Boeing E-3 Sentry

Boeing E-3 Sentry is the military designation for a Boeing 707-320, which is as AWACS reconnaissance aircraft by the air forces of several countries in use. The most striking external feature is the AN/APY-1-Suchradar above the fuselage.

  • 2.1 Overview of variants
  • 3.1 Specifications
  • 3.2 RSIP upgrade
  • 3.3 operating Modes



In the 1960s, a successor to the EC- 121 "Warning Star" was searched as part of a program to develop new technologies for an airborne surveillance system by the U.S. Air Force, at the radar system both Hughes and Westinghouse worked. As a carrier jet aircraft was planned; so struck Douglas as a base, the DC -8 -60 and Boeing 707- 320B before. The latter was chosen with four TF33 engines in July 1970, the two prototypes were fitted for comparison test of the two radar systems due to time constraints with four TF33 - ( JT3D ) engines. The first flight of the two machines designated as EC - 137D took place on 9 and 10 February 1972, the following flight test lasted until September 1972 from the Westinghouse AN/APY-1-Radar emerged as the winner. The following from January 1973 official development of the new AWACS system ran under the name E-3A Sentry. The first flight of the first Vorserienmodells was July 21, 1975 and it was decided that the production model to be equipped with four engines. Began in March 1977, the equipment of the 552nd Airborne Warning and Control Wing at Tinker AFB (Oklahoma ) with the first 22 production aircraft (known as " Core" standard referred to ) and the two prototypes and two pre-production aircraft. In the first half of the 1980s, a further eight machines were provided with AN/APY-2-Radar into service in an improved " standard " version.

Introduction to NATO

At the Ministerial meeting of the Defence Planungsauschusses NATO on 5 and 6 December 1978 in Brussels, ministers adopted the program for the flying NATO early warning and control system and signed an appropriate multilateral agreement in principle. With the Airborne Warning and Control System ( AWACS ), Member States called the largest commonly funded acquisition program, which was previously carried out by NATO.

Beginning of the 1970s gave the Supreme NATO commander order studies, showing that the existing fixed systems no longer provide effective air defense of the continental European area: So the Warsaw Pact already had fast-moving aircraft that were able to for example, at low altitude to escape the far-reaching radars; there was still a risk that the systems could be stationed laid off by electronic warfare ( electronic warfare ), and location also determines the warning period was limited to about a half hour. In NATO command area of ​​the SACEUR was to collect from mobile systems, for example, the ability to clear up early, smaller attack groups and to be able to use your own interceptor radar adequately supported.

The first machines of the type E -3A, also known as NE -3A designated (N for NATO), came from February 24, 1982 at the NATO Air Base in Geilenkirchen used previously in the U.S. in March 1977., The aircraft for the NATO were equipped with the Dornier plant in Oberpfaffenhofen and later still cared. Today, the technical support of the NATO aircraft in Manching plant of EADS takes place. Here is an ESM system has been upgraded in recent years to recognize the two antenna bumps on the left and right side of the forward fuselage.

The contract for operating the AWACS is the NATO Airborne Early Warning and Control Programme Management Organisation ( NAPMO ), the total for the planning, implementation and management of the Airborne Warning and implementation program of the NATO (English NATO Airborne Early Warning and Control Programs, Naew & C ) is responsible. It is directly subordinate to the North Atlantic Council, based at NATO headquarters in Brussels ( SHAPE).

The systems used by various NATO nations and NATO itself. The 17 NATO-owned machines have a single aircraft of Luxembourg and stationed at the Air Base Geilenkirchen near Aachen, on behalf of the NATO flying from the RAF base RAF Waddington. France has deployed its machines in Avord. In addition were the end of 2011 on the base in Geilenkirchen three training machines without an antenna, so called TCA ( Trainer and Cargo Aircraft). During the Cold War, the system has fulfilled the function of early warning of low-flying aircraft of the Warsaw Pact.


