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Dec 02, 2023

Rebuilt to Last

A small group of enthusiasts keeps World War I airplanes aloft. A rising sun

A small group of enthusiasts keeps World War I airplanes aloft.

A rising sun casts long shadows across the damp, manicured grass at Grimes Airfield, a private airstrip between the razor-like ridges that frame the farms of southeastern Pennsylvania. Grimes is home to the Golden Age Air Museum, which has organized a weekend gathering of vintage aircraft for a September airshow. Arriving as the sun climbs above the ridges is John Gaertner, a master airplane craftsman who is passionate about early aviation.

Gaertner's thick hair and goatee are filled with gray. His ever-present glasses are secured by a thin, black neck strap. Ask Gaertner any aviation­­-related question. If he doesn't know the answer, he’ll freely admit it. But a typical response will be so detailed with names, dates, historical events, aerodynamics, thermodynamics, mechanics, materials science—and more—that one can see why his two brothers nicknamed him "Professor."

John Gaertner (a Fokker Dr.1 replica behind him) visits the Golden Age Air Museum's airshow. Two of the Dr.1s in attendance belong to his clients.

Scattered across the grassy expanse at Grimes is an assortment of aircraft that few people today have ever seen fly but were once common in the early days of aviation. The airplanes attracting the most attention are four Fokker Dr.1 triplane replicas parked wingtip to wingtip. The Dr.1 was made famous by World War I German fighter pilot and ace Manfred von Richthofen, better known as the Red Baron.

The triplanes are in Pennsylvania for an event that is billed as an airshow but happily feels more like an informal fly-in. Three of the Dr.1s arrived by trailer, towed in from across the eastern half of the United States. The fourth is based at the Golden Age Air Museum. Most importantly, three of the four aircraft employ a rarity in recreational aviation: original rotary engines, built more than 100 years ago. Two of the triplanes belong to Gaertner's clients, and he's here to see his work fly.

Inside his basement workshop, Gaertner creates a non-flying replica of a Curtiss JN's instrument panel. Using a vintage compass as a guide, Gaertner fabricated a new one.

Gaertner belongs to a very small group of aviation craftspeople scattered across the world who help keep vintage aircraft flying and historically accurate. For one triplane, Gaertner fabricated a windshield, ammo trays, and adjustable gun mounts. For another, he added historically accurate seatbelts. Its owner next wants Gaertner to overhaul a vintage engine.

Chris Hill's day job is flying corporate jets. After flying his replica Fokker Dr.1 in the airshow, he cleans castor oil from the tail.

The weekend event is billed as historic. When three of the Dr.1s are photographed flying in formation, they constitute the biggest aerial display of rotary-powered flight America has seen in 100 years. "There were plenty of them after World War I, but even the Army Air Service relegated rotary engines to the scrap bin of history because of their requirement for lots of maintenance," says Gaertner. According to him, original rotary engines capable of propelling an aircraft these days "would be limited to about one dozen."

Gaertner is walking among the triplanes when he is asked what drew him to this era of aviation. "I think because it's when the airplane became practical," he says. "It was flyable. You could fly it every day. They had enough duration that it wasn't just a lark." Gaertner pauses as a passing aircraft drowns conversation. As the aircraft pulls away, he adds: "I just like the way they are built."

Aviation has long been part of Gaertner's work life. At 17, he was an intern at the Smithsonian Institution's National Air and Space Museum in Washington, D.C., where he helped with historical research before becoming an exhibits specialist. He went on to be a curator at the EAA Aviation Museum in Oshkosh, Wisconsin. In 1999, he joined the aircrew of a restored Vickers Vimy as it flew from Munich to the Paris Air Show for the 80th anniversary of its trans-Atlantic flight. Gaertner built the control system for a 1901 Wright glider, created wings for a Falco 8L, and fabricated multiple wing sets for Curtiss JN "Jenny" biplanes. He's also rebuilt a Hispano-Suiza 4A to airworthiness and overhauled five Curtiss OX-5 engines.

For a celebration of the 100th anniversary of the British Royal Air Force at the National Air and Space Museum's Steven F. Udvar-Hazy Center in Chantilly, Virginia, Gaertner displayed parts he made for an Avro 504 he's restoring. Known for his fabrication skills, Gaertner builds cockpit instruments ranging from compasses to oil pressure gauges. His clients include internationally famous aircraft collections and individual aircraft owners across North America and overseas.

Chris Hill is a self-described World War I fanatic and one of Gaertner's clients. He's a former U.S. Air Force Boeing B-52 pilot who flies corporate jets when he's not flying his Piper Cub, Vans RV-8, or his black-and-white Fokker Dr.1 replica—one of the four Dr.1s that were at Grimes. Hill also owns the wreckage of two British World War I biplanes—Royal Aircraft Factory S.E.5 fighters—which he plans to meld into one flyable aircraft.

