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The Boeing E-3 Sentry is an American airborne early warning and control (AEW&C) aircraft developed by
Boeing The Boeing Company, or simply Boeing (), is an American multinational corporation that designs, manufactures, and sells airplanes, rotorcraft, rockets, satellites, and missiles worldwide. The company also provides leasing and product support s ...
. E-3s are commonly known as AWACS (Airborne Warning and Control System). Derived from the
Boeing 707 The Boeing 707 is an early American long-range Narrow-body aircraft, narrow-body airliner, the first jetliner developed and produced by Boeing Commercial Airplanes. Developed from the Boeing 367-80 prototype, the initial first flew on Decembe ...
airliner, it provides all-weather surveillance, command, control, and communications, and is used by the
United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...
,
NATO The North Atlantic Treaty Organization (NATO ; , OTAN), also called the North Atlantic Alliance, is an intergovernmental organization, intergovernmental Transnationalism, transnational military alliance of 32 Member states of NATO, member s ...
, French Air and Space Force, Royal Saudi Air Force and
Chilean Air Force The Chilean Air Force () is the air force of Chile and branch of the Chilean military. History The first step towards the current FACh is taken by Lieutenant Colonel, Teniente Coronel training as a pilot in France. Although a local academy was c ...
. The E-3 has a distinctive rotating radar dome (rotodome) above the fuselage. Production ended in 1992 after 68 aircraft had been built. In the mid-1960s, the U.S. Air Force (USAF) was seeking an aircraft to replace its piston-engined Lockheed EC-121 Warning Star, which had been in service for over a decade. After issuing preliminary development contracts to three companies, the USAF picked Boeing to construct two airframes to test Westinghouse Electric's and Hughes's competing radars. Both radars used pulse-Doppler technology, with Westinghouse's design emerging as the contract winner. Testing on the first production E-3 began in October 1975. The first USAF E-3 was delivered in March 1977, and during the next seven years, a total of 34 aircraft were manufactured. E-3s were also purchased by NATO (18), the United Kingdom (7), France (4) and
Saudi Arabia Saudi Arabia, officially the Kingdom of Saudi Arabia (KSA), is a country in West Asia. Located in the centre of the Middle East, it covers the bulk of the Arabian Peninsula and has a land area of about , making it the List of Asian countries ...
(5). In 1991, when the last aircraft had been delivered, E-3s participated in the Persian Gulf War, playing a crucial role of directing
coalition A coalition is formed when two or more people or groups temporarily work together to achieve a common goal. The term is most frequently used to denote a formation of power in political, military, or economic spaces. Formation According to ''A G ...
aircraft against Iraqi forces. The aircraft was also the last of the Boeing 707 derivatives after 34 years of continuous production. The aircraft's capabilities have been maintained and enhanced through numerous upgrades. In 1996, Westinghouse Electric's Defense & Electronic Systems division was acquired by Northrop Corporation, before being renamed Northrop Grumman Mission Systems, which currently supports the E-3's radar. In April 2022, the U.S. Air Force announced that the Boeing E-7 is to replace the E-3 beginning in 2027.


