSTOL kits because they don't like the reduction in aileron effectiveness.....Personally, I'd never do that. First, I'd add a Sportsman kit, and see if that met my needs.

I have a few thousand hours working Cessna airplanes with RSTOL kits, and I love them, frankly. I'd take one of those airplanes over a stock wing airplane ANY day for work or play. And, yes, I've spent a few nights sleeping in my RSTOL Cessna after I landed somewhere and either the wind picked up or I realized I'd screwed up, and takeoff with a load wasn't going to be safe in gusty winds. Sorry, but that's a small price to pay for the capabilities of these kits.

That's my opinion, and we all know about those. Others can add to, refine or argue with what I've posted here, and they may be right.

MTV

Another pet peeve: Pilots who modify their aircraft, then tell you that their VGs/Cuff, or whatever "reduced the stall speed by 7mph".

Why you say? Understanding how your pitot system works should tell you the answer. A "STOL kit" generally does influence the Angle of Attack at which the wing stalls. That change also changes the direction that the relative wind strikes the pitot tube. The pitot tube is optimally located to offer the best accuracy over its range, but when the relative wind arrives from a different angle, the airspeed instrument may or may not be reading airspeed accurately.

In fact, I've told Cub owners, only somewhat jokingly, that I can make their plane land at a variety of speeds by just bending that little tube on the left wing.

Now, you can try to "calibrate" the pitot tube to try to compensate for a modification, but then you'll likely lose accuracy somewhere else in the speed range. Frankly, as has been pointed out many times on this forum and elsewhere, the pitot system in these small airplanes isn't very accurate. Which is why I never look at the airspeed instrument when I'm landing.....it's not reliable or accurate at those speeds.

In fact, when I bought a Piper PA-11 several years ago, I glanced at the A/S instrument a few times while landing, and it read zero mph.....now that's a Hell of a STOL kit!

Robertson STOL, unlike any other manufacturer of these "STOL Kits" that I'm aware of, installed precision flight test pitot masts and instrumentation on their airplanes in flight test, and actually documented their airspeed changes. It's also the only STOL kit I've seen that comes with a requirement to re-mark the airspeed instrument, and a Flight Manual Supplement which spells out all airspeed differences with the kit installed.

So, when a guy or gal with a Cessna 185 with a Robertson STOL kit installed tells you that the stall speed of the airplane is 37 knots (as compared to 56 knots for a stock airplane), they're not blowing smoke.....that figure is found in the RSTOL AFM and represents actual, precision flight test measurements with a gimball mounted flight test pitot system.

If that same person says their VG's decreased stall speed by 7 knots, ask them how they came up with that "data".

MTV

Only STOL kit install I was around took forever because the old Boeing mechanic refused to use the pop rivets supplied in the kit. I think it was a Horton. And the coffee breaks were really long. As I recall there were a couple of exceptions made where there was no way to buck a solid rivet. It was a near perfect installation and flew beautifully.

Just flew my '79 180 Skywagon (Texas Skyway O-550, float kit, Snider speed kit) home on 12/17/20 after getting Sportsman STC. Here's what I found:

So that I didn't land in the dark with a new Sportsman cuff, I flew home at 24 squared at 150 knots which looks like the Sportsman did NOT cost any top speed.

Stall speeds actually increased 0 - 6 knots ranging from 0 - 4 notches of flaps. That was a shocker! I want to do more AFTER SPORTSMAN testing in 2021 when the weather conditions are more similar to our BEFORE SPORTSMAN testing. I'll complete my before/after comparison spreadsheet after that testing.

At 3000 feet AGL I was flying a 500 ft/min decent (normal approach decent) varying around 47 - 50 knots carrying a little bit of power to produce air across control surfaces (ailerons, elevators, and rudder). My goodness!

Then I decided to do an actual approach. Instead of an approach speed of around 75 knots with an "across the fence" speed of 63 knots before the Sportsman, my approach speed felt quite stable at 55 knots and I slowed to an "over the fence" speed of 50 knots. Wow, what an improvement! I want to stress that my wagon felt more stable at the 50 knots than it did before the Sportsman at 63 knots when it felt pretty mushy.

Landed in 400 feet. Will probably reduce that landing distance with more practice.

