Aileron to flap alignment

[Anticept]

I like the expert description on this subject coming from Anticept. If I read it right, you are saying the physics of banking and looping are the same when thinking about pulling the stick back to stay coordinated in both. Since the flaps and ailerons have the effect of increasing both lift and drag. What role do these devices play in a stall if any? Given an increased AOA eventually results in loss of lift, and as you say, when that loss of lift falls below that needed to counter gravity and the weight of the aircraft leading to loss of control. To what effect do the flaps and ailerons contribute to this loss of equilibrium?

 

I got back and edited my post. Check the new section about ailerons.

 

Flaps don't directly cause any kind of stalls either (unless we want to talk about turbulence over the tailplane, but it's rare). They simply make a skinny wing seem like a big fat one. The reason you can stall on flap retraction is because you generate less lift, so AoA will increase momentarily, possibly past crit AoA.

 

When you deploy flaps, you increase lift. However, it won't change the AoA directly (it will momentarily as the forces find equilibrium again). *You* are actually the biggest factor to an AoA change, because you will need to nose over to counter the increase in lift and drag if you want to keep vertical speed and airspeed. Aileron deflection can do this too, but again, the effect is so incredibly small, you would need to have a HUGE aileron deflection, and the resulting roll will be the major factor to a stall, not the aileron.

[FredG]

Anticept, thanks, yes I do understand that banking the wings results in a lift vector that is no longer perpendicular to the horizon, and that once banked the elevator will affect turn rate and the rudder will affect pitch.

 

Really, what I was asking is, if the aileron creates no lift, then why does the wing with a down aileron deflect upward and why does it have induced drag, if it is not creating lift? And, since ailerons and flaps are pretty similar in their physical configuration, it seems that if the downward deflection of a flap creates lift, then the downward deflection of an aileron would also create lift. Perhaps it has to do with the greater deflection of the flaps than the ailerons.

 

Finally, you write that, "you try to bank close to a stall, and one wing drops from a stall, it's because you were uncoordinated." Yes this is logical. But isnt it also true that the uncoordinated condition would be either a slip or a skid, and that the wing that drops is predictable in the way we have been discussing?

[FredG]

Tom,

 

Yes, I agree, asymmetrical drag may be the issue. But that brings us back to the first question, why would some pilots want to disconnect the flaperon feature of the CT in order to mitigate asymmetrical drag that might occur during a sideslip? It seems that the asymmetry of drag would be unchanged regardless of any change in the angle of the flaperons (that occurs when the flaps are deployed), as long as that change was equal, left and right.

 

Fred

[Ed Cesnalis]

We think about reflex flaps that optimize our cruise speed but we deploy reflex flaperons as well. If we unlinked the flap deployent from the ailerons we would have to fix their position so they could no longer droop or reflex and we would give up speed due to the flapersons no longer reflexing.

 

 

Careful what you wish for.

[Tom Baker]

We think about reflex flaps that optimize our cruise speed but we deploy reflex flaperons as well. If we unlinked the flap deployent from the ailerons we would have to fix their position so they could no longer droop or reflex and we would give up speed due to the flapersons no longer reflexing.

 

 

Careful what you wish for.

 

Unless they were positioned in the reflexed position.

[Tom Baker]

Tom,

 

Yes, I agree, asymmetrical drag may be the issue. But that brings us back to the first question, why would some pilots want to disconnect the flaperon feature of the CT in order to mitigate asymmetrical drag that might occur during a sideslip? It seems that the asymmetry of drag would be unchanged regardless of any change in the angle of the flaperons (that occurs when the flaps are deployed), as long as that change was equal, left and right.

 

Fred

 

Fred,

Go out to your airplane and put the flaps at -6 with the ailerons nuetral and make note of the position. This is where we want the aileron for the least amount of drag. Now lower the flaps to 40 and add aileron until one is equal to the position when you had -6. Now look at how far down the other aileron is and think about how much drag there would be on that side. I wish you were here by the airplane so I could show what I am talking about. I think it would make it easier.

[Anticept]

Anticept, thanks, yes I do understand that banking the wings results in a lift vector that is no longer perpendicular to the horizon, and that once banked the elevator will affect turn rate and the rudder will affect pitch.

 

Really, what I was asking is, if the aileron creates no lift, then why does the wing with a down aileron deflect upward and why does it have induced drag, if it is not creating lift? And, since ailerons and flaps are pretty similar in their physical configuration, it seems that if the downward deflection of a flap creates lift, then the downward deflection of an aileron would also create lift. Perhaps it has to do with the greater deflection of the flaps than the ailerons.