Hill confirms the Grimes fly-in is uncommon. "Three rotary-powered Fokker triplanes flying together hasn't happened since the end of World War I," says Hill. "Following the war, there were three documented original Dr.1s that existed. Two of them appeared in a German movie in the 1920s or 1930s. But by the end of World War II, they’d all either crashed or been destroyed by the war. So there are no remaining originals. You find pieces of originals but not enough to make an airplane."

Three Dr.1s make a low pass over Grimes Airfield. Each airplane is powered by an original rotary engine that is at least 100 years old.

According to Russ Lee, who leads the aeronautics department at the National Air and Space Museum, finding an original aircraft from the early days of aviation is difficult because they no longer exist—or they already belong to collectors. "Almost every airplane in the collection is original," he says. "We just want the original. That's our standard. We’ve been offered replicas and reproductions over the years, but in almost every case, we turned them down."

Ken Kellett, a restoration specialist at Fantasy of Flight, an aviation museum in Polk City, Florida, that has one of the world's premier private aircraft collections, explains why so few of the early wood-and-fabric aircraft have survived: "They continually rot into the ground."

All airplanes—even metal ones—will deteriorate just sitting in a hangar. Birds make nests in air intakes while rodents invade cockpits, where they chew on wires. Even snakes have been known to call airplanes home. At the same time, lubricants in moving parts dry out, fuel evaporates into a gummy substance within carburetors, water collects in gas tanks, plastics become brittle, aluminum corrodes, and dissimilar metals seize to each other. With prewar and World War I airplanes, the fabric frays and the wood decays.

Kellett has worked on dozens of wood-and-fabric aircraft, including World War I fighters. He's also one of the few people who built and flew his own 1903 Wright Flyer. He knows well the joy and agony of working with early aircraft. "The World War I restoration that I do is at [film director] Peter Jackson's level of detail," says Kellett. "The instruments, seatbelts, wheels, and everything. If you need a gas tank that's all soldered and done the way it's supposed to be, the guys you’re gonna let do that are the John [Gaertners]. There's just a handful of people I can call on who can make this kind of stuff."

The National Air and Space Museum has a Lincoln Standard (seen here in 1964, just prior to becoming part of the Museum's collection).

One of the aircraft in Kellett's care is a biplane, a 1917 Standard Aircraft Corporation J-1 that was rebuilt decades ago by famed barnstormer Otto Timm, who gave Charles Lindbergh flying lessons in 1922. "It's important for me to retain as much of Timm's work as possible," says Kellett.

The J-1, which also appeared in the 1975 film The Great Waldo Pepper, has been undergoing restoration for seven years, and for the last two of those years, Kellett has had Gaertner feeding the airplane a steady flow of new, historically accurate parts.

"Occasionally, I’d come across pieces that were in really bad shape," says Kellett. "One was the throttle quadrant. It's an aluminum casting and sometimes you just can't save that stuff. I got the drawings from the Old Rhinebeck Aerodrome so John [could] cast a new part for me."

It wasn't long before Kellett gave Gaertner another project for the J-1: seatbelts. "Back then, seatbelts were five inches wide and they were cotton, canvas duck material," says Kellett. "No seatbelt people will make a seatbelt like that for you today. If you want that stuff authentic, then it's nice that John can do it." According to Kellett, Gaertner custom-made all the hardware for the new seatbelts: "And he made all the tooling so that he could make all of the fittings and all the bits that go into a seatbelt. I depend on this guy a lot for some of this really wild stuff on the airplane or I would never get it done."

At the National Air and Space Museum, Tony Carp can confirm the challenges of restoring aircraft from that era. Carp, a 20-year veteran of the Museum's preservation and restoration unit, is the team lead on a project to restore a Lincoln Standard, a variation of the J-1.

"The Lincoln Standard is a vintage biplane that we think was built in 1917 or 1918, so it's just over 100 years old," says Carp. He says his team, based at the Museum's Steven F. Udvar-Hazy Center, is working to bring the aircraft "back to a period when it was first built. Not necessarily as it rolled off the production line, but as it would have looked in the early 1920s when it was sold on the commercial market. Commercial aviation, as we know it, had to start somewhere and this is where it started, with airplanes like this one in the early 1920s, post-World War I."

Carp says his team's mission is "to bring an artifact back to a time that allows you to display it and tell a story." That, says Carp, "is what we are all about." To reach that goal, Carp taps into known resources and even eBay looking for authentic parts. If a "must have" part isn't available, the Museum will have it fabricated. The seatbelts are one such example. And, if the project requires new metal castings, the Museum knows that it can call Gaertner.

Within the U.S., Chris Hill can name only one other person who can cast metal for recreating vintage aircraft parts. "There are probably a couple of guys in Europe and maybe a couple in New Zealand and Australia," he says. "So, 10 in the world that are doing this for aviation? If you want a world-class, authentic reproduction of really anything, [Gaertner] is one of the people you need to have on your call roster."

Restoration specialist Jay Flanagan tightens the cross wire braces of the engine mount on the Lincoln Standard.

