Thirty-five years ago this month, the first two-seat aircraft to bear the RV moniker took flight. The RV-4 was more than just a stretched RV-3, and it went on to inspire a generation of builders who realized that while a single-seat airplane was a wonderful machine for a pilot, the future of spreading aviation was going to be with airplanes that could carry a passenger to enjoy the experience. More than a generation later, the RV-4 kit is still available, and it continues to be an exciting sport plane that is a delight to fly. According to Van’s Aircraft, as of May this year, 1367 RV-4s have been reported as completed and flying—that’s a respectable number for a kit that is not fully pre-punched, match-hole drilled, and requires jigging to build a straight ship. It’s old school. This month we take a look at this highly successful airplane from the early days of kit building—and remind potential builders that the kit is still out there if they want to experience what Van’s refers to as “total performance.”
Genesis
The RV-4 concept grew out of the original Van’s kit, the RV-3. Van’s Aircraft was, at the time, a very small company, working hard to produce plans and parts for the single-seat airplane that was astounding people with its performance and handling. Although very primitive by today’s kit standards, a reasonably competent builder could learn the skills necessary to construct the all-metal low-wing monoplane and enjoy a delightfully well-balanced machine when they were finished. The problem was that it was still a single seater, and while the fact remains that the majority of sport flying is done solo, having an extra seat that you can at least offer to a friend (or spouse) is a powerful draw when trying to justify building and owning an airplane on a working-person’s budget.
A modern RV-4 panel is simple to create with a single EFIS screen, a radio and transponder. Keeping it simple, light, and inexpensive is the goal for most RV-4 builders and pilots, and the latest VFR EFIS products are often cheaper than a panel full of gauges.
Once it was decided to build a two-seater, the first question had to be tandem or side-by-side. According to Van’s, a poll of prospective customers showed a strong preference for a tandem configuration, keeping the pilot on the centerline of the aircraft and keeping the frontal area as small as possible. While a casual look might suggest that Van merely stretched the basic RV-3 to create the -4, the truth is that the RV-4 was a clean sheet design, borrowing heavily on the experience of designing the -3, but using all new parts and several new design concepts.
Aileron trim is not required, but it sure can be nice in an airplane without an autopilot. This custom made trimtab has more authority than the factory spring-bias system, and was designed by the builder.
Similarities abound, of course. The flip-over bubble canopy was a simple and light way to give the pilot (and now the passenger) tremendous visibility all around. Gear legs attached to the engine mount made for easier structural attachment of the wheels. The pushrod control system came directly from the RV-3 and has survived in all of the RV models to date. Simple, sound structural design practices were carried along because they worked well and provided aerobatic structures at a minimal weight. The distinctive cheek cowls that enclose the cylinders, yet provide minimal volume are there on the -4 as well, causing some to confuse the two airplanes when viewed at a distance. The easy way to tell if the airplane coming up the taxiway is a -3 or a -4 is to look for the roll bar under the middle of the canopy—if there is one, then it is a -4 (the roll bar separates the pilot and passenger). If not, it’s a -3 (or someone left an important part off of their -4).
A professional machinist, Dayton Murdock has several unique pieces of hardware on his RV-4. This latch is used to secure the canopy in a slightly-open position for ground operations when extra ventilation is desired.
There are quite a few places, however, where differences can be found. Stand an RV-3 and RV-4 next to each other and the dimensional contrast is apparent. The RV-4 stands taller and looks bigger all around because it is—the wingspan is greater by three feet, and the chord is larger as well. The firewall structure on the RV-4 is more complicated than the flat plate on the -3, with a bump out for the pilot’s feet in the -4 providing a clever way to stretch the cabin for two without having to make it excessively long. The tail on the RV-4 sports balanced elevators that the RV-3 lacks, and is larger to boot. While today’s kit buyer for either airplane will find some shared components, such as aileron bellcranks and some welded bracketry, most of the parts for the two kits are unique.
While RV-3 tail kit sales are rare, Van’s reports that they still have people starting RV-4s on a regular basis—a testament to a good design that provides pilots what they want—a sporty two-seater in a smaller package than the RV-8.
