Unlike previous USAF medium bombers, the B-47 carried a combination bombing and navigation system operated by a bombardier-navigator. By automating many functions, this system reduced crew size by eliminating the need for a separate bombardier and navigator.
The bombardment part of the system included the Y-4 bombsight, an automatic pilot and an AN/APS-23 radar linked to a computer. Using these components, the bombardier-navigator could bomb targets either visually or by radar.
Designed for installation in the nose of B-47B and B-47E bombers, the Y-4 bombsight provided an optical view of bombing targets. The geared lens mount of the Y-4 moved to keep the line-of-sight on the objective. Unlike the World War II bombers of the previous decade, this allowed the pilot to take evasive action as he approached the target without the operator losing his aiming point.