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  • AESA And Typhoon
    Posted by Bill Sweetman 4:24 PM on Feb 19, 2009

    Everyone buying fighters wants an active electronically scanned array (AESA) these days, no doubt after reading Dave "Mr AESA" Fulghum on the subject.

    But Eurofighter remains wary about the issue. The consortium's executives still stay that - for today - the mechanically scanned (M-Scan) Selex Captor beats any in-service AESA for the Typhoon's mission, even though Selex itself is ready to go with its Vixen range of AESA radars. A clue as to why they think that way emerged at the Aero-India seminar last week.

    Discussing future technologies, Dr, Peter Gutsmiedl, senior vp engineering at EADS Military Air Systems, pointed out ways in which AESA could be integrated into Typhoon - one being the conventional fixed, canted antenna. They included an antenna with auxiliary side arrays, an azimuth gimbal and the so-called "swashplate" radar, a canted antenna on a rotating mount:

    blog post photo

    What's behind this thinking? A few years ago, Prof. John Roulston - former technical director at BAE Systems' radar division, now part of Selex - presented a paper in which he pointed out a limitation of AESA: at extreme scan angles the effective aperture decreases, and the performance of the radar (range, sensitivity and jamming resistance) declines as a result. So today's M-Scan has a larger field of regard than a fixed AESA, and better performance at the edge of the scan envelope.

    This is important for Typhoon because the whole system - in the air-to-air regime - is influenced by air-combat simulations in which a fighter-to-fighter engagement could involve multiple MRAAM shots, followed by a supersonic turn to evade the adversary's fire and extend the F-pole - the distance between the launch aircraft and the target at impact. To do this, it's essential to have a radar that can continue to track the target and guide the missile as the shooter turns away.

    The gimbal of a pointable AESA does not have to be anything like as fast as an M-Scan gimbal. The high-speed stuff, tracking a moving target, is still done electronically, with the gimbal moving relatively slowly to optimize the field of view.

    Moreover, the electronic field of view is now added to the gimbal scan: the swashplate design shown here adds the 60-degree AESA limit to its 45-degree cant angle, to cover 105 degrees in all directions - a total 210-degree field around the nose.

    By the way, the designers of the Su-35 think the same way, and the F-22 has space, weight and cooling provision for side arrays, but so far they have been deferred due to budget cuts.

    Tags: ar99, aesa, typhoon

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