Leading edge slats and Keller Flaps

[RaisedByWolves]

Wonder if the hinges will bolt on like a cub kit. I saw airframes came out with husky aluminum struts


This one has slats..

https://aviataircraft.com/wp-content/uploads/2022/05/Stu_AviatAircraftSpecSheet_n55wy.pdf

 

[Steve Pierce]

Wonder if the hinges will bolt on like a cub kit. I saw airframes came out with husky aluminum struts


This one has slats..

https://aviataircraft.com/wp-content/uploads/2022/05/Stu_AviatAircraftSpecSheet_n55wy.pdf

Took some pictures of it at the Texas STOL Round-up at Hondo, TX several years ago. https://photos.app.goo.gl/vd2ivV8Q9Crw2xKD8

 

[flagold]

Took some pictures of it at the Texas STOL Round-up at Hondo, TX several years ago. https://photos.app.goo.gl/vd2ivV8Q9Crw2xKD8

Those are automatic?

 

[JohnnyR]

LLD-
Curious if you finished your "experiment" and have some input on changes in flight characteristics.
Thanks,
J

I have a Javron wing and a set of leading edge slats to fit. My wings also have Keller flaps. I’m planning on initial flying without the slats fitted, so I have some base line performance figures to compare. I intend to try maybe fitting some platenuts as the attach for the slats rather than screws. So they are removable if I decide to when on floats. I’m concerned on chaffing the fabric leading edge at the attach points any ideas on mounting options for this leading edge system.

 

[DENNY]

Advice I received from another pilot was to leave the inboard few feet of the wing without slats so it is easier to fuel. DENNY

 

[john schwamm]

Gary,
We had two Helio's at Valhalla Lodge one on wheels and one on floats. They are fantastic airplanes, however because the slats are spring loaded so controlled by your forward speed, they work perfectly in the three point position. However on floats that is NOT the case, by the time you are on the step your deck angle is so flat to be in the slippery spot on the floats, you have sorta hung yourself as the slats have retracted into the leading edge
So you basically have a 2300lb; 295 hp Tcraft (similar wing profile) With big flaps.......... So it's still about same as a good 206 on 3430's........ The exception to this is in 'bigger waves' and lite, because of the "ramping effect" of the wave T/O could be done while riding up the front side of a wave while the slats were still fully extended. Showing the true potential
of the wing working correctly. While speaking with Dennis Branham (old time Helio family in Alaska) about this problem; with slats on floats, he told me, they had explored the possibility of a rear strut that could be shortened for T/O and extended for climb and cruise. But could never figure out how to do that. LoL
I have some old movies of Helio T/O from 80's in Nushagak River using the waves as ramps and you could
Get off in 100/150' as you went out thru the top of the wave because of the high AOA you had and slats doing their job! Of course the slats work the same for landing on
floats as on wheels; So that's not an issue. But most folks that have not flown them; have no idea, how increadably soon, you can start a STEEP turn in a Helio, to avoid an obstacle, You can be in a very short spot, with tall trees at end, or steep rising terrain, and if there is a gap either side to escape; the Helio can turn very steep safely, where other wings can NOT. Hope this helps
with the floatplane question.
And when Pete says he beat Bob Bryant in the Helio, he forgot to mention he also beat the " hottest Cub" in Maine
As well !!!! Moral of the story: Don't mess with Pete in a "Twin Bee"!!!
E

Turbo,
The Helio slats are not spring loaded! they are controlled by airflow only, come in and out at about 55mph.
Kirk bought the one Helio which was previously mine for Valhalla Lodge. Had several Helios over the years, best shortfield airplane of its size for sure.
If the wind is blowing at least 28mph they can hover..
With the flaps full down and slats out the wing area is doubled, so lot of lift, but drag too. Airfoil is same as P-51.
John

 

[TurboBeaver]

Thanks John! I always thought there must have been a lite spring behind them. So your saying the only reason they come back out if you push them in against the leading edge, is the angle of the shaft and gravity?
I agree completely on hovering into a big wind. Bob Curtis
used to luv telling about being down at Cold Bay in spring bear hunting. He claimed as soon as it going; puffing 35 plus,( about any day down there lol.) He would regularly get his Helio out and come in by the Cub guys slow up to a hover and then "BACKUP" show em what a Courier can actually do!
Fly safe John
E

 

[Steve Pierce]

Advice I received from another pilot was to leave the inboard few feet of the wing without slats so it is easier to fuel. DENNY

The latest out of Legend Aircraft is that slats in this prop wash area does nothing and contributes to the speed loss in the addition of the slats cause.

 

[flagold]

The latest out of Legend Aircraft is that slats in this prop wash area does nothing and contributes to the speed loss in the addition of the slats cause.

