Flaperon travel

26 posts in this topic

Posted

Something I have been thinking about for a while now is the safe limit of flaperon travel. These make such a huge difference in the short field performance of our planes it is always tempting to push the limit to get the max little bit of performance. What I have been thinking about is how to safely increase the useable flaperon travel. I set up my flaperons with the plane level to have about 3 to5 degree reflex angle and 18 degree droop with flaps full on. The warning is that going beyond this could cause contol reversal. So yesterday I measured the maximum combined angle of the flaps with the stick full to the stop both ways. On my plane the mixer linkage makes the travel not exactly equal but they are as balanced as I was able to get them after many hours of adustments. The combined flap/aeleron angles for mine were 40 degrees one way and 46 degrees the other way. Based on this I am thinking that control reversal actually is happening when the flaperon angle exceeds the 40+ degrees. So to maximize the plane's performance safely, we could do this as long as we considered the circumstances and used this information accordingly.

I have to fabricate a better flap control mechanism this summer anyway so I am considering setting up my flap with detents; the first at 10 degrees, second at 18 degrees and a third at say 30 degrees. For any normal flying you would never use more than the 18 degree or the second detent; but in calm conditions when you didn't have to manuver, you could dump full 30 degrees of flaps right at rotation and then back off to 18 degrees as soon as you had airspeed. I have a hunch this could lower the min. take off speed significantly and with knowledgeable use, it could be done safely.

Thoughts?

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Posted

Something I have been thinking about for a while now is the safe limit of flaperon travel. These make such a huge difference in the short field performance of our planes it is always tempting to push the limit to get the max little bit of performance. What I have been thinking about is how to safely increase the useable flaperon travel. I set up my flaperons with the plane level to have about 3 to5 degree reflex angle and 18 degree droop with flaps full on. The warning is that going beyond this could cause contol reversal. So yesterday I measured the maximum combined angle of the flaps with the stick full to the stop both ways. On my plane the mixer linkage makes the travel not exactly equal but they are as balanced as I was able to get them after many hours of adustments. The combined flap/aeleron angles for mine were 40 degrees one way and 46 degrees the other way. Based on this I am thinking that control reversal actually is happening when the flaperon angle exceeds the 40+ degrees. So to maximize the plane's performance safely, we could do this as long as we considered the circumstances and used this information accordingly.

I have to fabricate a better flap control mechanism this summer anyway so I am considering setting up my flap with detents; the first at 10 degrees, second at 18 degrees and a third at say 30 degrees. For any normal flying you would never use more than the 18 degree or the second detent; but in calm conditions when you didn't have to manuver, you could dump full 30 degrees of flaps right at rotation and then back off to 18 degrees as soon as you had airspeed. I have a hunch this could lower the min. take off speed significantly and with knowledgeable use, it could be done safely.

Thoughts?

I think part of the issue was that the original mixer gave you more down aileron than up on the roll control. When coupled with the flaps down, it really made it drop. I think with the new mixer that gives more up than down we can use more flaps before we get into reversal. I was thinking about setting up for as much as I can get, then go to altitude and play with it and see what happens.

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Posted

I think part of the issue was that the original mixer gave you more down aileron than up on the roll control. When coupled with the flaps down, it really made it drop. I think with the new mixer that gives more up than down we can use more flaps before we get into reversal. I was thinking about setting up for as much as I can get, then go to altitude and play with it and see what happens.

Randy, interesting stuff but I don't have my flaperons hung yet so I can't add much. I am, however, thinking of making this flap handle setup for mine. Trade off for the positive detents is loss of infinite adjustability for flaperon extension and positive reflex for cruise trim. Not sure how concerned about those I should be but it's simple and cheap enough to make and try out, or scrap if I don't like it.

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Posted

Doug, Would you please make two of everything you think of. As you know I am only a short drive from your palace, and I am on a fixed income. handjob.gif

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Posted

Randy, interesting stuff but I don't have my flaperons hung yet so I can't add much. I am, however, thinking of making this flap handle setup for mine. Trade off for the positive detents is loss of infinite adjustability for flaperon extension and positive reflex for cruise trim. Not sure how concerned about those I should be but it's simple and cheap enough to make and try out, or scrap if I don't like it.

Doug,

I like the design; it should give every solid flap positioning. There is one thing that has to be changed for the A+ though and that is the flap lever travel when connected direcly to the torq tube as designed only travels through about 10 degrees of arc to deploy the flaps from 3 degrees of reflex to full 18 degrees of flaps. I plan to build a second flap handle with a small roller on it that will roll along the lever attached to the torq tube and deploy the flaps gradually as it rolls up the lever through a longer arc of travel. I don't know if that makes sense without a sketch but the bottom line is we need a system that allows a longer flap handle travel to deploy the flaps.

