Reflex Ailerons?

[Jim Meade]

There has been considerable discussion on this forum about the difference between 6° and 12° reflex flaps.  I have two questions about ailerons:

1.  For those flying CTSW with legal, original 12° reflex flaps, what is the reflex on the ailerons?  Are they set to a higher angle than on the 6° flap planes?  I'll see if I can find any European maintenance manuals but if you have personal experience I'd be glad to hear it.

2.  For those who have flown CTSW with 6° reflex flaps that were modified to 12° flaps, did you change the pitch on the ailerons or fly with the factory setting?  If you flew with the original, factory setting ailerons, what was your experience in stall characteristics flying a wing where the root was at 12° and the tip was at 6°?  Any tendency to stall at the tip before the root?  Any recovery issues?

Direct factory references or personal experience especially anticipated.

[Tom Baker]

Just for conversation purposes, the reason we don't have -12 flaps here in the states is because it takes it out of the LSA category because of the clean stall speed being greater than the 45 knots minimum.

 

[Roger Lee]

1 hour ago, Tom Baker said:

Just for conversation purposes, the reason we don't have -12 flaps here in the states is because it takes it out of the LSA category because of the clean stall speed being greater than the 45 knots minimum.

 

I have changed 4 CT's to -12 and tested them against -6 Ct's. It really didn't take it over 45. I could still land less than 45. That said I wasn't impressed with the change and it didn't fly any faster than others with -6. This was tested on 4 CT's. Plus you lost lift at high altitudes. I'd leave -6 alone. I also found most CT's flaps at the actual setting number. I've had to reset many to be really 15 or 30, ect... They didn't come exact from the factory.

-12 was a disappointment over all.

[GrassStripFlyBoy]

I played with this a little bit, but simply by using ability the manual flap control affords.  When driving flaps manually, my bird goes darn close to -12.  (at least -11) The normal flap selector setting is -6, just a difference in the servo travel when not using the switches / control board settings, for whatever reasons the manual actuation differs.

As Roger share, disappointing gains, maybe 2 knots difference between -6 and -12.

If you're hunting for a few more knots, the old "wash and wax" your plane line is the region we're talking here.

I'm thinking the wheel pants on SW's are ripe for an improvement too, making a full pant that covers brakes, closer to small tires, might clean up a lot of drag, that is also cantilevered out from center of thrust.

E-props appears to be hottest & easiest thing for performance gain.

 

[Skunkworks85]

I have no personal experience,  and I have looked hard for European ctsw documentation,  but looking at factory a/c with -12, it appears that the ailerons have more reflex than lsa models converted to -12.  I suspect this is why you're asking. If the factory documentation calls a different aileron setting, or a different mixing ratio, Rodgers tests would be a moot point. 

[Jim Meade]

Thanks Skunkworks85.    You know, the original question was just a simple question.  You are the one who came closest to answering my inquiry. 

For the lurkers, it is useful to review what is legal and why.  Roger's experiences are interesting and it would be helpful to see his data, though his experience doesn't address my question directly.  It sounds like neither Roger nor Darrell changed aileron settings.  A difference between flap and aileron settings could be a safety of flight issue in wind sheer or gusty conditions, wouldn't you think?  I wouldn't like the wing tip to stall first and then try to recover from an unusual attitude.

I would suggest that +2 knots is a huge improvement for the amount of expense.  Standard certificated airplanes spend thousands of dollars for a few knots increase in speed. 

Darrell, how many knots can I get by washing and waxing my airplane?  Can you refer me to some published, credible data?  Sailplanes put incredible expense and effort into a smooth surface, but they are doing 60-90 knots at a 45° bank in a thermal, not trying for 120 knots cross country.  That brings up the question of gap seals.  I've improved the gap seals on the trim tab and intend to look into gap seals elsewhere but it's not on the top of my drag reduction list.

Wheel pants may indeed be an area for drag reduction.

Bottom line - I'm still interested in any experience with the aileron settings in a -12° flap airplane.  Thanks.

