Ailerons Up?

[Murocflyer]

On plane like the Tyro (below), if I set my Optic 6 in "Camber Mode" I can raise both ailerons and lower (or raise) the elevator. What is this supposed to do for me? I have experimented with it and it doesn't seem to do much if anything at all.

I imagine this function is used for slowing big gliders down, but not really needed on a 16 ounce plane like the Tyro?

Be nice to know what I am missing (or not missing).

Thanks,

Frank

[macboffin]

Raising both ailerons, (whilst hopefully retaining aileron function) will dump a lot of lift,,enable a short , steep , but slow descent path into a small field space.It would need simultaneous elevater trim, to maintain pitch stability. As you say, not much point for a trainer type! You don't have to do it because you can!

[Murocflyer]

Thanks for the response. So if the ailerons went up, I would have to add in some down elevator since the raised ailerons would make the nose go up correct? A little down should keep her straight. Sound right?

Thanks,

Frank

[slipstick]

Most often dumping lift using the ailerons as spoilers like that DROPS the nose so UP elevator is needed to keep it flat....but it varies from plane to plane.

Steve

[MarkusN]

Might also be a "snap-flap" mixer. It mixes elevator into flap, elevating lift at the wing when up-eleavator is applied and vice versa. Makes for "snappy" maneuvers.

Actually, looking at the name of the mixer ("camber mode"), that's probably the intention. The idea is to adjust camber of the wing to the flight speed "preselected" by the eleavator.

[Murocflyer]

Did some experimenting this morning. I found out that 65% ailerons up slows the plane down nicely without any pitch up or down although the nose does drop some because of the slower airspeed. A little up elevator mixed in and she lands sweetly.

Frank

[JetPlaneFlyer]

I'd have thought that the last thing you would want is ailerons up for landing. Having both ailerons up will decrease the airfoils camber and lower the Cl max (maximum lift coefficient) of the wing and hence will mean that the stall speed is increased; so you will have to land faster. Just look at the landing flaps fitted to many models and most full size aircraft... they move down for landing which increases the camber and hence lowers the stall speed.

Adjustable camber is often used on high performance gliders. Ailerons (slightly) up gives low camber which is good for high speed. Ailerons down gives high camber which gives more lift which is good for soaring and for landing.

Ailerons deflected up at a high angle will act as spoilers and give a fast decent but due to the increased stall speed you would not want to land in that configuration.

[Murocflyer]

Interesting info, thanks. I'm wondering since the ailerons are relatively small, they don't increase the stall speed that much?

I'll do some more experimenting and see how it works with the ailerons down next time.

Too bad I didn't have a cameraman to film the differences. It would be cool to see them.

Frank

[Rodney]

I have found that, on most planes (especially high winged ones), having the ailerons set slightly up improves the flight characteristics greatly. It especially helps to minimize the down stick force required when flying inverted. And, yes, on most of mine, if the ailerons are canted a bit up, it requires more down trim to fly level. This is not always the case however, I have had one (low wing type) that required up trim. I always experiment on any new plane to determine where the "sweet spot" is for the aileron setting. There always seems to be one position where everything works better and requires no trim for different airobatics or different flight speeds. Try experimenting, I think you will find the results enlightning.

[JohnBoy07]

Flaperons on sport or aerobatic planes can be slaved to elevator to cause very tight loops. That is, as the elevator goes up the ailerons can be slaved to a down deflection. The result is the elevator causes the tail to go down and the flarerons cause the main wing to go up - tighter loops than just the elevator. The reverse can be used to enhance the waterfall (outside loop with power off initially with full power when inverted).


Other than that, a sport plane might benefit from flaps (down flaperons) to get added lift and slower flight. Probably not an issue for a model plane as they are overpowered, but something that helps real planes that are underpowered.

[Murocflyer]

As soon as the weather permits, I'm gonna do some experimenting and see how she flies with the ailerons up as speed brakes and down as flaps (flaperons?).

Frank

[Brandano]

actually lowering both flaperons causes more drag than raising them as spoilers, but it also lowers the stall speed because it adds camber to the wing. This allows for much shorter landings, but will require more up elevator to keep th plane level, and it will make it more sensitive to th ground effect that might in turn stretch the landing run again. The best of both worlds is to have both flaperons and spoilers on the back of the wing to kill lift once you are sure you are going to land. You might try to fly an approach with the flaperons down and move them up in spoiler position once the wheels are on the ground to help the plane "stick"

[vintage1]

Up ailerons make good airbrakes..will kill lift in the approach and make it steeper, but typically no slower.

