During World War II, as Nazi Germany’s Focke-Wulf Fw 200 Condor long-range reconnaissance bombers threatened the safety of vital naval convoys, the United Kingdom (U.K.) equipped a Vickers Wellington bomber with a rotating Yagi-Uda radar antenna array to detect them. The modified Wellingtons later were used to direct Royal Air Force (RAF) fighters against Heinkel He 111s that were air-launching V-1 flying bombs, and “E-Boats,” wooden-hulled fast attack boats.

These “Air-Controlled Interception” aircraft were the first to merge two still relatively new technologies – radar and large aircraft. The resulting mobility greatly extended the ability and range of Allied aircraft to detect and destroy some of World War II Germany’s most advanced and effective weapons.

While using airborne radar to detect enemy air and surface assets and warn friendly forces about them marked a significant advance in modern warfare, the military also wanted to put a command and control (C2) capability aloft to improve its efforts to counter Japanese kamikaze attacks in the Pacific.

In February 1944, the U.S. Navy initiated Project Cadillac, in which an AN/APS-20 radar was mounted beneath the fuselage of a modified TBM Avenger torpedo bomber (TBM designated GM-built aircraft). It successfully detected low-flying aircraft at ranges exceeding 100 miles, and the Navy ordered production of about three dozen TBM-3Ws, which in March 1945 became the first production airborne early warning (AEW) aircraft to enter service.

While using airborne radar to detect enemy air and surface assets and warn friendly forces about them marked a significant advance in modern warfare, the military also wanted to put a command and control (C2) capability aloft to improve its efforts to counter Japanese kamikaze attacks in the Pacific. The resulting PB-1W, built on a modified B-17 fuselage, used the same radar as the TBM-3W, but brought aboard several additional operators, who used radio signals to guide defending fighters to their targets.

 

Post World War II Developments

After World War II, efforts to further improve airborne early warning and control (AEW&C) continued, both as dedicated aircraft and as secondary capability retrofits, such as placing an AN/APS-20 radar on a Grumman AF-2W Guardian. That, in turn, led to installation of a large belly radome and the same radar on the Douglas Skyraider attack aircraft. There eventually were three versions of the Skyraider AEW – the AD-3W, AD-4W (supplied to the Royal Navy) and AD-5W (later renamed the EA-1E).

As retrofit Skyraider variants, all had technical limitations, but lessons learned from them and the other U.S. and U.K. AEW and AEW&C projects were the foundation for development of advanced and specialized aircraft, including the U.K.’s Fairey Gannet AEW and the Lockheed Warning Star. Based on the Lockheed Super Constellation, more than 200 entered U.S. Navy and Air Force fleets as the WV-2 and EC-121.

In an historic operation in October 1967, a USAF EC-121 set the stage for many future AEW developments when one of its airborne controllers successfully guided a U.S. fighter to intercept a North Vietnamese MiG-21 over the Gulf of Tonkin.

In an historic operation in October 1967, a USAF EC-121 set the stage for many future AEW developments when one of its airborne controllers successfully guided a U.S. fighter to intercept a North Vietnamese MiG-21 over the Gulf of Tonkin. Throughout its career, the Warning Star was used to test and evaluate experimental radar and other electronics, including a prototype of what eventually became the radome and other systems on the E-3 Sentry AWACS (Airborne Warning and Control System).

A modified Boeing 707-320 commercial airframe with a rotating 30-foot-diameter radar dome mounted above the fuselage, the E-3’s Doppler radar subsystem greatly expanded the Air Force’s surveillance regime – from the Earth’s surface into the stratosphere, over both land and water.

The E-3 can present position and tracking information on both enemy and friendly aircraft and ships in real-time to local air, ground, or naval C2 centers and to the National Command Authority. E-3 on-board operators perform surveillance, identification friend or foe (IFF), weapons control, and battle management and communications functions, while providing information needed for interdiction, reconnaissance, airlift, and close air support.

The post-World War II Soviet Union pursued its own AEW and AEW&C capability. In 1958, the Tupolev Design Bureau was ordered to develop a Soviet AEW aircraft, primarily to patrol the USSR’s vast northern coast and land mass, which would have been far more costly using ground-based radars. The resulting Tu-126 “Moss” used a four turboprop Tu-114 fuselage equipped with an air-to-air refueling capability for extended range. Conflicts between the Tu-114’s large contra-rotating propellers and the original Liana radar soon led to introduction of the Shmel (Bumblebee) surveillance radar.

The E-3 can present position and tracking information on both enemy and friendly aircraft and ships in real-time to local air, ground, or naval C2 centers and to the National Command Authority. E-3 on-board operators perform surveillance, identification friend or foe (IFF), weapons control, and battle management and communications functions, while providing information needed for interdiction, reconnaissance, airlift, and close air support.

Western intelligence rated the Moss inferior to its American counterpart. While effective over water, its performance over land was poor, leading to its replacement in 1984 by the Beriev A-50 “Mainstay,” based on an Ilyushin Il-76, powered by four turbojet engines and equipped with a large disk radome on the rear fuselage. The original Mainstay SDRLO (Long Range Detection System) was able to control up to 10 fighter aircraft in air-to-air or air-to-ground missions and track up to 50 targets simultaneously within a 140-mile radius, and large targets such as tankers or aircraft carriers at distances of 240 miles.

The A-50U variant, with an upgraded Vega Shmel radar, began to enter the Russian fleet in 2011. It also features a new digital avionics suite, faster data processing, enhanced signal tracking and improved target detection. Further development of those upgrades, along with a new Vega Premier active phased array radar, will be incorporated into the next generation Russian AEW&C, based on a new IL-76MD fuselage powered by four PS-90A76 turbojet engines.

As the Cold War reached its peak, the United States and the USSR emerged as the only two nations producing large, four-engine platforms, with both finding ready international markets. The E-3 AWACS and A-50 AEW&C remain in service – and, through upgrades to both the aircraft and systems, no doubt will continue to do so for many more years to come – not only in the United States and Russia, but with half a dozen allied militaries.