Development


Background

In 1963, the USAF asked for proposals for an Airborne Warning and Control System (AWACS) to replace its EC-121 Warning Stars, which had served in the airborne early warning role for over a decade. The new aircraft would take advantage of improvements in radar technology and computer-aided radar data analysis and data reduction. These developments allowed airborne radars to " look down", i.e. to detect the movement of low-flying aircraft, and discriminate, even over land, target aircraft's movements; previously this had been impossible due to the inability to discriminate an aircraft's track from ground clutter.Eden et al. 2004, p. 92. Contracts were issued to Boeing, Douglas, and Lockheed, the latter being eliminated in July 1966. In 1967, a parallel program was put into place to develop the radar, with Westinghouse Electric Corporation and Hughes Aircraft being asked to compete in producing the radar system. In 1968, it was referred to as Overland Radar Technology (ORT) during development tests on the modified EC-121Q.Davies 2005, p. 2. The Westinghouse radar antenna was going to be used by whichever company won the radar competition since Westinghouse had pioneered the design of high-power
radio frequency Radio frequency (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the u ...
(RF) phase-shifters, which are used to both focus the RF into a pencil beam and scan electronically for altitude determination. Boeing initially proposed a purpose-built aircraft, but tests indicated it would not outperform the already-operational 707, so the latter was chosen instead. To increase endurance, this design was to be powered by eight General Electric TF34s. It would carry its radar in a rotating dome mounted at the top of a forward-swept tail, above the fuselage. Boeing was selected ahead of
McDonnell Douglas McDonnell Douglas Corporation was a major American Aerospace manufacturer, aerospace manufacturing corporation and defense contractor, formed by the merger of McDonnell Aircraft and the Douglas Aircraft Company in 1967. Between then and its own ...
's DC-8-based proposal in July 1970. Initial orders were placed for two aircraft, designated EC-137D, as test beds to evaluate the two competing radars. As the test beds did not need the same 14-hour endurance demanded of the production aircraft, the EC-137s retained the Pratt & Whitney JT3D commercial engines, and a later reduction in the endurance requirement led to retention of the JT3D engines in production.Taylor et al. 1976, p.246 The first EC-137 made its maiden flight on 9 February 1972, with the fly-off between the two radars taking place from March to July of that year. Favorable test results led to the selection of Westinghouse's radar for the production aircraft.Davies 2005, pp. 5–6. Hughes' radar was initially thought to be a certain winner due to its related development of the APG-63 radar for the new F-15 Eagle. The Westinghouse radar used a pipelined
fast Fourier transform A fast Fourier transform (FFT) is an algorithm that computes the discrete Fourier transform (DFT) of a sequence, or its inverse (IDFT). A Fourier transform converts a signal from its original domain (often time or space) to a representation in ...
(FFT) to digitally resolve 128 Doppler frequencies, while Hughes's radars used analog filters based on the design for the F-15. Westinghouse's engineering team won this competition by using a programmable 18- bit computer whose software could be modified before each mission. This computer was the AN/AYK-8 design from the B-57G program, and designated AYK-8-EP1 for its much expanded memory. This radar also multiplexed a beyond-the-horizon (BTH) pulse mode that could complement the pulse- Doppler radar mode. This proved to be beneficial especially when the BTH mode is used to detect ships at sea when the radar beam is directed below the horizon.


Full-scale development

Approval was given on 26 January 1973 for the full-scale development of the AWACS system. To allow further development of the aircraft's systems, orders were placed for three preproduction aircraft, the first of which performed its maiden flight in February 1975. IBM and Hazeltine were selected to develop the mission computer and display system. The IBM computer was designated 4PI, and the software was written in JOVIAL. A
Semi-Automatic Ground Environment The Semi-Automatic Ground Environment (SAGE) was a system of mainframe computer, large computers and associated computer network, networking equipment that coordinated data from many radar sites and processed it to produce a single unified image ...
(SAGE) or back-up interceptor control (BUIC) operator would immediately be at home with the track displays and tabular displays, but differences in symbology would create compatibility problems in tactical ground radar systems in
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, mainland Europe, and South Korea over Link-11 (TADIL-A). In 1977, Iran placed an order for ten E-3s, however this order was cancelled following the
Iranian Revolution The Iranian Revolution (, ), also known as the 1979 Revolution, or the Islamic Revolution of 1979 (, ) was a series of events that culminated in the overthrow of the Pahlavi dynasty in 1979. The revolution led to the replacement of the Impe ...
. Engineering, test and evaluation began on the first E-3 Sentry in October 1975. Between 1977 and 1992, a total of 68 E-3s were built.


Future status

Because the Boeing 707 is no longer in production, the E-3 mission package has been fitted into the Boeing E-767 for the Japan Air Self Defense Forces. The E-10 MC2A was intended to replace USAF E-3s—along with the RC-135 and the E-8 Joint STARS, but the program was canceled by the Department of Defense. NATO intends to extend the operational status of its AWACS until 2035 when it is due to be replaced by the Alliance Future Surveillance and Control (AFSC) program.NATO summit Warsaw July 2016 The
Royal Air Force The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...
(RAF) chose to limit investment in its E-3D fleet in the early 2000s, diverting Sentry upgrade funds to a replacement program. On 22 March 2019, the UK Defence Secretary announced a $1.98 billion (~$ in ) contract to purchase five Boeing E-7 Wedgetails. The U.S. Air Force intends to retire 15 of its 31 E-3s and acquire the E-7. On 31 March 2023, the USAF retired an E-3 from service for the first time.


