Chengdu J-20 pictures, analysis and speculation Part II

[Deino]

That's an interesting hypothesis! Over on the Keypublishing forum, somebody posted a close-up taken from below the airborne J-20 and I automatically suspected a fake , because the seeker looked remarkably like the one from the PL-8! Maybe the photo is genuine after all, and it's simply that your theory is correct?

To admit that image is a FAKE and we all know several other images from this artist but since there are a few CG-artists with quite fine contacts to the manufactors it's quite possible that he knows more than we ... (at least more than me :-[ !)

Deino

 

[overscan (PaulMM)]

http://www.china-defense.com/smf/index.php?topic=5901.840


Very nice pic, sharpened a bit to bring out details.

 

[Deino]

Yes, that image was from a flight performed yesterday ... sadly with the bays closed and no PL-10 !

Besides that I'm a bit surprised to see these test in the publiac done at CAC ... I would have expected these to see - if ever - much later or done at the CFTE. MAybe we can see the main-bays loaded too soon.

These are two PL-10-drawings I found in a Chinese forum ...

 

[overscan (PaulMM)]

Been double checking my measurements.

I calculated the ratio of length between missile and J-20 is about 6.7.

Now, using my old calculated length of 20.5m (without pitot) that gives a missile length of 3.04m.

I also calculated the length a completely different way and ended up closer to 19.5m (without pitot). That gives a missile length of 2.9m.

Deino's recent calculations giving 20.35m would imply missile is about 3.0m.

If the 22m length believers are right, then that gives a missile length of 3.28m.

I believe the true length of this missile is likely to lie in 2.9-3.0m range, which means the length of J-20 lies in the 19.5-20.5m range, and probably nearer the top end.

Lots of assumptions made, a clear side on image with the whole aircraft and missile in view would be handy.

For comparison:

IRIS-T - 2.936m
A-Darter - 2.98m
ASRAAM - 2.9m
AIM-9X - 3.01m
R-73 - 2.93m

I'm going to say PL-10 is ~3.0m.

 

[Deino]

...
I'm going to say PL-10 is ~3.0m.

What fits nicely to my theory again of being based on the PL-8's diamete/body, which is exactly 2.99m long !

 

[VH]

The missile firing sequence for J-20 if that is what is being seen with this complicated missile firing - deployment does not make sense. Here is an analysis from a Chinese military site and I agree.


Comparing the F-22 firing a missile to the J-20 doing the same you have these steps
F-22
1. Setup the missile in the bay with the door closed.
2 Open door
3. Fires missile
4. Close door

J-20
1. Opens door
2. Moves missile outside
3. Closes door and setups missile at the same time
4. Fires missile
5. Moves missile launching rail back into bay.
Or
1. Setups missile while in the bay
2. Open door
3. Moves missile out
4. Closes door
5. Fires missile
6. Moves missile launching rail back into bay

Unless the intention for the J-20 is to hang the missile outside during the entire engagement. The F-22 setup is faster.

 

[Deino]

So what's the problem ? If each step requires the same time You might be correct - at the cost of RCS with the bays open for the Raptor - ... otherwise (and since we don't know the time of preparation) this discussion is completely irrelevant.

IMO it's more like ...

J-20 - F-22

1. Setups missile while in the bay with the door closed - Setup the missile in the bay with the door closed
2. Open door and at the same time missile moves out - Open door and at the same time missile moves out (what You forgot for the Raptor)
3. Closes door (lower RCS) - Fires missile (RCS !! due to open bay)
4. Fires missile - Moves missile launching rail back into bay and at the same time close doors
5. Moves missile launching rail back into bay and at the same time close doors - done

As such it all depends on what time You need and at what cost. Both solutions are a compromise and I think it's stupid to simply bash one of them without knowing the time and pros & cons of each solution.

Deino

 

[chuck4]

The J-20 arrangement seems to be designed to minimize the necessary open angle (maybe 30-40 degrees) of the missile bay door during missile deployment, while placing the deployed missile well clear of the arc of its canard deflection.

