Hi, folks.

My name is Mike Arnold. This is my little airplane. I was a filmmaker in San Francisco before I designed and built the AR-5, set a world speed record, and won the Louis Bleriot Medal. What a thrill! This is the story of the AR-5:

“NAA SELECTS 10 MOST MEMORABLE RECORD FLIGHTS OF 1992 (Jack Cox, Sport Aviation Magazine, April, 1993) From all the record flights made in 1992, ranging from modeling to spaceflight, the National Aeronautic Association (NAA) has selected the 10 most memorable, and one of them was Mike Arnold’s world speed record in the FAI’s Class C1.A/O for aircraft weighing less than 661 pounds at takeoff. Mike and his AR-5 were featured in our January ‘93 issue (page 34). The AR-5 has set the aeronautical engineering world on its ear because it is apparently the first airplane to break one of aircraft design's most durable barriers by having a flat plate drag area of less than one square foot. A number of noted aerodynamicists, including Bruce Carmichael and Alex Strojnik, have examined the airplane and determined that, indeed, its flatplate area is less than one square foot...about .88 square foot. Perhaps the most amazing to them is the fact that the aircraft was designed and built by a person with no engineering background, using only a few standard texts and EAA manuals for reference. The message once again is that if given sufficient freedom, which is what the FAA’s current homebuilt rules allow, individuals can do wondrous things. Congratulations again, Mike! J.C.”

Because I was a filmmaker, it was natural for me to keep a video record of the design and construction process. From those records, we put together four informative video tapes. We digitally remastered the tapes in 2008 and now offer them as DVDs.

"This four tape collection is a great study in highly efficient aerodynamic design and provides a great explanation and demonstration on how to construct with composite materials." Ben Owen, Sport Aviation Magazine, Mar '97

The AR-5 has been donated to the Hiller Aviation Institute through the generosity of the Lyn and David Berelsman Foundation, and is on permanent display at the Hiller Museum in San Carlos, CA. Please stop and visit if you're in the area. It's a very interesting collection.

Magazine Articles about the AR-5:

The AR-5, Getting The Most Out Of 65 HP, Mike Arnold, Sport Aviation Magazine, Jan. 1993

Getting the most out of 65 horsepower.

On August 30, 1992, at 8:15 a.m., on a warm Sunday morning, I flew the AR-5 through the three kilometer traps north of Davis, CA at 213.18 mph, setting a new world speed record in FAI Class C1aO (under 661 pounds gross). What a thrill!

It wasn't so much the actual flying...I was so worried that something might go wrong I didn't really get a chance to enjoy that part very much, but more the slow realization later that I had actually done it! After all these years I had finally learned enough to design and build an airplane from scratch...and it was good enough to set a world record. Very heady stuff, indeed! I recommend it to all you folks who've ever thought about doing something similar.

I've dreamed of doing this since I was a little kid. I built countless models and imagined myself sitting in those tiny cockpits pulling high G turns and doing victory rolls. It was always a little fighter, never a bomber, and I wanted to design it.

Over the years I've pondered and meditated for hundreds of hours over photos of Me. 109s and Spitfires, Bearcats and KI-84s, P-51s and C-205s...all of those beautiful, expensive, hot rod airplanes that I loved as a boy. Their lines have been burned into my subconscious for nearly half a century.

I also collected all the technical information I could find (and understand) that was related in any way to the design and construction of an efficient low wing, single engined airplane, and then cogitated on all that stuff for years. It's a wonder I can still talk.

By the late '70s, I couldn't stand it any longer. I'd been in the Army, graduated from college, and was gainfully employed in my chosen profession, but I was doodling airplanes all the time. In 1978 I left a perfectly good job as a filmmaker and drove to the Mojave Desert to learn about composites from Fred Jiran at his glider repair station. Fred has been credited for having introduced Burt Rutan to the foam and fiberglass techniques developed by German sailplane designers for building prototypes without molds. Fred was then building all the prefabricated parts for the new VariEze. I brought a wing test section I had built and was having problems with and Fred, too busy to answer my many questions, hired me to build a VariEze fuselage and some molded, prefab wings.

I learned a lot, and got to poke around in all the latest gliders, but it only lasted six months or so...too much hot sand and wind, and too many stickery things out there for me. But I've been designing and building airplane parts ever since. Thanks, Fred. And thanks, Burt, for showing us all those simple ways to build composite airplanes. Most of my work has been on other people's development prototypes, and most of them have not been very successful to date. Ah, well, it's been fun.

In late 1981 I started drawing the AR-5 with the idea that if it were successful I'd sell plans like Burt Rutan was doing and, although I didn't see a great market for a light weight single seater, it might help pay for the prototype. Back then, product liability looked like it was becoming a problem, but I was sure reason would prevail and the courts would soon straighten themselves out. I built the fuselage and tail group in 1982 and put them aside for a while to wait on engine developments. When I started the design, rumors were floating around about turbocharged Onans putting out 35 horsepower, and I drew the forward fuselage for something that size, hoping that a better engine would come along later. Years passed, and many promising engines came and went. I drew cowls for Aero Motion Twins, Pong Dragons, sawed-in-half Volkswagens, and finally, TWO STROKES. It took a long time for me to come around to the two strokes. I'm a dyed-in-the-wool, four stroke kind of guy, and I'd watched the ultralights struggle with the early engines. They didn't look too good. Someone was falling out of the sky at least once in a while. But after a bit, they seemed to get better, and when the Rotax emerged as the most reliable of the bunch, I drew a cowl for it. Didn't look half bad. The more I looked at the engine, the more interested I got. It appeared that, with some work, I could squeeze the exhaust system under the cowl, the rest of the package seemed about the right size, and the weight was just perfect. And the water cooled engine was pumping out 65 hp! I was giddy. I realized that I would have to beef up the airframe to handle the extra speed, and that would add weight, so I'd have to beef it up to carry that extra weight, and so on, but the performance numbers I was coming up with were too attractive to ignore. It was going to be a real fighter!

About the time the airplane was on the gear, Mark Brown introduced his lovely Star-Lite with a Rotax 503 in it. Now we're getting somewhere. Here was something that looked like a real airplane, and Mark was saying that the engine was staying together, and maybe I'm not so crazy after all. And the Avid Flyers and Kitfoxes seemed to be having good success with the water cooled 532. I bought my 532 in late '87. The AR-5 first flew in early '92. Flight testing and development went fairly smoothly. No problems with the airframe. Cooling and propellers took most of the time. It's now a reliable weekend friend, and it does great victory rolls. I've finally got my fighter!

Turns out, though, I was a bit too optimistic about the courts being able to straighten themselves out. Liability is more a problem now than ever. I've been listening to the horror stories for ten years, and I'm scared to sell plans. Maybe someday things will change and I'll get my nerve up to take the plunge, but until then I'm limited to selling some video tapes about the unique design and construction process. Four videos are available now. We plan to continue to make them as long as people continue to be interested.

About the AR-5

The AR-5 is a sport plane (not a racer) roughly the size of a Midget Mustang...a little bit shorter fuselage and a foot and a half more span on the end of each wing. It looks bigger, sitting next to Kit Sodergren's on the flight line. It stands taller.

With starter, alternator, battery, coolant, and radio gear, but without pilot or fuel it weighed 488 pounds on the certified scales we used for the NAA officials. With Craig Cato's excellent 50x70 record setting prop, in normal, everyday flying conditions, it will cruise between 165 mph TAS (3 gph) and 175 mph (4 gph - two strokes are thirsty).

It feels quite solid and stable in the air. Control forces are light to moderate and well harmonized, and the roll rate is high. The stall comes at around 56 mph clean, and 53 mph with full flaps. Descent on final is fairly steep, and landings have all been uneventful. It's a pussycat on the ground. The wide, telescoping spring main gear and large rudder work well. I fly in all kinds of wind and have rarely had to use brakes to stay out of trouble. It feels like my old Aeronca 7AC on take off and landing. Flaps come down at 100 mph and I fly final at around 80. Visibility in the air is excellent, but, as in any fighter, the pilot can't see directly over the nose when the tail is on down, so I do wheel landings and try to get the tail up quickly on the takeoff roll. Because the cowl is so narrow (no cylinders sticking out the sides), I don't have to do much S turning on the taxiway to see where I'm going. Fuel capacity is 12 gallons which gives me a range of 500 miles with 45 minutes reserve. Better than an Me. 109!

The airplane climbs 1000 to 1200 fpm at 115 mph with Craig's speed prop, but at less than that speed the rpm falls below the Rotax's power band and the rate of climb diminishes. The takeoff roll is not very exciting...especially on these 90 degree days we get around here. Static rpm with the race prop is only 4400 which, according to the manual, is down around 40 hp, at best. I can still get in and out of 2000' strips, but I miss the 1500 fpm climb I got with the first prop I tried. It would only do 175 flat out but I sure did like the acceleration. The sound and feeling reminded me of the outboard boats I drove as a kid. Nothing violent about it...just a surprisingly strong, smooth push. I want that back again. It needs a constant speed prop.

The airplane is exceedingly quiet as it takes off or passes overhead. The stock Rotax muffler works very well, and wrapping it with insulation eliminates all that tinny dinging I've always associated with two strokes.

Inside, it's a different story, however. Below about 5800 it only buzzes, but above 5800 it gets downright noisy in there. Because 5800 rpm equals 175 mph or better and marks the top of the recommended cruise range, I spend most of my time at lower settings. The cockpit is very comfortable. I'm almost six feet tall and rarely bump my head in turbulence and have never felt cramped or confined. Inside dimensions are similar to a VariEze's.

The engine is a box stock 582 Rotax. I burn Chevron Super Unleaded and Red Line Kart Oil (synthetic). I've never had the head off, but we did have to modify the exhaust system to get it inside the cowl and, although we tried to use as many of the stock system's components and dimensions as possible, we found it necessary to make part of the system oval-section instead of round and I suspect that we're not developing the full 65 hp. The engine seems to run well enough, though. I've been flying for a year and a half now, first with the 532 while we worked out the installation and cooling problems, and now with the 582 for the last 40 hours or so. I had about l75 hours on the airframe as of October (1992).

So why does this almost-full-sized, blunt nosed, fixed gear airplane perform so well on such low horsepower? Low drag, of course. It has a coefficient of drag of around .016. Very low. It has an equivalent flat plate drag area of .88 square feet. Very small. But how come?

Here's what I think:

First, it's smooth. I've used the same finishing techniques Burt used on his VariEze/Long--EZ designs and, like him, I've used laminar flow airfoils and paid attention to contours and gaps.

But the AR-5 is almost as big as a VariEze, and it goes as fast as the fastest O-235 powered one I know of, and it does it on half the horsepower. "Smooth" is good, but it doesn't fully explain it.