Flying a Late Model RV-4
The RV-4 used for this report was built by Dayton Murdock of Carson City, Nevada, and is an excellent example of a recently-built aircraft with modern equipment and lessons learned from decades of previous RV-4s. The workmanship is excellent and evidence that the kit, while not pre-punched or match drilled, is mature. Equipped with an O-320, P-Mags, and a Catto prop, the firewall-forward installation reflects modern equipment that most builders would consider today. While some RV-4s sport constant-speed propellers, more often than not, you will find them simply equipped with a high-performance, lightweight, fixed-pitch prop like this one from Catto. Electronic Ignitions are likewise becoming more common, and reports of fuel savings on the nature of a half-gallon per hour, smooth starts, and smooth running are hard to beat. As a bonus, the ignitions work better with automotive spark plugs, which are far less expensive than the aviation plugs used with regular magnetos.
I flew Murdock’s airplane solo, with about half fuel, from Carson City airport, a field at an elevation of 4700 feet msl. Surrounded by mountains, Carson City is a great place to have the excess horsepower of most RVs—the altitude is hardly a factor, even in the heat of summer, since the airplane climbs reasonably well almost up to the beginning of the flight levels. This cool, late-winter morning, the temperatures were about 40 F at the surface and dropped to freezing at our test altitude. This made the atmosphere slightly lower than standard, and provided a good bite for some maneuvering and aerobatics.
Who says you can’t build complex curves in metal? These wingroot fairings were made the old fashioned way by the builder—stretching and shrinking for a perfect fit. Murdock’s canopy skirt is also aluminum, built per plans for a great fit.
Murdock recently switched the instrument panel to an all-EFIS cockpit. Equipped for day/night VFR with an AFS 4500 EFIS, a Garmin SL-40 for com, and a Garmin GTX-327 for transponder, the machine has plenty of what you need to have fun and fly comfortably on cross-countries using the mounted Garmin 396 GPS. He is considering adding an autopilot for longer cross-countries, but has taken it to Oshkosh several times without one and finds it a comfortable airplane to hand-fly.
A single short row of switches along the bottom of the panel controlled everything necessary for flight. Start-up was quick and simple, with the P-Mags providing a hot spark for a start after two of the three blades passed by the windshield.
Murdock builds and sells his own line of unheated—yet elegant—pitot tubes, so of course, his RV-4 sports one of them. These special touches are common in RV-4s—airplanes that invite customization because the kits themselves require a little more initiative on the part of the builder.
As taildraggers go, the RV-4 is a pleasure to taxi—there was no wind, but the airplane tracked true and solid, and the visibility over the nose was better than what most taildragger pilots have grown up with. The center portion of the cowl blocked the horizon, but it took only a couple of degrees of an S-turn to see over the cheek on either side, so you could effectively taxi straight-ahead and see most everything you need. I have found that cushion height has a lot to do with the over-the-nose visibility in the various RV-models, and a good view can generally be found before the pilot’s head hits the canopy. This RV-4 has the now-standard long gear legs, raising the nose just a little, but it was still better than what you see out of most RV-6s.
Simple fixed-pitch airplanes are a pleasure to fly because there is hardly any checklist to perform—a good CIGAR check will see you safely off, and that was the case here. The cool mountain morning lead to a quick takeoff and good climb rate of about 1500 fpm until clearing the pattern. Engine cooling was excellent, and even with a fairly steep climb, the CHTs all stayed below 380 F—and only hit that for a minute or two before pitching over to a cruise configuration. The handling of the RV-4 is solid and predictable, and the visibility is out of this world, with your entire head and shoulders in the bubble. Locating and avoiding traffic in the pattern is a piece of cake.
I checked the stability in all three axes with the expected results. Yaw returned instantly to center with no overshoot—RVs at speed are very stable in yaw. Rolling into a 60 bank and then releasing the stick provided a steady, 60 bank, with no tendency to steepen or shallow. In pitch, the airplane was slow in the phugoid, but definitely stable—with only a pilot, the airplane was in the forward quarter of the CG range and tended towards stable and a little heavy on the elevators. The tandem RVs are known to get fairly light in pitch with a heavy back-seat passenger, so builders err on the side of nose-heavy when solo to prevent surprises when two-up.
Next on the test card were stalls, and as Murdock said, they were pretty much Cessna-like. Although there wasn’t a lot of buffet, the stall was gentle and straight ahead—as soon as the nose dropped a few degrees, the wing was flying again. This particular -4 exhibited the gentlest of all stalls I have experienced in any of the RVs, and the nose never even dropped past the horizon with the power-off stall. The indicated airspeed at the break was 51 knots with the flaps up, and 47 with the flaps down.
