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Project Patrol

Quad City Aircraft Corporation Challenger II Special

By Chad Jensen, EAA Homebuilders Community Manager, EAA 755575


Don Weigt in front of his Challenger II

The freedom of this column called Project Patrol allows me to swing fairly wildly from one end of the experimental amateur-built spectrum to the other, yet still fall within our interest group. While last month I wrote about a seemingly rare plans-built airplane in the Christavia Mk I, my topic this time is one of the most popular kit airplanes available today, the Quad City Challenger.

With 4,000 Challengers flying since it was introduced in 1983, it certainly has earned the right to be called one of the most popular, and as their owners attest, it's one of the most fun flying machines available. There are several models existing in Quad City's lineup, and the Challenger II is by far the most popular, with 2,000 being reported as flown by the fall of 2011.

An offspring to the Challenger II is the Light Sport Special, which I'll just call the Special in this article. That model is quickly becoming a fan favorite, with 350 of them now flying. The difference is in the wingspan. The Special has a clipped span of just 26 feet versus the 31-1/2-foot wingspan of the standard Challenger II. Better roll rate was the goal with this model to create the "sportier" version of the original.

My trip to Madison, Wisconsin, a couple months ago became a multiple-story excursion for me after talking with Bill Rewey, who also directed me to the Christavia I wrote about in the December 2011 issue of Experimenter. The Challenger II Special that Bill directed me to for this report belongs to Don Weigt of Madison.

Don is a retired electrical engineer, and as you'll see from the pictures of his wiring runs, that part of his professional career is shining through on this project for him. His career actually began with the U.S. Air Force where he served as a bombardier/navigator system technician on B-52s, aka the BUFF (Big Ugly Fat Fellow).


The wiring runs and air lines are being laid out nicely along the side of the fuselage.

Don has been a private pilot since 2002, flying out of Middleton Municipal Airport – Morey Field (C29, Middleton, Wisconsin) in Cessna 172s after learning in the 152. He told me that he liked the 152 better, and he wanted something that was light and fun like it, but one that he could build at home and fly as a sport pilot. Don said, "I let my medical lapse after an angioplasty, so the time for flying under the LSA [light-sport aircraft] rules [as a sport pilot] has come for me."

"There was no medical reason I couldn't be reapproved to fly, but I balked at the cost. AOPA told me it is typical to spend about $6K to get the medical back, and then there are yearly follow-ups. Since I only flew day, VFR, it seemed the time was right for me to switch to LSA. After several years of very little flying, and that being with a flight instructor in a rented 172 [costing about $140/hour], I made the leap to buying a kit and building an experimental amateur-built that meets the qualification of LSA."

The kit as it arrives to your door from Quad City Aircraft Corporation is basically 49 percent complete, and you as the builder finish out the assembly, systems, engine installation, and covering—the remaining 51 percent. Don bought his kit on December 1, 2009. He really did figure he would have it completed by now with the estimated 300-hour build time, but as these things typically go, he's now in it at 675 hours of actual build time. He's nearing completion and hopes to have it flying in the spring of 2012.


Don's fuselage sitting in front of one of the wings and the tail surfaces, all of which are covered and ready to mount.

On the day of my visit, Don was working on closing the second wing, which was taking up his entire workbench in his single-car garage. We've all heard that airplanes can be built in single-car garages and even apartment living rooms, and I'm here to tell you, it's absolutely true!

The wing was resting on two EAA Chapter 1000 worktables that Don built prior to starting his project, and he has found their usefulness to be well served. The other wing was already covered and hanging on the wall behind the fuselage. The tail surfaces and side doors are already complete, and the HKS 700E engine is sitting quietly in the corner of his garage in a temperature-controlled foam-insulated box. As it sits, it's very nearly a complete airplane, just waiting for final assembly.

For the $17,000 purchase price of the kit, you get a pre-built fuselage, complete with factory-bent main fuselage tubes, wings with main spar, rear spar, and drag braces installed. (Ribs need to be drilled, fitted, and riveted. Root and tip sheet metal, as well as fiberglass tips, need to be installed.) The tail feathers are formed.

Nothing is covered with fabric (but fabric is included), and the only systems that are started are the push-pull tubes of the control system. Everything else is extra, including the engine, prop, and avionics. All up flying airplanes are routinely being completed for less than $35,000. Quite a bargain if you ask me! That bargain allows for some great fun, low and slow flying at its best, and you can take a passenger with you to enjoy the countryside or take that Sunday morning breakfast run.

Aluminum construction, whether tubing and fabric or monocoque sheet metal, is a nice, clean construction method. Don's work on the airplane thus far reflects cleanliness, and I would even go so far as to say he's methodical in his approach to keep things neat. The wiring runs are being nicely bundled and run through conduit supplied with Kuntzleman Electronics' Hot Box, and the remaining wiring will be contained or supported in a similar fashion when the bundles are complete.


The wide door modification can be seen easily here. The curved tubing gives much needed elbow room.

Don has made the "wide-cabin" modification, which was developed by Greg Klemp (a Quad City dealer). This isn't a factory mod, but Don worked off of pictures from Greg and made many phone calls to get it right. There's an extra tube installed on either side of the aft cabin that bows the doors outward to allow better elbow room and visibility all around. He has also faired certain portions of the fuselage with aluminum sheet to make smoother transitions in areas that he felt needed slightly better lines. "It's aesthetic only," he said, just because he wanted it that way.


