Country of origin | United States |
---|---|
Manufacturer | General Electric Hazeltine |
Introduced | 1945 |
Type | Airborne early warning, maritime patrol, weather research |
Frequency | S Band (APS/AN-20A), plus L and X Band (AN/APS-20E) |
PRF | 300 Hz |
Beamwidth | 1.5° (horizontal), 6° (vertical) |
Pulsewidth | 2 μs |
RPM | 3 or 6 |
Range | 200 nmi (370 km; 230 mi) against surface ships, 65 nmi (120 km; 75 mi) (APS/AN-20B) |
Diameter | 8 ft (2.4 m) (APS/AN-20A) |
Power | 1 MW (APS/AN-20A) |
The AN/APS-20 was an airborne early warning, anti-submarine, maritime surveillance and weather radar developed in the United States in the 1940s. Entering service in 1945, it served for nearly half a century, finally being retired in 1991. Initially developed at Massachusetts Institute of Technology (MIT) under Project Cadillac, the radar was developed to be carried by aircraft to extend the sensor range of ships by placing a radar at altitude. Although developed for carrier-borne operation, first being installed in the single-engined General Motors TBM-3W Avenger, it was also used in larger four-engined airframes, the last being a fleet of Avro Shackleton AEW.2 which were converted from maritime patrol aircraft. Similarly, although developed for detecting aircraft, it saw extensive service in anti-submarine and maritime patrol roles and was one of the first radars to be used in researching extreme weather like hurricanes by agencies like the Environmental Science Services Administration (ESSA). As well as the United States, the radar was used by a large number of services in other countries, including the French Navy, Japan Maritime Self-Defense Force (JMSDF), Royal Air Force (RAF) and Royal Canadian Air Force (RCAF). Early versions of the radar could see a low-flying aircraft at 65 nautical miles (120 km ; 75 mi ) and a ship at 200 nautical miles (370 km; 230 mi). This was improved, so that later versions had a range against aerial targets of 115 nautical miles (213 km; 132 mi).
From the early days of its development, radar had been used to detect aircraft. Early apparatus was large and required substantial power, and so was limited to fixed locations and ships. However, during World War II, increasingly smaller radar sets were developed that could be more installed in smaller platforms like aircraft. [1] At the same time, the United States Navy (USN) was aware that attacks from the aircraft of the Imperial Japanese Navy were the largest threat to their warships and protecting these ships became more dependent on aircraft carriers and their squadrons. Shipborne radar did not have sufficient range to identify attacking bombers in time to launch defensive interceptor aircraft due to the radar horizon. The solution lay in placing a radar in an aircraft. [2] Night fighter radars proved inadequate for the task. Optimised for aerial combat, they were too short ranged to fulfil the necessary long-range aerial surveillance role. [3]
The solution to the problem of detecting objects beyond the horizon lay in developing a dedicated airborne early warning radar. On 2 February 1942, the USN commissioned the Radiation Laboratory at the Massachusetts Institute of Technology (MIT) to explore an airborne radar design dedicated to seeking aircraft under Project Cadillac, named after the Cadillac Mountain in Maine. [4] The team grew rapidly from 37, including 10 officers, in May 1943 to 138 at the end of the War. [5] The outcome of the development was an S-Band radar designated AN/APS-20. [3] Development continued in two guises. Cadillac I, the initial platform, was to be carrier-based and the first radar was to be fitted to converted General Motors TBM-3 Avenger torpedo bombers. [6] Simultaneously, the need for a version for larger land-based aircraft was recognised. Under the guise of Cadillac II, it was decided that the Boeing B-17G Flying Fortress heavy bomber was to be fitted with the radar. [7]
The production radar was manufactured by General Electric and Hazeltine. [8] The first version, the AN/APS-20A, had, initially, an 8- foot -4- inch (2.54 m ) antenna and operated on a frequency of 2850 MHz in the S band. [3] Later a slightly smaller 8 ft (2.4 m) antenna was used. [8] The scanner had two speeds, 3 and 6 revolutions per minute. The radar worked at a Pulse Repetition Frequency (PRF) of 300 Hz, a pulse length of 2 μm (7.9×10−5 in). Peak power was 1 megawatt (1,300 hp ). [9] The AN/APS-20B, designed to be carried by larger aircraft, differed in size and capability. It had a peak power of 2 MW (2,700 hp) and a horizontal beam width of 1.5° and vertical of 6°. Pulse width remained 2 μs. [10] Range was extended to 65 nautical miles (120 km ; 75 mi ) against low flying aircraft and 200 nautical miles (370 km; 230 mi) against shipping. [11]
