The Lockheed AC-130 Spectre is armed tactical support version of the popular C-130 Hercules. The celllula base is built by Lockheed and Boeing is responsible for its conversion into a gunship flying. The AC-130 Gunship II replaced the AC-47 and AC-119 in the tactical support role in the Vietnam War. The USAF has used AC-130 for close support, interdiction and force protection for the area. The close support includes support for ground troops, escorting convoys and operations in an urban environment. Interdiction missions are conducted against planned targets and opportunities. Force protection missions include air defense of fixed installations or fortified areas. The first AC-130 gunship arrived in South Vietnam 21 September 1967 under the Gunship II program, and began operations on Laos and Vietnam that year. Since October of 1968 reached a sufficient number of AC-130 to form a squadron, the 16th Special Operations Squadron (SOS) dell'8th Fighter Wing, Royal Air Force air base in Thailand Ubon. Since December 1968 many AC-130 flying under escort of F-4 Phantom II 479th TFS, usually three for each Phantom Gunship. During the Vietnam conflict the different versions of the AC-130, following the "Pave Pronto" were equipped with the magnetic sensor (BMA) called Black Crow (AN/ASD-5), a passive system with high sensitivity, with a planar antenna in a radome positioned to the left of the muzzle, able to locate the smallest anomaly of the Earth's magnetic field.