More eyes in skies.

In the latter half of the 20th century AEW&C aircraft proliferated from the superpowers to what might be described as the more prosperous of the front-line states. Britain, France, Israel, Nato, Japan, Sweden and Taiwan represented the only 'international' market, with the Saudi purchase widely seen as a future host-nation funding the prepositioning of essential equipment for a US expeditionary force. However, in the last decade less expensive AEW&C aircraft have become available, hence requirements have arisen throughout the Asia-Pacific region, on the Indian subcontinent and even in Latin America.

In the beginning, the driving force behind AEW&C development had been the need to protect naval forces against surprise attacks by low-flying aircraft. By 1945, a Grumman Avenger was flying with the US Navy's APS-20A radar, later versions of which equipped a variety of carrier-borne aircraft (including Britain's Fairey Gannet), but also larger land-based aircraft, such as the Lockheed EC-121 Big Eye (as used in Vietnam) and the Avro Shackleton AEW2. Major naval developments were led by the piston-engined Grumman E-1B, which flew in 1957 with the APS-82. It was followed in 1961 by the APS-96 in the twin-turboprop Grumman E-2A Hawkeye, the world's first aircraft designed from the outset for the AEW&C role.

E-2

Of the early AEW&C aircraft, the only one to have survived to the present day is the Hawkeye, now serving in the form of the extensively redesigned Northrop Grumman E-2C. The original E-2A entered service in 1964, and by 1971 all these aircraft had been upgraded to E-2Bs. The E-2C Hawkeye II first flew in 1971 with APS-120 radar and more powerful Allison (now Rolls-Royce) T56 turboprops. It entered service in 1973. By 1976 the APS-125 radar was introduced, with an automatic overland target detection capability and an MTI (Moving Target Indication) facility. In 1988, an update programme was initiated to bring the remaining 55 E-2Cs to Group 0 standard. Further new-build aircraft Were completed to Group I standard, entering service in 1989 with the current 3800 kW T56-A-427 engines and APS-139 radar. The production standard switched to Group II in 1991 With a Lockheed Martin APS-145 radar, a Jtids (Joint Tactical Information Distribution System) radio, colour displays and a GPS receiver. The 170th E-2C was completed in 1994, when the production line closed in New York prior to reopening in Florida.

The 25-tonne E-2C carries two pilots, a radar operator, a mission commander and an air control officer. It has a maximum endurance of six hours, translating into four hours on station at 500 km radius. It cruise climbs from 25,000 to 31,000 ft. Aside from the US Navy fleet (around 75 aircraft available, providing ten active squadrons with four E-2Cs each), the aircraft has been exported to Egypt (seven aircraft), France (three), Israel (four), Japan (13), Singapore (four) and Taiwan (six). The Israeli E-2Cs (now retired) introduced a probe for in-flight refuelling, which could add up to four hours to a sortie but in practice was limited by crew fatigue. It may be noted that the US Coast Guard operates a Hawkeye radar mounted on a Lockheed Martin P-3, which offers much greater endurance and crew space than the E-2C. However, efforts to market the concept internationally have failed.

In 1999, the US Navy's first multiyear production programme for the new Hawkeye 2000 was approved, providing for three aircraft in FY1999, three in FY2000 and five each in FY2001, 2002 and 2003. The Pentagon's FY2004 budget request proposed a second multi-year programme, for two aircraft in FY2004, 2005 and 2006. The first Hawkeye 2000 was delivered in October 2001, introducing avionics improvements that included Co-operative Engagement Capability (CEC), a sensor-netting system developed by Raytheon. Aside from the 27 new-build Hawkeye 2000s, it is planned that 54 Group IIs will be converted to this standard. All US Navy E2Cs are being fitted with the NP2000 eight-blade Hamilton Sundstrand composite propeller, developed from the six-blade Ratier-Figeac propeller of the ATR 42/72 regional transport series. Rather than providing a performance gain, the new propeller will enhance blade reliability and maintainability.

