UC-123B/K Ranch Hand
By 1961, the guerrillas in Vietnam demonstrated how well they had learned ambush tactics from their Viet Minh predecessors. American soldiers conducting "search and destroy" missions in their armored personnel carriers and on foot would traverse into forests so dense that large numbers of heavily armed enemy could lie undetected in ambush only scant yards from the unsuspecting Americans. That is, of course, unless the Americans could find some way to see through the dense forest and jungle, to strip away the foliage that so effectively blinded the French army.
After coordinating with the South Vietnamese Government, the Americans turned to action in November 1961, when 6 C-123 Provider transports, specially modified for aerial-spraying operations, left Pope Air Force Base, North Carolina, en route to South Vietnam. Although earlier small-scale defoliation experiments had been conducted in Vietnam with both C-47 transports and H-34 helicopters, the decision to go to the more modern C-123 as the primary defoliant aircraft proved an excellent choice.
The C-123 had a rugged airframe, low-speed maneuverability, and good visibility that were near ideal for the spray mission. The decision to add armor plating to the cockpit area would prove equally wise (and would be enjoyed on a repetitive basis by the aircrews). The most visible modification to the spray aircraft was the MC-1 Hourglass spray system, combining external spray booms on wings and fuselage and an internal 1,000-gallon herbicide tank and pumps in the cargo hold. The modified aircraft were designated UC-123B to differentiate them from standard tactical transports. In spite of this, the aircraft could be and were often converted to regular transports as operational demands required.
Major modification of all spray aircraft was undertaken in July 1966. A new spray system, designated the A/A 45Y-1 Dispenser System, was fitted. Ssome aircraft had been delivered from the United States in 1965 and early 1966 with the system already installed. This new system was capable of spraying 250 to 400 gallons per minute, which was sufficient to provide a coverage of 3 gallons of defoliant per acre under a variety of tactical conditions. The completed system had a 20-horsepower pump, which provided the increased spray capability. A 10-inch dump valve also improved the "quick dump" capability from 75 to 29 seconds during aircraft emergencies.
In May 1968 some much-appreciated help came to the squadron with the arrival of the new K-model Providers, featuring two J-85 jet auxiliary engines mounted under the wings outboard of the two main piston engines. By April 1969, all Ranch Hand UC-123Bs had received the K-model conversion, being designated UC-123Ks. The additional engines gave improved the performance of the aircraft as issues of enemy ground fire continued to worsen.
UC-123 aircraft were also used in Vietnam to spray insecticide as part of the Military Assistance Command, Vietnam malaria control program. Spray aircraft were used for insect control in other areas as well. Even after the defoliation mission in Southeast Asia had ended in 1970, spray aircraft continued with this mission. This had in fact been the original mission of the Special Aerial Spray Flight, the first unit to perform the defoliation mission.
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