Super Cub retractable leading edge slat

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

Wrongway John

Well-Known Member
Joined
Dec 8, 2005
Messages
230
Location
Wichita Falls, TX
SuperCub uses a retractable leading edge slat on their wing that still lets them fly at around 20 mph. I believe there are no complex cables and controls involved. It works on air pressure, and under 60 mph, it opens up, while speeds over that, it retracts which gives considerably more top end airspeed and economy. Many STOL aircraft didn't won't to use retractable leading edge slats due to it often making the system much more complex, but this doesn't appear to be the case with these. Their site doesn't seem to have too much in the way of details from what I've found thus far, but I'll keep looking. I'm guessing this is accomplish through springs? Anyone know?

I wrote Wayne at SuperCub, who said although the Zenith aircraft hasn’t ever contacted him, he says it would be a fairly simply process to adopt them to their planes as well.

Might give the Zenith 701, 750 and 801 crowd, and other STOL aircraft something to think about.


Backcountry SUPER CUBS - SUPER CUB Slat Kit information Page
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,614
Location
Corona CA
Those are not retractable slats, though, they appear to be fixed. A retractable system does involve a lot more complexity and the airfoil and slat airfoil need to be matched. I was always impressed with the Helio Courier system, which does retract and extend automatically, in separate inboard and outboard sections.
 

autoreply

Well-Known Member
Joined
Jul 7, 2009
Messages
10,765
Location
Rotterdam, Netherlands
SuperCub uses a retractable leading edge slat on their wing that still lets them fly at around 20 mph.

I've often seen hilarious exaggerations of stall-speeds. Manufacturers often claim impossible numbers and this is just another one. 35 mph seems realistic. Below 30 is probably fantasy (or a wrongly placed pitot)
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,614
Location
Corona CA
Indeed. 20 mph groundspeed against a 20mph headwind in videos usually. Whatever the ASI says, counts!

Still, they show impressive slow speed handling, whatever the actual speed may be.
 

Wrongway John

Well-Known Member
Joined
Dec 8, 2005
Messages
230
Location
Wichita Falls, TX
Tom, glad you liked it.

PTAirco, I’ve heard others refer to it as a retract, but maybe that isn’t the best word to describe it. Don’t think it could be described as fixed either, since it does fold down Here’s a better pic of one comparing the system similar to Helio’s which they say were a spring loaded leading slat.

http://www.flickr.com/photos/themulder/3503281826/

Here’s a really cool experimental Super Cub video getting in and out of something that very few planes could. It didn’t have the slats, but gives an idea of how slow they go even without ‘em. Gotto love those tundra tires too.

http://www.youtube.com/watch?v=ucdb0TKu3rk&feature=related

In those trees and mountains, there couldn’t have been too much of a strong wind. I’ve read from other sites that are using the leading edge slats and VG’s on the Super Cubs that are claiming even more amazing results. It’s difficult to substantiate, but one thing is for sure, they don't need much runway at all.
 

WWhunter

Active Member
Joined
Mar 2, 2011
Messages
38
Location
Virginia/Minnesota
autoreplay,
I think I would do a little more research before I made a statement such as you did. How about you contact Wayne Macky and have a talk with him about his plane. I am not saying one way or another that his speed is below 20 but he is not one to exagerate. I have seen the plane in question and he KNOWS how to fly it.
WW
 

Joe Fisher

Well-Known Member
Joined
Feb 10, 2007
Messages
1,379
Location
Galesburg, KS South east Kansas
I worked on T39 Saber Liners they have leading edge slats that roll out on curved tracks. There are no springs or controls. When the airplane is parked they just hang out and you can just push them back in with a light touch. I was told that the F89 used the same system.
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,614
Location
Corona CA
Tom, glad you liked it.

PTAirco, I’ve heard others refer to it as a retract, but maybe that isn’t the best word to describe it. Don’t think it could be described as fixed either, since it does fold down Here’s a better pic of one comparing the system similar to Helio’s which they say were a spring loaded leading slat.


Ah, I see; it looks like a slat that is able to pivot and adjust itself to the airflow within certain limits. Still doesn't give the low drag advantage of a fully retractable slat though.
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,614
Location
Corona CA
Man, these Super Cub guys, are HAPPY guys! :gig:
Last week, I was practicing short field landings in a 90hp J3. I pulled off one that was so textbook perfect, so satisfying that I almost got out on the runway and did what those guys were doing! I may never do one like that again for the rest of my flying career, but I can say i did it once...
 