The next step beyond the Hawkeye 2000 is represented by the Advanced Hawkeye and the associated Radar Modernisation Programme. Last August Northrop Grumman's Integrated Systems division was awarded a $1.9 billion contract for the SDD (system development and demonstration) phase of AHE, which will include two test aircraft and lead to IOC (initial operational capability) in 2011. Meanwhile, Lockheed Martin Naval Electronics & Surveillance Systems was given a $413.5 million contract to launch the SDD phase for the next-generation UHF radar, which will involve the production of five radars for testing. For this radar the company is teamed with Northrop Grumman Electronic Systems and Raytheon Space and Airborne Systems. L-3 Communications is responsible for the electronically-scanned antenna and BAE Systems for the IFF system. The Advanced Hawkeye will also have a new cockpit, with displays allowing either pilot to function as a fourth mission system operator. The system is designed to provide the foundation for the Navy's theatre air missile defence, possibly using a Raytheon infrared search and track device to detect ballistic missiles in the boost phase. It will also have improved facilities for battlefield management. It is planned to have the Navy's whole E-2C fleet of 75 aircraft brought to Advanced Hawkeye standard by 2020.

E-3

The advent of jet-powered AEW&C aircraft was marked by the first flight in 1972 of the 152-tonne B707-320B-based Boeing E-3 Awacs (Airborne Warning And Control System), equipped with the Westinghouse (now Northrop Grumman) APY-1/2 radar. The US Air Force bought 34 E-3s and 18 were later ordered by Nato, five by Saudi Arabia, seven by the United Kingdom and four by France. Around 66 E-3s are now in service. The British, French and Saudi aircraft were equipped with CFM International CFM56-2 turbofans from the outset, and those first two nations' aircraft were given flight refuelling probes in addition to the standard dorsal receptacle. The E-3 cruises at around 30,000 ft, and has an unrefuelled endurance of over eleven hours. A typical cabin layout provides for 14 mission consoles.

It is noteworthy that, in order to ensure 24-hour theatre coverage for the 1991 Gulf War, eleven American E3B/Cs were deployed to Riyadh in Saudi Arabia and two to Incirlik in Turkey, adding to the five Saudi aircraft already at Riyadh. Two more US Air Force E-3s were held on standby in Britain and one was kept on alert in America to deploy if necessary. This Awacs fleet monitored up to 3000 sorties per day.

Benefiting from numerous upgrade programmes, the Boeing E-3 remains a viable system today, over 25 years since it entered service. However, the last B707 airframe rolled off the line in May 1991. At the end of that year Boeing announced that further Awacs production would be based on the B767-200ER. The latter flies higher and further, offers over 50 per cent more cabin floor area and will carry an avionics system that is fully interoperable with that of the E-3. The B767 also provides operating economies, since more than 600 commercial aircraft of this series are operating around the world.

767 Awacs

The new programme was launched in November 1993 with an initial contract for two aircraft (designated E-767) for Japan, which was followed by an order for a further two. With the Boeing designation 767-27C, the first airframe was completed in October 1994 and flew with the rotodome in August 1996. It was delivered in 1998 and the type became operational in 2000. The four E-767s serve alongside Japan's 13 E-2Cs, which are being upgraded to Group II standard.

The 175-tonne 767-27C is powered by two General Electric CF6-80C turbofans, giving a cruise climb from 34,000 to 550 km. While an in-flight refuelling receptacle can be fitted, the facility has not been retained on the E-767. The aircraft has a two-man flight deck and the cabin is designed for 19 mission specialists. The standard fit provides nine consoles, although five more can be installed if required.

At time of writing no further orders have been received for the 767 Awacs, but Saudi Arabia is a possible customer. The US Air Force has to decide next year whether to continue with the dedicated Awacs family or to incorporate the AEW&C role into the forthcoming E-10A Multi-sensor Command and Control Aircraft (MC2A), which has Northrop Grumman as prime for Increment 1. This is to succeed the Northrop Grumman E-8C Jstars in providing ground surveillance and battle management, but it will also track cruise missiles in its 30-degree azimuth search area. The Boeing-led MC2A Increment 2 is scheduled to provide AMTI (Airborne Moving Target Indication) over a 360-degree scan, but there are fears that this may interfere with GMTI. The MC2A is to be based on the 200-tonne B767-400ER, presumably offering further increases in time-on-station.

