Flaperons: Up or Down?

[wannabe]

I have been told that for the purpose of slowing a plane for landing, on wings with strip ailerons (ailerons that exttend the full legnth of the wing) it is better to set the flaps to tilt up (above the wing) instead of down. Supposedly, strip ailerons that go down (flaperons), can take away any effect of washout and cause instabilty.

I understand the concept, but will flaps that go up slow a plane the same as down flaps and how will the wing react?

Anyone heard of this?

[wannabe]

I have been told that for the purpose of slowing a plane for landing, on wings with strip ailerons (ailerons that exttend the full legnth of the wing) it is better to set the flaps to tilt up (above the wing) instead of down. Supposedly, strip ailerons that go down (flaperons), can take away any effect of washout and cause instabilty.

I understand the concept, but will flaps that go up slow a plane the same as down flaps and how will the wing react?

Anyone heard of this?

[wannabe]

I have been told that for the purpose of slowing a plane for landing, on wings with strip ailerons (ailerons that exttend the full legnth of the wing) it is better to set the flaps to tilt up (above the wing) instead of down. Supposedly, strip ailerons that go down (flaperons), can take away any effect of washout and cause instabilty.

I understand the concept, but will flaps that go up slow a plane the same as down flaps and how will the wing react?

Anyone heard of this?

[wannabe]

I have been told that for the purpose of slowing a plane for landing, on wings with strip ailerons (ailerons that exttend the full legnth of the wing) it is better to set the flaps to tilt up (above the wing) instead of down. Supposedly, strip ailerons that go down (flaperons), can take away any effect of washout and cause instabilty.

I understand the concept, but will flaps that go up slow a plane the same as down flaps and how will the wing react?

Anyone heard of this?

[sukhoi26mx]

Some guys are using signifigant amount of reflex to increase the stability of their 3d planes while flying harriers. The idea is that at the signifigant angles of attack 45 degrees + the ailerons are still effective helping to minimize wing rock and it does seem to make a big difference.

Adding reflex for landing on a regular plane will increase the pitch attitude at touchdown but will not help slow the plane to a slower approach speed in the normal angle of attack realm (i.e. not harriering).

Scott

[SchiessCo]

If you have full span ailerons you can try flaperons (down) or spoilerons (up). Flaperons create some lift, and drag. Spoilerons reduce lift and create drag (that’s the super simplified explanation). Both may work for you.

I’d program your airplane for flaperon and test them at altitude. Then program the spoileron, take it to altitude and test them. Then, use whatever method you prefer.

Pete

[reills]

I have a Pique-3 that I modified with strip ailerons (wider at the root, narrower at the tip). My experience has been that strip flaperons just did not work. The plane became real squirrely when flaps were deployed. Aileron performance suffered as well. Just my 1 1/2 cents.

[DeuceTrinal]

I have used both successfully on my 60" 30% chord full span ailerons on my DLG's. Flaps tend to slow down, and create more lift. Spoilers drop you out of the sky much faster, while not slowing a plane much (at least with this big of spoilerons), and are veRY effective at "spoiling" the lift. I can drop my plane fast enough to break it easily if I'm not careful. Flaps just slow it down nicely, and with correct elevator compensation, it stays nice and level.

Try both and use whichever suits your plane best.

[wannabe]

Scott,

Could you clarify a couple of things?

Is reflex the inverse of a normal (down) flap action?

I assume harriering is a stunt manuver of some sort. I am guessing it is something close to a torque roll?

As far as the angle of attack for landing, woudl programming some sort of elevator reaction (down slightly??) help?

This is my first computer radio. I think I can do that.....

[wannabe]

Originally posted by fok
I’d program your airplane for flaperon and test them at altitude. Then program the spoileron......


Hmmmmm. I wonder if my Eclipes 7 will do that. I just got it. Maby it is a negative % setting for the flaps....I will have to look.

[sukhoi26mx]

You bet.

Harrier is forward flight but with extremely high pitch attitudes (in excess of 45 degrees).

Reflex is symmetrical up deflection of the ailerons.

I would not suggest any reflex for any typical sport models during normal landings. What you are doing in effect is reducing the lift created by the wing (spoilerons for all practical purposes). This means that to create the same amount of lift it will require a higher angle of attack (higher pitch attitude) in the flare.

If you are concerned with landing speed in your average sport plane you will want to have your ailerons deflect slightly down (10-15 degrees) and this will require a slight mix of up elevator to compensate... In most planes the effective decrease in washout is minimal and does not have much effect on the flying characteristics of the plane.

Scott

[Dereck]

Hi Wannabe
Try this - dead simple, but works for most models.

Get a little height, back off the power so the model slows, then put in some up trim. This lifts the model's nose some, causing a slight increase in lift and somewhat more drag. What you are aiming for is a combination of up trim and power that will allow the model to cruise at a slower than normal speed while still maintaining good control.