The 17 NATO E-3A Airborne Early Warning & Control Force were modernized as part of the NATO Mid-Term Program for $ 1.6 billion of Boeing ( prime contractor ) and EADS. The computer system for processing of the recorded radar data was done by totally replaced by COTS computer and a Unix-based server-client network. On 2 December 2008, the 17th and last machine had gone through the conversion and was officially adopted in a ceremony in Geilenkirchen.

Due to the outdated drive technology, the AWACS NATO flying machines partially covered by a dispensation, since the engines of the E-3A no longer meet modern environmental standards related to noise and exhaust fumes. The UK (E -3D) and French version (E -3F ), however, were equipped with more modern engines. These concepts are currently at the E-3A NATO also in the exam, a reaction so far failed again and again to resistances of individual nations who wanted to deposit any money for this technology. All decisions regarding the Naew -NATO E-3A Component can be implemented only with the unanimous agreement.

The B and C versions of the U.S. Air Force will receive over the next few years based on NATO Mid-Term in the so-called Block 40/45, a new communication and electronic equipment and are then referred to as E- 3G. An exact date for the conversion is not fixed yet.


Since the basic model Boeing 707 and its variants are no longer produced since the early 1990s, the U.S. Air Force and other interested parties such as Japan use since the Boeing E -767 as a reconnaissance platform. The envisaged for the USAF successor model E-10, however, was stopped for reasons of cost for now. Therefore, the United States Air Force plans (USAF) to keep some of the 33 machines until after 2025 in the service.


The standard version of the Sentry is officially known as E-3A " Core" or "standard". Most machines of the U.S. Air Force were modernized in the 1980s and referred to as E -3B (block 20). These contained except the new AN/APY-2-Radar, CC2 - computers, new radios and now 14 operator consoles. Starting in 1987, further modernized aircraft complied with the block -30 standard. In the course of further modernization, many of the aircraft were given new CFM engines and the name E -3C (block 25 or block 35 ). In the late 1980s Boeing developed together with British Aerospace a modernized version of the Sentry for the Royal Air Force of Great Britain, the E- 3D Sentry AEW Mk.1. This was (as well as the E-3A machines for Saudi Arabia), the more powerful engines CFM International CFM56, and an apparatus for aerial refueling, which the Sentry can be fueled by both American as well as European tanker aircraft because they use different systems. In addition, the range of applications has been extended. Eight E-3A were put on the E -3C standard. Parallel to the E- 3D, the E -3F was developed for France, this differs only in a few details. The latest versions ( as of 2008 ) are the Block-40/45-Modelle, the modernized computer and contain data link systems.


Radar system

The approximately 3.6 -ton AN/APY-1-Suchradar dominates the skyline of the E-3. It is in a large 3.35 m radome placed over the hull, which has a diameter of 9.1 meters and a thickness of up to 1.8 meters. The system can detect and track, even if they fly very low ( low level flight ) or only a small radar cross section have air targets of all kinds (including fighter jets, helicopters and cruise missiles ). Similarly, ships at sea can be elucidated, this ability has been fully integrated only with the APY - 2 variant. The antenna is mechanically aligned in azimuth by rotation, in elevation electronically (28 phased array antennas on ferrite basis).


  • Diameter: 9.14 m
  • Height: up to 1.8 m
  • Weight: 3629 kg
  • Frequency range: 2-4 GHz
  • Number of Transmitters: 28
  • Antenna rotation time: 10 s
  • Range: about 460 km ( 400 km at low-flying targets up to 520 km for targets at medium altitude )

RSIP upgrade

The RSIP upgrade ( " Radar System Improvement Program " ) provides a comprehensive combat efficiency of APY-1/2-Radars dar. Thus, the range resolution could be increased by six times and the angular resolution doubled. The ECCM capabilities were significantly expanded. Also improvements have been made in terms of operability and reliability. The detection range was increased by 70-100 % and is at least 300 nm ( 556 km ) amount against a target with a radar cross section of 0.5 m².

