Hughes MD-500

The successful Hughes 500/MD 500 series began life in response to a U.S. Army requirement for a Light Observation Helicopter (LOH).[3] Hughes' Model 369 won the contest against competition from Bell and Hiller. The subsequent OH-6 Cayuse first flew in February 1963.

The 500 series design features shock-absorbing landing skid struts, a turboshaft engine mounted at a 45-degree angle toward the rear of the cabin pod, a fuel tank cell under the floor and the battery in the nose. The engine exhaust port is located at the end of the cabin pod underneath the tailboom. It has a short-diameter main rotor system and a short tail, giving it agile control response and is less susceptible to weather-cocking.

Hughes won the U.S. Army's LOH contest with its OH-6 helicopter by submitting a very low and aggressive price per airframe (without an engine). Due to rising prices, the U.S. Army later re-opened the contest, where Hughes offered the machine at a more realistic price, but was undercut by the redesigned Bell OH-58 Kiowa (military JetRanger). OH-6 helicopters were still ordered by the U.S. Army, though at a much reduced number.

Hughes/MD 500

Prior to the OH-6's first flight, Hughes announced it was developing a civilian version, to be marketed as the Hughes 500, available in basic five- and seven-seat configurations.[3] A utility version with a more powerful engine was offered as the 500U (later called the 500C).

The improved Hughes 500D became the primary model in 1976, with a more powerful engine, a T-tail, and a new five-blade main rotor; a four-blade tail rotor was optional.[3] The 500D was replaced by the 500E from 1982 with a pointed nose and various interior improvements, such as greater head- and legroom. The 530F was a more powerful version of the 500E optimized for hot and high work.