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Amaritime patrol aircraft (MPA), also known as apatrol aircraft,maritimereconnaissance aircraft,maritime surveillance aircraft, or by the older American termpatrol bomber, is afixed-wing aircraft designed to operate for long durations over water inmaritime patrol roles — in particularanti-submarine warfare (ASW),anti-ship warfare (AShW), andsearch and rescue (SAR).
Among other maritime surveillance resources, such assatellites, ships,unmanned aerial vehicles (UAVs) andhelicopters, the MPA is an important asset.[1] To perform ASW operations, MPAs typically carry air-deployablesonar buoys as well astorpedoes and are usually capable of extended flight at low altitudes.[2]
The first aircraft that would now be identified as maritime patrol aircraft were flown by theRoyal Naval Air Service and the FrenchAéronautique Maritime during theFirst World War, primarily on anti-submarine patrols. France, Italy and Austria-Hungary used large numbers of smaller patrol aircraft for theMediterranean,Adriatic and other coastal areas while the Germans and British fought over the North Sea. At first,blimps andzeppelins were the only aircraft capable of staying aloft for the longer ten hour patrols whilst carrying a useful payload while shorter-range patrols were mounted with landplanes such as theSopwith 1½ Strutter.[3] A number of specialized patrol balloons were built, particularly by the British, including theSS class airship of which 158 were built including subtypes.[4][5]
As the conflict continued, numerous aircraft were developed specifically for the role, including small flying boats such as theFBA Type C,[6] as well as largefloatplanes such as theShort 184,[7] orflying boats such as theFelixstowe F.3.[8] Developments of the Felixstowe served with theRoyal Air Force until the mid 20s, and with theUS Navy as theCurtiss F5L andNaval Aircraft Factory PN whose developments saw service until 1938.[9] During the war,Dornier did considerable pioneering work in all aluminium aircraft structures while working forLuftschiffbau Zeppelin and built four large patrol flying boats, the last of which, theZeppelin-Lindau Rs.IV,[10] influenced development elsewhere resulting in the replacement of wooden hulls with metal ones, such as on theShort Singapore.[11] The success of long range patrol aircraft led to the development of fighters specifically designed to intercept them, such as theHansa-Brandenburg W.29.[12]
Many of theSecond World War patrol airplanes were converted from eitherbombers orairliners, such as theLockheed Hudson which started out as theLockheed Model 14 Super Electra,[13][14] as well as older biplane designs such as theSupermarine Stranraer, which had begun to be replaced by monoplanes just before the outbreak of war.[15] The British in particular used obsolete bombers to supplement purpose-built aircraft for maritime patrol, such as theVickers Wellington andArmstrong-Whitworth Whitley,[16][17] while the US relegated theDouglas B-18 Bolo to the same role until better aircraft became available.[18] Blimps were widely used by theUnited States Navy, especially in the warmer and calmer latitudes of theCaribbean Sea,the Bahamas,Bermuda, theGulf of Mexico,Puerto Rico,Trinidad, and laterthe Azores.[19][20]
A number of special-purpose aircraft were also used in the conflict, including the American-made twin-engineConsolidated PBY Catalina flying boats,[21][22] and the large, four-engine BritishShort Sunderland flying boats of theAllies.[23][24] In thePacific theatre, the Catalina was gradually superseded by the longer-rangedMartin PBM Mariner flying boat.[25] For theAxis Powers, there were the long-range JapaneseKawanishi H6K andKawanishi H8K flying boats,[26][27] and the GermanBlohm & Voss BV 138diesel-engined trimotor flying boat,[28] as well as the convertedFocke-Wulf Fw 200 Condor airliner landplane.[29][30]
To finally close theMid-Atlantic gap, or "Black Gap", a space in which Axis submarines could prey on Allied shipping out of reach of MPAs, the BritishRoyal Air Force, theRoyal Canadian Air Force, and theUS Army Air Forces introduced the AmericanConsolidated B-24 Liberatorbomber, which had a very longrange for the era.[31][32] The B-24 was also used at the basis for thePB4Y-2 Privateer, a dedicated MPA variant adopted in large numbers by the US Navy, which saw service late on in the Pacific theatre.[33][34]
During the conflict, there were several developments inair-to-surface-vessel radar andsonobuoys, which enhanced the ability of aircraft to find and destroy submarines, especially at night and in poor weather.[35][36][37][38] Another area of advancement was the adoption of increasingly effectivecamouflage schemes, which led to the widespread adoption of white paint schemes in the Atlantic to reduce the warning available to surfacedU-boats,[39] while US Navy aircraft transitioned from an upper light blue-gray and lower white to an all-over dark blue due to the increasing threat of Japanese forces at night-time.[citation needed]
