Full span flaps and separate full Span ailerons?

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addaon

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You’ll probably need to say a bit more about the geometry you’re imagining, since it’s not clear how this would be arranged. Split flaps of less-than-usual chord? Simple flaps with hinged TE? Something else?
 

Vigilant1

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Has anyone done this ? Even thought about it ?
What's the objective? It's going to be considerably more complex and heavier than regular flaperons and have all the same drawbacks (flaps outboard where they are less effective and increase risk of tip stall, ailerons inboard where they are comparatively less effective at producing roll).
 

Tiger Tim

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Seems like pretty low hanging fruit to just think of. What would they accomplish and how would they work?

Would it be flaps where the trailing edge was hinged and moved differentially? That seems like it would have all the drawbacks of flaperons while also being heavier, more complex, and having a really messed up zigzag airfoil when the flap is down and aileron up.

Would it be full span ailerons with a split flap on the lower surface ahead of them? That would sort of be the inverse of full span flaps with roll spoilers. I don’t know of any airplanes that do that along the whole span but IIRC the P-26 had split flaps that partially overlapped the inboard end of the ailerons. Since it was from a time when NACA was hungry for reports on just about anything there might be some literature out there on what a leading split flap does to an aileron.
 

Pilot-34

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Lol you guys are asking me how do do it?

The reason I asked is I didn’t have a clue how !
I’ve given it some thought and there seems like a few obvious ways to go about it

Full span flaps attached to the wing and ailerons either above or below either full span or partial .
The vice versa
For Full span ailerons attached to the wing and flaps above or below either full span or partial.
Full span flaps either above or below the wing and ailerons attached in the opposite position above or below.

What I’m thinking is flapperons but separated for better performance
 

Victor Bravo

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I have owned two aircraft that have this feature. When done right, it's absolute magic. Done right is the Schleicher AS-W20 sailplane, which has not only full-span flaps and full span ailerons... but also a "crow" configuration with the flaps at 40 degrees and the ailerons reflexed upward to -6 degrees. This gives you incredible safety, maneuverability, and control at very low speeds. It requires a rather complex, but fully mechanical control mixer. It was a production aircraft, with about 1000 of them made. I was lucky enough to have owned and flown two different ones, an "A" and a "BL".

Done wrong, this could be attempted using almost the same hardware that deHavilland uses for their multi-element flaps... but using the hardware in a different way. Each full-span flap would have two sections, like a DH system. But the rear section of the flap would also be used as an aileron. It's certainly possible, but would come with a lot of baggage and head-scratching. Adverse yaw and control reversal would severely limit the benefits. The engineering and parts count and mixing linkages and flutter analysis would be a nightmare.

If someone wanted to build a new take on a high-performance STOL / bush aircraft, I guarantee that adapting the Schleicher sailplane control system for this use would make a huge increase in flight safety in ultra-high demand, real-world, extreme situations... the guys landing Super Cubs in gusty canyons, mountaintops,400 foot clearings with trees on both ends, etc.
 
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Riggerrob

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Dear Victor Bravo,
Are you referring to the double-hinged rudders that deHavilland of Canada installed on DHC-4 Cariboo and DHC-5 Buffalos? I suspect that DHC learned how to build double-hinged rudders when they built a batch of Grumman Trackers for the Royal Canadian navy (1950s). Grumman designed double-hinged rudders to fit inside cramped hangars onboard ships.
Then DHC adapted double-hinged rudders to smooth airflow during low-speed, STOL approaches.
 

Riggerrob

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What about Lamm ailerons?
They have full-span flaps, but the ailerons are only about a quarter of the span and they are essentially only the top skin of the outboard flaps. The trick is that Lamm ailerons are differential ailerons that only deploy upwards. Differential activation helps reduce adverse yaw.
 

AJLiberatore

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What about Lamm ailerons?
They have full-span flaps, but the ailerons are only about a quarter of the span and they are essentially only the top skin of the outboard flaps. The trick is that Lamm ailerons are differential ailerons that only deploy upwards. Differential activation helps reduce adverse yaw.
Your Reading my mind Rob,

I don't know what the status is of the patent and if anyone has ever enquired for a "one-off" license for their homebuilt. I've doodled a bunch of wing configs with them. If they truly do what they say, then add full span flaps combined with wingtip and airfoil advances that we have now, how can this not be a good thing.
 

Vigilant1

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Putting flaps all the way out to the tip may, on paper, give a greater max "whole wing" CL with flaps deployed.

From a practical aspect, the last few degrees of AoA are a lot more "useable" if we know our wing won't first stall at the tips. So, we may end up with a higher max practical CL by not having flaps all the way out to the tips.
 

Riggerrob

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Putting flaps all the way out to the tip may, on paper, give a greater max "whole wing" CL with flaps deployed.

From a practical aspect, the last few degrees of AoA are a lot more "useable" if we know our wing won't first stall at the tips. So, we may end up with a higher max practical CL by not having flaps all the way out to the tips.
To delay tip stall, the old method was to gradually twist the wing so that the tip operates at a shallower angle of attack.

Since NASA's work during the 1970s, the modern method is to install leading edge cuffs outboard (see Cirrus and Quest Kodiak). This serves two functions. First, the cuffs have larger leading edge radii.
Secondly, the dis-continuity generates a vortex that acts similar to a fence to delay root stall turbulence from migrating out to the ailerons.
 

Victor Bravo

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Putting flaps all the way out to the tip may, on paper, give a greater max "whole wing" CL with flaps deployed.

From a practical aspect, the last few degrees of AoA are a lot more "useable" if we know our wing won't first stall at the tips. So, we may end up with a higher max practical CL by not having flaps all the way out to the tips

Most of the current generation high performance gliders have the wing control surfaces terminate a fair distance inboard of the tip for this reason.
 

wsimpso1

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Has anyone done this ? Even thought about it ?
Nominally, we have to split up the trailing edge for flaps and ailerons. Smart way is flaps inboard, ailerons outboard, which tends to prevent tip stalls and obtain much more roll authority than with them reversed.

We can make ailerons that also droop to give flap function, and then they are called flaperons, and they have been done part span and full span. Many sailplanes, some light planes, and Kitfox does this with a Junkers flaperon.

Some folks have designed control surfaces that swivel for normal function and also open like split flaps, and they are typically used to increase cd almost as much as to increase cl. Space Shuttle rudder is an example. F-16, Fokker 100 and others have clam shell dive brakes too.

Billski
 

Bille Floyd

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Has anyone done this ? Even thought about it ?

Yes -- on RC airplanes .
Full span flapperons , on several airplanes ; they do not
add twist , for low speed stability, but they do make the airplane
fly slower. When full span flaps stall ; it's Violent (.)

Bille
 
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