Second, it's light. That's mainly due to the light engine. Regardless of what you've heard, foam and fiberglass airframes are heavier than wood or metal ones, especially if you put a pretty finish on them. The AR-5 has probably got 30 pounds of paint and filler on it. It's, maybe, 150 pounds lighter than a VariEze. Significant, for sure, but still not a complete answer. If you could take 150 pounds off a VariEze, could you get it through the traps at 213 mph on 65 hp? Maybe, but I think there's something else at work here. I took the record away from a gentleman in Austria who flew a clipped winged BD-5 with a 582 Rotax in it. He was supported by the Rotax factory, so I'm sure his engine was putting out at least full rated power, and the BD-5 is a very small, retractable geared, streamlined little bullet that is probably as light as the AR-5. I beat him by 13 mph without resorting to any speed tricks beyond washing the bugs off. "Light" helps, but it isn't everything. So what gives?

I think low interference drag "gives".

Interference drag reduction, as I've applied it, is more than just reducing the interference between boundary layers in the corners. What I've tried to do is arrange the wing and fuselage and canopy so the combination produces a sort of "Poor Man's Area Rule", as the late John Thorp is said to have called it. I spent a lot of time shoving things around on the general layout drawings, paying attention to the wing root fairings, and carefully positioning those things that have to be there anyway, like the canopy (and even the wheelpants), and reshaping the fuselage itself. If you get it right, you can reduce the drag of the wing/body combination, and that's what I think happened on the AR-5. I think I got it approximately right. The exhaust streak that forms on the fuselage side above the wing root is remarkably straight. I love that exhaust streak.

I noticed, after all this manipulation at the drawing board, that the shape that resulted happened to lend itself to a unique kind of construction that allowed me to build the fuselage by hot wiring it the same way Burt hot wired the wings on the VariEze. No fancy compound curves to carve. In fact, very little foam carving at all. The shape of the fuselage comes out almost automatically. The .4" thick sandwiches that form the majority of the primary structure are all cut to shape and thickness with the good old hot wire. Pretty darned neat!

It is this aerodynamic and structural concept that I intend to address in the videos. This principal of interference drag reduction (and the simple method of fuselage construction that goes with it) can be applied to any design.

Like many of you, I've been frustrated by the difficulty of finding accurate performance data on homebuilt designs. We homebuilders are sort of like fishermen. We tend to exaggerate a bit. None of us likes to admit we've built our airplane too heavy, or that it doesn't go as fast we think it should, so we fudge a little when we talk about it. I've tried to resist those "fish story" impulses in myself while compiling the data in this article, and I believe my numbers are accurate, but I invite challenges. Help keep me honest. Ask the guys who fly with me. Check the weight and speed with the National Aeronautic Association (NAA). Or come out and fly alongside. And speaking of challenges...the AR-5 turned out to be a fine little dog fighter, just as I'd hoped as a kid. I've already got a couple of Midget Mustang credits. Like to try turning with me?


I took this information from the VariEze Owner's Manual. I assumed 105 hp from the O-200 Continental because everyone overwinds them. Most VariEzes weigh 630 to 660 pounds. The fast ones will do 200 mph. The VariEze has slightly more frontal area due to the thick strake tanks. Both airplanes have fixed main landing gear. The VariEze has a retractable nose wheel, while the AR-5 has a small, fixed tailwheel.



Fuselage length
















13 sq. ft.

13 sq.ft.


8.6 sq. ft.

7.2 sq. ft.

The drag of the VariEze is approximately 158 lbs. The drag of the AR-5 is 97 lbs. It's hard to attribute all that difference to cooling drag, although I'm sure the AR-5 has somewhat less. I think part of the difference is interference drag. It's a major player on an already clean airplane. My ballpark guess is that reducing it, alone, might have added 10 mph to my top speed.

Mike Arnold, Nov, 1992 (reprinted from Sport Aviation Magazine, Jan 1993)

Getting to know the AR-5, Bruce Carmichael, Kitplanes Magazine, Oct. 1993

Mike Arnold's record-breaking single-seater resulted from a lot of study, followed by moldless-composite building.

By Bruce H. Carmichael, Kitplanes Magazine, Oct., 1993

In August, 1992, Mike Arnold set a new 3 km FAI world speed record of 213.18 mph in Class C1aO for airplanes weighing less than 661 pounds at takeoff. He set the record in his brand new design, the AR-5, an all composite homebuilt sport plane powered with a 65 hp Rotax. Seeing the photo and caption in the October issue of the EAA's Sport Aviation magazine certainly aroused my curiosity.

While I was trying to figure out how to get in touch, the phone rang, and it was Arnold, who was directed to me by our mutual friend, Stan Hall, the sailplane designer, builder and pilot. Arnold offered to let me study the AR-5 and asked if I could do a representative waviness survey on his wing. I jumped at the chance. The day after Thanksgiving found me in his compact shop in Crockett, CA, where he had the AR-5 assembled.


The gleaming white plane immediately said "smooth, light and tight" with a near absence of protrusions. It was up on saw horses, allowing me to crawl under.

The bottom of the airplane is every bit as smooth and protruburance-free as the upper part. Arnold will jolly well get drummed out of the airplane manufacturers's club for that as they have traditionally mounted all the drag-producing garbage underneath where they think no one will see it.

I saw no ripples in reflected light, indicating a very low degree of surface waviness. There are no unnecessary paint stripes to trip the laminar boundary layer. All intersections are beautifully filleted, and joint lines are flush and barely discernible. It looks like it was carved from a solid block of ivory. This is the work of a master craftsman and on a par with the finest high-performance sailplane technology.


As my friends in a group named TWITT (The Wing Is The Thing) say, the wing is the thing. Arnold's 21 foot span, aspect ratio 8:1 wing employs an NACA 65-418 section at the root and an NACA 65-215 at the tip. The plain flap of 25% chord covers 50% of the wing span, and where the wing fuselage fillet would have cut it off short at the root, Arnold cleverly extends it with a lower-surface, split-flap addition.

The 22% chord, top-surface hinged ailerons cover 40% of the span. No curtain or foam rub seals are employed, but the hinge line gap is very small. The leading edge of the ailerons, elevator and rudder are slightly extended outside the contour line as recommended by Hoerner to reduce drag. Elevator and rudder are mass-balanced at the tip by a narrow horn balance extending to the leading edge. They are all external balances and, of course, protrude when controls are deflected

The streamwise running gaps are not rub-sealed. The control surfaces are fastened on with raised head machine screws for easy removal. The cusps have been left in the ailerons, but Arnold reports excellent lateral control forces. The controls are well harmonized on all three axes.

The horizontal tail uses a low-drag, 12% thick section at the root and 10% at the tip. The vertical fin uses a 10% low-drag section. The tail surfaces are very generous in area as Arnold designed this as a personal light airplane, not a racer.


The 14.5 foot long, 23 inch wide, 36 inch deep fuselage has very pleasing lines. The slightly less than 1 foot diameter flat open cowl face is faired elliptically back to the point of maximum fuselage width. It is interesting to note that flat faced Navy torpedoes, faired in this manner, show no increase in drag over a streamlined nose of equal wetted area. This fuselage with the internal flow system sealed off should show no increase in external drag due to nose form.

The forebody is smoothly faired into the conical afterbody. A beautiful free blown canopy is generously faired at its leading edge into the basic fuselage, thus softening the adverse pressure gradient approaching the canopy and preventing excessive thickening of the boundary layer. This type of leading-edge filleting is also found on wing and tail surface intersections.

The full-width canopy hatch is foam-sealed along the transverse but not along the longitudinal seams. The canopy seams were not internally tape-sealed during the record attempt. The hatch is secured by two piano hinges on the right, and a single latch on the left. The pilot can release the latch in flight, and the canopy then raises only half an inch off the left rail.


To give away as few drag points as possible on this important juncture, Arnold did not allow the fuselage to contract until very near the wing trailing-edge. He had read an article by an old research pilot, flight instructor and friend, Ray Parker, on the importance of this. There is a stagnation-relieving fillet at the leading-edge, a corner radius fillet to prevent the large boundary layer-thickening found in a square corner and an expanding fillet on the aft portion to soften the adverse pressure gradient. The forward fillet is kept small to prevent excessive supervelocity near maximum wing thickness, with its attendant flow deceleration problem aft of maximum thickness. The bottom of the wing is flush with the bottom of the fuselage, thus virtually eliminating two intersections. This juncture should help reduce the interference problem common to low-wing aircraft, particularly at the higher lift coefficients, and, no doubt, it helps also at high speed and low lift coefficients.


This is the cleanest fixed landing gear that I have seen. It was placed outside the propeller slipstream so that it does not see the higher dynamic pressure of the prop blast, nor is it subjected to the non-zero angle of attack from the propeller blast or swirl. The low-fineness-ratio fairings of the gear legs meet the wheelpants flush with the outer side, thus eliminating two more intersections. An expanding fillet is employed at the rear of the leg/wing intersection.

The wheels protrude from the pants a mere 2 inches; the steerable tailwheel is tiny and unfaired. It is located at the end of a circular-cross-section rod. The airstream sees an elliptical cross section of this round rod due to its angle with the flow.


The protuberance under the fuselage admits cabin air and looks like a miniature P-51 cooling duct. The intake is spaced out from the fuselage skin so that, should carbon monoxide become entrained in the fuselage boundary layer, it will not be drawn into the cabin. The only protuberance under the wing is a single dogleg pitot tube made of ¼ inch round aluminum tube, unfaired.


The liquid cooled Rotax 582, according to the manufacturer's specs, delivers 66 hp at 6600 rpm. It has a very large exhaust system that Arnold has managed to house within his fuselage to the right of the engine . A portion of the open cowl face feeds air to cool it, exhausting through a 6-square inch exit duct raised about ¼ inch out of contour. Cooling air flows over the rounded intake lip and dumps into the internal cowl plenum. The engine exhaust exits through an unfaired, circular-cross-section steel tube that protrudes through the fuselage wall and turns downstream.

The expansion chamber had to be made elliptical to fit, and Arnold thinks it may have detuned the system and cost him a bit of power. Arnold tried a large-diameter spinner with the inlet air entering through the circumferential entry, but he found no change in top speed.


Having failed to see any large surface waves in the wing with reflected light, I next rocked a machinist's 6-inch scale on edge over the contour in the chordwise direction. I could not feel any jarring due to flat spots or large waves.

