A second Chinese stealth fighter, apparently from Avic’s Shenyang plant, has appeared in seemingly genuine pictures that cropped up on Chinese web sites Sept. 15.

The twin-engine, single-seat fighter, shown at an airfield, appears to approximate the Lockheed Martin F-35 in size, with a somewhat shallower body but a similar span of about 11.4 meters (37.5 ft.), as indicated by comparison with a commercial aircraft tug shown pulling it.

The aircraft features a large ventral weapons bay. Wing sweep looks to be less than 45 deg. on the leading edge, as it was on a wrapped fighter-like object that was hauled by road from Shenyang to Xi’an in June. That trucked object could well have been the now-assembled prototype, three photographs of which have appeared.

Whenever photographs of new weapons appear on nonofficial web sites in China, the risk of fakery is at least as great as elsewhere. But the publication and sustained appearance of the three shots on the large Chinese web portal Sina somewhat supports their veracity.

The source of the pictures is unknown; assuming they are real, they are probably official but unacknowledged, intended to let the world know how far China has gone in developing a smaller companion to the so-called J-20 fighter of Chengdu Aircraft, Shenyang’s rival.

Moreover, the photographs have evidently been staged with the intent of not only revealing the fighter but also letting observers easily measure it and appreciate some of its features. The object hauled on the back of a truck in June was similarly placed next to objects of known size to aid photometric analysis.

Among the most distinctive features on the prototype are doors for the weapons bay. They were about a third as long as the whole aircraft, meaning that the bay must be at least 5 meters long. Assuming that the Chinese military has deliberately revealed the prototype, it surely opened the doors just as deliberately, to show the location and size of the bay. Similarly, a directly head-on shot conveniently showed trapezoidal intakes much like the F-22’s and the angle of the twin canted fins and lower body, about 25 deg.

The engines could well be Klimov RD-93s, which have been imported from Russia for the JF-17 export fighter. If so, a Chinese engine would presumably follow. The engines appear to be installed aft of the bulkhead that carries the main landing gear. The exact routing of inlet ducts, a key issue in reducing radar reflections, could not be judged, but a bulge on top of the fuselage shows that they rise well above the wing.

The location of the prototype was not clear from the photos, but Xi’an, the destination of the trucked object in June, has a flight test center. While China has not officially acknowledged the existence of the Shenyang aircraft, it has been popularly called J-21 or J-31. Shenyang displayed a model of a similar aircraft labeled F-60 last year. The prototype differs at least in having different moveable wing surfaces and in lacking a stinger between the nozzles.

Simultaneous development of two stealth fighters indicates the allocation of enormous resources by China. But if the country is to continue to catch up to Western fighter technology, it probably cannot afford first to get the J-20 into service and then to move on to a smaller aircraft as a replacement for Chengdu’s J-10. The J-10 began large-scale entry into service in 2006 and is unlikely to be considered fit as a first-rank aircraft in the late 2020s.

Also, China will want a domestically built fighter for the aircraft carrier it is now testing, as well as any follow-on ships. The J-20 is probably too large for carrier use. On the other hand, views of the truck-hauled object suggested that the Shenyang fighter had only a modestly sized wing; carrier aircraft need relatively large wings. Conceivably, a big-wing carrier version of the new fighter could be built, like the F-35C.