Boeing 737-700 AEW&C
As various nations begin to take delivery of, or make plans to acquire, 4th generation fighter aircraft, they are also considering how to make the most affective use of these highly capable aeroplanes. Recent conflicts in the Middle East have once again served to remind those tasked with planning future operations, that the deployment and effective operation of an AEW&C system, working in conjunction with modern fighter aircraft, is an essential part of any successful modern air campaign. For many years the only real options available to countries wishing to purchase this capability were the Grumman E-2C Hawkeye and the Boeing E-3 Sentry. However, as the Israel air force discovered, the E-2C is optimised for over-water operations and its small size limited both the crew numbers and equipment carried. The E-3, whilst highly capable, is much larger, as well as being very expensive to both purchase and operate - consequently it was beyond the reach of most nations. The E-3 was based on the last of the old 707 airframes made by Boeing that, although tried and tested, used fairly old technology. Consequently, when Japan eventually decided to acquire an Airborne Warning And Control System (AWACS) capability after the 707 assembly line had closed down, their only option was to buy four Boeing 767 AWACS – an much more modern and capable aircraft, but so prohibitively expensive that Boeing have so far received no other orders for this type of aircraft.
One of the main reasons Boeing used the large, long-range 707 and 767 airframes for the AWACS was the need to carry the heavy Northrop Grumman AN/APY-2 radar, mounted inside a radome above the rear fuselage, whilst also having sufficient room within the fuselage for a large crew and a considerable amount of avionic equipment. However, because these expensive aircraft have only sold in limited numbers, Boeing have decided that a different approach is required if they are to have any chance of capturing the bulk of the estimated $30 million market for AEW&C systems over the next decade.
In response to this potential market, Boeing has developed their next generation AEW&C system, basing the platform on the latest version of their highly successful 737 commercial airliner – the 737-700 IGW (Increased Gross Weight), based on the airframe used for the Boeing Business Jet, but without the winglets. This modern airframe offers state of the art avionics, together with modern fuel-efficient CFM International CFM56-7B24 engines, providing a range of 3000nm together with an operating ceiling of 41,000ft. Most aircraft are likely to be fitted with an air-to-air refuelling system, either a probe or a flying boom receptacle. Typically the aircraft will operate with 2 pilots and between 6 and 10 mission crew.
However the use of the 737-700 in the AEW&C role has only been possible because of considerable advances in radar technology and avionics, enabling an AEW&C system, with similar capability to the E-3A, to be carried on and within a much smaller aircraft. The most obvious change is in the radar – instead of a 30ft rotating radome, the 737 will be equipped with the latest generation Northrop Grumman MESA (Multi-Role Electronically Scanned Array) L band radar, contained within a low drag fairing mounted above the rear fuselage. The fairing is an advanced ultra-light foam composite sandwich structure that supports side-emitting electronic manifold arrays and a ‘top hat’ end-fire array - using these three innovative apertures, sharing transmit and receive modules, the MESA will achieve 360 degree coverage out to a range of over 200nms. The MESA will provide multiple surveillance applications, using a variety of pulse radar forms for both air and sea search, as well as having an integrated civil and military IFF capability with a range of over 300 miles. The MESA and associated systems can track over 3000 air and sea targets simultaneously whilst continuously scanning the area of operations.
In Dec 00 under Project Wedgetail, Australia placed an order for four 737 AEW&C aircraft, with an option for 2 additional aircraft, in a contract worth $2.7 billion. The Wedgetail 737 AEW&C will be equipped with 6 identical multi-functional consoles, operating a Boeing designed Open Systems Architecture (OSA) mission system that uses 80% Commercial Off The Shelf (COTS) software. An extensive range of communications suite will also be installed, including HF, VHF, UHF communication systems together with Link 4A and Link 11 systems. The missions systems also include an Electronic Support Measures (ESM) and Electronic Warfare Self Protection (EWSP) systems supplied by Elta Electronics of Israel, giving the aircraft a considerable ELINT capability. To provide additional safety against Man Portable Air Defence Systems (MANPADS), Northrop Grumman will supply their AN/AAQ-24(V) Nemesis Directional Infrared Countermeasures (DIRCM) system, augmented with a Viper solid state multi-band laser. The first aircraft was rolled out in Mar 04 and should make its first flight in May 04. The first two aircraft should be delivered to Australia in Nov 2006, with another two following in mid-2007. Initial operational capability is planned for mid-2008. The aircraft will be operated by 2 Sqn based at RAAF Williamtown.
Turkey has also had a long-standing requirement for an AEW&C aircraft and the recent plan by Greece to acquire the EMB-145SA has focused their attention on the 737 AEW&C aircraft. In Jul 02 Boeing won a $1.5 billion contract from Turkey to supply four 737 AEW&C aircraft from 2007. However, a Turkish parliamentary anti-corruption commission is currently investigating a number of allegations, including broken cost and technology transfer commitments, which formed part of this contract. The allegations seem to imply that Turkey did not negotiate as good a contract for the four 737 AEW&C as Australia, but the issues will almost certainly be resolved without the delivery dates being affected.
On 20 May 04 the first Boeing 737 AEW&C 'Wedgetail' got airborne from Boeing Field in Seattle at 10.15am flown by Boeing test pilots Charles Gebhardt and co-pilot Ray Craig. During the 2 hour test flight various tests of the aircraft's systems and structures took place. Gebhardt reported that that there were no porblems with the handling, which was very similar to the 737-700. Flight testing is scheduled to continue through to mid-December 04. However in early 2005 Boeing suspended flight and radar tests of the first aircraft to allow significant modifications to be made to the MESA radar. It is believed that during certain tests problems with the performance of the MESA radar became apparent. To overcome this problem the height of the 'top hat' will be raised and this work will take at least a month or even longer, however, Boeing are confident that this problem can be resolved. Delivery of the first two aircraft is still planned for Nov 2006, with the next two following in 2007.
Cost and technology transfer have been the main inhibitors in limiting the spread of AEW&C systems to developing air forces. Boeing believes that the future platform for AEW&C systems is the large business jet and the evidence would suggest that other companies agree. With the Embraer SA-145 already in the market and Gulfstream developing the G500 into a compact AEW&C system for the Israeli Air Force, in the 737 AEW&C system Boeing would appear to have a product that will sit neatly between these more ‘compact’ systems and the much larger 767 AEW&C.