Last edited by a moderator:

Voyeurger

Well-Known Member
Joined
Oct 9, 2010
Messages
612
Location
Northern Phoenix, Arizona, U.S.A.
Last week, I was practicing short field landings in a 90hp J3. I pulled off one that was so textbook perfect, so satisfying that I almost got out on the runway and did what those guys were doing! I may never do one like that again for the rest of my flying career, but I can say i did it once...
I HOPE you had witnesses to give you an "attaboy". And sure you will do it again, more often likely.
 

autoreply

Well-Known Member
Joined
Jul 7, 2009
Messages
10,765
Location
Rotterdam, Netherlands
autoreplay,
I think I would do a little more research before I made a statement such as you did. How about you contact Wayne Macky and have a talk with him about his plane. I am not saying one way or another that his speed is below 20 but he is not one to exagerate. I have seen the plane in question and he KNOWS how to fly it.
WW
I don't have to contact him. 20 mph stall would mean a lift coefficient of 6.7 or so if it's soloed, no-fuel. At MTOW we're looking at even more hilarious claims, over 10. The guys at Boeing spend billions in surpassing 3-3.5. Do you really think this guy can just ignore those physics?

High Lift Systems: Introduction

I don't have anything against these slats. But exaggerated claims do ring a bell to me, especially if they're so overdone.

[video=youtube;h-9RPJDoC5E]http://www.youtube.com/watch?v=h-9RPJDoC5E&feature=related[/video]
:gig:
 
Last edited by a moderator:

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
14,692
Location
Memphis, TN
Unless the have a special calibrated pitot/ gauge for this low of a speed any reading below 30, I would be really suspect. CAFE needs to do a test on some ones plane. I know from our helicopters below 40 indicated with high angles nose up or down from level or yaw you can make the airspeed move 20.
 

PTAirco

Well-Known Member
Joined
Sep 20, 2003
Messages
3,614
Location
Corona CA
Since most of the ASI error is due to the pitot angle to the airflow, why don't we have pivoting pitot tubes on aircraft that always align themselves with the slipstream? It's not exactly rocket science, but I wonder how much of the error is also due to an inherent lack of accuracy at low air pressures. Lindbergh had a rotating cup style of ASI on his Ryan when he flew the Atlantic, as it was far more accurate than the usual pitot type.
 

autoreply

Well-Known Member
Joined
Jul 7, 2009
Messages
10,765
Location
Rotterdam, Netherlands
Since most of the ASI error is due to the pitot angle to the airflow, why don't we have pivoting pitot tubes on aircraft that always align themselves with the slipstream? It's not exactly rocket science, but I wonder how much of the error is also due to an inherent lack of accuracy at low air pressures. Lindbergh had a rotating cup style of ASI on his Ryan when he flew the Atlantic, as it was far more accurate than the usual pitot type.
It's not just the pitot.
I've read a lot of Dick's pirep's and usually the variations are rather big.

*Static holes placement is usually sub-optimal. You want to keep them dry and in a place you can access. The fuselage/wing flow influences them too.
*Same for pitot placement.
*Good pitots are vulnerable. You need something that is pretty long, sticking out of the wing/fuselage. People will hit it, unless you put them over the tail, which is useless for a tractor engine.
*Accurate speed indication at (low) speeds is irrelevant. Aircraft are certified with their standard pitot and static and the markings for stall, flaps and so on are based on that. If you're indicating 20 mph at stall, that's just fine if you're actually doing 35, as long as you (or the markings on your asi) know that.

A solution for the high aoa problem might be a glider specific one. Normally, they compensate slip (the open class ships slip quite a lot in thermalling). If you turn the arms vertical it'll compensate for aoa. Don't forget to reverse pitot and static :gig:dn-st1.png
 

Wrongway John

Well-Known Member
Joined
Dec 8, 2005
Messages
230
Location
Wichita Falls, TX
It would be interesting to hear what Orion has to say, and whether or not he thinks Mackey has achieved the MCA that he claims. For others interested in these slats, Mackey says these particular ones he uses were invented by Handley Page some 80 years ago, and they are easily fitted to many aircraft.

I don't have to contact him. 20 mph stall would mean a lift coefficient of 6.7 or so if it's soloed, no-fuel. At MTOW we're looking at even more hilarious claims, over 10. The guys at Boeing spend billions in surpassing 3-3.5. Do you really think this guy can just ignore those physics?