Design


Overview

The E-3 Sentry's airframe is a modified Boeing 707-320B Advanced model. Modifications include a rotating radar dome ( rotodome), uprated hydraulics from 241 to 345 bar (3500–5000 psi) to drive the rotodome, single-point ground refueling, air refueling, and a bail-out tunnel or chute. A second bail-out chute was deleted to cut mounting costs. USAF and NATO E-3s have an unrefueled range of or 8 hours of flying. The newer E-3 versions bought by France, Saudi Arabia, and the UK are equipped with newer CFM56-2 turbofan engines, and these can fly for about 11 hours or more than . The Sentry's range and on-station time can be increased through
air-to-air refueling Aerial refueling ( en-us), or aerial refuelling ( en-gb), also referred to as air refueling, in-flight refueling (IFR), air-to-air refueling (AAR), and tanking, is the process of transferring aviation fuel from one aircraft (the tanker) to an ...
and the crews can work in shifts by the use of an on-board crew rest and meals area. The aircraft are equipped with one toilet in the rear, and a urinal behind the cockpit. Saudi E-3s were delivered with an additional toilet in the rear. When deployed, the E-3 monitors an assigned area of the battlefield and provides information for commanders of air operations to gain and maintain control of the battle; while as an air defense asset, E-3s can detect, identify, and track airborne enemy forces far from the boundaries of the U.S. or NATO countries and can direct interceptor aircraft to these targets. In support of air-to-ground operations, the E-3 can provide direct information needed for interdiction, reconnaissance, airlift, and close-air support for friendly ground forces.


Avionics

The unpressurized rotodome is in diameter, thick at the center, and is held above the fuselage by 2 struts. It is tilted down at the front to reduce its aerodynamic drag, which lessens its detrimental effect on take-offs and endurance. This tilt is corrected electronically by both the radar and secondary surveillance radar antenna phase shifters. The rotodome uses
bleed air Bleed air in aerospace engineering is compressed air taken from the compressor stage of a gas turbine, upstream of its fuel-burning sections. Automatic air supply and cabin pressure controller (ASCPC) valves bleed air from low or high stage engine ...
, outside cooling doors, and fluorocarbon-based cold plate cooling to maintain the electronic and mechanical equipment temperatures. The hydraulically rotated antenna system permits the and AN/APY-2 passive electronically scanned array radar system to provide surveillance from the Earth's surface up into the
stratosphere The stratosphere () is the second-lowest layer of the atmosphere of Earth, located above the troposphere and below the mesosphere. The stratosphere is composed of stratified temperature zones, with the warmer layers of air located higher ...
, over land or water. Other major subsystems in the E-3 Sentry are navigation, communications, and computers. 14 consoles display computer-processed data in graphic and tabular format on screens. Its operators perform surveillance, identification, weapons control, battle management and communications functions. Data may be forwarded in real-time to any major command and control center in rear areas or aboard ships. In times of crisis, data may also be forwarded to the National Command Authority in the U.S. via RC-135 or
aircraft carrier An aircraft carrier is a warship that serves as a seagoing airbase, equipped with a full-length flight deck and hangar facilities for supporting, arming, deploying and recovering carrier-based aircraft, shipborne aircraft. Typically it is the ...
task forces.
Electrical generator In electricity generation, a generator, also called an ''electric generator'', ''electrical generator'', and ''electromagnetic generator'' is an electromechanical device that converts mechanical energy to electrical energy for use in an extern ...
s mounted in each of the E-3's four engines provide 1
megawatt The watt (symbol: W) is the unit of Power (physics), power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kgâ‹…m2â‹…s−3. It is used to quantification (science), quantify the rate of Work ...
of electrical power required by the aircraft's radars and electronics. Its pulse-Doppler radar has a range of more than 250 mi (400 km) for low-flying targets at its operating altitude, and the pulse (BTH) radar has a range of approximately 400 mi (650 km) for aircraft flying at medium to high altitudes. The radar, combined with a secondary surveillance radar (SSR) and electronic support measures (ESM), provides a look down capability, to detect, identify, and track low-flying aircraft, while eliminating ground clutter returns.


Upgrades

Between 1987 and 2001, USAF E-3s were upgraded under the "Block 30/35 Modification Program". Enhancements included: *The installation of ESM and an electronic surveillance capability, for both active and passive means of detection. *Installation of the Class 2H Joint Tactical Information Distribution System (JTIDS), which provides rapid and secure communication for transmitting information, including target positions and identification data, to other friendly platforms. This upgraded system allowed the Link 16 military tactical data link capability to be added as part of the Block 30/35 upgrade. Prior versions of the E-3 (NATO/US Standard and 20/25) had the Class 1 (Hughes) JTIDS system which was not Link 16 capable. *
Global Positioning System The Global Positioning System (GPS) is a satellite-based hyperbolic navigation system owned by the United States Space Force and operated by Mission Delta 31. It is one of the global navigation satellite systems (GNSS) that provide ge ...
(GPS) capability was added. *Onboard computers and software were overhauled to accommodate the JTIDS Class 2H, Link 16, the new ESM systems and to allow for future enhancements.


