“Wing warping,” as this approach was called, was satisfactory for very slow airplanes, but faster ones required more rigidity, and by around 1908 or 1909 the idea had arisen of replacing part of the trailing edge of a wing with a hinged, controllable flap. Actually, a prescient Englishman, Matthew Boulton, had patented the idea in 1868, when airplanes were still a thought experiment. His invention had been forgotten, however, by the time real airplanes came into being. Despite the early invention of the aileron, wing warping continued to be used, even on some fighters, as late as 1916.

That a hinged trailing-edge flap would have the same effect as warping the entire wing is obvious to us, because we have seen it in action. But it cannot have been quite so obvious then. The evolution of airplanes in the United States suffered from the Wrights’ unfortunate attempt to establish a monopoly on flight by patenting the very concept of lateral control. Litigation over that ambitious claim held back aeronautical development in America for years while it raced ahead in Europe.

The function of an aileron, or any hinged trailing-edge surface, is commonly explained in ground school by simple analogy to, say, a door opened on a windy day. The wind hits the deflected surface of the aileron and pushes on it. If the aileron is deflected downward, the wind pushes it upward, and if it’s deflected upward, the wind pushes it downward.

This explanation, while intuitively appealing, fails to capture what is really happening. The majority of the lift generated by an unstalled airfoil is always concentrated near the front, and moving a trailing-edge flap up or down changes the flow conditions at the leading edge. An aileron deflected downward impedes air passing below the airfoil, and as a result, the dividing line between air passing below the airfoil and that passing above it moves aft. More air now passes over the top, the velocity of air rounding the leading edge increases, and the pressure there is correspondingly reduced. In other words, the lift change that results from deflecting the aileron is not confined to the aileron itself. It affects the entire area ahead of the aileron as well.

• READ MORE: Recalling a Good Pilot Friend and One Curious Character

The effect of the aileron, like that of wing warping, amounts to a change in angle of attack. This understanding helps clarify what is happening in a steady-state roll. Why does an airplane with deflected ailerons settle at a steady-roll rate rather than roll faster and faster? It’s because the rotation reduces the angle of attack of the up-going wing and increases that of the down-going one. The change, which is opposed to the change caused by aileron deflection, is not uniform. It is greatest at the tip, where the rotational velocity of the wing, relative to the forward velocity of the airplane, is greatest. When the change of angle of attack due to rotation, integrated across the entire wing, is equal in magnitude to that resulting from deflection of the ailerons, the airplane is in equilibrium about its roll axis and rate of roll stops increasing.

Rate of roll is one of the “wow” numbers associated with a high-performance airplane. When we read that a T-38 or an A-4 rolls 720 degrees per second, we are amazed and wonder how the pilot knows which way is up. Arguably, roll acceleration—how quickly you get from zero to, say, 90 degrees of bank—might be more important in air combat maneuvering.

Roll rate is not a single number, however, as it increases with speed. Preferring a criterion that is independent of speed, engineers often refer to “peebee-over-toovee”—a (more or less) constant value represented by the ratio “pb/2V,” where “p” is the rate of roll in radians per second (a radian is 57.3 degrees), “b” is the wingspan, and “V” is the true airspeed (in the same units as the wingspan). Thus, for example, an airplane with a roll rate of 70 degrees per second (deg/sec), a wingspan of 35 feet, and a forward speed of 300 feet per second has a pb/2V of 0.071 radian.

In physical terms, that means that if the airplane flew past you while rolling, the path of its wingtip, in profile, would be at an angle of 0.071 x 57.3, or about 4 degrees to the flight path. That is called the “helix angle,” because the rotating wingtips form a double helix, like DNA.

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The rolling helix angle is theoretically a constant for any given airplane, determined by wing planform, aileron design, and various other subtler factors. In principle it allows you to predict an airplane’s roll rate at any speed. Things don’t quite work out that way, however, because at high speed deflecting the ailerons makes the whole wing twist, counteracting the ailerons themselves, and cables stretch, preventing the ailerons from deflecting completely. Still, helix angle remains a convenient criterion, at the very least for setting a minimum acceptable standard for rolling performance.

