Do any of you have experience with robertson stol? Whats your opinion, and do you fly it much differently than a stock wing?

Have a Robertson Stol 185 on straight PK3000 floats with a Cont 550.
Didn't find much difference between it and stock wing.
Recently added Micro vortex gens and now I do feel a difference.
Especially with full load on hot days getting off rough water when I need to.
It routinely gets off quicker during normal operations at any flap setting, but if needed, after on the step and gaining a little speed, just jerk the elevator all the way back, pop in full flaps and it flys.

Thanks for the reply,i am not unfamiliar with the concept as i have droop ailerons from cubcrafters installed on one cub.It just seems like in the 185 that the cross wind doesnt lift a wing as bad,probably because of the weight of 185.I have all the original paperwork for the 185 except the robertson supplement.It looks like it was ordered with the amphibs and robertson stol.

Interesting takeoff yesterday with the State 185 (Micros and Robertson). Tom came in the hangar last night and told us that he was at gross weight and elected not to use the ski strip (State airplane has Federal hydraulic skis) over at AIT but rather the 4000 foot paved runway. Well, they have 1 inch+ of glare ice on the entire runway and he ended up making a 20+ degree off heading takeoff the whole run. He was afraid to abort because he didn't know if pulling the power would send the airplane into the woods or just what might happen so he just rode it out (I'm going the direction I want to go) along with the wide eyed DNR types along and it worked out fine.

Brad

The DNR types around here love the VG and Robertson combo for ski operations

Interesting take off.
The combo of RStol and VG's make a nice difference on the 185.

I had a Robertson STOL kit installed on a C-180 back in the mid 80's. This model of the 180 had the old wing profile that was very forgiving. After the STOL kit was installed, the leading edge was then drooped with a cuff riveted over the stock wing profile, which is a NACA 2013 (approx)

Anyway, at the same time, I had the instruments done to IFR standard, including a new ASI that was calibrated very accurately and read only knots.

After the mod was completed, I was out one day flying it over Kamloops Lake demonstrating the STOL qualities to a fellow pilot and we began to do some very slow flight at about 5000 feet above the water. Imagine my surprise then, when we suddenly found ourselves inverted, looking up at the lake through the upper windshield. The Robertson mod really works, make no mistake, but you ABSOLUTELY MUST fly it according to the numbers. When they say it will fly at 42 knots for a certain weight, do not fly it one knot slower than 42 knots.

I found that the Robertson kit had changed my airborne steed from a very docile, forgiving airplane to a merciless, totally unforgiving falling object when pushed beyond the limit.

There was also a local fellow pilot at our little grass strip in the Fraser Valley of B.C. He was out one day, solo, practicing STOL landings and take-offs in his Robertson 180. We watched in awe as the 180 executed steeper and steeper rotations and climbouts. Suddenly, without warning, while the aircraft climbed to about 40 feet at a very steep deck angle, boom! It snapped inverted and crashed nose down breaking both of the pilots legs, among other injuries.

The moral of this story, is to be respectful of the numbers when flying you Robertson Cessna.

Cheers, Pete

I've flown several 185's and several 206's with Robertson kits installed. Some thoughts, for your consideration:

1) If you didn't get a Robertson Flight Manual Supplement with the airplane, you REALLY need to get one. Two reasons: first, the airplane is not airworthy unless a RSTOL Supplement is aboard at all times, and second, because the supplement is a wealth of important information on the characteristics of the kit.

2) The RSTOL kits droop the ailerons incrimentally, with flap deployment. When you go from 30 degrees of flap to 40, however, the ailerons actually retract two degrees. Check your airplane and make certain this occurs. IT is possible to misrig them so that they just keep coming down, and that is not good. The Cub Crafters cub droop aileron kit does this, and I do not like that kit at all. But, the Cub has very different ailerons as well. Different story.

3) As noted by other posters, the RSTOL kit definitely lowers the stall speed of the airplane (to 37 knots in the 185), and that was documented and proven in flight test. Ask the VG manufacturers what the documented flight test reduction in stall speed is for their kits. Blank stare. This is a huge reduction in stall speed in these airplanes.

4) Also noted by other posters is that the RSTOL airplanes do tend to be a little more abrupt when they depart in a power on stall. Frankly, I disagree that they are significantly worse, but it's really all up to the pilot, and what he or she does with the rudder pedals. I would characterize the departure as "slightly more abrupt", not as cataclysmic, as some have suggested. The airplane will not get on its back if the pilot is flying it. I've done falling leaf stalls with and without power in these airplanes, hard maneuvering in the stall, etc. If they break from an agressive stall, it will be an abrupt break. Nuff said.

