All Awhirl: Rotary Engines Still Soaring High

It’s the stuff of legend: goggles, leathercaps, and fluttering white scarves, brightly-colored canvas-and-wood aircraft clashing in battle, just barely past the fledgling stage of human flight. 

The aircraft and pilots of World War I and the surrounding pioneering era hold a fascination for many, yet a select group of pilots and mechanics stand out with the unique skills and dedication to historical detail necessary to fly and maintain aircraft—powered by original rotary engines—from this era. 

At one of the core hubs of this global community—Old Rhinebeck Aerodrome (NY94) in Red Hook, New York—director of maintenance Mark Mondello gives tours to visitors when he’s not flying or wrench turning on one of the museum’s myriad vintage aircraft. 

All total between flying, static display, and spares, there are 16 rotary engines at the museum attached to some of the most famous aircraft of WWI—Sopwith, Fokker, Nieuport, Caudron, Morane-Saulnier, Avro, and many more. Mondello has his hands full keeping everything running smoothly. He enjoys explaining the significance and function of these unique engines to new visitors in a colorful way—and enjoys flying them even more.

 “The whole engine spins,” he said. “Imagine if in your car, your engine was directly connected to your wheels and spun around crazy fast, like your wheels do all the time.” 

It gets your attention. 

Higher, Farther, Faster 

A rotary engine is a four-cycle combustion powerplant, but here is where the similarities to anything else abruptly end. 

Since the entire engine is spinning around the crankshaft, all the cylinders have to weigh exactly the same to be balanced, and the fuel must be supplied through the hollow crank- shaft. Instead of spark plug wires that would become tangled up, there’s a single collector disk.

There’s no way to circulate oil through such a spinning engine, so it is a total-loss system. Castor oil—a thick, incredibly sticky form of vegetable oil derived from castor beans—is flung out through the exhaust valve at the end of each cylinder, so the oil tank needs to be refilled after every flight. 

At a time when radial engines had not yet been developed, an engine that could be air cooled meant ditching the heavy, nonaerodynamic radiators and associated water. It marked a leap ahead in the rapid advancement of wartime technology, chasing improvement in power-to- weight ratio when the smallest edge in horsepower, speed, and altitude could mean victory on the battlefield. 

The French-designed Le Rhône rotary engine, weighing 250 pounds, could produce the same horsepower as 450-pound, water-cooled engines of the time—and was much easier to maintain. In addition, the lack of oil circulation meant it didn’t have to warm up like in-line, liquid-cooled engines did, allowing for quicker scrambling after start-up. 

The design was revolutionary. Many of the greatest WWI aircraft and aces were carried by rotary engines. But technology continued to advance so rapidly that by the end of the war in 1918 the rotary was made obsolete as the radial engine was perfected and began to take its place. 

Yet this flash-in-the-pan moment represents a crucial time in aviation technology and brought us some of the most iconic warbirds. For Mondello, it’s more than just a type of engine. It’s a museum within a museum and a living piece of aviation history that’s a thrill—and challenge—to experience. 

After personally flying around 10 types of World War I aircraft, the ones Mondello cites as most exciting and handling “like a fighter” are two rotary-powered legends—the German Fokker Dr.I triplane and the British Sopwith Camel. 

He describes flying the Camel “like having a tiger by the tail,” and it’s not hard to see why. With a wingspan of 28 feet, it weighs only 900 pounds empty, 300 pounds of which are the 160 hp Gnome rotary engine whirling along with its massive 9-foot propeller. It’s nimble and very unstable, with an enormous amount of thrust.

“It really surprises you,” Mondello said. “You feel like you just point the nose totally skyward, and it just goes.” 

The combination of higher horsepower and comparatively heavy engine makes the Camel the only rotary-powered aircraft he has flown where the gyroscopic precession is really noticeable. Add that to the Camel’s undersized rudder and some “weird” handling characteristics, and the airplane “can really screw you up if you’re not on top of it,” Mondello said. 

