Juan de la Cierva
Spanish aeronautical engineer whose autogiro C.4, flown at Getafe on 17 January 1923, was the first successful rotary-wing aircraft of any kind. His articulated rotor with flapping hinges solved the problem of asymmetric lift — the Smithsonian's own record calls it necessary for the development of the practical helicopter.
Why this wins its question: Helicopter histories usually start with Sikorsky; the Smithsonian's own collection record credits Cierva's rotor mechanics as the necessary prior step. This object binds that priority — and the exact first-flight record — to the museum's curatorial text. Vital dates are deliberately absent until a biographical source is registered.
Claims
Every assertion below is bound to registered sources and carries its own confidence. Weight them; do not treat the page as uniformly authoritative.
Cierva's C.4, the first successful autogiro and the first successful rotary-wing aircraft of any kind, took flight on 17 January 1923 at Getafe airfield in Madrid.
His key invention was the articulated rotor: flapping hinges let the advancing blade rise and the retreating blade descend, equalizing lift across the rotor disc — a mechanism the Smithsonian record describes as necessary for the development of the practical helicopter.
His C.8W, imported by Harold Pitcairn in 1928, was the first successful rotary-wing aircraft to fly in the United States and the progenitor of the American gyroplane line; it is preserved in the Smithsonian National Air and Space Museum collection.