In the decades following the Second World War, the MPA missions were partially taken over by aircraft derived from civilian airliners. These had range and performance factors better than most of the wartime bombers. The latest jet-powered bombers of the 1950s did not have the endurance needed for long, overwater patrolling, and they did not have the low loitering speeds necessary for antisubmarine operations. The main threat to NATO maritime supremacy throughout the 1960s, 1970s, and the 1980s wasSoviet Navy andWarsaw Pact submarines. These were countered by the NATO fleets, the NATO patrol planes mentioned above, and by sophisticated underwater listening systems. These span the so-called "GIUK Gap" of the North Atlantic that extends from Greenland to Iceland, to theFaroe Islands, to Scotland in theUnited Kingdom. Air bases for NATO patrol planes have also been located in these areas: U.S. Navy and Canadian aircraft based in Greenland, Iceland, and Newfoundland; British aircraft based in Scotland andNorthern Ireland; and Norwegian, Dutch, and German aircraft based in their home countries.
During the late 1940s, the RAF introduced theAvro Shackleton – a specialised MPA derivative of theAvro Lancaster bomber – in anticipation of a rapid expansion of theSoviet Navy's submarine force.[40][41] An improved model of the Shackleton, theMR 3, was introduced, featuring various structural improvements,[42] along with homing torpedoes andMk 101 Lulu nuclear depth bombs.[43] During the late 1960s, a jet-powered replacement in the form of theHawker Siddeley Nimrod, a derivation of theDe Havilland Comet airliner, begun to be introduced.[44][45] During the 2000s, an improved model, theBAE Systems Nimrod MRA4, was in development, but was cancelled and eventually substituted for by theBoeing P-8 Poseidon.[46][47]
The U.S. Navy flew a mixture of MPAs, including the land-basedLockheed P2V Neptune (P2V) and thecarrier-basedGrumman S-2 Tracker.[48][49] During the 1970s, the P2V was entirely replaced by theLockheed P-3 Orion, which remained in service into the early twenty-first century.[50][51]
The P-3, powered by fourturboprop engines, is derived from the 1950s eraLockheed Electra airliner. In addition to their ASW and SAR capabilities, most P-3Cs have been modified to carryHarpoon andMaverick missiles for attacking surface ships. American P-3s were formerly armed with theLulu nucleardepth charge for ASW, but those were removed from the arsenal and scrapped decades ago.[52] Produced inUnited States,Japan andCanada, the P-3 has been operated by the air forces and navies of United States, Japan, Canada, Australia, Iran, Brazil, Germany, the Netherlands,New Zealand,Norway, Spain, and Taiwan. The Canadian version is called theCP-140 Aurora.[53][54]
During the 1960s, in response toNorth Atlantic Treaty Organization (NATO) issuing aRequest for Proposals (RFP) for a new MPA, theBreguet 1150 Atlantic was developed by a French-led multinational consortium,Société d'Étude et de Construction de Breguet Atlantic (SECBAT).[55] Operators of the type include theFrench Navy, theGerman Navy, theItalian Air Force, thePakistan Navy, and theRoyal Netherlands Navy. During the 1980s, an updated version, theAtlantic Nouvelle Génération orAtlantique 2, with new equipment and avionics was introduced, which included a new radar, sonar processor,forward-looking infrared camera turret, and the ability to carry theExocet anti-shipping missile.[56][57] By 2005, French manufacturerDassault Aviation had decided to terminate marketing efforts for the Atlantic, promoting a MPA variant of theDassault Falcon 900 corporate jet instead.[58]
Japan has developed multiple purpose-designed MPAs during this period. TheShin Meiwa PS-1 flying boat was designed to meet a Japanese requirement for a new ASW platform. A modernised derivative of the PS-1, theShinMaywa US-2 amphibian, was introduced during the early twenty-first century to succeed the PS-1.[59][60] The land-basedKawasaki P-1 was introduced during the 2010s by theJapan Maritime Self-Defense Force (JMSDF) as a replacement for the agingP-3C Orion.[61][62]
Both theRoyal Australian Air Force and theRoyal Australian Navy met their early postwar MPA needs via a stretched-fuselage modification of theAvro Lincoln bomber. However, the type was soon supplemented and eventually replaced by new aircraft, such as the P2V and later the P-3C, which later became the sole ASW type operated by the service.
