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  • Hughes OH-6 Cayuse (Loach) Light Observation / Attack Helicopter

    The nimble little Hughes OH-6 Cayuse served extensively with US Army forces in the Vietnam War and, in various forms, exists today.

     Updated: 5/11/2016; Authored By Staff Writer; Content ¬©www.MilitaryFactory.com

    The Hughes OH-6 "Cayuse" (popularly recognized as the "Loach") was a revolutionary light helicopter mount primarily in service with the United States Army and saw combat service during the Vietnam War (1955-1975). The type was born from the US Army Light Observation Helicopter (LOH) program (which provided its "Loach" nickname) and ultimately proved an excellent helicopter system seeing only limited service in the inventories of several American allies worldwide. Fewer than 2,000 of the type were produced though the original went on to spawn a plethora of viable performers including the Hughes 500 "Defender" and the special forces-minded MH-6 "Little Bird".

    Following the close of World War 2 in 1945, rotary-wing flight entered a period of advancement and refinement to produce a viable helicopter solution for both military and civilian markets. The Korean War (1950-1953) was the first large-scale combat zone use of helicopters by United States forces who had been entertaining the prospects of vertical flight as early as the 1930s. The Korean War ushered the helicopter in as a Search and Rescue (SAR) mount and transportation of the wounded across Korea's unforgiving terrain.

    Years after the close of the war, the United States Army unveiled "Technical Specification 153" in 1960, establishing its Light Observation Helicopter (LOH) program. As the title suggested, the program goal was to stock a dedicated, light-class, rotary-wing system with a multipurpose battlefield role. The helicopter would be called upon to undertake various missions including that of SAR, MEDEVAC, observation, transport, reconnaissance, escort, Close Air Support (CAS) and direct attack.

    Famous American flight pioneer Howard Hughes (1905-1976), still alive by this time, was operating an aircraft division through his Hughes Tool front as the Hughes Tool Company - Aircraft Division. Understanding the potentially lucrative government contract waiting for such a system, he positioned his company to deliver. Hughes engineers developed the Hughes "Model 369" and, joining a dozen other firms, submitted their LOH proposal to the US Army.

    The United States Army initially selected two designs - one from Bell Helicopters and the other from Fairchild-Hiller. However, the Hughes submission was later added to the fold and all three concerns were funded for development of five prototype vehicles. The Hughes Model 369 was outfitted with an Allison T63-A-5A series turboshaft engine of 252 horsepower and recorded its first flight on February 27th, 1963. Should the Hughes development succeed, Allison Engine Company stood to make its own fair share of profit from the long-term US Army commitment. The United States Army designated the Hughes submission as the "YHO-6A" until a complete rewrite of American military designations occurred in 1962, prompting a change to the model as the "YOH-6A" (as such, serial production would spawn the "OH-6A").

    With US Army evaluations of each prototype ongoing, the underpowered Bell offering was formally dropped from contention and the US Army decision favored the Hughes design over the Fairchild-Hiller. It was deemed, based on Hughes' estimates, his units would be most cost effective in the long run. It later turned out that Howard Hughes purposely undervalued his estimate and deceptively won out against Fairchild-Hiller - his reasoning being that a long-term US Army commitment to his helicopter would, over time, make the deal profitable at some point. The US Army charged Hughes for 714 units with the serial production contract formally announced in May of 1965. Sensing its growing battlefield requirements, the US Army then raised the production ceiling to 1,300 units in all. The helicopter was inducted as the OH-6 "Cayuse" and would eventually take on the in-the-field nickname of "Loach" in reference to its "LOH" origins.

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    Hughes OH-6 Cayuse (Loach) Technical Specifications

    Service Year: 1966
    Type: Light Observation / Attack Helicopter
    National Origin: United States
    Manufacturer(s): Hughes Tool Company, Aircraft Division - USA
    Production Total: 1,434

    Structural (Crew Space, Dimensions and Weights)

    Operating Crew: 2
    Length: 30.84 feet (9.4 meters)
    Width: 27.33 feet (8.33 meters)
    Height: 8.53 feet (2.60 meters)

    Weight (Empty): 1,975 lb (896 kg)
    Weight (MTOW): 3,549 lb (1,610 kg)

    Installed Power and Standard Day Performance

    Engine(s): 1 x Allison T63-A-5A OR T63-A-700 turboshaft engine developing 317 horsepower to a four-blade main rotor and two-blade tail rotor.

    Maximum Speed: 175 mph (282 kph; 152 knots)
    Maximum Range: 267 miles (430 km)
    Service Ceiling: 15,994 feet (4,875 meters; 3.03 miles)
    Rate-of-Climb: 2,067 feet-per-minute (630 m/min)

    Armament / Mission Payload

    Optional and variable (attack and special forces versions only). Can include a combination of the following across two fuselage wingstubs (though some weapons operated from cabin doors):

    7.62mm M60 general purpose machine gun
    7.62mm M134 minigun pod
    12.7mm M2 Browning heavy machine gun pod
    2.75" (70mm) Hydra 70 rocket pod (7 x rockets ea).
    TOW Anti-Tank Guided Missile (ATGM) pod (2 x missiles ea).
    AGM-114 Hellfire Anti-Tank (AT) missile pod (2 x missiles ea).

    Also crew-served small arms of various kinds - sniper rifles, assault rifles and light machine guns as required.

    Global Operators / Customers

    Dominican Republic; Denmark; Japan; Spain; Taiwan; United States

    Model Variants (Including Prototypes)

    YOH-6A - Prototype Designation

    OH-6A - Initial Production Model Designation; fitted with 1 x Allison T63-A5A turboshaft engine.

    OH-6A NOTAR - Experimental Platform; sans tail rotor system.

    OH-6B - Fitted with 1 x Allison T63-A-720 turboshaft engine.

    OH-6C - Proposed Variant; fitting 1 x Allison 25-C20 turboshaft engine; five-bladed main rotor.

    OH-6J - Japanese Ground Self-Defense Force Version; license-production by Kawasaki Heavy Industries; based on OH-6A production model.

    OH-6D - Japanese Ground Self-Defense Force Version; license-production by Kawasaki Heavy Industries; based on Hughes 500D production model.

    EH-6B - Electronic Warfare Aircraft (EWA) Platform foruse by special forces; airborne command post.

    MH-6B - Special Forces Variant

    TH-6B - US Navy Variant; based on the MD-369H.

    AH-6C - Attack Platform; based on the OH-6A production model; provision for outboard weapons on wingstub fittings.

    MH-6C - Special Forces Variant