Next, we put a piece of masking tape marked off in quarter-inch intervals on the surface in a chordwise direction located 5 feet out from the fuselage wall. We read the dial indicator operating between fixed legs spaced 2 inches apart. A plot of the readings on the vertical scale, amplified 500 times compared to the chordwise location horizontal scale, revealed the following:

We could now find the spar where the largest peak-to-peak reading of 0.0036 inch over a length of 3.6 inches gave a ratio of one part in a thousand. A second wave nearby had a peak-to-peak reading of 0.002 inch over a 1.5 inch wavelength, or 1.33 parts in a thousand. Farther forward on the chord, a wave of 0.001 inch, peak-to-peak reading over a 4 inch wavelength, yielded a ratio of one quarter part in a thousand.

What do these numbers mean? It means that Mike Arnold has smoothed his low-drag wing to a greater degree than any production composite sailplane and equal to or better than the best achieved by dedicated sailplane pilots after a winter's work filling and resanding their wings.


How do we explain a man-carrying, low wing, tractor-propeller-driven airplane with a fixed landing gear and generous tail surfaces achieving this record-breaking performance on such low horsepower?

The FAI rules permit losing some altitude on the way into the course and over the measured run. Arnold had to hold his entry speed to 220 mph to stay within his flutter clearance. Although he could have entered at 492 feet, he chose to enter at 300 feet to be safely within the requirement. By letting down to 30 feet at the end of 4 km, he would have a descent angle of 1-degree, 18 seconds. His weight component along the flight path would give him an extra13.6 pounds of thrust to help stave off the decay of entry speed toward normal maximum level flight speed. By observing his readings during the runs and comparing with the ground data, Arnold was able to get a first-order correction for his airspeed system. He feels his maximum level flight speed was 207 mph.

Using this speed, 65 hp and 82% propeller efficiency, the AR-5 drag area comes out to 0.88 square feet. People have been trying for a long time to get a man-carrying airplane under 1 square foot of drag area from such calculations. The latest Formula 1 racers also appear to be in the vicinity of 1 square foot.

Dividing the drag area by the wing area of 55.125 square feet yields a traditional drag coefficient of 0.16. Drag area numbers have the disadvantage of combining size and speed, while the drag coefficient based on wing area moves around as the ratio of wing area to total area changes from design to design, but if we divide the drag area by the total wetted area of 236.4 square feet, we arrive at a wetted-area drag coefficient of 0.0037!

What does that mean? The lowest figure I had seen previously for a propeller-driven airplane was 0.0040 for the P-51 fighter, which had a larger Reynolds number, which means lower skin friction drag. In addition, the P-51 has a flush retractable landing gear and zero cooling drag. Mike Arnold's AR-5 is the most efficient man-carrying, propeller-driven airplane I know about.


The above comparison may puzzle traditional aero engineers. But the conclusion is that composite construction executed by a person of Mike Arnold's training and skill not only eliminates roughness drag, but the reduction of surface waviness permits achievement of the design extent of laminar flow. By using the 65-series airfoils, Arnold has almost 50% of the wing wetted area operating laminar with its greatly reduced friction drag. His very clean fixed landing gear located outside the propeller wake, his very low wing/fuselage intersection drag, and the absence of protuberances and associated form-drag all help. His efficient Cato propeller with twist distribution adjusted for fuselage interference as suggested by propeller guru Eugene Larrabee also helps. It appears that his cooling drag is also very low. The low total wetted area of this plane completes the picture. I couldn't resist doing a component by component drag buildup calculation. The sum of the external drag areas was 0.806 square feet, leaving 0.074 square feet or 8% of the total for cooling drag. With a less conservative fuselage drag estimation, the margin for cooling drag became 12%.


It is now obvious that as interesting as the advanced craft are, the people behind them and their stories are even more interesting. Arnold has been fascinated by high-performance aircraft all of his life. He carefully memorized the best features of the best racing planes and fighters and spent countless hours drawing his dream midget fighter-personal aircraft that would be fast, maneuverable and safe.

Arnold's degree is in movie making rather than engineering, but he has found and read the great books that present the real physical picture in understandable form. In particular, he studied "Fluid Dynamic Drag", by Hoerner to the extent that he took it on vacations with him. He then apprenticed himself to Fred Jiran of Mojave, California, to learn to work with composites. Jiran repairs and fine-tunes racing sailplanes, so Arnold got to see the finest drag-reducing tricks of the high-performance sailplane manufacturers.

He learned clever ways to build one-off prototype planes using the Burt Rutan method. Arnold's goal is to keep things as simple as possible while giving great attention to drag reduction. Engineering judgment and superb detail design are found in the AR-5. Arnold is a prime example of a man with a dream and goal who has made all the long, hard acquisitions of knowledge and hands-on experience necessary to reach that goal. There are many lessons to learn from his history as well as from the AR-5.

{Author Bruce Carmichael is an aerodynamicist who is well known for his work in the area of drag reduction and high-performance sailplanes. His comments are recorded in Mike Arnold's,"Why it goes so fast" and "Moldless, low drag wheelpants" videotapes, but he is not commercially involved with the AR-5. --DM, Ed.}

(Kitplanes Magazine, October, 1993)

The hottest airplane money can't buy, Robert Goyer, Sport Pilot Magazine,May 1994

No, you can't buy a kit or plans for Mike Arnold's 213 mph rocket, but the videos will definitely make you drool, and teach you a thing or two in the process.

By Robert Goyer, Sport Pilot Magazine, May 1994

For years aircraft designers have been trying to get the most performance out of the least engine, and there have been some pretty amazing success stories. Back in the 1960s, composite innovator Ken Rand came out with a pair of lightning quick fiberglass wonders he called the KR1 and KR2. With 80 hp VW engines, these little speedsters flirted with the 200 mph level on a regular basis. Formula One racers have pushed the envelope even harder. With stock 100 hp Continental engines, these aerial hot rods have done major damage to the 250 mph mark. As regular readers of "Sport Pilot" know, the Formula One racer "Nemesis", piloted by John Sharp, set a new world's speed record at Oshkosh last summer when it clocked a run of better than 277 mph.

But of all the speed records I've run across, few have inspired in me the kind of awe I felt when I first heard about Mike Arnold's mark in a Rotax 582-powered aircraft. 213 mph. Read on!

The AR-5 is not a revolutionary aircraft in any one way. It's made of standard wet-layup fiberglass/foam construction. It makes use of a conventional low-wing taildragger configuration. And its powerplant is an off-the-shelf Rotax 582, producing about 65 hp. What makes Mike Arnold's incredible little aircraft so amazing is its ingenious combination of design, materials, and approach. In a phrase, the AR-5 is an airplane which gets maximum results out of minimal weight without, and this is the key, being a minimal aircraft.

Mike has been building aircraft out of fiberglass since the late 1970s when he moved to the town of Mojave in the High Desert of Southern California, then the Mecca of composite aircraft construction and started working on fiberglass planes.

In 1981 Mike started drawings for the AR-5 with the thought of possibly selling plans or kits of it when the product liability mess finally got straightened out. Well, you know that story, but Mike went ahead and built the airplane anyway. At the time when he began work on the structure, 1982, there weren't really any engines available which were light enough and could produce the kind of power Mike figured he'd need for the plane. Mike admits that it took him a while to warm up to two-stoke engines, but as their design and reliability improved, they started looking better and better to him. Not only were they powerful enough for their light weight, but by 1987 Rotax's new water-cooled 532 was putting out a lot more power (65 hp) than he had even dreamed of. He actually had to beef up the engine mount to carry the extra weight. It was a problem Mike was more than happy to have.

Mike first flew his AR=5 in 1991 with the 532 and was getting about 175 mph top speed with a prop which gave him a 1500 fpm rate of climb. After a few experiments, Mike switched to a Craig Catto race prop and things really started happening. After bolting on the Rotax 582 and straightening out the installation and cooling problems, Mike realized he was really on to something. Especially when he clocked a run at 207 mph. Though he admits he didn't know much about records, a friend told him that 207 was probably a record for an aircraft in its category. So Mike called the FAI (the international organization which officiates on record attempts) and went through the involved process of going for the mark.

As they say, the rest is history. On August 30, 1993, Mike in his AR-5, made four runs over a closed course, all which would have broken the old record of 201 mph. For his efforts, the FAI awarded Mike the coveted Louie Bleriot medal. Each year the organization bestows only three (or fewer) of these awards, so the honor is a very real one. It's just another of the ironies behind the saga of the AR-5. Mike never intended to use the plane to set records; that just sort of happened. Quality, as they say is its own reward.

The record took the world of flying by surprise. Like many others, when I first heard news of the new mark, I suspected it might be a joke. After I realized the record was for real, I just had to know how the feat was accomplished.

According to Arnold, there's no one secret behind the success of the design. Instead it's a combination of factors which allows the AR-5 to achieve the remarkable figure 3.28 mph per horsepower.

Mike believes that one of the major factors contributing to the efficiency of the design is the remarkably low interference drag of the airframe. Interference drag is that which is produced when the clean airflow from two structures meet and violently disturb each other. On light aircraft this is most pronounced at the junction of the wing and the fuselage. After extensively researching the subject, Mike went to work modifying his basic design to minimize this interference drag. His work in this area has evidently paid off handsomely.

Another major factor is the plane's remarkably small drag area, a flat plate area of less than one square foot (.88, to be exact). Interestingly, it wasn't until after Mike set the record that he set out to calculate the plan's aerodynamic profile. When he came up with this figure, aerodynamicists were stunned. Some refused to believe it. It turns out the AR-5 was the first man-carrying airplane in history to break the one-square foot flat plate area limit. If it sounds esoteric to you, believe me, in the world of aerodynamics, it's a big deal.

Despite the fact that the AR-5 is the fasted thing in the sky in its category, Mike says he never intended it as a racer. Instead, he sees it as a sport plane, one which will provide plenty of performance while still exhibiting excellent slow speed manners and outstanding stability. When you look at the long wing and large tail surfaces, it becomes clear that Arnold could have made the plane faster by going with a shorter, thinner wing and smaller tail section. But it would have been at the expense of low speed stability and structural integrity, areas in which Mike was not willing to compromise.

Due to a freak accident, Mike got an unwished-for chance to find out first-hand just how strong the structure really was. Last summer on a return trip from a friend's airport, the AR-5's engine quit (the result of a throttle cable ferule coming off and getting into the works). After a hard off-airport landing, Mike walked away unhurt. Though the engine and prop were destroyed and the plane's landing gear, cowl, and a couple of fairings were damaged, the major structure came through the incident without any real damage. Ironically, this incident has given Mike the chance to make a few changes to the plane. As of this writing he's already completed a new landing gear and set of wheelpants, and he's installed an in-flight mixture control to help keep the 582 cooler during descents. The mixture control should also help the 582 reduce more power at altitude.

Mike hopes to have the AR-5 up and flying again by this summer {it flew again in April, 1994, it's better than ever!...M.A.}, at which time he hopes to get back into the air and get flying again. He really misses his little rocketship.

