flaperons: up or down?

[jsomers1234]

hi,

I am flying planes with ailerons. On my planes I have installed flaperons. When used they are in an upward position. If look to real planes, when landing they are in a downward position.

I'm doing it wrong or is there a difference between model and real planes? What happens if the flaperons are in a downward position on model planes. Are they as efficient as upward, does the plane react in the same manner?

Thanks for the advice,

Jan Somers.

[Mike Seale]

Full sized aircraft have flaps (inboard) and ailerons (outboard). Lowering the inboard flaps increases drag and reduces lift. It also has the effect of introducing washout so that the wing cannoit stall. If you only have outboard ailerons and want to use them as flapperons (most will call these spoilerons) you must raise them. Raising them increases drag, reduces lift and introduces washout, so the wing cannot stall. If you lower outboard ailerons you will get a very nasty tip stall.

If you see something like an F3B glider with flaps and ailerons you will see that they lower the inboard flaps and raise the ailerons for landing. This is called CROW braking, and makes these very slippery models easy to land.

Mike

[leccyflyer]

Originally posted by Mike Seale
Full sized aircraft have flaps (inboard) and ailerons (outboard). Lowering the inboard flaps increases drag and reduces lift. It also has the effect of introducing washout so that the wing cannoit stall.

Mike

Doesn't lowering the inboard flaps increase drag AND increase lift?

AFAIK the general concept that washout prevents stalling is that it doesn't so much prevent the stall as control where the stall occurs first, so that the higher angle of attack at the wing root promotes the stall to begin with the inboard section, thereby delaying the stall of the outboard section and prevented the "tip stall" and dropping of a wing, much feared by modellers everywhere.

Leading edge slats, slots and spoilers can produce the same control of where and when different sections of the wing reach their critical angle of attack relative to each other.

Brian

[Capt. Electron]

jsomers1234,

I realize this is conflicting information, but ....

Lowering inboard flaps increases lift and drag and lowers the stall speed. Small amounts, say up to 10 deg will add more lift than drag, over 10 deg will add more drag than lift. A lot of full size aircraft will use 10 deg or so of flap for take-off to benefit from the increased lift.

Adding washout will not prevent a wing from stalling. Only the pilot can do that. Washout merely determines which portion of the wing begins to stall first. The plane has more roll stability and control if the inboard section stalls first, and the tips are still flying for roll control. But adding washout decreases overall lift as the outer third of the wing is at a lower AOA. So flight performance throughout the envelope is decreased to gain some stability at the stall.

Flaps down on the outboard portion of the wing is bad. But you'll probably do OK till you make your first turn. If you're using flaps on the outboard section don't put them down until on final approach and you are lined up and level. Once on final approach ailerons are just used for wing leveling anyway, ground track is made good with the rudder.


Jimmy

[Mike Seale]

You're right, Brian. I am thinking from an R/C glider point of view where down flap (up to 90 degrees) for crow braking is creating huge amounts of drag, killing any lift in that part of the wing.

[steve lewin]

In my limited experience :

Ailerons down are called Flaperons
Ailerons up are called Spoilerons
(edited due to me orignally being so stupid I got them the wrong way round)

On a standard sports model with full span ailerons both work but are not quite the same.

Down (flap) creates more drag plus lift so slows the model right down but still keeps it flying. The planes I've tried them are also likely to balloon (bounce up) if you aren't quick enough adjusting the "trim". This is more like full size flaps which are at least partly aimed at providing enough lift so you can land at a reasonable speed.

Up (spoiler) creates drag and reduces lift so it's mainly useful for persuading floaters to drop out of the sky, hence the use in gliders which would otherwise keep going into the next county. Useful for spot landing contests too (provided you have strong landing gear ;)).

Steve

[leccyflyer]

Originally posted by steve lewin


Ailerons up are called Flaperons
Ailerons down are called Spoilerons


Steve

I think you might have typed that back to front- your description below makes more sense.

AFAIK since Flaps go down and Spoilers go up then Flaperons go down and Spolerons go up.

Brian

[jsomers1234]

Steve,

I hope you missed in the naming (= confusing)

objective = the same in both cases; less drag, loose altitude quickly for landing purposes

Ailerons up = flaps ==> used for glider (because ailerons are at the end of the wing, works as wash out, prevent stalling from the wing tips)
Ailerons down = spoilers ==> used for sport planes

Is this correct?