I could see how that would be true.





From what I've seen, the designs following the Rallye and Helio are the best of the best (weighted independent operation).

 

[stewartb]

As already stated, Back Country’s slats end 16” from my wing root. On those wings my last VG is about 20” out. My point being that there’s a relationship between VGs and slats. My Cessna’s STCd VGs end much closer to the wing root. Contrary to what I’ve read on this site, neither plane is difficult to fuel. FWIW my Cub with 35s will go 100 mph, so not slow, but it’s more comfortable to cruise at 85-90 mph.

If I look at the flight attitude and project the prop disc of my 80” prop, I don’t think prop wash is an issue at 16” out. Only important if it matters, and I’m not sure it does. If prop blast did anything to slats I’d expect it to keep them closed with high thrust throttle. That would impact the slow end, not the fast end. Where are Helio slats located in reference to wing root?

 

[flagold]

As already stated, Back Country’s slats end 16” from my wing root. On those wings my last VG is about 20” out. My point being that there’s a relationship between VGs and slats. My Cessna’s STCd VGs end much closer to the wing root. Contrary to what I’ve read on this site, neither plane is difficult to fuel. FWIW my Cub with 35s will go 100 mph, so not slow, but it’s more comfortable to cruise at 85-90 mph.

If I look at the flight attitude and project the prop disc of my 80” prop, I don’t think prop wash is an issue at 16” out. Only important if it matters, and I’m not sure it does. If prop blast did anything to slats I’d expect it to keep them closed with high thrust throttle. That would impact the slow end, not the fast end. Where are Helio slats located in reference to wing root?

I'd like to know how often the Helio pilots see that root slat come down.

 

[john schwamm]

View attachment 62155

I'd like to know how often the Helio pilots see that root slat come down.

Slats are out at about 55mph, they can dance in and out with wind and when turning inside ones are going in and out with tighter turning radius on inside wing if at the 55mph range.
They can slam out in strong winds and are a pretty loud bang.
In runup the inside left one can go in a bit.
John

 

[skywagon8a]

View attachment 62155

I'd like to know how often the Helio pilots see that root slat come down.

Here is a video which shows the slats moving independently from each other. As you can see, the slats do dance depending upon their local angle of attack.

 

[stewartb]

I recall the first time I rode in a Helio. I jumped when the slats came out with that bang they make. Helio slats are very different from Mackey slats.

 

[john schwamm]

Here is a video which shows the slats moving independently from each other. As you can see, the slats do dance depending upon their local angle of attack.

You can also see the interceptors coming out at top of wing when full aileron control is used to spoil the lift on either wing as needed to maintain flight level control.
Helio magic most never see.
John

 

[stewartb]

Do the slats create a pitching moment or do the spoilers cancel that?

 

[flagold]

Slats are out at about 55mph, they can dance in and out with wind and when turning inside ones are going in and out with tighter turning radius on inside wing if at the 55mph range.
They can slam out in strong winds and are a pretty loud bang.
In runup the inside left one can go in a bit.
John

Thanks for that. The guys we had practicing were always in T.O. & landing config. so I didn't get to see the inside slats doing their thing, but that must've been the loud bang on base to final. When the wind got up from the sea breeze at Ormond they could hover as pointed out.

Just so I'm clear: if you're in a tight turn around 55 - the outside slat on the inside wing is already out before the inside slat deploys (I take it).

 

[john schwamm]

Do the slats create a pitching moment or do the spoilers cancel that?

No pitch at all, interceptors only spoil lift on wing that needs lift killed to maintain level control at slow speed. They only come out with full aileron deflection. One wing or the other only.
John

 

[john schwamm]

All slats controlled by speed/airflow at about 55, so random when down at those speeds. Winds and turns can speed up or slow down airflow, so can be random.
John

 

[flagold]

All slats controlled by speed/airflow at about 55, so random when down at those speeds. Winds and turns can speed up or slow down airflow, so can be random.
John

Thanks for that. Was in and out of a lot of stuff, but one of my regrets is never getting ahold of a Helio or 235C Rallye.

 

[JohnnyR]

Stewart, did you ever run your experimental with no VG’s?
Currently I am planning to install nut plates on our Legend build but not slats or VG’s, fly it for a season, then put on slats and do another season, then glue on the VG’s. That would historically be about 450 hrs of flight data with which we’d make some assessments.

 

[stewartb]

Yes, I flew it with slats and no VGs in the initial hours but I didn't "test" anything. Those hours were high power with no slow flight other than landing. After the first engine was recalled I was bored while waiting for the new engine so I spent an afternoon applying VGs. Every SQ owner I know has VGs and I watched how those planes performed and wanted the same.