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Posted

Randy, interesting stuff but I don't have my flaperons hung yet so I can't add much. I am, however, thinking of making this flap handle setup for mine. Trade off for the positive detents is loss of infinite adjustability for flaperon extension and positive reflex for cruise trim. Not sure how concerned about those I should be but it's simple and cheap enough to make and try out, or scrap if I don't like it.

Doug, Jack,

have been thnking about a modified flaperon mechanism this week and I think I will try a different approach to get the lever travel we need. I am going to try to do it with a cable from the linkage at the mixer though a pully mounted to the seat truss and up to the torque tube that the flaperon handle mounts to. As the flaps are pulled the cable will wrap around he torque tube. I will have to mount a return spring the the mixer linkage but that should be easy enough. I think this will give us the mechanical advantage and lever travel we need for our flaps; plus having the mechanical advantage, the wind pressure should not be able to cause the flaps to come off even without locking positions in the flap handle.

I doubt I will do it before the temps warm up a bit but I am anxious to get this working. I am going to give myself a max of about 30 degrees of flaps and see what happens at a safe altitude.wink.gif

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Posted

Doug, Jack,

have been thnking about a modified flaperon mechanism this week and I think I will try a different approach to get the lever travel we need. I am going to try to do it with a cable from the linkage at the mixer though a pully mounted to the seat truss and up to the torque tube that the flaperon handle mounts to. As the flaps are pulled the cable will wrap around he torque tube. I will have to mount a return spring the the mixer linkage but that should be easy enough. I think this will give us the mechanical advantage and lever travel we need for our flaps; plus having the mechanical advantage, the wind pressure should not be able to cause the flaps to come off even without locking positions in the flap handle.

I doubt I will do it before the temps warm up a bit but I am anxious to get this working. I am going to give myself a max of about 30 degrees of flaps and see what happens at a safe altitude.wink.gif

The cable and pulley idea sounds like a great solution! I cant imagine trying to use the flaps as they are set up now. There cant be more than an inch or two of handle travel from stop to stop, and that sure does not give you much to play with for getting various settings.

The linkage on the two hiem joints... can it be shortened very much? If so, you could shorten the output end of the flap torque rod (the one opposite the flap handle) and angle it back under the seat edgeso the cross bar on the gear brace does not even come into play. A good picture of the area and I could draw up what I am talking about and see if it would work for you.

:BC:

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Posted

It would be a lot easier to do what my buddy building the Avid-Kitfox hybrid is doing.

Get yourself a model IV Kitfox flapperon mixer and install it. Way better all around...

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Posted

It would be a lot easier to do what my buddy building the Avid-Kitfox hybrid is doing.

Get yourself a model IV Kitfox flapperon mixer and install it. Way better all around...

Bob was going to do that on his model III. The 1200 bucks for it kinda turned him off though.

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Posted

Dave bought his out of a wreck for $100. Shopping around pays off...

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Posted

If the mixer assembly didn't work well I would look at other options but it works fine and the mounting setup under the seat is perfect; completly out of the way. I just need to figure out a better way to actuate the flaps which is kind of a fun challenge anyway. (we are flying experimentals aren't we?). The fix I am thinking of should cost me all of around $5.

Leni's idea to shorten the T-bar is another option but the shorter you make it will pull the linkage at more of an angle to the pivot pins. With the cable and small pully I should be able to keep the pull in line and get good travel on the flap lever. The advantage to using the shortened T bar is that you have a positive pull and push on the flap levers so no need for a return spring. I may end up trying both ways if I don't like the way the cable setup works.

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Posted

If the mixer assembly didn't work well I would look at other options but it works fine and the mounting setup under the seat is perfect; completly out of the way. I just need to figure out a better way to actuate the flaps which is kind of a fun challenge anyway. (we are flying experimentals aren't we?). The fix I am thinking of should cost me all of around $5.

Leni's idea to shorten the T-bar is another option but the shorter you make it will pull the linkage at more of an angle to the pivot pins. With the cable and small pully I should be able to keep the pull in line and get good travel on the flap lever. The advantage to using the shortened T bar is that you have a positive pull and push on the flap levers so no need for a return spring. I may end up trying both ways if I don't like the way the cable setup works.

I wonder if the return spring needed to return the flaps to the up position will overcome the mechanical advantage of the cable wrapping around the flap actuator shaft? I wonder about a small bellcrank ahead of the t-bar,with a couple of short links, one from the t-bar and one to the cross shaft, would provide the mechanical advantage while still providing a direct mechanical connection with no spring needed? You'd have to split the long shaft with an internal splice to facilitate installation and removal of the long shaft and the short end with the tabs needed connect to the upper link from the new bellcrank. Lots of monkey motion, huh?