F-22 style arranagement would seem to require the bay door to open to a high angle (nearly 90 degrees) to enable the missile to shot out through the middle of the missile bay door opening. This would feature seem to be problematic on the J-20 if the J-20's canards were deflected downwards at a high angle. Even if the missile or door doesn't foul the canards outright, at least the blast from missile motor would damage the carards.

Perhaps specification for the J-20 specifically require the aircraft to carry out extreme combat maneuvers involving high AOA and large canard deflection while ready to fire its IR missiles instantly, hence the unusual arrangement.

The fact this unusual arrangement is present on a prototype and tested so early in development phase suggest the J-20 design devoted significant forethought right at the beginning to all aspects of close combat capability. This further discredits the notion that it is a striker, and instead suggests the design requirements for its air superiority capability was thorough and ambitious.

 

[latenlazy]

The missile firing sequence for J-20 if that is what is being seen with this complicated missile firing - deployment does not make sense. Here is an analysis from a Chinese military site and I agree.


Comparing the F-22 firing a missile to the J-20 doing the same you have these steps
F-22
1. Setup the missile in the bay with the door closed.
2 Open door
3. Fires missile
4. Close door

J-20
1. Opens door
2. Moves missile outside
3. Closes door and setups missile at the same time
4. Fires missile
5. Moves missile launching rail back into bay.
Or
1. Setups missile while in the bay
2. Open door
3. Moves missile out
4. Closes door
5. Fires missile
6. Moves missile launching rail back into bay

Unless the intention for the J-20 is to hang the missile outside during the entire engagement. The F-22 setup is faster.

Alternatively, perhaps the more complicated missile firing sequence is a tradeoff for preventing the sudden drag penalty for when the sidebay doors open to fire. Instead, the J-20 could expose its missile the moment combat enters WVR, and maneuver with the missile exposed so that a sudden slowdown doesn't occur mid maneuver at the moment of fire.

 

[Dragon029]

If the J-20 were equipped with non-LOAL missiles for a sortie, would a seeker have a sufficient cone of visibility for accomplishing target acquisition? If so, I imagine that could be a major benefit for operations using backwards compatibility of older AAM's.

 

[VH]

With J-20 you have to open the bay doors TWICE. Once to get the missile out of the bay exposing the missile rail, then you close the bay doors. Then you must open the bay again to retract the missile rail. F-22 opens the doors once, fires the missile and then closes the door. J-20 has a more complex sequence which translates into more chances for something to get jammed especially under high g-loads. As the old saying goes: KISS.


I'll bet that at some point the Chinese abandon their messy sequence and adopt a F-22 type firing arrangement.

 

[Deino]

Again... I think the engineers at CAC surely will know how that system works, what pros & cons it has and so on regardless Your assumption that is is too complex, takes too much time and will be replaced by a F-22-style system ... as such I leke these discussion simply for "playing" around with an idea but I we all are only free-time-analysts ... or did You propose a Raptor-style launching sequence at CA`C and were rejected ?

IMO the complexity is surely not a problem even under high-g loads and as such what counts is simply what time the whole circle needs from bay-opening to AAM-launch (even if You then have to open & close it again) and what You gain on RCS-reduction with a closed door.

 

[quellish]

IMO the complexity is surely not a problem even under high-g loads and as such what counts is simply what time the whole circle needs from bay-opening to AAM-launch (even if You then have to open & close it again) and what You gain on RCS-reduction with a closed door.

Maybe, but with that missile hanging out any gains from having the door closed may be lost.

Kind of odd that it landed with that hanging out. From what I am reading in the thread I can't tell - did it take off with the rail out?

 

[VH]

Again... I think the engineers at CAC surely will know how that system works, what pros & cons it has and so on regardless Your assumption that is is too complex, takes too much time and will be replaced by a F-22-style system ... as such I leke these discussion simply for "playing" around with an idea but I we all are only free-time-analysts ... or did You propose a Raptor-style launching sequence at CA`C and were rejected ?

Sorry but I would favor the experience and air-to-air know-how accumulated by Lockheed for decades over what CAC believes they know.

