Boeing E-3 Sentry
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Date: 2018-12-21

Boeing E-3 Sentry, by Wikipedia https://en.wikipedia.org/wiki?curid=10384 / CC BY SA 3.0

Boeing E-3 Sentry

The Boeing E-3 Sentry, commonly known as AWACS, is an American airborne early warning and control (AEW&C) aircraft developed by Boeing. Derived from the Boeing 707, it provides all-weather surveillance, command, control, and communications, and is used by the United States Air Force, NATO, Royal Air Force, French Air Force, and Royal Saudi Air Force. The E-3 is distinguished by the distinctive rotating radar dome above the fuselage. Production ended in 1992 after 68 aircraft had been built.

In the mid-1960s, the US 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 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. NATO, as a single identity, also had 18 aircraft manufactured, basing them in Germany. The E-3 was also sold to the United Kingdom (seven) and France (four) and Saudi Arabia (five, plus eight E-3-derived tanker aircraft). In 1991, when the last aircraft had been delivered, E-3s participated in Operation Desert Storm, playing a crucial role of directing coalition aircraft against the enemy. Throughout the aircraft's service life, numerous upgrades were performed to enhance its capabilities. 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 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 in computer aided radar data analysis and data reduction. These developments allowed airborne radars to "look down", detect the movement of low-flying aircraft (see Look-down/shoot-down), 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. 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 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. The Westinghouse radar antenna was going to be used by whichever company won the radar competition, since Westinghouse had pioneered in the design of high-power RF phase-shifters.
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. Bo...