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BOEING 737 AEW&C; WEDGETAILBy Karl Schwarz
Ever since the 1970s Australia had harboured ambitions of procuring an airborne early warning & control (AEW&C;) aircraft, but at the end of the 1980s the then defence minister was forced to concede that the available systems were simply beyond the country's financial means.
Then, in the mid-1990s, the Australian military made another bid for this valuable resource. This time they were successful, for, as Wing Commander David Blacklock, who is in charge of the aircraft programme, put it, For a country with so much territory and such small, albeit powerful, armed forces, a system like Wedgetail is essential to ensure that these forces are in the right place at the right time. Wedgetail is an important element of our vision of network centric warfare. In the case of Wedgetail, which is named after an indigenous species of eagle, this vision will become reality in November of next year when Boeing hands over the first two 737 AEW&C;'s.
The Royal Australian Air Force (RAAF) will then have one of the most advanced early warning aircraft in the world. Its excellent performance is down to the Northrop Grumman supplied multi-role electronically scanned array (MESA) radar, a system that offers several operating modes and electronic beam steering of the antenna. This replaces the rotating antenna normally found on aircraft such as the E-3 AWACS or the E-2 Hawkeye, and as a result it is a lot more compact, while also being lighter and incorporating better aerodynamic design.
The antenna, which scans both sides, will fit, for example, into a 9.2m long, 55cm wide panel on the upper side of the fuselage. To ensure 360º visibility, a top hat which accommodates antenna elements fore and aft is superimposed on this.
As the MESA beam is electronically steered, the radar, which functions in the L band (1 to 2GHz, wavelength 15-30cm) is very flexible. Naturally it can also swivel 360º, a feat that is accomplished in around ten seconds. But more interesting are other operating modes, such as a more intensive search in a 120º sector, into which about 30 percent more energy is then pumped, while the rest receives correspondingly less energy. This can be used at ranges of up to 350 to 400 kilometres. The greatest range is achieved when all the energy of the MESA is concentrated on a narrow 60º sector.
The MESA radar can detect airborne targets moving at velocities from about 20 km/h. It also has a maritime surveillance capability. An Interrogation Friend or Foe (IFF) function is integrated.
The entire antenna structure weighs just under 3,000kg. It is attached with 22 bolts to the fuselage, which has reinforced frames to carry the extra weight. The cabling leads to the cabinets underneath where the control and signal processing computers are housed. The cabinet which contains the other electronic systems is similarly installed at the rear of the aircraft. Amongst other things, the 737 AEW&C; Wedgetail is fitted with a comprehensive self-defence system that includes the Northrop Grumman Nemesis system, which can engage approaching IR missiles.
In front of the electronics are a small rest room and a galley for the crew, which comprises a minimum of ten operators. Their consoles are accommodated in the forward cabin area along the side walls. Additional computers and radios (8 x UHF, 3 x HF, 2 x UHF, data links) are also located in this area. As in the civil version of the 737, the two-man cockpit has large colour displays.
As well as completely new cabin equipment and significant extensions to the cabling, the 737 AEW&C; has auxiliary tanks in the cargo bay, as on the Boeing Business Jet (BBJ). This means it can remain airborne for around 10 hours. With air refuelling, patrol time can be further extended. The power supply for the electronics and radar is provided by two 180kVA generators on the CFM56-7 engines.
So far the military division of Boeing (Integrated Defense Systems) has taken over two 737-700 IGS (enhanced takeoff weight) from the final assembly line. Following installation of the tanks and modification of the airframe, the aircraft with registration N378BC took off on 20 May 2004 from Boeing Field in Seattle for a two-hour maiden flight. Test pilots Charles Gebhardt and Ray Craig subsequently said that they were very pleased with the aircraft handling.
By the end of last year, some 400 flying hours had been completed. This included flights behind the KC-10 and KC-135, aimed at estimating the behaviour of the aircraft during air-to-air refuelling. Again, during the summer the cooling of the generator in the engine nacelle was tested at external temperatures of over 30ºC. The aircraft has behaved extremely well throughout, and we have had no unpleasant surprises as far as the aerodynamics is concerned, Boeing Programme Manager Patrick Gill is reported to have said in November.
However, since then it has emerged that the radar top hat needs to be raised somewhat to deliver the required performance. Modifications aimed at achieving this were begun in Seattle in December, but Boeing is confident that it can meet the schedule, not least because four previous milestones were achieved early.
The second 737 AEW&C; Wedgetail was fitted with its radar at the end of November 2004. In May it will begin a test programme that will last until June 2006. Both aircraft will then undergo field tests, following which they will be handed over to the RAAF in November of that year. The 737 AEW&C;'s are to be based with 2 Squadron in Williamstown. However, they will also fly regularly from Tindal base near Darwin.
In June 2004, Australia ordered another two Wedgetails, for delivery by the spring of 2008. These are to be converted in Amberley, Queensland, creating 150 to 170 jobs. Altogether the country is investing A$3.43 billion (approx. Euro 2 billion) in the new early warning system.
As well as Australia, Turkey has also decided to purchase the 737 AEW&C.; A contract worth over US $1 billion for the supply of four aircraft plus training and maintenance facilities was signed on 1 June 2002. However, it took some time for the contract to be approved by the US Congress, so that work on the Peace Eagle could not commence until July 2003.
The first 737-700 earmarked for the conversion rolled out of the hangar in Renton at the beginning of November 2004. It is to commence flight testing at the end of 2006, with a view to delivery in 2007. The three additional aircraft are to be converted at TAI in Turkey and are scheduled for delivery to the Turkish Air Force in 2008.
Boeing currently has its sights set on South Korea as another potential customer for the 737 AEW&C.; Here it is competing against a consortium made up of Israel Aircraft Industries, Gulfstream and L-3 Communications, which is offering the G550 business jet. The company sees additional sales opportunities in Italy, Spain, Singapore, Japan, Malaysia and the United Arab Emirates. The unit numbers of individual sales will never be very big, but Patrick Gill believes there are prospects for around thirty aircraft over the next ten years.
From page 58 of FLUG REVUE 3/2005
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