Clever bit - to come down, reduce power and the model should, if it's halfway decently designed, start a steady descent at pretty much the same attitude as it flew level. To stop the descent, restore the power. If you go to too much power, the up trim starts to do what it does so well, and the model will initially climb, then climb steeply if you persist to full power.

So, you're cruising along downwind at your new-found "pattern speed". Start to turn into the runway to land, back off some power and she'll ride on down. Keep the bank angle about 25 deg or less, so it doesn't have a large effect on overall lift.

Eventually, given enough practice, you'll slow up and trim back simultaneously to position on the downwind leg, roll into the final turn, back off some more power and after a 180 turn, arrive just short of the runway threshold and just high enough to reduce power some more, add a little more up - by stick, not trim - and fly her to the stall just as the wheels take over from the wings.

Far less fuss than trimming the ailerons for most models.

Ancient English flying saying - "Practice landings plenty - they are the only compulsory maneuvre in aviation"

Regards

Dereck

[temp_oct]

?
I'm curious about the same thing too.
Last time I flew on a jet (737), the flaps were down (below the wing) during both take off and landing.
It is suppose to be the same for model airplane?

[DeuceTrinal]

Yup, just reverse the negative or plus, and you have the opposite

[jgmtens]

Flaps and flaperons on RC airplanes and 737s are designed to go down thereby increasing the camber of the wing so it can produce the same amount of lift at a slower speed.

They should only be down for landing though - flaps are up during normal flight and flaperons should be neutral (just like ailerons) during normal flight. Flaps are also used on heavy jets for takeoff to shorten the takeoff roll.

Jon

[Dorme]

My 2 cents......Flaperons will work as long as you don't need ailerons in landing. They can create a situation, esp. in windy conditions that won't allow you to correct your lateral attitude until it is too late. Use flaps separately. Flaps are traditionally used as a method of landing at a steeper angle while maintaining a forward speed above stall. They generally increase the stall a few MPH.
Spoilerons are used for destroying the lift produced on the wings. This is very helpful for gliders that get caught in thermals and need to get out of them without damage to the wing(can't use the elevator here-too much stress). In a glider this is useful, as well as, making a spot landing due to the ground effect that can keep a glider going the whole length of the runway.

In general, I would use flaps on take off for my Storch to get a high lift angle(almost vertical briefly) and use them to come in for a higher approach. This all needs to be used in scale fashion. That is to say, horsing the plane off the ground early and landing at a higher speed than necessary won't utilize the flaps effectively. The heavier planes can use the flaps and may in some cases need them for the fields they fly in.

I rarely use spoilerons on my gliders, but when I do, it is only alittle as they are very effective. I neutralize them shortly after itilial use. I hope this helps.

[Bsmooth]

just n fyi, flaps that go "up" are called spoilers, but depenting on where they are in relation to the MAC (Mean Aerodynamic Chord) can effect the way the airplane reacts to the flap deflection. Spoilers placed on the MAC are effective at "killing" lift in the area behind the raised portion


kinda like this :
http://www.rcgroups.com/forums/showthread.php?s=&threadid=167050&highlight=spoilers

if the spoiler is set at the trailing edge of the wing, it will cause (for the most part) the plane to nose up into a higher angle of attack and slow down some.

when flaps are deployed downward it is intended to increase lift but not necessarily slow the plane down, spoilers kill lift and can provide a precise landing path, but again don't slow the plane down. competition Saiplanes have something that is called CROW or BUTTERFLY mixing, this is when spoilers (on the trailing edge) are on the outside pannel of the wing and flaps are deployed on the inboard part of the wing. This functions as a lift booster and an air brake slowing the plane down and increasing the sink rate

http://rcgroups.com/gallery/showphoto.php?photo=3811&password=&sort=1&cat=998&page=1

[sukhoi26mx]

Dereck,
Good techniques... used all the time in full scale as well. The only one that I don't do is trim using the trim buttons on the TX to compensate for the slower speed in the landing pattern. I find that once I have the plane trimmed I leave it be... and carry any load with my thumb. I do this primarily so that the plane is always in trim for the next flight and if I have to go around on the approach it is in trim for the go... rather than having a large pitch up due to the up trim from final. I would agree that there are very few sport models that have approach speeds that require any drag or extra lift devices.

Scott

[sukhoi26mx]

Originally posted by jgmtens
Flaps and flaperons on RC airplanes and 737s are designed to go down thereby increasing the camber of the wing so it can produce the same amount of lift at a slower speed.

Jon

Not only do they change the camber of the wing but on modern jets they also signifigantly increase the wing area (up to a 50 percent increase on some jets). In addition they signifigantly increase the drag on the plane beyond approximately 20 degrees (30-40 degrees landing flaps settings are common). This is very useful in a jet because to maintain a constant rate of descent (approx 700-800 fpm) the engines will have to be spooled and this aids go around engine response (i.e. more immediate thrust on go around).

