By A.J.S. RAYL
Air & Space Magazine
In the years following the Wright brothers’ first flight, anyone and everyone with a daring idea produced a flying machine, from Albert Einstein and his ill-fated wing to Thomas Edison and his box kite-type rotor biplane. “There were a lot of fairly eccentric designs in the patents from this era,” says J. Gordon Leishman, professor of aerospace engineering at the University of Maryland. But aviation history apparently forgot the hybrid tilt-rotor/tilt-wing helicopter-airplane that Nikola Tesla dreamed up in 1921—until this summer, on the 150th anniversary of his birth.
Although popular American history has largely ignored Tesla, the Serbian immigrant was heralded as the wizard of electricity in the first half of the 20th century. From development of the alternating current and the use of powerful turbine engines to radio and remote control, Tesla invented big. He installed his electricity-generating machinery at Niagara Falls, thereby creating the Niagara Falls Power Company, and lit the World’s Fair in Chicago in 1893 in conjunction with the Westinghouse Company. So significant were his contributions that Tesla’s 75th birthday in 1931 made the cover of Time magazine. “To this day there’s a kind of mystique around this guy that’s bigger than life,” says inventor Woody Norris, a Tesla fan in southern California, who will soon introduce a personal vertical-takeoff-and-landing aircraft, the AirScooter.
In January 1928, the U.S. Patent Office granted Tesla what would be his final patent, for a “novel method of transporting bodies through the air.” He described and sketched an open box-type craft with a tilting propeller and wing that theoretically would enable the vehicle to rise vertically and fly horizontally, though he also suggested a design in which two propellers “coaxially or otherwise disposed” would “revolve in opposite directions,” powered by his turbine engine.
Contrary to popular Tesla myth, this concept was not the inspiration for vertical-takeoff-and-landing craft, but it appears in hindsight that he logged a few significant first claims. “This may be the first tilt-rotor/tilt-wing concept,” Leishman says. Adds Roger Connor, a curator of vertical flight at the National Air and Space Museum, “The theoretical concept is very similar to the Convair XFY-1 Pogo that we saw in the 1950s, the Bell XV-15 in the late 1970s, and in the Osprey today.” And Tesla’s discussion of using a turbine engine is “astonishingly prescient,” Connor says. “In vertical flight particularly, if you don’t have a turbine, you’re not going anywhere, so he hit the bull’s-eye on that one, and to my knowledge this is the first time anyone proposed a turbine on a rotorcraft.”
Leishman says it’s clear that Tesla did some serious thinking. He considered
the issue of control in forward flight, designing his aircraft with ailerons
and conventional flight control surfaces. But when it came to hovering,
Tesla was hopelessly naive about the vagaries of rotary wing flight. “He
missed how long the blades would have to be to give you any kind of
meaningful lift and all the issues dealing with stability,” says Norris, who
encountered the physics first-hand with his AirScooter.
“The other thing that’s lacking is a way of compensating for torque reaction, which means it could never be practical,” says Leishman. “On a conventional helicopter, you’ve got a tail rotor that provides the anti-torque.” But Tesla “basically left the tail off this thing,” Connor points out.
Tesla probably could have gotten airborne with his turbine engine, “but
the tendency would be for the body of this machine to rotate in the opposite
direction to the propeller,” Leishman says. As Norris puts it, “The thing
would just spin maddeningly in a circle.”
By 1928, Tesla was without a laboratory or funding and headed toward impoverishment, passing much of his time tending to the pigeons in New York City’s Bryant Park. He died alone and penniless in 1943 at 86.
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