IMO the complexity is surely not a problem even under high-g loads and as such what counts is simply what time the whole circle needs from bay-opening to AAM-launch (even if You then have to open & close it again) and what You gain on RCS-reduction with a closed door.

Like you said its your opinion. Wonder what missile launching sequence the T-50 has chosen?

 

[sferrin]

Again... I think the engineers at CAC surely will know how that system works, what pros & cons it has and so on regardless Your assumption that is is too complex, takes too much time and will be replaced by a F-22-style system ... as such I leke these discussion simply for "playing" around with an idea but I we all are only free-time-analysts ... or did You propose a Raptor-style launching sequence at CA`C and were rejected ?

Sorry but I would favor the experience and air-to-air know-how accumulated by Lockheed for decades over what CAC believes they know.

Keeping in mind that LM has the accumulated experience from the F-102, F-106, F-111, and YF-12 when it comes to internal bays.

 

[chuck4]

Again... I think the engineers at CAC surely will know how that system works, what pros & cons it has and so on regardless Your assumption that is is too complex, takes too much time and will be replaced by a F-22-style system ... as such I leke these discussion simply for "playing" around with an idea but I we all are only free-time-analysts ... or did You propose a Raptor-style launching sequence at CA`C and were rejected ?

Sorry but I would favor the experience and air-to-air know-how accumulated by Lockheed for decades over what CAC believes they know.

Keeping in mind that LM has the accumulated experience from the F-102, F-106, F-111, and YF-12 when it comes to internal bays.

When LM has also accummulated experiences with having to launch out of an internal bay under the sweep of a canard, like they didn't with F-102, F-106, F-111, and YF-12, then we'll talk.

 

[sferrin]

Again... I think the engineers at CAC surely will know how that system works, what pros & cons it has and so on regardless Your assumption that is is too complex, takes too much time and will be replaced by a F-22-style system ... as such I leke these discussion simply for "playing" around with an idea but I we all are only free-time-analysts ... or did You propose a Raptor-style launching sequence at CA`C and were rejected ?

Sorry but I would favor the experience and air-to-air know-how accumulated by Lockheed for decades over what CAC believes they know.

Keeping in mind that LM has the accumulated experience from the F-102, F-106, F-111, and YF-12 when it comes to internal bays.

When LM has also accummulated experiences with having to launch out of an internal bay under the sweep of a canard, like they didn't with F-102, F-106, F-111, and YF-12, then we'll talk.

True. China has to make sure there is clearance for the canard. So most likely that is a less than ideal, compromised, solution.

 

[overscan (PaulMM)]

I have to step in here. Wild generalisations and assumptions are being thrown around. We can't conclude this is an amazing piece of Chinese ingenuity that Lockheed stupidly missed out on, any more than we can say its a stupid error by naive Chinese engineers who should have copied the F-22 design or a poor compromise forced on them by circumstances.

Firstly, what do we know? A J-20 prototype is fitted with an interesting sidebay weapons pylon arrangement which allows the pylon to stay outside while the weapons bay closes.

Why might you do this? Leaving aside the very real answers "because its a prototype - the finished article might be different" or "this is just for test rounds without LOAL" - lets assume for the sake of argument that this is the final design for the weapons sidebay.

Well, it might just be that the J-20 has a requirement to allow lock on before launch (LOBL) as well as lock on after launch (LOAL), just like the F-22 does. Aircraft design is the art of compromise, of reconciling different requirements which pull in different directions. There is no "one true way" which is demonstrably superior to all other approaches. F-22 and J-20 have different solutions to providing LOBL capabilities to the missile.

Why would this feature (LOBL) be important to China if the PL-10 AAM has lock on after launch ability?

1) Maybe pK is slightly higher with LOBL.
2) Maybe LOAL won't be available until Block 2 PL-10 and version 3 of the onboard J-20 software.
3) Maybe in a confused fight LOAL risks higher fratricide rates.
4) Maybe you are in a war and you just ran out of LOAL-capable PL-10s and need to use the stocks of PL-8/9 hanging around your airbase.
5) Maybe you want to be able to sell the J-20 to third parties but PL-10 is too secret to be exported with it so it needs to be able to fire PL-9.
6) Maybe leaving the AAM outside for the duration of WVR combat speeds up LOBL launch (no need to wait for the bay to open to lock on) and increases your chances of hitting fleeting targets of opportunity.
7) Maybe PL-10s are just damn expensive and you'd like to be able to use the cheaper PL-9 series as well.

