Spoilerons rigged up or down to reduce stall ......

[nixy]

...but keep some roll control near the stall.

I have a Ripmax Mustang fitted with full width ailerons. Am I correct in thinking that if both were rigged up, with some aileron differential, some power on, and some rudder linked with aileron, that the stall (approach) speed could be reduced whilst maintaining some roll authority?

Cheers

[JetPlaneFlyer]

Deflecting full length ailerons 'up' will actually increase the stall speed, not lower it. This is because by moving the ailerons up you would be reducing the camber of the airfoil and therefore the coefficient of lift will be lower. That's why aircraft have landing flaps that move down, not up ;)

Maintaining aileron authority near to stall is a different issue. Aileron differential and rudder coupling would help in this respect... Deflecting the ailerons up may theoretically help a little too but at the expense of an increase in stall speed as noted above.

Steve

[Marion]

I have had good luck doing it just as you described. The UP position reduces lift, making you fly at a higher angle of attack to maintain altitude == thereby increasing drag a good bit. Might not work for everybody and all airplanes, but has worked great for me.

[JetPlaneFlyer]

The UP position reduces lift, making you fly at a higher angle of attack to maintain altitude == thereby increasing drag a good bit.
Increasing drag does not decrease stall speed... all it does is reduce the models maximum speed.

If you want to lower the stall speed you need to do one of three things:Increase the wing areaDecrease the models weightIncrease the coefficient of lift

Steve

[BMatthews]

JPF is right but then so is Marion. Deflecting them up will reduce the maximum lift the wing can develop and so you end up increasing the angle of attack and that makes more drag. This means the model will settle in with a steeper and much more easily judged glide angle to touch down a lot more accurately. But it'll do so at a more or less normal flying speed rather than slowing down like a model with flaps would do.

Deflecting the ailerons down quickly lowers the roll control authourity and introduces a LOT of adverse yaw. I tried flaperons on a model years ago and it was hard to control at angles more than about 20 degrees. At close to 90 there was no roll effect at all and at that point no adverse yaw either. I used it but only for brief moments to kill off lots of altitude while in a steep dive since the model only had elevator control when deflected to that angle.

SO I'd suggest up traveling spoilerons and limit the spoiler angle to about 30 to 40 degrees. Beyond that I suspect your aileron roll function will suffer.

[markschaffin]

The real question seems to be will raising the ailerons give you a higher maximum lift coefficient. If the airfoil normally starts to stall via trailing edge separation which progresses forward, raising the ailerons will reduce the aft camber and might reduce the stress on the boundary layer at the trailing edge. You would have to experiment to see how well this works and how it affects the other modes of flight. An interesting experiment. Still might be better to land just a tad faster.

Mark

[macboffin]

Just a nit-picking comment ; "spoilerons" are not upwards deflected ailerons ; they are seperate control surfaces ususlly positioned about half-way between leading and triling edges. When operated they stand up like fence across part of the wing. Sailplanes use them to raise drag and kill some lift, to stop "floating" when landing or to descend steeply without excessive speed ; the "Black Widow" twin boom heavy fighter uses them as primary roll control, having virtually full span flaps. Many other aircraft have used them in this mode.

[Gene Bond]

IMHO, I've found on a few models that by flipping the flapperons up, I can pull higher alpha, while maintaining stability, so I can fly slower... Maybe the stall speed is higher, but when you can fly into extreme alpha w/o instability, all bets are off :)

[raptor22]

Just a nit-picking comment ; "spoilerons" are not upwards deflected ailerons ; they are seperate control surfaces ususlly positioned about half-way between leading and triling edges. When operated they stand up like fence across part of the wing. Sailplanes use them to raise drag and kill some lift, to stop "floating" when landing or to descend steeply without excessive speed ; the "Black Widow" twin boom heavy fighter uses them as primary roll control, having virtually full span flaps. Many other aircraft have used them in this mode.

No, those are spoilers. Spoilerons are in fact ailerons raised upwards. It is a combination of the words spoiler and aileron.

[BMatthews]

No, those are spoilers. Spoilerons are in fact ailerons raised upwards. It is a combination of the words spoiler and aileron.

Actually he WAS right, at least about the P61. A few full size planes used proper spoilerons. Namely the old P61 Black Widow and the Mitsubishi MU-2. There's very likely many others but those pop to mind at the moment.

Lots of airliners use their spoilers in a spoileron roll (get it? "roll"?... :D Golly I kill me sometimes... :D) where they tip up one side to ease into a gentle entry turn without using any aileron. That's a proper spoileron function. Using spoiler operation to achieve roll.

