Sky pup?

[ryanjames170]

What's the good bad and ugly of it?

 

[lr27]

What's the good bad and ugly of it?

I've heard they have a reasonably good safety record. The plans seem quite thorough, and are supposed to have been drawn by some engineers from Cessna. Sky Pups are supposed to come out at 190 lbs empty, but I seem to recall from discussion groups that they usually come out heavier. Controls are only rudder, elevator, and throttle. They're intended for relatively low power. As I recall, the instructions say no more than 20 hp, though I think sometimes people use a bit more. I recall you're not supposed to have more than 60 lbs or so for the engine, prop, redrive etc. It does have some AN hardware and some welded bits, but in general the materials are fairly basic. For instance, you're supposed to cover it in dress lining! Mostly it's wood and Styrofoam insulation that you can get at lumber places. The wheels are from BMX bikes! If I recall correctly, the gross is supposed to be 400 lbs. The fuselage isn't all that wide, either, so if you're big and/or heavy, you may have a problem. The wings are in 3 pieces, with the center section permanently attached.

You can find lots more at machnone.com

 

[Tiger Tim]

I don't recall any weldments on the plans and can't imagine where they could be other than on the control stick, but otherwise that describes the Sky Pup pretty well. It's been a long time since I had my plans out but IIRC the build manual has you size the fuselage to yourself in a pretty clever way. Really the whole thing is full of clever and cute solutions to cut weight and complexity, it's clear that whoever designed it wasn't copying anyone else's work. For example, it has sewn fabric hinges on the control surfaces and the belly has a hole that zips open so you can step right through when getting in and out since they felt reinforcing the floor to take that strain was unnecessary weight. The landing gear is a single leaf wood spring.

 

[Turd Ferguson]

What's the good bad and ugly of it?

The only negative I can think of is there are not more of them.

Designed by an engineer. Easily made the Part 103 wt limit. Flew well on very little power, easy and inexpensive to build, even by today's standards. Steve Wood knew what he was doing.

 

[Victor Bravo]

The Sky Pup was designed by a Cessna Aircraft engineer, and is known to be a pretty good design. Definitely not a "back-yard hillbilly" design. Much more refined and engineered.

It is a two-axis control aircraft, and it has been discussed here on HBA that the wing structure may not be suitable for a simple conversion to 3 axis.

An interesting and well thought-out design. But some of the compromises or design decisions made on that aircraft will not suit some builders.

 

[Turd Ferguson]

If you have good google skills, there are picture on the interweb of a Skypup modified by it's builder to a low wing configuration. That plane may have ailerons, I don't recall.

 

[cluttonfred]

The Sky Pup is an elegant and efficient design from a time when most other ultralights lived up the "flying lawn chair" nickname. The two-axis system has its pros and cons but it is well-proven and easy to build. If you need ailerons then build something else. Note that the Sky Pup does use a conventional stick and pedals (actually a rudder bar) but the stick only moves fore and aft since there are no ailerons.

Dan Grunloh is a well-know ultralight/microlight pilot who has written for EAA's Experimenter and Sport Aviation. He built a Sky Pup in the mid-1980s and was the Sky Pup newsletter editor for many years. He wrote this to sum up his thoughts on the Sky Pup.

I have been asked to share my thoughts about the Skypup in crosswinds compared to spoiler equipped ultralights and 3-axis ultralights so here goes. Compared to all other 2-axis ultralights, it is far better for two or three reasons. It is comparable to many 3-axis ultralights for reasons you might not realize. I flew mine in the 80's and 90's along with many other types and I did just fine.

1. A higher landing speed than almost all others means the crosswind component is less. In practice it lands faster than any quicksilver.

2. The VERY low CG and wide gear with large wheels can make successful landings in conditions that wreck other ultralights (even 3-axis). They are very hard to tip over, drag a wingtip, or ground loop. The key is to land on grass, not pavement. Those big wheels will slide sideways when you land in a crab. A witness once said my wheels threw up big rooster tails of dirt as they turned and slid sideways in an extreme crosswind landing. On pavement you would pull the rubber off the wheels doing that.

