David C Isby reviews the US Air Force upgraded E-3G Sentry and its international counterparts


Upgraded US Air Force Boeing E-3G Block 40/45 Sentry Airborne Warning and Control System (AWACS) aircraft have carried out combat missions in the Middle East, airspace monitoring in Eastern Europe and the western Pacific and guided interceptors to Russian bomber fly-bys in international airspace.

An upgrade package developed by Boeing dubbed Block 40/45 is at the heart of the changes that transform earlier E-3 models to E-3Gs, increasing capabilities and reliability and reducing sustainment costs.

The Department of Defense’s FY2016 Annual Report by J Michael Gilmore, Director, Operational Test and Evaluation details the Block 40/45 upgrade as replacing the mission computing system with openarchitecture, commercial off-the-shelf hardware including servers and 15 mission crew interactive operator workstations, and includes a new mission computing software program; a set of local area networked, open architecture programs. The human-computer interface is built on the Windows operating system and licenses the Raytheon Solipsys Tactical Display Framework.

The E-3G’s mission computing system provides the capability to automatically fuse all on- and off-board sensor inputs to provide a single track for each air, sea, and land entity using a multi-sensor integration algorithm.

Jim Haseltine

The upgrade is also intended to provide:

- An update to the Link 16 and satellite communications capabilities

- Software to automatically refresh the onboard database

- An updated mission system health monitoring tool

- Improved interfaces and controls of the onboard electronic support measures (ESM) system

- Improved mission planning and postmission processing capabilities

- A deployable ground support system to enable deployed crews to conduct mission planning and post mission processing with a central data processing centre for data storage and retrieval.

The basic Boeing 707 airframe and Northrop Grumman APY-2 radar remain unchanged.

E-3Gs will remain in US Air Force service to 2035, though their 40,000-flight hour airframe service life could enable them to fly on to 2050. What type of aircraft replaces the E-3 is already being considered by the US Air Force. The Block 40/45 upgrade – along with a new cockpit – is either being adopted or considered by NATO (currently operating 16 aircraft), the United Kingdom (6), Saudi Arabia (5) and France (4), plus Japan (four similar Boeing E-767 AWACS).

G Model Origins

Flight-testing of the first Block 40/45 E-3G started in July 2006, progressed through mission systems testing from April 2007 and was completed by August 2008. The E-3G entered low-rate initial production (LRIP) in November 2010 when E-3B serial number 82-0007 entered the modification line at Oklahoma City Air Logistics Complex. Fullrate production started at the end of 2012. When the E-3G achieved initial operational capability (IOC) on July 28, 2015, with five operational aircraft, 552nd Airborne Control Wing Commander, Colonel Jay Bickley said the E-3G represents the most significant upgrade in the 35-plus year history of the E-3 AWACS. He said: “It greatly enhances our crew members’ ability to execute the command and control mission while providing a building block for further upgrades.”

Operational missions flown by an E-3G were first flown with US Northern Command (homeland air defence) and Southern Command (counterdrug interdiction). Starting with Red Flag 14-1 and Northern Edge 2015, such exercises soon demonstrated the capabilities of the E-3G. During Northern Edge 2015, two E-3Gs simultaneously monitored and controlled nearly 100 combat aircraft over a 300-mile (480km) radius.

At Clark Field in the Philippines during Exercise Balikatan in May 2015, Philippine Air Force controllers directed aircraft from on board an E-3G. In the Trilateral exercise, held at Langley Air Force Air Force Base Virginia in December 2015, E-3Gs operated in a networked coalition environment with British and French aircraft.

Despite extensive operational commitments, US Air Force E-3Gs took part in a number of multinational exercises. At Red Flag 16-1 in February 2016 – its second Red Flag appearance – E-3Gs demonstrated their ability to operate with Royal Australian Air Force E-7A Wedgetail airborne early warning aircraft. During Red Flag 16-2 in March, E-3G crews found the improved human machine interface of the mission systems and the enhanced playback capabilities especially valuable. A Block 40/45 Sentry operated with Republic of Korea and Japanese forces for the first time during Exercise Max Thunder in May 2016, when an E-3G from Tinker Air Force Base deployed to Okinawa and fiew nine missions. Through July and August 2016 during Exercise RIMPAC (Rim of the Pacific), E-3Gs were electronically linked to US Navy and coalition warships, F-22 Raptors and US Navy P-3C Orion patrol aircraft.