Bringing the power back in, the next things on the test card were the commercial coordination maneuvers: chandelles and lazy eights. Both were simple, easier, and a blast with all of the power available. Moving on, it is almost impossible to make the eights “lazy” in an aerobatic RV—they tend more towards complete wingovers, and that is part of the fun. Keeping coordinated took a little more footwork than some of the other RVs, which tend towards naturally coordinating themselves. But there is nothing wrong with keeping a pilot on his toes to keep the ball between the lines, and the RV-4 is at least honest about it.
After these warm-ups, I proceeded to do some gentleman’s aerobatics: loops, rolls, and combinations thereof. Most of my RV aerobatic flying is done with constant-speed props—you can set the power level and leave the throttle alone, letting the governor prevent over-speeds as you head downhill. With the fixed-pitch Catto up front on the demonstration airplane, it took a little more attention than that—but not a lot. Aileron rolls, of course, were quick and, although not as light as in an RV-3, they weren’t as heavy as they are in the bigger -8. This airplane aileron-rolled faster to the right than to the left, coming all the way around in about a three-count (roughly three seconds) or maybe a little more. Flying at an altitude of 9,000 feet with the thinner air, I thought this was just fine. I started a loop from level flight and drew a nice round figure (no one was watching, so that’s what I am claiming) with no buffets of impending stalls in the thin air. This is a great sportsman aerobatic machine overall—not as nimble as many, but very forgiving to those learning the craft. Pulling up into a parabolic arc entry, then rolling over on the back to go over the top inverted, the mountain landscape of the Carson Valley spread out in the big bubble. I enjoy the fact that such airplanes exist to give us the complete freedom of the skies. As with all slick RVs, care must be taken on the down lines not to build up too much speed, and aerobatic instruction is recommended for those transitioning from airplanes with more drag.
The well-mannered RV-4 maintains its reputation in the airport pattern. It is easy to spot traffic and to slow down (with a little planning); and hitting low key, opposite the numbers, just as you touch the top of the white arc is not difficult. I dropped the flaps all the way at that point, idled the engine, and played the turns to base and final to touchdown right on the numbers in a nice three-point attitude—no effort. This airplane really makes a taildragger pilot look good! It is often said that the RVs are the pussycats of the conventional gear world, and aside from the difficulty I have in repeatedly getting good landings in the -6, I can’t complain about any of them. The flare comes naturally, and whether you end up in a tail-low wheelie or a three-pointer, so long as you don’t force the airplane to do something it doesn’t want to do, it will all turn out all right. Directional control is hardly exciting at all—the airplane goes where it is pointed.
I made the first landing a touch-and go, retracting flaps and adding power as I slowed down past 40 knots. Before I could get all the throttle back in, I was up and away for another go. The next time around the pattern was a low pass for some photography, and the airplane is well behaved at speed above the runway. Pulling up into a final turn around the patch, I set up for a steep descent and a three-point landing. I touched down under good control, then had to add power because I had a long way to go to get to the next taxiway turnoff. As many have discovered over the years, with good speed control on the part of the pilot, these are great short-field airplanes.
All in all, I place the RV-4 squarely in the middle of the spectrum between the RV-3 and the RV-8 (the two other centerline-seating RVs). All three are remarkable airplanes, guaranteed to delight any pilot looking for a quality flying experience. The RV-4 is more maneuverable than the -8, less so than the -3, but if you want to have the option of taking someone along on a breakfast run, the -3 is out of the picture. For average local flying, solo or two-up, it would be hard to beat the qualities of the RV-4.
Buying a used RV-4
Because the RV-4 has been out in the world for 35 years, there are many available for resale. A large number of the original builders have reached the age where they are no longer flying, and many fine examples of the model can be found for sale at any given time. As we all know, there are people who like to build, people who like to fly, and a few that like both equally well—but for those who would rather fly than build (especially a non-pre-punched kit), the availability of used RV-4s is wonderful news.
As with any aircraft purchase, careful attention must be paid to a pre-purchase inspection. Because these are Experimental and hand built, no two airplanes are alike, and details often vary considerably. As always, careful attention should be paid to overall workmanship. The first thing to check would be shop rivet heads—are they properly formed and uniform throughout the airframe? Rivet heads tell you a lot about the skill and attention to detail of the builder. Because so many of the airframe parts have to be fabricated from raw stock, take a look at skin lines—are they straight and do they nicely match their neighbors (if butt-jointed)? How about aluminum angle stock that is shaped into brackets and longerons—are the ends nicely trimmed and free from tool marks? Do the fiberglass fairings and tips look nicely matched and finished (many of the early parts took a lot of work on the part of the builder to get right)?
