Submarine Matters studies, above water, jets sometimes.
At one of China's major weapons PR events (the China International Aviation & Aerospace Exhibition, Zhuhai city, Guangdong Province) China showcased the beginnings of a technology demonstrator - which may become a Chengdu J-20 stealth fighter in a decade.
The J-20 has:
- the splayed out tail of a 26 year old YF-23 technology demonstrator, and
- canards like the Saab Gripen and some other fourth generation jets.
Aircraft aficionados will recall that the YF-23 competed against and to the Lockheed YF-22 in 1991 in what effectively became the US stealth superiority fighter fly-off. China, like Russia and India, all have optimistic visions of developing stealth air superiority fighters in a mere 5-10 years time. This is unlikely. See the list of just some stealth requirements below.
1. The easiest part is putting together impressive looking angles, by minimising verticals, to try to make the aircraft look flat - essentially a flying wing. Jack Northrop achieved a semi-safe flying wing by 1943.
2. The next most obvious attempted stealth qualities is how it moves using its jet engines. Recessing the engines so they will be less noisy and (most important) their heat signatures don't show much, and don't attract missiles, is difficult.
The F-22 can supercruise - the F-35 cannot. With relatively low fuel use an F-22 can rely on the "cruise" setting of its engines to achieve supersonic speeds. That is, there is no need to use loud, hot, after-burners. Afterburners flames can be seen at night, infrared detecters can also see them. Sensor/missile combinations can shoot after-burners users down.
The ability of an engine to efficiently and regularly thrust-vector is also important to stealthy/Fifth generation air superiority fighters. In that respect Russia, and many other observers, believe China really made a long fought deal to receive examples of Russia's Su-35 fighter in order to reverse engineer the jet engines that the Su-35 uses. Creating a Chinese copy of Russia's AL-41F1S series engine may be a prime Chinese intention.
3. Those with passive electromagnetic reception gear might be able to assess how unstealthy the J-20 radar, communications and other electronic emissions are.
4. Those friendlies with distributed active radar pulses (without the ability to cue a jet in an airshow with their eyeballs) might want to assess how easily the J-20 can be detected and targetted.
5. The radar absorbing presence and aerodynamic effectiveness of the J-20's Radar/Radiation Absorbent Material (RAM) coating (if it has any) would be the next checklist item in an assessment of the J-20's stealthiness. Assessing RAM may be difficult with a flying J-20 at a distance - much easier on the ground chipping off some RAM coating one foot away.
See many of these aircraft stealth requirements here.
The Chengdu J-20 (not yet stealthy) fighter made its first mobile public appearance on October 31, 2016, at China's International Aviation & Aerospace Exhibition, Zhuhai city,
The tentative, gentle movements of the J-20 in its only public flight - is captured in the Youtube above.
The two flying J-20s looked flyable enough for their 25 tonne (near empty) weight and didn't test any major capabilities.
Stealthy weapons bays, if there were any, remained shut. This might mean that the J-20s still need to hang highly unstealthy stores (bombs, missiles, sensor pods and fuel containers) from their wings and centerlines.
In terms of what is seen in the Youtube above it appears the J-20 is at least 25 years behind the F-22 in flight dynamics. However the Chinese are generally subtle in their conventional weapon testing. The J-20 may be capable of much more when the camera isn't looking.