Later versions expanded the capability. The AN/APS-20F extended the range against aircraft to 80 nautical miles (150 km; 92 mi), while the larger AN/APS-20E could detect an aerial 1 m2 (11 sq ft) target at 115 nautical miles (213 km; 132 mi). [12] Initially deployed in 1953, the E model operated in the L band, S band and X band, with a wide selection of PRFs and pulse widths in each band. It also included automatic target indication, three choices of heading reference and stabilization, selectable azimuth and elevation beam widths, selectable output and receiver radiated gain and automatic gain control amongst other features. [13]
The first aircraft equipped with the AN/APS-20 was a converted TBM-3 Avenger, designated XTBM-3W, which first flew on 5 August 1944. [5] The radar was mounted in a radome under the forward fuselage. A series of aircraft were converted from existing TBM-3 airframes by the Naval Aircraft Modification Unit and designated TBM-3W, with initial training aboard the aircraft carrier Ranger starting in May 1945. [14] At the same time, 31 large Boeing PB-1W aircraft were converted from B-17G Flying Fortresses to become the first land-based aircraft equipped with the radar. They were especially designed to combat the increasing threat of Japanese Kamikaze attacks. [7] The crew of the Avenger consisted of, as well as the pilot, a single Radar Operator (RO). The larger size of the PB-1W allowed for two ROs, an Electronics Technician and, critically, a Combat Information Center (CIC) Officer supported by two radio operators. The latter team was able to direct aircraft to the target, adding the ability of the aircraft to control fighter aircraft and enabling operation independent of shipboard or ground-based control. This capability was later developed into the Airborne Warning and Control System (AWACS). The war ended before either aircraft became operational. [15]
Post-war, the USN quickly accelerated a program to get the radar into service. The AN/APS-20 was installed in the Douglas AD-3W Skyraider, which replaced the Avenger, and the Lockheed PO-2W Warning Star, a specialised platform developed from the Lockheed L-1049 Super Constellation airliner. [16] Both also saw service outside the USN. The latter, which could carry up to 32 servicemen for long trips, so impressed the newly formed United States Air Force (USAF) that it ordered it into service as the EC-121 Warning Star. Following a test between 24 February and 23 March 1953, the USAF used their aircraft to mount a near-continuous monitor of potential incursion by the Soviet Air Forces of American continental airspace. [17] At the same time, the Royal Navy procured fifty examples of the AD-3W as the Skyraider AEW.1. This was the first use of the radar the a non-US operator. [18] Meanwhile, in an attempt to extend endurance, in 1954 the USN ordered the installation of the radar in a blimp, the ZP2N-1W, later redesigned ZPG-2W and then, in 1962, EZ-1B. [19] The last example retired in October 1962, not only ending the use of the radar in airships but also all lighter than air operations by the service. [20]
Alongside these developments, new uses of the radar were explored. One arena where the radar broke new ground was in weather research, particularly with the hurricane hunters that flew into tropical cyclones. The first trials of the radar took place in 1946 with a PB-1W and on 15 September 1953 the newly created weather squadron VJ2 flew the first aircraft equipped with an APS/AN-20 into a hurricane, Hurricane Dolly. [21] Equipped with the dedicated WV-3 Warning Star from 1956, the squadron frequently flew up to three times a week on tropical cyclone observation. [22] At the same time, VW-1 was providing a similar service tracking typhoons in the Pacific. [23] Other users of the radar included the Environmental Science Services Administration (ESSA) and its successor the National Oceanic and Atmospheric Administration (NOAA). [24] Aircraft operated by these agencies were also made available to universities, and therefore the radar was also used as a tool for academic research where its attributes proved invaluable in the study of precipitation. [25] It was used in a wide range of airframes, including converted Douglas DC-6 airliners and the dedicated Lockheed WP-3A Orion which served into the 1970s. [26] [27]
