Designed as a long-range anti-submarine patrol plane the Neptune first flew on May 17, 1945 and P2V-1s and -2s entered service with the U. S. Navy in March 1947. Steady technological upgrades and new orders kept the Neptune in production until April 1962. The final production version, the P2V-7 (later P-2H), began coming off the assembly line in 1954 and was the first version built with underwing jet engines.
The AP-2H designation was applied to four heavily modified SP-2H aircraft for a special program during the Vietnam War. This program, the Trails Roads Interdiction Multi-sensor (TRIM) Project was designed to use then new technologies such as FLIR (Forward Looking Infra-Red) and LLLTV (Low Light Level Tele-Vision) to track and attack North Vietnamese supplies and troops along the Ho Chi Minh Trail. Along with the sensors the aircraft were given heavy armament, with the installation of two 20mm cannon in the tail, a series of grenade launchers in the belly, two forward firing minigun pods, a minimum of two 500 lb bombs, and two 7.62mm waist guns. During 1968 and 1969 the four aircraft were assigned to VAH-21 (Navy Heavy Attack Squadron 21) at Cam Ranh Bay Vietnam. The sensors and weapons proved to be effective, but the aircraft were large, relatively slow targets and VAH-21 was withdrawn from combat in June 1969. The FLIR and LLLTV equipment was later installed in A-6 Intruders which continued the interdiction mission.
VAH-21, Sangley Point, Philippine Islands and Cam Ranh Bay South Vietnam, 1968
Pima Air & Space Museum