E-3 AWACS aircraft have been deployed to the US Central Command area of responsibility continually since 2007, as they previously were from 1990 to 2003.

The first E-3G combat mission, on November 28, 2015, monitored Syrian and Iraqi airspace: that year the E-3G achieved a mission capable rate of 83%, compared with 76% for the E-3C. Reliability of the E-3G’s sensors and mission systems – always an issue – was considerably better than that of earlier versions.

Jim Haseltine


The E-3G programme continues on track to deliver the 17th aircraft by the end of FY2017. By FY2020, all 24 aircraft currently in the US Air Force plan to be upgraded to full E-3G standard will be complete, including the LRIP aircraft (which lacked some on board equipment) to the common baseline configuration.

Originally, the US Air Force planned to upgrade all of its 31 operational and one developmental E-3s to E-3G standard. Funding limitations led to the programme being cut back to 24 aircraft. The smaller quantity raised the unit cost to $111 million (total cost $2.6 billion) in then-year dollars, which breached the Nunn-McCurdy amendment requirements, requiring the Department of Defense to notify Congress why the cost had gone up in this way or to cancel the programme.

The US Air Force FY2015 budget request included a proposal to retire immediately the seven E-3s that would not be upgraded and disbandment of the 513th Air Control Group, an Air Force Reserve Command unit that provides aircrew and technicians to support worldwide deployments of the E-3 AWACS. The proposal encountered Congressional opposition, especially from the Oklahoma delegation. Oklahoma is the home of Tinker Air Force Base where the Block 40/45 upgrades are carried out using Boeing-produced kits and all but four of the fleet are based at Tinker (two are based at Elmendorf Air Force Base, Alaska and two at Kadena Air Base on Okinawa).

As a result, AWACS divestiture has been limited by Congressional action, and the US Air Force has postponed an AWACS force structure reduction until FY2019.

Speaking to the Senate Armed Services Committee on March 8, 2016, Lieutenant General Mike Holmes, then deputy chief of stafffor strategic plans and requirements, said plans remain so the air force can draw down a portion of its fleet to make money available to upgrade the rest of the fleet to be effective for the combatant commanders.

Operating Block 30/35 AWACS alongside Block 40/45 aircraft is considered an unacceptable solution, as it would require two separate pipelines for spares and training and would provide operational commanders with two differing capabilities. Plans for a comprehensive AWACS sustainment and modernisation programme were scrapped in 2015 as unaffordable.

After the AWACS

The US Air Force is looking at potential AWACS replacements. In October 2015, its Office of Transformational Innovation studied whether buying an off-the-shelf twin-engine jet for the AWACS mission would save money and found that airframe cost savings would only be a fraction of the costs of the sensors and system migration and integration.

Nor would a new airframe address the emerging problem of vulnerability to new-generation weapons. The US Air Force’s recent Air Superiority 2030 Flight Plan identified long-range air and surface launched missiles, directed energy and electronic and cyberwarfare attack as forcing AWACS to stand offat greater range. Brigadier General Alexus Grynkewich, director of the study, said: “Instead of building another AWACS with limited reach into contested airspace and not necessarily survivable, a different solution would be to stitch together ISR [intelligence, surveillance and reconnaissance] feeds from F-22 and F-35 and other platforms to give you the blue operation picture.”

Another, more survivable (and potentially unmanned) sensor platform might be required to work closer to the threats and relay sensor-gathered information back by datalink for fusion and analysis.

A potential AWACS replacement, designated the Advanced Battle Management and Surveillance (ABMS) programme – which could be a single manned or unmanned platform or a network incorporating multiple remote sensors – would not appear until after 2030. An analysis of alternatives study for the ABMS is scheduled to conclude in late FY2018. Another upcoming study, modelled on the Air Superiority 2030 Flight Plan, will look at US Air Force command and control as a whole, studying the broader context of an AWACS replacement decision.

Workers at the Oklahoma City Air Logistics Center, install components on an E-3 Sentry as part of the Block 40/45 upgrade during programmed depot maintenance.
A US Air Force airman navigates an E-3G for a mission above the Joint Pacific Alaska Range Complex during Exercise Northern Edge 2015. Chief Petty Officer Larry Foos/US Navy


Replacing the old-technology hardware found on earlier Block configurations allowed the Block 40/45 upgrade to increase the number of mission system operator workstations from ten to 15. Operator workload has been reduced by automation: processes previously undertaken manually are now performed automatically, thanks to improved systems interface capabilities, including software that automatically refreshes on-board databases.

