Delta Wings, maneuvering, supersonic performance, and NGAD

Military aircraft - Post cold war aircraft, including for example B-2, Gripen, F-18E/F Super Hornet, Rafale, and Typhoon.
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viperzerof-2

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Unread post31 Dec 2022, 03:35

We have had a new topics as of late on NGAD and a number of discussions on the balance of seed cruise and mobility. Speculation has been on various configurations like a YF-23 or X-44 design.

I was kinda curious, not as speculation but curiosity, the possibility of delta wing design. Delta wings are good at super sonic and have very good instantaneous turn rates but suffer from poor sustained turning

As John Will explained back in 2009

“The XL wing, like any delta wing, has a flatter lift coefficient curve than a wing with lower sweep angle. So for a given wing area, it takes more angle of attack to produce a given amount of lift. More AoA in itself is not a bad thing, but along with more AoA comes more drag increase. Deltas also tend to have higher takeoff landing speeds (no flaps). Canards can be added to help reduce some of the disadvantages. Deltas are best suited for high speed cruise (Concorde, SR-71, B-70, B-58) and interceptors (F-102, F-106).

The top speed of XL was higher than the F-16, but by how much, we'll never know. At high altitude, high mach the climb rate and acceleration was excellent, but airplane was limited to 2.05 mach since analysis and testing had not been done to support higher speeds.” John Will


Delta canards can mitigate this somewhat but from what I can tell the Eurofighter by the experience of the Italian Air Force needs a lot of thrust to have a similar turn rate to the F-16 under 10000 feet (and much better above. The Rafale in the F-22 vs video bleeds speed at G an F-16 could sustain.

In the 90s general dynamics and the Lockheed proposed an F-16xl variant with an F-22 inspired wing.

Some claims about the wing design are rather spectacular

Addressing John’s point on the XL
https://ntrs.nasa.gov/api/citations/199 ... 022544.pdf
The wing planform is a clipped delta with leading-edge sweep of 50 ° and a trailing-edge sweep of -25 °. The wing camber, in combination with scheduled leading- and trailing-edge control surfaces, was designed to minimize lift-dependent drag at a Mach number M of 0.90 for sustained-g maneuver- ing, while minimizing trimmed drag at supersonic cruise conditions. (

It also mentions the potential for better sustained G in comparison to the F-16C (the paper compared them both at supersonic speeds, but wing only and did not measure other lifting surfaces.

Interavia
The F-16U will be about 25% heavier than the F-16C but should turn better, even with the current 129kN versions of the F110 and F100, because of the larger wing. The F-16U is also designed to be more stable at high angles of attack.

A more powerful engine, however, is very desirable to restore acceleration. In August, General Electric plans to run a 155kN F110 demonstrator with a higher-airflow blisk fan based on F120 technology, matched to the F-16's inlet, and fitted with a scaled-up version of the F414's composite-lined augmentor. Pratt & Whitney may offer its F100-PW-229 Plus.



From a 1990 AWST

Two fighter design programs are under way at General Dynamics for the Air Force’s Advanced Multirole Fighter competition that is to replace the current F-16 series sometime after the year 2000. The first program—designated the Falcon 21—is based on a design derived from the existing F-16. It would have supersonic cruise and supersonic maneuvering capability better than the current F-16 and subsonic maneuvering capability better than the F-16 Agile Falcon. It also has been viewed as a potential challenger to the Air Force’s advanced tactical fighter
(AW&ST Apr. 9, p. 16).


The current Falcon 21 configuration— Falcon 21-104—was developed from the basic F-16XL concept, with a new wing planforrn that gives a better compromise between subsonic and supersonic maneuvering capability. The new wing, with 630 sq. ft. of area, is a trapezoidal delta or so—called “clipped delta” design, with a biconvex airfoil shape that ranges from 0.4 to 8.5 deg. twist. It has a span of 34 ft. 8.3 in. and an aspect ratio of 1.91 with a leading edge sweep of 50 deg. The fuselage, which is 48.45 ft. long, could carry four semisubmerged AIM-120 AMRAAMs, with two advanced versions
of the AIM-9L Sidewinder or two ASRAAM missiles carried on under-wing pylons (AW&ST June 4, p. 24). Gross weight of the aircraft is projected at 35,320 lb., and the internal fuel capacity is 10,832 lb., giving it a fuel fraction of 0.31, greater than the existing F-16s, which have a fuel fraction of 0.29. General Dynamics officials said there are still questions as to whether an advanced derivative of the F-16 can meet Air Force ATF requirements. These requirements have not been finalized, but some may be beyond the capabilities of the Falcon 21.



That’s kinda shocking that an aircraft that heavy could turn like that even without the EFE engine. Am I misunderstanding? Can you make a delta wing aircraft with a very efficient wing that eliminates the issues of delta wing aircraft?


