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Robertson STOL

skywagon,

The gap seals that Robertson provided on some of their kits were not large enough. We found some larger, more effective gap seals somewhere, don't recall where, if I ever actually knew.

I agree fully that the IDEAL setup would have been to have the aileron droop control separate from the flap control. Wayne Mackey has done that on his airplanes, and that makes a great deal of sense. Best of both worlds.

I flew two Super Cubs with the old CC drooping aileron modification, and I DID NOT like that setup at all. In fact, we took those kits off those two airplanes, or at least they disabled them.

Talk about NO aileron authority!

MTV
 
Dalfena: the owner of one of the best engine overhaul shops in the country was yarning with me when a Robertson 185 took off with a show-off climb. "See that," he said turning to me, "those guys keep me in business."
 
The Finnish government put an RSTOL airplane through a LOT (as in a couple hundred) stalls, and eventually managed to get one to roll off.......duh. I'd bet that with a few hundred tries, we could get a LOT of airplanes to roll off in a stall.

Mike, if this is your characterization of the findings of the report, you might want to read it again.


From the report:

2.8 Results of the flight tests
The accident situation was simulated during the test flight so that the indicated air speed was reduced to 40-45 knots with engine on idle power. After this full power was set. When the aircraft accelerated through 50-55 knots the aircraft was pitched up 10 de- grees using the artificial horizon. The aircraft rolled to the right on five attempts from fourteen attempts and rolled 50-70 degrees in two seconds. The simultaneous heading change was 10-20 degrees. The movement would have continued but the incipient spin was recovered. On nine occasions nothing significant happened and the aircraft re- mained under control even at a speed of 40 knots and cross controls.
 
George,

They performed a number of stalls. The ones you reference were the FULL POWER stalls. Anyone who stalls one of these airplanes unintentionally while at full power is numb from the waist up, and the guy flying the accident airplane apparently was. Read the entire report. It is simply unbelievable that the Finnish Air agency even bothered to look at the airplane, considering what the pilot told them about the accident sequence.

Take your 185 out and try some half flap, FULL POWER, FULL stalls, and report back the results. Granted, those are going to be aggressive in the RSTOL airplanes occasionally, but it is my opinion that we still use pilots because they occasionally can use some judgement. I have gotten RSTOL 185's to roll with power on stalls, as well as a lot of other airplanes. This business does require pilot participation.

MTV
 
Mike, given the R/STOL supplement procedure, with a rotation speed of 37 knots and an initial climb at 42, wouldn't a full power departure stall be the mostly likely stall to encounter in an R/STOL equipped plane-- especially if the supplement speeds are too slow?

From the report:

The R/STOL supplement states also that the STOL take off is done with the flap setting of 30 degrees. The rotation speed is 37 knots and the initial climb speed is 42 knots. The flaps are raised to the setting of 20 degrees after lift off. When the close-in obsta- cles are no longer a factor the speed is increased to 65 knots and flaps are raised.
The calculations and test flights perfomed during the investigation proved that the STOL take off speeds are slightly too slow and there is a risk of stalling. The wing stalled at a speed of 50-55 knots during the test flights when the angle of attack was rapidly in- creased approximately 10 degrees. It seems to be very important to increase speed near ground or water to over 65 knots before starting to climb. One should not turn dur- ing the initial climb.
 
George,

Go fly an RSTOL equipped 185 and try a full power stall. I've done it. It's essentially an aerobatic maneuver, due to nose up pitch attitute, AND the indicated airspeed is BURIED at zero. If you FLY the airplane off as recommended by Robertson, maintaining those speeds, with full power, you've got margin. Remember, the 37 knot stall speed is Vso, power OFF. I'll be the first to admit that a full power stall in an RSTOL 185 is an "interesting" procedure. Then again, the same can be said for many airplanes in a full power stall. Why would you LET the airplane ever get there in a takeoff, though?

I repeat, you'd have to be numb from the waist up to actually stall one of these things (or a stock 185 for that matter) in a full power climb after takeoff.

And, in reality, not many of us use the MAXIMUM performance procedures recommended by the manufacturers as a regular practice. How may Cub drivers follow Piper's recommended Vx in a routine climbout after takeoff? That calls for full flaps and 45 mph.

