20 January 2011

Chinese J-20 Stealth Fighter Not So Advanced After All

The initial concern over China's stealth fighter may have not been warranted according to this report.
China’s newest combat aircraft prototype, the J-20, will require an intense development program if it is going to catch up with fast-moving anti-stealth advances.

In fact, anti-stealth will bring into question all stealth designs: How much invulnerability will current low-observability techniques offer as air defense systems adopt larger and more powerful active, electronically scanned array (AESA) radars? From the early days of AESA development, a key goal was to build a radar that could detect very small objects—such as 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 already be an operational capability. In a series of tests at Edwards AFB, Calif., in 2009, Lockheed Martin’s CATbird avionics testbed—a Boeing 737 that carries the F-35 Joint Strike Fighter’s entire avionics system—engaged a mixed force of F-22s and Boeing F-15s and was able to locate and jam F-22 radars, according to researchers. Raytheon’s family of X-band airborne AESA radar—in particular, those on upgraded F-15Cs stationed in Okinawa—can detect small, low-signature cruise missiles.

Moreover, Northrop Grumman’s lower-frequency, L-band AESA radar on Australia’s Wedgetail airborne early warning and control aircraft is larger and potentially more capable of detecting stealth aircraft at longer ranges.

Lockheed Martin also hinted at a JSF anti-stealth capability in 2009 in a reference to combat with sophisticated, foreign aircraft. “The F-35’s avionics include onboard 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,” said Dan Crowley, then-executive vice president and F-35 program general manager.

Better images emerging from China point clearly to the J-20’s use of stealth technology, but major uncertainties and questions remain unresolved.


The biggest uncertainty about the Chinese design concerns the engine exhausts, which as seen on the prototype are likely to cause a radar cross-section (RCS) peak from the rear aspect. One possibility is that a stealthier two-dimensional nozzle will be integrated later in the program; however, the nozzles on the current aircraft show some signs of RCS-reducing sawtooth treatment, suggesting that the People’s Liberation Army has accepted a rear-aspect RCS penalty rather than the much greater weight and complexity of 2D nozzles.
By: Shelldrake

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