Modified Frise style ailerons

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luked

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On the SSSC the ailerons are hinged by piano hinges on the top surface . More up than down, ( don't remember the amount without digging through the plans). Has 28' of span with a 48" cord , 24" wide fuselage. Each aileron is 7' long by 12" cord. You can bank the wings up to 20 degrees with your feet on the floor and the ball will stay centered. Over that you need just a little rudder. Ailerons are light and responsive. Same for the elevator and rudder. Everyone that has flown it, loves it.
The aileron differential on my 150 is about 2 to 1. I planned to provide some differential by the use of a cable driven bellcrank in the wing (again, like the 150, 172, etc.).

I watched a video of your SSSC, and it looks very nice. Looks fun to fly too. Does the differential control the adverse yaw over the full speed range? Also, does the leading edge hang down into the airstream when the aileron goes up?
 

TFF

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Look at a TBM 700 through whatever number they are up to, there is a drag spoiler or spoileron that is connected to the aileron that adds more drag for the up aileron to counter the down aileron. The ailerons are small relative to the span. Fly on an airliner, they have the same thing. Outboard spoiler follows the up aileron.

Aerobatic airplane, pure control without coupling. The fancier the plane the more the coupling has been removed. A Citabria is going to be a knife fight in the cockpit. A decathlon especially with the new ailerons is less. Run through the gamut. Get to the Extras, Sukois, MXs and coupling will be like an RC aerobatic airplane.

Big barn door ailerons will require more muscle than thin ones. Any Grumman is pretty light for a certified plane. Nothing crazy, but easy to roll. They have a thin chord so one isn’t having to muscle it. An Extra in a dive at 200 mph with the huge ailerons and then the pilot wants to max roll, it will take some muscle if there is not some help. Aerodynamic is free compared to hydraulic like power steering. You have counterbalances aero and weight, spades, hinge line at a certain point all mixed to the leverage that can be applied to the stick. For them they want it as light as they can stand because they are slamming the stick full one side to the other whenever they see fit.

Long wing, short wing. Shorter the wing, the less it is a problem. the farther the ailerons are out, the more leverage they have. That’s one of the Grummans and RVs reason for the platform.

It’s all trade offs. Short wings, long wings, big ailerons, small ones, leverage, hinge line, differential, airfoil, aileron airfoil, wing placement to the fuselage, platform, cable, pushrods, on and on.
 
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luked

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Eliminate Frise and now you need more rudder. More drag there, maybe not as much as the Frise, but drag nonetheless. It's not so simple.

My Jodel needed rudder to stay coordinated, but its rudder and fin were all one piece, and the whole thing moved. It had a symmetrical airfoil section and some aerodynamic balancing, and was extremely powerful. Didn't need a lot of effort or movement at all. It could do awesome slips because of that power and the non-differential ailerons that had a lot of travel.
All good points. I wasn't necessarily considering dropping the Frise ailerons. It might be a matter of choosing which flavor (Cessna vs. Vans, etc.), or maybe another option that I'm not aware of. I may drop them though if for instance differential alone would be adequate to avoid the need for significant rudder input. If I drop the Frise style I would probably consider a Grumman style with differential. Lot's of possibilities. Appreciate the different perspectives.
 

Dan Thomas

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Well, you're probably right. I just measured the trailing edge of my plane with a tape measure where it meets the flap trailing edge. Maybe I should double check the rigging. Seems to fly pretty well though.
Most of the Cessnas I worked on over the years had their control systems out of rig to some degree, sometimes by a lot. It's because way too many mechanics fix stuff without consulting the service manuals regarding rigging procedures. I retired four years ago, but worked on two 150s in the last couple of months; in one of them I found the ailerons badly out of rig. The other was out by a hair, but serviceable. It was within tolerances.

When I was still working I would often have to rerig a whole airplane, and the owner would exclaim at how nicely it flew afterward. That tells you something: the manufacturer knew what was necessary and why it was necessary and they published thick service manuals to tell mechanics all this stuff. But some mechanics already know it all, and screw things up.
 

luked

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Look at a TBM 700 through whatever number they are up to, there is a drag spoiler or spoileron that is connected to the aileron that adds more drag for the up aileron to counter the down aileron. The ailerons are small relative to the span. Fly on an airliner, they have the same thing. Outboard spoiler follows the up aileron.
I found some pictures. Those flaps go almost to the end of the wing. I also found a picture of a crashed TBM where you can clearly see extended spoilers on top of the wing near the ailerons. Very interesting.

I understand that every variable in the design is a trade off with other variables, and in the end I will probably end up with something that's pretty conventional. I just want to explore the edges of the envelope a little as I nail down a configuration.

