Boeing E-3A Sentry
1972
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Boeing E-3A Sentry

The requirement for an Airborne Warning And Control System (AWACS) aircraft was outlined by the US Air Force in 1963, at which time it was envisaged that a force of up to 64 of these specially-equipped aircraft would be needed. They were then considered essential to alert US air defences of approaching attack by manned or unmanned air vehicles of all classes, and to act as mobile control centres of unfixed geographical position, able to.control all national air activities in both conventional or nuclear combat operations. However, since the origination of the concept, economic considerations have made it necessary to reduce considerably the number of aircraft to be acquired initially.

The resulting Boeing E-3A Sentry is essentially a flexible, jamming-resistant, mobile and survivable radar station, plus a command, communications and control centre, all contained within the well-proven airframe of a Boeing 707. In addition to its long-range high- or low-level surveillance capability, an AWACS aircraft can provide all-weather identification and tracking over all kinds of terrain, and the 22nd and subsequent aircraft also have a maritime surveillance capability. These aircraft can command and control the entire air effort of a nation, embracing interception, interdiction, reconnaissance and strike, plus the back-up roles of airlift and support.

Two main areas of use have been planned by the USAF, with the Tactical Air Command (TAC) using its AWACS aircraft for airborne surveillance, and as a command centre for the rapid deployment of TAC forces. A differing role is envisaged for the same aircraft by Aerospace Defense Command (ADC), who regard the AWACS aircraft was 'hard to find' command and control posts. (ADC has now become a component of TAC, but the two basic E-3A missions remain substantially unaltered.)

Boeing was the successful one of two contenders for the supply of an AWACS aircraft, being awarded a contract on 23 July 1970 to provide two prototypes under the designation EC-137D. The company's proposed AWACS was based on the airframe of the Boeing Model 707-320B commercial transport, and the prototypes were modified in the first place to carry out comparative trials between the prototype downward-looking surveillance radars designed by the Hughes Aircraft company and Westing-house Electric Corporation. These tests continued into the autumn of 1972, and on 5 October the USAF announced that Westinghouse had been selected as prime contractor for the advanced radar that was to be the essential core of the AWACS. This has the difficult task of seeking and identifying low-flying targets at ranges as great as 370km, and in the case of high-altitude attack at even greater ranges.

The USAF had acquired an extensive knowledge of the operation and capabilities of the Boeing Model 707, especially in the form of the EC-135 variants which have served well and long. It was clear that with far more advanced equipment the same aircraft could provide the desired potential, thus ensuring that equipment acquired for and experience derived from the EC-135 would offer an important and reliable contribution to the AWACS concept.

Very little modification of the basic 707-320B airframe was needed to make it suitable for the new role. Most important, and an external identification feature par excellence, is the large rotodome assembly carried on two wide-chord streamlined struts, which are secured to the upper rear fuselage. The remainder of the essential avionics antennae are housed within the wings, fuselage, fin and tailplane. New engine pylon fairings are provided for the more powerful turbofan engines of the pre-production EC-137Ds, and of the production aircraft which were designated E-3A and given the name Sentry. Internal modifications included strengthening of the cabin floor, provision of MPC (multi-purpose console) and other equipment bays, and addition of a crew rest area. Basic operations require a flight crew of four plus 13 AWACS specialist officers, but this number can vary for defence and tactical missions, and other personnel can be cer-ried for systems management and radar maintenance.

Not surprisingly, the mass of avionics equipment needed for the E-3A to fulfil its AWACS role has required the installation of extensive cooling and wiring systems. The cooling and air-condition ing systems are complex to ensure an ideal working environment for crew and equipment. Thus, liquid cooling protects the radar transmitter, housed in the aft cargo hold, and a conventional air-cycle and ram-air environmental control system provides for crew comfort and the safe operation of other avionics equipment. There is also a large demand for electrical power, which is supplied by generators with a combined output of 600 kVA. The over-fuselage rotodome is 9.14m in diameter and has a maximum depth of 1.83m. This incorporates the AN/APY-1 surveillance radar and IFF/TADIL C antennae. During operational use the rotodome is driven hydraulically at 6 rpm, but in non-operational flight is rotated at one twenty-fourth of this speed to ensure that low temperatures do not cause the bearing lubricant to congeal and prevent normal operation when required.