The F-22 was designed to be able to fire AIM-9L/M. AIM-9X wasn't even an option initially. The F-22 uses an arrangement where, for LOBL, the weapons bay doors open and remain open. The launcher swings out so that the seeker of the AAM can locate the target. It locates the target, locks on, fires, then the launcher retracts and the bay doors close.

The J-20 arrangement seen on this prototype allows the weapons bay door to close, leaving the launcher outside and below the sidebay. The missile can then locate its target, lock on, fire, then the weapons bay doors open again to allow the launcher to retract.

Why might you do want the doors to close rather than stay open like on the F-22?

The J-20 has a canard in the near vicinity of the sidebay. It may be that having an open weapons bay door for an extended period restricts movement of the canard or causes nasty aerodynamic interactions between the two. This would make it advantageous to close the door as soon as possible.

Perhaps the area of the sidebay has undesirable airflow characteristics. This launcher puts the missile lower down on the fuselage side in a more benign environment.


Perhaps the requirement for quick launch were so severe they couldn't wait for bay doors to open so the only option was to make a launcher than can stay outside the whole WVR engagement allowing near-instant launch.

The appearance of this launcher on a prototype J-20 also does not preclude the ability to use lock on after launch missiles. For a start, there could be a second pylon arragement which ejects the missile directly without the drop-out rail. Even using the existing rail, without seeing the cycle in action its not possible to know if it is slower, or if it is slower, is that tactically significant when weighed against the benefits?

This topic is for analysis and speculation, but lets have informed speculation please.

 

[Mach42]

I would think the pros are that it gives better clearance and on the purely speculative side the CAC design might be inherently more resistant to G-forces and thus can be more lightweight.

 

[chuck4]

True. China has to make sure there is clearance for the canard. So most likely that is a less than ideal, compromised, solution.

Any practical engineering solution must be a compromise. The question is did the design compromise what is more important for what is less important. Judging from the fact that CAC picked canard layout more than once, we may assume CAC designers thought giving the plane a canard layout was more important than giving it a F-22 like launch rail. So the compromises of this launch rail design may well have been deemed to resulted in less compromised aircraft overall, at least in the estimation of CAC designer


.

 

[chuck4]

I would think the pros are that it gives better clearance and on the purely speculative side the CAC design might be inherently more resistant to G-forces and thus can be more lightweight.

Pure speculation. Nothing suggests the J-20 rail arrangement is intrinsically structurally lighter or more rigid, and hence more resistent to G-forces.

I think the J-20 launcher arrangement is governed largely by the different launch parameters specified in its design specifications.

 

[VH]

Sorry, but I would favour both Lockheed's and CAC's experience over that of an anonymous internet poster with an accumulative total of six posts on this forum, all in threads about China and all seemingly derogatory towards its intellectual and engineering capabilities. Especially considering that you seem not to understand that the trapeze mechanism used by the F-22 to launch it's missiles essentially achieves the same thing as the J-20's fold out launch rail.

Remember the discussion is on how effective this missile launch scheme is in maintaining the stealth of this aircraft in an air combat situation. Can you address that issue? As others have pointed out having this missile hanging out of the aircraft increases the radar cross section of the aircraft. This configuration with this missile is very much like hanging a missile from a pylon on a wing.

 

[latenlazy]

True. China has to make sure there is clearance for the canard. So most likely that is a less than ideal, compromised, solution.

Any practical engineering solution must be a compromise. The question is did the design compromise what is more important for what is less important. Judging from the fact that CAC picked canard layout more than once, we may assume CAC designers thought giving the plane a canard layout was more important than giving it a F-22 like launch rail. So the compromises of this launch rail design may well have been deemed to resulted in less compromised aircraft overall, at least in the estimation of CAC designer


.