The guy in Finland used full power, and stalled the airplane on takeoff from a HUGE lake--as in no obstacles....AND he admitted that a) He'd never actually stalled the airplane, and b) he understood the proper procedure for takeoff on floats to be full power, set the trim and keep hands off the controls (That is paraphrasing the report, but essentially, he said he let the airplane climb with pitch). Holy cats is all I could say about that. That accident was EASILY explained and preventable.

Any airplane will kill you if you push it over into a corner, then keep prodding it until it bites. ANY airplane.

As an old friend and check airman told me once in the middle of a checkride: "It may be time to do some of that pilot ****".

MTV
 
Mike, the reason I posted the link to the report, is I believe anyone flying an R/STOL equipped aircraft, or considering flying one, should, rather than rely on your view of what the R/STOL does to a Skywagon's handling, read the complete report and what they determined in the Finnish investigation. If you read the direct causal factors, while the first is pilot error, neither two nor three is something that R/STOL would likely use in their advertising.

Direct causal factors
The investigation commission considered that there were three direct causal factors to the accident:
The first factor was the incorrect take off procedure used by the pilot. He let the aircraft continue climbing after getting airborne without reducing the pitch angle to gain air- speed. This procedure caused the angle of attack to increase and right wing to stall.

The second factor was the tip-stalling tendency of the R/STOL kit. The kit incorporates a link between the flaps and ailerons and the ailerons turn downwards in the take off con- figuration. Turning ailerons downwards is unfavorable especially with the aileron mechanism used by Cessna when the hinge line is on the upper surface. Thus turning aileron down causes a sharp angle on the upper surface and induces flow separation. This led to a sudden right wing tip flow separation. The flow separation of a normal standard Cessna aircraft begins from the wing root area, which is favorable and safe.


The third factor was the wrong action by the pilot to recover from the situation. When the aircraft begun to roll to the right the pilot applied full left aileron and rudder. Probably he did not try to push yoke forward to unstall the wing. The collision with water could probably not have been prevented even with the correct stall recovery actions but the consequences of the collision could have been reduced. The full opposite aileron can also be considered as a wrong action because the right aileron turned downwards and worsened the right wing tip stall. On the other hand, the aileron control must have been a reflex movement for an unexpected roll.
 
Yep, George--that pretty well says it all. Numbers 1 and 3 that is.

This information was provided to the US FAA and NTSB, who have taken no action to rescind the Robertson stc. Numbers 1 and 3 are probably a big part of the reason why.

We ARE expected to actually FLY these things, George.

MTV
 
180 - 185 parts are what I need. If you could do some digging ar a contact that would be great.
 
Thanks for the tips, It would be fairly easy to not hook the RStol to the flap belcrank and actuate it by other means. I will consider it.
It would seem to me that if i where in a cross wind I would use less flaps. The less flaps the less aileron droop. Heck a 180 should land pretty short with no flaps, nose will be high. I do it in my PA-12 because Piper forgot to give me flaps....Ha.........The R/Stol has its place in this world and I like it, after all, any aircraft can and will bite you if you let it. I do have a few hours flying 180, 185, 206 all with Robertson STOL.
I don't think I have seen a large Boeing or Airbus that doesn't droop every thing it's got. Stol crap comes out of the wing in every direction, only diff I see is they have spoilers to help the roll, like the Helio.
Parts?? PM me with contacts, thanks.
 
Dan,

Not quite on the using less flap. In the RSTOL airplanes, the first notch of flap deflects the ailerons a bit. The second notch deflects them a bit more. The 30 degree flap setting affords the most aileron droop, then at 40 flaps, the ailerons actually retract a bit. So, yes, you can get less aileron droop by using ten or twenty flaps, but....

And, as Nanook explained, the ailerons on an airbus or boeing are quite a lot different design than on a Cessna 185. And so are those on a 206, by the way.

MTV
 
So... tell me why you would not want to use less flap in a heavy crosswind??? Can't tell me every landing is on a postage stamp. By the way I know exacty how a robertson sysyem works, just about every cessna i have flow has had it. Can display log book if you like.
Really, ailerons are designed differently?? How, still goes up and down. lenght and width yes, hindge design yes. what its designed to do, No, still the same controls roll.

