Lockheed P-2 Neptune

P-2 (P2V) Neptune
SP-2H of VP-7 over the Atlantic in the mid-1960s.
Role	Maritime Patrol and Anti-Submarine Warfare
National origin	United States
Manufacturer	Lockheed
First flight	17 May 1945
Introduction	March 1947
Retired	1984 From military use
Primary users	United States Navy Japan Maritime Self Defense Force Royal Australian Air Force Royal Canadian Air Force
Variants	Kawasaki P-2J

The Lockheed P-2 Neptune (designated P2V by the United States Navy prior to September 1962) was a Maritime patrol and anti-submarine warfare (ASW) aircraft. It was developed for the US Navy by Lockheed to replace the Lockheed PV-1 Ventura and PV-2 Harpoon, and being replaced in turn with the Lockheed P-3 Orion. Designed as a land-based aircraft, the Neptune never made a carrier landing, although a small number of aircraft were converted and deployed as carrier launched stop-gap nuclear bombers which would have to ditch or recover at land bases. The type was successful in export and saw service with several armed forces.

Development of a new land-based patrol bomber began early in World War II, with design work starting at Lockheed's Vega subsidiary as a private venture on 6 December 1941. At first, the new design was considered a low priority compared to other aircraft in development at the time, with Vega also developing and producing the PV-2 Harpoon patrol bomber. On 19 February 1943, the U.S. Navy signed a letter of intent for two prototpe XP2Vs, which was confirmed by a formal contract on 4 April 1944 with a further 15 aircraft being ordered 10 days later. It was not until 1944 that the program went into full swing. A major factor in the design was ease of manufacture and maintenance, and this may have been a major factor in the type's long life and worldwide success. The first aircraft flew in May 1945. Production began in 1946, and the aircraft was accepted into service in 1947.

Beginning with the P2V-5F model, the Neptune became one of the first aircraft in operational service to be fitted with both piston and jet engines. The Convair B-36, several Boeing C-97 Stratofreighter, Fairchild C-123 Provider, and Avro Shackleton aircraft were also so equipped. To save the weight and complexity of two separate fuel systems, the Westinghouse J34 jet engines on the P2Vs did not burn jet fuel- they burned the same fuel as the piston engines: 115–145 Avgas. The jet pods were fitted with intake doors that were kept closed when the J-34s were not running to prevent them from windmilling, allowing for economical piston-engine-only long-endurance search and patrol operations. In normal U.S. Navy operations, the jet engines were run at full power (97%) to expedite and assure all takeoffs, then shut down when the aircraft reached a safe altitude. Also, the jets were started and kept running at flight idle during low-altitude (500-foot (150 m) during the day and 1,000-foot (300 m) at night) anti-submarine and/or anti-shipping operations at sea as a safety measure in case one of the radials developed problems.

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