RSIP

The Radar System Improvement Program (RSIP) was a joint US/NATO development program. RSIP enhances the operational capability of the E-3 radars' electronic countermeasures, and improves the system's reliability, maintainability, and availability. Essentially, this program replaced the older transistor-transistor logic (TTL) and emitter-coupled logic (MECL) electronic components, long-since out of production, with off-the-shelf
computer A computer is a machine that can be Computer programming, programmed to automatically Execution (computing), carry out sequences of arithmetic or logical operations (''computation''). Modern digital electronic computers can perform generic set ...
s that utilised a
High-level programming language A high-level programming language is a programming language with strong Abstraction (computer science), abstraction from the details of the computer. In contrast to low-level programming languages, it may use natural language ''elements'', be ea ...
instead of
assembly language In computing, assembly language (alternatively assembler language or symbolic machine code), often referred to simply as assembly and commonly abbreviated as ASM or asm, is any low-level programming language with a very strong correspondence bet ...
. Significant improvement came from adding
pulse compression Pulse compression is a signal processing technique commonly used by radar, sonar and Ultrasound, echography to either increase the range angular resolution, resolution when pulse length is constrained or increase the Signal-to-noise ratio, signal ...
to the pulse-Doppler mode. These hardware and software modifications improve the E-3 radars' performance, providing enhanced detection with an emphasis towards low radar cross-section (RCS) targets. The RAF had also joined the USAF in adding RSIP to upgrade the E-3's radars. The retrofitting of the E-3 squadrons was completed in December 2000. Along with the RSIP upgrade was installation of the Global Positioning System/Inertial Navigation Systems which improved positioning accuracy. In 2002, Boeing was awarded a contract to add RSIP to the small French AWACS squadron. Installation was completed in 2006. Saudi Arabia began RSIP upgrades in 2013; the first aircraft being upgraded by Boeing in Seattle with the four remaining aircraft upgraded in Riyadh between 2014 and 2016.


NATO Mid Term Program

Between 2000 and 2008 NATO upgraded its E-3s to ''Mid Term Program'' (MTP) standard. This involved technical upgrades and a total multi-sensor-systems integration


DRAGON

In 2009, the USAF, in cooperation with NATO, entered into a major flight deck avionics modernization program in order to maintain compliance with worldwide airspace mandates. The program, called DRAGON (for DMS Replacement of Avionics for Global Operation and Navigation), was awarded to Boeing and
Rockwell Collins Rockwell Collins, Inc. was a multinational corporation headquartered in Cedar Rapids, Iowa, providing avionics and information technology systems and services to government agencies and aircraft manufacturers. It was formed when the Collins Radi ...
in 2010. Drawing on their Flight2 flight management system (FMS), almost all the avionics were replaced with more modern digital equipment from Rockwell Collins. Main upgrades include a Digital Audio Distribution System, Mode-5/ ADS-B transponder, Inmarsat and VDL datalinks, and a terrain awareness and warning system (TAWS). The centerpiece flight deck hardware consists of five 6x8 color graphics displays and two color CDUs. DRAGON laid the foundation for subsequent upgrades including GPS M-Code, Iridium ATC, and Autopilot. USAF DRAGON Production began in 2018.


USAF Block 40/45

In 2014 the USAF began upgrading block 30/35 E-3B/Cs into block 40/45 E-3Gs. This upgrade replaces the main flight computer with a Red Hat Linux-based system, as well as replacing the DOS 2.0-like operating system with a
Windows 95 Windows 95 is a consumer-oriented operating system developed by Microsoft and the first of its Windows 9x family of operating systems, released to manufacturing on July 14, 1995, and generally to retail on August 24, 1995. Windows 95 merged ...
-like system on the operator workstations. In 2016, a three-week long cybersecurity vulnerability test revealed that the 40/45 block and its supporting ground equipment were vulnerable to cyber threats, and were thus deemed "not survivable." This caused a delay of approximately two years. Twenty-four E-3s are projected to complete this upgrade to 40/45 by the end of
fiscal year A fiscal year (also known as a financial year, or sometimes budget year) is used in government accounting, which varies between countries, and for budget purposes. It is also used for financial reporting by businesses and other organizations. La ...
2020, while seven aircraft will be retired to save upgrade costs and harvest out-of-production components.


NATO Final Lifetime Extension Program

NATO intends to extend the operational status of its AWACS until 2035 by significantly upgrading fourteen aircraft in the ''Final Lifetime Extension Program'' (FLEP) between 2019 and 2026. Upgrades include the expansion of data capacity, expansion of bandwidth for satellite communications, new encryption equipment, new HAVE QUICK radios, upgraded mission computing software and new operator consoles. The supporting ground systems (mission training center and mission planning and evaluation system) will also be upgraded to the latest standard. NATO Airborne Early Warning & Control Program Management Agency (NAPMA) is the preparing and executing authority for the FLEP. FLEP will be combined with the standard planned higher echelon technical maintenance.