Merely deflecting our normal ailerons up to achieve a speed brake of sorts really isn't a proper spoileron but we all call it that.

[raptor22]

I know that term has been used in the full scale world, but the term "spoileron" is used pretty exclusively in the model world to mean raised ailerons.

We are talking about models right?

--Alex

[Mike the Snake]

The F-14 has no ailerons (as far as I can tell), watch some vids of carrier launches, and you'll see they have only spoiler(ons) for roll authority on the wings, (the tails also work independently as elevons).

Back to models, take a long smooth approach,

With spoilerons, when deployed, cause the tail to drop a little, increasing the aoa, and if the approach is drawn out, the plane Does slow down, but generally spoilerons don't slow the plane, just kills the lift. Aileron authority is retained, even improved with spoilerons deployed.

With Flaperons, the plane maintains it's trajectory (with proper landing elevator mixing), no aoa change, the flaperons really slow things down, However, almost all aileron authority is lost. I've crashed more trying to land with flaperons as you can't get out of trouble with flaperons deployed.

On 60" gliders with full span surfaces, I used both spoileron And flaperon mixes in combination, coming in with flaperons to keep speeds down (a Lot of speed can be scrubbed quickly with a lot of flaperon and down mix) and then switching to spoilerons for the landing where lots of control authority is needed.

I've only heard the term """erons" used on models, as far as I know, "spoilers" are fences that extend up vertically from the wing as on full scale gliders, they do not slow the plane, just kill lift (lift spoilers).

As far as speed goes, with flaperons, yes, you can fly slower before stalling, but as you slow you also lose aileron authority.

[MarkusN]

but generally spoilerons don't slow the plane, just kills the lift.
Careful there. If spoilers would kill significant amounts of lift, they'd actually speed up the plane (as higher speeds would be necessary to maintain lift-weight equilibrum.)

Indeed they do kill some lift, so approach speed must be slightly above minimum speed, lest the plane stall when spoilers are deployed.

Mostly they increase drag, though, so, as others have written, the glide path becomes steeper and more easily manageable.

Same with spoilers on gliders: mostly to increase drag and make the glide path more manageable. Can also be used to pull away speed without climbing away.

[macboffin]

I know that term has been used in the full scale world, but the term "spoileron" is used pretty exclusively in the model world to mean raised ailerons.

We are talking about models right?

--Alex We are talking about aircraft ; usually about pretty small ones, but still aircraft! Lots of mis-applied terms in the model fraternity ; my pet hate is "Semi-symmetrical". Either it's symmetrical, or it ain't! No such thing semi!

[BMatthews]

... my pet hate is "Semi-symmetrical". Either it's symmetrical, or it ain't! No such thing semi!

It's probably fair to say that you're semi right about this semi misunderstanding.... :D

Raptor, that's the thing. It's all semantics and we're all right. But it was only "semi" fair to take macboffin to task over the naming since both uses of the term have become common.

I also think that modelers may be the only folks that use such highly reflexed ailerons as airbrakes. At least I've never seen any such application in full sized aviation outside of camber changing on full sized sailplanes which use a much smaller angle of difference than we use for our spoilerons or ailerbrakes/brakerons or whatever we want to call them.

[Plantoflap]

nixy,
Raising both ailerons will reduce lift and increase drag. If you are in a glide it is the vector L'= square root of (lift^2 +drag^2) that supports the glider. Even though the overall CL is reduced by raising the ailerons, L' is greater than the lift so you can slow down depending on how much stability you have left. The sinc rate will increase while the foward speed (horizontal) will decrease.

For an extreme example, a glider with a L/D of 1 will have a glide slope of 1= 45 degrees. If lift and drag are both 1 lb ea. then the resultant lift will be 1.41 lbs. That implies it is going to slow down.

I built and flew a 32' rigid wing hang gliger that used up-only 5' ailerons controlled individually by squeeze grips on the control bar. When I deployed both of them the sink rate increased and I felt some vibration but it was stable and I couldn't feel any change in air speed. If a wing started to drop I would lower that aileron and that wing would yaw foward while moving up. Seemed natural. If I hit rough air I would release both and Its downward sink momentum would quickly convert to a foward speed increase without zooming. The only problem I had was that it was hard to keep them fully deployed very long especially at higher speeds due to the hand grips I used.

I flew at the 1976 John J Montgomery memorial championships and came in 16th out of 165 competitors largely because of my spot landing ability with that glider. I landed (standing up) in the 3 or 4' bulls eye once and one in the 6' ring out of 3 flights from a 500' hill. I did poorly in the flour bomb drop and shortest flight time events.

I wonder how a model glider would perform with half span flaps and half span up-only ailerons deployed ?

GB