China Claims Innovation in J-20 Weapons Bay Design

 - April 5, 2013, 1:00 PM
The second prototype of China’s J-20 combat aircraft taxiing with its starboard weapons-bay door open and a PL-10 air-to-air missile protruding. (Photo: Chinese Internet)

China’s under-development J-20 combat aircraft recently demonstrated its missile-launch mechanism, which the Chinese media tout as a simple but “more efficient” design than that of the American F-22.

J-20 number 2002, one of the two prototypes that have been made known to the public, carried a short-range air-to-air missile (AAM) aft of the air intake. The missile, identified as China’s newly developed PL-10, was shown in a video inside the starboard intake weapons bay before being moved outside the airplane by an ejection system. The door of the bay then closed, leaving the missile outside, but still attached to the airframe.

This arrangement is said to allow the missile to be fired in the shortest time possible. In the F-22 design, the door of its side internal weapons bay has to remain open for the launch of a missile, thus possibly compromising its stealth capability. By contrast, the J-20 could stay stealthy throughout the missile-launch process by keeping the bay door closed.

Despite the Chinese media’s acclaim for the J-20’s missile launch mechanism, Chen Kuo-ming, senior editor with the Taiwan-based Defence International magazine, said what’s more important is whether the J-20 could fire short-range AAMs from off-boresight angles as acute as those possible from the F-22. For the moment, the PL-10 does not seem to be comparable to the AIM-9X AAM of the F-22 in respect to off-boresight capability.

The J-20 is expected to begin air-to-air weapons firing tests soon. It carries two short-range PL-10s, one in each air-intake bay, and six to eight medium-range P-12s in the main internal weapons bay below the mid-fuselage.


One of the major problems is that the US under the Obama Admin capped production of the F-22 Raptor fighter jet at just 187 and did not authorize for further development of the aircraft; thus except for minor changes, the F-22 Raptor is as good as it's going to get.

Is it just me, or does anyone else think the photo accompanying this article looks photoshopped.

Yea, I'm no pro, but the grass in the foreground looks 100% photoshopped.

The grass and white stripe on the runway clearly look photoshopped on the left hand foreground. I suspect to remove some identifying features of the location, shadows, people, equipment, etc.

Whether you have your weapons bad door open or you have a big, honking missile hanging off the aircraft won't matter. Your stealth capability is going to be compromised to some degree. Probably more with the missile hanging out there.

Try again, China.

It is said that the Chengdu J-20 Chief Engineer, Yang Wei, is a very talented designer and manager of Engineering talent, in the mold of Kelly Johnson. There is nothing he has done on either the J-10 or the J-20 that diminishes this observation.

Photoshopped or not, other images and video footage demonstrate this ability to position an internally carried store outside the aircraft (captive or for launch) with the bay doors closed on a low profile pylon. This is something that no other production fighter aircraft is capable of doing which, yet again, supports the view shared by many defence analysts, including colleagues in Russia and India, that this aircraft (the J-20) is a game changer that will be evolved and, thus, with us for some time to come.

What everyone should be concerned about is the fact that the F-22 production line was shut down for what should now be seen as obvious "falsifications" about the number of F-35s that would be available at the time the J-20 would supposedly be coming online. The F-35 pogram is a mess, and the J-20 Program is already showing a level of maturity and program focus that SHOULD seriously draw into question whether the F-35 really IS going to massively outnumber fighters like the J-20 and J-31in the early 2020s; or even whether the F-35 kit is going to be ready in that time frame... If you notice, F-35 IOC dates are being pushed up, a clear indication that the JSF partners want to at least give the impression that they "got this". China does NOT have to produce a state-of-the-art anything to challenge the -35 and consequentially bring enormous pressure upon the tiny F-22 fleet that the powers-that-be were so confident weren't needed (i.e., let's remove the competition, that'll make the JSF successful... how's that worked for us?). The fact of the matter is that if the Chinese follow a conservative approach of justfielding their AESA/stealth package, they have a legitimate chance of fielding these things in enough numbers, with a low enough price tag, to seriously threaten the whole F-35 ideaology. Air superiority is NOTHING to trifle with. An air superiority fighter can be adapted to ground attack, but you end up with a mess going the other way, especially in 3 variants (history is available to support this fact, but JSF conveniently ignored it). So my underlying question is this: What sort of mindset would cancel an operational, highly upgradable air dominance platform like the F-22, with its expanding capabilities, falling costs, and THE most capable airframe out there, especially considering the problems everyone's known for a LONG time would occur with an overly-ambitious "pyramid scheme" like the F-35??? That kind of mindset is the REAL threat, because it's the exact reason WHY the J-20, J-31, and T-50 are the very threats they shouldn't even be - Not threats to the F-22, but to every OTHER aircraft out there where F-22 class aircraft are not providing air superiority; and since there are no more -22s in the works, and they are off-limits to non-U.S. partners, and there are a very limited number available, and the Chinese are probably going to be able to mass-produce these threats, we're all left to hope that the J-20, J-31, and T-50 really DO run into the major problems that the JSF program has been gambling our and our allies' security on! Gates and this administration should be as disgusted with themselves as we are with THEM... yeah, right.

It's not what the RCS looks like when the Pili is hanging that matters. It's what it looks like when the bay is closed up. In this, you are creating three little notches in the panel outline whose altered material densites and potential dielectric 'look thru' on the heavy steel arms will all be vulnerable to travelling wave entry and cavity backscatter.

This is an important facet of LO which people don't understand well in that the aircraft have both an optical (mirror scatter) and resonant dipole (tuning fork) response to radar and -any- surface discontinuity whether physical outline gap, or material type change can alter the surface impedance factors enough to cause backscatter along the illumination bearing.

It can also effect the surface tensions of the surrounding skin, causing, as this photo shows-

The door above the cutouts to not close fully.

Whether due to a change in the outline profile of the door, the bay panel surround or the way the two seat together, due to negative pressure or thermal or simple suction flex of the composites, something has happened to alter the fit of the door in the composite skin and this has the further potential to crush or gall the panel so that it begins to delaminate.

Because of this, it's just not wise to go cutting little bits out of composites as every corner becomes a crack multiplier and every altered thickness changes signature and material strength properties of the skins as a whole.

IMO, the biggest problem the J-20 has is the foolish copying of the same approach to 40nm LRAAM (AIM-120D as PL-21) and 10nm SRAAM (AIM-9M as PL-10) that the F-22 uses.

In that this is a very large plane, not a dogfighter you don't want to commit to closure past the radar merge at about 15nm. Particularly in the SC&M regime above 40,000ft, the utility of lightweight missiles is highly questionable anyway as their total motor impulse and aero vs. body lift just isn't that great.

A 20nm MRAAM makes much more stepped-engagement distance sense as a weapons mix with longer ranging ramjet weapons but try integrating a PL-12 within that bay aperture and, even if it's possible (10 vs. 13ft weapons) for length, you will find that all the rail swing arms have to be relocated to accommodate the different transverse and longitudinal loads of a 400lb vs. 200lb class missile with a vastly more energetic motor.

Neat gimmicks do not always make for sensible working systems.