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443:(AEW&C, often called AWACS) aircraft. AEW&C tends to be superior in that, being airborne and being able to look down, it can see targets fairly far away at low level, as long as it can pick them out from the ground clutter. AEW&C aircraft are extremely expensive, however, and generally require aircraft to be dedicated to protecting them. A combination of both techniques is really ideal, but GCI is typically only available in the defence of one's homeland, rather than in expeditionary types of battles.
455:(RWR) electronics, thus alerting the intruders that they may be coming under attack. With GCI or AEW&C, the defending aircraft can be vectored to an interception course, perhaps sliding in on the intruder's tail position without being noticed, firing passive homing missiles and then turning away. Alternatively, they could turn their radars on at the final moment, so that they can get a radar lock and guide their missiles. This greatly increases the interceptor's chance of success and survival.
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vulnerable than many ground-based radar stations. If a single AEW&C aircraft is shot down or otherwise taken out of the picture, there will be a serious gap in air defence until another can replace it, where in the case of GCI, many radar stations would have to be taken off the air before it became a serious problem. In both cases a strike on a command center could be very serious.
314:. The pilot was tasked primarily with getting the aircraft into the air (and back), and then flying in a parking orbit until called for. When an interception mission started, the SAGE computers automatically flew the plane into range of the target, allowing the pilot to concentrate solely on operating the complex onboard radar.
87:(CH), could only be directed along angles in front of the antennas, and were unable to direct traffic once it passed behind their shore-side locations. GCI radars began to replace CH starting in 1941/42, allowing a single station to control the entire battle from early detection to directing the fighters to intercept.
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Because the Chain Home radar stations faced out to sea, once airborne intruders had crossed the
British coast they could no longer be tracked by radar; and accordingly the interception direction centres relied on visual and aural sightings of the Observer Corps for continually updated information on
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systems and merged to produce a single set of "tracks", identified by number. These tracks were then telephoned to the Group headquarters that would be responsible for dealing with that target. Group would assign fighter squadrons to the tracks, and phone the information to
Section headquarters, who
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Today the term GCI refers to the style of battle direction, but during WWII it also referred to the radars themselves. Specifically, the term was used to describe a new generation of radars that spun on their vertical axis in order to provide a complete 360 degree view of the sky around the station.
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and other radar networks to produce a picture of all of the air traffic in a particular sector's area. The information was then displayed on terminals in the building, allowing operators to pick defensive assets (fighters and missiles) to be directed onto the target simply by selecting them on the
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Either GCI or AEW&C can be used to give defending aircraft a major advantage during the actual interception by allowing them to sneak up on enemy aircraft without giving themselves away by using their own radar sets. Typically, to perform an interception by themselves beyond visual range, the
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The strengths of GCI are that it can cover far more airspace than AEW&C without costing as much and areas that otherwise would be blind-spots for AEW&C can be covered by cleverly placed radar stations. AEW&C also relies on aircraft which may require defence and a few aircraft are more
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had important GCI systems which helped them harass the opposing forces (although in both cases due to the superiority in the number of US planes the effect was eventually minimised ). GCI was important to the US and allied forces during these conflicts also, although not so much as for their
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radar, which was originally intended as a very long-range early warning system for ROTOR but demonstrated its ability to control interceptions as well. This led to the abandonment of the ROTOR network and its operation being handled at the Type 80 "Master Radar
Stations". In the 1960s the
236:. Interceptions could be arranged directly from the display, without any need to forward the information over telephone links or similar. This not only greatly eased the task of arranging the interception, but greatly reduced the required manpower as well.
