The history of the Hughes OH-6 Cayuse helicopter is a long and illustrious one, full of accomplishment and faithful service. Nicknamed the “Loach”, this small observation chopper saw a lot of active duty and more than achieved the original goals set when it was designed.
The OH-6 Cayuse was designed to compete in the U.S. Army LOH (Light Observation Helicopter) competition in 1963. Originally called the Hughes Model 369, the OH-6 Cayuse competed against 12 other proposals. The final three in consideration where the Hughes Model 369, the H23 Raven concept from Fairchild-Hillier and the early OH-58 Kiowa prototype from Bell.
The Model 369 was designated YOH-6A by the Army and featured an Allison T63-A-5A engine with 252hp. It took its maiden flight on February 27 1963. The Bell was dropped because it was underpowered and it was down to the final two. Trials took place at Fort Rucker, Alabama during 1963, where the Hughes came out victorious.
The OH-6A Cayuse won out, partly because it was superior and partly because Hughes priced it cheaper. Nevertheless, the OH-6 Cayuse became the official U.S. Army LOH helicopter and an order for 714 of them was placed with Hughes. That would later be increased to 1,300, with 1,434 being made in total.
The primary features of the OH-6A Cayuse included quiet rotors, high performance and small size. This combination made it ideal for the purpose for which the army had instigated the competition and made it perfect for the role. The helicopter was light, small and easily maintained too, making it ideal for military use.
The two man crew sat forward with the engine above them. In the rear were two removable seats that could carry people or light cargo. It was small enough to carry fuel, crew and small stored and nothing else. The engine was coupled with a four-bladed rotor and a twin bladed tail rotor. The body’s egg shape became very distinctive and coined the named “Killer Egg.”
The OH-6 Cayuse saw its first action in Vietnam in 1966 when it was used for medevac, troop transport, observation and a range of other duties. Around 100 of them were used in all.
The OH-6B Cayuse uprated the Allison engine to 420hp to boost performance. The OH-6C Cayuse added a 5-bladed rotor for quieter operation. Then came the EH-6B, an electronic warfare platform for special forces use and the MH-6C, also for special forces. The OH-6C Cayuse was most famously used by the 160th SOAR, who earned the name Night Stalkers for their ability to use the helicopter to great success in night operations.
Fairchild-Hillier weren’t pleased with the way Hughes won the competition and forced a rematch in 1968. This saw Bell compete with what would become the OH-58 Kiowa. The Kiowa performed well and with the requirement of sealed bids to secure the contract, Bell undercut Hughes to win. This would effectively see the end of production for the original OH-6 Cayuse. The final helicopter rolled of the line in 1970.
Fortunately for Hughes, they had developed a civilian variant of the OH-6 Cayuse, the Model 500 which was selling well across the world. It would place Hughes at the forefront of helicopter engineering and bring them to the attention of McDonnel Douglas in the 1980s.
The power, flexibility, size and capability of the OH-6B Cayuse saw it spawn the MH-6 “Little Bird.” When armed, the helicopter could carry either a XM27E1 7.62mm machine-gun kit or a XM75 40mm grenade launcher on the port side of the fuselage. A flexible gun could be mounted on the aft door on the starboard side.
The MH-6B would act as a scout and light attack helicopter with the special forces. This version used infra-red suppressed exhaust, night vision integration, turret mounted FLIR and seats for four troops or fittings for two miniguns.
The AH-6C was a modified OH-6 Cayuse used by special forces with the same modifications as the MH-6B but with the added capacity of rocket pods fitted with Hydra rockets or TOW missiles.
The EH-6E was an electronic surveillance package ordered by the Army for special forces use. It is believed three of these were made and included the “Black Hole” infra-red suppression system, five bladed rotor, quiet tail rotoe and advanced avionics.
The MH-6E was based on the alternative Model 500D Quiet Advanced Scout Defender developed by Hughes. These too were used by special forces and procured under a black budget. Fifteen of these MH-6E’s were believed to have seen service.
AH-6F was another light attack version of the OH-6 Cayuse and saw extended testing in Florida. As well as the armament above, a M230 chain gun was also trialed, as was a Stinger air-to-air variant. The AH-6G and MH-6H both saw engine upgrades but the remainder of the airframe retained the characteristics of the AH-6.