Photos: A century of helicopters

Through the first decades of the 20th century, the airplane had its coming of age in World War I dogfights and the postwar barnstorming craze; in 1927, Charles Lindbergh flew across the Atlantic, and in the early 1930s, Wiley Post made a pair of round-the-world flights.

The helicopter, meanwhile, was still awaiting a technological breakthrough. That's because it was a much more difficult mechanical problem to solve than was the fixed-wing airplane. Where airplanes get their lift from the wings, allowing for the use of a relatively modest engine for propulsion, helicopters rely on their rotors for both functions. Torque was another serious challenge--inventors kept trying new ways to counteract the twisting movement that was directed into the helicopter body from its large main rotor. Even today, helicopters are a noisier, shakier ride than their winged counterparts.

One hybrid approach that got a few tries over the years was the autogyro. The one in this undated photo (probably from the early 1930s) is a Pitcairn PAA-1. The big overhead rotor aside, it's got a pretty standard monoplane fuselage. Autogyros were a big deal, at least briefly--Amelia Earhart flew them, while Herbert Hoover heaped praise on manufacturer Harold Pitcairn.