The most important helicopter produced by Hughes Aircraft Division prior to the company's acquisition by McDonnell Douglas in 1984 was the two-seat, light-observation helicopter (LOH) Model 369, the company's entry into the U.S. Army's 1963 LOH competition. Initially called "Loach," an adaptation of its acronym, it was officially called the "Cayuse." It was also know as the "Flying Egg," and when equipped for combat, the helicopters were known as "Killer Eggs." The modern-day OH-6 variants flown by the U.S. Army's Special Operations Forces are known as "Little Birds," and because of their ability to strike undetected during darkness, earned Task Force 160 the right to call themselves "Night Stalkers."
The Army initially ordered 1,438 OH-6As for use during the Vietnam conflict. First flown in February 1963, the OH-6A Cayuse entered service in September 1966, establishing 23 world records for speed, distance and altitude. The Cayuse was Hughes' longest-running helicopter program and, during the Vietnam conflict, as many as 100 OH-6As were built a month. The OH-6D was an improved version with more advanced electronics and heavier armament. The OH-6 also was exported as the Model 500 Defender. It served in Granada and Panama during the 1980s, as well as in the Gulf wars, Somalia and the Balkans.
The commercial version was the Hughes 500, which became the MD 500 series after McDonnell Douglas acquired Hughes Helicopters in January 1984.
The MD 520N® pioneered the NOTAR® anti-torque system concept that replaces the traditional tail rotor using compressed air to offset torque instead of a conventional tail rotor. Versions also included the Model 530 Defender, a variant with refined aerodynamics and more power, and the AH-6 Model 530 version for U.S. Special Forces. A NOTAR version of the heavy-lift Model 530 became the MD 530N. Variants included the AH-6J attack helicopter and MH-6J insertion and extraction transport, based on the MD 530F. These featured a more powerful engine and improved avionics, including an embedded global positioning system/inertial navigation system and forward-looking infrared.
On Jan. 19, 1999, MD Helicopters Holding Inc., an indirect subsidiary of the Dutch company RDM Holding Inc., purchased Boeing's MD 500, MD 600N® and MD Explorer® series of light helicopter product lines, including the MD 500E and MD 530F® single-engine helicopters with conventional tail rotors, the MD 520N and MD 600N single-engine helicopters with the NOTAR system, and the MD Explorer series of twin-engine, eight-place helicopters. By that time, more than 4,700 Model 500-series helicopters had been produced. Patriarch Partners, LLC, an investment fund based in New York and Charlotte, N.C., acquired MD Helicopters from RDM in 2005.
||Feb. 27, 1963
||Military scout/commercial helicopter
||One 317-shaft-horsepower (236-kW) Allison T63-A-5A
||150 mph at sea level
|Initial climb rate:
||1,840 feet per minute
|Max. takeoff weight:
||26 feet 4 inches
|Length overall, rotors turning:
||30 feet 9.5 inches
||8 feet 1.5 inches
|Main rotor disc area:
||544.63 square feet
||2 crew, 2 to 4 passengers or 4 armed troops; (500MG) 7 armed troops or 2 stretchers; (600N) 7 to 8 passengers