Open the canopy and look at the raw edge of the Plexiglas (behind the skirt)—is it nicely polished, or are there tool marks and/or scratches? Does the skirt fit tightly when closed? Most -4s use aluminum skirts per the original design; many later ones are using fiberglass parts created by the builder because the aluminum ones can be hard to fit. If an aluminum skirt fits well, you have a fine example of the builder’s art. How about the empennage fairing—does it fit nice and even to both the vertical and horizontal stabilizers? What about the lower rudder fairings—these are all quick places to check on a builder’s attention to detail.
It is a good idea to look at several examples of RV-4s to get an idea of what is built to plans and what might be created by an individual. In any case, investing in a set of preview plans from Van’s is not expensive, and if you show up at a pre-purchase with your own set, well-studied, it will let a buyer know you have done your homework.
Inspecting systems installation is the same on an RV-4 as it is on just about any other airplane. Look for well-made hoses, a lack of significant leaks, well-restrained wiring and plumbing—everything that makes the firewall-forward area neat and tidy. Probably a majority of RV-4s have simple systems that are easy to inspect. Some later models, or those that have been upgraded, might take a little more time and care to make sure that everything works and is shipshape. Lots of -4s have add-ons like smoke systems; check for leaks, function—and take a careful look at the weight and balance. As with any homebuilt, be sure to get the builder to explain the systems—wiring and plumbing—in detail. Many people take the creativity allowed in Experimental aviation quite literally and do things differently in a break from tradition. A dark and stormy night is no time to discover that fuel doesn’t flow the way you thought it would.
What should you look for on RV-4s in particular? Many early models developed wrinkles in the lower corners of the firewall, mostly from hard landings; this is a place you want to look carefully. Take a look at the tailwheel and see if it is the original, or has it been upgraded to a modern steerable/swiveling model. Take a good look at the aft fuselage skins to make sure that hard landings on the tail haven’t bent anything—subtle wrinkles or bulges will tell you if the lower fuselage has been tweaked sideways.
As with any used aluminum airplane, look for wear at cowl and fairing attach points—fiberglass can wear holes in aluminum over time, and it is good to look for this. Take the wheelpants off and check the brake lines—early models used plastic tubing, later ones used aluminum. Either one can develop wear spots that could lead to a loss of brakes if they let go under pressure. Early model RVs frequently used sloshing compound to seal the fuel tanks—this has been found to flake off after a number of years, causing debris that can block fuel pickups and lead to fuel starvation. Look into the tank fillers with a flashlight and see if there is evidence of slosh—removing it is a doable, but painful process, and needs to be taken into consideration when buying an older ship.
Overall, a used RV-4, built to reasonable standards, is a great investment in a fun and useful aircraft. Most are built well, and the ones that aren’t are not hard to spot when you get up close. Used RV-4s are frequently advertised on the web site www.Vansairforce.net, in Trade-a-Plane, or on www.Barnstormers.com.
I’m fortunate to have flown every single model of flying RV (except for the -5, a one-off swing-wing prototype that was never produced), and each has its distinct advantages and characteristics. There are many who consider the RV-4 to be the nicest handling of the line. It is hard to disagree that, overall, it is an extremely well-balanced airplane—and without a doubt, the lightest handling two-seater of the line. Actual handling characteristics of individual aircraft do vary because of the way they are built, how much they weigh, and where the center of gravity is located for a particular flight. In addition, the shape of the aileron trailing edge has a great deal to do with the roll handling qualities, no matter which of the folded-trailing-edge RVs you look at. I have flown a much heavier RV-8 with somewhat convex ailerons whose roll feel was the lightest of any RV I have tried—and I have flown numerous RVs with more tightly squeezed ailerons that were almost heavy (compared to other RVs).
This makes comparing models more difficult, unless you have flown a number of each type. The RV-4 flown for this particular report is an excellent example of a carefully-built airplane, done according to plans by a meticulous machinist who likes to make parts match the drawings—exactly. The ailerons and elevator trailing edges are as close to spec as you can get, and therefore, this plane should be about what you’d expect if flying the original. The result is a very nice flying machine, lighter on the controls than almost anything the average GA pilot is likely to have flown. I have to qualify that “almost” because there is always the RV-3.
