AC-130 gunship is a heavily-armed ground-attack aircraft. The basic airframe is a C-130 Hercules which is then converted into a gunship and for aircraft support. It is a variant of the C-130 Hercules transport plane. The AC-130A Gunship II superseded the AC-47 Gunship I in Vietnam. The gunship's sole user is the United States Air Force, which uses AC-130H Spectre and AC-130U Spooky variants. The AC-130 is powered by four turboprops and has an armament ranging from 20 mm Gatling guns to 105 mm howitzers. It has a standard crew of twelve or thirteen airmen, including five officers (two pilots, a navigator, an electronic warfare officer and a fire control officer) and enlisted personnel (flight engineer, electronics operators and aerial gunners).