General Dynamics ATF proposal was quite similar to this configuration, and much like speculation that the YF-23 Configuration could influence NGAD I wonder if this might as well. It meets the fast long range super cruise criteria and potentially maneuverablity.
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Unread post01 Jan 2023, 19:49

So, after all the Wing Loading, Aspect Ratios, etc etc are accounted for... Drag due to lift is a factor of g, dynamic pressure, e (oswalds efficiency factor), and span loading squared (W^2/b^2).

(W/b)^2 for an airshow Viper is 810,000 at 27,000lb. This new Delta Viper would be 1,040,000 at 35,320 (a 4k increase in empty weight for the delta wing) so unless the "e" at the lift condition could be improved by 28% there isn't a way to get the same turning drag for the same turn. I have not studied how high e can get on a delta in a turn, but with the LEF/TEF scheduling and tail load adding to lift the F-16 seems well suited to keep e high already don'tcha think? If anyone has studied this and can shed light on it then I welcome the data.
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Unread post02 Jan 2023, 01:29

Salute!

Great thread.

As a nugget delta pilot in my early days, I would not put cannards on something nowadays. I would use the FLCS and control laws to limit AoA unless the pilot wants to bleed more "e" while making the bat turn, then die if the other guy doesn't overshoot or go verticle and you go down. Which always is not an options.

Something about that new "diamond" planform seems to be catching on, and maybe less induced drag in a hard turn. Or some LO science.

I still see too many folks are talking about supersonic and faster. The capability to go fast and burn as much as we did in the old days is nice, But I would not have my doctrine based on 1.6M cruise to the oncoming enema horde versus a comfortable 0'9M at 40,000 ft and the RCS of a bumblebee.

Make no mistake... I am not hung up on high tech and BVR and yada yada. It is very nice to be able to turn and burn with the best of them, but I look at the overall requirement and what we can do with the tech and the $$ here.

Finally, I found the Deuce the most comfortable "high performance' jet of those golden days, and would have loved to move on the "6".

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Last edited by Gums on 02 Jan 2023, 03:57, edited 1 time in total.
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Unread post02 Jan 2023, 02:01

Gums wrote:Finally, I found the Deuce the most comfortable "high performance' jet of those golden days, and would have loved to move on the "6".

Yeah, as I understand it the Six is what the Deuce was supposed to be. The Voodoo was the fastest of the jets you flew wasn't it? (I think it was functionally faster than early Vipers anyway)
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Unread post02 Jan 2023, 04:10

Salute!

The VooDoo and Viper were about equal in acceleration until above 1.5M, and then if you had another minute or two or more in full burner you could get the Viper up about 2.0M. BFD! Both accelerated up to 1.5M easily, but the 101 just quit, and both planes had fixed intakes....just that 20 years of engine and intake technology helped the F-16.

What surprised me the most about the Viper was it climbed about the same as the F-101B. Once up high and cooking, both went thru the mach about the same and could cruise at 1.1M for awhile...Voodoo did it until running outta gas by one motor in mil and the other in min AB. Viper would gradually come back subsonic after a few minutes in mil.

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Unread post02 Jan 2023, 14:51

Ah, thanks for clearing that up for me.
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Unread post02 Jan 2023, 15:52

I wasn’t expecting to get the all star team to respond to this thank you!


I’ve been hearing a lot about the Voodoo lately, it really seems to have been quite underrated.


With the F-16at, I thought it was a bit suspect that at that weight it could turn like that on wing design alone especially given most delta’s can’t, but if it was true it was too good to ignore when speculating about NGAD.
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Unread post02 Jan 2023, 16:50

Salute!

Thanks for the compliment, viperzero.

As far as initial thread point, I like the deltas, and the tech has now given us good performance where we are moving the battlespace - up high.

An interesting bit of info in original posts has to do with the wing's camber. When I checked out in 1965 we had two duece blocks - they were a combo of electronics and wing design. The electronics were "fig something" and the wing was "case something' So latest was Case 20, Fig 8. best I recall.

The baseline Deuce had a fairly straight leading edge , but the new ones and the "6" had a "conical" leading edge and it was very evident on the preflight. Somehow, this feature helped drag problems at higher AoA without using leading edge slats or slots. Seemed to help cruise fuel consumption, too. I noticed it most during the flare, as the new wing did not bleed off speed as much as the older version.
========================
As far as the VooDoo being a great interceptor, it was. Although we burned more gas per hour then the "6", and couldn't get up to 2.xM, we still did great for our mission, which was to shoot down Bears and Bisons. I routinely flew 200 miles north and orbited Canada by the north end of Lake Winnepeg for an hour. Then came home if no bandit on the NORAD radar. We guarded the "central flyway" that we thot the enemy buffs would use. Our Cannuck friends in their VooDoos were 200 miles further north!!!

Do not forget the VooDoo recce version did really well in the 60's, including missions over Cuba in 1962 and many over North Vietnam. My Double Ugly friends said it out accelerated them when making their final run for the target. I believe them and recount a short war story, then sign off.

