Monday, January 3, 2011

China's J-20 Stealth Fighter In Taxi Tests

Jan 3, 2011
By Bill Sweetman
Washington

China’s first known stealth aircraft just emerged from a secret development program and was undergoing high-speed taxi tests late last week at Chengdu Aircraft Design Institute’s airfield. Said to be designated J-20, it is larger than most observers expected—pointing to long range and heavy weapon loads.
Its timing, Chengdu’s development record and official statements cast doubt on U.S. Defense Secretary Robert Gates’s 2009 prediction (in support of his decision to stop production of the Lockheed Martin F-22) that China would not have an operational stealth aircraft before 2020.

The debut of the J-20 was announced in a November 2009 interview on Chinese TV by Gen. He Weirong, deputy commander of the People’s Liberation Army Air Force. The general said a “fourth-generation” fighter (Chinese terminology for a stealth fighter) would be flown in 2010-11 and be operational in 2017-19.

The J-20 is a single-seat, twin-engine aircraft, bigger and heavier than the Sukhoi T-50 and the F-22. Comparison with ground-service vehicles points to an overall length of 75 ft. and a wingspan of 45 ft. or more, which would suggest a takeoff weight in the 75,000-80,000-lb. class with no external load. That in turn implies a generous internal fuel capacity. The overall length is close to that of the 1960s General Dynamics F-111, which carries 34,000 lb. of fuel.

The J-20 has a canard delta layout (like Chengdu’s J-10) with two canted, all-moving vertical stabilizers (like the T-50) and smaller canted ventral fins. The stealth body shaping is similar to that of the F-22. The flat body sides are aligned with the canted tails, the wing-body junction is clean, and there is a sharp chine line around the forward fuselage. The cant angles are greater than they are on the Lockheed Martin F-35, and the frameless canopy is similar to that of the F-22.

The engines are most likely members of the Russian Saturn AL-31F family, also used on the J-10. The production version will require yet-to-mature indigenous engines. The inlets use diverterless supersonic inlet (DSI) technology, first adopted for the F-35 but also used by Chengdu on the J-10B—the newest version of the J-10—and the Sino-Pakistani JF-17 Thunder.

The main landing gears retract into body-side bays, indicating the likely presence of F-22-style side weapon bays ahead of them. The ground clearance is higher than on the F-22, which would facilitate loading larger weapons including air-to-surface munitions. Chinese engineers at the Zhuhai air show in November disclosed that newly developed air-to-ground weapons are now required to be compatible with the J-20.

Features at the rear of the aircraft—including underwing actuator fairings, axisymmetrical engine exhausts and the ventral fins—appear less compatible with stealth, so the J-20 may not match the all-aspect stealth of the F-22. There are two possible explanations for this: Either the aircraft seen here is the first step toward an operational design, or China’s requirements do not place as much stress on rear-aspect signatures.

The major open question at this point is whether the J-20 is a true prototype, like the T-50, or a technology demonstrator, with a status similar to the YF-22 flown in 1990. That question will be answered by whether, and how many, further J-20s enter flight testing in the next 12-24 months.

Developing an effective multi-mission stealthy aircraft presents challenges beyond the airframe, because it requires a sensor suite that uses automated data fusion, emission control and low-probability-of-intercept data links to build an operational picture for the pilot without giving away the aircraft’s own location.

Credit : Aviationweek

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