Boeing E-3 Sentry AWACS

Summary

Description

In the mid-1960s, the U.S. Air Force initiated a program to replace its Lockheed EC-121 Warning Star aircraft. After evaluating preliminary development proposals from Boeing, Douglas, and Lockheed, Boeing was selected to build two prototype airframes for comparative testing of competing radar systems developed by Westinghouse Electric and Hughes Aircraft Company. Both radar systems employed pulse-Doppler technology, with Westinghouse's design ultimately being chosen for the production aircraft. Flight testing on the first production E-3 commenced in October 1975. The first USAF E-3 was delivered in March 1977. An order from Iran for ten E-3s in 1977 was cancelled following the Iranian Revolution. Production concluded in 1992, resulting in a total of 68 aircraft built.

The E-3 Sentry airframe is derived from a modified Boeing 707-320B Advanced, distinguished by a rotating radar dome, or rotodome, positioned above the fuselage. Structural modifications include uprated hydraulics, increased from 241 bar to 345 bar, specifically to power the rotodome's rotation system, and provisions for both single-point ground refueling and air refueling. The rotodome, which is unpressurized, has a diameter of 30 feet, is 6 feet thick at its center, and is elevated 11 feet above the fuselage via two support struts. To minimize aerodynamic drag during flight, the rotodome is engineered with a slight downward tilt at the front; this tilt is electronically compensated for by the radar and secondary surveillance radar antenna phase shifters to maintain directional accuracy. Temperature control for the electronic and mechanical components within the rotodome is managed by bleed air and a fluorocarbon-based cold plate cooling system. The rotodome houses the AN/APY-1 and AN/APY-2 passive electronically scanned array radar systems, which provide surveillance coverage from ground level up to the stratosphere, effective over both land and water. Data processed by the aircraft's computer systems is displayed on fourteen onboard consoles, presenting information in graphic and tabular formats to support surveillance, target identification, weapons control, battle management, and communications conducted by the mission operators.

The primary function of the Boeing E-3 Sentry is airborne early warning and control, not offensive engagement. Consequently, the aircraft is not equipped with internal weapon bays or external hardpoints designed to carry ordnance such as bombs or missiles. The substantial internal volume of the E-3 is utilized to accommodate its extensive radar systems, computing infrastructure, and multiple operator consoles, all essential for its surveillance, command, control, and communications roles.

Since its introduction, the E-3 Sentry has been deployed extensively in operational environments worldwide. Deliveries of the initial USAF E-3s began in March 1977. By 1991, the aircraft demonstrated its operational significance during the Persian Gulf War, where it provided command and control for coalition aircraft operations against Iraqi forces, accumulating 5,052 hours of on-station surveillance time and contributing to 38 of the 41 documented air-to-air engagements resulting in kills during the conflict. NATO, UK, French, and USAF E-3s were also integral to the air campaign over Serbia and Montenegro during Operation Allied Force from March to June 1999, directing allied strike and air defense assets. More recently, in November 2015, an E-3G variant was deployed to the Middle East to conduct combat missions in support of Operation Inherent Resolve against ISIL, marking the first operational combat deployment of the upgraded Block 40/45 standard aircraft. Beyond the USAF, the United Kingdom's E-3D aircraft contribute to the NATO Airborne Early Warning and Control Force while also maintaining the capability for independent national tasking, deploying to locations such as Cyprus in 2015 to support U.S.-led coalition airstrikes targeting Islamic State militants. France independently operates its fleet of E-3F aircraft.

Main Variants:

• EC-137D: Two prototype aircraft equipped with JT3D engines and used for radar competition testing, one fitted with a Westinghouse radar and the other with a Hughes radar, later converted to the E-3A standard with TF33 engines.

• E-3A: The initial production configuration powered by TF33 engines and featuring the AN/APY-1 radar, with 24 built for the USAF (subsequently converted to E-3B standard) and 18 delivered to NATO.

• KE-3A: A tanker variant based on the E-3 airframe but without AWACS mission systems, powered by CFM56 engines and delivered to Saudi Arabia.

• E-3B: An upgraded version derived from the E-3A, incorporating enhancements as part of the USAF's Block 30 program, with 24 aircraft modified to this standard.

• E-3D: Production aircraft for the RAF built to E-3C standards, fitted with CFM56 engines and incorporating British-specific equipment modifications, designated Sentry AEW.1, with seven units produced.

Technical specifications

Current operating countries

Country		Units
	United States	31
	Saudi Arabia	5
	France	4
	Chile	1 (+1)

Numbers in parentheses, e.g. '(+5)', indicate units ordered but not yet delivered.

All operators

Chile • France • United Kingdom • Saudi Arabia • United States

Photo of E-3 Sentry AWACS