From Russia With Mods

The Soviet Union's first AEW&C aircraft was the four-turboprop Tu-126, which entered service in the late 1960s. It was employed operationally in 1971 to control Indian fighters during that country's conflict with Pakistan. However, in 1965 the Vega NPO design bureau had already started work on the Shmel radar system, which was installed by Beriev on a modified Ilyushin I1-76MD transport. This system entered service in 1984 as the A-50 and it is believed that 23 were built.

The A-50 is a 190-tonne aircraft powered by four Rybinsk D-30 turbofans. It has a four-man flight deck and carries eleven systems operators. Although heavier than the 767 Awacs, it reportedly provides only four hours on station at 1000 km radius, since the weight of the avionics restricts fuel load. It cruise climbs from around 26,000 to 33,000 ft. The A-50U is an upgraded version (probably only existing in prototype form) with Shmel-M radar and a maximum take-off weight of 210 tonnes.

Flight refuelled from Myasishchev ZMS-2 tankers (the 11-78 evidently causing unacceptable buffeting), A-50s were operated over the Black Sea and the Caspian Sea during the 1991 Gulf War to monitor Coalition aircraft and cruise missile movements. In October 1999 Russia offered India one A-50 for immediate delivery, to be followed by two A-50Es, the export version of the A-50U. India paid $1.9 million for an A-50 to take part in its military exercises in June 2000, but the sales offer was declined. In November 2000 Russia reportedly offered China six A-50Es for one billion dollars, but again the offer was declined.

In June 1997, Rosvoorouzhenie (then the Russian state agency for arms exports) signed an agreement with IAI's Elta Systems covering the joint development of an AEW&C system based on the A-50, but using the Phalcon EL/ M-2075 phased-array radar in place of the mechanically scanned Shmel. This unofficially named A-50I was the subject of a contract between Israel and China, covering the supply of up to four aircraft. An A-50 was flown to Tel Aviv in late 1999 for the installation of the radar, but the United States threatened to reduce its $2.8 billion annual funding for Israel and the programme was cancelled in July 2000. China, which had already paid Israel $200 million, claimed compensation and, in early 2002, settled for $350 million. In 2001 China took a three-year lease on two A-50Us, following this with the purchase of up to six A-50Es for delivery by 2005. However, Pentagon officials claim the A-50E has a radar range of only 230 km and can track only 50 targets simultaneously (half that of the Phalcon).

America, however, raised no objection to Israel selling such a system to India and the Delhi newspapers announced that on October 10, 2002, a billion-dollar deal had been signed between the defence ministries of the two countries, covering the supply of three AEW&C aircraft. A third signatory represented the government of the Russian Federation. Other sources indicate that the radar is an improved version of Phalcon, and that the contract is worth $1.25 billion. The A-50 represents a convenient platform for the Indian Air Force, since the service already operates the I1-76 transport and I1-78 tanker. Although the A-50I retains the 'flying saucer' radome of earlier models, in this case it does not rotate. Instead it houses three fixed electronically scanned antennas. The I1-76/78 and A-50 airframe series are produced by Tapo in Uzbekistan but marketed internationally by Rosoboronexport.

Phalcon

The Elta Phalcon (Phased Array Conformal) radar was announced at the 1987 Paris Air Show, when it was described as having a system of six antennas on a B707 airframe, which would typically accommodate eleven operator consoles. It was rumoured that development was being jointly funded by the air forces of Israel and South Africa. At the 1989 show, IAI exhibited a model of a B707 with a conventional nose radome and five large antennas scabbed on to the fuselage, four on the sides (ahead of and behind the wing) and one under the rear. The Israeli Air Force is believed to have at least two such aircraft in operation, replacing its earlier four E-2Cs, while South Africa is thought to have at least two B707s with some Phalcon elements. In May 1993, a Chilean Air Force B707 had its maiden flight with Phalcon antennas in a bulbous nose radome and two massive front fuselage side scabs. Named Condor, it appeared at the 1993 Paris Air Show and was delivered to Chile in 1995. In 2000 it was reported that IAI hoped to sell Chile a further system, possibly using an Airbus A310 as the platform.