Operational history


United States

In March 1977 the 552nd Airborne Warning and Control Wing received the first E-3 aircraft at
Tinker AFB Tinker Air Force Base is a major United States Air Force base, with tenant United States Navy, U.S. Navy and other United States Department of Defense, Department of Defense missions, located in Oklahoma City, Oklahoma in Oklahoma County, Okl ...
,
Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
. The 34th and last USAF Sentry was delivered in June 1984. The USAF has a total of thirty E-3s in active service. Twenty-six are stationed at Tinker AFB and belong to the
Air Combat Command The Air Combat Command (ACC) is one of nine List of Major Commands of the United States Air Force, Major Commands (MAJCOMs) in the United States Air Force, reporting to Headquarters, United States Air Force (HAF) at the Pentagon. It is the prim ...
(ACC). Four are assigned to the Pacific Air Forces (PACAF) and stationed at Kadena AB, Okinawa and Elmendorf AFB, Alaska. One aircraft (TS-3) was assigned to Boeing for testing and development (retired/scrapped June 2012). E-3 Sentry aircraft were among the first to deploy during Operation Desert Shield, where they established a radar screen to monitor Iraqi forces. During Operation Desert Storm, E-3s flew 379 missions and logged 5,052 hours of on-station time.Veronico and Dunn 2004, p. 83. The data collection capability of the E-3 radar and computer subsystems allowed an entire air war to be recorded for the first time. In addition to providing senior leadership with time-critical information on the actions of enemy forces, E-3 controllers assisted in 38 of the 41 air-to-air kills recorded during the conflict. NATO, UK, French and USAF AWACS played an important role in the air campaign against
Serbia , image_flag = Flag of Serbia.svg , national_motto = , image_coat = Coat of arms of Serbia.svg , national_anthem = () , image_map = , map_caption = Location of Serbia (gree ...
and
Montenegro , image_flag = Flag of Montenegro.svg , image_coat = Coat of arms of Montenegro.svg , coa_size = 80 , national_motto = , national_anthem = () , image_map = Europe-Mont ...
in the former republic of
FR Yugoslavia The State Union of Serbia and Montenegro or simply Serbia and Montenegro, known until 2003 as the Federal Republic of Yugoslavia and commonly referred to as FR Yugoslavia (FRY) or simply Yugoslavia, was a country in Southeast Europe locate ...
. From March to June 1999 the aircraft were deployed in the NATO bombing of Yugoslavia (operation Allied Force) directing allied strike and air defence aircraft to and from their targets. Over 1,000 aircraft operating from bases in
Germany Germany, officially the Federal Republic of Germany, is a country in Central Europe. It lies between the Baltic Sea and the North Sea to the north and the Alps to the south. Its sixteen States of Germany, constituent states have a total popu ...
and
Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...
took part in the air campaign which was intended to destroy Yugoslav air defenses and high-value targets such as the bridges across the
Danube The Danube ( ; see also #Names and etymology, other names) is the List of rivers of Europe#Longest rivers, second-longest river in Europe, after the Volga in Russia. It flows through Central and Southeastern Europe, from the Black Forest sou ...
river, factories, power stations, telecommunications facilities, and military installations. On 18 November 2015, an E-3G was deployed to the Middle East to begin flying combat missions in support of Operation Inherent Resolve against ISIL, marking the first combat deployment of the upgraded Block 40/45 aircraft.


United Kingdom

In February 1987 the UK and France ordered E-3 aircraft in a joint project which saw deliveries start in 1991. The British requirement arose due to the cancellation of the BAE Nimrod AEW3 project. UK E-3Ds contributed to the NATO Airborne Early Warning and Control Force (NAEWCF), receiving much of their tasking directly from NATO. However, RAF E-3Ds remained UK-crewed and capable of independent, national tasking. In 2009, the UK effectively limited the service life of the E-3D fleet by de-funding the Project Eagle upgrade which would have seen it upgraded in line with the USAF Block 40/45 standard. ''AirForces Monthly'' reported that by December 2020, just 2 aircraft were available for operations at any one time. The Strategic Defence and Security Review 2015 had announced the intention to retain the E-3D fleet until 2035, however in March 2019, the Ministry of Defence announced that the E-3Ds would be replaced by five E-7 Wedgetails from 2023. The £1.51 billion contract was awarded to Boeing without a competitive procurement process, a decision criticised by both competitors of Boeing and the UK's Defence Select Committee. The 2021 Integrated Defence Review confirmed a reduced order of three aircraft. On 27 January 2015, the RAF deployed an E-3D Sentry to Cyprus in support of U.S.-led coalition airstrikes against
Islamic State The Islamic State (IS), also known as the Islamic State of Iraq and the Levant (ISIL), the Islamic State of Iraq and Syria (ISIS) and Daesh, is a transnational Salafi jihadism, Salafi jihadist organization and unrecognized quasi-state. IS ...
militants in Iraq and Syria. The last operational flight by an RAF E3 Sentry was in July 2021 with the Sentry subsequently retired from service.