 

Finally, you write that, "you try to bank close to a stall, and one wing drops from a stall, it's because you were uncoordinated." Yes this is logical. But isnt it also true that the uncoordinated condition would be either a slip or a skid, and that the wing that drops is predictable in the way we have been discussing?

 

I did not say that they don't create lift, I said they don't directly affect stalls. The lift and drag they create is just very negligible compared to the entire wing. Flaps also deflect much more, so they generate a lot more lift. Additionally, proper aircraft design dictates that you can have a stalled wing, but the ailerons should not be. Basically, the aileron has very little to do with a stalling wing, rather, it sets up a chain of events that can lead to a stalled wing.

 

My context has been in a landing configuration, under the assumption that we may be slipping in a crosswind. Whichever wing is slower than the other or generates less lift than the other will be the one that stalls first.

 

 

Anyways, I am curious as well, why does anyone want to remove the flaperon link? It's because of flaperons that we can fly so slowly, and if flapperons are a problem, why don't people use a smaller setting, like 15? We need flapperons to be able to fly as slowly as we can, they provide us such a wide operating ramge. And if asymmetric drag is a concern, then perhaps the person needs to remember to say ahead of the airplane?

[Ed Cesnalis]

...When you deploy flaps, all you do is increase lift...

 

Anticept,

 

You can't create lift without creating induced drag

[Anticept]

 

 

Anticept,

 

You can't create lift without creating induced drag

 

That's not what my statement meant. Looks like it got through during my rush to type it out. Removing the "all you do" part.

 

As an additional note, this is why fowler flaps are so popular on big birds, they allow the lift coefficient to be raised even higher than other forms of flaps before drag really becomes a problem.

[FredG]

Tom, you wrote, "Go out to your airplane and put the flaps at -6 with the ailerons nuetral and make note of the position. This is where we want the aileron for the least amount of drag. Now lower the flaps to 40 and add aileron until one is equal to the position when you had -6. Now look at how far down the other aileron is and think about how much drag there would be on that side. I wish you were here by the airplane so I could show what I am talking about. I think it would make it easier. ".

 

Tom, I understand what you are saying. Do you think that, even though the left and right flaperons move the same amount with flap deployment, the fact that it is possible to get more absolute downward deflection of the flaperon with 40 degrees (compared to -6 degrees) of flaps makes the plane more prone to drop a wing while in a slip?

 

Fred

[Ed Cesnalis]

If someone tufted a wing and used a few external go-pros it might lend some clues or even explain what is taking place.

[Tom Baker]

Tom, you wrote, "Go out to your airplane and put the flaps at -6 with the ailerons nuetral and make note of the position. This is where we want the aileron for the least amount of drag. Now lower the flaps to 40 and add aileron until one is equal to the position when you had -6. Now look at how far down the other aileron is and think about how much drag there would be on that side. I wish you were here by the airplane so I could show what I am talking about. I think it would make it easier. ".

 

Tom, I understand what you are saying. Do you think that, even though the left and right flaperons move the same amount with flap deployment, the fact that it is possible to get more absolute downward deflection of the flaperon with 40 degrees (compared to -6 degrees) of flaps makes the plane more prone to drop a wing while in a slip?

 

Fred

 

Yes, and in a direction opposite of the aileron input.

[FredG]

Tom, thanks!

fg

[Anticept]

Ooooooohhh I see what you guys are saying!

 

Yes, the wing with the flaperon that RAISES will show a small drop, this is normal for a flapperon, because it is the same as raising the flaps for only one wing. This is due to the decreasing camber, thusly, decreased lift. I thought we were talking about an AILERON causing a stall, then I thought we were talking about the downward deflecting flapperon causing a wing drop.

 

You would have to be doing some pretty significant deflection for this to become a problem, because as soon as you neutralize, the wing will raise again.

[Ed Cesnalis]

You would have to be doing some pretty significant deflection for this to become a problem, because as soon as you neutralize, the wing will raise again.

 

 

This is a landing issue for me. In flight I think about amount of deflection but when I land I think about enough flaperon to counter drift and enough rudder to keep me aligned. I tend to loose sight of whether that is 30% rudder or 90%.

 

I only find a problem at 40 degrees when a meaningful crosswind correction is needed and its not so much that the wing drops as the fact it does so without warning.

 

Back to my comment on careful what you wish for. Your now ailerons need to be fixed but I bet they won't be fixed in the reflex position because of the likely negative effect on slow speed control.