Down alairons will also add drag, but slower the sall sped.

This seems better, but its dangerous with outboard ailerons. The outboard section of the wing will stall first..makes for an easy way to pile a model in, if you do a slow speed turn..

Best odf all is crow braking. inboard flaps down, alierons up. That's how you kill lift and lower speed on a sialplane.

For power stuff, inboard flaps is best.. no need to flip the ailerons up. The glide angle is usually steep enough, and you want to basically just slow the model down some.

[Murocflyer]

Did a little experimenting today.

With flaperons down (30%) she wants to glide forever -certainly not the desired affect I was looking for, but it was cool to see. I'll think I'll stick with the ailerons up so I can "drop it right in" when need be.

Thanks for all the responses and opinions. I definitely learn a lot every time I post here.

Frank

[MarkusN]

This seems better, but its dangerous with outboard ailerons. The outboard section of the wing will stall first..makes for an easy way to pile a model in, if you do a slow speed turn.
Another disadvantage of down ailerons is that you lose roll authority. Not something you want during approach. So with single ailerons using them UP for spoilers is usually best.

[gigelus2k3]

I have a low wing plane that seems to need more washout than what I have built into its wing.

If I set both ailerons to slightly point up (just a few degrees), would the wing behave like it has more washout? This setup would be permanent.

The plane is not an aerobatic one, therefore I'm not looking for neutral behavior when it's belly up.

Serban

[Murocflyer]

If the wing is balsa and it's covered, you can simply twist the wing tip, TE up, and blow hot air on it to shrink the now loose covering. Works well.


Frank

[gigelus2k3]

Frank, it your reply was addressed to me, then no, the model is not balsa but built up depron instead.

Serban

[Murocflyer]

Frank, it your reply was addressed to me, then no, the model is not balsa but built up depron instead.

Serban

That's a bummer. Not sure how you can re-shape depron. Oh well.

What percentage of the wing is the aileron? Does it go out to the wing tip?

Frank

[gigelus2k3]

The aileron is about 45% of the wing and doesn't reach the wing tip.

Anyway, I thought it's easier to actually do it and see what changes. I dialed 6% on each aileron (CH1 and CH5) in my Optic6's STRIM setup and gave it a try.

It actually flew much nicer and did not drop a wing when I reduced the speed. This trim is here to stay (until the plane's demise that is).

Cheers,

Serban

[JetPlaneFlyer]

Moving ailerons 'up' could only have a washout type effect if the ailerons are located outboard rather than full length strip type ailerons.

***EDIT***..I see from your last post that you did in fact state that the ailerons occupy only 45% of the span.

[Murocflyer]

Postscript. I have found that using ailerons up on approach to about 5 feet off the ground, then switching them off seems to work really well this model. Makes for some very short but nice landings.

Frank

[tommyeflight89]

I was messing around with this type of function on my Laserarts 48" Cub. I was screwing with flaperon mixing, crow mixing, aileron/rudder mixing etc just for fun. It lands at snails pace regardless, but with flaperons or spoilerons, it almost stops.
Be careful tough, you still want to retain enough travel...

[Texas Buzzard]

I'd have thought that the last thing you would want is ailerons up for landing. Having both ailerons up will decrease the airfoils camber and lower the Cl max (maximum lift coefficient) of the wing and hence will mean that the stall speed is increased; so you will have to land faster. Just look at the landing flaps fitted to many models and most full size aircraft... they move down for landing which increases the camber and hence lowers the stall speed.

Adjustable camber is often used on high performance gliders. Ailerons (slightly) up gives low camber which is good for high speed. Ailerons down gives high camber which gives more lift which is good for soaring and for landing.

Ailerons deflected up at a high angle will act as spoilers and give a fast decent but due to the increased stall speed you would not want to land in that configuration.
.................................................. ...................................


Jet plane flier is Absolutely correct.
If you raise both ailerons what you have done is to reduce the lift of that wing. Also you have lowered the incedence of that wing. You will have to fly FASTER to maintain altitude.

Back in the nineties a sailplane designer from Washington state ( he designed the Windsong) added a gimmick to speed up the sailplane when going to look for another thermal. It was simply a servo that raised the ailerons several degrees - it usually turned out to be 2 degrees up aileron. This speeded up the plane significantly. Also the elevator had to be given a touch of up when you raised the ailerons.