Modes of operation

The radar has a number of operating modes which can be selected depending on the situation. The following are the main modes, which are available since the RSIP upgrade.

  • Pulse Doppler scan Nonelevation ( PDNES ): This is the default mode to detect air targets. Due to the Doppler filter also small targets against a background of intense clutter can be reliably detected. However, this mode does not provide altitude information to the destination.
  • Pulse Doppler Elevation Scan ( PDES ): Similar to the PDNES mode, but allows the height determination by a rapid vertical search through.
  • Beyond -the- Horizon ( BTH ): This mode is used to very long ranges to achieve. This is achieved by switching off the Doppler filter. However, it is now almost impossible to detect targets in a clutter environment. Therefore, in this mode, only the air space is scanned which is situated above the visible horizon of the radar.
  • Interleaved: Combines the PDES - and BTH- mode, the signal processing is heavily used, so that very small targets may not be able to be reliably located.
  • Maritime: mode to search for large and small sea targets. For this purpose, the pulse duration ( transmission time ) is greatly shortened to suppress clutter as possible by waves. In coastal areas of mainland disappears automatically based on digital maps. The PDNES mode can be used simultaneously.
  • Passive: In this mode there are some or all of the 28 antenna units in passive ELINT mode. This targets can be detected and tracked based on their radar emissions, without the E-3 revealed by emissions themselves. Furthermore, can be sources of interference with individual antenna elements accurately captured, analyzed, and hidden, the other elements can actively work on the basis of information obtained ECCM.


The number of crew aboard NATO AWACS is usually 16 soldiers from various NATO states divided over the so-called Flight Deck and the mission deck. Composed of:

The crew of Flight Deck directs the aircraft and is responsible to bring the machine in the correct use of space (the correct pattern). The mission deck cares about the actual tasks, thus creating air situation and tactical support of fighters and battle planes by radio and Data Link. In Europe, the Flight Deck to report to other participants with the mission callsign " NATO XX", the mission deck with " MAGIC XX". XX represents the mission number, the number of mission -Call Signs always by 50 is greater than that of NATO callsigns (eg NATO and 01 MAGIC 51).

As part of the modernization of the mission system on the NATO Mid-Term Level the composition of the crew has been changed. The Flight Deck is the same, with the mission - crew there were the following changes: From the DT ST has become (System Technician ) and the CO has been dropped. Thus, the original 17 -strong crew has shrunk to just 16.




  • On 22 September 1995 crashed on Elmendorf Air Force Base in Anchorage, Alaska, an American Boeing E-3 (call sign: Yukla 27 ) from. Unfortunately it came after geese got into the engine. Here, 25 crew members, including one Canadian died.
  • On July 14, 1996 E-3A (LX - N90457 ) NATO rolled beyond the runway of the air base Preveza (Greece ) and sank into an adjacent lake. Although the machine was destroyed in the process, all 16 crew members were saved. The cause of the accident bird strike was suspected, but which has never been proven.
  • On 28 August 2009 an E -3C, USAF (S / N 83-0008 ) was damaged on landing at Nellis Air Force Base after the nose gear had failed. The thereby induced fire destroyed the machine completely. This was caused by a pilot error during the landing maneuver.

Similar types

  • Embraer R- 99A (EMB - 145SA with same Eriye radar as Saab 340AEW )
  • KongJing -2000 " Mairing " ( Il -76 AWACS )
  • KJ -200 ( Shaanxi Y -8 AWACS )
  • Avro 696 AEW Mk.2 " Shackleton "
  • Boeing 737 AEW & C ( Boeing 737- 700ER AWACS )
  • Grumman E-2C / D " Hawkeye "
  • Berjew A- 50A " Mainstay "
  • Tupolev Tu -126 " Moss" (now decommissioned )
  • Saab 340B AEW -300 ( S- 100D " Argus " with Erieye radar system )
  • Saab 2000 Erieye AEW & C