My ex-tac officer from USAFA flew the things and asked for me to wait one day until fuel was below 3,000 lb. That meant our T/W was >1.0 Then at 400 KIAS light the ab's and pull up at 3 or 4 gees. I quit at 45 deg pitch and going thru 600 KIAS. In the Viper, I had my students sit at 400 KIAS and repeat the exercise but horizontal. Using a 3 gee pull in AB, 700+ kias at the 90 degree mark. Heheh. So a constant 9 gee at that speed had a slightly greater turn radius with no loss of speed and 15 or 20 deg/sec rate. Was easier to manage energy in the Viper than many people realized. Best speed for a knife fight was between 300 and 400 kias, maybe down to 200 kias at top of a vertical move.

Have a great new year folks. Live long and prosper.

"all star" Gums sends...
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Unread post02 Jan 2023, 17:15

Well, Gums is on the All-Star team with jonwill, Roscoe, TEG, and some other "old-timers." We have some "varisty" guys like 35_aoa, f119doctor, and other "been there done that recently" folks. I'm somewhere between "fantasy football" and "junior varsity," a lifelong aviation enthusiast who got degreed in Aerospace Engineering just to learn how things work. I don't even get to use my degree professionally, just for my hobbies (calculating/understanding performance).
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Unread post08 Jan 2023, 08:35

sprstdlyscottsmn wrote:Well, Gums is on the All-Star team with jonwill, Roscoe, TEG, and some other "old-timers." We have some "varisty" guys like 35_aoa, f119doctor, and other "been there done that recently" folks. I'm somewhere between "fantasy football" and "junior varsity," a lifelong aviation enthusiast who got degreed in Aerospace Engineering just to learn how things work. I don't even get to use my degree professionally, just for my hobbies (calculating/understanding performance).


Aw shucks... (thanks for the shout out!)
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Unread post25 Jan 2023, 17:08

Is it possible to make a highly maneuverable delta design without Canards? The French seem to think so with the Mirage 2000. But if thats the case, then why did they put Canards on the Rafale? From what I'm reading, the main advantage of the Canards is delaying the separation of the boundary layer from the main wing. This is useful in high AoA, but if thats the case, why are none of the Euro Canards particularly good at high AoA.

They're better than the F-16 but they come nowhere close to the Hornet or Flankers. They're only, slightly better than the Mirage 2000. If I'm not mistaken the main advantage of the Euro Canards over the Mirage 2000 was better energy in a turn, but this could be due to engines.
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Unread post25 Jan 2023, 17:14

The Rafale has canards to increase lift at lower AoA for a functional carrier approach speed. Deltas have "always" been highly maneuverable, they just bleed speed. None of the Euro canards are "particularly good at high AoA" for the same reason the F-16 isn't. Their FBW won't let them go there. More lift at lower AoA also helps with energy retention in turns.
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Unread post25 Jan 2023, 18:29

Oh I see, so can the function of the canards (providing more lift at lower AoA) be done with simply enlarging the wings? The Tempest mock up seems to have giant wings, will it compensate for the lack of canards.

As for energy, won't the canards also add more trim drag. are they less drag than bigger wings?
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Unread post25 Jan 2023, 19:10

No, because the way the canards (at least on the Gripen and Rafale) work is that they control the airflow over the wing (Typhoons are too far forward and are the pitch control surface, they might be pitch control on the Gripen but they are not on the Rafale). Larger wings make more lift, yes, and add a bunch of form drag and weight. Everything is a trade off, there is no perfect wing design. Canards do not add trim drag unless they are providing negative lift.
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Unread post26 Jan 2023, 03:30

sprstdlyscottsmn wrote:The Rafale has canards to increase lift at lower AoA for a functional carrier approach speed. Deltas have "always" been highly maneuverable, they just bleed speed. None of the Euro canards are "particularly good at high AoA" for the same reason the F-16 isn't. Their FBW won't let them go there. More lift at lower AoA also helps with energy retention in turns.

I found out today that apparently the Typhoon is AoA limited because of unwanted Yaw and rolling at high AoA. Older articles refer to it as having a 35 degree AoA limit, apparently that proved to not work out. The AMK apparently works by correcting this.
https://www.sto.nato.int/publications/S ... 307-19.pdf

The EAP was capable of 35 degree AoA. Early pre Typhoon concepts like the P.110 and TKF-90 apparently had twin tails like the hornet for high AoA. The P.110’s side intakes became the more familiar under intake on the multi national Agile combat aircraft which Primed the EAP, apparently because the Germans had done research indicating it was better for high AoA. The EAP was supposed to have a V tail but the German government pulled their funding at the last minute and the British substituted it with a modified Tornado tail. Later aerodynamic work showed the canards and V tail didn’t get a long.


P.110
3CF82FA9-014C-4FB9-A36B-A1AC87ECC255.jpeg

ACA
B3035226-7DE0-4C89-9CEA-E4476BF62002.jpeg

TKF-90
546A4D45-7CBF-4DDF-9737-0AD31BC6CBB7.jpeg
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