France

In February 1987 the UK and France ordered E-3 aircraft in a joint project which saw deliveries start in 1991. France operates its E-3F aircraft independently of NATO. France operates four aircraft, all fitted with the newer CFM56-2 engines. In early 2024, there were reports that France is looking to the Swedish Saab GlobalEye to replace its AWACS aircraft.


Chile

Three Boeing E-3D Sentry (Sentry AEW.1) aircraft, acquired second hand from the United Kingdom in September 2021, arrived in Chile in July 2022; units ZH103 and ZH106 will join the "Grupo de Aviación N.º 10" of the II Air Brigade. The other E-3D will reportedly be used as a source of spare parts.


NATO

NATO acquired 18 E-3As and support equipment, with the first aircraft delivered in January 1982.Wilson 1998, p 75. The aircraft are registered in
Luxembourg Luxembourg, officially the Grand Duchy of Luxembourg, is a landlocked country in Western Europe. It is bordered by Belgium to the west and north, Germany to the east, and France on the south. Its capital and most populous city, Luxembour ...
. The eighteen E-3s were operated by Number 1, 2 and 3 Squadrons of NATO's E-3 Component, based at NATO Air Base Geilenkirchen. NATO E-3s participated in Operation Eagle Assist after the
September 11 attacks The September 11 attacks, also known as 9/11, were four coordinated Islamist terrorist suicide attacks by al-Qaeda against the United States in 2001. Nineteen terrorists hijacked four commercial airliners, crashing the first two into ...
on the World Trade Center towers and the Pentagon. NATO and RAF E-3s participated in the military intervention in Libya. From January 2011 to September 2014, NATO E-3s were deployed to Mazar-i-Sharif International Airport, Afghanistan, as part of NATO's
International Security Assistance Force The International Security Assistance Force (ISAF) was a multinational military mission in Afghanistan from 2001 to 2014. It was established by United Nations Security Council United Nations Security Council Resolution 1386, Resolution 1386 ac ...
(ISAF) mission. The aircraft were used for
air traffic control Air traffic control (ATC) is a service provided by ground-based air traffic controllers who direct aircraft on the ground and through a given section of controlled airspace, and can provide advisory services to aircraft in non-controlled air ...
of military aircraft over the country, as well as surveillance, and tactical management of friendly aircraft. During the mission to Afghanistan, NATO E-3s flew 1,240 missions and accumulated 12,240 flying hours. Presently, 14 NATO E-3As are in the inventory, since one E-3 was lost in a crash and three were retired from service in 2015, 2017, and 2018. The first was due for its six-year cycle Depot Level Maintenance (DLM) inspection which would have been very costly. The "449 Retirement Project" resulted in reclamation of critical parts with a value of upwards of $40 million which will be used to support the remaining active aircraft. Some of the parts to be removed are no longer on the market or have become very expensive.


Variants

;EC-137D :2 prototype AWACS aircraft with JT3D engines, 1 fitted with a Westinghouse Electric radar and 1 with a Hughes Aircraft Company radar. Both converted to E-3A standard with TF33 engines. ;E-3A :Production aircraft with TF33 engines and AN/APY-1 radar, 24 built for USAF (later converted to E-3B standard), total of 34 ordered but the last 9 completed as E-3C.Pither 1998, pp. 40–42 One additional aircraft retained by Boeing for testing, 18 built for NATO with TF33 engines and 5 for Saudi Arabia with CFM56 engines. ;KE-3A :These are not AWACS aircraft but CFM56 powered tankers based on the E-3 design. 8 were sold to Saudi Arabia. ;RE-3A :Three KE-3 airframes delivered as CFM56–powered strategic reconnaissance aircraft. Systems and external appearance are similar to the USAF’s RC-135V/W Rivet Joint platform. At least one of the RE-3As has received the extended "hog nose" as fitted to the RC-135. ;E-3B :USAF Block 30 modification. E-3As with improvements, 24 conversions. ;E-3C :USAF Block 35 modification. Production aircraft with AN/APY-2 radar, additional electronic consoles and system improvements, ten built. ;JE-3C :One E-3A aircraft used by Boeing for trials later redesignated E-3C. ;E-3D :Production aircraft for the RAF to E-3C standard with CFM56 engines and British modifications designated ''Sentry AEW.1'', 7 built. Modifications included the addition of a refueling probe next to the existing boom AAR receptacle, CFM-56 engines, wingtip ESM pods, an enhanced Maritime Surveillance Capability (MSC) offering Maritime Scan-Scan Processing (MSSP), JTIDS and Havequick 2 radios. ;E-3F :Production aircraft for the French Air and Space Force to E-3C standard with CFM56 engines and French modifications, 4 built. ;E-3G :USAF Block 40/45 modification. Includes hardware and software upgrades to improve communications, computer processing power, threat tracking, and others, and automates some previously manual functions. Initial operating capability (IOC) declared in July 2014. It also removed the 1970 vintage mission computing. E-3G(II) Block 40/45 modification that included a glass cockpit modification that reduced the crew size by one, and added a new avionics suite.


