J-20 versus F-35

[madrat]

What a stork sense of reality.
You came up with that theory on a lark.

[weasel1962]

For anyone who wants to have an estimate of China's air power today.

http://www.airuniversity.af.mil/Portals ... %20web.pdf

This should be read as a high estimate which roughly translate into

33 J-20s
631 Flanker variants (J-11, J-16, Su-27/30/35)
589 J-10s (includes 84 SY trainers)
302 J-8s (includes 80 recon)
535 J-7s (excl trainers but mostly in reserve)
219 JH-7s
270 H-6 (includes 24 tanker and 55 combat capable trainers)

Q5s should not be included as these have been retired after the publication. Roughly 1,253 3G, 302 2G BVR, 535 2G fighters, 489 bombers totally ~2,500 combat aircraft

[gta4]

And do you still believe J-20 has an empty weight of only 15 ton?

[weasel1962]

And do you still believe J-20 has an empty weight of only 15 ton?

Actually, I don't. However I posted the links to demonstrate that there are people who have done calculations who dont necessarily confirm assumptions about j-20 weights. Personally, I dont have enough info to confirm the actual weight. I do read a lot of assumptions like how the F-35 can fly 3000 nm unrefuelled.

To date, what is factual is there isnt an authoritative calculation of what the actual empty weight of the j-20 is.

I woud however standby what I said about "60k lb thrust at roughly F-15 weights". No one has yet suggested J-20 exceeds F-15 take off weight of 81k lbs,

[gta4]

So you are equivalent to say "J-20 carries less fuel and payload than F-15 at take-off"

[weasel1962]

So you are equivalent to say "J-20 carries less fuel and payload than F-15 at take-off"

Just highlighting that the 60lb engine thrust at approx F-15 take off weight should not differ too far from F-15 flight performance. More of a general statement. Don't recall any concrete data on fuel carried or payload being mentioned. Didn't want to belabor the point that the F-15 has an empty weight of 20k tons.

viewtopic.php?f=55&t=6094&start=1695

The post was really in response to a comment that the J-20 is sluggish, still not sure how that comment can be supported.

btw, that reminds me. Still waiting for that research paper...

[gta4]

So you are equivalent to say "J-20 carries less fuel and payload than F-15 at take-off"

Just highlighting that the 60lb engine thrust at approx F-15 take off weight should not differ too far from F-15 flight performance. More of a general statement. Don't recall any concrete data on fuel carried or payload being mentioned. Didn't want to belabor the point that the F-15 has an empty weight of 20k tons.

viewtopic.php?f=55&t=6094&start=1695

20tons = 44000lbs. Are you sure?

Guess what? Even F-15E with GE129 has an empty weight of 33800 lbs:
https://arc.aiaa.org/doi/abs/10.2514/6.1990-1266

F15EGE129weight.jpg (65.36 KiB) Viewed 25027 times

[gta4]

So you are equivalent to say "J-20 carries less fuel and payload than F-15 at take-off"

Just highlighting that the 60lb engine thrust at approx F-15 take off weight should not differ too far from F-15 flight performance. More of a general statement. Don't recall any concrete data on fuel carried or payload being mentioned. Didn't want to belabor the point that the F-15 has an empty weight of 20k tons.

viewtopic.php?f=55&t=6094&start=1695

The post was really in response to a comment that the J-20 is sluggish, still not sure how that comment can be supported.

btw, that reminds me. Still waiting for that research paper...

I also have to remind you that, the same guy has done another estimation on F-35, and according to him, F-35 has far better aerodynamic performance than J-20, and is 10000lbs lighter than J-20:

http://www.dept.aoe.vt.edu/~mason/Mason ... ownS03.pdf (their estimation of F-35)
http://www.dept.aoe.vt.edu/~mason/Mason_f/J20Spr11.pdf (their estimation of J-20. You cited this.)

[weasel1962]

Righto. I got sidetracked by Boeing's 45000lb class on its tech specs. Checking back its 33.5k lbs empty w.o CFT and 37.5k lbs w CFT = agreed.

Nevertheless, nothing posted has changed the basic argument. The J-20 is fitted with twin AL31FM2 engines, each with 31.5k lb thrust or 63k lbs.

https://www.rt.com/news/364947-china-fi ... t-airshow/

If assuming an F-15C with twin 220 driving 47,540 lb thrust on a 33,500 lb empty weight derives a thrust weight ratio of 1.42. A J-20 with 63k lbs thrust on 44000 lb empty weight derives a thrust weight of 1.43. No one ever claimed an F-15C was sluggish.