Meanwhile, in 1948, the UK evaluated a PB-1W equipped with AN/APS-20 against a Vickers Warwick V fitted with ASV.13 to see if the radar could also be used to identify surface ships, but the peak power was deemed too high and the pulse length too long for the application. [9] Nonetheless, the Royal Canadian Air Force (RCAF) used the radar in their maritime surveillance Canadair Argus Mk.1. [28] The USN also looked to mount the radar on its carrier-borne anti-submarine aircraft, commissioning Grumman to use it in the design which eventually became the Grumman S2F Tracker. [29] Of greater impact, however, was the improved AN/APS-20E subsequently used in the role in the Lockheed P2V Neptune. The radar first flew in the third airframe, designated P2V-2S, which was the first developed for the anti-submarine role. [30] It proved effective at identifying large surface ships up to 200 nautical miles (370 km; 230 mi) away but was ineffectual when tracking periscopes. [31] Subsequently, the airframe was adopted by a range of operators, from the Argentine Navy to the Republic of China Air Force. [32]
The AN/APS-20 was also briefly used as part of the Space Race, supporting Project Mercury, where the radar's long range enabled it to be used in tracking and other tasks. [22] It was particularly used to help find returning space capsules after splashdown. For example, the radar was installed aboard aircraft of VP-5 that were involved in the recovery of Commander Alan Shepard from Mercury-Redstone 3, Captain Gus Grissom from Mercury-Redstone 4 and Commander Wally Schirra from Mercury-Atlas 8. [33]
Replacement of the radar took many decades. The USAF trialled the more advanced AN/APS-82, which provided target height data, in 1956 but waited until after 1962 before replacing the radar with the AN/APS-95 aboard their Warning Stars. [34] In the meantime, the USN introduced the AN/APS-82 on board carriers in the airborne early warning role in 1959. [35] The AN/APS-80, which offered similar capabilities to the AN/APS-20 but added continuous 360° area search coverage, replaced the radar in the anti-submarine role from 1961. [31] The Canadians finally replaced their AN/APS-20 with AN/APS-115 in 1981. [36] The last operator of the radar was the Royal Air Force (RAF), which had previously used it between 1952 and 1957. [37] When the Royal Navy retired their last AN/APS-20, they were refurbished and fitted to retiring Avro Shackleton MR.2 maritime patrol aircraft. Re-entering service in 1972 with the RAF with the designation AEW.2, the aircraft continued to operate until July 1991 in the airborne early warning role. [38]
The Lockheed S-3 Viking is a four-crew, twin-engine turbofan-powered jet aircraft designed and produced by the American aerospace manufacturer Lockheed Corporation. Because of its characteristic sound, it was nicknamed the "War Hoover" after the vacuum cleaner brand.
The Hawker Siddeley Nimrod is a retired maritime patrol aircraft developed and operated by the United Kingdom. It was an extensive modification of the de Havilland Comet, the world's first operational jet airliner. It was originally designed by de Havilland's successor firm, Hawker Siddeley; further development and maintenance work was undertaken by Hawker Siddeley's own successor companies, British Aerospace and, later, BAE Systems.
The Northrop Grumman E-2 Hawkeye is an American all-weather, carrier-capable tactical airborne early warning (AEW) aircraft. This twin-turboprop aircraft was designed and developed during the late 1950s and early 1960s by the Grumman Aircraft Company for the United States Navy as a replacement for the earlier, piston-engined E-1 Tracer, which was rapidly becoming obsolete. The aircraft's performance has been upgraded with the E-2B and E-2C versions, where most of the changes were made to the radar and radio communications due to advances in electronic integrated circuits and other electronics. The fourth major version of the Hawkeye is the E-2D, which first flew in 2007. The E-2 was the first aircraft designed specifically for its role, as opposed to a modification of an existing airframe, such as the Boeing E-3 Sentry. Variants of the Hawkeye have been in continuous production since 1960, giving it the longest production run of any carrier-based aircraft.
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.
The Douglas A-1 Skyraider is an American single-seat attack aircraft in service from 1946 to the early 1980s, which served during the Korean War and Vietnam War. The Skyraider had an unusually long career, remaining in front-line service well into the Jet Age ; thus becoming known by some as an "anachronism". The aircraft was nicknamed "Spad", after the French World War I fighter.