Jan:confused:

[leccyflyer]

This link might provide some food for thought on Spoilerons and Flaperons in sailplanes.

http://www.nesail.com/setslope.htm

Brian

[leccyflyer]

............and here's another article explaining some of the advantages and disadvantages of flaperons, specifically in terms of models.

http://www.mindspring.com/~cramskill/flaperon.htm

Brian

[BMatthews]

I didn't follow the links so this may have been covered in them but here goes anyway....

I made a 2 meter glider a few years back that had full span strip flaperons. I found that when these were angled down more than about 10 degrees the adverse yaw became quite bad. At 30 degrees is was all but impossible to turn any more. At 45 and over it would actually turn the opposite way and look like a drunken sailor while doing it.

I never played with raising the flaperons but I understand that raising them retains full control. The only thing is that you're dumping lift and adding drag rather than adding lift and drag. But our models, especially sailplane types, have way too much lift when it's time to land anyway.

And as the others said, if it's tip located flaperons or spoilerons you don't want to be lowering them anyway. That would create a very nasty tip stall condition.

[Sparky Paul]

Flaperons going up will increase the sink rate without doing too much to the pitch angle. Good for short steep landing approaches, or leaving that Buick-lifting thermal.
Flaperons down will also increase the sink rate, but with a pitch attitude change, AND the adverse yaw you've noticed. (Disorienting, isn't it? :) )
Splitting the surface into seperate flaps and ailerons to get the "crow" mode is most common. Ailerons up, flaps down.
And both surfaces can be linked to function as full-span ailerons, if you wish.

[steve lewin]

Apologies for the confusion. How was I to know that you were only going to read what I wrote instead of what I obviously
meant :( ?

I've fixed my original message.

Steve

[BMatthews]

Originally posted by steve lewin
...How was I to know that you were only going to read what I wrote instead of what I obviously
meant :( ? ......Steve

Yeah, I hate it when that happens.... :D

I'm looking at making a Speed 400 "warmliner" type glider. Since it's not going to be for contests I like the idea of using wing servos and coupling the throttle to them to act as spoilerons. This being for "normal" ailerons on the outer 30 to 40% of the wing panels. Sparky, if they truly don't have a lot of pitch effect then I'll be super happy.

I'm assuming that they will pitch down slightly but I gather from what you wrote it won't be a full on dive like with traditional high point spoilers?

Got ta git me som o' dose new fangled 5 or 6 channel FMA micro receivers....

[Mike Seale]

All of my gliders, from S400 warmliner to F5B have pitched up when outboard ailerons are raised as brakes. However, I always leave elevator at neutral for the first flight so that I can see how severe the pitching is. I then dial in a guesstimated amount of down elevator (usually between 15 and 25 percent) then adjust over the next few flights until applying the spoilers has no pitching effect.

BTW, if you set up the ailerons with differential (more up then down) you will need to programme in 'reverse differential' (more down than up) when the spoilers are fully deployed. If you don't do this, or if your tx can't do it, you will have very little roll control on finals. I put up with this scenario for 10 years with my FF7 and it's great now to be able to steer my models when I land.

Mike

[Jurgen Heilig]

Hi Mike,

I don't see a real need for "reverse differential". When the spoilerons are up, the model usually comes in "like on rails" anyway. Small corrections are usually still possible.

If you need more, all you need to do is move the "throttle-stick" (I hope you have the spoilerons on the throttle stick?!" while doing the correction. The effect is identical to "reverse differential".

All Graupner/JR MC-18, 20, 22 etc. Tx can be programmed that aileron will override spoilerons at any time, giving you full aileron control - with correct differential - at any spoiler setting.

:) Jürgen
http://people.freenet.de/slowfly

[Mike Seale]

As I said, I survived for 10 years without reverse differential, so kind of agree with you. However, there are times in competitions where I have been in a thermal and don't want to get out of it too early for fear of landing before time. Rsuilt is that you stay in lift for too long and then need to dump a lot of height quickly. This is possible in many ways but the easiest is with reverse differential where you can stick the spoilers up and still have full aileron control. Maybe the software that the MC18+ uses where aileron takes priority over spoilers is the same as reverse differential? Regardless, the p4000 that I use makes my planes a lot more controlable.

Mike