Who here has experience with installing and piloting drooping ailerons / flaperons?

- I am looking for knowledge about how the install works in STOL kits available on the market, the mechanics inside the wing. Photos would be pure gold.

- I am also specifically interested to know whether the roll control forces increase with drooped ailerons deployed, and if there's no change in control forces - how do they achieve that....?

Any information on the above would be hugely appreciated!


P.S. I am not looking for another debate on the much mooted pros and cons of drooping ailerons and flaperons.
I want to land slower, and I am prepared to accept a bunch of other cons to get that pro, even if it doesn't appear to stack up to the outside observer.
In the Bearhawk, with its large constant chord wing, drooping ailerons are proven to shave 3kts off the stall, which theoretically means up to 15% shorter landing and take-off roll.

I flew both the Callair A9A which had no flaps and regular ailerons and the A9B Quail which had drooping ailerons. The drooping ailerons, like normal flaps, decreased stall speed and decreased landing distance. They also helped with getting off short with a full load.

The main thing I liked about drooping the ailerons one notch, in the crop field, was that they leveled the airplane. This helped with visibility. All spray planes fly nose up a bit, with a full load, to prevent descent. CG is to the front of the envelope when loaded. A lot of trim is used to help hold the nose up. Ground effect also helps. The Pawnee doesn't have enough flap to be worth the bother. Flying level, even though a bit slower, also made the airplane respond to all controls better. I kept a notch of droop until about half the load was gone. I used full droop on all landings.

Good visibility, when flying low, is a major safety issue. I also cushioned up until my helmet almost touched the cross tube in the top of the cockpit. There are lots of things out there to miss.

The problem with drooping ailerons for STOL operations is that they work great right up until the moment they cause a big safety problem.

Because a STOL airplane will be operating in real-world gusty and maneuvering conditions... make damn sure you are considering the real-world, low, turning, gusty, tip-stalling realities as much or more than you are considering the wind tunnel, calm weather, sales brochure benefits.

I would STRONGLY recommend pairing the drooperons with VG's. This is a quick 'n' dirty band-air fix, but it will keep the air stuck to the wing at times when the combination of flap deployment, aileron input, and a gust all get together and conspire to make you lose a wingtip turning final into a short dangerous strip.

EZFlap wrote:The problem with drooping ailerons for STOL operations is that they work great right up until the moment they cause a big safety problem.

Because a STOL airplane will be operating in real-world gusty and maneuvering conditions... make damn sure you are considering the real-world, low, turning, gusty, tip-stalling realities as much or more than you are considering the wind tunnel, calm weather, sales brochure benefits.

Like I said right up front, no need to discuss the choice to install them (pros and cons). I want to know about how it's done.

JB,

The one thing you'll want to do with this mod is build it so you can enable/disable the drooping ailerons. I know of one plane configured this way, but I don't personally know the builder. I'll ask around and see what I can find out. In the meantime you ought to look into replacing your existing flaps with Doug Keller Double Slotted Fowler flaps. He can build them to your flap specs.
http://www.performancestol.com/
Best to call, not email.

I'm not an aircraft designer/modifier but according to John Boyd KISS is a principal of of aircraft design/modification as well as a principal of war.

Flew a RSTOL C206 a little bit. Amazing slow handling characteristics. There was a slight roll penalty but the ailerons on a 206 can overcome most of it. I wouldn't hesitate a bit, at least on that airframe.

The long and the short of it...

I am going to go out on a limb and assume your aileron control cable is a looped system. You will lengthen that loop system to be able to accept a pulley that will be controlled by the flap actuator, and a pulley (spring loaded or otherwise) to take up the slack when the flaps are not actuated. When you actuate the flaps the new pulley will bring down the ailerons, when you release the flaps the other pulley will take up the slack. On an experimental, without a mixer, it is a reasonably easy mod. It gets a tad more complicated if you want the ability to adjust the amount of droop on the fly, but it is not an inordinate amount of added complexity.

Actual control forces shouldn't be measurably changed because the droop doesn't change aileron size nor max deflection, but because you've added a bit extra cable and another pulley / turn or two, some extra cable drag may be there. You're not getting to move the flaps with the ailerons, like a flaperon, you're just altering the aileron location when you add flaps.
Roll rate on the other hand will be somewhat reduced when flaps are selected, because you aren't getting to change the max deflection. How much obviously depends on how much droop you intend to induce, and whether or not you intend to add any other tricks to the mix at the same time. Designed with a little fore thought and flown accordingly it should be an absolute non event. After all MANY standard A/W aircraft are certified this way from the get-go.

I would add them, or do them again on almost everything I fly or have flown that had them, and that includes a reasonably wide cross section of aircraft

Take care, Rob

Barnstormer wrote:JB,

The one thing you'll want to do with this mod is build it so you can enable/disable the drooping ailerons. I know of one plane configured this way, but I don't personally know the builder. I'll ask around and see what I can find out. In the meantime you ought to look into replacing your existing flaps with Doug Keller Double Slotted Fowler flaps. He can build them to your flap specs.
http://www.performancestol.com/
Best to call, not email.