I've actually made up a spreadsheet of multiple aircraft of interest. It includes many characteristics for comparison. Many are ratios for more apples to apples comparison. Things like wing loading, span loading, aspect ratio, power to weight, Aileron to flap span ratio, percent chord for flaps/ailerons, etc. It's just one more thing to mull over as I think about ideas. It helps me to see if I'm straying too far from conventional norms. Not that it would be bad, but I guess I should have a compelling reason to do so.
 

challenger_II

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Well, you're probably right. I just measured the trailing edge of my plane with a tape measure where it meets the flap trailing edge. Maybe I should double check the rigging. Seems to fly pretty well though.
You might try a digital level, rather than a tape measure. Use the CG "leveling" mark as your "zero".
 

MACOWA

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The Smith DSA used Frise ailerons to good advantage in such a short coupled aircraft. I've still got the lower wing set and have had thoughts of using the hardware for a similar setup on my current project, it being rather short as well.
 

edwisch

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* Frise aileron proverse drag improves handling qualities. For many missions, pilots have other things to do than work the rudders all the time.
* Ailerons can be hinged aft of the leading edge, but too far aft leads to reduced margin for aerodynamic flutter.
* Piano hinges don’t work on bigger airplanes. In addition, the friction of piano hinges degrades control feel. Sensuous control feel is why pilots appreciate planes appreciate the RV series and the SF260.
* The normal ideal ratio of control forces is ailerons 1, elevators 2, rudders 4.
* Spades have a lot of drag, relatively speaking.
* A yaw damper is not considered fly by wire, nor are autopilot servos. True fly by wire normally refers to electronics between the sole connection between the control wheel and the control surfaces. Some planes are in that gray area in the middle, some control surfaces electronically controlled, some straight hydraulics.
* As pointed out, differential deflection can reduce adverse aileron yaw.
* And if you really want to get into minutiae, the P-51 and others had ailerons that were not in line with the wing surface ahead but stuck up a little bit to get out of the boundary layer. Want more? Look at the effect on stick force of blunt versus sharply pointed trailing edges. On the RVs, Frise ailerons provide a handy place to put weights to statically balance the ailerons. On the LongEZ, the first part of stick deflection gives a nice roll rate but additional stick deflection gives little additional roll rate. There’s lots to consider in airplane design, lots…
 

nestofdragons

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I heard about Frise-ailerons or -elevons for the first time when reading about Horten flying wing gliders. The Horten HXa had frise-elevons. He didn't use it any more in the HXb.
The Frise-elevons are mentioned here (near middle of page):
The frise-elevons are being mentioned very briefly in this remark about the HXc:
If you want to see the HX-gliders, go see the links at the top right of that page.
 

wsimpso1

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* Piano hinges don’t work on bigger airplanes. In addition, the friction of piano hinges degrades control feel. Sensuous control feel is why pilots appreciate planes appreciate the RV series and the SF260.
* The normal ideal ratio of control forces is ailerons 1, elevators 2, rudders 4.
Please be careful using absolutes.

Piano hinges don't work on bigger airplanes? On Aeroshell Square one time I was surprised to see really long piano hinges swinging what sure looked like ailerons. IIRC, it was TR-1 (current version of U-2). Long ailerons with piano hinges...

Someone once stated that the ideal ratio is 1:2;4, and it has been echoed a long time. Other folks say the ideal is 1:2:3. I am one of those guys who is suspect of integer ratios and claims as to ideals - Our skeletal, muscular, and sense systems did not evolve around some particular integer ratio, are not linear in feel nor force output, and our proportions vary between people a fair amount. Yes, I do have graduate school training in human factors.

I do suspect that those ratios are pretty good territory to aim for, but there is nothing magic about achieving exact results on this sort of thing, unless you have a contract with the customer that says what the ratio must be and how it is measured. Get in the ballpark using base design (TOWS has a chapter on high lift devices, and our control surfaces model as flaps nicely) and be prepared to fool with linkage ratios/gearing, aerobalance, tab sizes/gearing/degree of servo/anti-servo, downsprings, bobweights, centering springs, etc.

The goal is to be able to fulfill your mission well. If you are doing aerobatics, you do not care about adverse yaw, but you do want all the roll rate you can get, so you might build a symmetric wing with symmetric ailerons carrying a lot of aerobalance and provisions for spades, and make the control forces light enough that flying at high g's and roll rates does not tire you quickly. If instead you are building a cross country machine with instrument capabilities, you might like ailerons designed to eliminate adverse yaw, all controls nicely self center, and response in all three axes are well damped... Your bird, you get to pick.

Billski
 

wsimpso1

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Also, Cessnas do not employ Frise-type ailerons. As a miner reference:
Depends upon how you define "Frise aileron". A number of definitions seem to be in play... If we can be pointed to a description of Frise Ailerons that is considered definitive and widely used within the industry, I am all ears.