A 1941 National Advisory Committee for Aeronautics report set that minimum value at 0.07 for transports and bombers and 0.09 for fighters. According to some published figures with which pilots who flew the airplanes are bound to disagree, the Spitfire Mk.V and FW-190 were fast-rolling airplanes, and the P-40 was not far behind. The FW-190 rolled 151 deg/sec at 226 knots, the Spitfire 150 at 176, and the P-40 134 at 315. The P-47 rolled a mere 71 deg/sec at 250 knots, the P-51B 98 at 260, the P-38 78 at 260. The corresponding pb/2V values are 0.118, 0.163, 0.082, 0.060, 0.072, and 0.084 respectively. The T-38 scores around 0.26.

Neither helix angle nor rolling acceleration fully expresses the quality of lateral control experienced by the pilot. That has more to do with effort, linearity of response, and presence or absence of “hysteresis,” or slop. Pilots used to single out the ailerons of Bellancas for praise, but pb/2V had nothing to do with it. It was really all about the ailerons’ smooth, frictionless, instantaneous response, low forces, and lack of free play.

The fact that pb/2V is theoretically constant for a given airplane has a couple of corollaries. One is that a larger span results in a lower roll rate. Another is that roll rate in degrees per second, taken alone, is misleading.

The Sopwith Camel, one of the deadliest fighters of World War I, rolled at a mere 40 degrees a second. But if you judged it by its pb/2V of 0.083, it was equal to the P-40 and superior to the P-47 and P-51.

This column first appeared in the March 2024/Issue 946 of FLYING’s print edition.

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The talents of One-G Simulation, the makers of FAA-approved flight training devices, and education technology company Cignatec have created two Sopwith Camel simulators as part of the Museum’s World War I exhibit.

The museum commissioned One-G to design and build the devices to give museum visitors an immersive flying experience through a range of user-activated scenarios.

About the Simulators

One-G produces FAA-approved professional grade aviation training devices. The company began in a Seattle-area garage when One-G CEO Xylon Saltzman, an engineer, flight instructor, and charter pilot was forced to travel to Arizona for type-specific recurrency training. He realized that there was a market for better access to equipment and the company was born. According to Saltzman, One-G received its first letter of authorization from the FAA in 2011. Today, One-G has approximately 100 devices in the flight training world ranging from primary training units that simulate round-dial and G1000 cockpits to the more advanced devices that are used for training by companies such as air ambulance providers that utilize TBM and PC-12s.

“As a longtime resident of Seattle, it has been a pleasure collaborating with the Museum of Flight, successfully bringing the experience of flying a Sopwith Camel into the hands of the general public,” said Saltzman.

• READ MORE: When the Nose of a Camel Starts to Wander

Cignatec is devoted to creating learning experiences through the application of technology. Josh Swanson, president of Cignatec, is enthusiastic about collaboration with One-G and the MOF. “As a long-time member of the Museum of Flight, and advocate for STEM education, supporting the museum with this project has been a privilege and a lot of fun — and of course, it’s always great to work with One-G.”

According to Drew Pine, chief simulation engineer for One-G, “We hadn’t done anything like this before. It was quite a departure from FAA projects that we mostly develop. We wanted to make it enjoyable for non-pilots.” To that end, the units have elevator and aileron control and auto-rudder. “It is more along the lines of an arcade educational device rather than a training device,” he said.

There are three scenarios: takeoff and landing practice, follow the leader (another Sopwith Camel), and flying through rings. The flights take place over rural Europe, circa 1917. The scenarios are selected by pressing a button, and last for approximately two minutes.

About the Sopwith Camel

The Sopwith Camel is an open-cockpit single-seat biplane from World War I. Introduced by the Sopwith Aviation Company in 1917, it became one of the best-known fighter aircraft of World War I. The airplane was also immortalized in the Peanuts comic strip as Snoopy, the cartoon Beagle with the rich imagination, pretended to be a WWI flying ace at the controls of a Sopwith Camel while sitting atop his doghouse.

About the Museum of Flight

The Museum of Flight is located at King County International Airport/Boeing Field (KBFI). The museum collection contains aviation artifacts that predate the Wright Brothers and extend through the space program. The MOF is one of the largest aviation museums in the country and has the added bonus that pilots can fly in to visit.

