The Boeing E-3 Sentry is an airborne early warning and control (AEW&C) developed by Boeing as the prime contractor. Derived from the Boeing 707, it provides all-weather surveillance, command, control and communications, and is used by the United States Air Force (USAF), NATO, Royal Air Force (RAF), 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 were built.
In the mid-1960s, the USAF was seeking an aircraft to replace its piston-engined EC-121, which had seen 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. NATO, as a single identity, also had eighteen 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, by which time 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 was acquired by Northrop before being renamed Northrop Grumman Electronic Systems, which currently supports the E-3′s radar.
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—but the E-10 program was canceled by the Department of Defense. The USAF is now performing a series of incremental improvements, mainly to avionics, to bring the E-3 up to current standards of performance. Boeing is flight testing its Block 40/45 E-3s. This modified E-3 contains upgrades of the mission crew and air battle management sections, as well as significantly upgraded electronic equipment.
The E-3 Sentry’s airframe is a modified Boeing 707-320B advanced model. USAF and NATO E-3s have an unrefueled range of some 4,000 mi (6,400 km) or eight 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 about 5,000 mi (8,000 km). The Sentry’s range and on-station time can be increased through air-to-air refueling and the crews can work in shifts by the use of an on-board crew rest and meals area.
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; whilst 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 fighter-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.
The unpressurized dome is 30 feet (9.1 m) in diameter, six feet (1.8 m) thick at the center, and is held 11 feet (3.4 m) above the fuselage by two struts. It is tilted down 6° at the front to reduce its air drag during take-offs, and while flying endurance speed (which is corrected electronically by both the radar and SSR antenna phase shifters). The dome uses both bleed-air and cooling doors to remove the heat generated by electronic and mechanical equipment. The hydraulically rotated antenna system permits the Westinghouse Corporation’s AN/APY-1 and AN/APY-2passive electronically scanned array radar system to provide surveillance from the Earth’s surface up into the stratosphere, over land or water.
Other major subsystems in the E-3 Sentry are navigation, communications, and computers. Consoles display computer-processed data in graphic and tabular format on video screens. Console operators perform surveillance, identification, weapons control, battle management and communications functions. The radar and computer subsystems on the E-3 can gather and present broad and detailed battlefield information. This includes position and tracking information on enemy aircraft and ships, and location and status of friendly aircraft and naval vessels. The information can be sent to major command and control centers in rear areas or aboard ships. In times of crisis, data can be forwarded to the National Command Authority in the U.S. viaRC-135 or naval aircraft carrier task forces.
Electrical generators mounted on each of the E-3′s four engines provide one megawatt of electrical power that is required by the E-3′s radars and other 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 “beyond the horizon” radar has a range of approximately 400 mi (650 km) for aircraft flying at medium to high altitudes. The radar combined with secondary surveillance radar to provide a look down to detect, identify and track enemy and friendly low-flying aircraft while eliminating ground clutter returns.
Specifications
Crew: Flight crew: 4; Mission crew: 13–19
Length: 152 ft 11 in (46.61 m)
Wingspan: 145 ft 9 in (44.42 m)
Height: 41 ft 4 in (12.6 m)
Wing area: 3,050 ft² (283.4 m²)
Empty weight: 185,000 lb (73,480 kg)
Loaded weight: 344,000 lb (with aerial refueling) (156,036 kg)
Max. takeoff weight: 347,000 lb (157.397 kg)
Powerplant: 4 × Pratt and Whitney TF33-PW-100A turbofan, 21,500 lbf (93 kN) each
Maximum speed: 530 mph (855 km/h, 461 knots)
Range: 4,000 nmi (7,400 km)(8 hr)
Service ceiling: 41,000 ft (12,500 m)
Boeing E-3 Sentry was first posted on November 26, 2013 at 12:23 pm.
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