Ground-controlled ( GCI ) is an air defense tactic in which one or more radar stations or other observation stations are related to the command communication center that guides the interceptor to the target air. This tactic was pioneered during World War I by the organization of the London Air Defense Area, which became the Royal Air Force Dowding system in World War II, the first national-scale system. The Luftwaffe introduced the same system during the war, but most other combatants did not experience the same threat of airstrikes and did not develop such complex systems until the Cold War era.
Today the term GCI refers to the style of battle direction, but during World War II it also refers to the radar itself. In particular, the term is used to describe a new generation of radars that rotate on their vertical axis to provide a complete 360-degree view of the sky around the station. Previous systems, notably Chain Home (CH), can only be directed along the antenna in front of the angle, and can not direct traffic after passing back behind their beachfront location. The GCI radar began to replace CH starting in 1941/42, allowing one station to control the entire battle from early detection to directing fighters to intercept.
The GCI system grew in size and sophistication during the post-war era, in response to the threat of a tremendous nuclear strike. The US SAGE system may be the most complicated effort, using a building filling computer connected with dozens of radar and other sensors to automate all tasks identifying enemy aircraft paths and directing interceptor aircraft or surface-to-surface missiles against them. In some cases, SAGE sends commands directly to the autopilots of the aircraft, bringing the aircraft within range of attack completely under the control of the computer.
Currently, GCI is still important for most countries, although Airborne Early Warning and Control, with or without support from GCI, generally offers a much greater range because of far greater radar distances.
Video Ground-controlled interception
World War II
In the original Dowding combat control system, information from the Chain Home coastal radar station was diverted by telephone to a number of operators on the ground floor "filter room" at Fighter Command headquarters at RAF Bentley Priory. Here the information from the radar is combined with reports from the Royal Observer Corps and a radio directional search system and combined to produce a set of "traces", which are identified by numbers. This track then calls to the headquarters of the Group which will be responsible for handling that target. The group will assign the combat squadron to the track, and call the information to the Section headquarters, which is directly related to the fighters. This fighter can then be "randomized" to intercept the plane.
Since the House Chain radar station faces the sea, once airborne intruders have crossed the English coast, they are no longer trackable by the radar; and thus centers of interception directions depend on the visual and aural visions of the Observer Corps for updated information about the location and title of enemy aircraft formation. While these arrangements work well during daytime attacks from the Battle of Britain, the subsequent bombing attacks from The Blitz indicate that such a technique is entirely inadequate to identify and track aircraft at night.
Experiments in dealing with this problem began with manual-directed radar used as a kind of radio spotlight, but this proved too difficult to use in practice. Another effort is made using an elevation radar mounted on its side to scan the arc in front of the station. This proved to be very workable, and was soon expanded to include a full 360 degrees by making small changes to support systems and bearings. Creating a viewing system, "Position Indicators Plan" (PPI), featuring a 360 degree pattern proved very easy, and a test system was available by the end of 1940.
Beginning in 1941 the RAF began deploying the GCI radar production model, first with a thoughtful solution, and then a permanent station. Unlike the previous system in which radar data was forwarded by the phone and plotted on the map, GCI radar merged all of these functions into one station. The PPI is in the form of a top-down 2D display that shows both the target and the intercepting night warriors. Interceptions can be set directly from the screen, without the need to forward information over a telephone line or the like. This not only greatly eases the task of managing interception, but also greatly reduces the labor required.
When the system started to operate, the success of the RAF night combat troop began to increase. This is aided by the introduction of Bristol Beaufighter and its AI Mk. The Radar IV becomes available in number at the same time. Both of these systems proved to be strong combinations, and the interception rate doubled every month from January 1941 until the Luftwaffe campaign ended in May.
Germany was slow enough to follow the terms of the PPI and did not order the operational version of their Jagdschloss radar until the end of 1943, with relatively slow deliveries thereafter. Many are still under construction when the war ended in 1945.
Maps Ground-controlled interception
Post WWII
Recently, both in the Korean and Vietnamese War, North Korea and North Vietnam have an important GCI system that helps them harass opposing troops (though in both cases due to superiority in the number of US aircraft, the effect is ultimately minimized). GCI is important for US forces and allies during this conflict as well, though not as much as their opponents.
The most advanced GCI system used to date is the US Semi Automatic Ground Environment (SAGE) system. SAGE uses a massive computer to combine reports sent via teleprinters from Pinetree Line and other radar networks to produce images of all air traffic in certain "sector" areas. The information is then displayed on the terminal in the building, which allows operators to select defense assets (fighters and missiles) to be directed to targets simply by selecting them in the terminal. Messages are then automatically redirected via the teleprinter with instructions on them.
The SAGE Long Radar Station is described in the On-line Radar Museum. See radomes.org/museum
The system is then upgraded to deliver directional information directly to autopilot interceptor aircraft such as the F-106 Delta Dart. The pilot is assigned mainly by bringing the plane into the air (and back), and then flying in a parking orbit until requested. When the interception mission begins, the SAGE computer automatically flies the plane into the target range, allowing the pilot to concentrate solely on the operation of a complex onboard radar.
GCI is usually augmented by the presence of very large early warning radar, which can warn GCI against hostile flying hours before arriving, allowing enough time to prepare and launch the aircraft and arrange for interception either using their own radar or with the help of a regular radar station once the bogey approaching their reach. An example of this type of system is the Jindalee radar above the Australian horizon. Such radar usually operates by reflecting their signals from layers in the atmosphere.
Early Warning and Air Control
In recent years, GCI has been replaced, or replaced directly, with the introduction of Aircraft Early Warning and Air Control (AEW & amp; C, often called AWACS). AEW & C tends to be superior in that, because of the air and being able to see down, it can see targets far enough at low levels, as long as it can pick it up from the clutter of the ground. AEW & amp; C is very expensive, and generally requires a dedicated aircraft to protect them. The combination of these two techniques is really ideal, but GCI is usually only available in the defense of one's homeland, rather than in the type of expedition battles.
The strength of GCI is that it can include more air space than AEW & amp; C without as much cost and areas that otherwise would be a blind spot for AEW & amp; C can be reached by smartly placed radar stations. AEW & amp; C also depends on aircraft that may require defense and some aircraft are more vulnerable than many ground-based radar stations. If one AEW & amp; C is shot down or taken from the picture, there will be a serious gap in air defense until others can replace it, where in the case of GCI, many radar stations have to be removed from the air before it becomes a serious problem. In both cases the strike at the command center can be very serious.
Whether GCI or AEW & amp; C can be used to provide the main profit aircraft defense during the actual interception by allowing them to sneak onto enemy planes without breaking away by using their own radar devices. Typically, to perform their own interception beyond the visual range, the aircraft must search the sky for intruders with their radar, an energy that may be noticed by an intruder alert warning device (RWR), thus warning intruders that they may be attacked. With GCI or AEW & amp; C, the surviving aircraft can be vectored to the interception path, possibly sliding in at the unknown tail's tail position, firing passive homing missiles and then turning. Or, they can light their radar at the last moment, so they can get a radar lock and guide their missiles. This greatly increases the chances of success and the survival of the interceptor.
See also
- K-35 Trailer
- Signal Corps Radio
- Office hours
- ROTOR
- Planner/Mediator
- Boeing Ground-to-Air Planes
- UCAV
- STRIL
References
- GCI Radarpages.co.uk page
- Jindalee over-the-horizon radar
- GCI Online Radar Museum
External links
- Ground Interception Interception Controlled in Neptune/Overlord (pdf)
Source of the article : Wikipedia
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