Jack

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Posted

Oh, good grief. I just spent a few hours trying to lay out different size and pattern tiles for four interconnected rooms and logged in because I needed a brain break... now this! I better go take a good close look at the set up and try to grasp the issue and suggestions before opening my mouth. I did look in my photo archive to see if Vince did anything on his Avid+ to alleviate the problem, bottom line is not much (pic attached).

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Posted

I looked at how the mechanism works a little closer this weekend and it looks like the aeleron function may depend on some rigidity of the linkage to work correctly. I don't know if cable tension will provide this as a solid support for the flaperon links to lever against. I think I will try Leni's suggestion of shortening the Tee link as much as possible as the first stage of a fix and see how much additional lever travel that will provide. Doing it through an aditional linkage will be option two. I attached a picture of the mixer linkage for a visual.

Nice panel Doug! looks like some expensive glass.

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Posted

Something I have been thinking about for a while now is the safe limit of flaperon travel. These make such a huge difference in the short field performance of our planes it is always tempting to push the limit to get the max little bit of performance. What I have been thinking about is how to safely increase the useable flaperon travel. I set up my flaperons with the plane level to have about 3 to5 degree reflex angle and 18 degree droop with flaps full on. The warning is that going beyond this could cause contol reversal. So yesterday I measured the maximum combined angle of the flaps with the stick full to the stop both ways. On my plane the mixer linkage makes the travel not exactly equal but they are as balanced as I was able to get them after many hours of adustments. The combined flap/aeleron angles for mine were 40 degrees one way and 46 degrees the other way. Based on this I am thinking that control reversal actually is happening when the flaperon angle exceeds the 40+ degrees. So to maximize the plane's performance safely, we could do this as long as we considered the circumstances and used this information accordingly.

I have to fabricate a better flap control mechanism this summer anyway so I am considering setting up my flap with detents; the first at 10 degrees, second at 18 degrees and a third at say 30 degrees. For any normal flying you would never use more than the 18 degree or the second detent; but in calm conditions when you didn't have to manuver, you could dump full 30 degrees of flaps right at rotation and then back off to 18 degrees as soon as you had airspeed. I have a hunch this could lower the min. take off speed significantly and with knowledgeable use, it could be done safely.

Thoughts?

Hi!

I too have wondered about this. How much down-flap is too much and why? I would really like to use as much as possible, because the landing performance just gets better with more.

Since your original question did not get answered in this thread I would like to ask it again and also ask the question "Exactly what is flapperon reversal anyway?"

Seems to me the only thing that could cause the ailerons to seem to "reverese" would be too high of an angle of attack causing a stall on the steepest deflected aileron, thereby making seem like reverse operation. Is that how everyone understands how "reversal" happens?

If that is the case, has anyone actually setup for greater deflection and tried it? When I am trying for my slowest landings, it is never in a lot of wind. I would be willing to live with pretty greatly reduced aileron control with maximum flap deflection as long as I understand what is going on so I can make intelligent decisions about how much flap to deploy in what situation.

Chris Bolkan

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Posted

Hi!

I too have wondered about this. How much down-flap is too much and why? I would really like to use as much as possible, because the landing performance just gets better with more.

Since your original question did not get answered in this thread I would like to ask it again and also ask the question "Exactly what is flapperon reversal anyway?"

Seems to me the only thing that could cause the ailerons to seem to "reverese" would be too high of an angle of attack causing a stall on the steepest deflected aileron, thereby making seem like reverse operation. Is that how everyone understands how "reversal" happens?

If that is the case, has anyone actually setup for greater deflection and tried it? When I am trying for my slowest landings, it is never in a lot of wind. I would be willing to live with pretty greatly reduced aileron control with maximum flap deflection as long as I understand what is going on so I can make intelligent decisions about how much flap to deploy in what situation.

Chris Bolkan

stirthepot.gif

Chris,

Those are my thoughts and understanding exactly. Control reversal has to be the result of stalling one flaperon when it is deflected too far. With pure flaps that isn't too much of a concern but with flaperons we depend on them for aleron control as well so we have to be consevative so they will not cause reversal at full aleron deflection. I think knowledeable use of them in calm conditions should allow much greter flap deployment as long as we have appropriately limitted aleron input. Based on measurements of my plane as currently set up, maximum deflection with full flaps and full stick is around 40 degrees. As long as we stay within that max deflection with any combination of inputs we should not get control reversal. Obviously in a windy/turbulent situation we would not want to put in any more flaps than the 18 degee limit because it is pretty hard to mentally overcome reactive inputs but with knowledgeabel use I think this can be utilized safely.