After the Skywagon will be getting extensive work done on it for the next few months (new utility interior/painting, avionics/panel incl Garmin 3X touch), I'll fly for a month or two. Then will probably add vortex generators on the main wing, elevators and rudder to provide even more control authority.

As many of you have stated, the Sportsman is a MAJOR improvement!

Kevin Voges wrote:.
Stall speeds actually increased 0 - 6 knots ranging from 0 - 4 notches of flaps. That was a shocker! I want to do more AFTER SPORTSMAN testing in 2021 when the weather conditions are more similar to our BEFORE SPORTSMAN testing. I'll complete my before/after comparison spreadsheet after that testing.
As many of you have stated, the Sportsman is a MAJOR improvement!

You had me going there for a moment.....I think you meant your stall speeds decreased , not increased......

Sounds like a nice machine

MTV

You had me going too until the last sentence, I just about called about that plane but ended up getting what I think is a good airframe that is very original and I can spend some money. Got the new Pponk and maybe I'll do the Sportsman and ........... By the way, I read about your business and it sounds pretty interesting. Do you need to set one up in Northwest Iowa------my town is looking for something like that.

MTV,

No, you read it correctly. My stall speeds actually INCREASED with the Sportsman.

Here's some data:
Before Sportsman no flaps 55 knots After 55 knots
Before Sportsman 10 deg flaps: 46 knots After 49 knots
Before Sportsman 20 deg flaps: 44 knots After 46 knots
Before Sportsman 30 deg flaps: 41 knots After 45 knots
Before Sportsman 40 deg flaps: 39 knots After 45 knots

I am going to do another stall test when the weather gets as warm/humid as when I did the BEFORE test. (My thought is that because my AFTER Sportsman was done with colder weather, the stall speeds should be even less.)

Maybe the wagon is flying at a different angle of attack with the Sportsman resulting in showing a faster indicated airspeed than actual OR the Before test was showing a slower indicated than actual OR a combination of both...'not sure.

I have no doubt though that this wagon is flying much more stable at slower speeds and is allowing me to fly 50 knots at 13" mp with 4 notches of flaps "over the fence" into a very benign/docile landing. A lot more lift now. Before the Sportsman at 13" mp, it fell out of the sky at any speed < 63 knots and felt very mushy. The difference is quite radical and I can't be happier...except for one thing...please read on.

The first time my short approach was 50 knots, in error I cut the power about 10' feet above the turf. I lost elevator control and it fell like a rock. I now keep that power in right until those tires touch, then cut the power allowing the tail to come down when it's ready.

Willie Stein told me that he loves his Sportsman on his '77 185, but the VGs helped with more "control effectiveness" as he put it. I too will probably add VGs after a few more months of flying with the Sportsman.

After just a few days of flying with the Sportsman, I've already started tearing it back down for utility interior paint, new seats, flooring. Then off to the avionics shop for a 3X Touch, etc.

I am absolutely a rookie. A previous Mooney/Cirrus pilot with some aerobatics sprinkled in. If you, MTV, or anyone else has advice for me, I encourage it. I need to learn as much as I can.

God's wonderful blessings to all this CHRISTmas.

Kevin Voges wrote:.....I have no doubt though that this wagon is flying much more stable at slower speeds and is allowing me to fly 50 knots at 13" mp with 4 notches of flaps "over the fence" into a very benign/docile landing. A lot more lift now. Before the Sportsman at 13" mp, it fell out of the sky at any speed < 63 knots and felt very mushy. The difference is quite radical.....

To me, this is the value of a sportsman cuff, or a VG kit--
added control effectiveness at low speeds.
Much more important IMHO than cutting a couple mph off the stall speed.
I have a totally stock wing on my 53 180.
It's a little mushy when slow, & I've thought about adding VG's,
but I was under-impressed with them when I put a set on my old C150/150TD.
A sportsman cuff would probably be the way to go, but a lot more work & cost-
plus, I really like the way my stock aluminum wingtips look.
I don't care for any of the fiberglas tips including the ones that come with the sportsman.
I've seen a couple pics where a fence was installed at the outboard end of the cuff,
to allow for mounting the stock tips, but I don't care for how that looks either.
Even the stock wing is pretty capable though, if you spend the time to learn how to fly it.

