Jan 3, 2011
By Bill Sweetman
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.
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