To keep those small objects at bay while in flight, Don made a storage location under the seats using plastic trays.

For cabin comfort, he made his seats with the latest in "space-age" foam. The high-density (split density) foam forms to your body and makes for very comfortable flying on longer legs. Under those comfortable seats, he mounted plastic trays that can be found in any home store for keeping small items, such as fuel testers and tie-down ropes, out of the way and to keep cabin clutter to a minimum. As a tandem-seat airplane, cabin space is somewhat at a premium, so a little extra space to store small items will really come in handy.


The 60hp HKS 700E engine. Don has is stored in a temperature controlled insulated box while it awaits installation.

The previously mentioned Japanese-built HKS 700E engine, which he chose to use, develops 60 hp at 6200 rpm and is a horizontally opposed, four-stroke, two-cylinder, air/oil-cooled engine that is very commonly used in light aircraft around the world. The cylinders are air cooled, while the heads are oil cooled. The engine looks like an oversized radio-control airplane engine, but at 680 cubic centimeters, it's plenty big and powerful with its twin carburetors and reduction gearbox, and it will give ample performance for the Special. Click here for HKS 700E specifications.


The battery location in the Challenger II Special, as far forward as possible.

Don's other modifications are fairly simple ones, and in all reality, there isn't all that much one can do to change the Challenger II, other than a few cosmetic items and systems mods. The nose cone on most Challengers is permanently mounted, with just an access hatch cut to get to wiring and the battery in front of the instrument panel. Don decided to follow Greg's advice again and made his entire nose cone removable. He cut away a small aft section of the cowl and mounted that part to the fuselage permanently. This change allows for much easier access to things hidden underneath the nose cone.


This is the piece of the nose bowl that Don cut away and mounted permanently to the fuselage to make removing the bowl easier to allow access to the entire forward fuselage.


The Radio Shack project boxes used to house the perfboard and electronics that house the ignition modules for the HKS 700E.

The ignition control box is something that is definitely of Don's own design. He chose to build a circuit on perfboard stashed in a cut-down Radio Shack project box to connect a normal magneto-type "Cessna" (off—R-L; both—start; where "off" is a positive connection to ground) ignition switch to the HKS' electronic ignition modules (where "off" is an open connection).


Power distribution center for the airplane getting nicely wired and bundled.

The power transistors connect power when the magneto switch contacts open, and disconnect it when they close, reversing the normal function of the key switch. An electrical engineering background comes in real handy for this type of stuff. The electrical system will run off of standard automotive-style fuse buses. Many builders, myself included, find this type of bus wiring to be simpler than, and just as effective as, tried-and-true circuit breakers but at a much reduced cost.


The second wing being covered and readied for installation. Rivets and finishing tape are next!

For covering, Don used the SuperFlite 104 with PolyTak fabric that was supplied with the kit. But he needed to purchase some additional fabric since he elected to wrap it around the wingtips, and he double-covered the leading edges of the wings. Don said, "I learned how to cover the plane mostly from the Quad Cities instructions [that came with the kit] and a copy of the Stits manual loaned to me by Greg Sutter, from whom I had begged a flight in his clipped wing Challenger on the Labor Day before I ordered my kit. You might say my Challenger project is all Greg's fault!"

"I also got advice from my technical counselor, Bill Rewey, and my dealer, Greg Klemp. It was very helpful that I had covered model airplanes with silk and dope in the past. Covering the Challenger is similar, although on a much larger scale, and the heat shrinking of the fabric is a big advantage. Of course, the models didn't need rib-stitching or fabric rivets and tapes." For primer and paint, Don will be using Sherwin Williams SuperPaint exterior acrylic latex, but he must be keeping the color scheme a secret since that wasn't brought up — somewhat of a homebuilder's tradition, I think.

As I mentioned previously, when I arrived at Don's home, he was working on finishing up the covering on the wings. The root end of the wing he was working on is open (and stays open, but a tube between the bottom of the wings and the top of the doors closes the gap, and the top will be faired across the top between the wings to close that gap), and that allowed me to shoot some pictures of the inside of the wing to show how it's constructed.


A look inside the Challenger wing shows the no-web ribs. Structural drag and anti-drag braces give the wing its strength.

The all-aluminum ribs don't have any webbing structure, but they do have drag and antidrag braces built into the bottom of the wing structure. The main spar is a tube that doubles as the leading edge and also acts as a wiring conduit for wingtip lighting.

The next items on Don's checklist are to install reinforcing tapes over the ribs and then set the blind rivets that will mechanically attach the fabric to them. The fabric is glued down as well so there's chemical adhesion as well as rivet security. Once the rivets are in place, the finishing tape will be applied over the rivet heads to complete the wing covering process. Then painting will commence.

This is the first time I've seen a Challenger under construction, and I have to say that I'm impressed with the quality of the kit and ease of construction. Couple that with the low build time, inexpensive build cost, and pure fun flying when it's complete, I understand why these are such popular airplanes. Don already has the airplane registered; N4270W is the N-number. If you see this number on a grass strip or GA ramp someday, give him a pat on the back for a job well done!

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