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  • Anti-Stealth Sensors to Tackle Chinese and Russian LO Designs
    Posted by David A. Fulghum 8:13 PM on Jan 11, 2011

    With first flight out of the way, the discussion about China’s new J-20 stealth prototype is switching to the aircraft’s mission (fighter or, more likely, long-range strike), sensors (strike missions would require a high-resolution long-range radar) and communications (which would demand high-speed datalinks and sophisticated integration).

    Conventional radars have only one-half to one-third of the range of an active, electronically scanned array (AESA) radar. Moreover, the movement of a conventional, mechanically-scanned radar antenna provides a tell-tale glint of radio frequency (RF) reflections to enemy aircraft with advanced radars. Such reflections slash at the effectiveness of a stealth airframe. China is known to be pursuing newer radar technology.

    “It's too early to tell the true status of the Chinese AESA program,” says a Washington-based intelligence official. “We've seen lots of press and airshow info on the program, but that doesn't automatically translate into a robust development or give us an accurate look at where the PRC is as far as fielding one anytime soon.

    “Like the [high-performance] engine, it'll be a challenge to take the step from older radars to one designed for a 5th-Gen fighter,” he says. “Again, though, the J-20 is just the first or second -- depending on whom you believe -- prototype into a very long development program.”    

    A two-seat J-10 fighter acted as chase plane for the J-20 during the flight

    Photographs show the J-20 flying at shallow angles of attack and with its undercarriage extended. An observer posting minute-by-minute reports of proceedings to the Global Times, apparently from the fence at Avic’s Chengdu facility, said at 12:50:08 local time (04:50:08 GMT) that the aircraft had begun moving, following a second later with “accelerating” and at 12:50:16 “flying”. The landing was reported 18 minutes later.

    Two passenger aircraft, one a 737, arrived at the Chengdu facility less than an hour before the J-20’s takeoff, presumably carrying important officials. The Chengdu plant is part of the Avic combat aircraft division, Avic Defense.

    “Chinese military [sources] are saying that the first test pilot for the new Chinese fighter is Liang Wanjun,” the analyst says. “He has previously test flown the J-7, J-10 and JF-17. Liang has a total of 2,300 flying hours, joined the PLAAF in 1982 and became a test pilot in 1998.

    It is unclear whether the J-20 is a prototype or only a technology demonstrator. Either way, it is not the only program for an advanced combat aircraft.

    The deputy chief of the air force, He Weirong, said in November 2009 that in 2017-19 China would field a “fourth-generation” fighter, which in China means an aircraft of the F-22’s technology level. He was not referring to the J-20, however, because a month later a prominent news report in English quoted the People’s Liberation Army Air Force (PLAAF) as saying that the 2017-19 fighter would be an improved J-10. It is possible that the 2017-19 fighter is a supercruise version of the J-10 since the Chinese navy has expressed the need for an aircraft that can maintain fuel-efficient, long-distance, supersonic flight, a necessity for keeping enemy forces away from the coast of China.

    The Chengdu J-20 design has struck most analysts and observers as familiar and somewhat different that the Lockheed-Martin F-22 and F-35 as well as the Sukhoi T-50.

    “The J-20 is reminiscent of the Russian MiG 1.42 both in terms of planform, and also with regard to the rear fuselage configuration,” says Douglas Barrie, senior fellow for military aerospace at London’s International Institute for Strategic Studies. “The most obvious difference is the greater forward fuselage shaping as the basis for low observable characteristics, along with the different engine intake configuration. The MiG program was cancelled by the Russian government around 1997.”

    Others note that the planform also has a resemblance to Sweden’s SAAB Viggen.

    Another issue that will continue to surround all stealth designs is how long will current stealth designs offer invulnerability as air defenses adopt even larger and more powerful AESA radars. From the early days of AESA development, a key goal was to build a radar that can detect a very small object like a cruise missile at a distance great enough to target and shoot it down or a larger object like a fighter with a very low observable treatment.

    Airborne detection of stealth aircraft may have already been accomplished in a series of tests done at Edwards AFB, Calif. in the second half of 2009. Those with insight into the research say Lockheed Martin’s CATbird avionics testbed –a 737 that carries the F-35 joint strike fighter’s entire avionics system -- engaged a mixed force of F-22s and F-15s and was able to target the F-22s.

    "The F-35 mission systems suite is the most sophisticated and powerful avionics package of any fighter in the world," said Dan Crowley, Lockheed Martin executive vice president and F-35 program general manager at the time of the tests.

    His clue about the fighter’s anti-stealth capability is in a reference to confronting new, sophisticated, foreign aircraft.

    “The F-35's avionics include on-board sensors that will enable pilots to strike fixed or moving ground targets in high-threat environments, day or night, in any weather, while simultaneously targeting and eliminating advanced airborne threats,” Crowley said.

    Tags: ar99, J-20

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