As much as the resources wielded by the Chinese state aerospace industry impress outsiders these days, few could have expected that one of the companies in the sector would want to produce a stealth fighter on its own account.

But that is just what Shenyang Aircraft wants to do. Equally surprisingly, the Chinese air force is turning its nose up at the result. What looks like a thoroughly modern stealth fighter is apparently not good enough to serve as China's next medium-weight combat aircraft.

After three evidently staged appearances of the real aircraft this year, Avic displayed a model at Airshow China in Zhuhai last week, displaying the fighter that is unofficially called the J-31 and known to come from Shenyang. The aircraft is being developed “for the international defense market,” says Avic.

The model was labeled as a concept fighter, but it showed few if any differences from the real aircraft that appeared first under wraps on a truck in June, then being pulled around an airfield in September and, finally, on Oct. 31, in the air, prominently numbered “31001” and possibly making its first flight. It is clear, then, that the project has transcended the concept stage.

The aircraft has been designed to deliver a highly stealthy configuration at low cost, with a heavy weapons load capability over a wide combat radius, says Avic. The model is a single-seat, twin-tail, twin-engine aircraft with a high wing, like the real aircraft seen in unattributed photographs on the Internet. As described at the show, the fighter has a typical takeoff weight of 17.5 metric tons, is 16.9 meters (55.5 ft.) long and 4.8 meters high with a wingspan of 11.5 meters.

The aircraft that flew last month has two Klimov RD-93 engines, which project engineers do not regard as sufficiently powerful, industry executives say. As fitted to the JF-17 (or FC-1) single-engine export fighter from Shenyang's rival, Chengdu Aircraft, the RD-93 produces 19,000 lb. thrust. Regardless of the RD-93's power, Shenyang needs a Chinese engine if it is to avoid Russia holding a veto over J-31 sales. Judging from photographs of the prototype, the nacelles may be designed for engines larger in diameter than the RD-93, a derivative of the MiG-29's RD-33. The alternative may be the reported WS-13 Taishan from the Guizhou plant of propulsion specialist Avic Engine.

Avic says the J-31 has a combat radius of 1,250 km (780 mi.) on internal fuel or 2,000 km with external tanks. Maximum speed is Mach 1.8, takeoff distance is 400 meters and its landing distance 600 meters.

“Operational effectiveness will be higher than current or upgraded fourth-generation fighters or almost equivalent to typical fifth-generation,” says Avic. The reference to fifth-generation aircraft presumably indicates the Lockheed Martin F-22 and F-35.

The J-31 is known to come from Shenyang because the company displayed a flyable model of a similar fighter last year with the designation F-60 and because a wrapped object that was presumably the real aircraft was trucked in June from Shenyang to Xian, where China has a flight-test center.

The designation “J-31” may be no more valid than the widely assumed but unconfirmed moniker “J-20” applied to a larger fighter from the Chengdu fighter works. The Shenyang aircraft is also sometimes called J-21—again, without any certain validity. The J-20 was revealed in late 2010 and appears to have made its first flight in January 2011. It was not promoted at Zhuhai.

And therein lies a key piece of evidence of the status of the J-31. The J-20 was not at Zhuhai because it is not for sale and because China does not want to reveal too much about it. It is intended for the Chinese air force.

Conversely, because the J-31 was exhibited at Zhuhai and is promoted as an export product, the Chinese air force obviously does not want it. Early production of a fighter intended for Chinese service would be reserved for the air force, as has been Chengdu's J-10, the current Chinese medium-weight fighter.

Why, then, has Shenyang developed it? There are a few possibilities. It could be a technology demonstrator funded by the military, one that the company's management thinks has good potential for full development as an operational fighter.

Alternatively, it could be an internally funded program for the export market, as the company seems to suggest, encouraged by the knowledge that not all countries have access to Western fighters. The J-31 would mainly be a competitor to Russian fighters—though Shenyang might also be calculating that buyers of Western equipment will want more choice as some U.S. and European types go out of production over the next decade or two. Importantly, the Chinese fighter should be cheap, as the JF-17 is, while offering at least the prestige of stealth technology.