I'm splitting hairs a bit here, but for the solution to be a compromise one would have to assume some loss in functionality, or some form of inferiority. I haven't yet seen any compelling reason to assume those things. Couldn't it just be an equally functional/effective, or even a better approach?

Sorry, but I would favour both Lockheed's and CAC's experience over that of an anonymous internet poster with an accumulative total of six posts on this forum, all in threads about China and all seemingly derogatory towards its intellectual and engineering capabilities. Especially considering that you seem not to understand that the trapeze mechanism used by the F-22 to launch it's missiles essentially achieves the same thing as the J-20's fold out launch rail.

Remember the discussion is on how effective this missile launch scheme is in maintaining the stealth of this aircraft in an air combat situation. Can you address that issue? As others have pointed out having this missile hanging out of the aircraft increases the radar cross section of the aircraft. This configuration with this missile is very much like hanging a missile from a pylon on a wing.

Stealth isn't as important in wvr combat.

 

[Blitzo]

Stealth isn't as important in wvr combat.

Not to mention a missile hanging out on a pylon would be more stealthy than a missile hanging out on a pylon with both bay doors open the entire time too ala F-22...

 

[VH]

Not to mention a missile hanging out on a pylon would be more stealthy than a missile hanging out on a pylon with both bay doors open the entire time too ala F-22...

FYI The time F22 consumes to open its side bay and fires its Sidewinder is measured in seconds. Check out any video of F22 firing its Aim-9 and see for yourself

 

[VH]

Just like when the F-22, F-35 and F-15 Silent Eagle weapons bays/launchers push their missiles outside the bay and through the boundary layer prior to missile launch. And you were not talking about radar cross section, you were talking about complexity, it has been pointed out to you that the system chosen by the Chinese is no more complex than that on the F-22.

How did you arrive at that conclusion? And I am speaking about loss of radar cross section and complexity.

 

[Blitzo]

Not to mention a missile hanging out on a pylon would be more stealthy than a missile hanging out on a pylon with both bay doors open the entire time too ala F-22...

FYI The time F22 consumes to open its side bay and fires its Sidewinder is measured in seconds. Check out any video of F22 firing its Aim-9 and see for yourself

See, so the point of your argument wasn't about stealth per se as much as time.
Of course, we don't know how quickly J-20 can fire PL-10 in a test environment as of yet, so your argument is moot.


Practically, for those of us bent on comparison,


1: How quickly would an F-22 would fire its sidewinder in a combat scenario?
2 (and more importantly): How quickly would J-20 fire its PL-10 in a comparable scenario, assuming both are firing LOBL or LOAL missiles.


If one day we get an answer for 2, and it turns out both J-20 and F-22 have SRAAM firing sequences of similar duration, then technically J-20 will be exposing less drag and less surfaces for reflection than F-22.

 

[chuck4]

True. China has to make sure there is clearance for the canard. So most likely that is a less than ideal, compromised, solution.

Any practical engineering solution must be a compromise. The question is did the design compromise what is more important for what is less important. Judging from the fact that CAC picked canard layout more than once, we may assume CAC designers thought giving the plane a canard layout was more important than giving it a F-22 like launch rail. So the compromises of this launch rail design may well have been deemed to resulted in less compromised aircraft overall, at least in the estimation of CAC designer


.

I'm splitting hairs a bit here, but for the solution to be a compromise one would have to assume some loss in functionality, or some form of inferiority. I haven't yet seen any compelling reason to assume those things. Couldn't it just be an equally functional/effective, or even a better approach?

The photo and CG rendering of j-20 mechanism suggests the launch rails are mounted rigidly to curved arms , which either pivot or travel on rollers during deployment to facilitate more complicated out and down motion. F-22's launch rails are hinged to trapeze arms, which deploy when retracted collapse under the rails. This suggests the f-22's lunch rails stow into a smaller package when retracted.

 

[chuck4]

Not to mention a missile hanging out on a pylon would be more stealthy than a missile hanging out on a pylon with both bay doors open the entire time too ala F-22...