Should be alot of Robertson stol systems removed really cheap! Like I said, I am interested in one for 180-185 wing.
Thanks again. $100.00 finders fee paid for a complete system
 
Does anyone have experience with VG's on an RSTOL Cessna? Would VG's on an RSTOL Cessna have any negative consequences, ie: worse break from a stall?

I fly a RSTOL TU206 with flint tip extensions/tanks. I have about 350 hours on this AC. With flaps down the ailerons droop and aileron travel is restricted so the roll rate is not as good. I've learned that it takes more roll input at landing speeds and never had a time where I felt that I did not have "enough" aileron authority. If there is a moderate or greater crosswind, then I reduce flaps to 10% (less aileron droop) and increase my take-off/landing speed. So far I like the RSTOL.
 
"The less the flaps the less aireron droop" is not true on my Robertson STOL Cessna 172. Aileron droop reaches it's max at about flaps 25, then backs off towards less droop as the flaps are further extended to 40 deg. In 1983 I flew a few Robertson equipped Cessnas with the factory pilots when they were located in Everett, Washington (they built the B1RD ultralight there). They explained that the max droop/flap setting was based on the available horsepower, so that a full flap go-around wouldn't be impossible due to high drag. C-182's for example, reach max droop at about 30 degrees of flaps.

I have a 180hp constant speed conversion in my airplane, and have flown it since 1981. As long as I fly it like the book, it doesn't bite. I have heard that BLE's make the ailerons more effective at slow speeds, but am waiting to fly one before I do that to mine. My STOL takeoff per the book is rotate at 40mph, climb at 55 mph, and it works well. Landings are flown per the book at 50 mph at max ldg. weight. The airplane behaves well if these speeds are used....
 
Don't think anyone said "The less the flaps the less aireron droop" The amount of droop vs flap setting on your 172 sounds about the same as my 206 RSTOL system. I am considering VG's to improve the control at slow speed.
 
You're right--I misread the thread where that was said. MTV's post got it right on the Robertson flap/aileron droop relationship.
 
I'm looking at a 180 with just Robertson leading edge cuff and fences, it does not have and it has never had the drooping ailerons,
does anyone have experience with this setup, it looks about like a Horton
 
I'm looking at a 180 with just Robertson leading edge cuff and fences, it does not have and it has never had the drooping ailerons,
does anyone have experience with this setup, it looks about like a Horton

Yes, it looks about like a Horton, or an Owl, or a late-model Cessna "camber-lift" leading edge.

The Horton really does come alive with MicroAerodynamics VG's on it. In comparison.......I'd rather have a micro-vg equipped early 100-series leading edge than a Horton leading edge without VG's......I'd rather have a Sportsman-equipped leading edge without VG's than a Horton with vG's, and I'd still rather have an RSToL and VG'ed wing than the others.

I have just re-read this whole thread.....George M., why does the Finnish Accident report even matter in any discussion of RSTOL performance when the pilot so-obviously allowed the aircraft to pitch beyond critical? His failure to excersize piloting skill would crash any airplane. I really am not interested in an argument.......just a reason why I should care about the Finn's findings when the pilot really just screwed up.........
 
okmike, there is nothing wrong with the Robertson cuff or fences. There is a lot wrong with the aileron interconnected to the flap via bellcranks and push pull rods. You are looking at the best of the Robertson system minus the worst. You should be happy with that arrangement. The VGs will only improve what you already have.
 
I'm looking at a 180 with just Robertson leading edge cuff and fences, it does not have and it has never had the drooping ailerons,
does anyone have experience with this setup, it looks about like a Horton

Id make certain that the airplane is LEGAL in that configuration.

that would require a field approval for removal of the aileron/flap interconnect. You can't just remove half of an STCd system without FAA authorization.

The RSTOL cuff was pretty minimal in camber, which is why Robertson quit using it after Cessna re-cambered their leading edge from the factory.