 

 

 

 

[Roger Lee]

When -12 was flown side by side others at -6 they were equal. -12 did not pull ahead or go faster and at high altitude and at max weight the -12 people had to reduce flaps to zero to keep up and keep the nose level instead of sticking up in the air more. This was definitely a negative.  This also considered prop settings which was crucial to get accurate results. I had 8 CT's at my field and 4 identical. We took of side by side in pairs and flew 50 - 100 ft. apart in air for comparisons and prop pitch was the same. There is no noticeable difference in speed, temps or fuel use.

 

Bottom line it just wasn't worth it.

[Tom Baker]

9 hours ago, Roger Lee said:

I have changed 4 CT's to -12 and tested them against -6 Ct's. It really didn't take it over 45. I could still land less than 45. That said I wasn't impressed with the change and it didn't fly any faster than others with -6. This was tested on 4 CT's. Plus you lost lift at high altitudes. I'd leave -6 alone. I also found most CT's flaps at the actual setting number. I've had to reset many to be really 15 or 30, ect... They didn't come exact from the factory.

-12 was a disappointment over all.

Landing at less than 45 knots and having a power off clean CAS stall speed of less than 45 knots are to completely different things. This is due to ground effect, air compressibility, and the angle of airflow entering the pitot tube.  Besides, stall speed for normal landing would be unchanged with the change to -12° flaps.

[Jim Meade]

Without knowing the factory aileron settings of the -12° flap airplanes, we have no idea if Roger's tests were representative of a factory -12° flap plane.  Roger needs to simply publish his findings, including speeds, but the fact is that does not address my original question  - it is thread drift and belongs in a different thread.

Maybe some more -12° factory plane owners will offer more insight.

[Skunkworks85]

 

Jim, 

After forcing google to only look in Germany, and translating to wartungshadbuch, I did find an older revision of the factory settings for the ailerons on a -12 aircraft. 

My interpretation is that the plane needs to be rigged so the flaps and ailerons are at -12 as its "zero" position. Pictures I have seen of LSA a/c do not have the ailerons aligned to the flaps when converted to -12.  I would agree that the performance of an LSA CTSW converted to -12 flaps (without adjusting the ailerons), will be different than a factory aircraft with -12 flaps.

 

 

 

 

 

 

 

 

I would also like to the that parts book for a factory -12 machine and see the part number relating to the "aileron pivot number 1" and see if it is the same part number as listed in the LSA Parts manual. 

 

 

 

 

 

[GrassStripFlyBoy]

3 hours ago, Jim Meade said:

Can you refer me to some published, credible data?

Hey Jim - I've been repeating what I heard over the years, but a quick search appears to substantiate it.  Maybe that's why my SW is so fast, I keep it CLEAN!

Here's a couple that popped on the first :15 seconds of researching it:

Do Airplanes Fly Faster After Waxing Them? – Airplane Academy

"A 1997 CAFÉ scientific study tested a Mooney M20E with and without wax, documenting a 3-knot speed improvement for an aircraft that was already free of bugs, oil, etc." 

Maintenance: Improving aircraft performance, part 2 - AOPA

[Jim Meade]

Great work. '85  Can you provide the web sites you used?  i can't find them.  My German is not great, but if needed my wife and daughter can translate for me.

Thanks Darrell.  It seems cleaning the airplane lets it reach it's design and build potential as opposed to adding speed, but your point is well taken.

[Skunkworks85]

36 minutes ago, Jim Meade said:

Great work. '85  Can you provide the web sites you used?  i can't find them.  My German is not great, but if needed my wife and daughter can translate for me.

Thanks Darrell.  It seems cleaning the airplane lets it reach it's design and build potential as opposed to adding speed, but your point is well taken.

http://www.ksfv.at/wp-content/uploads/2013/04/CTSW_Flug_Wartungshandbuch_s.pdf

 

[Tom Baker]

On 11/11/2022 at 11:13 PM, Roger Lee said:

I have changed 4 CT's to -12 and tested them against -6 Ct's. It really didn't take it over 45. I could still land less than 45. That said I wasn't impressed with the change and it didn't fly any faster than others with -6. This was tested on 4 CT's. Plus you lost lift at high altitudes. I'd leave -6 alone. I also found most CT's flaps at the actual setting number. I've had to reset many to be really 15 or 30, ect... They didn't come exact from the factory.

-12 was a disappointment over all.