3. Crosswind potential of 3-axis ultralights is just that. "Potential". You must have the skill to use it and be willing to risk the airframe. I flew with ultralights that had great crosswind potential, but the average pilot didn't want to risk it. It has been 20 years, but I estimate my max comfortable crosswind at about 12mph on grass. Have landed successfully in much more without damaging anything but the sod. In strong conditions you come to a stop at 90 degrees to the runway.

4. The choice of ultralight depends on where you fly, and what you want to do. I hangared at an airport with a wide grass runway and at one with two paved runways at 90 degrees. It takes a wide runway to land a Skypup in a crosswind. You don't want to have to hit a narrow pavement and miss the landing lights.

5. The length of runway is also a factor. I can get a quicksilver or a trike in or out of a 600-800 foot runway (some with obstacles). The Pup needs more, especially for landing.

For very short tight spots I would want a quicksilver. If you have just one paved runway it's best to have tricycle gear and full 3-axis. The Skypup can go farther on 3 gallons than any Quick can go on 5 gal. I did cross country flights up to 70 miles on my Pup. You can buy used 3-axis Quicks nowadays for $5-6 but they will be sucking fumes after 70 miles.

The biggest advantages of the Pup are; elegant design, low cost,fun to build, and VERY SAFE compared to many others. I started out with almost no training and it probably saved my life more than a few times.

You will find more articles by Dan and others on http://machnone.com and several experienced Sky Pup builders and pilots participating in https://groups.yahoo.com/neo/groups/Skypup-club/info.

The biggest shortcoming of the 'Pup is that it's just too light for most pilots at 195 lb/400 lb. Most homebuilts come out heavier than the prototype, so once you've added fuel, there's not much left for anyone but a light and trim pilot. A "Sky Pup XL" at 250 lb empty/500 lb gross (or even 300 lb empty/600 lb gross outside Part 103) using a modern paramotor engine and perhaps with tricycle gear would be an absolute hoot.

 

[lr27]

I don't recall any weldments on the plans and can't imagine where they could be other than on the control stick, ...

Oops. A quick review of the plans seems to indicate you're right about the lack of welding. But it looks like I can't edit my post.

 

[TLAR]

The Sky Pup is an excellent candidate for some updates.

 

[BJC]

The Sky Pup is an excellent candidate for some updates.

What would you do to update it, and how would you determine the structural adequacy?


BJC

 

[Mohawk750]

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.

 

[cluttonfred]

I have said before that a Sky Pup XL would be a great idea: 500+ lb gross weight (or more if not Part 103), bigger cockpit, paramotor engine, maybe tricycle gear, but same overall layout and construction method including two-axis controls.

 

[TLAR]

What would you do to update it, and how would you determine the structural adequacy?


BJC

Structure has already been analyzed and will safely handle more weight.
I’m still thinking of some updates.
Ailerons will be the first update

 

[Tiger Tim]

I have said before that a Sky Pup XL would be a great idea... bigger cockpit

I’ve never sat in one before. Are they known to be cozy?

 

[BJC]

Ailerons will be the first update

Won’t that require a different structural analysis of the wing to account for the aileron forces?


BJC

 

[pwood66889]

"I’ve never sat in one before. Are they known to be cozy?"
I did once, Tim. It was tight - in length. Side-to-side it was "intimate," but not "squeezy." Getting in and our had challenges, though.
Percy at about 6 feet high and 150 pounds.

 

[TLAR]

Won’t that require a different structural analysis of the wing to account for the aileron forces?


BJC

For a 60mph wing, no

 

[BBerson]

The wing was specifically not designed for ailerons.

 

[cluttonfred]

This is another of those threads which remind me that major modification of an existing design is not that different than starting from scratch.

I suggest studying the Sky Pup if you like the construction method and configuration and designing your own plane in the same spirit from a clean sheet.

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.

 

[TFF]

It would be relatively easy to know red neck style. If you can walk up to it and twist the wing more than about a 1/2”, you will know an aileron will do that every time. Having the aileron actually change the angle of attack of the wing, not just relative AOA, would be entertaining to watch fly. Maybe some cool flutter and interesting control reversal.