Graham Warwick/WASHINGTON DC
On Northrop Grumman's map of prospective customers for airborne warning and control (AEW&C) aircraft, only one country is marked as conquered - Australia. Next to fall, the company hopes, will be Turkey. A win there will be followed by an assault on Israel. Italy and Spain are listed as future targets, as are a clutch of Asia-Pacific countries: Malaysia, Singapore, South Korea, Taiwan and Thailand.
Northrop Grumman's interest is in the market for Boeing's 737-based AEW&C aircraft, for which it is developing the radar, continuing a co-operation which began with the Airborne Warning and Control System (AWACS), in original 707- and current 767-based forms.
"South Korea's AEW requirement is coming back," says Bill Adams, vice-president, airborne surveillance systems. Meanwhile, Singapore, Taiwan and Malaysia "have all started planning" for AEW procurements, he says.
Each of the countries marked on Northrop Grumman's map has a requirement for at least four AEW&C aircraft, the minimum required to provide continuous coverage. Combined with Australia's launch order for seven 737 AEW&Cs - and an unsolicited offer to the USAir Force of eight aircraft to augment its overstretched AWACS fleet - that makes an identified market for more than 50 aircraft.
Northrop Grumman's market projection would seem optimistic - given that only 70 AWACS have been delivered to just six operators over the past 20-plus years - were it not for the fact that Boeing's 737 AEW&C dramatically reduces the cost of entry into the exclusive club of AEW owners.
According to Adams, the 737 AEW&C costs $150-190 million, compared with around $400 million for the 767 AWACS - "and the price will be higher after the production break" which followed delivery of four aircraft to Japan, he says. "The 767 is a superior platform, but at a superior price not many customers can afford."
Key to the 737 AEW&C's affordability - and capability - is Northrop Grumman's MESA active-array radar. The antenna can be installed "with very little modification to the platform itself", maintaining the high dash speed and long endurance of the Next Generation 737 airframe. "Windtunnel tests with the Tophat antenna show no difference in performance from the 737NG," Adams says.
The 550mm (22in)-thick antenna will be attached to the top of the aft fuselage by 22 bolts. Modified skin panels, frames and stringers "are the only new things Boeing will do on the line", he says. This contrasts with the major modifications made to the 707 and 767 airframes to support the heavy AWACS rotodome.
The 288 transmit/receive modules for the active-array radar will be installed inside the aircraft, to improve reliability and maintainability in flight. The same modules will power all three elements of the antenna - switching between the two side-facing arrays and the Tophat end-fire arrays that look fore and aft. Identification friend or foe (IFF) will be integrated into the same array and will operate simultaneously with the radar - "a first for us", says Adams.
While its technology is very different, the MESA builds on Northrop Grumman's long experience with the APY-1 and -2 radars in the AWACS. A key feature carried over is the ability to perform over land and sea, detecting and tracking air and surface targets. "Most other systems can't do both," he says.
Over land, the MESA radar can see targets travelling at speeds down to 10kt (18km/h), while the AWACS radar is intentionally "notched out" at around 50kt to avoid overloading the processor. The MESA can handle up to 10,000 reports per scan, he says.
Active electronically scanned array radar technology adds the ability to generate a flexible, agile beam that is not restricted to repeating endlessly the same 360° sweep. According to Northrop Grumman, an agile beam allows the radar to interlace several functions:
• 360° surveillance, providing a 10s update rate and a range of 350-370km (190-200nm) against a 1m² (11ft²) airborne target;
• sector emphasis, focusing radar power in a particular direction to extend range;
• maritime mode, detecting surface targets as small as fast patrol boats at reduced range;
• dedicated track beams, providing target updates every second or less;
• interleaved IFF.
The agile beam also allows flexible radar utilisation. The basic operating mode replicates the AWACS' capability, and provides uniform 360° coverage, but the electronically scanned array allows the operator to focus the radar's energy in particular directions.