To slow a plane for landing it is standard practice to lower the flaps or in the case of strip ailerons....lower both ailerons. This increases lift at the lower speeds. You may have to give a click of down on the elevator. UP AILERONS FOR LANDING DOESN'T MAKE SENSE.

[vintage1]

OUTBOARD up alierons make a LOT of sense..its washout by another name and stops tipstalling in slow turns.

If you ver see pictures of Albataros WWI fightres,they had permanently uprigged ailerons. I suspect the pilots found this helped stop it flicking after some drunken rigger did it accidentally.

Shame the wings still folded in a dive tho..

[JetPlaneFlyer]

Actually Vintage I think you will find moving aileron 'up' does not really have much in the way of washout effect... Reflexing the TE just does not have the same effect as reducing the AoA of the entire airfoil as is the case with washout.

To demonstrte this i run a simulation in Profilli using the Clark-Y and the Clark-YS (which is identical to the Y apart from a reflexed TE). The results show that the YS stalls 2.5 Deg BEFORE the ordinary Y. This needs adjusting because the flipped up TE effectivly meand that the YS chord line datum is 2 degrees different to the Y... So in reality the YS is stalling half a degree earlier than the Y using a common datum of the flat underside of the airfoil, for the sake of argument leats say it stalls at the same AoA ;) The point is the 'up aileron' did not have a washout effect, all it did was reduce the lift produced, also note that the stall on the YS is much sharper than the trusty standard Clark Y.

On this evidence moving the ailerons up will mean that you need to either land faster and/or fly closer to the stall, and the stall when it comes will be sharper.... not a good combination.

[vintage1]

Try it with a curved plate WWI airfoil..

[biber]

JPF, please do the same calculations with a Clark-Y and modify that one to have a flap.
Then examine the one with the upped flap aswell.

Can you supply the coordinate files the Clark-Y and Clark-YS you used?
Your calculation will give a fair compare only if the airfoil coordinates upto the hingeline
are identical and the y-ordinate of the Clark-YS's TE is positive (with the y-ordinate of the Clark-Y being (at least close to) zero).

biber

[JetPlaneFlyer]

Try it with a curved plate WWI airfoil..
The model that was the subject of this thread looked like it had a Clark-Y'ish type section so I think the graph is reasonably valid in the context of the original discussion. However I'll run one with a WWI type airfoil but I'll have to wait till I get home.
BTW... I think the ailerons were reflexed on the Albatros and similar WWI aircraft to reduce adverse aileron yaw ;)

JPF, please do the same calculations with a Clark-Y and modify that one to have a flap.
Then examine the one with the upped flap aswell.

Can you supply the coordinate files the Clark-Y and Clark-YS you used?
Your calculation will give a fair compare only if the airfoil coordinates upto the hingeline
are identical and the y-ordinate of the Clark-YS's TE is positive (with the y-ordinate of the Clark-Y being (at least close to) zero).

biber

The Clark YS is supposed to be identical to the Clark Y except from the reflexed TE, you can get coordinates and images here: http://www.ae.uiuc.edu/m-selig/ads/coord_database.html It's hard to compare the coordinates back to back because the reflexed TE means that the camber line reference is different.
In any case to avoid any doubt I'll modify a Clark Y to feature both 'Up' and 'Down' aileron deflection and see how they shape up.



It's maybe not so surprising that 'up' deflected aileron does not work like washout... when you think of it why should it? The basic AoA of the wing is unchanged and rather than delay flow seperation from the wings upper surface the reflex will cause a local increase in static pressure which can only promote seperation... this issue is well recognised in reflexed airfoils operating at low'ish Re.

[biber]

i just checked the database you linked and found the issue I was trying to point out.

Pleas look at the graphs to see what I mean:

http://www.ae.uiuc.edu/m-selig/ads/afplots/clarky.gif
http://www.ae.uiuc.edu/m-selig/ads/afplots/clarkys.gif

The point I'm trying to make is that if you raise the ailerons only and have some inboard wing section unchanged,
all parts of the wing in front of the hingeline remain at the same attitude,
while the TE at the aileron part of the wing moves away upwards from its previous position.

Now in the two files the reflexed airfoil is rotated to set LE and TE level again which does not happen on a wing.

That means you would have to translate the YS-Graph to the right,
by the amount of rotation that was made to level the LE and TE in the file (about 1.8°),
to get a correct compare.