Very intriguing suggestion Phil. Not sure whether they would fit a Bearhawk, but I would like to find out... His website has quite a few broken links, so not much help there.

Rob wrote:The long and the short of it...

I am going to go out on a limb and assume your aileron control cable is a looped system. You will lengthen that loop system to be able to accept a pulley that will be controlled by the flap actuator, and a pulley (spring loaded or otherwise) to take up the slack when the flaps are not actuated. When you actuate the flaps the new pulley will bring down the ailerons, when you release the flaps the other pulley will take up the slack. On an experimental, without a mixer, it is a reasonably easy mod. It gets a tad more complicated if you want the ability to reduce the ability to adjust the amount of droop on the fly, but it is not an inordinate amount of added complexity.

Actual control forces shouldn't be measurably changed because the droop doesn't change aileron size nor max deflection, but because you've added a bit extra cable and another pulley / turn or two, some extra cable drag may be there. You're not getting to move the flaps with the ailerons, like a flaperon, you're just altering the aileron location when you add flaps.
Roll rate on the other hand will be somewhat reduced when flaps are selected, because you aren't getting to change the max deflection. How much obviously depends on how much droop you intend to induce, and whether or not you intend to add any other tricks to the mix at the same time. Designed with a little fore thought and flown accordingly it should be an absolute non event. After all MANY standard A/W aircraft are certified this way from the get-go.

I would add them, or do them again on almost everything I fly or have flown that had them, and that includes a reasonably wide cross section of aircraft

Take care, Rob

Thanks Rob,

Do you have a photo of this kind of arrangement? It sounds like it could be done to a Bearhawk.

PM sent

I have several thousand hours in aircraft with ailerons that droop (deHavilland aircraft and Cessnas with RSTOL mostly).

I for one love these systems. They make a good STOL airplane an even better one.

Rob is correct that aileron forces don't change as ailerons droop.

The only down sides I've experienced with these systems are a slight reduction in roll authority with ailerons drooped, and a slight increase in weight and complexity.

The deHavilland system is quite straightforward, and is pretty much as Rob described. With that system, the more you deflect the flaps, the more the ailerons droop, if I recall properly.

The RSTOL systems, on the other hand, operate somewhat differently. In these systems, the first three notches of flap (10, 20, and 30 degrees) each increase aileron deflection incrementally. Maximum aileron deflection is achieved at 30 degree flap setting. When the pilot selects full (40 degrees) flaps, the ailerons actually retract several degrees.

I'm sure this was a certification issue. But it complicates the mechanism a bit.

Also, the RSTOL system requires the addition of something like seven pounds plus I'd lead balance weights in each aileron. They actually removed the aft rivets in the ailerons and attached the additional weights, then riveted them again. This was to preclude a flutter event, presumably. If you decide to go this route, I would strongly suggest that you consult someone who's knows this business before leaping into it......aerodynamic flutter is not something you want to experience.

Wayne Mackey, the creator of the SQ-2 aircraft design had drooping ailerons installed on his airplane, controlled independently from the flaps. Might get a little busy, but could be a lot simpler to install.

MTV

Thanks for the information Mike, I appreciate that.

mtv wrote:Wayne Mackey, the creator of the SQ-2 aircraft design had drooping ailerons installed on his airplane, controlled independently from the flaps. Might get a little busy, but could be a lot simpler to install.

MTV

There is a Bearhawk using this design already, which is where I got the performance numbers from.

I only have experience piloting a Cessna 185 with the R-STOL. In the hangar, moving the yoke through roll inputs, you can definitely feel the higher stiffness in the controls as a result of the rigging complexity. Furthermore, you cannot move the ailerons up and down externally by pushing on the actual control surface due to this friction. However, in flight, I do not notice it in roll whether the flaps are extended or retracted. As the airplane slows, the control forces naturally lighten up so that when the flaps and ailerons are drooped, the forces are not significantly different from non-dropped wings. I do notice a significant flap deployment force and the flap extension speeds on the cessna are reduced from stock wings. I really like to slow the plane up before extending flaps for this reason.

Squash wrote: Furthermore, you cannot move the ailerons up and down externally by pushing on the actual control surface due to this friction.

Don't want to veer to far from the topic, nor sound critical of your airplane, but I have only met a few mechanics (2) who have actually taken the time to educate themselves on how to correctly rig an RSTOL system. Most probably just don't service enough of these birds to mess with it, but it isn't the same game as standard Cessna rigging.
What you are describing is incorrect, and would be worth addressing. I have flown several Cessna 1 series, and 2 series RSTOLs and have yet to fly one that you couldn't move the control surfaces on. The ones on my 180 will flap around in a breeze if you allow them to.

Take care, Rob

Rob wrote:

Squash wrote: Furthermore, you cannot move the ailerons up and down externally by pushing on the actual control surface due to this friction.

