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Flying Light Planes and Ultralights on Skis

Introduction by Dan Grunloh, Editor – Light Plane World, EAA 173888

Rob Steiger landing
Rob Steiger landing at Dan Grunloh’s farm.

In this article, several ultralight and light plane pilots share their experiences flying their planes on skis in winter. Read how they did it and learn how to build your own economical skis with included photos and drawings. Also included are sources for ready-to-fly skis and retractable skis. Don’t let the snow on your runway reduce your enjoyment of the clear smooth air of winter flying.

My first contact with skis came recently when my friend Rob arrived overhead at my farm unexpectedly with skis on his Eipper GT400. My hayfield was covered with soft powdery snow, so you couldn’t see the runway. But he knew just where to find it. After a landing and friendly visit, he was able to leave once he and I pulled the plane back on top of the snow where it had sunk in during his stay.

I asked Rob and two others to give us a rundown on how to get into ski flying. The examples shown here involve replacing the aircraft wheels with skis, but there’s another way to do it. Skis can be strapped onto the wheels without removing them by using shock cord and packing straps. Typically the tire drops into a box or frame attached to the ski. The disadvantages are the weight penalty and the problem of keeping the ski properly aligned on the wheels. With smaller-sized tires the skis may twist when taxiing or landing in crosswind. The conventional wisdom seems to be that it’s much better to remove the wheel and securely attach the ski to the airplane.

Flying an Eipper GT400 on Skis
By Rob Steiger, EAA 810073, for Light Plane World

Rob Steiger
Rob Steiger and his Eipper GT400 on skis.

Winter has set in, and the runway is clogged with snow. You’re not at an airport that plows the paved runway, and there’s no chance of running a plow over a sod runway. If the snow won’t set hard enough to roll over, the only way to fly is with skis. I’ve really had a blast flying my Eipper GT400 right after a heavy snow and looking at what is truly a winter wonderland. My skis were used and they came off a Challenger, but they slip right onto my axles. I’m not sure who made them, but it could have been Sheer Technologies Inc. It takes me approximately 15 minutes to switch between wheels and skis. Here are a few things I have come to know from flying with skis.

You have to get the ski size correct so they will plane quickly over the snow; just sliding isn’t enough. For some aircraft this could be a trial and error process. If they’re too wide with not enough length, they’ll plow; if too long, they’ll be hard to trim for flight. Do your early hangar preparation so you don’t have the “Dang, it won’t slide on the hangar floor, even with a herd of goat and three small boys pulling it” moment. Throwing a little snow on the hangar floor might help save your back, but having a set of dollies made up to maneuver the plane around really helps when there isn’t enough snow on the pavement outside the hangar. Taxiing over pavement, even a few bare spots on the runway, will eat the skis up pretty quickly.

Sheer Tech ski
Skis built by Sheer Technologies commonly used on Challengers.

Flying with skis isn’t really hard in and of itself, but there is a mindset that you have to put yourself in. You really need to be prepared for soft and short field characteristics of your plane. It would have been good to know that back in June or July when you could have been practicing for flying with skis.

Nice, dry, powdery, hard pack, or grainy ice bead snow isn’t too bad for takeoff, but landing is a bit different; always think the runway is short. You don’t have any brakes and you’re going to go farther than you might think on the “slideout.” This also applies to starting your plane. If you’re on hard pack, it will move with the slightest wind or thrust. It’s a good idea to be pointed to the direction you want to go before you start it up.

Wet snow or deep snow is really tough on takeoff. It’s like flat tires in tall grass in the summer. Remember, I said you could get practice for skis in June or July. I put in quite a bit of flaps for my ski takeoffs to get the nose ski light as soon as possible. That means less snow is getting kicked up onto the windscreen and into the prop. Running up and down the runway to pack the snow isn’t a bad idea, either.

As to landing at a field that hasn’t been desecrated yet, it may be easy from altitude to see where the runway is, but it’s a good idea to make note of some ground markers. When you get low the reflection may wash out your vision, so those markers may come in handy. I’ve been known to fly in and lightly touch the snow to make a mark and test the conditions. Just keep the airspeed up and the engine in the power curve to make it easy to pull out. Keep your wits about you.

There’s nothing like flying in a winter wonderland.

Kolb Firestar on Skis – 1,000 Hours Flown Over 25 Years
By Ralph Burlingame, EAA 285324, for Light Plane World

Ralph Burlingame's Kolb Firestar
Ralph Burlingame’s Kolb Firestar.

My skis are easy to make as they are composite water skis with no hardware on the bottoms. The builder would need to make a set of brackets for each ski with large drilled 3/4- or 5/8-inch holes to fit each wheel axle. I hadn’t built my skis on a pedestal, so the aircraft sits lower on skis than it does on wheels. I didn’t notice any difference in takeoff performance doing it this way because the dense air makes for a shorter takeoff than in the summer months even though the wing angle is lower relative to the surface. (The Firestar is a taildragger.)

