Billy Miller’s eye-catching Thatcher CX4

There’s a sporty little gem tucked away in a hangar at Montgomery County Airport in North Carolina, when its builder and pilot, Billy Miller, isn’t flying it in those “Carolina blue” skies.

This plans-built Thatcher CX4 (S/N 426) is one of only 70 CX4s listed on the FAA Registry as of May 2020. N426F received its airworthiness certificate Dec. 28, 2017 — and Billy is one proud “papa” of Guardian.  

As a child, Billy used to ride bicycles with his brother to Moore County Airport to look at airplanes and play in a derelict AT-6 that sat on the ramp. He also built plastic models of airplanes, and finally, at age 48 in 1994, he decided to learn to fly. He took flying lessons in a Piper Tomahawk and earned his certificate in less than six months. 

“I flew for a while renting the plane, and then it got hard to get it when students were flying it — it just wasn’t available,” recalls Billy. “About 20 years later, I joined the EAA Chapter at Gilliam-McConnell Airfield and got to helping an A&P/IA work on airplanes. That’s what really got me back into flying. The mechanic ended up being airport manager at Montgomery County Airport (43A), and I helped him build engines and work on planes. During that time I saw the Thatcher aircraft in a magazine and I just got it in my head that I wanted to build that plane.” 

CX4 

David Thatcher of Pensacola, Florida, designed the CX4, introducing his prototype to the experimental world during EAA AirVenture Oshkosh 2004. The attractive, all metal airplane immediately garnered attention from admirers, and plans were soon being sold to prospective builders in numerous countries. 

The CX4 measures 18 feet 3 inches from nose to tail, has a wingspan of 24 feet, and a height of only 4 feet 8 inches. The wings can be removed in about 20 minutes, facilitating storage or transport. Weighing 560 pounds empty, its gross weight is 850 pounds.

The single-place cockpit is 23 inches wide, and a “wide and tall” version started with plans number 102.

The CX4 cannot be flown with its canopy open, but can be flown with its canopy removed. Powered by a VW engine, it has a starter and alternator. The airframe is built from aluminum, the cowling, wingtips, and wheel pants are fabricated from fiberglass. 

The CX4 has a 125 mph cruise at 75% power (with a 1700cc VW 55 hp engine), stalls at 40 mph, and has a 850 fpm climb rate. Fuel capacity is 10.5 gallons, and fuel burn is around 2.5 gph. With a 54/38 propeller, the CX4 needs about 700 feet to take off.

There is also a CX5 tandem version and a prototype CX7 side-by-side.

Building The Thatcher CX4

Soon after he decided he wanted to build one, Billy found a partially-built CX4 and bought it in April 2013. Fully retired at 67, he slowly started working on the CX4 when he wasn’t helping the A&P/IA. Then, after helping a friend build a Zenith 601, Billy focused solely on building his CX4, working on it one to four hours every day. 

After evaluating the components that were already built, Billy decided he’d rather build most everything directly from the plans himself.

Describing the overall process, Billy explains: “The plane is built around the center section. So you build the spars, then build the center section and lay it on a table so you can get the dihedral, and drill the holes for the main bolts. Then you build the framework from the firewall to the pilot’s seatback. That ‘cage’ had already been built, so I used that and then, starting from the number 6 bulkhead — which is the seatback — I built that whole plane except for the skin on the bottom of the fuselage, the seat bottom, and two wing root panels. I solid riveted my fuselage, except for just a few pulled stainless steel rivets.” 

When the fuselage was finished, Billy tackled the tail section…and soon discovered something amiss.

“I was going to use the spars that had been built for the horizontal stabilizers, but then I realized one inch had been cut off one side of the spars,” elaborates Billy, adding with a chuckle, “So I built new spars and what did I do? You know the old saying, ‘measure twice and cut once’? Well, I had built the stabilizers and skinned them and I was getting ready to do the rudder, and then I noticed the pieces didn’t fit! I got to measuring and said ‘oh, no!’ I had made the spars two inches short! So I built it all again.”

After completing the vertical stabilizer and elevators, Billy started building the wings.

“The wing spars are built with solid aircraft rivets, and I pulled stainless steel rivets on the other surfaces.,” says Billy. “There’s a very good Thatcher CX4 website that used to have a link to a group website where a lot of builders put photos of their entire build. I referred to those often as I read the plans and studied. I was already very familiar with reading blueprints, but going to that website and looking at pictures really helped!” 

Billy purchased a partially-built 1915cc VW 65 hp engine and after finishing the airframe, he tore the engine down and rebuilt it.

“I followed the Great Plains Aircraft Supply manual and watched the two CDs that show every step of building it,” he recalls. “The VW engine is very similar to a Continental or Lycoming in the way that it’s built as far as assembling the cylinders, the crank, and the cam.”

Paint Scheme 

With the engine installed on the completed airframe, it was time for paint. Billy hired a local painter to do the job, since, he says, “I thought a professional painter on his worst day would be better than my first day!”

“I love the P-51, so I wanted to paint it like a warbird with invasion stripes,” he continues. “I flew remote control model airplanes in the 1970s and 1980s, and I had a little model P-51 that was called Sweet Thing. I used that paint scheme for my airplane, but I wanted a different name for it. I was talking to my wife, Linda, about that one day and she said, ‘how about Guardian?’ I thought that was pretty good, because a guardian is a protector. She also suggested putting a griffin on it — a griffin is a protector also. So I found a griffin that was half eagle and half lion, and had that put on my airplane.” 

Billy was mighty proud — and rightfully so — of his accomplishment when N426F received its airworthiness certificate in December 2017. All told, he figures it took him about a year and a half’s time of solid work to complete it.

Go Fly!

Billy has logged about 60 hours in his CX4 since he’s had it flying, despite considerable time out to recover from double-knee replacement and to “shelter at home” during the COVID-19 pandemic.

He loves having the freedom to go out to the airport and have immediate access to flying his very own airplane that he knows from the inside out — as opposed to renting. So far, most of his flying has been to local airports, but he’s planning to do some cross countries this year.

“The plane is real slick,” he reports. “I can be running, say, 80 mph on final and if I drop the nose a little, it’s at 100 mph in a heartbeat! Its gross weight is 860 pounds, and you can really feel the thermals. I’ve only flown it three times when it was calm. It has full length ailerons and the controls are light, but not oversensitive. Mine flies a lot like an RV-4. To me, every flight is memorable. I just love to fly!

Take the Initiative!

As you might guess, Billy would be among the first to encourage others to build their own airplane.

“It’s challenging and it’s a real learning curve, but don’t let that stop you! It’s really rewarding, and I think anybody who has the initiative to get started can do it,” he says.

“Don’t look at the whole plane, just look at one individual part as you’re building it, and complete that. Then go on to the next part,” advises Billy. “If you look at the whole thing, it’s overwhelming. But if you just look at one aspect of it and work on it every day, no matter what little bit you do, you will complete it.”

“Anybody can build a plane if they take it one step at a time and keep working at it. It’s like building a big model — that’s the way I look at it — it’s the very same thing, just bigger!”