TheSoviet Union developed theIlyushin Il-38 from a civilian airliner. Similarly, theRoyal Canadian Air Force derived theCanadair CP-107 Argus from a British airliner, theBristol Britannia. The Argus was superseded by the CP-140 Aurora, derived from the Lockheed Electra.
Since the end of theCold War, the threat of a large-scale submarine attack is a remote one, and many of the air forces and navies have been downsizing their fleets of patrol planes. Those still in service are still used for search-and-rescue, counter-smuggling, antipiracy, antipoaching of marine life, the enforcement of theexclusive economic zones, and enforcement of thelaws of the seas.
The earliest patrol aircraft carried bombs and machine guns. Between the wars the British experimented with equipping their patrol aircraft with theCOW 37 mm gun. During World War II,depth charges that could be set to detonate at specific depths, and later when in proximity with large metal objects replaced anti-submarine bombs that detonated on contact. Patrol aircraft also carried defensive armament which was necessary when patrolling areas close to enemy territory such as Allied operations in theBay of Biscay targetingU-boats starting out from their base.
As a result of Allied successes with patrol aircraft against U-boats, the Germans introducedU-flak (submarines equipped with more antiaircraft weaponry) to escort U-boats out of base and encouraged commanders to remain on the surface and fire back at attacking craft rather than trying to escape by diving. However, U-flak was short-lived, as opposing pilots adapted their tactics. Equipping submarines withradar warning receivers and thesnorkel made them harder to find.
To counter the German long-range patrol aircraft that targeted merchant convoys, theRoyal Navy introduced the "CAM ship", which was a merchant vessel equipped with a lonefighter plane which could be launched once to engage the enemy planes. Later, the smallescort carriers of WWII became available to cover the deep oceans, and the land air bases inthe Azores became available in mid-1943 fromPortugal.
As technology progressed the bombs and depth charges were supplemented withAcoustic torpedoes that could detect, follow and then explode against an enemy submarine. The US Navy began fielding theMark 24 mine in 1943, labelled as a mine as a security measure. It sank 37 Axis submarines during the war.
The Cold War era saw the introduction of thenuclear depth bomb, a depth charge with anuclear warhead that raised the probability of a kill against a submarine to a near-certainty as long as detonation occurred.
While anti-submarine warfare is the main role of patrol aircraft, their large payload capability has seen them fitted for various weaponry outside their nominal role. TheLockheed P-3 Orion was fitted with underwing pylons that could carry a variety of common American weapons, including theAGM-84 Harpoon anti-ship missile, the air-to-groundAGM-65 Maverick, as many as ten of theCBU-100 Cluster Bomb, rocket pods, sea mines, and the standard issueMark 80 general purpose bombs.
TheRoyal Air Force'sHawker Siddeley Nimrod was fitted withAIM-9 Sidewinder missiles in 1982 during theFalklands War in order for it to be able to attack anyArgentine Air Force patrol planes they might encounter.
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Maritime patrol aircraft are typically fitted with a wide range of sensors:[63]
A modern military maritime patrol aircraft typically carries a dozen or so crew members, including relief flight crews, to effectively operate the equipment for 12 hours or more at a time.[citation needed]
The first air attack using a torpedo dropped by an aeroplane was carried out by Flight Commander Charles H. K. Edmonds, flying a Short 184 seaplane fromBen-my-Chree on 12 August 1915, against a 5,000 ton Turkish supply ship in theSea of Marmara. Although the enemy ship was hit and sunk, the captain of a British submarine claimed to have fired a torpedo simultaneously and sunk the ship. It was further stated that the British submarine E14 had attacked and immobilised the ship four days earlier.
white has proved to be the most efficient concealing coloration for aircraft on anti-submarine patrol