Some definitions specifically indicate a hinge on the bottom airfoil surface and a sharp leading edge that deflects into the airflow when the trailing edge is up. Other definitions are broader - not specifying vertical hinge placement nor leading edge radius - only specifying that the leading edge goes into the airstream when trailing edge is up - how you get that effect is up to you.

The top surface hinged ailerons on many Cessnas and Cherokees do have a leading edge forward of the hinge and do deflect into the airstream when the trailing edge is up, but not when down. That meets the broad definition but not the narrower one. Other ships run with the hinge line slightly below the bottom airfoil surface, and meet the other broad definition, but not the narrowest definition... Vans' aircraft seem to have a nice blend of aerobatic capability and good manners in cross country flight.

Billski
 

Pops

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The aileron differential on my 150 is about 2 to 1. I planned to provide some differential by the use of a cable driven bellcrank in the wing (again, like the 150, 172, etc.).

I watched a video of your SSSC, and it looks very nice. Looks fun to fly too. Does the differential control the adverse yaw over the full speed range? Also, does the leading edge hang down into the airstream when the aileron goes up?
WOT is just about 95 mph in level flight. Yes, no adverse yaw over most of the speed range. Never tested at WOT. Start a slow bank rate with you feet on the floor and the ball will stay centered until passing 20 degrees and then it starts going off and a little rudder is needed. No, the ailerons hinges are at the top of the skins so the LE does not go up in the airstream.

Dan is correct-- Most Cessna's are out of rig in varying amounts. Rig it by the Cessna Service Manual and see the difference.
 

BJC

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I am one of those guys who is suspect of integer ratios and claims as to ideals
For aerobatics, I prefer that pitch and roll stick forces be identical and light. See below.
If you are doing aerobatics, you do not care about adverse yaw, but you do want all the roll rate you can get, so you might build a symmetric wing with symmetric ailerons carrying a lot of aerobalance and provisions for spades, and make the control forces light enough that flying at high g's and roll rates does not tire you quickly.
I like to be able to very easily take the stick, backhanded, to the roll stop at Vne. Yes, I know that that isn’t Va.


BJC
 

speedracer

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My understanding is that Frise type ailerons provide two main benefits. First, as the trailing edge rises, the leading edge dips down into the airflow below the wing, and increases drag to help counter adverse yaw. Also, that drag can help counter the hinge moment and decrease stick forces.

In most Frise type ailerons I've seen, the leading edge nose or point extends the full span of the aileron. I'm wondering if there are any examples where this feature is only on the outboard portion.

My thought was that the further outboard the drag is created, the more benefit it provides in terms of countering adverse yaw. Less helpful drag (inboard) could be eliminated. As for lightening stick forces, it wouldn't seem to matter (other than torsional stiffness maybe).

There must be a good reason this isn't common. My first thought is that it's not worth the trouble on most designs because the drag only occurs when ailerons are moved from the neutral position. Are there some negative effects I'm not thinking of?

Thanks,
Luke D.
EZ's have frise ailerons and no rudder is needed during turns as the ball stays pretty close to center. The other benefit, a biggie, is that the stick forces stay the same at any speed. I traded rides with a guy names Ty Ross and his Lancair 4 turbine. We were boogying along at over 300 MPH with me flying and I asked him if I could roll it. He said that we'd have to slow down first as the ailerons were just too stiff at this speed. He was right. The stick seemed almost unmovable at that speed. Slowing down to below 250 it did nice rolls with no rudder needed. Then we took my Long EZ up. He did a number of rolls from the back seat from 140 MPH up to 230 MPH and liked that the stick forces stayed the same at all speeds.
 

Dan Thomas

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Also, Cessnas do not employ Frise-type ailerons. As a miner reference:
That is a quote from a CFI, not an authoritative source. I have run into way too many instructors that have no clue about carb ice, leaning, accelerated stalls and AoA, engine and accessory principles, unusable fuel, and a lot of other stuff.

On this one he is completely wrong. Push up on any Cessna aileron and see the lower leading edge stick down below the wing. That's the definition of a Frise aileron, causing drag. Why would Cessna deliberately cause drag unless they wanted to counter adverse yaw?

Some folks think that a Frise has to have a nicely rounded leading edge. They get that from the pictures in the textbooks, but all we need is drag, and that Cessna aileron does it handily.
 
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flitzerpilot

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Regarding LukeD's quest for perhaps an idealised aileron design that incorporates an effective anti-adverse yaw device, I think what he may be describing was already designed by L.G. Frise in a later evolution of his patent, which was the Hartshorn Aileron (see attached diagram) described in David Luff's excellent book on the Bristol Bulldog fighter (Airlife 1987). This variation, in which the Frise section at the outer tip featured a rising leading edge inboard to the aileron root provided a progressive emergence of the aileron nose into the airflow when deflected TE upwards, instead of it emerging over the whole length of the aileron as on the standard Frise type. There were some negative aspects to the design under test, however, and as the standard Frise was less susceptible to rigging errors, it was not proceeded with.