FYI The time F22 consumes to open its side bay and fires its Sidewinder is measured in seconds. Check out any video of F22 firing its Aim-9 and see for yourself

See, so the point of your argument wasn't about stealth per se as much as time.
Of course, we don't know how quickly J-20 can fire PL-10 in a test environment as of yet, so your argument is moot.


Practically, for those of us bent on comparison,


1: How quickly would an F-22 would fire its sidewinder in a combat scenario?
2 (and more importantly): How quickly would J-20 fire its PL-10 in a comparable scenario, assuming both are firing LOBL or LOAL missiles.


If one day we get an answer for 2, and it turns out both J-20 and F-22 have SRAAM firing sequences of similar duration, then technically J-20 will be exposing less drag and less surfaces for reflection than F-22.

2 observationss and 1 reflection:


Due to the location of the rail, the seeker of an IR missile on the rail of a J-20 should have a substantially larger uninterrupted field of view than a seeker of an IR missile on the rail of an F-22.


J-20's design affords the option of stowing the IR missile for maximum stealth during BVR combat, and also deploying the IR missile outside in an aerodynamically relatively clean configuration during WVR combat, when stealth can't be achieved anyway. While so deployed othe IR missile can be fired even quicker than the missile on the f-22. F-22's design does not afford similar options. the missile is either stowed stealthily even when stealth can't be achieved, or deployed in an aerodynamically messy configuration.


Now the reflection. LOAL is nice. But I am not sure it is always desirable to fire a missile in the LOAL mode even if the missile is capable of LOAL mode. For instance, in a very close range maneuvering fight, the distance the missile fired in LOAL mode may have to travel before it acquires a lock may put the target out of the field of view of the seeker. Having the ability to carry the missile outside in relatively clean aerodynamic configuration to facilitate lock on before launch when situation demands it may be an advantage.

 

[latenlazy]

True. China has to make sure there is clearance for the canard. So most likely that is a less than ideal, compromised, solution.

Any practical engineering solution must be a compromise. The question is did the design compromise what is more important for what is less important. Judging from the fact that CAC picked canard layout more than once, we may assume CAC designers thought giving the plane a canard layout was more important than giving it a F-22 like launch rail. So the compromises of this launch rail design may well have been deemed to resulted in less compromised aircraft overall, at least in the estimation of CAC designer


.

I'm splitting hairs a bit here, but for the solution to be a compromise one would have to assume some loss in functionality, or some form of inferiority. I haven't yet seen any compelling reason to assume those things. Couldn't it just be an equally functional/effective, or even a better approach?

The photo and CG rendering of j-20 mechanism suggests the launch rails are mounted rigidly to curved arms , which either pivot or travel on rollers during deployment to facilitate more complicated out and down motion. F-22's launch rails are hinged to trapeze arms, which deploy when retracted collapse under the rails. This suggests the f-22's lunch rails stow into a smaller package when retracted.

Sure, but isn't the real gauge of how effective the solution is dependent on its performance as a weapons mount? What I'm getting at is whether the specific mechanism compromises deployment time, aerodynamic penalty, detectability, kill probability, etc etc. Even if the mechanism takes up more space, that's secondary to the actual performance of the solution.

 

[Trident]

- snipped for brevity -

Good post! I would like to add only one point which affects most SRAAMs but is independent of LOAL/LOBL capability: such missiles are generally rail launched (rather than free-fall or ejector). I would expect the PL-10 to be no different, if nothing else to ensure backwards compatibility with legacy fleets (J-10, J-11).
All in all, I see the following other reasons as possible explanations for the novel weapons bay solution:
1. Interference between the door and canard if opened far enough to clear the missile. This could be either mechanical (if so, most likely for upward deflection, there are photos showing the bay door at least partially open during full downward canard deflection on the ground) or aerodynamic in nature.
2. Severe vibration induced by air flow over the open bay cavity which cannot be tolerated by the missile for long periods. As pointed out by you, it could be advantageous to extend the missiles as soon as the J-20 enters a short-range engagement and keep them ready to fire with minimum delay throughout the fight.
As for disadvantages, I don't really see any. Probably the biggest penalty will have been the research effort to come up with this solution and then the development cost to validate it over a more conventional approach due to the increased risk inherent in adopting any untried solution.