Shenyang is working on China's ship-borne fighters, raising the possibility that the J-31 was at one time intended for the newly commissioned aircraft carrier Liaoning and its successors. If so, it probably is not now destined for such service, since the navy, like the air force, would not want to exhibit an aircraft that it intended to operate.

The difference in the sizes between the J-20 and J-31 indicates that they have probably not been designed for the same requirement. Moreover, Avic makes no mention of any domestic use for the aircraft.

A foreign aerospace executive with insight into Shenyang and the wider Chinese industry has perhaps the simplest explanation for the J-31's existence: “This is the program of a company that has more engineers than it knows what to do with.”

While a prototype or technology demonstrator is flying, a key question is whether much progress has been made in developing low-observability features that are easily maintained and do not encumber the aircraft with much weight. An even greater challenge for Shenyang and its suppliers to overcome is fitting the aircraft with electronic systems that merge the inputs from various sensors to give the pilot situational awareness. Avic's statement that the aircraft will offer capability “almost equivalent” to the latest U.S. fighter suggests that it aims to go some way in that direction.

And yet that could all be far away. There is a world of difference between, on the one hand, flying an aircraft that from the outside looks like a fighter and, on the other, building an operational combat aircraft. The F-35 will go into service almost 20 years after the first flight of its X-35 technology demonstrator. Similarly, Shenyang may so far have little more than a bare aircraft that an “export” customer would be expected to help fully develop, or at least fund, as Pakistan has with the JF-17.

Avionics immaturity may be the reason why the J-31 is an export-only aircraft, even though it seems well-sized as a successor to the Chinese air force's J-10 and as a cheaper, large-production complement to the J-20. The air force may well have decided that Chinese industry has enough of a challenge in improving the J-10 and integrating systems for the J-20. But yet another possibility is that Shenyang or Chengdu is cooking up something more advanced than the J-31. With no clear answer, that probably remains the key mystery about the J-31: Why does the Chinese military not want it?

Reviewing the J-31's configuration, it appears that the designers have aimed for an aircraft that has stealth but also conventional fighter versatility, and they are not trying to achieve supersonic flight without afterburning, as the F-22 does. The choice of a quad aft-tail arrangement—two horizontal and two vertical stabilizers—indicates the designers wanted to combine low radar reflectivity with high angles of attack and therefore easier handling in combat, which that would have been hard to do with a canard configuration.

The aft-tail layout also puts hard points close to the center of gravity, probably making the carriage of stores easier and thereby promoting versatility. Photographs of the aircraft at an airfield in September revealed the doors of a large ventral weapons bay.

The model has only moderate sweep on the leading edge of the J-31's wing. To minimize radar reflections, air inlets for the engines have no boundary-layer diverter plates. The nose volume is not large, leaving room for only a modestly sized radar antenna.

For all its habitual secretiveness, the Chinese military displayed two recent attack helicopters at Zhuhai for the first time. One of these was the Z-10 (or WZ-10), which Chinese media suggest is sized between the Eurocopter Tiger and Boeing AH-64 Apache. It is a product of the Changhe works of Avic rotary-wing specialist Avicopter.

The other was the Z-19, an adaptation of the Z-9 and, ultimately, Eurocopter AS352 Dauphin, but with a new fuselage and tandem seating. As a Dauphin derivative, the aircraft should have a gross weight of 4-5 tons, making it somewhat smaller than the Z-10. Harbin Aircraft, also part of Avicopter, builds the Dauphin derivative. It did so originally under a license that Eurocopter says has expired.

Both attack helicopters are powered by Chinese engines, says Avic. The Z-10, at least, has reportedly been fitted with foreign engines during development.

Harbin has also developed an attack version of the Z-9 that retained the bulky cabin of the original utility helicopter. The Chinese army allowed rare close inspection of a recent version, the Z-9WZ in July.