In my neverending quest for knowledge about bush plane design, I have started thinking a little harder about design considerations of the light-sport class of bush plane. Consider this thread.

In this class, we have the Rans S-7 Courier, the Just Highlander, the Kitfox Super Sport 7, and a few others. Of these, the Kitfox latest and greatest design still uses flaperons.

I'm not looking for a type comparison so much as I am an explanation of the flaps vs flaperons pros and cons. I admit I am partial to the conventional arrangement of control surfaces, but is this flaperon thing worthy? What full size bush planes employ them successfully?

The Savannah uses flaperons, and it is the only plane I've flown with this configuration, so take this as a small sample size.

The full length flaperons give the advantage that you can simultaneously have both very responsive ailerons and a lot of flap deployed. In the case of the Savannah, there is no washout in the wing, making it easier to construct. To get the inboard section of the wing to stall first, maintaining control, the flaperons are split into an outboard part and an inboard part. The inboard part has a bit of an offset downward, for more angle of attach, than the outboard part. This is simple and effective.

Not unique to flaperon design, but used on some slow flight planes like the Storch and the Savannah is the separation from the trailing edge of the flaperon. This helps keep the ailerons flying at slow speed since they are in less disturbed airflow.

When you see what the super cubs do with a more conventional design, I'm not convinced that all the flaperon and separated flow stuff makes all that much difference. Trouble is, I've never seen a really good, aggressive pilot in such a plane, so I'm not sure I've ever been able to see apple / apple comparison. I do believe that you get a margin of error in flying that may make the difference in a safe or sorry landing. As an old goat that got started late, I'm pretty happy with that.

tom

Zane-

Flaperons are used on the worlds safest (so they say) aircraft....the helio courier. The STOL capabilites of that aircraft are virtually unmatched.

I like that STOL CH 701..it has them as well.



http://webcache.googleusercontent.com/s ... ent=safari

The helio courier has a wielded steel frame around the cabin that is made to with stand about 14Gs, and the wings and gear are made to shear off in a crash, thus making it a very safe plane. that is also part of the reason why jaars uses them.

My Zenith 801 has them...It is a love/hate relationship.

With the flaps up you have full span ailerons so the roll control is outstanding.

With 10 degrees or so it creates a ton of lift and does not bother the roll control too bad.

At full flaps the angle of attack of the flaperons are as such that you gain alot of drag and very little roll control is left.. If the wind is dead calm full flaps can be exciting, and make for some spectacular short landing. If the wind is strong enough that you need accurate roll control to maintain a stabilized approach, full flaps will kill ya. or at least scare the shit out of ya.

Ben
www.haaspowerair.com.

Don't even get me started on full power/fullflaps take offs....

Zane,

The Kitfox not only has flaperons but it also has the "offset" flaperons. I built and owned a Kitfox 7 and like others have said, the full-length flaperons give excellent roll authority even at low speeds. As flaps they were effective and reduced the stall speed by about 6-7 mph while still moving independently for roll control. The earlier Kitfoxes had flaperons also but if you deployed them more than about 20 degrees it would bind up the aileron function which is obviously not a good thing.

I owned an early Kitfox and never deployed the flaperons as flaps... you didn't need to because it landed slow enough anyway. The slightest movement of them during cruise flight did function as an effective pitch trim though. The offset part of the Kitfox design is different than the others you mentioned but not unique. The Storch (arguably one of the best and most definitly the ugliest stol aircraft) and the Junkers bombers used the offset control surfaces also so that design is tried and true.

1 seventy Z asked:

I'm not looking for a type comparison so much as I am an explanation of the flaps vs flaperons pros and cons. I admit I am partial to the conventional arrangement of control surfaces, but is this flaperon thing worthy?

Kitfox Classic 4 builder and flyer here. In a word, I answer your question with yes, this flaperon thing is worthy. I then say that every airplane design is a compromise so it depends somewhat on what the person wants most.

Flaperons produce a much quicker roll rate than ailerons but when drooped too far with the flap handle the roll rate suffers.

They are very effective in cross wind landing.

Drooping them causes a nose down pitch in the kitfox. In the Kitfox models 1 through 4 they are used to trim the pitch.

They can be rigged with a few degrees of reflex in the down flap handle position. This position spills lift off the wing and can be used to lose altitude in a hurry when you want to.

When installed below the trailing edge of the wing...like a kitfox...flaperons do not suffer from flow separation when the wing stalls so roll control is maintained well into the stall.

Their primary purpose is to produce lift not drag. On my Kitfox 90% of the stall speed reduction is achieved with the flap handle about half way up. Beyond that they produce some drag but start to feedback into the ailerons and reduce the roll effectiveness.

The design is simple with few parts. There is only one control rod to connect to each wing which simplifies the wing folding process. I think this is one reason kitfox continues to use them.

Flaperons are used on the worlds safest (so they say) aircraft....the helio courier.

Really?...........one of my best friends has one..........no flaperons on it.