[Anticept]

CharlieTango, if I may make a point, trying to land with 40 degrees of flaps in anything more than a light draft crosswind might require some re-thinking about the approach .

[Tom Baker]

Ooooooohhh I see what you guys are saying!

 

Yes, the wing with the flaperon that RAISES will show a small drop, this is normal for a flapperon, because it is the same as raising the flaps for only one wing. This is due to the decreasing camber, thusly, decreased lift. I thought we were talking about an AILERON causing a stall, then I thought we were talking about the downward deflecting flapperon causing a wing drop.

 

You would have to be doing some pretty significant deflection for this to become a problem, because as soon as you neutralize, the wing will raise again.

 

I am not talking about the downward aileron causing the stall. I am saying that the airplane will drop the wing and turn towards the downward deflected flaperon when it stalls. This is why using full flaps in a crosswind can cause a problem. Whether it is caused by the difference in camber, angle of attack, or the difference in drag I don't know, but the problem is there. IMO increasing drag on the downwind side of the airplane while landing in a crosswind is a bad idea.

[Tom Baker]

This is a landing issue for me. In flight I think about amount of deflection but when I land I think about enough flaperon to counter drift and enough rudder to keep me aligned. I tend to loose sight of whether that is 30% rudder or 90%.

 

I only find a problem at 40 degrees when a meaningful crosswind correction is needed and its not so much that the wing drops as the fact it does so without warning.

 

Back to my comment on careful what you wish for. Your now ailerons need to be fixed but I bet they won't be fixed in the reflex position because of the likely negative effect on slow speed control.

 

Just checked my airplane which is a CTLS and the ailerons do not move up when you go fron 0° to -6°, they only go down when you add flaps. I can't remenber if the CTSW is different. I don't know how much difference having the ailerons droop makes to the stall speed, but it can't be much. We only have a 5 knot difference in stall speed between -6° and full flaps.

[Doug G.]

We only have a 5 knot difference in stall speed between -6° and full flaps.

Actually

Vs @ -6° = 50 kts

Vs @ 35° = 40 kts

[Anticept]

I am not talking about the downward aileron causing the stall. I am saying that the airplane will drop the wing and turn towards the downward deflected flaperon when it stalls. This is why using full flaps in a crosswind can cause a problem. Whether it is caused by the difference in camber, angle of attack, or the difference in drag I don't know, but the problem is there. IMO increasing drag on the downwind side of the airplane while landing in a crosswind is a bad idea.

 

WHEN it stalls with a downward deflected flapperon, the wing with the downward deflected flaperon will have a good bit more drag than the one that is raised, so naturally it will want to turn in that direction. This is why you go ailerons-neutral in a stall, because if you are starting to spin to the right, for example, and you try to roll left to correct, you only increases drag further on the right wing due to the downwards deflection, steepening the spin. Also keep in mind though, if that downward deflected flapperon is also on the lower wing, gravity will also pull the nose towards it, so that can be a factor too!

 

I suspect you already know this Tom, I'm just adding this in using my own words if people are still confused

[Ed Cesnalis]

Actually

Vs @ -6° = 50 kts

Vs @ 35° = 40 kts

 

50 kts sounds too fast for LSA

[Tom Baker]

WHEN it stalls with a downward deflected flapperon, the wing with the downward deflected flaperon will have a good bit more drag than the one that is raised, so naturally it will want to turn in that direction. This is why you go ailerons-neutral in a stall, because if you are starting to spin to the right, for example, and you try to roll left to correct, you only increases drag further on the right wing due to the downwards deflection, steepening the spin. Also keep in mind though, if that downward deflected flapperon is also on the lower wing, gravity will also pull the nose towards it, so that can be a factor too!

 

I suspect you already know this Tom, I'm just adding this in using my own words if people are still confused

 

I agree if you are doing stalls the ailerons should go to nuetral, but when you are a few feet off the ground doing crosswind landings I'm not shure it would be much help. Landing accidents are why some were asking to have the flapperons removed.

[Tom Baker]

Actually

Vs @ -6° = 50 kts

Vs @ 35° = 40 kts

 

That may be indicated airspeed, but the AOI says 44 kts CAS for -6° and 39 kts CAS for 35°. This is where I picked up the 5 kt difference.

[Doug G.]

Mine are from the newer unofficial, unreleased POH. Strange, huh?

[Anticept]

Mine are from the newer unofficial, unreleased POH. Strange, huh?

 

LSAs are not allowed to stall above 45 kts in VS1 configuration (14 CFR 1.1, light-sport aircraft). I am not sure if -6 flaps is any different than 0 flaps per this definition though.