In platform-stabilised sector operation, 30% of the radar's energy is redirected towards the side array that is facing the threat, providing increased range over one-third of the 360° scan. For the remaining two-thirds of its scan the radar provides background coverage, but with reduced range.
Ground-stabilised sector operation is similar, Adams says, "but because the Tophat has less gain than the side arrays there is not as much range increase" when the threat sector is ahead of, or behind, the aircraft as it orbits. Dedicated sector operation, meanwhile, focuses all the radar energy in a 30° threat sector, "and increases performance by another factor", he says, adding that the mode is used "when you know exactly where to look".
Northrop Grumman is set to deliver the first MESA array to Boeing in 2002, with deliveries of the 737 AEW&C to the Royal Australian Air Force expected to begin in 2003. As prime contractor, Boeing leads a team that includes Northrop Grumman's Electronic Sensors and Systems Sector, Boeing Australia and BAE Systems Australia.
Based on the configuration selected by Australia to meet its Project Wedgetail requirement, the Boeing-led team has created a "core product" for the export market, says Adams. This core system includes the airborne segment, mission planning and analysis, mission crew training and system support.
The aircraft itself is based on the Boeing Business Jet, a hybrid of the 737-700 fuselage and strengthened 737-800 wing. The CFM International CFM56-7 engines are fitted with 90kVA generators to power the radar.
Inside, the core 737 AEW&C has six mission consoles, mounted facing outwards (rather than forwards, as in the AWACS). There is a crew rest area in the centre cabin and the aft section is reserved for the radar electronics, with space available for growth. According to Adams, options include increasing the number of operator consoles to 10, increasing the radar power and modes, and fitting systems such as electronic support measures.
Turkey's AEW competition is in its final stages and Boeing/Northrop Grumman and Raytheon/Elta were due to submit their best and final offers on 10 February. The country has asked for up to eight aircraft, but so far only has funding for four.
Having won in Australia against the Raytheon-led team offering an Airbus A310 equipped with Elta's Phalcon active-array radar, Adams believes a victory for the 737 AEW&C in Turkey would "open up Israel as the next target". Israel has operated Northrop Grumman E-2C Hawkeyes, and is seeking four AEW&C aircraft as part of any US arms package tied to a peace accord with Syria.
The Asia-Pacific economic recovery has rekindled hopes that South Korea will restart its stalled AEW procurement. The country had shortlisted the 767 AWACS and Raytheon/Elta A310 AEW&C, but Adams is hopeful the 737 AEW&C will be included in any new competition. "We think the 737 will be included and we hope the 767 is still in the competition," he says.
Despite the launch of the 737 AEW&C, work continues on the AWACS family. The radar system improvement programme (RSIP), now under way, is increasing detection range and accuracy, and allowing the APY-2 to see smaller and slower targets. Electronic counter-countermeasures and operator man/machine interface, as well as reliability and maintainability are also being improved.
During the Kosovo conflict, Adams says, the upgraded AWACS beat its specification, which was to see the same size target at twice the range. At the same range, the RSIP AWACS can see targets which are 10 times smaller, he says. Range, azimuth and altitude accuracy has been doubled and range resolution increased by a factor of six, enabling the AWACS to separate multi-aircraft raids into individual targets.
By the end of last year, all NATO E-3 Sentry AWACS had undergone the RSIP upgrade. The USAir Force has begun upgrading its E-3s and plans to accelerate the programme, while all the UK Royal Air Force's Sentries are to be upgraded by March next year. "We are ready to get France, Saudi Arabia and Japan under contract," says Adams.
Northrop Grumman says the AWACS will be flying for several more decades, perhaps augmented by 737 AEW&Cs and new platforms such as the company's Global Hawk unmanned air vehicle and space-based radars. The company also sees potential new applications for its active-array radar technology, including the upgrade and eventual replacement of its own long-running AEW platform, the Hawkeye.
Source: Flight International