Operators

;: The
Chilean Air Force The Chilean Air Force () is the air force of Chile and branch of the Chilean military. History The first step towards the current FACh is taken by Lieutenant Colonel, Teniente Coronel training as a pilot in France. Although a local academy was c ...
purchased three retired E-3D Sentry aircraft from the
Royal Air Force The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...
. ;: The French Air and Space Force purchased four E-3F aircraft. * '' Escadron de détection et de contrôle aéroportés 36 Berry'' (36th Airborne Detection and Control Squadron "Berry") based at Avord Air Base. ; : 18 E-3 AWACS were purchased – 1 was written off in
Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...
, 3 were retired from service. Mainly responsible for monitoring European NATO airspace, they have also been deployed outside the area in support of NATO commitments. The 20 multinational crews are provided by 15 of the 31 NATO member states. * NATO Airborne Early Warning and Control Force – E-3A Component. Based at Geilenkirchen (Germany), with forward operating bases at Konya (Turkey), Preveza/Aktion (Greece) and Trapani/Birgi (Italy) and a forward operating location at Ørland (Norway). ** Aircrew Training Squadron ** Flying Squadron 1 ** Flying Squadron 2 ** Flying Squadron 3 – disbanded in 2015 ;: The Royal Saudi Air Force purchased five E-3A aircraft in 1983. In 2004, modifications began to convert KE-3A tankers into RE-3 electronic intelligence gathering aircraft. * RSAF No. 6 Wing ( Prince Sultan Air Base – Al Kharj) ::''السرب الثامن عشر'' (''al-Sarab al-Ththamin Eshr'' – No. 18 Squadron) ::No. 19 Squadron – RE-3A/B (as well as Beechcraft 350ER-ISR) ::No. 23 Squadron – KE-3A ;: The
United States Air Force The United States Air Force (USAF) is the Air force, air service branch of the United States Department of Defense. It is one of the six United States Armed Forces and one of the eight uniformed services of the United States. Tracing its ori ...
has 21 operational E-3s as of June 2024 :
Tactical Air Command Tactical Air Command (TAC) is an inactive United States Air Force organization. It was a List of Major Commands of the United States Air Force, Major Command of the United States Air Force, established on 21 March 1946 and headquartered at Lang ...
1976–1992 :
Air Combat Command The Air Combat Command (ACC) is one of nine List of Major Commands of the United States Air Force, Major Commands (MAJCOMs) in the United States Air Force, reporting to Headquarters, United States Air Force (HAF) at the Pentagon. It is the prim ...
1992–present * 552d Air Control Wing – Tinker Air Force Base,
Oklahoma Oklahoma ( ; Choctaw language, Choctaw: , ) is a landlocked U.S. state, state in the South Central United States, South Central region of the United States. It borders Texas to the south and west, Kansas to the north, Missouri to the northea ...
:: 960th Airborne Air Control Squadron 2001–present ( NAS Keflavik,
Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...
1979–1992) :: 963d Airborne Air Control Squadron 1976–present :: 964th Airborne Air Control Squadron 1977–present ::
965th Airborne Air Control Squadron The 965th Airborne Air Control Squadron is part of the 552d Air Control Wing at Tinker Air Force Base, Oklahoma. It operates Boeing E-3 Sentry aircraft conducting airborne command and control missions. The first two antecedents of the squadron ...
1978–1979, 1984–present :: 966th Airborne Air Control Squadron 1976–present * 380th Air Expeditionary Wing 2002–present Al Dhafra Air Base, United Arab Emirates :: 968th Expeditionary Airborne Air Control Squadron 2013–present ( Thumrait Air Base,
Oman Oman, officially the Sultanate of Oman, is a country located on the southeastern coast of the Arabian Peninsula in West Asia and the Middle East. It shares land borders with Saudi Arabia, the United Arab Emirates, and Yemen. Oman’s coastline ...
2002–2003) :
Air Force Reserve Command The Air Force Reserve Command (AFRC) is a MAJCOM, major command (MAJCOM) of the United States Air Force, with its headquarters at Robins Air Force Base, Georgia. It is the federal Air Reserve Component (ARC) of the U.S. Air Force, consisting of ...
* 513th Air Control Group (Associate) – Tinker AFB, Oklahoma :: 970th Airborne Air Control Squadron 1996–present (Personnel only, aircraft loaned by co-located 552nd ACW as needed) * 413th Flight Test Group – Robins AFB, Georgia :: 10th Flight Test Squadron – Tinker AFB, Oklahoma 1994–present : Pacific Air Forces * 3d Wing – Elmendorf AFB,
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
:: 962d Airborne Air Control Squadron 1986–present *
18th Wing The United States Air Force's 18th Wing is the host wing for Kadena Air Base, Okinawa, Japan and is the Air Force's largest combat wing. It is the largest and principal organization in the Pacific Air Forces Fifth Air Force. The Wing's 18th ...
– Kadena AB, Japan :: 961st Airborne Air Control Squadron 1979–present


