2016 Year at a Glance

2016_Year-at-a-GlanceThe Year at a Glance – Task Force Whirlwind – U.S. Army Evaluation of Bell YOH-4, Hiller YOH-5, and Hughes YOH-6
Light Observation Helicopter (LOH) Development Program

In February 1961, twelve contractors had submitted design proposals in response to the design competition for the U.S. Army’s Light Observation Helicopter. On May 19, 1961, The Army Chief of Staff approved the Design Selection Board’s recommendations to develop the Bell D-250 (YHO-4A), the Hiller 1100 (YHO-5A) and the Hughes 369 (YHO-6A). Each contractor was to provide 5 helicopters for further competitive evaluation and final selection of one design for production.

Testing started in January 1964. The first helicopter of each type was used for initial pilot training and 1,000-hour accelerated logistical tests at Fort Rucker, Alabama. The second helicopter was used for engineering and aerodynamic tests by the U.S. Army Test Activity at Edwards Air Force Base, California. The third helicopter participated in tactical and operational suitability tests at Fort Rucker. The fourth helicopter was provided with armament installations for evaluation at Camp Hunter Liggett, California and the fifth helicopter participated in avionics and air transportability testing at Fort Rucker and Eglin Air Force Base, Florida.

Task Force Whirlwind members are shown at Camp Hunter Liggett, California on May 18, 1964 with the three prototype helicopters. Initially, each of these helicopters was provided with two armament kits. The XM-7 kit consisted of a dual M-60 machinegun installation. The XM-8 kit consisted of a single 40 mm grenade launcher installation. Upon completion of these tests, the helicopters went to Edwards Air Force Base for engineering and aerodynamic testing of the armament configurations.

The official starting date of the LOH competitive evaluation was January 1, 1964. All evaluations were completed by June 30, 1964. As a result of the evaluation, Hiller's YOH-5 and Hughes' YOH-6 were selected to compete in a program cost analysis bid for the contract. The Hughes bid won the contract, although Hiller protested the contract award, and in 1965, the YOH-6 was redesignated as the OH-6A Cayuse with variants of this aircraft remaining in both military and civilian use today.

Note that the aircraft were originally designated YHO- (Y – Prototype, H – Helicopter, O – Observation). In September 1962, U.S. military aircraft designations were standardized between the services, and these three U.S. Army helicopters were redesignated YOH-4, YOH-5 and YOH-6. The original HU-1 ‘Huey’ designation was also changed to UH-1.

Source: “LOH Development and Test Program” by Major Boyce B. Buckner, U.S. ARMY AVIATION DIGEST, August 1964.

(Photos by Ray Robb, US Army; Main photo by Raymond Robb; text by Raymond Robb)

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