China’s J-20 fifth-generation stealth fighter is the most vaunted aircraft in the People’s Liberation Army Air Force’s (PLAAF) inventory. Its deployments near Taiwan and the Indian border in the past year were clear shows of strength, as was the appearance of 15 J-20s – 10% of the fleet, its largest public display yet – at the Chinese Communist Party’s centenary celebrations in Beijing last month.

The FC-31, the J-20’s lesser-known cousin, isn’t in service with the PLAAF, but a model was recently spotted on a mock aircraft carrier, indicating that China’s navy may adopt the fighter – most likely for use in the future air wings of its new carriers. Little is definitively known about the FC-31, which is also sometimes referred to as the J-31 or J-35, but it does have an interesting history.

Unlike the Chengdu Aircraft Industry Group, which builds the J-20, the Shenyang Aircraft Corporation developed the FC-31 privately and therefore didn’t get the same amount of government support. (Though the FC-31’s development was likely helped by China’s theft of American technology.)

In fact, the FC-31 wasn’t originally intended for the PLAAF, but for the international export market. The jet first flew in 2012 but was not officially revealed to the public until the 2014 China International Aviation & Aerospace Exhibition. Only three prototypes have been built, the last of which was noticeably different than its predecessors. It reportedly conducted a flight test in September 2020.

Despite appearances at trade shows, there haven’t been any foreign purchases of the FC-31. As a result, the Shenyang Aircraft Corporation switched its focus from the international market to trying to make the FC-31 the PLAAF’s newest stealth fighter.

The PLAAF hasn’t shown any interest in the FC-31, but there were reports that China’s navy (PLAN) is looking at the FC-31 as an addition to its carrier-based air wings. The likelihood of adoption by the PLAN seemed to increase last month, when an aircraft model that looked like an FC-31 appeared aboard a land-based mock aircraft carrier near the city of Wuhan.

The mock carrier, built 10 years ago, has been used to test how other aircraft could function on a flattop. The model aircraft was easily recognizable because of its stealthy airframe. It was also sitting near two J-15 fighter models and a model of a Z-18 transport helicopter, both of which are in service with the PLAN.

Heavy Jets

The FC-31 is in many ways designed to compete with the US-made F-35, but with some differences. It is slightly larger and has two jet engines to the F-35’s one. The US Navy’s main fighters, the F-35C and the F/A-18E, both have a top speed of Mach 1.6, while the FC-31 is reportedly capable of reaching speeds as fast as Mach 1.8. (The F-35C is currently limited to operation on just one US carrier.)

Crucially for the PLAN, the FC-31 is as much as 22,000 pounds lighter than China’s current carrier-based fighter, the J-15, which is the heaviest carrier-based fighter in service in the world. The J-15’s weight, combined with the disadvantages of ski-jump carrier design, severely limits the capabilities of the PLAN’s carrier air wings.

But the FC-31 has its own weight problems. Its empty weight is believed to be as high as 38,000 pounds. This affects its maximum take-off weight, which is estimated to be 56,000 pounds. Higher take-off weights require bigger engines and more fuel, reducing the amount of armaments an aircraft can carry.

By comparison, the F-35C has an empty weight of 34,800 pounds (15,785 kg) and a maximum take-off weight of 70,000 pounds (31,751 Kg). The F-35B, the short-take-off-and-landing version that also operates from US Navy ships, has an empty weight of 32,300 pounds and a take-off weight of 60,000 pounds (27,215 Kg).

The F/A-18E has an empty weight of 32,000 pounds (14,514 kg) and a maximum take-off weight of 66,000 pounds (29,937 kg). China’s struggle to produce an efficient high-end jet engine also affects its jets’ weight. The first FC-31 model was fitted with Russian engines, just like the J-20. Better engines would allow China’s fighters to carry heavier loads and operate for longer periods.

Turning the FC-31 into a carrier-borne aircraft would require other changes, like making the wings larger, that would also make it heavier.

New Plane,  New Carrier

The FC-31’s effectiveness and final design will also depend on the PLAN’s carriers themselves.

The PLAN’s current carriers, Liaoning and Shandong, both have ski-jump ramps, which will put the FC-31 at a disadvantage because it will not be able to take off fully loaded. China’s new Type 003-class carrier, currently under construction, will have a flat deck and a modern Electromagnetic Aircraft Launch System, the same as what’s on the US Navy’s new Gerald R. Ford-class carriers.

EMALS would allow the FC-31 and the J-15 to launch fully loaded. Having full fuel and munitions loads will increase the jets’ ranges and fighting capability.

China, like the US, has had difficulty with EMALS. China’s struggles are likely due to its lack of experience with any kind of carrier-based catapult system. The US Navy has used steam catapults for decades and says it is fixing its EMALS issues.

If adopted by the PLAN, the FC-31 will supplement and potentially replace the J-15. (The FC-31 may also fly off China’s proposed Type 076 amphibious assault ship.)

On paper, the FC-31 has advantages over the J-15, which has crashed several times, at least one of which was fatal. The FC-31’s stealth capabilities are also extremely appealing to the PLAN. Global Times, a Chinese Communist Party tabloid, claims that radars can only track the jet from within 31 miles. The FC-31’s appearance on the mock aircraft carrier means “once it is upgraded to suit the needs of carrier operations, [it] could be a top option for China’s next-generation carrier-based fighter jet,” Global Times quoted an expert as saying this month.