Northrop / McDonnell Douglas ATF - YF-23 and EMD F-23

[F-14D]

Considering the YF-23 is a bigger plane than the YF-22 and has significant area ruling is it feasible that an F-23A could have had the higher fuel fraction and less supersonic drag required to meet the original ATF supercruise requirement?

You know, although the YF-23 looked dramatically larger, in reality it was only three feet longer than the YF-22, had the same wingspan and wasn't as tall. Interestingly, although it could carry more internal fuel, its empty weight and normal operating weigh was actually less.

 

[sferrin]

Considering the YF-23 is a bigger plane than the YF-22 and has significant area ruling is it feasible that an F-23A could have had the higher fuel fraction and less supersonic drag required to meet the original ATF supercruise requirement?

You know, although the YF-23 looked dramatically larger, in reality it was only three feet longer than the YF-22, had the same wingspan and wasn't as tall. Interestingly, although it could carry more internal fuel, its empty weight and normal operating weigh was actually less.

I've always thought it was interesting how small it looked from pretty much every angle except looking down or up at it. You could show movies on the YF-22's vertical tails.

 

[F-14D]

he production version of he Raptor would be just under that

What I find interesting is how the production version of the F-23 would have had half shock cone inlets instead of the 3D oblique shock inlets and how they moved the engines closer together.

Was this really planned for production F-23s, or were these features of the proposed "F/B-23" of a few years back (visible on the model)? The cones could also indicate that higher speed was wanted for this latter mission, both the F-22 and F-23 designs top speeds being limited by their fixed inlets. If for strike reason a higher penetration speed was deemed Worth the complexity, they could be engineered in and the top speed would rise. This is the reverse of what was done on the F-14D. There, the aircraft was capable of speeds around M2.5. However, Navy decided that that extra speed wasn't worth the maintenance expenses. So, although the D have variable intake ramps they were deactivated, limiting operational Ds to M1.88-2.0.

Similarly do we know that production F-23s would have relocated the engines (a major redesign), or was this also something from the F/B-23, a;though in the latter case this may have just been how it appeared given the F/B's expected even larger weapons bay.

I, for one would be interested to know.

 

[flateric]

Have heard of half-cone inlets on EMD F-23 from the several sources that worth to listen. Top speed was limited not only by inlets, but by materials used in airframe. As well, high M numbers is something that wasn't in AF wishlist.

 

[sferrin]

Have heard of half-cone inlets on EMD F-23 from the several sources that worth to listen. Top speed was limited not only by inlets, but by materials used in airframe. As well, high M numbers is something that wasn't in AF wishlist.

BMI is better than aluminum when it comes to maintaining strength at elevated temps.

 

[flateric]

Haven't you read AWST 1991 article on BMI usage in ATF program? It reads like a horror novel...))) There were a heck of other problems with BMI instead.

 

[Sundog]

Did I lose someithing in the conventional tail offered? What's the advantage compare with the foreplan? You keep nose down, I keep nose down either.!

Yes, you did. There are areas of the flight envelope where a conventional tail works much more efficiently than a canard does. That's why none of the latest U.S. fighters have canards.

 

[sferrin]

Haven't you read AWST 1991 article on BMI usage in ATF program? It reads like a horror novel...))) There were a heck of other problems with BMI instead.

Never said it was trouble free from the beginning. Just said it's better than aluminum at elevated temps. And that was 16 years ago. BMI is fairly common these days.

 

[LowObservable]

<<I've always thought it was interesting how small it looked from pretty much every angle except looking down or up at it.>>

Errrrmmmm....

I think that was kinda sorta the whole idea. An air-combat nuclear attack submarine.

 

[sferrin]

<<I've always thought it was interesting how small it looked from pretty much every angle except looking down or up at it.>>

Errrrmmmm....

I think that was kinda sorta the whole idea. An air-combat nuclear attack submarine.

Someone forgot to tell that to Lockheed.

 

[rousseau]

Did I lose someithing in the conventional tail offered? What's the advantage compare with the foreplan? You keep nose down, I keep nose down either.!

Yes, you did. There are areas of the flight envelope where a conventional tail works much more efficiently than a canard does. That's why none of the latest U.S. fighters have canards.

The lost thing still Is WHY conventional tail will be much more efficient than canards? ???

 

[F-14D]

Have heard of half-cone inlets on EMD F-23 from the several sources that worth to listen. Top speed was limited not only by inlets, but by materials used in airframe. As well, high M numbers is something that wasn't in AF wishlist.