Scott

[Marion]

Flaps UP will make the plane try to go down. That makes you pull the nose up, and that in turn slows the plane nicely. I set mine for flaps UP, and it works great for me

[wannabe]

I appreciate the info guys! Derrick, since I have taught myself to fly models ofer the past 3 months, your explanation of landing brings some things onto focus for me.

While I do as many touch and goes as I can, my landings are still a bit of a pucker. I'm sure there will always be a little of that.

The plane I am learning on is not exactly a typical "park flyer" It is a 44" span, semi-symetrical wing, just over 2lbs. Plenty of power. It stalls at 21mph. It is capable of many aerobatics.

I just got a computer radio and I wanted to try the flaperons as much out of curiosity as out of need. There is something very scale like about a high wing comming in on full flaps. Just floating....

[wannabe]

here is the plane

[lrsudog]

It depends on too many factors to give a yes or no answer. If you have plenty of power and the wing tips are not extra critical, Some flaps mixed in for landing are not a problem at all. Especially if you have aileron differential. No matter what though, you do not want to have the flaps setting using up more then half of your aileron travel.



It also depends on how good a pilot one is.

[DeaninMilwaukee]

I'm using flaperons and spoilerons in my jk aerotech big T. Strip ailerons, and I have programmed in throw at 25% of aileron throw for both.

This planes a floater anyway, but I can rog in a shorter distance with the flaperons deployed, but landing gets tricky trying to use them. The plane does go slower, but drag is way up, so what often happens is I wind up doing a small stall just before touchdown making the landing bouncy.

I now use the spoilerons for the landing glide. Not sure why, but they seem to create a controlled sink that glides much further than if using the flaperons, and landings are pretty easy to grease in.

Works for me.

Dean in Milwaukee

[xmech]

I had flaperons setup on my Sig Something Extra for a while. Didn't like em. Seemed to make airplane kind of squirrely on landing.Of course the Something Extra will land at a crawl anyway, and flaperons weren't needed.Think they would be better for a heavier higher wing loaded airplane.Having a crow setup works much better, but you need four control surfaces and two more servos to do that.

[tim hooper]

Thread closed.

Please do not post the same thread in multiple forums.

Thank you.

Tim Hooper

[capncrunch]

I think that what you may have heard in the first post of the thread is advice relating to planes with inboard flaps/outboard strip ailerons.

for gliders and such, setting up "CROW" or "butterfly" airbrakes is used for dethermalizing or spot landings. i've seen a guy locally using it for slowing down vertical descent on a fun fly plane :)

if you set up an airbrake like this, and you set the outboard ailerons to go down and the inboard flaps to go up, you are aerodynamically destabilizing the wing. its the reverse of wash-out, the ailerons are at a higher angle of attack than the flaps, and so they stall sooner than the flaps, causing a tip-stall.

but, if you are mixing in flaperons, you dont need to worry about this. moving the flaps up would probably result in a crash :)

good luck!

barrett

[Martin Hunter]

Cross posting to multiple forums is not allowed. I'm closing this down.

Martin

[Gordon]

Lowering strip ailerons as flaperons does lower landing speed and is safe to do. I've used this system regularly for over 20 years on many models and wouldn't be without it.

However, once the flaperons are lowered more than about 10deg, you begin to lose aileron effect and risk generating significant adverse yaw when you try banking the model. Not a problem with a computer radio. Just arrange for rudder to be slaved to aileron when you switch in the flap ... start with 50% mix and experiment to get the final figure right.

You can operate the rudder with your thumb to counter the adverse yaw effect without mixing of course, but mixing is easier.

I set up the throws so that flap deflection doesn't exceed max aileron deflection, and limit flap deflection to about 15deg.

You'll probably have to mix in some up or down elevator trim with flaps lowered, which will then automatically achieve the landing trim described by Dereck.

Gordon

[Ollie]

Flaps up decreses the maximum lift coefficient of the wing by reducing or making negative the airfoil camber. This increases the stall speed and reduces the potential for slowing the model. The increased drag of flaps-up bleeds off speed very quickly and with up elevator, gives the illusion of lowering the landing speed. The best technique is to apply up elevator sooner with a long shallow landing approach so that speed can be bled off before touch down without resorting to up-flaps.

The trouble with flaperons down is that it introduces severe adverse yaw while the aileron response is decreased at slow speed.

The solution to a steep approach with a low landing speed is seperate flaps and ailerons.

[leccyflyer]

This thread was posted in four different forums. Such cross posting to multiple forums is generally accepted as being bad etiquette and is not permitted. The four separate threads have now been merged into one, located in the forum most specific to the query being made, which regards aerodynamics and forms part of the Modelling Science forum.

Brian