High Lift Systems: Introduction

I don't have anything against these slats. But exaggerated claims do ring a bell to me, especially if they're so overdone.
There are many things that obviously need to be accounted for, and I wouldn't know how to do all the necessary calculations that would need to be involved that would accurately account for everything. I'm sure you know more about it than me. But I don’t think Mackey is ignoring physics. Strong headwinds can make almost any plane look good on take off and landing, but Mackey isn’t relying on that for his figures. Cold air also helps. And obviously, MTOW is going to be higher numbers, but I don’t think anyone here or Mackey has used MTOW to make this claim for his minimum controllable airspeeds. At 1800 lbs, still not MTOW for his plane, but a fairly good load, the EAA article below reports 26 mph minimum controllable airspeed. His gross weight on his Cub is 2,200 lbs, so obviously the numbers would go up even more in this setting than the 26 mph figure. But at 1450 lbs, the minimum controllable airspeed given is at 18 mph. He used many modifications to achieve this. Some of the major ones are the slats, longer wing span, and VG’s.

http://www.eaa.org/sportaviationmag/2010/1007_Backcounty.pdf

You claim such figures are hilarious exaggerations of stall-speeds, and that anything below 30 is probably fantasy or a wrongly placed pitot. Mackey or any other isn’t going to rely on a pitot tube for minimum controllable airspeed numbers in these planes, simply due to the AOA. There are many of these Mackey squared videos you can look at on youtube, where the tailwheel is inches from the ground, and the Cub is coming in at a very steep AOA. So unless the winds are stronger that what I imagine, or they have altered these videos, it seems pretty convincing that Mackey’s Cub numbers come in at the MCA he is reporting.

It’s difficult to judge wind speed from many of these youtube clips I’ve seen, but judging from the trees and other vegetation and also bodies of water that are shown, it looks to be light or almost dead calm winds. I could be mistaken about this, however. But in many of those scenes that are being shot for over 10 and 20 seconds at a time, the tailwheel is inches away from the ground. For the time being, anyhow, he’s at least successfully demonstrated to me that he can fly with MCA in a dead calm wind at about 20 mph.

So unless they are using trick photography, editing the scenes to look like no wind, using other deception, or there is something else that I’m missing, it doesn’t seem like a fantasy at all that his planes can not only still fly under 30 mph, but 20 mph is probably the more accurate figure.

For entertainment value, I think others will get a big kick out of what this guy did with this Super Cub. One of the funniest video's I've ever seen. Gotto watch how it ends too. :gig:

YouTube - Drunk pilot.... Piper super Cub What a great pilot!
 

autoreply

Well-Known Member
Joined
Jul 7, 2009
Messages
10,765
Location
Rotterdam, Netherlands
There are many things that obviously need to be accounted for, and I wouldn't know how to do all the necessary calculations that would need to be involved that would accurately account for everything.

Basically, it's just Bernouilli. Here's a handy calculator:
Airplane Aircraft Wing Lift Design Equations Formulas Calculator - Coefficient
I've used:
Lift: 1400 and 2200 lbsf
Density 1.225 kg/m3
Wing area 16.5 m2 (178 sqft)

Lift coefficient @ 1300 lbs, 20 mph = 7.15
Lift coefficient @ 2200 lbs, 20 mph = 12

Typical is 2.0 with simple and inefficient flaps, 3 with very effective flaps (Fowler, slotted) and 3.5-4 for the most advanced systems (triple slotted flaps with slats)
He probably gets some lift from the prop as well. Statical thrust is (just a wild guess) probably in the order of magnitude of 500 lbs.

At 1800 lbs, still not MTOW for his plane, but a fairly good load, the EAA article below reports 26 mph minimum controllable airspeed. His gross weight on his Cub is 2,200 lbs, so obviously the numbers would go up even more in this setting than the 26 mph figure. But at 1450 lbs, the minimum controllable airspeed given is at 18 mph. He used many modifications to achieve this. Some of the major ones are the slats, longer wing span, and VG’s.

A decrease in weight from 1800=>1450 would yield an 11% lower speeds, so 23 mph, not 18. To get from 26 to 18 mph, you would need to loose half of your weight.

Not trying to be the wise-ass, just trying to warn for exaggerated numbers.
 
Top