Gaertner has a shop in his home not far from Charlottesville, Virginia. Grabbing a travel mug full of coffee at the start of his day, Gaertner opens the door to his basement while keeping a wary eye on his two cats. His basement shop is now home to his mother's cat and one of the upstairs cats wants to bully the newcomer. As Gaertner heads downstairs, his mother's cat disappears into the labyrinth of hiding places created by a lathe, drill press, welding machine, 3D printer, shelves, tools, cabinets, wood airplane parts, and the covered aircraft engines resting on the concrete floor.

Although crowded, the shop is clean and more orderly than you would expect. The walls are hung with photographs of Gaertner's dream project: an Avro 504, a British aircraft that first flew in 1913. The airplane caught his interest decades ago when he was working at the National Air and Space Museum. He was trying to decide which aircraft to build as a personal project when one of his colleagues suggested the Avro. Intrigued, Gaertner used the Museum's archives to learn about the 504 and became entranced by its history and aviation significance. The 504 was the first tandem training aircraft in which an instructor, using a speaking tube, could correct the student in flight. "It trained thousands of pilots all over the world, not just Great Britain," says Gaertner.

Gaertner feeds scrap aluminum into a small furnace. He will then pour the molten metal into a muffin tin (at lower left), creating ingots he can re-melt to create new castings.

Gaertner's biggest hurdle to finishing the Avro is his desire to power it with a 100-horsepower Gnome rotary engine. Original rotary engines rarely come up for sale and can fetch $25,000 (while still requiring a rebuild). An alternative, new-build engine from New Zealand could set him back around $65,000, prompting Gaertner to consider using his metal casting skills to build his own.

During its heyday, the rotary engine required constant maintenance. According to Hill, World War I pilots were pleased if they got 20 hours on a rotary before it needed to be rebuilt—or discarded entirely. By the late 1920s, the development of the more reliable radial engine began to lessen the demand for rotary engines.

Hill flies with a pair of original French Le Rhône rotary engines that were built in 1917, an 80-hp and a 120-hp. While a stickler for historical accuracy, Hill also believes in safety. "Now that I’m rebuilding them, we do things to try and improve that reliability," he says. "Like putting in new pistons." Hill believes part of the rotary's problem was the metal used at the time. "Today, you can put in 4340 steel for the pushrods so you have double the tensile strength over the original steel," he says.

If you’re accustomed to horizontally opposed engines—like Lycomings, V-8s, and the radial engines used by World War II aircraft—understanding the workings of a rotary engine can be perplexing.

The propeller on a rotary engine is attached directly to the pistons. Together, as one unit, they spin around a fixed and hollow crankshaft. A carburetor attached to the rear of the engine fills the hollow crankshaft with a fuel-air mixture. The pistons, rotating around the crankcase, suck in the fuel by vacuum. The burned mixture is released directly to the atmosphere from an exhaust valve at the top of the piston, a factor that helps give the engine its distinctive sound. At the same time, castor oil, which does not dissolve in gasoline, moves along the crankshaft via journals to the crankcase. The oil is slung through the engine by centrifugal force and gets expelled with engine exhaust as a fine mist. As a result, oil covers anything the exhaust touches.

Although Hill does much of his own engine work, he says he's "going to have [Gaertner] do my 180-horsepower Hisso for my S.E.5." Gaertner has already rebuilt similar engines for two of Hill's pilot friends. "They both told me it was to perfection," he says. "You can't complain with that. Especially when you go out and you’re flying vintage planes on old engines. You want them perfect."

Gaertner has fashioned a mold for a Wright J5 engine oil strainer. He will use the mold to sandcast a new, historically accurate duplicate.

Rebuilding an aircraft engine in the U.S. usually requires the services of a mechanic holding an airframe-and-powerplant license, known as an A&P. But Gaertner doesn't hold the A&P, so how can he work on 100-year-old engines?

"Nobody in the world ever certified these engines," he says. "If you put them on an airplane, the airplane has to be [designated] experimental exhibition." Gaertner likens the situation to someone who owns a Ferrari with a rare engine: "They don't take it to the Chevy dealer to overhaul because that guy wouldn't have any idea what he was looking at, even though he's a qualified auto mechanic."

The Golden Age Air Museum's event was the largest U.S. gathering of rotary-powered aircraft in nearly 100 years.

Back at Grimes Airfield, Gaert­ner gestures to the various vintage aircraft that have gathered for the airshow. Some are original, some are replicas.

"Most replicas aren't built with the original structures," he says. "[They’re built] with pop-riveted aluminum tube, and they run with half of a VW engine or something like that." Gaertner pauses beside an immaculate Sopwith Pup that has come from New York. The Pup earns the professor's coveted approval.

"This plane is from Rhinebeck with a rotary engine," says Gaertner. "It's built the way the real plane was built. Like I build planes."

Tim Wright is a writer, photographer, and drone pilot who has reported on the salvage of the B-29 Kee Bird and the theft of N844AA, a Boeing 727-200.

This article is from the Spring issue of Air & Space Quarterly, the National Air and Space Museum's signature magazine that explores topics in aviation and space, from the earliest moments of flight to today. Explore the full issue.

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