Still it could be the unchanged Clark-Y winning the contest but if so, by a small amount.
However, the YS seems to be not really smooth, its file seems to have much less coordinates than the flie of the Y which might make big difference in the predicted stalling behaviour.
(checked the files, Clark-Y contains 122 coordinates, YS only 34)

biber

[JetPlaneFlyer]

Biber,
Read my original post again... I did adjust by 2 degrees to compensate for the difference in chord line relative to the common 'flat bottom' airfoil datum... Even with this adjustment the reflexed airfoil stalls at the same AoA or slightly before the non reflexed version.

[vintage1]

It's maybe not so surprising that 'up' deflected aileron does not work like washout... when you think of it why should it? The basic AoA of the wing is unchanged



I THOUGHT the angle of attack was defined as the angle between the nose and the tail of the airfoil, in which case it most certainly does change..

In the limit consider a flat plate wing/aileron, and then reconsider what you just said..

Also, if the angle of incidence doesn't change, why do ailerons work at all?

[CloudyIFR]

AoA is reference from the chord line of the airfoil, which is a straight line drawn from the leading to trailing edge of the airfoil, to the relative wind. Relative wind is the direction the airplane is moving through air. The slower you fly the higher the AoA has to be to maintain straight and level flight, in order to create more lift.

If you have full span ailerons and increase or decrease camber your are not affecting washout or washin, respectively.

However, if you have say 1/3rd span ailerons in the outer part of the wing then you would be affecting washout/in with a deflection change.

Curtis
Montana

[JetPlaneFlyer]

AoA is reference from the chord line of the airfoil, which is a straight line drawn from the leading to trailing edge of the airfoil, to the relative wind. Relative wind is the direction the airplane is moving through air. The slower you fly the higher the AoA has to be to maintain straight and level flight, in order to create more lift.

If you have full span ailerons and increase or decrease camber your are not affecting washout or washin, respectively.

However, if you have say 1/3rd span ailerons in the outer part of the wing then you would be affecting washout/in with a deflection change.

Curtis
Montana

Curtis, of course you are correct, due to a 'quirk' of the way AoA is measured (i.e. from a datum of tip of TE to Tip of LE chord line) moving the ailerons up does technically create geometric washout. However what aileron up deflection does not do (I believe) is to cause the tips of the wing to stall later than the root, which is the effect you actually want.

I think that stating that ‘aileron up’ deflection creates washout, while technically accurate, is possibly a little misleading as it implies that it has a similar effect to washout which I don’t believe to be the case.

[JetPlaneFlyer]

I THOUGHT the angle of attack was defined as the angle between the nose and the tail of the airfoil, in which case it most certainly does change..

In the limit consider a flat plate wing/aileron, and then reconsider what you just said..

Also, if the angle of incidence doesn't change, why do ailerons work at all?
I think you are splitting hairs on terminology and in doing so losing sight of the key point I'm trying to make... When I said 'basic AoA' what I had in mind was the angle of attack of the fixed part of the airfoil excluding the movable aileron... I accept that technically AoA is measured from a chord line datum which does change with aileron deflection.

The basic point I'm trying (unsuccessfully?) to make is that moving outboard ailerons up does not have the same EFFECT as washout.... ie. it does not prevent tip stall.

[biber]

Ok, JPF, I missed the statement, where you did correct for that in the text, so do have a point there.

Still I'd rather use the same file and modify it, because of the different 'resolution' of the two files.
That cam make a considerable difference, especially in stalling AoA.
To my knowledge Profili lets you add flap deflections just like Xfoil does.
At least in Xfoil you wouldn't even have to correct the AoA values afterwards,
since Xfoil does only rotate the flap and leaves the rest as it is.

biber

[JetPlaneFlyer]

ok... Here is a graph of a standard Clark-y against a modified Clary-Y with aileron deflected up. The reference chord line datum remains the same for the aileron up airfoil as for the standard foil so no need to apply any adjustment.
As you can see the stall occurs at about the same point for both, splitting hairs maybe the stall is slightly earlier and sharper for the modified airfoil.

[JetPlaneFlyer]

Vintage,
Here is a graph for a typical WWI type airfoil aginst the same foil but with an Albatros type TE reflex.
Interestingly on the heavily undercambered airfoil the stall AoA is increased slightly with reflex, but the Cl value really takes a big hit:

[vintage1]

Yes..the key is that the inner wing starts to stall before the outer tips..giving sort of 'understeer' in tight lows speed turns.

In reality the albatros ailerons were progressively larger towards the tips as well. and somewhat more chord % than you show there.