The RV-3 was, of course, Van’s second design—the RV-1 being the place that he learned about what would work, and what wouldn’t, when producing a small sport plane. The original RV-3 wing was the wing that Van designed for the RV-1, transplanted onto a new monocoque aluminum fuselage (which added six inches of legroom for the pilot over the original Stits Playboy design). The net result was an outstanding plane with delightful handling qualities. Because of the small size, the moments of inertia are small, so roll and pitch rates are quick, while the airplane remains stable. The RV-4, built to carry two, required larger everything—more wing, more tail, and a longer fuselage. As described by Van (see page 14), he spent a lot of time getting the dimensions right in “scaling up the -3,” with the result being an entirely new airplane that happens to look like its smaller brother.
In terms of flying, the RV-3 will spoil a pilot for anything else. Even though our own RV-3 is a “heavy” example of the marque, it is light and responsive in a way that no two-seater can ever quite match. The time it takes to do a 360 aileron roll in the -4 is probably one and a half times what the same maneuver will take in a -3—but compared to most general aviation airplanes, they both are extremely quick. Equipped with the same engines, the RV-3 will outperform the -4 as you would expect; a lighter airplane on the same horsepower will climb quicker and run faster. However, the RV-3 was originally designed for an O-290 engine, and with the 160 hp O-320, it will outrun its design redline at sea level. The Vne is defined by the flutter limit (among other things), so it is not something to ignore lightly. The RV-4, with its balanced tail, is more forgiving when it comes to red lines, which are also a little higher.
The RV-4 tested for this report is fast—and with its Catto prop pitched slightly for speed, it takes a little effort (and fuel) to catch. Our RV-3, with the constant-speed WhirlWind three-blade propeller can enjoy good climb and great speed—but at a significant outlay of cash. While there is no doubt that a constant-speed prop makes aerobatics easier (you can set the throttle and forget it), if going to breakfasts with friends is more your mission, a good, light, fixed-pitch prop will be just fine.
Cockpit comfort is largely defined by how the builder has customized the interior, but the RV-3 feels a little more cocoon-like than the RV-4, which feels more like you are sitting in a seat. Again the -4 is just fine—but you wear an RV-3.
The choice between an RV-3 and an RV-4 is going to be largely decided by your need (or desire) for a passenger seat. Building a single-seat aircraft is a selfish act, almost by definition. Spouses must be understanding, and be kept happy, for us to keep enjoying our passion for flight. For this reason, a lot more RV-4 kits have been sold and built than RV-3s over the years. And the truth is, an RV-4 is not much of a compromise—it is a wonderful airplane. If, of course, you already own a passenger carrier (be it a side-by-side or tandem), and you are looking for that second airplane, the RV-3 might well be the choice—but it is nice to share the thrill of RV flight with that RV-4 backseat.
—P.D.
Van Remembers-Designing the RV-4
When writing about a design that has been around for 35 years, it never hurts to go back and talk to the original designer to find out where the airplane came from and what he or she thinks about its evolution. We had the chance to catch up with Richard VanGrunsven—the “Van” in Van’s Aircraft—and ask him some questions about his first two-seat design.
The RV-4 kit as packaged 35 years ago is substantially the same as today. Everything for an airframe is there. (Photo: Van’s Aircraft)
KP: Describe how you designed the RV-4; was it simply a matter of stretching the -3 or a clean sheet?
I knew that I wanted to replicate the RV-3’s performance and handling as closely as possible, so the general lines were adhered to. But it was not a simple matter of scaling up a certain percentage. A wing area was chosen to provide a wing loading reasonably close to that of the RV-3. An estimated gross weight was the target from which these other parameters were derived. The cabin design was a key issue. I made a wooden cabin mockup and spent a lot of time sitting in it. I really worked hard to get the maximum comfort in a compact space. From the beginning I wanted to solo from the front seat, but did not know if the handling qualities (CG) would be acceptable, considering the considerable shift with or without a rear seat occupant and baggage. I ballasted my RV-3 to a very forward CG to simulate the solo condition of the RV-4. It worked OK, so then I designed the RV-4 with a greater horizontal tail volume coefficient to provide more pitch authority to accommodate the wider anticipated CG range. (Almost all tandem homebuilts at that time, mostly biplanes, used rear seat solo).
