From 1954 into 1982, the United States military relied on the EC-121 "Warning Star" platform as its primary Airborne Early Warning (AEW) system. AEW aircraft were developed to provide battlespace command and direction for allied forces through the tracking of all presented aircraft, ground vehicles and naval assets. This sort of management proved ultra-critical in the evolving age of electronics and processing which saw an elevated reliance on all manner of scanning, tracking and detection. Aircraft like the EC-121, therefore, served as "directors" to oversee a given battlefield from lofty positions in the sky. The Warning Star series, based on Lockheed's "Constellation" line, fulfilled this requirement and was produced across 232 examples, largely remembered for their triple-fin tails and hump back fuselage spines. These aircraft served throughout the Vietnam War (1955-1975) and were popularly known by their nickname of "Connie", of course born of the original Constellation name.
Into the 1960s, the United States Air Force (USAF) was already planning for a new AEW platform with much improved battlespace capabilities and would serve as a direct successor to the EC-121 line. Turbofan jet technology now allowed for larger aircraft to fly farther and higher than previous and the Boeing 707 was formally selected as the "carrier" for a powerfully advanced radar system. Two systems were then trialled on two Boeing 707 airframes - one radar from Westinghouse and the other from competing Hughes. The Westinghouse design was officially selected and the resulting aircraft became the E-3 "Sentry". Sixty-eight E-3s were produced from 1977 into 1992. The modern E-3 is given the descriptor of "Airborne Early Warning and Control" (AEW&C) to which the common term of "AWACs" is derived.
Beyond the USAF's usage of the type, the aircraft was also sold to NATO, the British Royal Air Force (RAF), the French Air Force and Saudi Arabia. After the United States, NATO became the largest operator with eighteen airframes in its stable.
The E-3 was born from the original "EX-137D" prototype of which two were constructed to evaluate the competing radar installations. These were powered by 4 x Pratt & Whitney T3D series jet engines (the same as found on the Boeing B-52H "Stratofortress" and Lockheed C-131 "Starlifter"). The initial production mark was the E-3A and powered by Pratt & Whitney TF33 series jet engines and outfitted with the AN/APY-1 series radar suite. Twenty-four were produced. The E-3B was an improved form of which 24 were converted to the new standard from existing E-3A models. The E-3C was outfitted with the more powerful AN/APY-2 radar system and added crew control stations. Ten of the type were produced with nine born from an original E-3B order for 34 B-model aircraft. One E-3C was used as the "JE-3C" for testing by Boeing. E-3D and E-3F were foreign export marks - the former to the RAF and the latter to the French Air Force. The D-model incorporated CFM56 series engines and were designated "Sentry AEW.1" for RAF service. F-models to the French Air Force were similarly powered though outfitted with French-required systems. The British received seven aircraft to the French's four. Saudi E-3's are represented through five E-3A models and a further eight KE-3A used in the aerial tanker role.
As an interesting aside, Iran had ordered some ten E-3 Sentry aircraft for its revamped air force, however, the 1979 Revolution terminated any possibility of a sale from the United States to the Islamic nation.
The most recent E-3 Sentry production mark is the "E-3G" which brings about major improvements through the Block 40/45 initiative. The initiative - currently (2013) under testing with Boeing - will upgrade avionics and mission performance capabilities as well as onboard electronics. A further proposed upgrade could see the old-style cockpit replaced with a more modern design including an "all-glass" approach now common to current- and next-generation aircraft.
The primary USAF/NATO E-3 includes a flight crew of four personnel with 13 to 19 mission crew added. These aircraft are powered by 4 x Pratt & Whitney TF33-PW-100A turbofan engines, each delivering 21,500lbs of thrust. Maximum speed is 530 miles per hour with a range out to 4,000 nautical miles while operating at service ceilings nearing 41,000 feet. The aircraft has a mission endurance time of eight hours which is crucial to an ongoing military campaign. It can be refueled from USAF KC-135 Stratotankers and similar for much-improved operational ranges and mission endurance times.
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July 2017 - Boeing has won a contract to upgrade the French fleet of E-3 Sentry aircraft. The upgrades (digital glass cockpits, updated navigation and airspace equipment) will follow those already being applied to both United States Air Force and NATO Sentry aircraft. The work will span from 2019 into 2024 on French soil (Air France).
January 2020 - The British Royal Air Force (RAF) has returned one of its E-3D platforms for permanent storage in the United States.
January 2021 - The British Ministry of Defense (MoD) is selling off two of its retired E-3D Sentry aircraft for scrapping.
August 2021 - The British Royal Air Force has ended operations involving their fleet of aging E-3D "Sentry" platforms. The service spans some thirty total years. Beginning in 2023, the gap will be filled by the fleet of three-strong E-7A "Wedgetail" (Boeing 737) type.
September 2021 - The USAF is eying the purchase of the E-7 Wedgetail AWACs platform to succeed an aging line of E-3 Sentry platforms in same role.
February 2022 - Britain has announced it is selling an unspecified number of former Royal Air Force (RAF) E-3D Sentry platforms to the nation of Chile.
April 2022 - The USAF has committed to the purchase of the E-7A Wedgetail to fulfill its AWACS requirement and succeed an aging line of Boeing E-3 Sentrys in same role. The initial service-centric prototype is expected in 2027.
Boeing Aerospace Company - USA Manufacturer(s)
Chile (ex-RAF, announced Feb 2022); France; NATO; Saudi Arabia; United Kingdom; United States Operators
Design utilizes a single primary wing mainplane; this represents the most popular modern mainplane arrangement.
Mainplanes are low-mounted along the sides of the fuselage.
The planform features wing sweep back along the leading edges of the mainplane, promoting higher operating speeds.
4 x Pratt and Whitney TF33-PW-100A turbofan engines developing 21,500 lb thrust each. Propulsion
None. Mission equipment carried for battlespace direction.
EC-137D - Two Examples Prototype AWACS; fitting JT3D series engines; first prototype fitting Westinghouse-brand radar system whilst second prototype fitting Hughes-brand radar system; later converted to E-3A standard and fitting TF33 series engines.
E-3A - Initial Production Model Designation; fitted with TF33 engines; AN/APY-1 series radar system; 25 examples produced for USAF (later converted to E-3B standard); 18 examples produced for NATO usage fitting TF33 series engines; 5 examples produced for Saudi Arabia fitting CFM56 engines.
E-3B - Based on E-3A models but featuring improvements; 24 conversion examples.
E-3C - Fitted with AN/APY-2 radar system; system improvements throughout; 9 examples produced.
JE-3C - One-Off Trials Aircraft utilized by Boeing; later becoming an E-3C.
E-3D - British production E-3C model; fitted with CFM56 engines; 7 examples produced.
E-3F - French production E-3C model; fitted with CFM56 engines; 4 examples produced.
E-3G - Block 40/45 modification; Airframe Modernization Program (AMP); USAF usage.
KE-3A - Saudi Arabian tankers fitted with CFM56 engines; 8 examples produced.
Sentry AEW.1 - British Designation of E-3D model.
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