The original OH-6 Cayuse helicopter proved its worth during the Vietnam War in the light helicopter role. The designers at Hughes realized there was a market for a light multi-mission helicopter with an improved equipment fit than the OH-6 and Model 500M. The resulting design was the Model 500MD Defender which first flew in 1976. It was tailored for specific roles including unarmed observation and an armed scout helicopter equipped with TOW anti-tank missiles. An anti-submarine version was developed with a search radar, magnetic anomaly detector and the capability to carry lightweight aerial torpedoes. The helicopter was popular with customers like Kenya who could buy a capable anti-armor helicopter for less than half the cost of a gunship such as the AH-1 Cobra or the AH-64 Apache. Israel used the Defender extensively during the conflicts of the late 1970s and 1980s against Syrian armored forces. The Defender was later built as an improved version as the MD530MG, with increased engine power, handling, avionics, and a redesigned forward fuselage. Later developments included a mast mounted sight. In December 2012, Boeing demonstrated their Unmanned Little Bird to the South Korean Army. The pilotless aircraft flew autonomously in a 25-minute demonstration for the purpose of showing unmanned capabilities technologies, such as enhanced ISR and resupply, in the system that could be integrated into Army MD 500 helicopters. In October 2015, Korean Air Aerospace Division unveiled a mock-up of their unmanned MD 500, designated the Korean Air Unmanned System-Vertical Helicopter, featuring blacked out windows, a large fuel tank where the rear seats would be that extends endurance to four hours, and an armament of two Hellfire missiles and a 2.75 in rocket pod; unlike Boeing's optionally manned and unarmed ULB, the KUS-VH is completely unmanned and armed as well as having an EO/IR sensor. The KUS-VH is envisioned to perform missions including ISR, attack, aerial delivery, coast guard, amphibious landing support, and emergency reinforcement to back up manned helicopter units. A KUS-VH unit would consist of two to four aircraft and sensor packages, a ground control system and ground support system, and it could operate alone or in conjunction with manned attack helicopters. A request for proposals for an unmanned scout helicopter is expected in 2016-2017, for which the company says making the up to 175 MD 500s unmanned would be a cheap way of reusing them after retirement from service over the next 10 years for safely performing dangerous attack missions. MD Helicopters had submitted a version called the MD 540F in the U.S. Army's Armed Aerial Scout program. This caused Boeing to try and block MD Helicopters from participating, citing agreements the companies struck in 2005 to offer the Mission Enhanced Little Bird in the Armed Reconnaissance Helicopter program. As part of the venture, MD Helicopters sold intellectual property related to the aircraft's design. The two companies lost the bid and the program was ultimately cancelled. When MD Helicopters disclosed plans to offer the MD 540F in the AAS program in April 2012, Boeing claimed that they could not sell any "similarly configured" aircraft to any U.S. or foreign military organization. Boeing offered their AH-6 in the competition. MD Helicopters said Boeing did not object to previous sales to armed forces and governments in Japan, Jordan, and Italy, as well as to U.S. special operations, and local U.S. police forces. Restrictions on selling aircraft similar to the Little Bird, domestically or to foreign users, would have put the company out of business. In July 2013, a federal court ruled that MD Helicopters could not be blocked from offering their aircraft. The Army ended the AAS program in late 2013.
Variants
;500D Scout Defender ;500M Defender ;500M/ASW Defender ;NH-500E built under license by Breda Nardi since 1990 ;NH-500M Defender ;500MD Defender ;500MD/ASW Defender ;500MD/TOW Defender ;500MD/MMS-TOW Defender ;500MD Quiet Advanced Scout Defender ;500MD Defender II ;500MG Defender ;520MG Defender ;520MK Black Tiger ;530MG Defender ;MD530 Nightfox ;MD530MG Paramilitary Defender ;MD540F ;MD530G