5) The RSTOL airplanes offer the pilot so much advantage and buffer in the slow speed range that I really like them. But, I basically fly them almost as if they were a stock wing airplane. That way, you have a lot more margin for error.

6) As to takeoff performance, they are spectacular. This can tend to lead pilots to practice very steep departures. Sooner or later, this can lead to failure. Duh. Super Cubs and Huskys are just as well known for this characteristic.

In my opinion, the Robertson STOL kits are a fantastic addition to the Cessna aircraft. THere is a slight loss of roll control with the kit installed at mid flap settings, and this can be problematic in a takeoff with a crosswind on floats, for example. That is the only area I ever saw as an issue in several thousand hours in these aircraft.

But, get the manual supplement. I believe Sierra Systems now owns the STC's, so get in touch with them, or find someone with one, and copy it. It'll make you legal, and give you a lot better understanding of what the kit does for you.

It really is a good supplement.

MTV

What is the difference betwen the Robertson and the Horton STOL kits, if any? Thanks in advance for any replies.

Not sure about today, but in the old days, a Horton STOL kit consisted of a fence on the upper wing surface similar to a Robertson STOL or a Beaver. I think the old kit had a flap gap seal also.

I was flying an interesting Cessna 182 last year for a green pilot. This 182 had the Peterson 260 HP Conversion kit with a canard mounted on the engine nacelle, a Horton Stol kit and a set of Micro Dynamics vortex generators all over the airframe. I think the ailerons deflected with the flaps also.

One day we were out practicing slow flight with the airspeed indicating less than 30 mph. Stall warning bleating continuously. Funny thing though, the GPS never showed under 59 knots in any direction??? It was all smoke and mirrors.

Cheers, Pete

There is a world of difference between the Robertson and the HOrton STOL kits.

The Horton is simply a leading edge cuff, and a stall fence on the top of the wing. That's pretty much it. It's not a radical cuff either, and in my honest opinion, it is not worth the effort or dollars, because it does not significantly alter teh performance of the plane.

If you are going this direction, buy a Sportsman STOL kit. This is a similar type kit, but it has a very radical leading edge recontour. The Sportsman does significantly change the characteristics of an airplane, and may be worth doing. The Sportsman doesn't have a fence, but it does have aileron gap seals.

The Robertson kits, on the other hand, are primarily a functional kit that "droops" the ailerons with flap deployment, effectively creating full span flaps. As you deploy more flap, the ailerons droop more, until the final notch of flap, where the ailerons retract just a bit. The early Robertson kits also included a recambered leading edge (a cuff), and they all contain a stall fence, between the aileron and flap gap. Robertson quit providing the recambered leading edge when Cessna stole the idea from them, and recontoured their leading edges.

I have not flown one of the "Wren" conversions on the 182, but Robertson did no joke full out flight test on their kits--all of them. They documented (not claimed) a substantial reduction in stall speed. As I noted for the 185, the stock airplane stalls are around 56, whereas the Robertson airplane stalls at 37. That is a substantial change in performance, and the airplanes will do that. Step over that edge, and they get sporty, though.

Now, the VG manufacturers simply tell the FAA that their kits don't induce any adverse flight characteristics and demonstrate that. They do not verify stall speed reductions. Try to pin one of those guys down by asking him what the documented, flight tested stall speed of one of their modified aircraft is. Won't get an answer,

Robertson, on the other hand, provides this information with every one of their kits.

MTV

It was all smoke and mirrors.

The hangar door hit my leading edge so I got the Sportsman kit to cover the damage. It does a great job of that. My momma always said "there ain't no free lunch".
The best Stol mod I have is the O-520 with the three blade. Even better would be to lose a few hundred lbs.

Yowsah!! You got that right.

MTV

MTV...the VG's aren't a STOL kit...that's not what they're designed to do... what they do (and do very well) is provide more positive control at lower airspeed. The fact that stall is reduced is because they "energize the boundary layer to allow controlled flight at a higher angle of attack." I've installed quite a few sets of them, and always explain to the customer that this isn't really a STOL kit... and once they realize that, they're very happy with what they have.
In my opinion... I'd love to see the combination of both, Robertson and VG's.... I'm sure it's been done, but I haven't seen one in person yet..
JH

John,

You should go talk to the man who owns Micro Aerodynamics or any of his minions. They will tell you unequivocally that VG's will reduce your stall speed by this much, they will make your dog's breath smell better, and make your wife love you even more. Until you ask them for data.

You are absolutely correct, but my point is that these folks are SELLING them as a STOL kit, and CLAIMING significant stall speed reduction. Right up till you ask them to provide documentation.

Robertson did just that. Horton didn't, Sportsman didn't, and neither has either of the VG manufacturers.

