Ground-controlled interception

Ground-controlled interception (GCI) is an <a href="/facts/Air_defence/fHtGQpLy">air defence</a> tactic whereby one or more <a href="/facts/Radar_station/jk9BTbFA">radar stations</a> or other observational stations are linked to a command communications centre which guides <a href="/facts/Interceptor_aircraft/HhjPMdnf">interceptor aircraft</a> to an airborne target. This tactic was pioneered during <a href="/facts/World_War_I/vITTUanQ">World War I</a> by the <a href="/facts/London_Air_Defence_Area/Uequ8XwV">London Air Defence Area</a> organization, which became the <a href="/facts/Royal_Air_Force/P10CbL5H">Royal Air Force</a>'s <a href="/facts/Dowding_system/TMxPVVF4">Dowding system</a> in <a href="/facts/World_War_II/2efV5L1U">World War II</a>, the first national-scale system. The <a href="/facts/Luftwaffe/k7PAsBlo">Luftwaffe</a> 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 <a href="/facts/Cold_War/spJdJQ3q">Cold War</a> era.
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. Previous systems, notably <a href="/facts/Chain_Home/XPwgbaQr">Chain Home</a> (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.
GCI systems grew in size and sophistication during the post-war era, in response to the overwhelming threat of nuclear attack. The US' <a href="/facts/Semi-Automatic_Ground_Environment/qAPVULus">SAGE</a> 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 <a href="/facts/Interceptor_aircraft/HhjPMdnf">interceptor aircraft</a> or <a href="/facts/Surface-to-air_missile/2qEW5P07">surface-to-air missiles</a> against it. In some cases, SAGE sent commands directly to the aircraft's <a href="/facts/Autopilot/cypCha01">autopilot</a>, bringing the aircraft within attack range entirely under computer control. The RAF counterpart, <a href="/facts/ROTOR/971K8DCR">ROTOR</a> remained a mostly manual system.
Today, GCI is still important for most nations, although <a href="/facts/Airborne_Early_Warning_and_Control/VXDQUphK">Airborne Early Warning and Control</a>, with or without support from GCI, generally offers much greater range due to the much more distant <a href="/facts/Radar_horizon/JQVWBfyB">radar horizon</a>.

Ground-controlled interception open-in-new

Ground-controlled interception