Ski rigging
Kolb Firestar ski showing rigging details.

Overhead view of Ralph's Kolb
Overhead view of Ralph’s Kolb and the composite skis.

Using full-length water skis offers the advantage of using the surface area of the skis in heavy snow. There have been times when fellow pilots haven’t been able to take off in heavy wet snow because the skis sunk down. I've never had this problem with full-length skis. I spent an afternoon one winter day trying to help a friend take off on skis. His skis were short and weren’t able to get enough speed on takeoff to lift up. We even enlisted someone at the airport to run a snowmobile up and down the runway to pack the snow. It was getting dark, and my friend and I wanted to head for home. I spotted an aerosol can of lubricant spray in a hangar and asked if I could use a little. Then I sprayed my buddy’s skis on the bottom and watched as he was able to take off in very short order. I didn’t need to use the spray on mine, so I took off as usual (although I learned to keep a small can in my pouch just in case). Plans for my skis can be downloaded here.

Snow Hopping With a Weedhopper
By Mike Schweim, EAA 607384, for Light Plane World

 Snowhopper ski
Weedhopper on skis made from snowboards.

I’ve been flying my Weedhopper on skis since 2007. My plane is a 1982 Weedhopper C, powered by a Rotax 377 engine. I made my skis from kids’ snowboards (the pylons were made from scrap pine lumber, and 1/8-inch packing crate plywood). The snowboards are 8-inch wide x 28-inch long. They work well on packed, firm snow but sink in too much if the snow is soft or if you break through the crust of snow. I’m in the process of making a new set of skis, using larger snowboards, and purchased quality grade pine lumber and 1/4-inch Luan plywood. I got the idea for my skis from an article on building skis for ultralights published by Dave Loveman in Ultralight News. That article was inspired by a “Member Projects” story in the December 1997 Experimenter on skis built by Harry Winslow for his 3/4-scale Pietenpol Air Scout. 

Snowhopper ski
Close-up of Snowhopper ski.

I’ve found that winter provides some of the best flying conditions of the year, if you dress for it. In calm or light winds, the air is almost always smooth as glass. Also, almost all the fields around here in Southern Minnesota can become runways. The plane also performs much better in winter, as the cold, dry, winter air is denser than in the summertime. In winter, I can usually be airborne around 80 feet, compared with 100 to 150 feet in summer. Max rate of climb is around 1,200 fpm in winter, 800 fpm in summer.

I dress in jeans, sweatshirt, jacket, insulated coveralls, heavy socks, insulated boots, insulated ski gloves, homemade fleece neck gaiter, and helmet. I also have an 18-inch x 24-inch Lexan windshield installed on my plane to block the wind from my chest and face. I’ve had snowmobilers stop to watch and talk to me as I’m setting up or coming back from a flight. Several have mentioned that I must be crazy to fly in the cold. They don’t realize that 40 mph in the air isn’t any colder than 40 mph on their snowmobile. I can fly in comfortdown to about 28 degrees for about 40 minutes at a time.  In colder weather, I have a 12-volt car seat heating pad that I wrap around my chest inside my jacket. I power the heater with a 12-volt cigarette lighter socket on my plane, powered by the engine’s lighting coil.

I designed my ski rigging for fast and easy change between wheels and skis. I can switch either way in about half an hour. All rigging for each ski is attached to the airframe by a single bolt that holds a bracket made from 0.063-inch aluminum. I have a cable from the bracket to the rear of the ski that limits the upward travel of the ski. There’s another cable attached to the nose of the ski to limit the downward travel. There’s also a screen door spring attached to the nose of each ski to keep the tip raised in flight. I used springs instead of bungee cords because springs won’t get cut from ice and won’t be weakened by the cold. I had my skis adjusted so the skis tilt up and down approximately 10 degrees each way.

Snowhopper ski
Comparison of two different sizes of snowboards used to make skis.

When flying over snow, watch out for a reduced sense of depth perception. When everything is white, it can be difficult to judge your distance from the ground when landing or when flying low. The easiest way to land in those conditions is along the edge of a field, along a tree line, or where there are weeds, etc., visible along the edge to give you an idea where the ground is. Worst conditions are on overcast days, as the ground and sky tend to blend together along the horizon. I have several ski flying videos posted on my YouTube channel at www.YouTube.com/weedhopr.

For more information about flying Challengers on skis, read “An Ultralight for All Seasons” by Garth Wallace. Also read Dave Loveman’s article on aircraft ski installation. Don Zank of www.ZankLites.com builds custom skis similar to the Sheer Technology skis to fit any aircraft. For the ultimate in convenience when operating on snow and pavement, check out the Datum Air retractable wheel penetration skis.

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