Lockheed P-2 Neptune

The Lockheed P-2 Neptune (designated P2V by the United States Navy prior to September 1962) is 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 was replaced in turn by the Lockheed P-3 Orion. Designed as a land-based aircraft, the Neptune never made a carrier landing, but a small number were converted and deployed as carrier-launched (using JATO assist), stop-gap nuclear bombers that would have to land on shore or ditch. 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 prototype 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. Potential use as a bomber led to successful launches from aircraft carriers.

Beginning with the P2V-5F model, the Neptune became one of the first operational aircraft fitted with both piston and jet engines. The Convair B-36, several Boeing C-97 Stratofreighter, Fairchild C-123 Provider, North American AJ Savage, and Avro Shackleton aircraft were also so equipped. To save weight and complexity of two separate fuel systems, the Westinghouse J34 jet engines on P2Vs burned the 115–145 Avgas fuel of the piston engines, instead of jet fuel. The jet pods were fitted with intake doors that remained closed when the J-34s were not running. This prevented windmilling, allowing for economical piston-engine-only long-endurance search and patrol operations. In normal US Navy operations, the jet engines were run at full power (97%) to assure takeoff, then shut down upon reaching a safe altitude. The jets were also 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 as a safety measure should one of the radials develop problems.

Normal crew access was via a ladder on the aft bulkhead of the nosewheel well to a hatch on the left side of the wheel well, then forward to the observer nose, or up through another hatch to the main deck. There was also a hatch in the floor of the aft fuselage, near the sonobuoy chutes.

Before the P-3 Orion arrived in the mid-1960s, the Neptune was the primary U.S. land-based anti-submarine patrol aircraft, intended to be operated as the hunter of a '"Hunter-Killer" group, with destroyers employed as killers. Several features aided the P-2 in its hunter role:

As the P-2 was replaced in the US Navy by the P-3A Orion in active Fleet squadrons in the early and mid-1960s, the P-2 continued to remain operational in the Naval Air Reserve through the mid-1970s, primarily in its SP-2H version. As active Fleet squadrons transitioned to the P-3B and P-3C in the mid- and late-1960s and early 1970s, the Naval Air Reserve P-2s were eventually replaced by P-3As and P-3Bs and the P-2 exited active U.S. naval service. VP-23 was the last active duty patrol squadron to operate the SP-2H, retiring its last Neptune on 20 February 1970, while the last Naval Reserve patrol squadron to operate the Neptune, VP-94, retired its last SP-2H in 1978.

At the end of World War II, the US Navy felt the need to acquire a nuclear strike capability to maintain its political influence. In the short term, carrier-based aircraft were the best solution. The large Fat Man nuclear munitions at that time were bulky and required a very large aircraft to carry them. The US Navy Bureau of Ordnance built 25 outdated but more compact Little Boy nuclear bombs to be used in the smaller bomb bay of the P2V Neptune. There was enough fissionable material available by 1948 to build ten complete uranium projectiles and targets, although there were only enough initiators to complete six. The U.S. Navy improvised a carrier-based nuclear strike aircraft by modifying the P2V Neptune for carrier takeoff using jet assisted takeoff (JATO) rocket boosters, with initial takeoff tests in 1948. However, the Neptune could not land on a carrier, therefore the crew had to either make their way to a friendly land base after a strike, or ditch in the sea near a U.S. Navy vessel. It was replaced in this emergency role by the North American AJ Savage (transferred to the Pacific Fleet in October 1952) the first nuclear strike aircraft that was fully capable of carrier launch and recovery operations; it was also short-lived in that role as the US Navy was adopting fully jet powered nuclear strike aircraft.

In 1954, under Project Cherry, the US Central Intelligence Agency (CIA) obtained five, newly built P2V-7 and converted them into P2V-7U/RB-69A variants by Lockheed's Skunk Works at Hangar B5 in Burbank, California for the CIA's own private fleet of covert ELINT/ferret aircraft. Later, to make up for P2V-7U/RB-69A operational losses, the CIA obtained and converted two existing US Navy P2V-7s, one in September 1962 and one in December 1964, to P2V-7U/RB-69A Phase VI standard, and they also acquired an older P2V-5 from the US Navy as a training aircraft in 1963. Test flights were made by lead aircraft at Edwards AFB from 1955 to 1956 with all the aircraft painted with a dark sea blue color but with USAF markings. In 1957, one P2V-7U was sent to Eglin AFB for testing aircraft performance at low level and under adverse conditions.^{[citation needed]}