By Andrew Erickson and Gabe Collins

In the span of a week, Chinese government vessels have been dispatched to waters near the contested Senkaku/Diaoyu Islands, anti-Japanese riots have erupted in major Chinese cities -- and a new highly-prestigious piece of military hardware has been unveiled.

Tiexue.net Photos posted the Chinese military discussion forum Tiexue.net purportedly show a new stealth jet being developed by the Shenyang Aircraft Corportation referred to by some analysts as the J-31.

As if U.S. Secretary of Defense Leon Panetta didn’t have enough to contend with on his current China visit, photos leaked online on Sunday suggest Shenyang Aircraft Corporation (SAC) is making substantial progress on a stealth aircraft prototype, which Chinese netizens and foreign analysts have variously dubbed the “J-21,” “J-31,” and “F60”—a possible future export variant. SAC itself seems to have painted a “31001” designation on the aircraft. (For purposes of consistency, we will henceforth refer to the aircraft as the “J-31.”) The timing of the photo release echoes the events surrounding former Secretary of Defense Robert Gates’ January 2011 visit to China, when the PLA conducted a surprise test flight of Chengdu Aircraft Corporation (CAC)’s J-20 late-generation strike fighter prototype.

In June, Internet photographs and video clips of a heavily-wrapped aircraft being transported by truck appeared. Coupled with previous reports of a J-31 program, this suggests that direct competition has been introduced between CAC and SAC, obviating earlier geographic division of labor that insulated military aviation manufacturers.

Two additional possibilities also raise interesting questions: First, some observers suggest that twin-wheel nose landing gear hints at carrier operations, rendering it strategically noteworthy as the PLA Navy prepares to commission its first carrier, the Liaoning, although the J-31’s configuration and structural outlines may make that unlikely. Second, while the aircraft undoubtedly draws on significant indigenous capacity, it also appears similar in shape and size to Lockheed Martin’s F-35 Lightning II. In a report in March, The Australian quoted “senior security figures” saying hackers from China cracked into British defense firm BAE Systems’ computers and siphoned off large amounts of data on the design, performance, and other characteristics of the F-35. Elements of the J-31’s general configuration and contours also resemble those of Lockheed Martin’s twin-engine F-22 Raptor.

While previous Chinese aircraft were generally copies or emulations of a single foreign design, China’s J-31 and J-20 appear to draw on multiple foreign sources, as well as increasingly-robust indigenous design capabilities. This may enable Chinese solutions that have advantages over American ones in some respects. For instance, the basic configuration and possibly weight class of both Chinese aircraft are much more similar to each other than those of the F-22 and F-35, which might enable the Chinese planes to use one common engine, or at least a common base variant. This could reduce R&D costs and enhance operational readiness.

The J-31’s twin-engine configuration could indicate higher take-off weight than similarly-sized foreign aircraft like the F-35. This could be driven by higher fuel loads which, in turn, might suggest designs to enhance range and loiter time for reconnaissance and attack. Those might be compatible with long-range, “over water” operations. Based on this apparent potential for significant fuel and weapons loads, the J-31—- like the J-20 —- may be armed with air-to-air and air-to-surface missiles of sufficient range to pursue strike missions against slow-moving and relatively vulnerable early warning and tanker aircraft, as well as surface ships. Such an approach would pit missiles, a traditional Chinese strength, against key American and allied vulnerabilities.

Alternatively, the J-31’s twin-engine design could also reflect design inefficiencies that would increase the net weight as compared to U.S. airframes of similar size or even lack of trust in the reliability of engines currently available. A single-engine design such as the F-35 for naval operations implies an extremely high degree of confidence in engine reliability.

The bottom line is that much of the J-31 and J-20’s performance will hinge on the parameters and quality of their engines, one of the greatest areas of weakness for China’s aerospace industry but one that has been prioritized for improvement, with Russian imports as a stopgap in the meantime.

Images that appear to show China's J-20 prototype stealth fighter jet, unveiled during U.S. Secretary of Defense Robert Gates’ January 2011 visit to Beijing, during a 'taxi test' at a facility in western China.

Neither the J-31 nor the J-20 has demonstrably advanced beyond the prototype stage, although at least two J-20 airframes have undertaken at least 53 test flights, according to Xinhua. It is too early to determine the extent to which they will succeed, when precisely they will be operational, the extent to which they can utilize indigenous engines, whether they will truly have “stealth” capabilities, and whether those would entail primarily forward stealth or all-aspect stealth. Stealthiness depends not only on geometry but also on radar-absorbent coatings on exterior surfaces (pdf), particularly the leading edges of wings and other reflective points. This “sensitive skin” degrades constantly and has to be maintained vigilantly to retain its effectiveness, but China lacks experience with such “defense dermatology.” Until such a capability is demonstrated, it is better to refer to the J-31 and J-20 as aspiring to be “low observable.”

But what already appears clear is something far more significant for long-term Chinese military aircraft development: Beijing has finally decided that it can sustain multiple overlapping advanced programs. China’s shipbuilding industry—which, aside from its missile and electronics industries, produce its most advanced defense products—has already proven able to do this with its simultaneous construction of multiple modern submarine and warship classes. Now China’s military aviation industry, which has traditionally lagged, also appears to be making this important strategic breakthrough.