I'm with you--as long as folks know what they are buying it's fine. And, in my experience, the VG's do precisely what you describe. Again, though, that's not what the advertising hype says. Look at their web site.

I've flown a Robertson equipped aircraft with a Sportsman leading edge. I've flown a Robertson equipped aircraft with VG's, and I've flown a stock wing Cessna with VG's.

I wouldn't install VG's on a Cessna wing again, personally. On a Cub--probably. On a Scout--definitely. They do different things on different aircraft. They mellow out the stall a little on the Cessna wing, but not enough to warrant the cost or hassles associated with them, in my opinion.

I don't operate right on the edge either, by the way. But if you do that, any of these kits will eventually get you in trouble.

The Robertson kits are the real deal. They really work, and the company documented that in flight test. A simple set of aileron gap seals really helps the roll control issue with these kits, and that's all that is really necessary.

MTV

I have some questions on the Robertson.

1) Does it buy you anything with regard to stall/climb/aircraft performance with flaps at 0deg, especially if this question is centered around post-1974 Cessna wings? Any added performance/safety region in this configuration.

2) What is the added performance envelope and aileron effectiveness when flaps are say 10 to 20 degress (Is this the configuration where the ailerons are drooped the most?). I wonder about this configuration since it is commonly observed when people are bucking a good crosswind and/or wind gusts.

3) With the later Cessna wing what was the low-end performance gain and was cruise speed affected. I've read books written by Cessna test pilots during this era and they mention a decrease in cruise speed. Is this what others have observed?

Doth,

1) On the later airplanes, the Robertson kits do essentially nothing to or for the airplane with Zero flap setting. The only thing different in this regime is the stall fence, which may in fact have a tiny effect on stall characteristics.

2) The Robertson kits droop the ailerons sequentially with flap deployment. I don't have the precise aileron droop in front of me, but at 10 degrees of flap deployment, the ailerons droop something like 2 degrees. At 20 flaps, the ailerons droop something like 5 degrees. At 30 flaps, the ailerons droop 7 degrees. When flaps 40 are selected, the ailerons retract up to, I believe 5 degrees. Don't crucify me on the degree settings, they may be off a degree or two, but that is roughly the ratio of deployment.

I never found the aileron deployment to be a SIGNIFICANT issue in a crosswind EXCEPT on takeoff with a floatplane with a GUSTY crosswind. I had times when I rejected a takeoff (and in fact a few landings, since I wouldn't be able to takeoff) due to gusty crosswinds on floats. Rare, though, and frankly this can be a hairy situation with a stock wing as well.

On wheels, I never found the kits to be a big problem. Let me clarify that by also stating that I don't land these airplanes in 30 knot direct crosswinds, there may be braver folks out there.

3) I put over 3,000 hours on a 1985 Cessna 185 with a Robertson kit. The stall speed on that airplane without the kit was 51 kts, as I recall. With the kit, it was 37. I never saw any decrease in cruise, though the kit does add just a bit of weight. I can't imagine how the kit could add any measurable cruise speed penalty. With the flaps retracted, the only thing sticking out in the wind is the stall fences, and they're aligned with the wind.

Now, on earlier airplanes, where Robertson also installed the leading edge cuff, perhaps there was a cruise penalty, but I doubt that claim in the later airplanes that came from CEssna with the Camber lift wing.

MTV

I agree MTV... the "salesmen" are just that.... "salesmen".... not much different from used cars to airplane parts! I guess technically, it is sort of a STOL kit in the fact that it might make a slower take off and landing comfortable.... and of course if it sells, they're gonna use that for sure.
JH

Thread resurrection!!!

I just wanted to tap the local knowledge here about my A185F with Robertson STOL.

1 Should the ASI have be remarked? I noticed the white arc range changes with the kit

2 Am I reading the VFE speed right, VFE with the kit gets lowered from 120KIAS to 95KIAS?

3. Is there a float supplement? All I've found for late model A185Fs is the land supplement with no mention of float ops


Thanks!

NineThreeKilo wrote:Thread resurrection!!!

I just wanted to tap the local knowledge here about my A185F with Robertson STOL.

1 Should the ASI have be remarked? I noticed the white arc range changes with the kit

2 Am I reading the VFE speed right, VFE with the kit gets lowered from 120KIAS to 95KIAS?

3. Is there a float supplement? All I've found for late model A185Fs is the land supplement with no mention of float ops


Thanks!

My 185 airspeed indicator was remarked. VFE is 95 KIAS. I don't have a float supplement either and have never seen one.

Thread re-resurrection! I just noted I have the kit installed but no POH supplement. Anybody willing to share one? TU206G, amphibian.