Sky pup?

[Vigilant1]

Personally, I’d love to see a side-by-side two-seater in wood/foam/fabric with tricycle gear and air brakes or flaps to eliminate the major issue with two-axis controls—adjusting the glide path on final without the being able to slip.

That's one issue, but you'd still have no good way to get the airplane aligned with the runway if there is a crosswind. Both "wing low" and "crab" aren't in the toolbox anymore if bank and heading change always come as a linked pair.

 

[BJC]

Having the aileron actually change the angle of attack of the wing, not just relative AOA, would be entertaining to watch fly.

Right, but I hate to see crashes.


BJC

 

[BJC]

That's one issue, but you'd still have no good way to get the airplane aligned with the runway if there is a crosswind. Both "wing low" and "crab" aren't in the toolbox anymore if bank and heading change always come as a linked pair.

Yup, the designer commented that, like any other light wing loading ultralight, it is not intended to be flown in windy (relative to the airplane) conditions.

It is a well thought out design that meets its goals. Leave it alone. Design something new using it for inspiration if you want something different.


BJC

 

[Gary Hogue]

How about the addition of Cousandy flaps ala the Pou du Ciel? Koen of nestofdragons.com has elaborated on that here.

 

[cluttonfred]

How is the Sky Pup different from any other two-axis craft in that respect? Ercoupes have been landing crabbed for 80 years. What I have in mind is effectively a microlight, high-wing Ercoupe about 1/3 lighter than Fred Weick’s classic so about J-3 weight.

Also, for the ultralight Sky Pup, while any part 103 ultralight is challenging in strong wind, the resulting ground speed is so low you can likely just land across the runway in a pinch.

That's one issue, but you'd still have no good way to get the airplane aligned with the runway if there is a crosswind. Both "wing low" and "crab" aren't in the toolbox anymore if bank and heading change always come as a linked pair.

 

[ragflyer]

How is the Sky Pup different from any other two-axis craft in that respect? Ercoupes have been landing crabbed for 80 years.

Rudder two axis are a little different to ercoupe style aileron-rudder linked airplanes. As you point out in both types of airplanes, if they are tricycle geared, you fly final pointed to the wind and land crabbed and the stout tricycle gear automatically aligns with the ground roll due to its CG position. No need to slip.

However on a Ercoupe you have direct control of the two axis that are critical close to ground- ground track and roll axis. If the wing drops close to ground in the Ercoupe you can directly (rapidly) pick it up with ailerons or if you need to align with runway you can turn with ailerons and linked rudder. You have direct control in both cases. The Ercoupe after all uses control surfaces on all three axis even though the pilot control two of them together and so cannot cross control to slip/skid.

On a rudder airplane you pick the dropped wing and turn to align with runway indirectly as the only direct control is yaw. This can make a difference when you are close to ground in gusty conditions and need rapid control response.

All in all many 2 axis rudder planes have been and continue to be flown safely but all things being equal they provide a little less (rapid) control in landing than an Ercoupe. I am a big fan of rudder two axis planes for fun UL flyers.

 

[ragflyer]

I should add to my earlier post ...on a tail dragger things are the other way around. There is a benefit of rudder style two axis machines with direct yaw control rather than Ercoupe which has to land crabbed and will ground loop if it where a tail dragger. On a sky pup and other 2 axis tail draggers direct yaw is critical to give you a shot at aligning with the runway in the last second. You cannot do this in an Ercoupe style airplane.

 

[cluttonfred]

I had not thought of potential differences between combinations of rudder vs. aileron two-axis control and conventional vs. tricycle gear before. Powerful rudder control may explain why Mignet types often get away with conventional gear, though the ability to “plant” the main gear with forward stick (negative wing incidence) also helps.

 

[Protech Racing]

Lots of Fleas get spun out while taxi testing. They do not like high speed taxi runs. AS they slow down , drop the tail,they get assy. AS pilots get more time and confidence , they simply WOT and fly off. When landing, the are easy to tail wheel drag and slow easy under control MOL.
The best way to taxi is too blast the power on the rudder and get the proper direction. Just enough speed to get to lift off point. WOT to pattern alt.
My Tandem wing was tri gear and everybody flew it easy peasy.

 

[Marc W]

Just saw this on Craigslist for anyone looking for Skypup plans: SKY PUP Construction Drawings - aviation - by owner - airplane...

 

[Turd Ferguson]

Quicksilver built 1000's of 2-axis ultralights.

 

[Victor Bravo]

Yes they most certainly did, and apparently they're perfectly safe when flown within their low wind/turbulence limits.

 

[TLAR]

I don’t see a problem with trying to get a very lightly loaded wing to behave in a limited crosswind, probably won’t be successful, I do like the two stick French flap, but thinking it through would end up being heavier than ailerons.
How big do the ailerons need to be?
To have a chance of being effective they’re gonna have to be large.
It would really be nice to have a clean strut free ultralight

 

[TLAR]

Thanks Mark W
I was able to get those plans from Richard. Nice clean original set!

 

[cluttonfred]

Here's a neat clip showing a Sky Pup dealing with some rough air and showing how quick rudder input can translate into roll. Like I have said before, it's a cool design if you are not too heavy, just leave it alone, build it per the plans, and respect its limitations (like those of a any true ultralight) and you will have a lot of fun.

PS--There are also quite a few small paramotor engines that should do very well on a Sky Pup, more power for less weight than the old school options.

 

[TLAR]

Thanks for the video, it’s a great looking ultralight.

 

[Dewey Vicknair]

I have a set of Sky Pup plans and have studied them fairly well.

The only negatives I can think of is it would be a fair weather flyer, very light winds and cross wind capability like the early ultralights and relatively large for storage. You wouldn't want it left outside in the weather.

On the plus side there are many, low cost materials, low hp (less expensive) engine, proven track record, decent plans and probably a network of builders and former builders for support.

All in all a valid project with a decent chance of having a good flyer when complete.

All ultralights, by design, are fair weather fliers.

 

[Dewey Vicknair]

For a 60mph wing, no

Nah, it'll be fine. I wonder how often "That looks about right" are the second to last words.

 

[pwood66889]

Very Inspiring Video, Matthew! Had missed that = Percy