For Australia's Wedgetail AEW&C contest in the late 1990s a variant of the Phalcon was proposed (unsuccessfully) by a Raytheon-led team, using the Airbus A310 as platform.

Late last year at the Korea Air Show IAI unveiled a large-scale model of a Phalcon version of the Gulfstream G550, around three of which have been ordered by the Israeli Air Force. In this case there are conventional radomes in the nose and the tail end of the fuselage as well as two large scabs on the cabin sides. The cabin will house six operator stations. The weight and drag penalties associated with the radar will reduce endurance to around ten hours and maximum ceiling to 41,000 ft, but these are still attractive figures in relation to (for example) regional transports. South Korea is evidently regarded as a possible customer.

B737 AEW&C

The current market leader appears to be the Boeing B737 AEW&C, which combines the B737-700IGW airframe and the Northrop Grumman Mesa (Multi-role Electronically-Scanned Array) radar, with dorsal-mounted side-looking antennas and small end-mounted antennas looking fore and aft, giving 360-degree cover. It has a gross weight of 77 tonnes, and provides eight hours on station at 500 km radius, climbing from 30,000 to 40,000 ft. The baseline version has a two-man flight crew and six mission specialists. The radar can track over 3000 targets simultaneously.

The B737 AEW&C was selected by Australia in July 1999, and in late 2000 a contract was placed for four aircraft with an option on three more (currently deferred). The first aircraft is due to fly early this year, leading to two deliveries in November 2006 and others in March and August 2007. The B737 AEW&C is claimed to cost less than half the $400 million of a 767 Awacs, although the Australian contract is valued at approx imately two billion dollars. In June 2002, Turkey signed a one billion dollar contract for four B737 AEW&C aircraft, with an option on two more. Boeing sees a potential market for a further 30 aircraft over the next ten years.

Erieye

Another leader in the field of phased arrays for the AEW&C role is Sweden's Ericsson, producer of the Erieye system. In 1992 Ericsson was contracted to supply six of these PS-890 radars for use on twin-turboprop Saab 340Bs of the Swedish Air Force (SwAF), the resulting aircraft being known as the S 100B Argus. The type entered service in 1997 and is normally crewed by just the two pilots, radar information being downlinked to the ground for analysis. However, for deployment overseas, it can be equipped with up to three operator consoles. The Argus normally patrols at up to 20,000 ft, its dorsal-mounted antennas scanning a primary area covering 150 degrees on either side. Targets outside these arcs can be detected at somewhat reduced range by virtue of the antenna side-lobes.

The limited ceiling of the turboprop encouraged a switch to regional jets for later applications. Brazil chose the twinjet Embraer EMB 145SA equipped with Erieye, and ordered five, of which the first two were delivered in July 2002. The EMB 145SA is a 23.4-tonne aircraft with five workstations, a nine-hour endurance and an operational ceiling of 30,000 ft. Mexico has ordered a similar aircraft, reportedly to operate alongside four exIsraeli E-2Cs in anti-smuggling operations. In late 1999, Greece signed a $600 million contract for four similar EMB 145Hs, with interim AEW&C capability and crew training being provided by the leasing of two Swedish Argus, each equipped for the duration of the lease with two operator consoles.

Vertical Operations

Britain's bitter experience in the South Atlantic in 1982 led to desperate measures to provide AEW&C capability at sea, which had earlier assumed support from US Navy E-2Cs. The addition of a deployable search radar to the Sea King helicopter resulted in the 9.7-tonne AEW2 variant, with two operator stations and a 3.75-hour endurance at 370 km radius. The latest in the series is the Sea King AEW7 with Thales Sensors Searchwater 2000AEW radar.

Possibly encouraged by British developments, Russia has produced (at least) prototypes of the Kamov Ka-29RLD, a derivative of the Ka-29 assault transport with a large ventral-mounted rectangular antenna, which for landing and takeoff is retracted to lie against the bottom of the fuselage. Marketed as the 12.5-tonne Ka-31, it has a two-man crew and an endurance of 2.5 hours. In 1999 the Indian Navy ordered four Ka-31s, followed by five more in 2001.