Developed from the civil Bell Model 206A JetRanger helicopter, the US Army's OH-58 Kiowa served extensively in Vietnam in the light observation and scout roles. The Model 206 was built in significant numbers for military service and remains in widespread use with the US Army in upgraded OH-58C form. Numerous foreign air arms also operate the military Model 206A/Bs primarily in the training role. The type also serves as a trainer with the US Navy as the TH-57 SeaRanger and with the US Army as the TH-67A Creek.
The Model 406 was developed to meet a US Army requirement for a helicopter capable of observation duties, as well as support of attack helicopters and direction of artillery fire. The Model 406 introduced a mast-mounted sight, specialized avionics and a four-bladed main rotor with composite blades. Some 424 OH-58Ds were converted from previous OH-58 models in a process that was completed in 1998.
The first OH-58D prototype made its maiden flight on 6 October 1983. Deliveries began in December 1985, and the first deliveries to a Europe-based unit took place in June 1987. Under Operation Prime Chance, 15 OH-58Ds were modified from September 1987 for operations against Iranian fast patrol boats in the Persian Gulf: provision was made for Stinger air-to-air missiles and Hellfire anti-tank guided missiles in addition to 0.5-in (12.7-mm) machine-gun pods and rocket launchers.
The armament options of the Prime Chance OH-58D were retained for an armed OH-58D version, designated as the OH-58D(I) Kiowa Warrior, to which standard all OH-58Ds have been upgraded. Taiwan is the only operator of new-build full-standard OH-58Ds, receiving 26 examples from July 1993. Saudi Arabia operates 15 of the simplified Model 406CS Combat Scout variant.