Former operators

;: The
Royal Air Force The Royal Air Force (RAF) is the Air force, air and space force of the United Kingdom, British Overseas Territories and Crown Dependencies. It was formed towards the end of the World War I, First World War on 1 April 1918, on the merger of t ...
purchased seven E-3Ds by October 1987, designated ''Sentry AEW.1'' in British service. As of December 2020, only three remained in service after one was withdrawn from service in 2009 to be used as spares, two were withdrawn in March 2019 and a further one withdrawn in January 2020. The fleet had been given an out of service date (OSD) of December 2022. They formed the E-3D Component of the NATO Airborne Early Warning and Control Force. However, that date was accelerated pursuant to the 2021 defence review and the aircraft made its final flight in U.K. service in August 2021. * RAF Waddington,
Lincolnshire Lincolnshire (), abbreviated ''Lincs'', is a Ceremonial counties of England, ceremonial county in the East Midlands and Yorkshire and the Humber regions of England. It is bordered by the East Riding of Yorkshire across the Humber estuary to th ...
, England :: No. 8 Squadron (1991–2021) :: No. 23 Squadron (1996–2009) :: No. 54 Squadron (Operational Conversion Unit 2005–?) :: No. 56 Squadron (Operational Evaluation Unit 2008–?)


Incidents and accidents

E-3s have been involved in three hull-loss accidents, and one radar antenna was destroyed during RSIP development (see photo under Avionics). * On 22 September 1995, a U.S. Air Force E-3 Sentry (callsign Yukla 27, serial number 77-0354), crashed shortly after takeoff from Elmendorf AFB, Alaska. The plane lost power to both left side engines after ingesting several Canada geese during takeoff. The aircraft went down about northeast of the runway, killing all 24 crew members on board. * On 14 July 1996, a NATO E-3 Sentry (tail number LX-N90457) overran the runway and crashed into a sea wall at Preveza-Aktion Airport in Greece when the pilot attempted to abort takeoff after mistakenly believing that the aircraft had suffered a bird strike. The aircraft overran the runway and struck a sea wall, where it came to a halt. There were no injuries and the aircraft was written off. Investigators could find no evidence that a bird strike and ingestion had occurred. * On 28 August 2009, a U.S. Air Force E-3C Sentry (serial number 83-0008) participating in a Red Flag exercise at
Nellis Air Force Base Nellis Air Force Base ("Nellis" colloquialism, colloq.) is a United States Air Force military installation, installation in southern Nevada. Nellis hosts Aerial warfare, air combat exercises such as Exercise Red Flag and close air support exerc ...
, Nevada experienced a nose gear collapse on landing, resulting in a fire and damaging the aircraft beyond repair. All 32 crew members evacuated safely.


Specifications (USAF/NATO)


See also


References

Notes Citations Bibliography * * * * * * * *


External links


Royal Air Force E-3 Sentry information

NATO AWACS-Spotter Geilenkirchen website

Airborne Early Warning Association website
{{Authority control Aircraft first flown in 1972 AWACS aircraft E-03 Sentry Boeing 707 E-03 Sentry Quadjets 1970s United States military reconnaissance aircraft 1970s United States command and control aircraft Low-wing aircraft Aircraft with retractable tricycle landing gear