Those of you who want to learn more about the project are in luck. Mike's firm, The Arnold Company, offers two excellent video tapes which tell you all you could every hope to find out about the AR-5 (except, perhaps, where to send for plans!).

The first tape, entitled "Why It Goes So Fast", is an in-depth look at the record setting performance. But more interestingly, it also goes into great detail on how Mike came up with such an incredibly clean structure. There's commentary from aerodynamicist Bruce Carmichael, who, like the rest of us, seems positively in awe of Mike's achievement. For those of you who like practical aerodynamics, this is a fascinating tape. Especially interesting to me were the discussions involving the interference drag phenomenon.

The second tape, "How It's Made", is a two-hour discussion of how the AR-5 came together. Mike and his colleagues take us through the process of creating fiberglass and foam structures, actually making a few of them as we watch and listen to Mike's commentary on the ins and outs of the construction techniques. If you've ever wanted to build your own fiberglass aircraft, this tape is an absolute must, as it takes dry theory and puts it into the goopy, real world of wet lay-up construction. Fascinating!

If you love this kind of stuff as much as I do, you should get these tapes. "Why it goes So Fast" retails for $29.95; "How It's Made", for $39.95, or you can get both of them for $59.95. That's $20.00 off the original price. To order either or both of these fascinating tapes, send a check or money order to The Arnold Company, 5960 S. Land Park Dr. , Sacramento, CA 95822. If you want to get plans for the AR-5, you'd better write to Washington and get them going on liability reform. If that works out, who knows, maybe you'll get your chance.

Robert Goyer, Sport Pilot Magazine, May 1994

{Note: We now sell four tapes and our address has changed. Please see below. M.A.}

Drag Analysis of the Arnold AR-5 Airplane, Bruce Carmichael, CONTACT Magazine, Jan. 1994

By Bruce Carmichael, 34795 Camino Capistrano, Capistrano Beach, CA 92624; CONTACT Magazine, Vol 5, Number 1, Jan - Feb 1994, Issue 24

The AR-5 is a composite construction, low wing, fixed gear, tractor monoplane powered by a liquid cooled 65 horsepower Rotax 582 engine. The fact that this configuration, which had not been designed as an all-out racer, had captured the world speed record for take-off weight of 661 pounds or under, makes it highly interesting for drag estimation study.


At Mike's invitation, I first visited his shop for a detailed inspection of the AR-5, including checking the wing for surface waviness with a wave gauge. The workmanship is superb and a look at it in glancing light makes a wave gauge reading almost superfluous. It was no surprise when the largest wave I could find over the spar area was 1/1000 ratio of wave height to wave length. The external aerodynamic drag estimates need no corrections for surface roughness. The surfaces are remarkably free of protuberances and all joints and control surface hinge lines are beautifully executed. The internal aerodynamics of the cooling system leave room perhaps for some additional refinement. Since I did not have enough detailed internal geometry, this report calculates only the external drag and then inquires as to the margin from the total drag (calculated from speed, power, and assumed propeller efficiency) left over for cooling drag. I did not use the record speed of 213 mph for the analysis but rather Mike's best estimate of his maximum level flight speed of 207 mph. The record setting rules permit an assist from gravity to enter the course a bit above maximum level flight speed.


The aspect ratio eight, 55.125 square foot, low drag wing has a taper ratio of 0.78, a NACA 65/3-418 root airfoil, a NACA 65/2-215 tip airfoil, 50 percent span, 25 percent chord, flaps, and 44 percent span, 23 percent chord ailerons. The wing area exposed outside the fuselage is 49.6 square feet, and its wetted area is 102.6 square feet. At 207 mph at sea level the Reynolds number per foot of length is 1.94 million. The average chord is 2.7 yielding a wing Reynolds number of 5.15 million. The low turbulence wind tunnel data (1) gives a profile drag coefficient of 0.0047 for the root and 0.0045 for the tip. The resulting drag area for the exposed wing is 0.228 square feet. The slight losses due to turbulent wedges at the tips, roots and landing gear intersections, plus the slight discontinuity at the flap and aileron hinge lines will probably raise the average profile drag coefficient to 0.005, giving an exposed wing drag area of 0.248 square feet. The wing loading is 12 pounds per square feet, the dynamic pressure is 109.6 psf, giving a lift coefficient of 0.109. The induced drag coefficient is 0.00053, or induced drag area of 0.029 square feet.


The 14.5 foot long, 23 inch wide, 35 inch deep fuselage has a length to effective diameter ratio of 6 and a frontal area of 5 square feet. Mike figured the wetted area from the plans and I figured it from measurements that Mike, my son Doug, and I made during the inspection. I cross-checked to within 1/3 of one percent of Mike's figure of 83 square feet. The canopy is 19.1 inches wide and protrudes 9.55 inches above the forebody.

I shall initially assume the fuselage boundary layer is completely turbulent and that there is no roughness drag. The internal flow drag will be ignored for now and it is assumed that the inflow in flight is correct to avoid affecting the external flow at the nose. The basic wetted area drag coefficient is found on the streamlined body charts of Young (2) for transition at the nose (length Reynolds number of 29 million, and length-to-effective-diameter ratio of 6), to be 0.0029. What must we increase this by to take into account the flat faced shape difference from a streamlined body?

It has been found (3) that Navy torpedoes with a flat face of half the body diameter, faired elliptically into the forebody, had the same drag as a streamlined body (of the same wetted area). Still, I will use a 5 percent increase, to acknowledge the shape difference.

The canopy has a raised frontal area of 0.99 square feet. Hoerner (4) gives a frontal area incremental drag coefficient of 0.04 for a clean canopy. Mike has faired his in at the front, thus softening the adverse pressure gradient on the fuselage approaching the canopy. If we use a coefficient of 0.03, we get an increment in drag area for the canopy of 0.0297 square feet. The fuselage as a glider would have a drag area of 0.0029 x 83 x 1.05 + 0.0297 = 0.2827 square feet.

Now we must increase the drag to account for the propeller slipstream. Hoerner gives a value of 7 percent. More recent NASA work (5) indicated that slipstream effects on the mean behavior of the boundary layer are perhaps less drastic than originally assumed. We shall use a 5 percent increase until further data is available. The fuselage drag area in powered flight is therefore 0.297 square feet. The frontal area drag coefficient is 0.059, and the effective fuselage wetted area coefficient is 0.00358.


Mike has not started contracting the fuselage until almost at the wing trailing edge which will help reduce the low wing intersection problem somewhat in the high speed condition, and especially at the higher lift coefficients in the climb. He has also provided a planform radius at the leading edge, which softens the adverse pressure gradient on the fuselage boundary layer as it approaches the wing stagnation. He has a small but adequate radius in the wing fuselage corner as seen in front view, which limits the pile up of boundary layer one finds in a right angle intersection. It is important to do as Mike has done and not overdo this radius, as that would increase the super velocities at the thick point of the wing and steepen the adverse pressure gradient to the rear. The lower surface of the wing is tangent to the lower fuselage, thus eliminating two corners.

Estimating intersection drag is a chancy business, unless one has the new, powerful computer programs as mentioned in John Rontz's fine article in the February 1991 Sport Aviation Magazine (6). In the past, it was set equal to the wing area enclosed within the fuselage, figured at the exposed-wing drag coefficient. On this basis, the 23 by 34.6 in area gives a drag area increment of 0.028 square feet for the intersection. This is 5 percent of the sum of the wing, alone, and body, alone, drag areas. Hoerner suggests a 4 percent increase for each juncture, at normal wing locations. Due to the beautiful filleting job Mike has done I will assume 3 percent for each juncture, or 6 percent of the sum of wing and body. This comes to an intersection drag area of 0.033 square feet, for the high speed condition.


The horizontal tail has 13.26 square feet of area, an average chord length of 1.75 feet, and a Reynolds number of 3.39 million. The 11 percent thick low drag section has a profile drag coefficient of 0.0042 (1) giving a horizontal tail drag area of 0.0557 square feet. The vertical tail has 7.35 square feet of area, an average chord of 2.5 feet and a Reynolds number of 4.8 million. The 10 percent thick, low drag section will have a profile drag coefficient of 0.0038 (1), giving a vertical tail drag area of 0.0279 square feet. The sum of the clean surfaces is then .0836 square ft. This must be increased by 8.7 percent for hinge lines, and each of the 6 junctures causes a 1 percent increase in drag in the tail location. This is less than a wing juncture, according to a study in Hoerner (4) showing the variation in intersection drag with location along the fuselage. We must also account for the influence of the slipstream. If the tail surfaces were made completely turbulent by the slipstream, it could double the profile drag coefficients. Recent NASA studies (5) have indicated the time average effect may be considerably less severe. Until further data is in, let us assume a 40 percent increase. The total tail drag area is, therefore, 0.0836 x 1.4 x 1.062 x 1.043 = 0.13 feet squared. Note that the hinge line and intersection increases as originally figured for laminar surfaces have been considered constant, and are thus a lower percentage increase for the partially turbulent surfaces in the propeller slipstream.


The clean, fixed landing gear consists of two airfoil shaped leg fairings, 21 inches long, 1.38 inches thick, and 4.5 inches in chord. Thickness ratio is 0.307 and chord Reynolds number is 726,000. Frontal area of both is 0.403 square feet, and frontal area drag coefficient is 0.044 (7). Resulting drag area is 0.018 square feet. The 24.75 in long by 8.75 inch deep by 6 inch wide wheel pants, at a Reynolds number of 4 million, have a wetted area coefficient of 0.00465 (2), if completely turbulent. This, times a wetted area of 6.8 square feet for both, gives a drag area of 0.032 square feet. The protruding wheel area is 0.11 square feet and, with a frontal area coefficient of 0.1 (4), yields a drag area increment of 0.011 square feet. The 9 inch long, 3/4 inch diameter tail wheel strut lies at a low angle to the wind and yields a drag area increment of 0.0047 square feet. The three inch diameter, 1.5 inch wide tailwheel has a frontal area of 0.032 square feet, and a Reynolds number of 500,000. Applying the drag coefficient of a supercritical sphere of 0.1, we get a drag area of 0.0032 square feet. Each landing gear leg has an intersection with the wing and one with the wheel pant, increasing the leg drag by three percent, which adds an increment of drag area of 0.0005 square feet. The total drag area of the landing gear is 0.0694 square feet, of which the legs give 26 percent, the pants 46 percent, their interference 1 percent, their protruding wheels 16 percent, tail wheel strut 6 percent, and tailwheel 5 percent. It would be interesting to put one main gear in a wind tunnel to see if the drag is as low as this calculation.


First, let's add up the incremental drag areas calculated thus far for the external aerodynamics. By subtracting this from the total effective drag area found from the top speed of 207 mph, we can see if anything is left for cooling or internal drag.

