The AUM-N-2 Petrel, also known as Kingfisher C and AUM-2, was an air-to-surface missile produced as part of Project Kingfisher for the United States Navy. Intended for use against enemy surface ships and surfaced submarines, giving aircraft the ability to deliver aerial torpedoes from outside the range of defensive armament, it saw brief operational service in the late 1950s. The project was never considered a high priority by the Navy however, as it was useless against submerged submarines, which were considered the greatest potential threat. Following its withdrawal from operational usage, the Petrel was used as a target drone, receiving the designation AQM-41A shortly before being retired from service altogether. Design and development The development of the Petrel began in August 1944, when the U.S. Navy Bureau of Ordnance (BuOrd) began Project Kingfisher, intending to develop a series of standoff torpedo weapons. The "Kingfisher C", later designated AUM-2 and then as AUM-N-2 (for 'Air-to-Underwater Missile'), was designed as an air-launched jet-powered missile which carried a torpedo as its payload. Various different design options were considered for this missile; the final choice was a Mark 21 Mod 2 torpedo, in diameter, with a Fairchild J44 turbojet engine providing thrust, wooden fins and wings in span, and a nose fairing housing guidance equipment. On launch the , missile dropped to above the water and cruised at Mach 0.5 towards the target, using semi-active radar homing. Once the missile had reached a range of just under from its target, the engine would be shut down and all wings and fins jettisoned. The torpedo dropped on a free trajectory into the water and began to home in on the target. The weapon was suitable for use against surface targets only—primarily ships and surfaced submarines, with the Navy considering the weapon effective against targets traveling at up to . The AUM-2 was usually carried by the Lockheed P2V Neptune, although the Grumman S2F Tracker was also considered as a potential carrier aircraft. Operational history Under the authority of the National Bureau of Standards, tests of the AUM-2 began in 1951; by this time, the Mark 41 torpedo had replaced the Mark 21 Mod 2 as its payload. Development was transferred to the Guided Missiles Division of Fairchild Aircraft in 1954, with the missile being declared operational in 1956; the Petrel project was publicly revealed by Fairchild in the company's annual report for that year. The