Just because you could land at less than 45 knots, doesn't mean the calibrated power off stall speed under standard conditions with -12° flaps is less than 45 knots. Indicated airspeed near stall speed will always read lower than calibrated speed because of the angle at which the airflow enters the pitot tube. Also in ground effect the air is compressed making the wing more efficient lowering stall speed, as compared to at altitude.

[Roger Lee]

It was done as one of my research projects. I do some every year to test claims from different companies.

[Skunkworks85]

2 minutes ago, Roger Lee said:

It was done as one of my research projects. I do some every year to test claims from different companies.

Dis you also re-rig the ailerons when you tested the -12 deg flaps? 

[Tom Baker]

23 minutes ago, Roger Lee said:

It was done as one of my research projects. I do some every year to test claims from different companies.

What kind of calibrated equipment did you use to measure the stall speed? Like I have said before I have been told by the factory engineers that the reason we don't have -12° flaps here in the states is because the calibrated stall speed with -12° flaps is greater than the 45 knot limit established by the FAA for maximum allowed stall speed in the clean configuration.

[Jacques]

hat's what my book says

[airhound]

What W&B and DA do they base stall speeds on?

[Anticept]

IAS/CAS Stall speed doesn't change with DA, and likely stall speeds are based on near max gross certificated weight.

Although to be honest, without proper calibrated test equipment, we're not going to be able to get accurate testing within a few knots.

[Tom Baker]

2 hours ago, airhound said:

What W&B and DA do they base stall speeds on?

Should be gross weight. 

[Roger Lee]

I didn't need calibrated equipment and didn't care about specific numbers. I was only comparing -6 to -12.. I wasn't looking for an exact speed. FD already did that. I took the SW and tested it in -6 for stalls and WOT. Then I took the same plane within a 30 min. time and did it again at -12. I just needed to see if there was any difference on the same instruments, stalls and WOT. Then I took and flew it at WOT against other CT's that were just -6. Then at high altitude to see the difference.

Bottom line -6 in some areas performed better than -12 and at high altitude -12 did worse when heavy.

[Jim Meade]

Well, Roger, when I read your post I see top hats and capes, white rabbits and girls sawed in half.  You seem to be talking about a hermaphrodite US configured FD CTSW where the flaps are reflexed but not the ailerons.  That is not a valid comparison with FD posted information for planes where both flaps and ailerons are configured for a -12° rigging.  Apples and oranges.  If I read you right, you're saying don't reflex (ONLY) the flaps.  I concur.  Reflex both or neither, just like FD does.  If you ever do that, please post the results.

Disavowing the scientific process is not an argument unless you are a witch doctor.

My own opinion, not being an aeronautical engineer, is that reflexing the flaps and not the ailerons is dangerous for those of us who are expecting the wing root to stall first and pilots could find that in your configuration the tip stalls first.

[Roger Lee]

2 hours ago, Jim Meade said:

Well, Roger, when I read your post I see top hats and capes, white rabbits and girls sawed in half.  You seem to be talking about a hermaphrodite US configured FD CTSW where the flaps are reflexed but not the ailerons.  That is not a valid comparison with FD posted information for planes where both flaps and ailerons are configured for a -12° rigging.  Apples and oranges.  If I read you right, you're saying don't reflex (ONLY) the flaps.  I concur.  Reflex both or neither, just like FD does.  If you ever do that, please post the results.

Disavowing the scientific process is not an argument unless you are a witch doctor.

My own opinion, not being an aeronautical engineer, is that reflexing the flaps and not the ailerons is dangerous for those of us who are expecting the wing root to stall first and pilots could find that in your configuration the tip stalls first.

I wasn't looking for that kind of specific exact data and numbers. No one said we didn't test it with adjust ailerons either. We did both. No change. Just comparing -6 vs -12. Numbers don't really mean anything for me or the other pilots. Those have too many variables and other factors you'll have to control. We only wanted an in flight side by side comparison. After 4 CTSW's and 8 years worth of using them the evidence was quite clear. Might as well leave -6 alone. There just aren't any real SERIOUS gains to be had going to -12 and there are some drawbacks. Unless people have done this type of research and seen the real time evidence it would be hard to say it was wrong 

Plus it would be hard to use just a single plane to compare in all situations. That's why we used 4 CTSW's real comparisons.

Give it a try and see what you come up with.