KP: How do you personally rate the RV-4 in terms of your other designs?
The RV-4 probably brought about greater changes to Van’s Aircraft infrastructure than any subsequent design. This is because the level of sales required more incremental growth than the addition of any later designs. While the RV-6 eventually outsold the RV-4, its introduction was not as game changing. The RV-4 exceeded our conservative performance estimates, but most subsequent designs have also. It is my opinion that the RV-4’s handling qualities are a bit better than our other two seat designs. But, this is a fine-line differentiation and is easily outweighed by the more utilitarian qualities of the others.
Van’s prototype RV-4, now on display in the EAA Museum, is outwardly distinquished by its two-piece canopy (front hinged to the side, rear sliding), which was discarded in favor of a single-piece, side-hinged canopy. (Photo: Van’s Aircraft)
KP: What do you like best about the RV-4?
Probably the handling qualities and the appearance, in that order.
KP: The RV-4 is still advertised and in your inventory; are people still buying new tail kits? How many?
Yes—but there were only eight RV-4 kit starts in 2013.
KP: What do you feel is the ideal engine for the RV-4?
It’s always debatable, but I’ll stick with the 160-hp Lycoming O-320. To my tastes, it seems to offer the right balance. However, the 180-hp O-360 is also a good fit.
KP: Short gear legs or long gear legs—what is your preference? Why?
The long gear legs provide better ground clearance for the prop. Initially, I based the prop clearance on the 68-inch diameter wood props, which seemed pretty ideal. When builders began using constant-speed props, their 72-inch diameter reduced the ground clearance uncomfortably. Also, the longer gear provides a higher ground angle of attack, which reduces the impact of tailwheel first contact on 3-point landings. Before developing the longer gear legs, I set the prototype up on wheel blocks to simulate the higher ground angle and the reduced over-the-nose view. It was still very good, so this was not seen as a limitation. Had I known in the beginning what I later learned, the longer gear legs would have been standard from the outset.
KP: Is today’s kit updated significantly from the original? How many changes would you say have been incorporated since the first kits were sold? What would you say are the most significant updates to the design over the years?
There have been hundreds of small changes made. Some were just to correct errors and others were improvements made as we gained experience. One of the most significant was the introduction of the pre-built wingspars. Though this did not involve a design change and is not externally visible, it nevertheless made a difference in ease of building and quality assurance. Most builders today can’t conceive of assembling their own spars, but that’s how it was at the time of the RV-4’s introduction.
During the early RV-4 years, the engine cowl evolved through several iterations. Mostly these were to increase the internal volume (engine and exhaust system clearances), and to accommodate constant-speed props. The evolution of carb induction boxes, resulting in the current “banjo box” filtered air box, also required cowl configuration changes. Along with the longer landing gear legs already mentioned, most of the other changes have occurred forward of the firewall.
KP: When and how did you come to realize that there was a demand for a two-seat tandem design as a follow-on to the RV-3?
Almost before the plans and kits were introduced, people began asking for a two place. I was hesitant to consider a two-place aircraft because of my perception that two-seat planes inherently lacked the performance and maneuverability of a single-seat like the RV-3. When I realized that there was a greater market for a two-seat plane, whether or not it approximated RV-3 qualities, it then became a “tandem vs. side-by-side” decision. My preference, from the aesthetic, performance, and sport perspective, was the tandem. My informal market survey seemed to indicate a slight preference for tandem.
KP: Do you see any reason why you wouldn’t continue to support new RV-4 sales in the future?
No, at least not in the immediate future. However, there are considerations that may affect the longer term.
KP: Any chance that you would choose to update the RV-4 kit to match-hole technology?
That’s not very likely. Designing parts for matched-hole capability is an enormous task. Preparing construction drawings comparable to those of our later designs is also a long and expensive process. There is not enough potential sales volume to offset these costs. When we developed the RV-8, we assumed that the RV-4 would soon be phased out because we thought that sales would essentially stop. That was almost 18 years ago, and the RV-4 is still in production. The RV-8 is a better airplane in many ways. Cockpit space is considerably larger, field of view is better, engine compartment space is greater, larger engines can be used, etc. Plus, the RV-8 kit and plans are superior. Our experience showed that a comparably powered RV-8 is only 3 mph slower than an RV-4. In the real world, this is an insignificant difference.
