The Sentry AEW Mk1, or Boeing E-3D, aircraft which replaced the Avro Shackleton AEW Mk2 in 1990, is a highly capable and versatile Airborne Warning And Control System (AWACS) aircraft. Entering service with the USAF in 1977, and subsequently with the NATO AEW Force in 1982 and the Royal Saudi Air Force in 1986, the E-3 series is based on the Boeing 707-320B airframe of 1960s vintage. Seven RAF E-3Ds and four French Air Force E-3Fs were built to almost identical specifications and procured jointly from the manufacturer.
When introduced, the technology present in the E-3D represented a leap of several generations over the Shackleton. Flying at 29,000 feet, the Westinghouse AN/APY-2 multimode radar has the capability to scan over 300,000 square kilometres of the earth's surface and the information gathered is processed by a high capacity central computer system, before being displayed on 9 mission consoles. Information is then distributed to interested agencies via numerous secure data link systems. The aircraft also has an impressive UHF, VHF and HF radio suite which offers either secure or clear voice communications. Unlike the other other E-3 variants currently in service, the E-3D is equipped with an Electronic Support Measures (ESM) system - the Loral 1017 "Yellow Gate" - which greatly enhances its surveillance and identification capabilities.
To increase the already significant range and endurance of the E-3D, the aircraft is fitted with a dual in-flight refuelling system, enabling replenishment from either probe and drogue tankers (VC10 and Tristar) or boom and receptacle (for example USAF KC10 and KC135). To operate the aircraft, employ the mission system tactically and carry out in-flight maintenance as necessary, the E-3D has a crew of 17 men and women. The flight crew of 4, comprising of two pilots, a navigator and a flight engineer, and the mission crew, led by the tactical director, consists of weapons and surveillance teams, a communications operator and three airborne technicians.
In addition to the traditional AEW role, which centres on extending and enhancing radar cover in order to detect and report potentially hostile aircraft at all altitudes and subsequently vector air defence fighters to intercept the threat, the E-3D AWACS platform has many other applications, including maritime surface surveillance, offensive support and various command and control functions. The aircraft is undoubtably the most significant addition to the RAF front-line in recent years and, whilst new applications for its many talents continue to be found, its capabilities and flexibility offer senior commanders immense tactical and strategic advantages.
From the first delivery of the airframe to Waddington in March 1991, the outstanding performance of the E-3D has significantly assisted the Component, comprising No 8 Squadron, Sentry Training Squadron (now part of No 23 Squadron), and the Sentry Standardisation Unit, to rapidly achieve operational maturity. Since then, the E-3D force, in concert with the E-3A Component and the E-3F squadron in France, has risen rapidly to the challenge of full-time support to United Nations and NATO initiatives in the Balkans, presently collectively known as Operation Decisive Endeavour. The fourth anniversary of E-3D involvement in the former Republic of Yugoslavia theatre passed in July 1996. Formation of the second AEW squadron at Waddington has introduced an element of healthy competition into the E-3D world and created a more efficient Component structure.