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arrays, which could alert GCI to inbound hostile aircraft hours before they arrive, giving enough time to prepare and launch aircraft and set them up for an intercept either using their own radars or with the assistance of regular radar stations once the
232:. Unlike the earlier system where radar data was forwarded by telephone and plotted on a map, GCI radars combined all of these functions into a single station. The PPI was in the form of a 2D top-down display showing both the targets and the intercepting
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turned on its side in order to scan an arc in front of the station. This proved very workable, and was soon extended to covering a full 360 degrees by making minor changes to the support and bearing systems. Making a display system, the
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system was perhaps the most complex attempted, using building-filling computers linked to dozens of radars and other sensors to automate the entire task of identifying an enemy aircraft's track and directing
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project looked to computerize the system in a fashion similar to SAGE, but was years late, significantly underpowered, and never operated properly. There was some thought given to sending directions to the
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Experiments in addressing this problem started with manually directed radars being used as a sort of radio-searchlight, but this proved too difficult to use in practice. Another attempt was made by using a
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which became available in numbers at the same time. These two systems proved to be a potent combination, and interception rates doubled every month from
January 1941 until the
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introduced similar systems during the war, but most other combatants did not suffer the same threat of air attack and did not develop complex systems like these until the
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321:, which was largely an expanded and rationalized version of their wartime system and remained entirely manual in operation. This was upset by the introduction of the
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As the system became operational the success of the RAF night fighter force began to shoot up. This was further aided by the introduction of the
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terminal. Messages would then automatically be routed back out via teleprinter to the fighter airbases with interception instructions on them.
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GCI systems grew in size and sophistication during the post-war era, in response to the overwhelming threat of nuclear attack. The US'
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until late in 1943, with deliveries being relatively slow after that. Many were still under construction when the war ended in 1945.
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stations was relayed by phone to a number of operators on the ground floor of the "filter room" at
Fighter Command's headquarters at
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the location and heading of enemy aircraft formations. While this arrangement worked acceptably during the daylight raids of the
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aircraft would have to search the sky for intruders with their radars, the energy from which might be noticed by the intruder's
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Starting in 1941 the RAF began deploying production models of the GCI radar, first with expedient solutions known as the
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demonstrated that such techniques were wholly inadequate for identifying and tracking aircraft at night.
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The
Germans were quite slow to follow in terms of PPI and did not order operational versions of their
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In more recent years, GCI has been supplanted, or replaced outright, with the introduction of
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or other observational stations are linked to a command communications centre which guides
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were in direct contact with the fighters. These fighter aircraft could then be "
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interceptors in a fashion similar to SAGE, but this was never implemented.
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183:. Here the information from the radar was combined with reports from the
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against it. In some cases, SAGE sent commands directly to the aircraft's
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names and readiness status boards on the wall behind. Also shown is the
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Ground
Controlled Interception Radars in Operation Neptune/Overlord
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GCI is typically augmented with the presence of extremely large
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approach their coverage. An example of this type of system is
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The most advanced GCI system deployed to date was the US's
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The restored
Operations Room in the underground bunker at
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Today, GCI is still important for most nations, although
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to an airborne target. This tactic was pioneered during
228:, and then permanent stations based on the much larger
390:but its sources remain unclear because it lacks
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156:showing the map and plotters and with the
421:Learn how and when to remove this message
317:The RAF's post-war system was originally
171:of fighter control, information from the
505:List of government and military acronyms
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27:System for intercepting hostile aircraft
485:Boeing Ground-to-Air Pilotless Aircraft
69:, the first national-scale system. The
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500:List of established military terms
441:Airborne Early Warning and Control
435:Airborne Early Warning and Control
359:Airborne Early Warning and Control
116:Airborne Early Warning and Control
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288:Semi Automatic Ground Environment
111:remained a mostly manual system.
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204:, subsequent bombing attacks of
527:Jindalee over-the-horizon radar
353:Jindalee over-the-horizon radar
57:organization, which became the
31:Ground-controlled interception
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266:More recently, in both the
41:tactic whereby one or more
18:Ground control interception
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510:Index of aviation articles
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333:English Electric Lightning
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83:Previous systems, notably
522:Radarpages.co.uk GCI page
376:This article includes a
133:Radar Coverage 1939-1940
532:GCI Online Radar Museum
405:more precise citations.
251:campaign ended in May.
219:Plan Position Indicator
189:radio direction finding
101:surface-to-air missiles
55:London Air Defence Area
567:Aerial warfare tactics
453:radar warning receiver
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308:interceptor aircraft
214:height finding radar
185:Royal Observer Corps
97:interceptor aircraft
47:interceptor aircraft
340:early warning radar
241:Bristol Beaufighter
549:2015-09-24 at the
465:Signal Corps Radio
378:list of references
181:RAF Bentley Priory
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480:Linesman/Mediator
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167:In the original
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