 

[RaisedByWolves]

Almost all of my supercub time is with vg’s. I was being a 90hp cub into our strip with a crosswind, was carrying a little extra speed because of the crosswind. The wind dropped the wing, and I used the aileron like I’m used to. The wing didn’t move. I’d say vg’s help for sure.

I put a set of slats, and pstol flaps on a smith cub. Wide body 160hp. Extended wings, flaps and ailerons. The owner loves the flaps, he just took the slats off. Said if he was to do it again he would do pstol and not the slats. The cub is really slow in cruise. It has vg’s as well.

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[stewartb]

When I was investigating adding VGs I looked for advice. I messaged Jerry Burr to ask about the slat-VG relationship. I asked about where to install VGs to best enhance the slats. Jerry replied that I had it wrong, slats energize the VGs. He told me to dismiss the noise and buy the VGs from Back Country and install them where they advised because they had been tested and they worked. I respected the advice and did exactly that.

 

[JohnnyR]

I wanted our 16 y/o to get some time under her belt flying a regular wing, then add in the extras so she has a baseline for understanding and appreciating the differences.

Problem is the VG’s need to go back a few inches further when mounted with the slats compared to regular positioning (can’t expoxy in conventional location and then move them back).

Not sure what/how much the VG’s would do if mounted rearward on a regular wing.

 

[stewartb]

Use VHB tape. Moving them would take some effort and care but doable. I’ll never use the glue again.

 

[stewartb]

I put a set of slats, and pstol flaps on a smith cub. Wide body 160hp. Extended wings, flaps and ailerons. The owner loves the flaps, he just took the slats off. Said if he was to do it again he would do pstol and not the slats. The cub is really slow in cruise. It has vg’s as well.

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The only way that makes sense to me is if your customer doesn’t like to fly on the back side of the power curve. Ultimately that’s where slats do their work. Some guys will comment that slats allow silly high AOA. That may be true if demonstrating level flight AOA, which we all saw on early slat videos, and keep in mind those videos had shorter, standard flaps. Wings have evolved. Keller flaps allow the same speeds with a lower AOA. Translate that flight attitude to approach to landing and rotate the nose down. The relative wind is the same. Keller flaps at 50+° provide considerable drag, and that’s a good thing in that technique. Slow, steep, and the top of my wing is still fully engaged, making lift, and the ailerons are responsive. Attitude controls speed, thrust controls descent. Nothing is different about that. The wing’s ability to maintain control at that speed in that attitude is very different. If a guy isn’t comfortable in that configuration, the slats are just along for a ride.

 

[RaisedByWolves]

The only way that makes sense to me is if your customer doesn’t like to fly on the back side of the power curve. Ultimately that’s where slats do their work. Some guys will comment that slats allow silly high AOA. That may be true if demonstrating level flight AOA, which we all saw on early slat videos, and keep in mind those videos had shorter, standard flaps. Wings have evolved. Keller flaps allow the same speeds with a lower AOA. Translate that flight attitude to approach to landing and rotate the nose down. The relative wind is the same. Keller flaps at 50+° provide considerable drag, and that’s a good thing in that technique. Slow, steep, and the top of my wing is still fully engaged, making lift, and the ailerons are responsive. Attitude controls speed, thrust controls descent. Nothing is different about that. The wing’s ability to maintain control at that speed in that attitude is very different. If a guy isn’t comfortable in that configuration, the slats are just along for a ride.

He runs out of fuel using them to climb, doesn’t have the aoa at take off to use them, and 15mph slower. He’s comfortable with the airplane for sure. I have heard a lot of the legend guys took the slats off. I would imagine you can get in much shorter than you can get out? He did say it was safer horsing around, that was the upside. Just passing along what he told me.


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[skywagon8a]

Has anyone done a direct comparison between the "screw-on" exposed LE slats and the Dakota built-in slot? Performance and cruise drag in particular?

 

[stewartb]

Like with any airplane mods, the biggest factor is the pilot, and I’m far from the best. For me? Takeoff performance is equally as excellent as landing with slats and Kellers. The longer the flaps the better in both cases. Mackey airplanes demonstrate that. For takeoff the more important factor is thrust. Horsepower and a good prop are what makes it go. I understand the ground AOA comment, but for me that mostly applies to scrubbing speed to land. I can bump my tail pretty hard if not slow enough on final. I switched to 6” gear to improve my goof margin. But similar to my Cessna, more flaps reduces the takeoff roll and deck angle for climbing out. It just requires power.

To that topic, BCSC Rev 3 flaps create less drag and more lift. Pireps for that wing are that landings are a little longer and takeoffs a little shorter. That from a friend who’s had 12’ Kellers and 12’ Rev 3s on the same plane. Wing evolution is fascinating to watch.