Allegations China Stole F-35 Design to Make J-20, FC-31 Based On Superficial Evidence

China has long been accused of stealing US defense technology and its weaponry is derided as “copycats” of US equivalents, but the allegation rarely extends beyond superficial supposition.

Chengdu Aerospace Corporation’s J-20 “Weilong” is China’s answer to the United States’ fifth-generation stealth aircraft, the F-22 Raptor and F-35 Lightning II. While the planes are comparable in many ways, their superficial similarity is often judged by defense commentators as proof that Chinese engineers stole the design from Lockheed Martin. As J-20s begin to fill squadrons in the People’s Liberation Army and a generalized fear of Chinese firms as dishonest international players is increasingly propagated by Western powers, the attacks on the J-20’s origins have only increased.

Early last month, then-US National Security Adviser John Bolton put the issue in no uncertain terms, saying “the fifth-generation Chinese fighter aircraft looks a lot like the F-35, that’s because it is the F-35. They just stole it.” Bolton could be referring to the J-20 or to Shenyang’s FC-31, a testbed the PLA hasn’t yet committed to adopting.

On Saturday, the foreign policy publication The National Interest published a piece forwarding the idea once more, reviving a Task & Purpose article from August 2018 and calling it “an outrage,” stating unequivocally the “key point” was that “Beijing has long stolen foreign technology and used it to reverse-engineer its own weapons.”

Asia Times then presented Bolton’s comments, made at a press conference in Kiev, alongside the Task & Purpose observations, as a “report,” endowing them with a further air of legitimacy.

​Similar allegations have been made against Harbin’s Z-20 helicopter, derided as a “copyhawk” ripoff of the UH-60 Black Hawk chopper it will replace. As Sputnik reported, this is also a superficial judgment, as the helicopter differs significantly from Sikorsky’s in its engines, fly-by-wire controls, avionics and other features.

Likewise, Shenyang’s “Sharp Sword” carrier-based drone is said to be a stolen design from Boeing, since the Chinese UAV and Boeing’s MQ-25 Stingray both utilize a flying wing shape and fly from carriers.

However, the claim also raises the question: if China copied the F-35, how come the J-20 isn’t a malfunctioning, underperforming money pit like Lockheed Martin’s plane is?

So what’s the big proof that the J-20 “is the F-35”? Well for one, the J-20 sports a sensor system that “looks awfully similar” to the F-35’s Electro-Optical Targeting System (EOTS) sensor. What’s that similarity? Well, as Task & Purpose is forced to concede, the two systems “are not identical,” but they are both mounted in similar places under the nose of the aircraft. That’s different from Russia’s Su-57, in which Sukhoi put an infrared tracking system on the top of instead of underneath the nose.

Further, “parts of the design of the J-20 appear to resemble the F-22 and it’s stealthy curves [sic],” Task & Purpose said, although it immediately concedes that “these similarities could be skin deep,” going on to note several differences.

All in all, T&P’s report is measured in its suspicion. By the time this story got to Asia Times, though, the similarities became “striking,” and the stealthy curves don’t just resemble, they “mimic” the F-35.

Fueling the allegations are that in 2007 and again in 2017, Chinese hackers were implicated in the theft of technical documents relating to the F-35 program in the US and Australia. However, with the J-20 flying for the first time in 2011 and the FC-31 in 2012, the claim that these hacks could’ve been used to affect the design of either jet is shaky at best. Further, there’s no specific reason to assume that Chinese hackers, whether they were private or state-backed, aimed to supplement Chinese aircraft design. Just as likely are the possibilities that either the hackers wanted intelligence on US jet capabilities, or even simply to sell the information for a profit.

A quick look at the dimensions of the jets should have been enough to dispel Bolton’s claim that either jet is an F-35 copy, though:

​It’s immediately obvious that the J-20, for whatever “similar curves” it has to the F-35, is a much larger aircraft, measuring in at 21.1 meters as opposed to the F-35’s 15.67 meter length. While it’s not on this chart, the FC-31 (seen above as the “J-31”) is reported by Air Force Technology to have a length of 16.9 meters, still longer than Lockheed’s jet.

Another huge difference hinted at by T&P is the engines: the F-35’s only got one engine, while both the J-20 and FC-31 have two. The difference isn’t insignificant; it can substantially affect the implications of other parts of the plane’s design, including its stealthiness. You couldn’t, for example, steal an F-35’s airframe and put two Russian-made engines on it, which seems to be what Asia Times thinks Beijing has done.

The South China Morning Post noticed this, noting that Bolton might’ve been talking about the FC-31 instead of the J-20, but overall ignoring their own evidence arguing against a theft of the design and confining themselves to a comparative review of the jets.

Moreover, superficial similarities between aircraft are as old as the flying machines themselves, making identifying the decade in which a jet was designed a fairly easy task in most cases. Planes built today don’t look like postwar jets, even though in some cases those planes themselves remain in service.

In a June white paper on US-Chinese trade and economic consultations published by China’s State Council, Beijing rejected the accusation, stating that “China resolutely opposes forced technology transfer and is taking decisive measures against theft of intellectual property. Accusations of forced technology transfer against China are groundless and untenable.”

That’s not to say Beijing hasn’t reverse-engineered a plane before, though: Shenyang’s J-15 is heavily based on a Sukhoi Su-33 prototype bought from Ukraine, the T-10K-3, itself a version of the Su-27 modified for carrier use. The J-15 fills the same role for the PLA Navy today. However, this is an example of legal technology transfer, which the white paper acknowledges is incredibly important to the Chinese economy and highly encouraged.