I built a new shorter tee link for my Avid + flap control so I am just waiting for some warmer spring temps to put it in and change the flap limit. I will try it at altitude first though; I don't see any answers by someone who has tried it. Sure would like to though. dunno.gif

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Posted

stirthepot.gif

Randy,

The control reversal could also be caused by the excessive drag caused by the lowered flaperon. When most flaps are used they go from a point of creating lift to aid in maintaining flight at very low air speeds, to one of creating drag because of their very large deflection. When we lower lower the flaperons beyond the recommended amount and then feed in needed aileron to lift a wing or turn a bit, the wing we expect to raise and assist in the turn, will suddenly be in a situation of being subjected to excessive drag. Thus,feeling and acting,like the controls have been reversed, because the wing that you expect to raise and move ahead, if you're using rudder too, pulls back and down. At least this is how I remember Steve Winder, I think, explain it years ago. Does it make sense?

I'm really interested in seeing how the shortened "T" link helps the flap lever throw. If you want a hand with the installation and rigging, give me a holler.

Jack

to

Chris,

Those are my thoughts and understanding exactly. Control reversal has to be the result of stalling one flaperon when it is deflected too far. With pure flaps that isn't too much of a concern but with flaperons we depend on them for aleron control as well so we have to be consevative so they will not cause reversal at full aleron deflection. I think knowledeable use of them in calm conditions should allow much greter flap deployment as long as we have appropriately limitted aleron input. Based on measurements of my plane as currently set up, maximum deflection with full flaps and full stick is around 40 degrees. As long as we stay within that max deflection with any combination of inputs we should not get control reversal. Obviously in a windy/turbulent situation we would not want to put in any more flaps than the 18 degee limit because it is pretty hard to mentally overcome reactive inputs but with knowledgeabel use I think this can be utilized safely.

I built a new shorter tee link for my Avid + flap control so I am just waiting for some warmer spring temps to put it in and change the flap limit. I will try it at altitude first though; I don't see any answers by someone who has tried it. Sure would like to though. dunno.gif

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Posted

Woops, looks like I mixed my reply in with Chris' answer. Hope you see it Randy.

Jack

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Posted

Not ready to do it yet because of other projects, but I think I will remove the flap travel limit on my magnum and go up and do some mock approaches at high altitude and see if I can get the reversal thing to happen with greater flap deflection. I should also be able to see the effect on aileron authority with increased flap travel as well as if I can initiate reversal. Will report back to this thread once I do that. it may be a little while until I get to it, but it will be nice to know what exactly happens at what deflections.

I can't imagine this being a particularly dangerous experiment if done with adequate altitude fully expecting odd behavior. If anyone disagrees and believes this is an accident waiting to happen please speak up and say why! :stirthepot:

Chris

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Posted

Not ready to do it yet because of other projects, but I think I will remove the flap travel limit on my magnum and go up and do some mock approaches at high altitude and see if I can get the reversal thing to happen with greater flap deflection. I should also be able to see the effect on aileron authority with increased flap travel as well as if I can initiate reversal. Will report back to this thread once I do that. it may be a little while until I get to it, but it will be nice to know what exactly happens at what deflections.

I can't imagine this being a particularly dangerous experiment if done with adequate altitude fully expecting odd behavior. If anyone disagrees and believes this is an accident waiting to happen please speak up and say why! :stirthepot:

Chris

Do it! I am going to play with mine tomorrow if the wind lays down. I would love to have more flaps! Just be ready on the rudder and you should not have any big surprise.

:BC:

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Posted

Do it! I am going to play with mine tomorrow if the wind lays down. I would love to have more flaps! Just be ready on the rudder and you should not have any big surprise.

:BC:

That's what I'm thinking! Thanks!

Chris

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Posted

I reworked my flaperon linkage the other day; installed a shortened TEE link in the Avid+ and increased the full flap deflection fron 16 degrees to 28 degrees. I didn't get a chance to fly it until this weekend after I switched back to wheels. I didn't get any feeling of control reversal with full flaps but I didn't try any full stick deflections while at full flaps. Mine seems to put in some roll component at full flap deflection but it might be due to the fact that I had to offset tthe TEE link slightly and caused the connector links to flaperon L levers (not sure of the name) to be set at different lengths. Not a big deal but just had to compensate with stck or back off on the flaps a little. It does help the fat Avid get off the ground better and land slower.

I know this is exceeding the flaperon travel recommended in the Avid manual so I am not encouragng anyone else to do it; just noting my observations.

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Posted (edited)

Can't wait to hear how it goes. Would you mind posting a pic of what you modded? I do not have a good visual image.

Thanks!

Chris Bolkan

Edited by ChrisB

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Posted

Would you mind posting a pic of what you modded?

^this

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Posted

I know its a bit of an old post but im curious to see pics/ results of your modifications to the flap lever. And just as a side note the kit im working on has the old B style flapperon mixer and im wanting to upgrade it to the under the seat / cable design. I think i can easily fab up the parts but im wondering if i can get some really good pics w measurements of this mechanism especially the rear bell cranks F7A? and the F1? control tube.

Thanks

Robert

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