P-3 Orion

### Operators

Argentina, Australia, Brazil, Chile, Canada, Germany, Greece, Iran, Japan, Pakistan, Portugal, South Korea, Taiwan, USA (Current), Netherlands, New Zealand, Norway, Spain, Thailand (former)

### Status

Active

The **Lockheed P-3 Orion** is a four-engined, turboprop anti-submarine and maritime surveillance aircraft developed for the United States Navy and introduced in the 1960s. Lockheed based it on the L-188 Electra commercial airliner; it is easily distinguished from the Electra by its distinctive tail stinger or "MAD" boom, used for the magnetic anomaly detection (MAD) of submarines.

Over the years, the P-3 has seen numerous design developments, most notably in its electronics packages. Numerous navies and air forces around the world continue to use the type primarily for maritime patrol, reconnaissance, anti-surface warfare and anti-submarine warfare. A total of 757 P-3s have been built. In 2012, it joined the handful of military aircraft including the Boeing B-52 Stratofortress, Boeing KC-135 Stratotanker, Lockheed C-130 Hercules and the Lockheed U-2 that the United States military has been using for more than 50 years. In the twenty-first century, the turbofan-powered Boeing P-8 Poseidon began to supplement, and will eventually replace, the U.S. Navy's P-3s.

### Design

In August 1957, the U.S. Navy called for proposals for replacement of the piston-engined Lockheed P2V Neptune (later redesignated P-2) and Martin P5M Marlin (later redesignated P-5) with a more advanced aircraft to conduct maritime patrol and antisubmarine warfare. Modifying an existing aircraft should save on cost and to allow rapid introduction into the fleet. Lockheed suggested a military version of its L-188 Electra, then still in development and yet to fly. In April 1958, Lockheed won the competition and was awarded an initial research-and-development contract in May.

Lockheed modified the prototype YP3V-1/YP-3A, Bureau Number (BuNo) 148276 from the third Electra airframe c/n 1003. The first flight of the aircraft's aerodynamic prototype, originally designated YP3V-1, took place on 19 August 1958. While based on the same design philosophy as the Electra, the aircraft differed structurally; it had 7 feet (2.1 m) less fuselage forward of the wings with an opening bomb bay, and a more pointed nose radome, a distinctive tail "stinger" for detection of submarines by MAD, wing hardpoints, and other internal, external, and airframe-production technique enhancements.

The Orion has four Allison T56 turboprops, which give it a top speed of 411 knots (761 km/h; 473 mph) comparable to the fastest propeller fighters, or even to slow high-bypass turbofan jets such as the Fairchild Republic A-10 Thunderbolt II or the Lockheed S-3 Viking. Similar patrol aircraft include the Soviet Ilyushin Il-38, the French Breguet Atlantique and the British jet-powered Hawker Siddeley Nimrod (based on the de Havilland Comet).

The first production version, designated P3V-1, was launched on 15 April 1961. Initial squadron deliveries to Patrol Squadron Eight (VP-8) and Patrol Squadron Forty-Four (VP-44) at Naval Air Station Patuxent River, Maryland, began in August 1962. On 18 September 1962, the U.S. military transitioned to a unified designation system for all services, with the aircraft being renamed the P-3 Orion. Paint schemes have changed from early 1960s, gloss seaplane gray and white to mid-1960s/1970s/1980s/early 1990s gloss white and gray, to mid-1990s flat-finish low-visibility gray with fewer and smaller markings. In the early 2000s, the paint scheme changed to its current overall gloss gray finish with the original full-sized color markings. However, large-sized BuNos on the vertical stabilizer and squadron designations on the fuselage remained largely omitted.

In 1963, the U.S. Navy's Bureau of Naval Weapons contracted Univac Defense Systems Division of Sperry Rand to engineer, build, and test a digital computer (a device then in its infancy) to interface with the many sensors and newly developing display units of the P-3 Orion. Project A-NEW was the engineering system, which after several early trials, produced the engineering prototype, the CP-823/U, Univac 1830, Serial A-1, A-NEW MOD3 Computing System. Univac delivered the CP-823/U to the Naval Air Development Center at Johnsville, Pennsylvania, in 1965; this directly led to the production computers later equipped on the P-3C.
Three civilian Electras were lost in fatal accidents between February 1959 and March 1960. Following the third crash, the FAA restricted the maximum speed of Electras pending determination of the causes. After an extensive investigation, two of the crashes (those of September 1959 and March 1960) were identified as due to insufficiently strong engine mounts, unable to damp a whirling motion that could affect the outboard engines. When the oscillation was transmitted to the wings, a severe vertical vibration escalated, tearing off the wings. The company implemented an costly modification program, labelled the Lockheed Electra Achievement Program, which strengthened the engine mounts and the wing structures supporting the mounts, and replaced some wing skins with thicker material. At its own expense, Lockheed modified all surviving Electras of the 145 built at that time, the process taking 20 days for each aircraft. These changes were incorporated into subsequent aircraft as they were built.
The Electra's sales were limited as Lockheed's technical fix did not completely erase the aircraft's poor reputation in an era in which turboprop-powered aircraft were being replaced by faster jets. In military roles that valued fuel efficiency more than speed, the Orion remained in service for over 50 years after its 1962 introduction. Although surpassed in production longevity by the Lockheed C-130 Hercules, 734 P-3s were produced through 1990. Lockheed Martin opened a new P-3 wing production-line in 2008 as part of its Service Life Extension Program (ASLEP) for delivery in 2010. A complete ASLEP replaces the outer wings, center-wing lower section, and horizontal stabilizers with newly built parts.
In the 1990s, the U.S. Navy attempted to procure a successor aircraft to the P-3, and selected the improved P-7 over a naval-specific variant of the twin turbofan-powered Boeing 757, but this program was subsequently cancelled. In a second program to select a replacement, the advanced Lockheed Martin Orion 21, another P-3-derived aircraft, lost out to the Boeing P-8 Poseidon, a Boeing 737 variant, which entered service in 2013.

The P-3 has an internal bomb bay under the front fuselage, which can house conventional Mark 50 torpedoes or Mark 46 torpedoes and/or special (nuclear) weapons. Additional underwing stations, or pylons, can carry other armament configurations, including the AGM-84 Harpoon, AGM-84E SLAM, AGM-84H/K SLAM-ER, AGM-65 Maverick, 127 millimetres (5.0 in) Zuni rockets, and various other sea mines, missiles, and gravity bombs. The aircraft also had the capability to carry the AGM-12 Bullpup guided missile until that weapon was withdrawn from U.S./NATO/Allied service.
The P-3 is equipped with a MAD in the extended tail. This instrument is able to detect the magnetic anomaly of a submarine in the Earth's magnetic field. The limited range of this instrument requires the aircraft to be near the submarine at low altitude. Because of this, it is primarily used for pinpointing the location of a submarine immediately prior to a torpedo or depth bomb attack. Due to the sensitivity of the detector, electromagnetic noise can interfere with it, so the detector is placed in P-3's fiberglass tail stinger (MAD boom), far from other electronics and ferrous metals on the aircraft.