  • Induced drag: 0.029 square feet ------(03.6 percent of total drag)
  • Wing profile drag: 0.248              (30.8%)
  • Fuselage drag: 0.297                  (36.8%)
  • Wing/body intf.: 0.033                (04.1%)
  • Tail drag: 0.130                      (16.1%)
  • Landing gear drag: 0.069              (08.6%)
  • Total external drag 0.806 square feet(100.00 percent)

As a glider, with the internal system sealed, the total drag area converts to a drag coefficient based on wing area of 0.0146.

It can also be converted to a wetted area coefficient of 0.0034 (by dividing by the total wetted area of 236.4 square feet.)

We can solve for the total effective drag area in flight by using the estimate of top level flight speed of 207 mph, brake horsepower of 65, and 82 percent propeller efficiency. This yields a drag area of 0.88 square feet. Subtracting our total external drag area of 0.806 square feet yields a difference of 0.074 square feet, or 8.4 percent of the total available for cooling drag. The drag breakdown is now:

Induced drag 0.029 square feet             (03.3 percent of total drag) Wing profile drag 0.248                    (28.2%) Fuselage drag 0.297                        (33.7%) Wing/body intf. 0.033                      (03.8%) Tail drag 0.130                            (14.8%) Landing gear drag 0.069 square feet        (07.8%) Cooling drag 0.074                         (08.4%) Total drag 0.880                           (100.00 percent)   Total Drag Coefficient based on Wing Area = 0.016 Total Wetted Area Drag Coefficient        = 0.0037

These final drag figures are quite remarkable for a low wing, fixed gear, tractor propeller, manned airplane. The drag area (which is a product of the size and cleanliness) of less than one square foot has not often been achieved. The wetted area coefficient of 0.0037 at a wing Reynolds number of only 5 million and a fuselage Reynolds number of 29 million, is remarkably low, and it includes all the increases from perfect streamlined body data, including the cooling drag. This cleanliness factor (0.0037) is lower than the lowest number published for propeller driven aircraft in the past of 0.0040 for the P-51 fighter. The P-51 flew at higher Reynolds numbers, had a fully retractable landing gear, and achieved zero cooling drag.

Many aerodynamicists will consider the coefficients of this study as optimistic, but sailplane designers might not, if they had the opportunity to examine the AR-5 as I did. Finally, even if the maximum level flight speed should be 200 mph, instead of 207, and if 72 instead of 65 hp were coaxed from the engine, the drag area would only be 1.12 square feet at 85 percent propeller efficiency, and the wetted area coefficient would be 0.0047. { I think it's more likely that the flight speed is correct, that engine horsepower is down around 60 or less, and that the propeller efficiency is no more than 82 percent. But, of course, I would think that, wouldn't I? M.A.}

The AR-5, and two recent Formula 1 raceplane designs, have demonstrated that quite high performances can be achieved with fixed landing gear, tractor propeller airplanes when laminarized through composite construction, together with great attention to detail design to eliminate all unnecessary sources of drag. While increased gains through laminarization can theoretically be achieved by pusher aircraft, and further reductions in wetted area can be achieved with retractable landing gear, it is not at all simple to beat the simpler configuration in practice. B.H.C.


(1) Abbott, I.H., and Von Doenhof, A.E., "Theory of Wing Sections", Dover Publications, Inc N.Y. 1949

(2) Young, A.D., "The Calculation of Total and Skin Friction Drags of Bodies of Revolution at Zero Incidence", ARC R&M 1874, Apr 1939

(3) Phone call by writer to engineers at Naval Ordnance Test Station, Pasadena 1962

(4) Hoerner, S.F., "Fluid Dynamic Drag", Published by the author, Vancouver, WA 1958

(5) Holmes, B.J., Obara, C.J. and Yip, L.P., Natural Laminar Flow Experiments on Modern Airplane Surfaces" NASA Tech Paper 2256 June 1984

(6) Roncz, J., "Evolution of a Homebuilt Design", Sport Aviation Magazine Feb 1991

(7) Carmichael, B.H., "Two Dimensional Airfoil Literature Survey", North American Autonetics C6-1796/020 Aug 1996

Bruce H. Carmichael graduated with a degree in Aeronautical Engineering from the University of Michigan in 1944. Among his teachers was fellow EAA member Ed Lesher. Bruce later worked at Chance Vought and Goodyear Aircraft in applied aerodynamics. A chance meeting with Dr. August Respet at a sailplane meet in 1949 led to Bruce's joining him in boundary layer control flight research using sailplanes. This in turn led to extension of his research at high subsonic speeds with Dr. Werner Pfenninger at Northrop Aircraft, using an F-94A jet aircraft. He later extended both natural laminar flow and artificial boundary layer control for drag reduction with Dr. Max Kramer, using unmanned underwater vehicles.

He has served on aerodynamic committees for various soaring organizations, and written articles for soaring and aviation magazines. Retired in 1989, Bruce has had the good fortune during his career to return over and over again to the subject of drag reduction and vehicle transportation efficiency. M.C.M. CONTACT Magazine

Crockett Rocket (Pilot Report), Peter Lert, Air Progress Magazine, July1995

"Mike Arnold's little AR-5 puts world-record performance in a tiny package."

By Peter, Lert Air Progress Magazine, July, 1995

Think of world speed records for propeller-driven airplanes and your mind turns naturally toward such brutes as the current incumbent, a Grumman F8F Bearcat modified to the extent that hardly anything is original except the data plate and the shadow. Moreover, the fact that what was already the best-performing piston fighter of World War Two required such extensive modifications shows that such speed records are hard to gain. It took about 35 years for an earlier Bearcat to wrest the title form its former holder, an equally modified Messerschmitt with such radical changes that it was an ME-109 in name only.

Given all the hype that surrounds a new absolute speed record, it's not surprising that some other, more-modest speed records are sometimes eclipsed. That's a pity, though, as in many cases these "class" records are, in their own way, every bit as impressive in terms of aircraft and pilots as their bigger and more-flamboyant counterparts. Moreover, both pilots and airplanes are "closer to home" and considerably more accessible. Thus, I felt honored when Mike Arnold, of Crockett, California, offered me the chance to fly his very own world-record airplane: the remarkable little AR-5.

I was excited, to. After all, few of us are privileged to fly anything that holds a world record of any type (although a number of my flying companions used to accuse me of owning the world's raunchiest 1953 Cessna 180). In Mike's case, the AR-5 has held the world speed record for class C1aO, propeller-driven airplanes weighing no more than 300 kilos (661 lbs), since 30 August, 1992, and it looks like it may continue to hold it for quite a few years to come.

Even more impressive than the record itself - 213.18 mph - is the fact that Mike, over more than ten years of single minded effort, managed to design and build an airplane that breaks an aerodynamic record even when it's sitting still in a hangar. It's the first manned aircraft with a total equivalent flat plate drag area (I'll explain that in a minute) of less than one square foot. This minuscule drag has allowed the AR-5 to reach its heady record speed powered by a totally stock, 65-hp Rotax 582 two-stroke -- the same engine that shoves much lighter Ultralights along at all of 45 mph. Even more remarkable, as aerodynamicist Bruce Carmichael likes to point out, the AR-5 goes that fast with fixed landing gear.

I'd heard about Mike Arnold and his remarkable project for a couple of years before I finally managed to meet up with him at one of Oshkosh's more select and obscure functions: the annual dinner meeting of the True Believers Society, a group that persists in the belief that there is indeed such a thing as laminar airflow over aircraft structures. These meetings generally combine (too much) food and (even more ) drink with at least one lecture or presentation so abstruse that each place setting should include a slide rule as well as the usual knives and forks. Often, there's some empirical aeroballistic research as bread sticks and dinner rolls are hurled at speakers who make outrageous claims.

Mike's unassuming presentation a couple of years ago was refreshing in a couple of ways. Not only was he able to show that one could achieve breakthrough design performance by almost fanatic attention to detail, rather than by any revolutionary new aerodynamic techniques, but he was also able to hold the attention of some 25 of America's finest aerodynamicists for close to an hour...without a single Viewgraph slide or equation!

Even so, more than a year was to elapse before I'd get a chance to be the first pilot other than Mike himself to fly the AR-5. First, the vicissitudes of travel schedules prevented it; then, when my schedule opened up, a broken throttle control forced Mike to make an off-airport landing that required minor repairs. Finally, Mike and I were able to synchronize our lives once again, and by careful planning, I was able to time my arrival in San Francisco Bay area to coincide exactly with last March's "Storm of the Century".

In the interim, however, I'd had a chance to learn quite a bit about both the design and construction of the AR-5 from Mike's fascinating set of videotapes (see sidebar). When I finally met Mike and the AR-5 at the Nut Tree Airport during the one-day respite between two monster storms, I was to find that the airplane more than lived up to all of its advance billing.

So what does it take to go faster than a Bonanza on 77% less horsepower ("and with fixed gear, too!)? Obviously, it takes a smaller, lighter airplane; but even more significantly, it takes one that's much cleaner aerodynamically. Sure, the AR-5 is smaller than a Bonanza -- but if it were to be 77 % smaller to match it's power, it would have a wing span of only 8 feet, and Mike would have to fly it in circles around his head at the local model-airplane field!

True, at 660 lbs (vs 3800 for the biggest Bonanzas) it's not that far from being 77% lighter -- but the real secret is that it has about 80 percent less drag than its production-airplane counterpart ("and with fixed landing gear, too!).

This is where the idea of equivalent flat plate area comes in. Since different airplanes not only are of different sizes, but also fly at different speeds, it's hard to come up with a single yardstick for comparing drag (which changes according not only to the size and cleanliness of a design, but also with the square of its airspeed). Instead, designers use equivalent flat plate area (usually abbreviated as "F"), which expresses total drag in terms of the size of a hypothetical flat plate -- say, a sheet of plywood.

The average lightplane has an F on the order of 10 square feet or less, which doesn't sound like much, but stop and think for a minute. Ten square feet is about the size of, say, a card table -- one of those folding ones we used to carry outside for a picnic. If you're carrying it on edge, it doesn't take much of a breeze to either rip it out of your hands, or knock you over -- 10 or 15 mph would be plenty. Now imagine how hard that table would shove you at 100 mph, and you begin to see why it takes so much power to go fast (and, incidentally, why installing twice as much power doesn't make you go anywhere near twice as fast).

Of course, a flat plate is literally as unstreamlined as you can get, and anything you can do to streamline it will reduce its drag. Otherwise, it would be much easier just to make airplanes cube shaped (are you reading this, Barnaby Wainfan?).

Streamlining even small items can make a very significant difference. For example, many biplanes profit by having streamlined stainless steel flying wires (actually blade like airfoil shapes) between their wings, rather than the simple round cables you might find on an ultra-light. The more you can reduce the drag, the faster you can go; but the faster you go, the more even a small amount of additional drag can slow you down. thus, it's pretty easy to get the first few mph out of a drag reduction program, but each additional knot may cost you more dearly in time, effort and sweat.

