Interesting comments, largely based on assumptions and “I heard’isms”.
TheSportsman and RSTOL are two very different modifications to the stock Cessna wing. I flew RSTOL equipped Cessna 185 and 206 working aircraft for 28 plus years, and several thousand hours. I love both mods, especially when installed on the same airplane.
First, let’s look at speeds. Stock C-185 POH calls out full flap stall speed of 49 knots. With RSTOL installed, the full flap stall speed is 37 knots. That’s 12 knots difference, which is very significant, much greater than ANY other “STOL kit”. Second, that stall speed change was documented by Robertson to the FAA during certification. Look at an RSTOL equipped airplane’s airspeed indicator: the markings reflect that decrease in stall speed, and the RSTOL incluses a “Flight Manual Supplement” which outlines those different speeds. In my experience, Robertson is the ONLY STOL mod that went through the rigorous flight testing required to actually, officially DOCUMENT what the kit does. Now look at the airspeed instrument in any of the other “STOL KITS” out there: Owl, Horton, Micro VG and yes, Sportsman. No change in speed markings…..why? Because those manufacturers essentially assert in their certification that their mods do not create any adverse flight characteristics. Yes, they were flight tested, but they have not documented ANY decrease in stall speed to the certification process. If they did, they’d have to re-mark the a/s instrument. Now, don’t get me wrong, I am NOT suggesting that those mods do NOT decrease stall speed, only that there is no official recognition of what that is. And, yes, in my experience, all those mods do either reduce stall speed some or alter stall characteristics. Just not as much as RSTOL.
RSTOL equipped aircraft droop ailerons with flap deflection, progressively, up to the 30 degree flap setting, where aileron droop is greatest. Increasing flap deflection to 40 degrees reduces aileron droop some, but that does NOT reduce aileron droop to zero. Understanding this is key to operating these airplanes. Increasing flap deflection crosswinds, I nearly always opted for flaps at 20 degrees. That offers most of the stall speed reduction of the RSTOL kit, while retaining MOST aileron effectiveness. In very GUSTY crosswinds, I sometimes opted for a no flaps landing, with or without an RSTOL kit installed. And, frankly angling into the crosswind to reduce x-wind component should be a technique in EVERYONE’S skill set. And, yes, I’ve landed RSTOL equipped airplanes in some significant X-winds.
I LOVED the comment about crosswinds never being an issue on floats…..that’s a pilot who’s never worked seaplanes in narrow sloughs, rivers, etc, obviously. One thing EVERY aspiring seaplane pilot should experience is crossing takeoff and landings…..and takeoffs are generally more challenging….but I digress.
At one point, our aircraft division wanted to “test” install a Sportsman kit on one of our 185s. They chose my assigned 185, largely because from experience, they knew I would offer an unbiased opinion in my report (and I would write a report). So, the Sportsman kit was installed on this 1985 airplane, which was equipped new with RSTOL.
Now, one characteristic of the RSTOL kit that hasn’t been noted to date in this thread is that OCCASIONALLY, RSTOL equipped airplanes, if driven to a very deep stall, with power, MAY break in the stall rather enthusiastically, and roll. This is not dangerous at altitude, the airplane recovers with proper control inputs, quite normally. But, because of that tendency, most smart RSTOL operators do not approach to land close to earth in the very bottom of that speed range. “AHA”, you say…..”what’s the point of having such a low stall speed if you can’t use it for landing?” Simple answer: The decrease in stall speed just permits one to lower the approach speed generally….most pilots I know don’t approach right AT stall speed…..the RSTOL provides a nice buffer, even at supignificantly lower approach speeds.
BUT, what I found immediately with the Sportsman added to the RSTOL was that I could push that airplane into the deep far reaches of the stall, power or no, and all that sharp break was GONE! Stalls became a very mellow operation, at very slow speeds. Now, I found myself actually approaching at VERY low speeds. Even my non pilot boss remarked how slow I was landing, and he knew nothing about the change in equipment.
Now, however, comes the best news: the Sportsman kit for the 185 comes with aileron gap seals, in addition to the significant leading edge droop. You see, the 185 has very basic, simple ailerons, which are not very effective, frankly, RSTOL or not. But, with the Sportsman kit installed, I got much of the aileron authority lost to the RSTOL back. Which meant that Sportsman kit was the second best thing we did to that airplane. RSTOL being the best.
After ten years (literally to the day) flying that 185, the crankshaft broke, and I parked the plane on a mountainside, not veryy elegantly. Doors still opened so it was a good landing, but plane was totaled.
When our aircraft folks asked me what equipment I wanted on the replacement airplane, my response was “RSTOL, Sportsman, and fuel flow computer.” Period. And so it was.
Sorry for the long rant, but there is sooooo much “stuff” out there about RSTOL that is based on hearsay.