Another consideration we are increasingly becoming aware of is the challenge of supporting a diverse product line. Volume is necessary for efficiency and cost containment. At some point we need to realize that we can’t offer everything to everyone. Upgrading the RV-4 kit to RV-8 levels (or better) just doesn’t pencil out.
—P.D.
RV-4: A Recent Build
The first Experimental I ever saw was an RV-4 being built in a barn in Iowa. Having grown up building RC models, I intuitively knew this was the next step for me. I began reading KITPLANES, and while I ordered the info pack for the Starduster and a few other Experimentals, when that beautiful yellow RV-8 came to Oshkosh in 1995, I knew that was the plane for me.
Comparison of identical RV-4 flap horns built by two different builders. This doubler is fabricated entirely of aluminum angle and sheet. Note poor shop heads, wandering rivet line, edge distance violation, non-flush edges and lack of radiusing on Part B, as well as incorrect material thickness on lower stiffener. From a purely structural point of view, the horn on the right might be acceptable, but it looks terrible. Be honest with yourself when considering building a -4 and ask if the things you’ve built in your life look more like A or B. If B, you might want to reconsider a -4.
So, how did I end up with an RV-4?
After much soul searching, I realized that the -4 met my three goals of skill-set building, performance, and economy better than the -8. My primary goal was to use homebuilding as an “apprenticeship” to subsequently designing and building my own plane. The -4 requires quite a bit more fabrication than the later -8 (a plus for me since I wanted fabbing experience), and the RV series is held in high regard for the quality of its engineering—conservative, safe design, which yields high performance. In other words, I wanted to learn from the best. As far as the factory is aware (and they do keep close tabs on the safety record of each model), there has never been a -4 with a catastrophic structural failure when properly built and operated within its design limits.
RV-4 control horn closeup. RV-4 instructions call for casting the lead in place at the control horn. This is typical of the RV-4 emphasis on fabrication vs. assembly. Later series RVs have bolt-in preformed weights.
Performance-wise, the -4 is consistently rated as the sportiest and best handling two-place RV by those who have flown all types, and it will give you climb and cruise numbers with a fixed-pitch prop close to what other RVs achieve with a constant-speed. For the money, it’s pretty hard to beat a -4 (unless you downsize to a -3!).
Finally, -4s tend to be significantly less expensive to build than later series RVs. Much of this is obviously up to the builder’s own budgeting, but the smaller cockpit, smaller panel, and limited baggage space mean that there is simply less opportunity to drop big bucks on multi-panel glass displays, plush interiors, and a constant-speed prop with inverted oil or other goodies. Not that you can’t, but -4s tend to induce a more economical build.
Strapping the RV-4 turtledeck for match-drilling to bulkheads. Good RV-4 construction requires equal amounts of patience, precision, and creative-problem solving. You’ll also probably invest more in shop tools compared to other models (not necessarily a bad thing!).
There was, of course, a flip-side to the above parameters. The -4 turned out to be an apprenticeship indeed: while the factory web site lists a build time of 2000-2200 hours, I spent 3600 hours to get N986BP “Banana Puddin” in the air, followed by another 400 hours on details like upholstery and paint. And that doesn’t include the approximately 800 hours I spent online researching building techniques, problem solving, and procuring parts. Based on reports from other builders who have kept detailed and accurate build logs, my build time was not atypical.
The RV-4 canopy skirt is formed from aluminum, as compared to fiberglass for later series RVs. The skirt, wingroot fairings, and other parts will test your metalworking skills.
I also had the luxury to work on this project full time in a large, well-outfitted shop. For builders who have jobs and families, and are working in less than ideal spaces like garages, it’s no wonder that many -4 builders lose motivation long before the project sees the light of day. For an experienced builder, build time could be significantly cut, but I personally doubt that even with one -4 under my belt, I could get another in the air in the factory-listed 2000 hours. Give this serious consideration when ordering a kit.
Fairings can take quite a bit of rework for a flush fit. This is not uncommon for RVs, so developing good fiberglass skills is important.
Part of the build time issue with the -4 (and even more so for the -3) is that the -4 involves much more fabrication as compared to later CNC pre-punched kits which are more assembly-oriented. There is no quickbuild kit, and the only pre-punched parts are the wingskins. While there is certainly a feeling of pride and accomplishment that comes with this kind of labor-intensive craftsmanship, I’m thoroughly in favor of using technology to make building airplanes as simple as possible. If you’ve had any exposure to the later kits, there are times when fabricating -4 items seems needlessly old school.