The Grumman S-2 Tracker was the first purpose-built, single airframe anti-submarine warfare (ASW) aircraft to enter service with the United States Navy. Designed and initially built by Grumman, the Tracker was of conventional design — propeller-driven with twin radial engines, a high wing that could be folded for storage on aircraft carriers, and tricycle undercarriage. The type was exported to a number of navies around the world. Introduced in 1952, the Tracker and its E-1 Tracer derivative saw service in the U.S. Navy until the mid-1970s, and its C-1 Trader derivative until the mid-1980s, with a few aircraft remaining in service with other air arms into the 21st century. Argentina and Brazil are the last countries to still use the Tracker.
An airborne early warning and control (AEW&C) system is an airborne radar system designed to detect aircraft, ships, vehicles, missiles, and other incoming projectiles at long ranges and perform command and control of the battlespace in an air engagement by directing fighter and attack aircraft strikes. AEW&C units are also used to carry out surveillance, including over ground targets and frequently perform battle management command and control (BMC2). When used at altitude, the radar on the aircraft allows the operators to detect and track targets and distinguish between friendly and hostile aircraft much farther away than a similar ground-based radar. Like a ground-based radar, it can be detected by opposing forces, but because of its mobility and extended sensor range, it is much less vulnerable to counter-attacks.
A maritime patrol aircraft (MPA), also known as a patrol aircraft, maritime reconnaissance aircraft, maritime surveillance aircraft, or by the older American term patrol bomber, is a fixed-wing aircraft designed to operate for long durations over water in maritime patrol roles — in particular anti-submarine warfare (ASW), anti-ship warfare (AShW), and search and rescue (SAR).
The Lockheed P-2 Neptune 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, 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.
The Grumman TBF Avenger is an American World War II-era torpedo bomber developed initially for the United States Navy and Marine Corps, and eventually used by several air and naval aviation services around the world.
The Lockheed EC-121 Warning Star was an American airborne early warning and control radar surveillance aircraft operational in the 1950s in both the United States Navy (USN) and United States Air Force (USAF).
The N-Class, or as popularly known, the "Nan ship", was a line of non-rigid airships built by the Goodyear Aircraft Company of Akron, Ohio for the US Navy. This line of airships was developed through many versions and assigned various designators as the airship designation system changed in the post World War II era. These versions included airships configured for both anti-submarine warfare and airborne early warning (AEW) missions.
A radar picket is a radar-equipped station, ship, submarine, aircraft, or vehicle used to increase the radar detection range around a nation or military force to protect it from surprise attack, typically air attack, or from criminal activities such as smuggling. By definition a radar picket must be some distance removed from the anticipated targets to be capable of providing early warning. Often several detached radar units would be placed in a ring to encircle a target to provide increased cover in all directions; another approach is to position units to form a barrier line.
The British Aerospace Nimrod AEW3 was a proposed airborne early warning (AEW) aircraft which was to provide airborne radar cover for the air defence of the United Kingdom by the Royal Air Force (RAF). The project was designed to use the existing Nimrod airframe, in use with the RAF as a maritime patrol aircraft, combined with a new radar system and avionics package developed by Marconi Avionics.
The Fairey Gannet AEW.3 is a variant of the Fairey Gannet anti-submarine warfare aircraft intended to be used in the airborne early warning (AEW) role on aircraft carriers of the Royal Navy. It was introduced to service in 1959 to replace the obsolete Douglas Skyraider, and was intended as an interim solution until the planned introduction of a new, purpose built AEW platform for use on the planned CVA-01 aircraft carriers. Neither the new aircraft carriers nor the new AEW aircraft were proceeded with, and the Gannet AEW.3 remained in service until the last aircraft carrier that could operate it was retired in 1978.
The Hawker Siddeley P.139B was a proposed airborne early warning aircraft intended to operate from aircraft carriers of the Royal Navy. The P.139B formed part of the a major equipment procurement plan for the RN in the 1960s intended to give the service a force of new, modern carriers capable of operating air groups consisting of equally modern aircraft. However, cuts in defence spending by the British government in the mid-1960s meant that these proposals never came to fruition.
{{cite journal}}
: CS1 maint: date and year (link){{cite journal}}
: CS1 maint: date and year (link){{cite journal}}
: CS1 maint: date and year (link)