Granted high M numbers above what YF-22/23 achieved was something for which AF said it would not give credit, but I'm not sure that airframe materials would really have been a limiting factor up to M23.-2.5. After all, F-4 did not use what we would consider exotics, and it did M2.6. My point was that ATFs were limited to M2 and below by their fixed inlets, again AF saying it was not willing to pay for the complexity required to get another M0.5. I was wondering if cones shown in F/B-23 were there for reasons that might indicate variable inlets (ala Mirage) in that model, indicating a desire for higher top speed.

 

[F-14D]

My dear friend:
you'd better know what was you said equal factually is dissimilar.
foreplan could be smaller than horizontal stabilizer so the structual weight will be reduced.
foreplan will give a smaller balanced drag than conventional horizontal stabilizer, no matter where the barycenter you put.
the area of delta wing adapt to the foreplan will be bigger than conventional layout so give more lift the maneuver needed.

As I've stated before, canard aircraft tend to be lower cost, because they tend to have lower weight, for the mission, precisely because you don't need the tail structure that a conventional aircraft requires.

However, most modern fighters are unstable. As such, the canard is usually sized to push the nose down at high alpha. That means the canard is working against the wing. Whereas with the conventional tail it provides lift to keep the nose down in the same regime. As such, it turns out there are areas of the envelope where the canard can't trim the aircraft as effectively because the conventional tail offers advantages in sizing in this part of the regime. This is one of the reasons why Lockheed's F-35 went from a canard design to a conventional tail. There are other areas of the envelope where the conventional tail is better as well.

However, for many nations, cost is the number one driver, which was one of the primary design drivers for all of the new European Fighters having been built as canards instead of conventional tail configurations.

I wonder it it's simply a cost issue or whether it is a different design philosophy as well as something as simple as current "fashion" in the US engineering world. It might well be true that at extreme AoA the conventional tail has an advantage (although with the modern use of using the wing trailing edge as large maneuvering surfaces instead of just a flap a canard wing could have a large "up force" at the rear), but with missiles like ASRAAM IRIS-T, AIM-9X out there, especially combined with Helmet Mounted Sights (which F-22 lacks, BTW), extreme AoA may not be as important as it was 20-25 years ago. It's worthy of note that Typhoon is more maneuverable overall than any US fighter, with the possible exception of the F-22, and Rafale and Gripen (especially the former) may be able to make the same claim. Of course, Typhoon is not a close coupled canard as the others are. I'm attaching a view of Typhoon; look where the canard is relative to the pilot.

Canards give away certain parts of the envelope to conventional planforms, but they also have some advantages as well. On takeoff, on the approach or at low altitudes, for example, the conventional tail works against the wing. To raise the nose or hold a positive AoA, a conventional tail exerts a downward force, negating some of the lift of the wing, requiring more thrust or a bigger wing or more required speed. With a canard, both surfaces are exerting an upward force, increasing lift at lower speeds. This can result in shorter ground runs and safer approaches and departures, which may be a big driving factor for the Europeans, who apparently aren't convinced that there will always be a 9,000 foot runway available. One thing that's also a factor is the incredibly high thrust/weight ratio of modern fighters. Rules that apply to virtually all other aircraft types get "bent" for fighters because of their ability to power out or through situations that would "trap" any other aircraft.

On the other hand, it's harder to "stealth" a canard, because normally the canard is not in line with the main wing and so there are two surfaces for radar to see.

On the NATF, the Navy may have been willing to accept less extreme AoA, given that they were expecting AIM-152 and some form of dogfighting missile to be arming it in return for slower, flatter approaches which the canard (like a vg wing) could provide.

 

[sferrin]

My point was that ATFs were limited to M2 and below by their fixed inlets,

The F-22 is not limited to Mach 2. A fixed intake is not necessarily a limiter (the XF8U-3 also had a fixed intake and it EASILY exceeded Mach 2 as well).

 

[Woody]

??? Did I lose someithing in the conventional tail offered? What's the advantage compare with the foreplan? You keep nose down, I keep nose down either.! : 8)

You must have missed the bun fight on this one but this submission from Lantinian is enlightening:-

AIAA Paper 84-2401
Forward
Past investigationsl-5 have differed on the best choice between tail and canard for future tactical aircraft employing fined, low aspect ratio wings. A previous Grumman USAF study1 of an advanced strike fighter emphasizing supersonic persistence showed the superior trim drag characteristics of a canard. Northrop argued that a tail design has lower subsonic maneuver trim drag and greater stability c.g. location flexibility and is therefore the preferred configuration for an air combat fighter. A General Dynamics study3 indicated that a canard quipped F~16d design had potential high AOA stability and control problems when balanced at negative static margins; as a must the tail arrangement had a better subsonic trimmed polar and a Similar supersonic trimmed polar. An incompressible lifting system analysis found a tail to be the better choice. The message seems to be clear: the selection of a canard YE a tail is both configuration and mission dependent.