The discussion here has gone into enormous detail on differential ailerons and their pros and cons: a Tiger Moth for example might just as well not have differentials given the amount of rudder necessary - a great training machine for all that and partly because of that.

Nowadays, starting with the newly introduced cantilever monoplanes from the late 1960's and '70's, initially thick-winged devices such as the Acrostar and Yak 55 and the later Sukhoi 26 and the later carbon fibre-reinforced designs with somewhat thinner sections, like the Extras, these all used symmetrical foils rigged at zero incidence and using ailerons, many of whose maximum thickness around fulcrum lifted the boundary layer and lightened the control. Blunt trailing edges were also introduced for better 'feel'. ' Bulged about fulcrum' ailerons were, I believe, pioneered by Schmued on the P-51 although one test pilot recently commented that the P-51's ailerons are heavy; at least compared with those of the Spitfire or the later Sea Fury with spring tab ailerons.

I utilised the above 'bulged' aileron design on my first biplane project, the Tigerfalk, and the 1/4 scale dynamic model of that had superb roll response according to the builder, the then World Champion R/C Scale modeller, Pete McDermott (Ca 1988), who coined the expression for it, "Stalls like a Pussycat: Snaps like a Pitts"! This featured a modified NACA 23012 airfoil with the upper and lower ordinates from 60% chord running as a straight lines to the TE. Thus the unmodified (original) aileron profile projected into the airflow. The wing chord itself was also reduced from the original profile by that mod.

The ultra-simple, by comparison, Flitzer uses two big, plain high-aspect ratio ailerons with low break-out forces and one test pilot claimed in the aviation press that its 'differential ailerons' were extremely effective - even though they are not differential and operate via 1:1 via pulley system using short runs with no measurable cable drag. Although aiming for simplicity, the later 4-aileron Stummelflitzers Z-1R and S are more complex, involving drag-compensating ailerons which combine mass-balances and spades. In this sense these have migrated towards the old Tigerfalk design, but unless one wants about 270 degrees of roll-rate, the basic sportsplane is ideal at 100+. The exception is the Z-2 Schwalbe which retains the 'square' wingtips of the early Flitzers, but because it has relatively broader chord wings and greater mass, it needed more aileron power to match the manoeuvrability of the original single-seaters.

There is no noticeable adverse yaw when flying the Z-1 or Z-21 and I agree with Billski that 1:2:3 perceived feedback in terms of aileron: elevator and rudder is perfect, although I was initially aiming for 1:2:4 as a recognised 'standard'. The lower profile, rounded fin and longer-chord rudder on some Flitzers was an attempt to achieve 1:2:4 but made little difference. It took all of 30 seconds on my first flight to appreciate the light rudder on the prototype in any case. The control harmony is favourably commented on by Bob Grimstead in his original Kitplanes article and later in PILOT when evaluating the Z-21's handling and aerobatic qualities.

In terms of muscle power and the ability to roll the a/c in either direction with ease, I am considering cranking the stick grip on the latest type, the Sz-1 (work name only) slightly to the left, so the back-handed roll to roll-stop (rolling right) is more comfortably achieved given the limitation of the human wrist (referencing BJC's comment).

I did design a 'hide-and-seek' mass-balance and spade for the SK26 biplane many years ago in which the balance arm was enclosed inside a 'wing pocket' when the aileron was neutral or TE down, but that's another story.

Also attached is a picture of Pete McDermott with the 1/4 Tigerfalk and the latest Flitzer evolution which may use the cranked stick grip.
 

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bhooper360

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Wing lift is usually distributed along the span in a nice elliptical shape. (...) [Go] half way out the wing and the local lift is dropping off. By the very tip there is no local lift at all. (...) That lowers how effective ailerons can be.

I was having trouble intuiting this. As you get to the tip, you're basically just controlling the intensity of the tip vortex, like, you're controlling how hard the toilet flushes, and it doesn't accomplish anything useful. But... once you deflect the flap (i.e. aileron), then you're also changing the amount of lift produced. So, it's not accurate to visualize it as a nice giant ellipse from the textbook, right? Because the wing at the tip is producing either much greater lift or much less, depending on the aileron deflection. So it's basically a separate ellipse with a different vertical axis. And in theory it could dwarf the other ellipse. So yes, there are tip losses, but it does not seem accurate to imply that the lift produced by the wing sans aileron is relevant in understanding the limit of aileron effectiveness.

Also, did my browser change or was there some kind of editor update? It erases my last newline when I press backspace.
 
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