I don't even know if a world record was what Mike had in mind when he started to sketch the AR-5. According to him, what he wanted was "a little dogfighter', something he could throw around the sky for fun. At the same time, I'm sure he felt the challenge. As someone very familiar with the composite structures that go into homebuilts, he was also starting to immerse himself in the techniques and art of aerodynamic design as he laid out the parameters of what would be totally his own airplane, rather than a kit or design conceived by someone else.

Weight and cost were no doubt factors as well. To some extent, airplanes cost by the pound, just like any other commodity. More to the point, weight has to be lifted, and while we intuitively think of drag as only the parasitic kind -- the drag of nonlifting protrusions such as landing gear, struts and antennas -- the very act of producing lift itself also produces drag: induced drag. Thus, a smaller airplane is a lighter airplane, producing both less parasite drag and -- if properly designed -- less induced drag.

Moreover, a smaller and lighter airplane can be powered by a smaller engine. It obviously didn't escape Mike's attention that the 65 hp liquid-cooled Rotax 582 is not only significantly smaller and lighter than a Continental A-65, it's also aerodynamically much cleaner and costs -- even brand new -- less than half as much as a well-worn Continental.

There's a lot more to a design, however, than just making it small and light -- and each design decision involves tradeoffs and compromises. Take, for example, the question of wing size and shape. A long, tapered wing like that of a sailplane produces less induced drag, for a given amount of lift, than a short stubby one. One the other hand, it also requires a heavier and more-sophisticated structure for adequate strength and stiffness; so at some point, the benefits of a skinny wing diminish. A rectangular wing has more benign stall characteristics than a tapered one -- but at high speeds, it also has more drag.

Overall airplane layout is also important. For example, there are those who claim that a mid-wing location, with about as much fuselage above the wing junction as below it, is the most efficient. Others, however, hold that much of the drag of an airplane comes from the intersection between the wing and fuselage -- and a high - or low wing layout has only one intersection on each side, rather than two.

What about the landing gear? There's no question that retractable gear have less drag than fixed gear -- but is it possible to design a very clean fixed gear with a drag penalty that is small enough to offset the additional weight, complexity and cost of retractable gear?

These were the kind of questions that concerned Mike Arnold as he laid out the basics for the AR-5. The result is -- as can be expected -- a small airplane, with a wingspan of just over 21 feet. It's also light; at max gross weight, wing loading is only about 11.8 lbs per square foot, a bit less than half that of a Bonanza. The aft fuselage is fairly short; while this requires good-sized tail surfaces for stability and control, it's worth it in terms of decreased weight and wetted area. The nose is long, partly because of the light weight of the little Rotax and partly because long, skinny shapes tend to have less drag than short, fat ones (Gee Bees notwithstanding).

As some great artist once said, "God is in the details," and this is where the brilliance of the AR-5 really shines through. Take the landing gear, for instance. It's conventional, of course, with its two long legs, nicely faired and far enough outboard that they're not exposed to high-energy air from the prop (which, given its tiny size, isn't all that far outboard anyway). An additional benefit of this wide stance is that it makes the airplane surprisingly docile on the ground. Spring shock struts, with a couple of inches of travel, are built into the legs. The wheel-pants are what you'd expect of a high-speed aircraft: small and tight, with an extended afterbody and almost no clearance around the tire. What's different is the way they fair to the struts: Not symmetrically, but offset all the way to one side, so that there's only one drag-producing intersection rather than two. A long, curved, tubular spring fairs aft out of the tailcone, supporting at its end a tiny solid tailwheel.

Similar details about all over the airplane, including a flush-fitting fuel filler door and a combination fuel-tank vent and filler-drain scupper all of a half an inch tall -- everything carried out at a level of workmanship that rivals or surpasses the most expensive German sailplanes. Some of the most significant details, though, aren't all that visible; the overall shape of the fuselage and its relationship with the location of things like the wings and cooling-air outlets.

Mike studied most of the classic of aerodynamics to find out that it's not just the shape with which an airplane meets the oncoming air that's important; equal, if not more important, is the shape with which it leaves the air behind as it passes. Mike found that the AR-5 was just about equally fast with a big prop spinner, a little one, or none at all.

Sudden transitions in the cross-section of an airplane cause drag, whether they're increasing or decreasing -- a low-speed version of the area rule that makes Coke-bottle shapes more efficient for jet fighters. Mike was able to work these factors very much to his advantage. For example, the nose of the airplane is long enough that the airflow has a chance to align itself (aided by outflow from the radiator cooling outlets) before it gets to the wings. About the time it leaves the trailing edge, both the presence of the canopy and some very carefully shaped fillets keep the cross-sectional area near constant; then, as the aft fuselage taper, the job of maintaining areas is taken over by the tail surfaces.

The final important factor was not only the choice of an airfoil, but the precision with which it was executed. Hundreds of hours of painstaking work resulted in a wing on which irregularities are measured in thousandths of an inch and on which the airflow remains laminar -- flowing smoothly along in a sheet rather than tumbling in microscopic whorls and ripples -- back to an unprecedented 70 percent of the total chord.

Overall, the result of all these design decisions came out looking a bit like a cross between the longnose Ta-152 version of the Focke-Wulf 190 ahead of the wing, and an F4U Corsair from the canopy back, with elements of 1930s Bendix Trophy racer thrown in.

There's an old adage that says, "An airplane that looks good flies well," and I was to find that the flying qualities of the AR-5 certainly bear this out. At the same time, the airplane has a few idiosyncracies...which isn't unexpected in something that's really intended to be flown by only one person thoughout its career.

To get aboard, for example, you first put a towel down on the wing to avoid marring its pristine surface. Mike had to advise me exactly which (unmarked) postcard-size area of the wing had the additional stiffening to take my weight. Once in the comfortable fixed seat, I was presented with very basic instruments (airspeed, altimeter, tach, coolant temperature and EGT) and a handheld radio in a convenient little clip. There's a good-sized center stick; under the panel, it has an adjustable bobweight -- not to increase pitch forces or stability but just to prevent the weight of the curved stick itself from contributing to a G-induced pitchup. Somewhere up ahead under the float-gauge-equipped fuel tank are the rudder pedals and toe brakes; a two-notch flap handle is on the left sidewall. Pitch forces at any airspeed are light enough that elevator trim is neither needed, nor installed.

With the four-point harness fastened and the canopy locked, a flick of the ignition switch and a jab at the electric starter brought the Rotax to its usual slightly rough, blue-smoking idle at 3600 rpm to prevent gearbox chatter (the prop turns at half the engine), but that power was more than sufficient to trundle the AR-5 along at a brisk rate.

Direct tailwheel steering made it easy to fishtail for forward visibility; in fact, with that long , round cowl out ahead, the view is quite P-51-like on the ground. With the open tailcone right behind the pilot's ear and that tiny solid tailwheel rolling along Nut Tree's slightly rough asphalt, the effect was exactly like that of the old RCA Victor gramophone logo, with me playing the role of Nipper the dog.

Startup and taxi also brought home the AR-5's most significant idiosyncrasy, at least from the piloting standpoint: The throttle works backward! I'm not sure whether Mike did this to make things simpler or just to save weight (not that one can be profligate with the ounces -- the airplane weighs 488 lbs empty, and Mike weighs around 145, leaving only 27 lbs for fuel on world record attempts.)) But since the slides in the twin Bing carburetors on the Rotax are pulled out to open the throttle, a simple pull cable attached to a vernier throttle on the panel handles the chore instead of an elaborate linkage.

I found that as long as I used the vernier feature and remembered the old Spitfire pilot's expression of "opening the tap" for more power, things worked fine; but when I pushed in the center button and moved the throttle normally, I tended to get crossed up.

With no elevator trim and only a single "either it runs or it doesn't" switch for the Rotax's dual ignition systems, there isn't much to check before takeoff, so I line up on Nut Tree's runway 20 and opened the tap all the way. With only about 40 of the 65 hp available initially due to the aggressively pitched prop, acceleration isn't exactly neck-snapping at first, but the AR-5 moved out quite smartly nonetheless, and as advised by Mike, I raised the tail at about 45 mph. I expected a swing to the right (the prop turns "the wrong way"), but it was so minor, it was almost imperceptible. As soon as the tail comes up, the visibility is excellent, and the airplane leaves the ground very comfortably at about 60 mph.

Mike had warned me of another slightly odd effect: Since the prop is pitched for high-speed flight and turns pretty fast, it's at least partly stalled during the initial part of the takeoff. As speed increases and the prop finally "hooks on" to the air, the engine seems to sag momentarily; even so, the airplane continued to accelerate.

Mike had advised a climb speed of around 100 mph, at which the airplane climbed at better than 1000 fpm with excellent visibility. The air was quite bumpy, and the light wing loading made itself felt; on the other hand, the combination of good damping and very powerful controls made it easy to compensate for the gusts.

Pushing over in smoother air at 4500 feet, I let the AR-5 wind up toward cruise speed, and discovered more evidence of Mike's craftsmanship. Good laminar airfoils have a particular range of angles of attack over which they attain especially low drag (the so-called "bucket,"), and as the ship accelerated, I could feel it drop into the bucket very perceptively. This also let the engine wind up toward peak power; I throttled back...er, forward -- anyway, I "screwed in the tap" until things settled at 5500 rpm and an indicated cruise of about 160 mph, then I started feeling out the handling.

It was, in a word, delightful. Pitch forces are light, but not overly so for this class of aircraft; stick-free stability appeared just about neutral, perhaps just a hair divergent. At any rate, the phugoid period (if it even has one with me aboard) seems so long that I gave up trying to time it after about a minute. However, I weigh about 25 lbs more than Mike does, and after running the numbers a day or two after my flight, Mike noted to his embarrassed surprise that I was flying at a CG significantly farther aft than he ever had, despite some lead ballast on the engine mounts.

Roll rate is good (estimated at around 2.65 seconds for a full 360 degree roll), and roll acceleration -- the initial start of a roll out of level flight, which really gives the subjective impression of roll rate -- is even better. My only cavil there is that while both the ailerons and the elevator get somewhat heavier with increased airspeed, the ailerons "heavy up" slightly faster. Control harmony is well-nigh perfect at lower speeds, but pitch is a bit sensitive at higher ones. The rudder is very light and powerful throughout -- in fact, I probably wouldn't have minded if it were a bit heavier -- but there's so little adverse yaw from the ailerons that most evolutions, including aileron rolls and the dogfighting that Mike loves, can be executed "feet on the floor". I assayed several rolls, including one gingerly four-pointer (going negative halfway around would have stopped the engine, with its flat-type carburetors), and found that I could reach comfortably brisk roll rates without ever coming near the full travel of the stick.

