[1] The D-255 was planned to be a purpose-built attack helicopter based on the UH-1B airframe and dynamic components with a new, slender airframe and a two-seat, tandem cockpit, featuring a grenade launcher in a ball turret on the nose, a 20 mm belly-mounted gun pod, and stub wings for mounting rockets or SS.10 anti-tank missiles.

[3][4][5] The Sioux Scout included all the key features of a modern helicopter gunship – a tandem cockpit, stub wings for weapons, and a chin-mounted gun turret.

[3] The tandem cockpit placed the gunner in the lower front seat with the pilot in the rear, with both crew positions featuring flight controls.

[3] Later in 1964, the Army requested proposals for its Advanced Aerial Fire Support System (AAFSS).

However, the Bell D-262 was not selected as a finalist in the competition, which was won by the abortive Lockheed AH-56 Cheyenne.