Don't want to veer to far from the topic, nor sound critical of your airplane, but I have only met a few mechanics (2) who have actually taken the time to educate themselves on how to correctly rig an RSTOL system. Most probably just don't service enough of these birds to mess with it, but it isn't the same game as standard Cessna rigging.
What you are describing is incorrect, and would be worth addressing. I have flown several Cessna 1 series, and 2 series RSTOLs and have yet to fly one that you couldn't move the control surfaces on. The ones on my 180 will flap around in a breeze if you allow them to.

Take care, Rob

d

Squash,

What Rob said. Those cable tensions are set too tight. Controls should move freely from inside or out. That much tension is not good.

MTV

Battson wrote:Who here has experience with installing and piloting drooping ailerons / flaperons?

- I am looking for knowledge about how the install works in STOL kits available on the market, the mechanics inside the wing. Photos would be pure gold.

- I am also specifically interested to know whether the roll control forces increase with drooped ailerons deployed, and if there's no change in control forces - how do they achieve that....?

Any information on the above would be hugely appreciated!


P.S. I am not looking for another debate on the much mooted pros and cons of drooping ailerons and flaperons.
I want to land slower, and I am prepared to accept a bunch of other cons to get that pro, even if it doesn't appear to stack up to the outside observer.
In the Bearhawk, with its large constant chord wing, drooping ailerons are proven to shave 3kts off the stall, which theoretically means up to 15% shorter landing and take-off roll.

There is an L-5 Stinson at the air museum in Ankeny, IA and it has been modified to lower the ailerons with a crank you would find in a pacer. They were doing an annual on the plane when I saw it and the aileron were drooped more than normal so I inquired about why the ailerons were drooping. Come to find out that the plane was in Japan and they modified it over there. Below is the website.

http://iowaaviationheritagemuseum.webs.com/

mtv wrote:

Rob wrote:

Squash wrote: Furthermore, you cannot move the ailerons up and down externally by pushing on the actual control surface due to this friction.

Don't want to veer to far from the topic, nor sound critical of your airplane, but I have only met a few mechanics (2) who have actually taken the time to educate themselves on how to correctly rig an RSTOL system. Most probably just don't service enough of these birds to mess with it, but it isn't the same game as standard Cessna rigging.
What you are describing is incorrect, and would be worth addressing. I have flown several Cessna 1 series, and 2 series RSTOLs and have yet to fly one that you couldn't move the control surfaces on. The ones on my 180 will flap around in a breeze if you allow them to.

Take care, Rob

d

Squash,

What Rob said. Those cable tensions are set too tight. Controls should move freely from inside or out. That much tension is not good.

MTV

The book calls for a tension of 30 +/- 10 lbs. I will have my mechanic look at it, but we re-rigged the system a couple years back now and the tensions were correct. Controls move freely and easily from inside and I can move the controls externally by pushing on the control surfaces but it certainly isn't frictionless, and I fear damaging a skin by pushing on them so I don't. I will investigate.

Quickdraw1 wrote: There is an L-5 Stinson at the air museum in Ankeny, IA and it has been modified to lower the ailerons with a crank you would find in a pacer. .........

I believe some of the later versions of the L5 were factory equipped with drooping aileron systems, deployed separately from the ailerons.

http://www.airbum.com/pireps/PirepStinsonL-5.html

As far as the mechanics inside the wings, and how this will affect the control forces and cable tensions.....

Although this will surely not be the easiest way, by far the best possible way to accomplish all of the things the OP is trying to do will require replacing some or perhaps all of the tensioned control cables with non-tensioned push-pull rods with spherical bearings.

ONLY THEN will you be able to use a "mixer" that has the same low control actuation forces and "breakout" forces at all flap/droop/roll settings. Using the (proven and well engineered) mechanical mixing systems that were developed for a completely different category of aircraft will still make a HUGE difference in what you are able to achieve in the field with your STOL aircraft.

I do not have any flight time in back country powered aircraft (R/STOL, DeHavilland, etc.) using drooped ailerons. So I don't know how bad or fatiguing or unbalanced those cable based systems are.

But I do have a fair amount of hours in aircraft that have extensive and well-designed control mixing inside the wing, using push-pull rods and mechanical mixer units, and I can speak from solid experience about how good those systems are. I've used them on numerous 6-8 hour flights, where the aircraft was never in stable trimmed cruise flight, and where continuous full-time usage of those mixers were required throughout the full flight envelope, all the way to a forced off-airport landing..

My point is not to directly compare my own strange experience with others here... my point is simply to say that

1) if you want to experiment with and develop control mixing, camber changing, etc. it can be done;
2) it DOES make a huge difference if done correctly, and will increase both STOL performance and safety at the same time;
3) the best way to execute this mixing mechanically has already been designed, engineered, and demonstrated in another category of aircraft;
4) by using what has already been done as a start point... and mild re-engineering to handle the different loads and speeds on your Bearhawk... you will likely be able to do better than previous STOL powerplane modifications that were designed to use the tensioned cable system.

The system you should be looking to adapt to your Bearhawk is the control mixing system in the Schleicher AS-W20 competition sailplane. It is a completely different application, for sure. But I will bet you a steak dinner and a bottle of single malt Scotch that it will make a spectacular difference in the capabilities and low-speed safety of your Bearhawk.