As regards the performance of the -4, the single biggest drawback is cockpit size. I am 6 feet 2 and had to do a “tall-man conversion” in order to fit in the cockpit; I still find the limited room uncomfortable on cross-country flights (as aficionados would say, “You wear the -4”). Rear seat room is even more cramped, and if you want to install rudder pedals or engine controls to the back, you will be on your own (as compared to the -8 which includes drawings for both). You will also run out of rearward CG sooner than in the heavier (and typically nose-heavy) RV-8; this affects the amount of baggage you can carry and dual aerobatics.
There’s no quickbuild option for RV-4s, so all builders get to enjoy the thrill of working with Pro-Seal when constructing the fuel tanks.
Finally, on the issue of economy, the -4 resale market is relatively small, and it’s more of a buyer’s market compared to the other models. I’ve been tracking RV prices for about 15 years, and while you can probably expect to recoup what you have in the plane should you someday need to sell it (assuming proficient craftsmanship), you’d be lucky to get much more than that, and could potentially get much less if there are issues with the build (as there often are on older models that predate the Internet when builders were more or less on their own).
Kits are relatively complete and parts quality is generally excellent, with the occasionally inexplicably cheap hardware (i.e., plastic brake lines, industrial tailwheel). Factory support is good, but is officially only for two hours in the morning and one hour in the afternoon Monday through Friday, which can be frustrating for those who build in the evenings and on weekends. Thankfully there is Doug Reeves’ Van’s Air Force builders’ forum, and questions posted there are often answered within minutes by experienced builders.
Spar carrythrough bulkhead. These bulkheads, along with the spar splice plates, are match-drilled with the spars at the factory, so it’s essential to make sure these are part of the package if you buy a used wing kit.
Parts fit is not really an issue—not because it’s so good, but rather because so much of the plane is hand crafted and it’s the builder who makes things fit. Fiberglass parts fit ranged from excellent (wingtip fairings and wheelpants) to mediocre (cowl and empennage fairing). There is unfortunately no quickbuild kit.
In my mind, the biggest problem with the -4 kit is the plans and builder’s manual, which are mostly accurate but occasionally incomplete, baffling, or even incorrect. It seems like updating the plans would be a small matter, but with the factory only selling a few kits each year, there is, understandably, little impetus to do so. The instructions remind me of my attempts when young to write a diary. The beginning is quite thorough (drill this hole, measure that, set first rivet here), but by the end you feel as though the young Dick VanGrunsven has had enough of this literary business and has moved on to something more interesting, such as Chapter 18—”Installing the Engine,” or Chapter 19—”Go Fly.”
As I built my -4, I traced the analogous build process of the RV-8 via the -8 preview plans set (both drawings and manual). This allowed me to get a sense of how RVs have evolved, both in actual design as well as presentation of plans. If you enjoy mental puzzlers, the -4 has them aplenty. Regardless of which kit you build, taking a few months to read the instructions and study the plans in advance is time very well spent.
As with many kit aircraft, the completion ratio of -4s by the initial buyer/builder is low. This can work in your favor: my wing and tail came from a barn in Wisconsin, and my fuselage from a hangar in Oregon (the finishing kit came from Van’s). This saved about $4000. Due to the large number of RV builders, new/like-new parts, avionics, and tools are available on Vans Air Force.net or Barnstormers.com and can help reduce the investment for the motivated scrounger.
Inevitably, the questions come up of would you do it again (absolutely), and what would you change the second time around. Knowing what I know now, if the RV-10 hadn’t driven up prices for IO-540s, I’d be sorely tempted to build a Rocket. I also like the look of the fastback, but heeded the advice of another builder who said, “If you trick out everything on the plane, you’ll never finish.” The issue of constant-speed versus fixed-pitch propellers is endlessly debated on the online forums, but on an airplane like the -4, which has such a huge ratio of stall-speed (54 mph) to top-speed (200 mph+), I think the ever-present temptation to install bigger powerplants has a low return on investment unless paired with a constant-speed prop. On the other hand, I’m quite pleased with my 7-inch SkyView EFIS and Vertical Power VP-X electrical system and will definitely use both in my next plane.
—Eric Stewart