I was also impressed, particularly in so light an aircraft, by how well it could maintain energy under increased G loads. "Windup" turns at full power could be held until the outside world started going a bit gray around the edges (for me, somewhere between 4 and 5 G) before the speed started falling. On the other hand, one can certainly tell when one finally leaves the laminar low-drag "bucket". Get below about 110 mph while pulling G, and the AR-5 feels like it's run into a wall of feathers. Of course, the "peakiness" of the two stroke's power curve contributes to this as well. As the airplane slows, the engine also drops out of its best-power range, and it takes what seems to be a long time to get things to wake up again.

Things are equally nice at the low end of the speed range. The airplane can be carefully worked into a stall (at 56 mph clean and 53 dirty) with almost no perceptible break, and it can be held level with ailerons and rudder while the sink rate builds up. Pulled up more briskly, particularly with full flaps, it tends to drop the left wing, although I was able to pick it up with rudder by about 45 degrees. Mike has spun it a half turn and reports no indication of developing problems...but I'll leave that to him.

I made a long, gradual descent back toward the Nut Tree. Mike had warned me that the Rotax tended to go lean at high airspeeds and intermediate throttle settings, requiring either more power (and higher speeds than I cared for in the rough air) or less airspeed. Arriving overhead for a high, 360 degree approach, I closed the throttle, waited what seemed like forever to get down to the 85 mph speed for the first notch of flap, and added the second on base leg. With full flap, the AR-5 comes down very nicely, with the nose down out of the field of view.

Some sink on short final called for a little power. Crossing the threshold at 80 mph, I did what I'd planned before the flight: I closed the throttle all the way, then immediately stuffed my left hand under my thigh to preclude my doing anything stupid with it.

As it turns out, it was no problem. Mike had advised me to make a wheel landing, since the three-pointer tends to scrape the aft ends of the wheelpants. Forward visibility was excellent all the way to touchdown, and the spring shocks in the gear legs soaked up the actual moment of truth to the point where I barely felt it. Despite gusts, the very powerful rudder and wide stance of the main gear made it a no-brainer to keep things straight until I could lower the tail, then pike it down with full aft stick for maximum tailwheel steering effectiveness.

So, that was my flight in a world-record airplane. I hope I get the chance for some more time in it. Mike certainly achieved his goal, whether primary or secondary, of a very small, high-performance airplane that's also loads of fun to fly. This is not one of those all-out machines, like an America's Cup yacht, that has to be kept in a velvet-lined case when not in use. In fact, with a cruise range of about 500 nm, it would make a neat little traveling machine; I only hope Mike can be persuaded to take it to Oshkosh this year. I'd be happy to ferry it there for him if he can't spare the time.

Peter Lert, Air Progress Magazine, July 1996

At last, something worthwhile for us couch potatoes, Peter Lert, Air Progress Magazine, July 1995

Peter Lert, Air Progress Magazine, July 1995

The AR-5 is such an impressive project that it's very easy to forget that Mike Arnold isn't an aeronautical engineer (although by now, of course, he is one, even if he doesn't have some fancily engraved sheepskin on his wall). In fact, he started his career (and has a degree) in an entirely different direction -- as a filmmaker. I never asked him if his initial exposure to composite construction techniques (at Fred Jiran's Glider Repair in Mojave) came from interest or a budding filmmaker's typical lack of gainful employment in his own field...but he's released a set of videotapes, commonly called the "The AR-5 Tapes". These tapes show that he certainly hasn't lost his touch behind (or in front of) the camera.

At the time of this writing (1995), there are two tapes in the series (but a third is in production that may even show a few moments of your. obedient. servant. flying the airplane [ note: Peter's pilot report is featured in "The AR-5 in Action", disc 4, MA, Dec 2010] ). One, at something over an hour, is called "Why It Goes So Fast." The other, at just under two hours is called "How It's Made."

Each tape appeals to a somewhat different interest among homebuilders. "Why It Goes So Fast" begins with a description of the actual world-record flights, which is fascinating and exciting in its own right. From there, Mike goes on (aided by noted aerodynamicist Bruce Carmichael) to explain the various design features that contributed to the airplane's stunning performance, as well as the reasons behind them. While he sometimes uses very clear blackboard illustrations to explain some of the points, most of them are shown on the airplane itself, which really makes them real for would-be aircraft designers.

In "How It's Made", Mike turns adversity into advantage. The tape was filmed in Mike's tiny shop in Crockett, and at the time it was produced, the airplane was laid up (pun intended, for you composite fans) for repairs after a power failure and off-field landing. Once again, the film begins with some real-world action -- in this case, the disassembly and recovery of the airplane from the field next to Lake Berryessa, where it ended up. From there, however, it goes back to basics, as Mike explains every stage of moldless composite construction, beginning with the hot-wiring of foam cores and continuing through all the stages of composite layup.

He doesn't just cover primary structure, either; he also describes the construction of complex subassemblies like fuel tanks and nifty little features like access doors. There's a good discussion throughout of the various materials and processes that are used.

What I particularly like about both tapes is that they combine a complete lack of pretension and overly slick production techniques with solid, professional filmmaking. There's none of the camera shake or jumpy editing common in amateur videos (assuming those are edited at all!), and while this is clearly not a studio production, the shots are carefully set up and properly lighted. At the same time, while Mike and his helpers are clearly not working from a word-for-word script, it's equally clear that they didn't just jump into the process cold. In fact, there's a very logical and obvious progression through the shots and sequences, and the occasional minor blunder -- say, spilling a bit of resin -- only adds to the cinema verite effect.

Overall, the effect is exactly what I imagine Mike was trying to achieve: The feeling of being in the shop of a very experienced and competent composite homebuilder, and looking over his shoulder as he goes about his business and explains informally what he's doing. I recommend both films very highly to anyone who's either building a composite homebuilt (whether from scratch or from a kit), or even just contemplating building one. The second film, in particular, is a great way to see what composite construction techniques are like and to decide if they appeal to you -- before you start messing up your garage. In fact, you don't even have to move out your Weber grill!

Peter Lert, July 1995

Builder's Bookshelf, Dave Martin, Kitplanes Magazines, Aug. 1996

The AR-5 Tapes 3 and 4: "Moldless, Low Drag Wheelpants" and "Making Fiberglass Molds"

Produced by The Arnold Company, 1203 Wanda Street, Crockett, CA 94525; VHS Video Tapes, 73 and 66 minutes respectively; $29.95 each

More than two years ago we reviewed Mike Arnold's tapes 1 and 2 about designing and flying his record-setting, extremely low-drag AR-5 composite airplane. His new Tape 3, "Moldless, Low Drag Wheelpants", follows Arnold as he designs and builds a set of replacement wheelpants for the AR-5 after a landing incident destroyed the first set. Starting with a fineness ratio recommended by Hoerner, Arnold's process shows how to design and make your own landing gear fairings and wheelpants.

Every step, process and material used is covered in detail, and the final product is a pair of custom pants that weigh just 2.35 pounds each: half the weight of mass-produced pants and obviously lower drag than you can buy. At tape's end, Arnold tells why he abandoned his original plan to retrofit the AR-5 with retractable gear. The answer is that he believes that his fixed gear offers lower drag -- not to mention less complexity, weight, and cost -- than he could achieve with the best-devisable retractable system.

Tape 4, "Making Fiberglass Molds" is a similar step-by-step tutorial on the process of turning out highest-quality identical composite parts. The example is a complex six-part underwing cargo carrier that fits precisely on an RV-4 or RV-6. Beginning with a sketch, followed by a full scale drawing, templates, carved foam plug, and a series of female and male molds that incorporate joggles and all necessary details, this is a complicated process that would logically be attempted by a company, an EAA chapter or other building group that expects/needs a considerable number of copies of the final product. It's obviously no weekend project to produce professional-quality production molds. But the video covers every step in enough detail that you could emulate the process.

Both tapes are of top professional quality including excellent photography, well-planned running commentary by Arnold plus occasional asides by a narrator and a few clarifying sketches. I even liked the wide variety of noncontinuous, subtle background music that seemed appropriate to the level of concentration and skill required by some of the steps.

Beginners in composite construction should check out these tapes if only to see and hear a master composite craftsman (who is also a record-setting designer and pilot) at work. Mike Arnold's video documentaries are downright inspirational! --Dave Martin

Checking out a Record Setter (Pilot Report) , Dave Martin, Kitplanes Magazine, Oct. 1999

Checking Out a Record-Setter

Is Mike Arnold's AR-5 the world's lowest-drag propeller airplane?

By Dave Martin, October, 1999, "Kitplanes Magazine


What would you do if you were invited to fly a one-of-a-kind, hand built, world-record-setting airplane? You would probably do what I did: think about it, research it, and accept the invitation.

 The call came from Mike Arnold, who spent 10 years designing and building his AR-5 tail dragger that set a world speed record in 1992 in the FAI C1aO class for airplanes weighing less that 661 pounds at takeoff. The 2-kilometer closed-course AR-5 record, set in August, 1992, was 213.18 mph on AR-5's 65-hp Rotax 582 two-stroke engine. The record stands to this day.

 At the time of his call last spring, Arnold and a friend of mine, writer Peter Lert (who has written about other subjects in KITPLANES), were the only two people to have flown the AR-5. "I'm thinking of selling the AR-5," Arnold said, "and I'd like you to have a chance to fly it before I do."

Research Time:

 When in doubt, check it out. I reread aerodynamicist Bruce Carmichael's October 1993 KITPLANES article on the AR-5. The airplane is built entirely of fiberglass and foam using the moldless composite technique pioneered by Burt Rutan on the VariEze.

 The AR-5 was intended originally as a fast, personal sport plane that Arnold could use to keep up with his father in his Thorp T-18 and friends like Kit Sodergren in his Midget Mustang--without the cost of buying and operating a Lycoming or a Continental.

 Rather early in the design process, Arnold realized that he could set a world record with the AR-5 (his fifth design but first construction, by the way); the previous C1aO record was near 120 mph.

 Visiting the project, Carmichael was amazed to discover incredible attention to detail both in design and construction. Laminar flow over much of the wing's surface would be critical to drag reduction. The 8:1 aspect ratio wing features a NACA 65-418 airfoil at the root tapering to a NACA 65-215 at the tip. This wing would promote superior laminar flow if smoothness and lack of waviness were good enough.

 Using reflected light, Carmichael looked for ripples and saw little waviness. He them rocked a steel straight edge fore and aft on the wing, listening and feeling for unevenness. Finding little, he measured waviness by moving a dial indicator along a piece of masking tape placed in a chordwise direction on a wing. The indicator was centered between two pegs 2 inches apart. His largest peak-to-peak reading was 0.0036 inches over a 3.6-inch length, revealing a waviness of one part in 1000. Farther forward on this chord line, waviness was found to be only one part in 4000. Remarkable!