For more information visit https://www.museumofflight.

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Aside from a change in career trajectory, another change was owning a North American T-28, having previously owned an Aeronca L-16 when he first began flying and a North American T-6 years later. He loved flying the loud radial warbirds, but there were downsides to their power, Turner recalled. 

“I grew tired of $500 fuel fill ups in the T-28. It was amazingly high to fuel that aircraft. As a result, I started getting into World War I aircraft. I built a Sopwith Camel, with a more modern engine. I really enjoyed the people, the airplanes, and the history of First World War aviation, so I continued on with this hobby.”

The timing of his new interest conveniently coincided with a move that Turner would soon make across the country. “At the time, I was working as a civilian at Brooks Air Force Base in San Antonio, Texas, and they were moving the section I worked in up to Dayton, Ohio, to Wright-Patterson Air Force Base. I thought, ‘Well, this is the chance for me to do something really crazy,’” he said. “I found 11 acres of land and I decided that I was going to have a little First World War airfield.” 

He decided to call the airfield Aerodrome Les Noyers (50OH). With a 1,600-foot-long turf runway, its unique and memorable name was an ode to one of the Great War’s Triple Entente members. This is an homage that Turner has sought to highlight as much as possible throughout the property and its routinely held events.

“I wanted a French name. ‘Les Noyers’ is French for ‘the walnut grove,’ which is what borders the aerodrome—and is a common French town name. After buying the property, I built a wooden hangar, and also built a little French cottage. It almost feels like you are over in Europe. That was the whole goal. I told you I was crazy!” Turner laughed.

• READ MORE: Museum Spotlight: National Museum of the U.S. Air Force

“When you come down the property, there is a big, long row of trees, as well as a runway. There is also a 50-foot by 60-foot hangar, a base operations building decorated with period items—and I have a Nissen hut from Wales. This is kind of like a Quonset hut, and in here there is an officer’s club with a little bar, a potbelly stove, as well as tables and chairs. There, we have our little meetings and stuff.”

Another onsite building is useful for Turner’s and others’ ongoing aircraft build endeavors, he said. “I also have a heated building on the property, which is kind of a fabric and paint shop. After we got settled here, I sold the first Camel that I had built and am currently building another. Except, this one is much more historically accurate and has an original rotary engine in it. I’m also building a two-place Nieuport 12, so that we can give rides to people.” 

Looks only get you so far—the real appeal of Aerodrome Les Noyers is the action that takes place there. Its location in the Dayton area makes it popular within the WWI aviation interest circle, for a key reason. 

Turner said, “The National Museum of the United States Air Force is up near here and they have a World War I fly-in every other year. And we have a smaller, private fly-in here at my place. The event population has ranged anywhere from 75 to 150 participants, and they come from Canada, Europe, and all over. It’s a nice group of people, and we are all kind of amateur historians. During our events, we do formation flying in our World War I replica aircraft, safety instruction, and stuff like that. We keep it very simple and safe here during the fly-ins, but it’s really cool to see a bunch of World War I airplanes flying in formation. You just don’t see that very much.”

“We have one really cool thing that we will do during this time, where we will send up a guy in a Nieuport biplane. What he will do is make very slow, lazy circles over the airfield. Then for everyone else who flew in, we will put GoPros on their airplanes. After briefing, they will try to saddle up for a gunshot, so it’s like gun camera film—but with World War I airplanes. Once they land, we review the film together and vote on a ‘Top Gun’ film. It’s hysterical fun.” 

Having given a glimpse into his special aerodrome, Turner proudly summarized its importance. 

“We also support period aircraft builders and stuff like that at Les Noyers Aerodrome. So, it’s really just a nice World War I venue for people to fly their World War I airplanes into. I don’t know of any other airfields in the country that are like this one. I know there are some others that focus on the Golden Age of Aviation, that have some World War I airplanes. But I think Les Noyers Aerodrome is the only one of its kind. And, not to mention, we have the only currently flying rotary Sopwith Camel in the Western Hemisphere.” 

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