The necessity of on-point rudder usage and continuous close management of a 100-plus-year-old engine makes for a demanding airplane. Mondello explained that when flying airplanes from the 1920s onward, about 80-90 percent of the pilot’s brain power is concentrating on the actual flying, while perhaps 10-20 percent is focusing on the management of the engine and systems. 

But when flying a rotary, he said you’ll need at least half of your brain power and attention to just manage the engine and keep it running. 

“I’m amazed by the young people who were fighting in these things in World War I,” Mondello said. “Then on top of that, someone is trying to kill you, and you’re trying to kill them too. So that’s really incredible to me.” 

It’s a sensory overload, and heightened attentiveness to things like sense of balance and the airflow over your face, listening to engine rpm and tone—“fizzy soda” is good, “bubbling coffee” is bad, according to Mondello—are crucial. So is using sight to identify the right color 

exhaust smoke and smell to determine if the Castor oil is burning as it should. 

“When I land a rotary engine, I smell like a McDonald’s that burned down,” Mondello said with a laugh. Despite the mental and physical workload, he said it’s a rewarding enterprise. 

“It’s very engaging to the entire body, to all of your senses,” he said. “And that’s one of the things that makes it so much fun because it’s a full experience of flight. You’re as close to one with the airplane as you could ever be. Also, very few pilots can say they’ve flown behind a rotary engine, so hey, I feel a little special!” 

Aviation Archeology 

The delight of interacting with this extraordinary and historical piece of machinery is infectious and quickly apparent among anyone in its proximity. 

Michael Damiani, a pilot and A&P/IA who flies and maintains vintage aircraft at the Golden Age Air Museum in Pennsylvania, shares the intrigue during his personal time working on a Fokker Dr.I triplane, owned and flown by museum president Paul Dougherty, with an 80 hp Le Rhône rotary engine. 

It’s a popular attraction for visitors during events, and in 2022 the museum organized the Fokker Scourge fly-in, open to public attendance, where four rotary-powered Fokker triplanes were displayed and flew—the largest known gathering since World War I.

Damiani recalled how it was a challenge to get the engine running initially. He said it took some creative brainstorming and thinking outside of the box to troubleshoot—something that’s part of the fun for both he and Mondello. 

From a mechanical perspective, they attribute a large portion of the fascination surrounding rotary engines to a sort of “aviation archeology.” A lack of complete documentation over 100 years means nothing is neatly laid out in a maintenance manual with every step written down. 

Modern mechanics have the task of trying to reverse engineer things, getting into the mindset of a mechanic from 1914-18 to infer what their experiences were, what tools they were 

familiar with, and what methods they would have used—filling in the gaps in the historical record. This is one of the reasons the community is so tight-knit and supportive in sharing knowledge. It takes a village to keep each of these engines in the air. 

It’s a system that is working smoothly, thanks to the dedication of each individual involved. “It’s extremely reliable and runs great,” Damiani said of his triplane’s engine. “I’m impressed by its reliability and simplicity.” 

Although these engines and their parts are rare, they do exist and are carefully curated by the community when found. A good portion in the United States were built by the Union 

Switch & Signal Co. in Pennsylvania, which produced switches and signals for railroads before receiving a contract during the war to build the Le Rhône engine. 

In the end, most of these engines never made it overseas before the end of the war. But some of them are still turning up, sprouting aspirations among more pilots already enveloped in vintage aviation circles. 

‘It’s Visceral’ 

One new pilot inductee in the rotary-engine fraternity is John Elliott, a Virginia resident and accountant by trade who has been “airplane crazy since being a little kid.” 

After getting his pilot certificate in 2008, Elliott immediately launched into ownership of a string of vintage aircraft. The goal was always to own and fly a WWI fighter, particularly one with an original rotary engine.