The current Westinghouse radar, installed first in the 22nd Sentry, and scheduled to be updated in earlier aircraft, can function as a pulse and/or pulse-Doppler radar, and is operable in six different modes. The data processing capability of the first 23 E-3As is provided by an IBM 4 Pi CC-1 high-speed computer. It has a processing speed of some 740,000 operations per second, main memory capacity of 114,688 words, and a mass memory of 802,816 words. The IBM CC-2 computer, introduced on the 24th production aircraft, has a main memory capacity of 665,360 words. Also introduced on this aircraft is the newly-developed Joint Tactical Information Distribution System (JTIDS). This provides a high-speed secure communications channel for up to 98,000 users, and one that is less vulnerable to jamming.

The first production E-3A was delivered on 24 March 1977 to the USAF's 552nd Airborne Warning and Control Wing, based at Tinker AFB, Oklahoma. The current force of AWACS aircraft for service with the USAF is 34. In addition, a force of 18 generally similar aircraft was acquired by NATO. Initial deliveries of NATO's operational E-3As, which are based at Geilenkirchen, West Germany, were made during 1982. They differfrom their USAF counterparts by comparatively minor changes in installed avionics to meet NATO communications requirements. They also introduced underwing hardpoints to carry self-defence weapons, but these mountings can be used optionally to carry ECM pods. The Sentry has also been sold to Saudi Arabia, France and the United Kingdom, all export aircraft being powered by CFM56 high bypass ratio turbofans.

Boeing E-3A Sentry


Specification 
 CREW17
 ENGINE4 x Pratt & Whitney TF-33-PW-100/100A turbofans, 93.3kN
 WEIGHTS
    Take-off weight147418 kg325003 lb
 DIMENSIONS
    Wingspan44.42 m146 ft 9 in
    Length46.61 m153 ft 11 in
    Height12.6 m41 ft 4 in
    Wing area283.35 m23049.95 sq ft
 PERFORMANCE
    Max. speed853 km/h530 mph
    Ceiling8840 m29000 ft
    Range w/max.fuel12000 km7457 miles

3-View 
Boeing E-3A SentryA three-view drawing (592 x 966)

Comments
Leroy McVay, leroynjean=msn.com, 16.10.2013

I'll get my story straight yet! Very first one used ultra vilot light, i.e. heat waves, to locate target. Big security on a/c as we worked on it. Mechanic bought a magazine with EVERYTHING YOU MIGHT WANT TO KNOW ABOUT THE A/C & HOW IT WORKED! Took magazine to Air Force inspection office. He tossed it across the desk and said, "So much for security!"

E3flyer, 17.12.2011

the E-3A is the NATO version while the B/C variants are the ones at Tinker and the D/F are the Brits and French. The Saudis have a few as well as the Japanese have the 767 versions..All E-3's are were built to be E-3's on the 707 production line...Unlike the JSTARS plane E-8C which are refurbished/retrofitted airliners. Just got done with my career of flying on these planes.

Leroy McVay, leroynjean=msn.com, 18.03.2011

Modify my comments a little. One we worked on had a 'green house,' not the antenna as shown in picture.

Leroy McVay, leroynjean=msn.com, 18.03.2011

Worked on original re-work of KC135 to AWACS. Engineering drawing were for current production a/c. Air Force gave us line number 13 to re-work. Nothing matched! Had a resident liasion engineer. Several time he told us to figure it out and he'd draw a picture later; this was ll non-structural. First work order was to cut a 5' (?) hole in top of the plane. We were right on.

Lee Patterson, 27.10.2010

Was in the 552nd when Boeing delivered the first one. All of the aircraft in the original fleet were 707 airframes.

Kenneth W. Bennett, k_kbennett=sbcglobal.net, 22.03.2010

Message for Chris. The E-3A's B's and C's were based on a B707-320 airframe. I performed Comm maintenance on them at Tinker AFB, OK in 1980-81. Though looking at new pictures they might have moved to a new airframe. FYI . . Japan AWACS is a modified 767.

Chris, aikens.christopher=gmail.com, 11.03.2010

I heard that the E-3A is based on the 707 but conflicting sources tell me otherwise. Does anyone know for real? Please leave a comment directed at me. Thanx

Moshakes, pilot2004abdu=yahoo.com, 23.08.2009

I am working on the E-3A AWACS i wont any new information

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