An integrated net-centric capability replaces old and no longer sustainable mission systems with a new suite of flatscreen computers that enhance tracking and combat identification capabilities, improve mission effectiveness and system reliability and lower life cycle costs. The E-3G’s open-architecture mission computer system (50 linked computers running 24 types of mission software) uses improved battle management tools. This allows the mission crew to access air tasking order and airspace coordination order data in flight, improving the ability to flexibly re-task coalition airpower. The Block 40/45 upgrade includes a networked multi-spectral sensor system; Boeing’s AYR-2 ESM system, mounted in the cheek canoe fairings, replaces the earlier AYR-1 integrated as part of the earlier Block 30/35 upgrade; and the datalink infrastructure prioritises bandwidth between the Block 40/45’s Situational Awareness Data Link (SADL), Link 11, Link 16 and Link 22 systems.

New mission crew workstations on the E-3G provide crew with greater levels of automation to help them fight each air battle. US Air Force

The open architecture computer system’s improved human-machine interface uses sensor integration algorithms to create the multi-sensor integration that automatically fuses data from the E-3G’s radar, ESM and IFFwith off-board sensor inputs from a wide range of platforms to generate a single track and identification for each air, sea and land target. For many years the holy grail of battle management, single target/single track capability was a key performance parameter of the Block 40/45.

An E-3G cockpit fitted with the DRAGON flight deck, the first of 24 AWACS aircraft configured with the system. Kelly White/US Air Force

According to Vice Admiral Mike Shoemaker, the US Navy’s air boss, the United States has recognised that to fight and win in a future networked air battle, the key piece is longrange combat identification.

To meet this requirement, the Block 40/45’s Mode 5 and Mode S compatible Telephonics UPX-40 NGIFFinterrogator system can identify and position aircraft or ships as friendly or unknown, as well as determine their bearing and range. The UPX-40 can also distinguish multiple targets in close proximity, including military aircraft flying in close formation with civil aircraft. Replacing the earlier APX-103C, the UPX-40 provides threat identification of multi-sensor tracks from birth to death, including manoeuvring, stealthy and low-flying targets. It can start tracking an aircraft while it is still taxiing at its base and follow it as a single track regardless of evasive tactics or countermeasures. First installed in 2015, the UPX-40 will be retrofitted fleet wide, including to the six LRIP E-3Gs, by 2020.

DRAGON on the Flight Deck

A communications, navigation and surveillance/air traffic management (CNS/ATM) upgrade package for the NATO E-3 AWACS force was developed jointly with the US Air Force DRAGON (derived from Diminishing manufacturing sources Replacement of Avionics for Global Operations and Navigation) programme with some 95% commonality, but under different production contracts. DRAGON is not part of Block 40/45, but requires the upgrade’s computer open architecture.

Designed by Boeing, the three-place flight deck (there is no navigator) is compliant with global air-traffic management standards and replaces analogue instrumentation with full-colour digital displays. It includes an upgraded weather radar and ground proximity warning system.

The new cockpit was first flown on E-3A AWACS N-1 (LX-N90459), the NATO technology demonstration aircraft at Boeing Field, Seattle on April 20, 2015. The US Air Force developmental aircraft D-1 (77-0351) was installed at the company’s facility at Boeing Field during 2014 and 2015. Upon completion of testing, the aircraft returned to Tinker Air Force Base on January 9, 2017. Under current plans, the US Air Force will configure all 24 E-3Gs with a DRAGON standard flight deck over the next eight years: the first LRIP contract for five aircraft is expected to be issued this year. A contract to reconfigure the AWACS flight simulator at Tinker with a DRAGON standard flight deck was awarded to L-3 Corporation in July 2016.

International AWACS

NATO is the largest E-3 AWACS operator outside of the US Air Force. In addition to airspace monitoring along Europe’s eastern and southern borders, NATO AWACS fiew 1,240 sorties during a three-year operational tasking to Afghanistan between 2011 and 2014. At a NATO summit in Warsaw last year, NATO Secretary General Jens Stoltenberg announced NATO’s intent to operate NATO E-3 aircraft over Turkey and in international airspace to monitor Syria and Iraq and support coalition air operations, but not participate in combat against the so-called Islamic State: missions started in October 2016.