“It’s just fascinating,” Elliott said. “The idea of flying these fragile aircraft at 15,000 feet, wood and fabric and a wicker seat, shooting each other with guns, just seemed crazy to me. It had been a dream of mine to have one of those aircraft, but I thought it would be sort of an impossible dream.” 

The intimidating stories of the gyroscopic effects did not deter him but only made him “absolutely convinced” of his goal, determined to build his skill to be able to safely handle the challenges that came with a nimble fighter equipped with such an engine. 

In 2021, he bought a Fokker Dr.I triplane replica with a Lycoming radial engine and flew it for a few years, getting used to the unique handling characteristics and integrating into the WWI aircraft community. 

When one day he heard about an original 1918 80 hp Le Rhône for sale, he dropped everything to go and buy it. Thus began a firewall-forward conversion that turned out to be “a lot more work than it seemed.” 

With a new laminated wooden propeller made by community leader Fred Murrin, a mix of original and replica WWI instruments, replica guns, and a new paint job in one of the “Red Baron” schemes of famous WWI ace Manfred von Richthofen, the airplane is a historically-accurate work of art. The first flight test was the experience of a lifetime, according to Elliott. 

“It was just a spectacular experience for this journey, which has 

been like a 50-year journey since I was a little kid,” he said. “Dreaming about doing this, drawing pictures of triplanes [then] to actually then go and execute on that dream.” 

In harmony with Mondello’s description, the gyroscopic effects were not as big of a monster to deal with for Elliott as expected, especially with the lower horsepower. Elliott said a good tailwheel pilot will automatically compensate for most of it, and the only significant difference that feels counterintuitive at first is the need for left rudder in both turns. 

“When you roll into a hard right turn, it likes to turn right, and the nose tends to tuck down,” he said. “So sometimes if you turn too tight, you might need to use left rudder to bring that nose up a little bit. It’s a little slower to roll in the left turn, because it doesn’t like to go left as much, and again you’re stomping on left rudder to get the nose down, because the nose will try and pitch upward. It climbs great, maneuvers great…I tell everybody it’s like standing on a ball. You got to fly it all the time. You got to be on all three axes.” 

Elliott said he loves the experience of operating a machine that is a true organism—where the pilot is the brain, an integral part of the engine and airframe. 

“It’s visceral,” Elliott said. “It penetrates, and you’re using all of your senses at the same time. So from that aspect, it’s addictive, right? So I think that’s the part that the folks that have it are like, ‘Wow, yeah, I want to do this more.’ I can’t wait to fly it again. It’s the wildest stick-and-rudder experience.” 

Still Going Strong 

The adventure of flying old, cantankerous engines on highly-demanding aircraft is not for everyone. But those who have taken on the challenge understand the unique risks and prepare as much as they can, always growing their knowledge and skills and supporting each other. 

Community is key, as it is impossible to operate these aircraft alone. 

“Someone has to flip the prop,” Elliott said. “You have to have somebody with a fire extinguisher, [and] you have to have somebody pull chocks, right? If you’re going to do this, then you’re going to need that kind of support.”

 Elliott expresses deep gratitude for the help and encouragement the community has provided from the beginning. And he’s eager to pass it along to the next newcomer. 

Damiani emphasized the enjoyment he gets out of his work with the museum every day. 

“It’s special, and people are interested in the airplanes,” he said, citing a family who had a rotary engine passed down for generations and donated it to the Golden Age Air Museum, which has plans to put it on a Nieuport 17, a French-built fighter. 

Damiani also highlighted a common theme among the community—that it’s as much about the 

history and people they represent as having an amazing flying experience. Keeping this bit of aviation heritage alive is a big task, one that he believes this ever-growing group of aviators is more than capable of carrying on.

 “There’s certainly still interest in it,” Mondello said. “[The public] like seeing the airplanes, and they like learning about them. There’s still stories to be told. There’s still reasons to display the airplanes and the engines.”