Kevin Voges wrote:MTV,

No, you read it correctly. My stall speeds actually INCREASED with the Sportsman.

Here's some data:
Before Sportsman no flaps 55 knots After 55 knots
Before Sportsman 10 deg flaps: 46 knots After 49 knots
Before Sportsman 20 deg flaps: 44 knots After 46 knots
Before Sportsman 30 deg flaps: 41 knots After 45 knots
Before Sportsman 40 deg flaps: 39 knots After 45 knots

I am going to do another stall test when the weather gets as warm/humid as when I did the BEFORE test. (My thought is that because my AFTER Sportsman was done with colder weather, the stall speeds should be even less.)

Maybe the wagon is flying at a different angle of attack with the Sportsman resulting in showing a faster indicated airspeed than actual OR the Before test was showing a slower indicated than actual OR a combination of both...'not sure.

I have no doubt though that this wagon is flying much more stable at slower speeds and is allowing me to fly 50 knots at 13" mp with 4 notches of flaps "over the fence" into a very benign/docile landing. A lot more lift now. Before the Sportsman at 13" mp, it fell out of the sky at any speed < 63 knots and felt very mushy. The difference is quite radical and I can't be happier...except for one thing...please read on.

The first time my short approach was 50 knots, in error I cut the power about 10' feet above the turf. I lost elevator control and it fell like a rock. I now keep that power in right until those tires touch, then cut the power allowing the tail to come down when it's ready.

Willie Stein told me that he loves his Sportsman on his '77 185, but the VGs helped with more "control effectiveness" as he put it. I too will probably add VGs after a few more months of flying with the Sportsman.

After just a few days of flying with the Sportsman, I've already started tearing it back down for utility interior paint, new seats, flooring. Then off to the avionics shop for a 3X Touch, etc.

I am absolutely a rookie. A previous Mooney/Cirrus pilot with some aerobatics sprinkled in. If you, MTV, or anyone else has advice for me, I encourage it. I need to learn as much as I can.

God's wonderful blessings to all this CHRISTmas.

It's the angle of your Pitot Mast. I'll bet if you had flown four direction stalls monitoring GPS ground speed, you'd have found that stall speeds decreased, not increased.

MTV

I fly a 1953 180 with a sportsman. While I suspect my airspeed indicator could read low, my stall at 40 degrees flaps, is well under 40MPH indicated. And my cg is at the forward limit when it’s just me and fuel. At 40 I don’t even have a stall horn going off.
How can it be that much different from one 180 to the next?

.

Kevin Voges wrote:....Snider speed kit

If you still have flap gap seals, remove them, instead of the wing just quitting flying you’ll get just a mush down. Won’t affect the elevator but will the wing.

If you want to add VG’s I suggest going with BLR not Micro. BLR’s VG’s were developed when Robertson was part owner of the company. Robertson as in Robertson STOL. I’ve had both and BLR is superior. Speed improvements are documented by BLR as part of the STC just like the Robertson STOL. You won’t need to install VGs on the rudder or elevator either as BLR uses a “Delta Wing” mounted on top of each wing at their roots. These energize the tail. BLR VGs are available for the J & K 180 and the A185F.

Very good point, MTV. Yes, I think you are correct and will do what you recommended.

Barnstormer, there are no flap seals included with my Snider Speed Kit.

StillLearning, you mentioned that your stall speed on your '53 180 is "well under 40 mph". Let's make a conservative assumption and say that your stall speed is 38 mph which equates to 33 knots. As glacier said, you may want to check your speeds via GPS in four directions as MTV recommended, right?

Glacier said that out of ground effect, he can hold his plane at 45 mph which is 39 knots. That's pretty close to what my '79 is achieving with wheels. My '79 Skywagon has a Texas Skyway 0-550 and a float kit so it's probably a little heavier at 1805 lbs than your '53 180, but 33 knots stall speed sounds ultra low.

Thanks to all for your comments.

Doing an approach stall, my 53 180 lets go at about 44 mph indicated.
I had a different airspeed indicator in it for a while, that one indicated over 50 at stall.
Both indicated about the same airspeed at normal cruise power settings.
So there can be a lot of differences just between instruments.

Best way to compare would seem to be in totally no-wind conditions,
using GPS groundspeed as a reference.
And then do it using 4 different headings, 90* apart, just in case.