Engineers are laz...errr efficient. If there's something that they don't need to test on a prototype that would require extra work and that thing doesn't impact everything else, they'll gladly skip that step and do without it. From a resource and time perspective this makes sense. If you're a creme de la creme project, time is more important than veneer.
J-20 5th Gen Fighter Thread V
- Thread starter Deino
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I love your brain-storming and enthusiasm gentlemen, and I can assure you that NO, Chengdu did not get lazy, they have NO control on when the WS-15 prototypes will be airworthy enough to certify to production, so they are trying to "read the tea leaves" and anticipate on a real world basis.
It remains rather apparent that the AL-31s are with us for the immediate future, possibly longer, before we get into a panic, I would remind you that Wilbur and Orville, "flew" their gliders for some time before graduating to the "Wright Flyer" in 1903??
so while the knowledge and engineering of the WS-15 may be complete?? (lets suppose they are complete), just for fun?, the processes for building and operating this very complex aircraft engine, are equally complex, as are the material characteristics required to give it a usable life-span. I will say this once,
no I'm gonna say it twice?? LOL "complexities do not lend themselves well to time constraints", when you begin to try to bring two new pieces of highly complex equipment together, it is almost ignorant to tie them up with a "schedule", the J-20 and WS-15 will be brought together when they are ready, not a moment before?
By my eyes, it looks like 2016 is the only one with "recessed" nacelles. The others just look shorter because of the angle. Gotta look at the relationship of length between the two sections.
plawolf
Lieutenant General
I think the first pair of pictures show it best, engine nacelle has been extended slightly, and widened if both are using the same engines.
You can see by referencing both the relative positioning of the engine nacelle compared to the root of the vertical stabilizer and the ventricle fins, since the two shots are of very similar angles.
You can tell that the nacelles are slightly wider, especially at the end, as the fairly pronounce tapering off has disappeared, and the whole nacelle has a far more smooth overall outline. Which, would incidentally, help explain the noticeable gap between the engines and the nacelles on 2016 compared to the far more flush finish of earlier prototypes.
Quickie
Colonel
Yes I remember the pictures. I was arguing, and still stand by it, that the apparent different in size of the 2 engine nacelles was not due the angle of view of the picture but an actual physical difference. If you look at the size of the pair of wheels and flaps of the prototype, there is no noticeable size distortion in the picture that would explain the apparent different in size of the nacelles.
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After drawing some lines to help visualize the perspective, it shows a couple things. First is that you're correct that it's not the perspective that causing one engine to look larger. But also second that there's no difference between the two engines aside from the petals. The housing around them (the serrated part where the fuselage ends) is the same, the angles are correct, etc.
From this, it looks like it's just an optical illusion caused by the right engine having its petals opened completely, while the left side has them contracted.
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Quickie
Colonel
After drawing some lines to help visualize the perspective, it shows a couple things. First is that you're correct that it's not the perspective that causing one engine to look larger. But also second that there's no difference between the two engines aside from the petals. The housing around them (the serrated part where the fuselage ends) is the same, the angles are correct, etc.
From this, it looks like it's just an optical illusion caused by the right engine having its petals opened completely, while the left side has them contracted.
There's more work to do actually.
Looking at the 2nd line from the top, the length from the left side of the left flap to the centre of the left nazelle is actually longer than the length from the right side of the right flap to the centre of the right nacelle.
So there's already a perspective distortion that makes dimensions on the left side of the aircraft seem slightly longer than the right.
One way to measure the nacelle diameter is to draw a imaginary zig-zag line across the top of the 2 nacelle serrated edges and then try to straighten the 2 lines (Is there a software that can do this?) and compare their lengths.
(Also bear in mind the perspective distortion that would make the left nacelle length appearing longer, although this may be quite small because of the close distance of the 2 nacelles.)
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