Conclusion
Equivalent canard and tail control surfaces are compared on an advanced, carrier-based fighter/attack aircraft featuring variable wing sweep and vectorable, two-dimensional nozzles. Evaluations of stability and control characteristics, trimmed drag due to lift, minimum takeoff rotation speeds, and carrier approach speeds are presented. The results show that the canard configuration has substantially less supersonic trim drag and a lower carrier approach speed, which can yield appreciable takeoff weight savings, but the tail configuration exhibits better stability and control characteristics with less development risk.

There must be some advantage of conventional tails over foreplanes in terms of drag (sub and supersonic) why else would they do it?, but I've yet to fully understand why. If you want to see the full thread the link's below.

http://www.secretprojects.co.uk/forum/index.php/topic,1624.0.html

Cheers, Woody

 

[rousseau]

Hmmm, maybe I do lost something very important. The AIAA Paper 84-2401 file you posted via quote is only a part of complete version so that display an amphibolous explain, could you send me a whole file? 8)

 

[overscan (PaulMM)]

No requests for articles or books, please.

 

[lantinian]

My point was that ATFs were limited to M2 and below by their fixed inlets,

It is my understanding of flight that an object does not necessary need variable inlets to travel supersonically. Most asteroids that enter the earths atmosphere do not have even aerodynamic shape, yet they travel trough it quite fast indeed.

To end the joke with a reasonable and usefull comment I would say.

Variable geometry inlets allow a much more efficient flight at supersonic speeds to justify the extra complexity.
The ATFs however have a lot of excess trust available and can go over Mach 2 without problem. (reports say F-22 reaches Mach 2.4)

However, due to raised drag and raised temperatures ( stealth coatings have low temp limits) the YF-23 and now F-22 were not thought out to be flown at speeds above Mach 2 operationally (at least not for more than minute or two). The inlet designs were therefore designed to be most efficient at cruising speeds of Mach 1.5+

Further, some recent design innovations in this area, like the devertless inlet on the F-35 do allow even simpler design to perform well up to Mach 2.

Finally, the drawings available for the production F-23A (earlier in the tread) do suggest a similar divertless design with a fixed cone shape inside the inlet. Clearly the engineers have figured out that a inlet design that had an order of magnitude lower RCS but a little higher drag is of more value now if you can still reach Mach 1.5 at about 80% throttle setting.

regards,
lantinian

 

[flateric]

Some extra shots with details of YF-23 weapon bay [doors] with provisions for AIM-9 launcher and, of course, Paul Metz.

 

[rousseau]

Good post Flateric!
Although only one bomb bay can be dimly seen, your post proved this pic.

 

[Sundog]

My point was that ATFs were limited to M2 and below by their fixed inlets

If they were using 2-Dimensional shock structures and mechanics like 1960's era fighters, that would be true. However, the ATF designs used three dimensional shock structures which offer greater pressure recovery and they also used other technologies, such as porous materials and possibly fluidic controls to manage their shock structures which offer the ability to control the inlet flow without mechanical controls, thereby maintaining their L.O. properties over the speed range. It's been reported that the second YF-23 prototype with the GE variable bypass engines had a top speed of M=2.8+. I can't confirm that, it's only what was reported.

 

[flateric]

Heard of M=2.3 for PAV-2, but figure seems to be not so exspressive to make it classified for 18 years...

 

[lantinian]

ATF inlet designs had the ability to control the inlet flow without mechanical controls

Thanks Sundog! Its good to learn something everyday. I allways though the inlet designs were a compromise betwen LO and Speed. Apparently not!

It's been reported that the second YF-23 prototype with the GE variable bypass engines had a top speed of M=2.8+.

It now makes sense in terms of available trust (1.5+ times more than F-15) and aerodynamics (Extensive area ruling, higher sweep angles and advanced inlets). However, I still doubt the max supercruise to have been more than Mach 2.1. At higher speed the supersonic cone will overlap the wing tips and that coupled with the aerodynamic heating will likely compromise the integrity of the LO coatings. Not to mention that the IR signature at front will rise enough to challenge the rear one, substantially increasing the range of hostile IR sensors.

Still, in terms of sustained speed it seams the production F-23A could have been just as much faster than YF-22 as YF-22 was over F-15. WOW!