NATO awarded Boeing a contract to upgrade 14 of its 17 E-3A aircraft (the force size is being reduced as a result of Canada withdrawing from the programme). In addition to the CNS/ATM cockpit, aircraft will receive NATO-specific Mode 5 and Enhanced Mode 5 IFFtransponder upgrades, secure communications, and the capability to receive data feeds from NATO’s RQ-4 Global Hawk unmanned air vehicles, as demonstrated during Exercise Unified Vision back in 2014.

Last year, CNS/ATM integration work started on the second aircraft, and NATO hopes to have funding available to start the Block 40/45 upgrade in 2018. Valued at $4.1 billion, the Block 40/45 upgrade programme would keep NATO’s E-3 fleet operationally viable through to the mid-2030s, although the current commitment to operate the force continues only to 2025.

Jim Haseltine

During a June 2016 meeting in Brussels, NATO defence ministers approved a planning mandate for the Alliance Future Surveillance and Control (AFSC) programme costing an estimated $8 billion to procure the replacement for the E-3A after 2025.

A 2015 study from NATO’s Industrial Advisory Group recommended adopting a distributed system of networked airborne sensors rather a single aircraft design. Spacebased solutions were seen as too costly and technologically risky to meet NATO needs.

All four Armée de l’Air E-3Fs were upgraded to Block 40/45 standard at the Air France- KLM Engineering & Maintenance facilities at Le Bourget and Charles de Gaulle airports in Paris using Boeing-supplied kits. Flight testing was conducted from BA702 Avord.

The first aircraft left Avord on January 31, 2014; the Centre d’Expertises Aériennes Militaires (Military Aviation Test Centre) received the upgraded aircraft for certification on August 1, 2014; and the modernized E-3F was declared operational with Escadrille Opérationnelle 1/36 on March 1, 2015 when combat missions were under way in the Middle East. All four upgrades were complete by July 2016. The French also intend to participate in the CNS/DRAGON upgrade, but have not yet signed a contract.

In 2015, Armée de l’Air Chief of StaffGeneral Denis Mercier said France was also looking at acquiring an AWACS replacement post-2030.

Saudi Arabia completed upgrading its five AWACS to Block 40/45 including Link 16 compatible connectivity to US and coalition platforms, so data can be shared with the Saudi ground air defence system. Negotiated in August 2014, the $2 billion programme was completed by the end of 2016.

Then there’s the UK. Six of the seven E-3D Sentry AEW1 aircraft will be upgraded from 2020 to extend their service life by ten years to 2035: the plan was announced as part of former Prime Minister Cameron’s 2015 Defence and Security Review. Shrouded in the UK’s standard level of non-disclosure, details about the UK AWACS upgrade remain unknown, though it will likely bring all six aircraft up to a configuration similar to Block 40/45 and include the CNS/DRAGON flight deck. Nothing in the UK’s arsenal is ever standard, none more so than the modifications expected for the Sentry AEW1, which will refiect its unique ESM system and radar maritime scan-to-search capability.

In addition to their air-to-air radar capability, Japan’s four E-767 AWACS share a maritime surveillance capability similar to the RAF’s E-3Ds. The E-767s are being upgraded with a package similar to the Block 40/45 by Boeing under a programme started in 2014.

AWACS Upgrades

Upgrading military aircraft is less popular than new production, both with those in uniform and those in industry. Yet the E-3G shows that an upgrade programme can provide years of additional capability for a fraction of the costs associated with AWACS operation, let alone a replacement. US Air Force, NATO and RAF E-3 fleets are all shrinking in size despite the fact there is no shortage of missions for them, because, no matter how modified, the 1950s era airframe design is expensive to operate.

Missions being flown by NATO AWACS on the alliance’s troubled border with Syria and Iraq since October are the latest example of the continued importance of these aircraft. In addition to being a vital element of airpower, AWACS deployments – over the United States after the 2001 terrorist attacks, Afghanistan and NATO’s eastern frontiers – have added to overall coalition situational awareness, as well as providing a strong diplomatic message while avoiding the appearance of an armed threat inherent with using fighters or bombers in such missions.

The long-term question, whether there needs to be a replacement aircraft for the E-3 AWACS or whether networks of distributed sensors and battle management nodes will be able to do its job better in the post-2035 world, has not been resolved and upcoming studies by the US Air Force are likely to provide only a first cut of the answer to the question.