28 September 1920 – (USA) — American pilot Howard Rinehart, flying a Dayton-Wright R.B Racer, becomes the first person to fly an airplane fitted with retractable landing gear. (1)
Howard M. Rinehart, holder of the [Aero] club’s certificate No. 266, was a top-ranking, seasoned flier for the Wright organization. He had been an instructor in Augusta in 1911 and had flown for the Mexican revolutionary Pancho Villa in 1914. He was in charge of all tests for the De Havilland 4s that Dayton–Wright produced in large numbers during World War I and had spent many years in research work, which gave him the title of aeronautical engineer on the company’s list of executive officers.
The RB-1 was a high-wing monoplane with a monocoque fuselage and cantilever wing built around a solid balsa wood core laminated with plywood and covered in linen that incorporated a mechanism designed by Charles Hampson Grant to vary its camber in flight by adjusting the angles of the leading and trailing edges, with the trailing edge being a plain flap, and the leading edge functioning similarly. The aircraft also featured a retractable undercarriage operated by a hand-crank making it one of the first instances of undercarriage retraction for aerodynamic benefit alone.
Sources: (1) Skytamer.com; (2) Howard Max Rinehart (earlyaviators.com); (3) Wikipedia