I agree with Dave: If you're doing a cuff, go with the Sportsman....it's head and shoulders better than any others.

would I remove a Robertson cuff, if that and fences were all of the kit that was left? No, as long as I could get the FAA to buy off on it.

MTV
 
Not installing the droop parts was very common with Robertson kits. Most pilots with half a brain left could figure out what restricting your aileron travel in a cross wind would do for you....
 
Mike. I disagree. There is a stipulation in the Regs. for a partial installation of an STC. I forget where it is, but I have read it. I think it was intended for an ongoing alteration and not a permanent thing. Kinda like a Progressive Inspection.
 
I have just re-read this whole thread.....George M., why does the Finnish Accident report even matter in any discussion of RSTOL performance when the pilot so-obviously allowed the aircraft to pitch beyond critical? His failure to excersize piloting skill would crash any airplane. I really am not interested in an argument.......just a reason why I should care about the Finn's findings when the pilot really just screwed up.........

First, not sure I should answer this as Mike V and I exchange Christmas cards, and I want to keep it that way. :)

Just a quick response here, and I haven't gone back to review the whole thread. If the Finn report were the only issue, perhaps you would have a point. However, that their aviation authorities went to the considerable trouble to look into this, despite the obvious crappy piloting, might be a clue. There was also a crash south of Iliamna in a 206 (Ted Gerken's sp lodge) attributed to lack of roll control with R/STOL compared to a stock wing, that resulted in a monetary award. And, a friend of mine and chief pilot of Viking in BC, crashed a 180 into the ocean giving a check ride, related to lack of roll control with R-STOL. As I probably mentioned before, Beegle's jokingly calls this their single favorite Skywagon wheel plane mod, as it results in so much repair business for their company. Dave Younkin, who has forgotten more than I know about Skywagons, would remove R-STOL, at considerable expense, on every state of Colorado 185. I just couldn't stand the R-STOL on the 185 we got, and got rid of the plane at some expense. That opinion was shared by a friend who flew it, and operated a non- R-STOL 185 135 for thousands of hours. Interestingly, the new owner promptly ground looped the plane after getting it, which may mean something or nothing depending upon your view on R-STOL.

If you operate on floats into the wind, it may be a great mod. If you were able to disable the droop/reduction in up aileron, it might be fine on wheels. There was a mod people were doing that kept the cuff but got rid of the droop, but I am not sure that goes in today's approval world. As always, it is the indian and not the arrow, and a skilled pilot can no doubt work with R-STOL. I just think Sportsman/Wing X/ VG's is another approach to improving performance with less of the negative attributes of the R-STOL in gusty conditions.

I fought the concept of Wing X for years, but am now amazed at how much slower the plane can fly with it.
 
Thanks for the civil answer George. :) I had mentioned the attributes of WingX to you at one point and I recall your unwillingness to add the weight......all I could do was laugh at your naivete about the subject.

Nanook, who pissed in yer coffee?
 
Thanks for the civil answer George. :) I had mentioned the attributes of WingX to you at one point and I recall your unwillingness to add the weight......all I could do was laugh at your naivete about the subject.

Let me publicly eat crow on the Wing X. You and Jeff Walker both mentioned it to me, and I resisted for years.

We put it (Wip Tips the 206 version) on a float 206 along with the Sportsman, and it flew so slow afterwards it was crazy. Tried in on the late model 185 my wife uses, and it changed its short field performance into that of Fireball, the super light 62 185. Then Fireball got the Wing X, and it now performs like a mid weight Husky. Even though the Wing X has taken away some roll control in gusty conditions, overall and surprisingly, the Wing X has made that light 185 ride much more comfortably in turbulence, besides the short field benefits. I am now a major Wing X believer. Not that we plan on flying it at gross, but with Wing X, Fireball has a useful load greater than its empty weight.
 
George, have you flown it at gross?

I will loudly proclaim that an early C180 with wingX flown at 2950 is a better performer than the same airplane at 2550 without wingX. .....certainly while on the wing, if not during rollout or early takeoff run.

Have you flown the 185 at UP-gross? This is the other regime where wingX SHINES! I wanna know what you think.

......:) so you are willing to give away some aileron authority to gain the positive attributes of wingX.......? :)

What flavor of VG's????
 
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