The Hollmann HA-2 / HA-2M Sportster was a two-seat sport gyrocopter developed in the United States during the early 1970s. Designed by Martin Hollmann, a senior aerospace design engineer based in Orlando, Florida, the aircraft was specifically engineered to be accessible to homebuilders with limited access to power tools. Design work commenced in June 1969, and the construction of the prototype began in December 1972. The prototype, registered as N158, completed its first flight in October 1974 and was subsequently certified in the FAA Experimental category. Test flights for the aircraft were concluded by January 1976.
Technically, the HA-2M Sportster was innovative for its era, incorporating a collective-pitch rotor mechanism and a mechanical prerotator. This system used a clutch to engage the engine and prespin the rotor to 240 rpm before takeoff, which significantly shortened the takeoff run and provided the potential for jump-starts. Additionally, the aircraft was equipped with a rotor brake to facilitate ground handling and taxiing on narrow strips. The aircraft's configuration consisted of a side-by-side two-seat cockpit with a single pusher engine driving a propeller.
Powerplant options varied by configuration. The prototype N158 utilized a 130 hp Franklin Sport 4B four-cylinder horizontally opposed engine. Other documented homebuilt configurations utilized a 150 hp Lycoming O-320 engine. Performance specifications for the Franklin-powered version included a maximum speed of 145 km/h (90 mph), a cruising speed of 121 km/h (75 mph), and a rate of climb of 213 m/min (700 ft/min). The aircraft had a rotor diameter of 8.53 m (28 ft) and a maximum loaded weight of 476 kg (1,050 lb).
Marketing and kit production were handled by Winther Hollmann Inc. / Hollmann Aircraft, based in Cupertino, California. By May 1976, the company was issuing formal technical documentation for the HA-2M. The design received several accolades in the mid-1970s, including a "Best Original Design" award at the 1976 EAA Oshkosh meeting, an "Outstanding New Design" award at the 1976 PRA Fly-in in Rockford, Illinois, and a "Best Autogiro" award at the 1977 EAA Annual Antique Fly-in in Watsonville, California. While production numbers are not officially recorded, the prototype and at least one other airframe are known to have existed, the latter being involved in an NTSB-reported accident in 1976.