 The fixed landing gear,engine cowling, cabin air intake, empennage treatment, and the wing/fuselage junction were all found to maximize best drag-reduction techniques.

 Using an estimated fixed-pitch propeller efficiency of 82% and the record-setting speed on 65 hp (which was purposely flown at an allowed descent angle of 1 degree 18'), Carmichael determined that the AR-5 has a drag area of only 0.88 square feet. Formula1 air racers come close to this figure, but it is possible that AR-5 has the lowest drag and the lowest drag coefficient of any man-carrying, propeller-driven airplane in the world. Wow!

I called Peter Lert about flight characteristics.He noted the left-turning propeller, the sensitive rudder, and the somewhat disconcerting loading of the high-pitch cruise propeller late in the takeoff run. The cruise prop unstalls and loads the engine, dragging rpm down about the time you get airborne. Arnold had said I'd fly with a climb prop, which doesn't have this annoying problem. Lert assured me that I'd like the airplane.

Putting It Together:

 A few days later I called Arnold, and we set up a schedule to get together near Sacramento, California. Thirty minutes later, Bruce Carmichael called to sell me on an article idea, and he mentioned the AR-5. We hadn't talked in a year. "Did Mike Arnold tell you I'm about to fly it?" I asked. "No," he said. "I haven't talked with Mike in a year and a half." Talk about a coincidence!

 On the appointed morning I arrived at Sacramento International Airport on schedule and was met by Harry Arnold, Mike's father. We drove to Yolo County Airport, where the AR-5 is based. I'd arranged with Ray Ferrell of Sky Dance Sky Diving on the airport to photograph the AR-5 in the air. Strapped to the right front floor of the Cessna 180 and facing backward to shoot out the open door, I motioned Mike and the AR-5 into various positions as we circled. You see the result here. {We aren't able to reproduce Dave's beautiful pictures here, so we've substituted some of our own shots for the web page. MA}

Covering the Quirks:

 Back on the ground after 20 minutes, Arnold prepared me to fly the AR-5. As we looked into the cockpit, he described the controls. They seemed conventional until he got to the throttle, which is hooked up backward. Pull for more power and push for idle. What?! "I know. Peter Lert screamed too. But he found it not to be a problem," Arnold said. He says he rigged the throttle this way because it was lighter and simpler...and because he intended to be the only pilot.

 There's a vernier on the throttle that helps set power precisely. In this case it also slows throttle application, which is helpful with a nonstandard installation. My experience, it turns out, was like Lert's; the screwy throttle wasn't a problem.

 Next Arnold covered an AR-5 powerplant characteristic that could be a problem. Because of the propeller's high pitch and the airplane's high speed, reducing power to midrange during a descent can result in overheating the engine enough to seize it. How's that?

 Pulling power (which in the AR-5's case means pushing the throttle) in most fixed-pitch airplanes means reducing engine rpm, even in a descent. But because of the high pitch of the AR-5's propeller--even the climb propeller--the engine tends to maintain its cruise rpm in a descent with the throttle back some (err, forward; you know what I mean). The result is reduced fuel and the same amount of air: a leaner mixture that results in instantly higher EGTs. Keep the EGT to 1200 degrees F or less, Arnold cautioned. Let it reach 1450 degrees F and you stick aluminum parts together. The solution in a descent is to leave full power set or to reduce it to idle. The technique works.

One other unusual feature of the AR-5 would be anticipated by anyone who has flown a composite taildragger with a tiny tailwheel: extremely noisy taxi. "You're the dog listening to His Master's Voice," Arnold said, referring to the old mechanical RCA Victrola record player. The pilot sits at the end of a megaphone attached to the needle-size (2-inch) tailwheel scratching along the concrete. "When the tailwheel contacts the runway after your wheels landing," Arnold predicted,"you'll think it came off." Fair warning.

Flying It:

 After watching Arnold take off, fly the pattern, and land using his recommended wheels-landing technique, I checked the airplane externally and scrambled aboard. There's not much to check in the cockpit. Controls free. Flaps retracted for takeoff. Ignition switch on (there's a single electronic CD ignition that sparks a pair of plugs in each cylinder). Clear the area and start. Canopy latched and locked. Toe-operated wheelbrakes are moderately effective.

 The first surprise was how good visibility is while taxiing. Cushions below and behind achieves about the eyeball position for me as for Arnold without them, and I could see the taxiway everywhere except directly ahead. Little S-turning is needed to clear the path. I set 3000 engine rpm (the prop turns half as fast) for taxi to minimize clatter and wear on the speed-reduction gearbox.

 On the runway, I slowly dialed in some power and eased the stick forward to raise the tail as the airspeed indicator came alive. Because the prop turns counterclockwise, raising the tail requires a little right rudder because P-Factor is momentarily reduced. On getting airborne, a touch of steady left rudder is needed to counteract P-Factor in the climb. Immediately apparent during the takeoff run is that the rudder is highly sensitive. A bit more practice would be required to achieve a smooth, straight takeoff.

 I aimed for 110 knots to keep the Rotax's coolant temperature within limits, and that results in a less-than-spectacular climb angle, although the rate is acceptable. Leveling initially at 2500 feet west of the airport, the AR-5 confirmed Arnold's note that no rudder is needed for rolling maneuvers at cruise airspeed. Setting a moderate 5500 rpm achieved close to 140 knots level, and I set up for my standard 45 degree-to-45 degree roll rate check.

For an airplane with a 21-foot wing with relatively high aspect ratio (8:1), the AR-5 rolls remarkably fast: not much more than 1 second from 45 degrees to 45 degrees. The roll is equally rapid both directions, and little or no rudder is needed. "You can roll or loop at 120 knots," Arnold had said, and for a change I took him upon it and tried an aileron roll each way. Really nice!

Next came the stick-free pitch stability check. For this, we need hands-off, trimmed flight, and the AR-5 has no trim control. But with my weight and this loading, the plane flies level without help at 135 knots. After easing the stick forward a bit, I let go and waited. The lazy pitchdown slowed, reversed upward and passed through the horizon going up. Pitchup slowed and reversed, and this time the pitch-

down angle was less than before: Damping indicated positive pitch stability at this configuration. The rate was long --40 seconds per cycle-- but stability was there.

 Slow flight and a first use of the three-position flaps followed. Maximum flap speed is 95 knots, and I simulated flying a landing pattern at 3000 feet using a road for orientation, remembering to "push" the throttle to idle before descending. Fly downwind at 110 knots, turn base slowing to 100, apply flaps and continue slowing to 80 knots.The descent with full flaps is steep, and the intent is to flare low to a level-attitude wheels touchdown.

 Approach and departure stalls revealed that the AR-5 is docile at this edge of the envelope. A gentle stall break occurred at 56 knots with flaps up and 52 knots with flaps down. Arnold says the ASI indicates somewhat too high at the low-speed end of the dial.

 A last check before the first real landing was a full-throttle level run. Wearing its climb prop, the AR-5's Rotax can exceed the marked 6500 rpm limit, and I made it a point to reduce power as the tach needle wound up toward the engine limit. Indicated airspeed (which is quite accurate at cruise and faster speeds, Arnold says) was near the top of the yellow arc: about 165 knots.

 Lacking an outside air temp gauge, I can only estimate temperature at 3000 feet msl. If the guess of 78 degrees F is close, true airspeed was 178 knots (207 mph) on the climb prop.

 Entering the left 45 degree leg for Runway 34, I tried to duplicate the higher-altitude dry run: 110knots on downwind, slowing to 80 with full flaps on final, flattening the final approach with a bit of power. Touchdown in a level attitude was soft and looked normal and I relaxed, which was a mistake.

 Failing to ease the stick forward upon touchdown, and also leaving the flaps down, I found myself back in the air a foot or so after a 5- or 6-second roll. A couple of ungraceful runway contacts followed, and the tailwheel megaphone let me know when it was firmly on the runway.

 Fortunately, none of the several runway contacts scratched the rear of the wheelpants, which is one reason Arnold makes wheel landings in the AR-5. Missing the midfield turnoff, I slunk to the far end of the runway having bruised nothing but ego.

 Followup back at the hangar:

 Arnold reminded me of some of the details required to achieve the AR-5. After a 10-year career as a filmmaker, Arnold turned his interests and talent to aviation, where he worked on the composite Amsoil Racer designed by Burt Rutan. An apprenticeship with composites guru Fred Jiran explains the AR-5's gorgeous, low-drag conception.

 Engine cooling was initially a problem, and Arnold spent countless hours on baffling. A special oval exhaust expansion chamber was designed to fit under the slim cowl. When a Rotax 582 replaced the original Rotax 532, the 582's oil injection system had to be removed as it would not fit.

 Arnold has fine-tuned the AR-5 in the years since the world record. He changed stick force ratios and made other modifications including lightening aileron forces and increasing rudder force a little.

 Before leaving for home, I told Arnold that the AR-5 is one of the handful of airplanes sampled in this job that are memorable because of their excellent handling. I compared it to the feel of the Stelio Frati-designed F.8L Falco (available as a kit from Sequoia Aircraft).  Mike Arnold understood the compliment.

-Dave Martin, Kitplanes Magazine

The AR-6: My Formula 1 Design

The AR-6, my Formula 1 racer design, flew for the first time in April, 2005. The airplane is currently owned by Steve Senegal of San Bruno, CA. It was built and raced by David Hoover in 2005, 2006, and 2007, finishing second in the first two races and first in the Gold race in 2007. In 2008 new owner Steve Senegal took the plane to victory again in the Gold race, and in 2009 he qualified first but had engine problems and did not finish the Gold race. He won again in 2010. He was top qualifier in 2011, but the races were cancelled after the tragic crash of an unlimited racer into the spectator's area. In 2012 "Endeavor" set a new race-lap record of 260.775mph, and won the Gold race again. In 2013 it qualified first but Steve was unable to overcome a slow start and finished second in the Gold race. In 2014 he set a new qualifying lap record of over 267mph and won the Gold race again.

For more information about the AR-6, see articles below:

Magazine Articles about the AR-6:

+ ENDEAVOR, by Jack Cox, Sport Pilot Magazine, Winter, 2006

+ The AR-6 Racer, by Michael Friend, Todays Pilot Magazine, Mar 2006

+ Formula One, by Tom Wilson, Kitplanes Magazine, May 2015

AR-6 Images   - The last three images are of a 42% scale model

We've recently finished a movie showing how we made the master plug for the curvaceous, molded fuselage of the AR-6. It's called, "Making a molded fuselage-Shaping the AR-6"


Email me at: marnold@AR-5.com