Another set of measurements. Assuming 20.8 meter length for J-20, tip of nose to end of fairings to the side of the engines.
Bay length 4.4 meters (Possibly 4.45 but likely not more)
Bay width (individual bay) 1.07 meters (there are a few structural spars that at a few places make the width more narrow, by a few cm)
PL-15 missile dimensions
length 3.94 meters
diameter 0.202 meters
mid-body wing span ~ 0.430 (give or take 2 cm)
rear fin span ~0.562 (give or take 2 cm)
For comparison, here are the official SD-10A dimensions (verified to be the same for PL-12 by using photo measurements)
Length: 3934 mm
Diameter: 203 mm
Wing span: 670 mm
Fin span: 752 mm
Weight: 199 kg
When rotated by 90 degrees, to get the narrowest width of the fin box.
one gets roughly 40 cm for rear fins and 32 cm for mid body wings.
When one staggers the missiles, overall length of two such staggered missile package is 4.31 m.
Without ANY clearance calculated, overall width for a pacage of 3 missiles, with middle missile staggered, would be basically 1.06 - 1.12 m
Of course, several cm of clearance is needed, at four points. Between missiles and outer walls of the bay, and two more points between each of the side missiles and the middile missiles.
Basically, even if the length /depth of the edges of the bay allowed for staggering, the width of the missiles (rear fins to be more exact) doesn't allow it. if each fin was 1-2 cm shorter, one just might have been able to cram it all in.
Fun fact: pl-12/15/sd10 are the largest of the medium range modern actively guided missiles.
Japanese AAM4 and Russian r77-1 have similar diameters, but are both shorter, at 3.66 and 3.8 m respectively.
Basically, when PLAAF decides to get a missile that is slightly narrower or has slightly shorter fins... packing 3 of such missiles will be possible per bay. And such missile would still be larger than amraam, which is a 1.78 m diameter and 3.66 long missile with 4.78 m finspan and wingspan (both being the same)
End conclusion is - plaaf could have went for a slightly smaller missile. and perhaps suffered just a few percent worse performance, as the overall change in size would have been almost negligable. that could have allowed them to have 50% more bvr missiles per j-20. But they chose not to do it.
Reasons? Stick with pl-12 body form? That could have saved them some money, logistically, as pretty much all support eco system is already in place.
doctrine? Their theory of air combat versus opponent such as US might have led them to believe that number of occasions where more than 4 BVR aams are needed is insignificantly small. If so, that would be in opposition to US, which concluded 4 missiles aren't enough for raptor. But at the same time they're in no hurry to fit more into F-35. As for russians, no official info is out there. the case for 4 inside su-57 is as strong as the case for 6.
Folding fins is in my opinion extremely unlikely. We wont see such a missile soon. There is no example of such high-speed medium range missile with folding conventional fins, anywhere in the world. Some surface to air missiles do have folding fins, but i wouldn't say that's the same class of a weapon. Russian r-77 can fold its rear control surfaces, but those are not fins. We would have seen by now some BVR range missiles with folding fin solutions if that was something that was worth making. Evidently everyone in the world concluded the tech is not there even to try making a demonstrator. Likely structural weight penalties are probably not worth it. I'd think there are higher chances of China fielding a whole new, slightly narrower missile (still bigger than amraam) than fielding a folding fin variant.
bonus measurement: pl-10 seems 3.01 m long, overall max finspan 0.54 m
While I may be off on baseline 20.8 m length for J-20, all the ratios would remain the same, bay size to missile size etc. Plus the pl-15 missile measurements fit very nicely to known published sd-10 body dimensions.
Bay length 4.4 meters (Possibly 4.45 but likely not more)
Bay width (individual bay) 1.07 meters (there are a few structural spars that at a few places make the width more narrow, by a few cm)
PL-15 missile dimensions
length 3.94 meters
diameter 0.202 meters
mid-body wing span ~ 0.430 (give or take 2 cm)
rear fin span ~0.562 (give or take 2 cm)
For comparison, here are the official SD-10A dimensions (verified to be the same for PL-12 by using photo measurements)
Length: 3934 mm
Diameter: 203 mm
Wing span: 670 mm
Fin span: 752 mm
Weight: 199 kg
When rotated by 90 degrees, to get the narrowest width of the fin box.
one gets roughly 40 cm for rear fins and 32 cm for mid body wings.
When one staggers the missiles, overall length of two such staggered missile package is 4.31 m.
Without ANY clearance calculated, overall width for a pacage of 3 missiles, with middle missile staggered, would be basically 1.06 - 1.12 m
Of course, several cm of clearance is needed, at four points. Between missiles and outer walls of the bay, and two more points between each of the side missiles and the middile missiles.
Basically, even if the length /depth of the edges of the bay allowed for staggering, the width of the missiles (rear fins to be more exact) doesn't allow it. if each fin was 1-2 cm shorter, one just might have been able to cram it all in.
Fun fact: pl-12/15/sd10 are the largest of the medium range modern actively guided missiles.
Japanese AAM4 and Russian r77-1 have similar diameters, but are both shorter, at 3.66 and 3.8 m respectively.
Basically, when PLAAF decides to get a missile that is slightly narrower or has slightly shorter fins... packing 3 of such missiles will be possible per bay. And such missile would still be larger than amraam, which is a 1.78 m diameter and 3.66 long missile with 4.78 m finspan and wingspan (both being the same)
End conclusion is - plaaf could have went for a slightly smaller missile. and perhaps suffered just a few percent worse performance, as the overall change in size would have been almost negligable. that could have allowed them to have 50% more bvr missiles per j-20. But they chose not to do it.
Reasons? Stick with pl-12 body form? That could have saved them some money, logistically, as pretty much all support eco system is already in place.
doctrine? Their theory of air combat versus opponent such as US might have led them to believe that number of occasions where more than 4 BVR aams are needed is insignificantly small. If so, that would be in opposition to US, which concluded 4 missiles aren't enough for raptor. But at the same time they're in no hurry to fit more into F-35. As for russians, no official info is out there. the case for 4 inside su-57 is as strong as the case for 6.
Folding fins is in my opinion extremely unlikely. We wont see such a missile soon. There is no example of such high-speed medium range missile with folding conventional fins, anywhere in the world. Some surface to air missiles do have folding fins, but i wouldn't say that's the same class of a weapon. Russian r-77 can fold its rear control surfaces, but those are not fins. We would have seen by now some BVR range missiles with folding fin solutions if that was something that was worth making. Evidently everyone in the world concluded the tech is not there even to try making a demonstrator. Likely structural weight penalties are probably not worth it. I'd think there are higher chances of China fielding a whole new, slightly narrower missile (still bigger than amraam) than fielding a folding fin variant.
bonus measurement: pl-10 seems 3.01 m long, overall max finspan 0.54 m
While I may be off on baseline 20.8 m length for J-20, all the ratios would remain the same, bay size to missile size etc. Plus the pl-15 missile measurements fit very nicely to known published sd-10 body dimensions.
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