Agree F-35 is an awesome plane. The F-35 may be better than a J-20 but it is not objective to ignore the J-20 has many features that enable it to similarly beat the F-15. Firstly, it has less drag with no external tanks. It has greater thrust in its engines. And like the F-15C, its A2A internal only so far. 6-8 missiles is not a heavy weapons load. So really, its a function of how much fuel it carries, even if the 44,000lb empty weight is validated, which it is not. If its lighter...

P.s. The F-35A has a 1.48 thrust-empty weight ratio but the F-35B has less. Doesn't mean anything right because the B carries less fuel to compensate for the diff.

[sprstdlyscottsmn]

20tons = 44000lbs. Are you sure?

Before you make that leap, check to see if they are using Metric or US tons in their statements. Being in the US myself, I always default "ton" to 2,000lb. If I mean to specify 1,000kg I will say Metric Ton or Tonne. An F-15E is close to 40,000lb empty with the CFTs, and an F-22 is close to 44,000lb empty. It is not unreasonable to assume a 20-ton or 20-tonne weight class for a large LO aircraft with internal weapons bays.

[wrightwing]

20tons = 44000lbs. Are you sure?

Before you make that leap, check to see if they are using Metric or US tons in their statements. Being in the US myself, I always default "ton" to 2,000lb. If I mean to specify 1,000kg I will say Metric Ton or Tonne. An F-15E is close to 40,000lb empty with the CFTs, and an F-22 is close to 44,000lb empty. It is not unreasonable to assume a 20-ton or 20-tonne weight class for a large LO aircraft with internal weapons bays.

The J-20 appears to be larger than the F-22 by pretty good amount. I would be very surprised if it had an empty weight less than 44,000lbs.

[gta4]

Righto. I got sidetracked by Boeing's 45000lb class on its tech specs. Checking back its 33.5k lbs empty w.o CFT and 37.5k lbs w CFT = agreed.

Nevertheless, nothing posted has changed the basic argument. The J-20 is fitted with twin AL31FM2 engines, each with 31.5k lb thrust or 63k lbs.

https://www.rt.com/news/364947-china-fi ... t-airshow/

If assuming an F-15C with twin 220 driving 47,540 lb thrust on a 33,500 lb empty weight derives a thrust weight ratio of 1.42. A J-20 with 63k lbs thrust on 44000 lb empty weight derives a thrust weight of 1.43. No one ever claimed an F-15C was sluggish.

Agree F-35 is an awesome plane. The F-35 may be better than a J-20 but it is not objective to ignore the J-20 has many features that enable it to similarly beat the F-15. Firstly, it has less drag with no external tanks. It has greater thrust in its engines. And like the F-15C, its A2A internal only so far. 6-8 missiles is not a heavy weapons load. So really, its a function of how much fuel it carries, even if the 44,000lb empty weight is validated, which it is not. If its lighter...

P.s. The F-35A has a 1.48 thrust-empty weight ratio but the F-35B has less. Doesn't mean anything right because the B carries less fuel to compensate for the diff.

Again, you are terribly wrong.
F15C weights only 28400 lbs empty. You can't tell 15C from 15E.

[fbw]

Again, you are terribly wrong.
F15C weights only 28400 lbs empty. You can't tell 15C from 15E.

The F-15C has not had an empty weight below 30,000lbs in a long time. The OEW is nearly 32,000lbs.

[weasel1962]

20tons = 44000lbs. Are you sure?

Before you make that leap, check to see if they are using Metric or US tons in their statements. Being in the US myself, I always default "ton" to 2,000lb. If I mean to specify 1,000kg I will say Metric Ton or Tonne. An F-15E is close to 40,000lb empty with the CFTs, and an F-22 is close to 44,000lb empty. It is not unreasonable to assume a 20-ton or 20-tonne weight class for a large LO aircraft with internal weapons bays.

The J-20 appears to be larger than the F-22 by pretty good amount. I would be very surprised if it had an empty weight less than 44,000lbs.

It is longer but shorter wingspan and lower height with roughly equivalent wing area. Also a question of building materials.

http://www.china-arms.com/2016/01/china ... se-report/

Most sources appear to quote 19.4tons, which is ~300kg lighter than f-22. At that empty weight, its 1.48 thrust-empty weight ratio.

[gta4]

Again, you are terribly wrong.
F15C weights only 28400 lbs empty. You can't tell 15C from 15E.

The F-15C has not had an empty weight below 30,000lbs in a long time. The OEW is nearly 32,000lbs.

28400 lbs is what I get from F-15C MSIP manual