Part 2 of 4
This is a discussion on J-20... The New Generation Fighter III within the Air Force forums, part of the China Defense & Military category; Well Brat, aerobatics aircraft have different requirements I'd say. Most notably, they're far slower and have less requirement for stealth, ...
Well Brat, aerobatics aircraft have different requirements I'd say. Most notably, they're far slower and have less requirement for stealth, so the aerodynamic requirements can be fullfilled almost without compromise. Plus, on aircraft with a single vert stab, it's rather strange to have that canted
For all I know the vert stabs on the F-22 are actually smaller in area than they were on the prototype (and I think you can see that looking at pictures form a similar angle), though they are further back.
If you're trying to yaw in high AoA / slow speed an all moving vert stab may be more usefull to enforce that movement, as in a conventional stab you still have that fixed controll surface part wich I imagine wants the plane to weatherwane back into the wind somewhat. I can't really say if it's better for yaw stability in other flight regimes, though.
Then again, the J-20 also has those vert fins extending down below the vert stabs, providing additional controll. So in the end, the total area might no be that much smaller than that of the Raptor's vert stab.
The YF-22 was the more agile plane I think, while the YF-23 was apparently more stealthy & faster, but also considered to be more high risk, wich is I think were the believe of "having settled for the F-22" comes from.
Last edited by Scratch; 01-16-2012 at 12:33 AM.
Part 2 of 4
Last edited by FarkTypeSoldier; 01-16-2012 at 12:34 AM.
Part 3 of 4
Last edited by FarkTypeSoldier; 01-16-2012 at 12:36 AM.
Part 4 of 4
Last edited by FarkTypeSoldier; 01-16-2012 at 12:37 AM.
Sorry for mulitple posts... I do not know why the links were all broken, but is fixed now. All images were uploaded by imageshack.us.
Last edited by FarkTypeSoldier; 01-16-2012 at 12:41 AM.
I hadn't seen those fark they are great, I like the one with the landing configuration, that kind of illustrates, where the canards should be, what was confusing me that mig29 helped clear up, where the canards angled down at high AOAs, that study he posted pointed out that they are angled down at high aoas to prevent over pitching and loss of directional control. Happy new year! Brat
Honestly, I don't really know about any details there, either. Back then, when the YF-23 was supposedly relying on B-2 tech (already super expensive) for it's performance and all that, it was exspected that these (slightly) superior characteristics would have to be bought with a lot of extra money.
YF-23 : Slightly superior in RCS reduction, Superior IR reduction, Faster in with & without afterburner (some rumors put as much higher speed potential over the YF-22), Excellent supersonic maneuverability.
YF-22 : Greater low speed handling, Excellent supersonic maneuverability, Cheaper to make, USAF confidence in timely & on budget delivery, Commonality with NATF further reducing cost (ironically NATF got cancelled )
YF-23 was considered to be complex, and it seem USAF was not sure about the teams ability to deliver. Essentially risky because it was considered more complex.
Last edited by Hyperwarp; 01-16-2012 at 04:14 PM.
I'd like to go back to something briefly mentioned before, but wich's potential effects have bothered me to some extent.
That is the J-20s rather blueish exaust plume when in afterburner. I still think my previously stated explanation of the J-20 having rather "high" bypass ratio engines (around .6 -.7 maybe) is the most likely reason. More unburned air is still available for further combustion, hence a cleaner process resulting in a more blueish flame, like on other afterburning turbofans with similar BPR (e.g. in Flankers, Lancers, or Tu-22).
While the very low BPR engines like F-119, EJ200 or M88 have a much more yellowish flame.
That brings me to the question of results for the design concept. Because of engines with a higher BPR having a lower specific thrust, but also lower specific fuel consumption, could that mean the J-20 is -if at all- a rather modest supercruiser with the design intent of having it fly generally more efficient in the high subsonic / low supersonic flight regime?
Supercruising, after all, still requires a much increased fuel flow, as supersonic drag is still way higher than high subsonic drag. I've seen statemens (by the air force association?) that a Raptor supercruising at M1.7 may decrease it's combat radius from 600nm to 450nm.
And then the F-119 engine has a very low BPR of .2, EF & Rafale engines are not above .4, for both types figures of M1.3-1.4 in supercruise are flying around.
The latest Su-35BMs have, however, "only" be quoted as reaching "M1.1 and accelerating" using the higher BPR 117S engines.
So can it be infered that in case of the J-20 range / endurance has been place above the need for (high) supercruise? Either because it is to cover such a wide area or because engine fuel efficiency couldn't just be made as good as required.
Well scratch, you did good on this one, they decreased the size of the vertical stabs 20% and moved them further aft from the center of yaw increasing their effectiveness to compensate. The F-22 was the result of the ATF program which had super maneuverability as one of the primary design objectives. The F-22 is indeed a very fine aerobatic aircraft able to perform the pugachev cobra, tailslides, and all the classic airshow moves. I would suggest that the Raptor is indeed the most agile of the fifth gen contenders, but as of today is still the fastest as supercruise capabilities are astounding. The J-20 has the potential to be a contender in these areas as well and that is where the real chanllenge lies, to meet these design objectives while at the same time increasing low observable characteristics. What remains to be seen as relates to all these objectives seems to be the integration of all these traits into one supercruising, low observable fifth gen bird, I'd say their on the right track.
Last edited by bd popeye; 01-16-2012 at 09:49 PM.
By challenge44 at 2012-01-16