Hey Z
This may be a little petty larceny, not really being what you are asking, but when I was looking for a cheaper, lighter, backcountry plane, and still keep my 180, these were the 3 planes I liked the most.
My pick of the litter was the Rans s7,but fly one of the Kit Fox ss7 sometime. What a nice little plane. Won't land as slow as the others, but light, and will land plenty short for most. On the other side, a little faster with the same power. Really comfortable cabin and a solid feel on the controls. If it were me, I would probably put the earlier flaperons on it for quicker response, but a great plane.
FWIW Gary

Here's the biggest plane that I've ever seen with flaperons...........but I'm sure that there could be others out there.
I've got some pictures of it that I took two years ago, and some from this summer. It can carry a small pickup truck.


http://www.oldwings.nl/content/gafhawk/gafhawk.htm

What full size bush planes employ them successfully?

Twin Otter. I think they have a system that connects the ailerons and flaps together and operates them as one unit. I guess that qualifies as flaperons?

The Raven LSA uses full span frease type flaperons , it has a system that maintains full delection with full flap deployed and has diferential that counter acts
adverse yaw you can put your feet flat on the floor and roll in and out of a turn with the ball in the center .
It has a roll rate that would scare you untill you get used to it then it is nice even at very slow speed which makes it very responsive in a cross wind .
The lift it creates is huge and does not suffer from the stall/ reversal that a common flapperon has when deployed to far I can fly at 25 mph with aleron control
that is as effective as a conventional is at 60+ mph !

Hafast wrote:

Flaperons are used on the worlds safest (so they say) aircraft....the helio courier.

Really?...........one of my best friends has one..........no flaperons on it.

I don't think the Helio has flaperon either. Some have spoilers in addition to the ailerons.
I think the Twin Otter system described may be aileron rigged to droop with the flaps, like a Robertson STOL kit for a Cessna.

While we're discussing design, I have a question. My C150 has about the same wing area as a Pacer (about 160 sq feet) but uses tapered longer-span wings to get it- about 32-1/2 feet versus about 30 for the Pacer. The GlasStar has about the same wing area, uses a constant-chord wing like the Pacer but an even longer span (35' or so) to get it. Which is better, how, and why? I would think the shorter span the better for a quicker roll rate, and constant chord for ease of manufacture.

Hotrod150,
That is what they call aspect ratio ,the higher the aspect ratio the less drag which causes more lift .
If you took two planes identical and put a low aspect ratio wing on one and a high on the other then
take off together( the low would get off the ground first ) and as you gained alt the high would soon
pass the the low then when the low reaches service ceiling the high would continue to climb to a higher
alt . Howerver, the low aspect ratio is safer at low speeds as the high aspect ratio is more easily stalled, well hell its like a hawk and a falcon
the hawk with it,s short fat wings flys low and dodges in and out of the trees ect... ( super cub )and the falcon
with its long skinny wings uses alt and speed ( cessna ) Ha !

Gary,

The 170 is as good as gone (fingers crossed) and I will be building one of these within the next 2 years. I like the feel of the Rans S7 but the limited baggage is kind of a downer. The increased baggage/cargo of the SS7 and the Highlander appeals to me.

If I had a 180 I would prob find a way to keep it, but the 170, as much as I love it, just can't fill my mission anymore due to its certified nature.

So how much shorter were you able to land with the S7 vs the SS7?

Z

shortfielder wrote:Hey Z
This may be a little petty larceny, not really being what you are asking, but when I was looking for a cheaper, lighter, backcountry plane, and still keep my 180, these were the 3 planes I liked the most.
My pick of the litter was the Rans s7,but fly one of the Kit Fox ss7 sometime. What a nice little plane. Won't land as slow as the others, but light, and will land plenty short for most. On the other side, a little faster with the same power. Really comfortable cabin and a solid feel on the controls. If it were me, I would probably put the earlier flaperons on it for quicker response, but a great plane.
FWIW Gary

Z
In this market, you could probably buy a nice 170B w.180hp and csp prop for less than what it would cost to build a kit, get in and ot of most anywhere you wanna go, and carry wife kids and camping gear when ya want. And spend that couple years flyin, instead of in the shop.
You can make the baggage area quite a bit bigger in the Rans s7 and add extended fuel. If ya want the kit plane.
Watchin Emmet and Tom really makes them look good. I'd like to have one, and keep Ol Buzzard Bait.

I missed one of your questions
And I've told ya before how much I like the later 170's with the bigger engines.
I didn't fly the Kit Fox and the Rans under the same conditions, so, hard to make a scientific/solid comparison, but just knowing that the Rans is lighter, and flies slower, only makes sense that it would land and take of significantly shorter.

Z
You could probably go down to Homedale and compare them all right there. The Raven looks kinda interesting, but I couldn't find much info on it.

I just jeep asking myself what would allow me to land on those crazy Ohio Bush Planes airstrips and still make it to Johnson Creek.