 

[rousseau]

Over M2.8.......
Sundog must be a fans of US jet. ;D I love you!

 

[flateric]

Bismaleimide (BMI) and carbon fibres (Hercules AS-4 fiber, mostly, in the case of YF-23) possess excellent mechanical properties in the 150 C to 232 C range.
Large sections of YF-23 airframe was made of carbon/BMI composites
If travelling at M=2.8-3.2 range SR-71 has lowest T at the center top/bottom of fuselage (the coldest area) of 250 degrees C, not talking of leading edges and chines with Ts in 315-340 C range...Canopy glass has about 300 C *after* landing! Northrop has a *great* problems at M=1.4-1.6 with engine cowls heating - and not aerodynamic, but from the engines core!

 

[AGRA]

Where did you get the number as only 0.29 for F-22A or YF-22?
The correct calculation of fuel fraction is internal fuel capability/weight empty.
so even the internal fuel of F-22 down to 10 ton, the empty weight up to 17 ton. the fuel fraction also will be reach 0.59!! You put the wrong number not is on basic digit but on tens digit!

Fuel fraction is determined by whatever weight the aircraft happens to be divided by the weight of the amount of fuel in it. Any empty aircraft would have a fuel fraction of 0 unless it needs to have a certain amount of fuel onboard at all times for some kind of structural or maintenance reason.

Of course the most important fuel fraction figure is the aircraft in a typical combat mission configuration ready for engine start up and takeoff. One then takes this weight and divides it by the amount of fuel in the aircraft for this configuration. A subsequent fuel fraction of 0.3 typically means a good range for a conventional subsonic cruising aircraft. Because of the higher fuel burn demands of the ATF’s supercruise mission a higher fuel fraction was needed to provide a reasonable mission radius.

 

[rousseau]

Well, if my understanding is right
Even though the fuel fruction should be internal fue/ empty weight + internal fuel
then Su27 = 9.3/(9.3+17) = 0.35
F22 = 10/(10+14.5) = 0.41
conclusion is that ff of Raptor is still higher than Flanker

 

[flateric]

YF-23 manufacturing and 'Iron Bird' pics from West Coast Images 'YF-23 Black Widow II Declassified'
For Details and Ordering http://www.wci-productions.com/2.html

 

[Sundog]

If travelling at M=2.8-3.2 range SR-71 has lowest T at the center top/bottom of fuselage (the coldest area) of 250 degrees C, not talking of leading edges and chines with Ts in 315-340 C range...Canopy glass has about 300 C *after* landing! Northrop has a *great* problems at M=1.4-1.6 with engine cowls heating - and not aerodynamic, but from the engines core!

1) How much of the heat/energy was transferred to the fuel? You do realize that the YF-23 most likely, like the F-22, circulated it's fuel under the skin to absorb the heat from high temperature flight.

2) Just because an aircraft "can" supercruise at a very high speed, I never stated the amount of time it could operate at that speed. For instance, the ATF design specs said it needed to supercruise for one hour. I don't remember if that was M=1.5 or slightly higher (the specs, not the actual capability). The aircraft don't heat up immediately. It takes time to get there.

3) As for the heating of the engine cowls, that tells me they had insufficient cooling around the engines. That really isn't surprising in a prototype. That still doesn't mean it's top end speed was immediately limited.

Sundog must be a fans of US jet.

Actually I'm a fan of all aircraft. Fortunately for me, I still remember many of my lessons from my compressible aerodynamics courses.

 

[flateric]

YF-23 would undergo subtle changes if it wins competition.
Source: Defense Daily
Publication Date: 14-JAN-91

The Northrop/McDonnell Douglas YF-23 Advanced Tactical Fighter (ATF) full-scale development production
aircraft would undergo some subtle changes in configuration from the prototype design if the Air Force chooses
it for its air-superiority fighter, YF-23 Program Manager Thomas Rooney said last week.

YF-23 engineers, after reviewing test flight information, decided to make changes in the airframe to improve
the flying quality and low-observable signature of the aircraft, Rooney said.