 

[chuck4]

2 thoughts:


1. It seems to me that severe aerodynamic vibration inside the open weapon bay may be more easily cured by some kind of simple movable spoiler or deflector that deploys with the bay doors, rather than a elaborate and novel rail deployment mechanism.


2. It's not the rail launch that brings up the issue of LOAL/LOBL. It's the fact that the ability to close the weapon bay doors with the rail outside suggest the design specifically intends to hold the missile in the airstream for a significant amount of time. If the design simply calls for the quickest possible launch of the missile, there is no need to close the doors in the middle of the sequence.

 

[VH]

2 thoughts:


1. It seems to me that severe aerodynamic vibration inside the open weapon bay may be more easily cured by some kind of simple movable spoiler or deflector that deploys with the bay doors, rather than a elaborate and novel rail deployment mechanism.

F-117 and B2 both deploy a simple airdam into the slipstream when the bomb bay doors are open for that purpose

2. It's not the rail launch that brings up the issue of LOAL/LOBL. It's the fact that the ability to close the weapon bay doors with the rail outside suggest the design specifically intends to hold the missile in the airstream for a significant amount of time. If the design simply calls for the quickest possible launch of the missile, there is no need to close the doors in the middle of the sequence.

Exactly. And the mystery remains as to why the J-20 was seen landing with their novel missile rail system still deployed. Did it jam up and fail to retract during a test?

 

[latenlazy]

2 thoughts:


1. It seems to me that severe aerodynamic vibration inside the open weapon bay may be more easily cured by some kind of simple movable spoiler or deflector that deploys with the bay doors, rather than a elaborate and novel rail deployment mechanism.


2. It's not the rail launch that brings up the issue of LOAL/LOBL. It's the fact that the ability to close the weapon bay doors with the rail outside suggest the design specifically intends to hold the missile in the airstream for a significant amount of time. If the design simply calls for the quickest possible launch of the missile, there is no need to close the doors in the middle of the sequence.

And again, the intention to leave the missile in the airstream for a prolonged period, or at least the capability to do so, by itself is not necessarily indicative of issues with LOAL, especially if there are inherent advantages to adopting the particular mechanism, such as better launch of non LOAL missiles.

Exactly. And the mystery remains as to why the J-20 was seen landing with their novel missile rail system still deployed. Did it jam up and fail to retract during a test?

Unlikely? They would need to test the aerodynamic effects of the extended rail in all flight envelopes, including landing, with or without the intention to leave it exposed over a prolonged period of time.

 

[VH]

Using the F-22 and the F-23 as a yardstick I never saw a instance of those aircraft landing with side or bottom bays still open. But maybe J-20 rolls different?

 

[overscan (PaulMM)]

Note that the F-22 won't have LOAL capability until 2015 at the earliest, which is 10 YEARS after IOC.

 

[sferrin]

Using the F-22 and the F-23 as a yardstick I never saw a instance of those aircraft landing with side or bottom bays still open. But maybe J-20 rolls different?

F-22 has landed with a side bay open. There was a picture of it in one of Airtime Publishing's books.

 

[latenlazy]

Using the F-22 and the F-23 as a yardstick I never saw a instance of those aircraft landing with side or bottom bays still open. But maybe J-20 rolls different?

That's a bit beside the point. They would have to conduct tests like these in case of mechanical failure. The yf-23 probably never had to conduct those tests because the program was never picked up. I'm more than certain the F-22 would have had to land with its bays open as it was testing for certification.

 

[chuck4]

Also keep in mind that whether the cheek missile arrangement on the j-20 innovative and effective, or overly clever and ill considered, this arrangement in and of itself seem unlikely to have a great deal of impact on the overall effectiveness of the j-20, which remains essentially unknown.

 

[Sundog]

Perhaps one of the reasons to have the launch rail exposed with the doors closed is to be able to carry missiles/munitions on that station that would not fit within the weapons bay? For missions when LO isn't required, just as the F-35 has the ability to carry external stores during such missions.