China’s new stealth fighter’s missile launch rails prove Beijing can improve U.S. technology

Mar 26 2013 - 14 Comments

In order to preserve their stealthiness and keep the RCS (Radar Cross Section) as low as possible, radar-evading planes rely on weapons bay: bombs and missiles to be fired are kept inside the bays until it’s time to use them.

For instance, the F-35 can carry one AIM-120D (AIM-120C8), on a trapeze : when needed, the BVR (Beyond Visual Range) missile is lowered into the airstream on the open bomb bay door, and ejected.

F-22 Raptors use canted trapeze to put the AIM-9 Sidewinder seeker into the airstream to achieve a lock on the target as the side bay doors are open.


Image credit: U.S. Air Force

Once the missile is fired, the bay doors close up.

Obviously, such method requires the stealth plane to fly with the open bay doors for a certain amount of time, a condition that can limit the aircraft performance, maneuverability, and increases the overall plane’s RCS, with a temporary exposure of the aircraft to the enemy radars.

Something that can be quite lethal in a Within Visual Range scenario.

The problem is to be partly solved with the use of missiles featuring the Lock On After Launch capability. With this kind of missile (available on the Raptor when the AIM-9M will be replaced by the AIM-9X Block II) the bay doors remain open just the time it is needed to eject the missile into the airstream.

However, China might have found a clever solution to the problem, as the latest images of the J-20 Mighty Dragon stealth fighter jet, emerging from the Chinese Internet, seem to suggest.

J-20 2002 side bay maybe - out mod 2

Indeed, the second prototype of the aircraft features a missile deployment device on the side weapons bay which extracts the selected air-to-air missile and then closes the door to keep the reduced RCS.

J-20 missile deployment device

Simpler and probably cheaper than the use of LOAL missiles, the J-20’s deployment device shows that Chinese engineers are not simply copying U.S. tech: if not improving it, they are at least troubleshooting some of the issues already faced by their American counterparts, with some clever ideas.

Missile launch rail

Graphs from Chinese forums

The missile launch rail was used to carry the PL-10 IR air-to-air missile during tests.

Anyway, it’s worth noticing that along with AIM-9X missiles, the F-22 pilots will receive Scorpion HMCS (Helmet Mounted Cueing Systems) that will be particularly useful in case of dogfight. There are no information about similar helmets being fielded to Chinese fighter planes.

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  • Troy

    Just to clarify……the AIM-9 and AIM-120 are rail launched and not “ejected” like the AIM-7 and AIM-54 were. The thrust of the rocket motor flies it off the launcher rail. Fascinating article on the progress of Chinese espinoge in their attempts to field new aircraft.

    • JohnJubly

      The AIM-120 can be ejector launched.

  • Troy

    I was referring to the F-35 and F-22 as the article referenced those two specific U.S. aircraft. Yes, the AIM-120 can be ejector launched as I loaded quite a few in my Navy days on F/A-18s and the LAU-116s before I joined the Air Force. I tried to keep my comment within the context of the article.

  • OG_Locc

    Interesting idea, and even more interesting that you took that as an “improvement” on US technology. Door closed or door open – a missile hanging on the outside of the aircraft is returning a HUGE RCS.

    • cencio4

      IMO anything that can solve a problem in a fast and cheap way is an improvement of a previous tech suffering that problem.
      Anyway, an open door with a hanging missile returns a higher RCS and, above all, I’d rather maneuver with closed doors in a dogfight

      • Yeah but now that they’ve developed the “lock on after launch” tech, I don’t see them just forgetting about that later. It’s a pretty big flexibility. The next US fighter may require a weapons bay that can close with the missile outside like this though for sure.

  • cencio4

    I’m an eager reader of Ty’s work. And he’s a loyal reader of The Aviationist. We have been contributing with each other for many months as you may have noticed by the amount of cross links.

  • DexterM

    Why does the header say “.. improve U.S. technology”? It is clear that the two systems are completely different. From a mechanical, stealth and dog fighting standpoint the Chinese designed J20 missile launch system is superior to the US designed one.

  • John Tam

    the usa will copy this and claim the chinese stole it through cyber war fare and hacking

    • kb

      Its possible the US will utilize this in some way…but when has the US ever copied a chinese design and claim the chinese stole it from the US first. I just don’t see it.

      • Sam

        of course you wouldn’t be able to see it if they did

  • Dion Jones

    Yes and Russian tanks have had auto loaders for decades. There are several reasons why the M 1 doesn’t.

    The system pictured for the Chinese Stealth require several steps to take place for a launch. Open door, deploy missile, close door, fire, reopen door, acquire missile close door, fire. Now I give the Chinese more credit than that. I would imagine you could fire a missile with the door open. The system can never be as reliable as a missile fixed to a launcher by a well trained human loader. Open door extend rail , fire and fire again. Faster and simpler.

    • xiao ju Lin

      you gotta, lot of missiles to shoot with!!!!

  • Lop_Eared_Galoot

    It’s an interesting concept though one which doesn’t seem to understand the nature of LO as being one of avoidance of material type discontiguities in surfaces.
    Travelling waves respond to variance in EM properties as mass density changes as much as physical aperture gaps.
    Add to this the potential for the actuator notch blockers to physically obstruct door opening/closure with thermal changes in the composites around them causing differential shrinkage/expansion, and you have some big design problems for a minor gain in seeker LOS on what -should be- a LOAL capable HOBS weapon.
    There is already a photo on the net of the side door remaining partially open with the missile extended to support this conjecture of mechanical complexity where it’s not needed.
    Finally, let me add that while this is not the Pili-10 I remember, the fact is that it’s also a short range solution on an exceedingly large jet is highly dubious. The J-20 would benefit, tactically, by making a doctrinal choice to refuse to cross the RCS detection threshold as a function of firing ‘just a couple more’ BVR shots before extending out away from the merge.
    Copying the U.S. solution was a mistake in this case because the original YF-22 was supposed to mount either/or AIM-120 as AIM-9 in it’s side bays and it was the moving of the inlets rearwards to provide a better view for the pilot that shrank the available bay lengths too much to accomplish this.
    The J-20 has such long inlet trunking that it should be no problem to fit a Pili-12C to extended sidebays.