The Boeing E-3A Sentry is essentially a flexible, jamming-resistant, mobile and survivable airborne radar station. The Airborne Warning and Control System (AWACS) is tasked primarily with airborne surveillance, but can also act as a command and control centre.
Boeing was awarded a contract on 23 July 1970 to provide two EC-137D prototypes. Based on the airframe of the Model 707-300B airliner, these added a large 9.14-m diameter rotodome above the rear fuselage to house the antenna for the search radar. Other essential avionics antennae are housed within the wing, fuselage and tail unit. The cabin is fitted with equipment bays and SDCs (Situation Display Consoles) for the AWACS specialist officers. The first test aircraft flew on 5 February 1972 and the first production E-3A was delivered to the USAF on 24 March 1977.
The E-3A has been replaced in USAF service by the E-3B and E-3C, with upgraded APY-2 radar, higher-speed computers and secure communications facilities. THe E-3C also has five additional operator consoles. In 2001 the USAF AWACS force numbers 18 E-3B/C aircraft, while NATO continues to fly the 17 survivors of 18 jointly funded E-3As. Based at Geilenkirchen, Germany, these have been extensively updated, most recently with the addition of the AN/AYR-1 ESM system.
E-3s powered by CFM56 engines serve with France (four E-3Fs), Saudi Arabia (five E-3As) and the UK (seven E-3D Sentry AEW.Mk 1s). The E3 remains invaluable to the USAF's front-line force, and the service is currently considering upgrading its E-3s with the glass flightdeck of the Next Generation Model 737 and the Eagle system (to detect and track theatre ballistic missiles), with an infre-red search and track sensor and a laser rangefinder. Major upgrades are also planned for the radar, computer and navigation systems, as well as re-engining with CFM56 (F108) powerplants.