Among the most obvious changes, the two distinct boxy humps, where its two engines are housed, will be
smoother. With the advent of a down-select the aircraft will be tailored to fit one engine type rather than two.
General Electric and Pratt & Whitney are locked in competition for the ATF engine contract, while the
Lockheed/Boeing/General Dynamics team is competing with the Northrop team for the airframe contract.
Rooney said the aircraft inlet cell will also be changed slightly to reduce the aircraft's radar cross-section. "The
change has been tested on a full-scale model," Rooney said.
In addition, the trailing edge of the aircraft's stabilizers will be changed slightly, altering their intersection with
the aft deck of the fighter, Rooney said.
The prototype aircraft utilized a greater percentage of titanium metal in its wing structure because the
prototype manufacturers had "problems with the scheduling and did not want to risk doing the substructure of
the wing with composites because they had more experience with the use of titanium structures," Rooney
said. Approximately 50 percent of the YF-23 production model structures will be composites. The aircraft will
be in the 55,000 pound weight class, according to Rooney.

Northrop Unconcerned About Missile Firings
Rooney said his team was not concerned with the Lockheed team's decision to fire Sidewinder and AMRAAM
missiles, which he says were not a requirement of dem/val. "We make a list of what we feel is important and
we didn't share our list with Lockheed ... and they didn't share their list with us," he said. "We didn't think that
launching a very mature missile at seven-tenths Mach in level flight had any meaning whatsoever. (We) were
concerned about ... the environment in that weapons bay at very high speeds."
Test Pilot Paul Metz said that to a less experienced pilot, the opening of the bay doors on the YF-23 would
have gone unnoticed in the cockpit, but he noticed acoustic levels were a little higher than anticipated. Metz
said small adjustments to the spoiler corrected the problem.
Regarding news that Lockheed had displayed its YF-22's ability to attack from a 60 degree angle, Rooney said,
again, that Northrop decided that a 25 degree angle of attack was all that was needed in dem/val.
Metz said the YF-23 could come through any angle of attack "even backwards." He said the aircraft can regain
control out of zero airspeed but it would have to fall to pick up the speed again. "No matter where it's at or
oriented it will come out and start flying," Metz said. This airplane, as designed, has the best high angle of
attack and spin characteristics of any airplane ever built by McDonnell Douglas or Northrop." Metz said the
YF-23 topped T-38s, F-5s, F-15s and F-18s, which are considered premier high angle of attack airplanes today.

 

[lantinian]

Most people quite logically assume that the YF-23 having somewhat bigger profile is larger and heavier. Also, that is was a more a concept demonstrator than a prototype with many parts from other aircraft.

Approximately 50 percent of the YF-23 production model structures will be composites. The aircraft will be in the 55,000 pound weight class, according to Rooney

Quite the opposite seams to be true. Not only had YF-23 a more advanced internal structure but it was also lighter as a result. The F-22 as we know today is considered to be a 60 000lb + pound aircraft.

Another commom misconception is that the YF-23 will undergo a more radical change than the YF-22 from a prototype to production stage.

some subtle changes in configuration

is what says the YF-23 program manager. I also think that making an airplane longer is easier and less troublesome than changing the wing sweep and the shape of the entire forward fuselage, as was the case with F-22

 

[KJ_Lesnick]

After reading, you can rename the thread

I take it this is a what-if design? If so, I'd change the nozzles (same shape but cover more of the top) to make a thrust vectoring design more like the F-22.

If they were using 2-Dimensional shock structures and mechanics like 1960's era fighters, that would be true. However, the ATF designs used three dimensional shock structures which offer greater pressure recovery and they also used other technologies, such as porous materials and possibly fluidic controls to manage their shock structures which offer the ability to control the inlet flow without mechanical controls, thereby maintaining their L.O. properties over the speed range.

I thought 2D shapes yielded better efficiency (at least with hypersonic waveriders -- but the same thing that would produce high pressure recovery would produce high lift on such a design)...

What's a fluidic control? And what's L.O. properties?


Kendra Lesnick

 

[lantinian]

I thought 2D shapes yielded better efficiency

Cooling efficiency Yes, but trust efficiency - NO

What's a fluidic control?

Ability to change the direction of the exaust trust without moving parts. X-36 had such technology on it.

And what's L.O. properties?

Low Observable = Stealthy

 

[KJ_Lesnick]

Cooling efficiency Yes, but trust efficiency - NO

I would almost swear I read that the 2D design (with delta-wings, but the compression ramp was wedge shaped) produced lower overall drag...

So a highly-swept design is more efficient?

Ability to change the direction of the exaust trust without moving parts. X-36 had such technology on it.

Assuming that's not clasified, how the hell do they do that?

Low Observable = Stealthy

Thanks


Kendra Lesnick

 

[lantinian]

I would almost swear I read that the 2D design (with delta-wings, but the compression ramp was wedge shaped) produced lower overall drag...
So a highly-swept design is more efficient?

I think, this is actually quite simple geometry. A Circle will always have less circumference than a Rectangle for a similar area. So, if for any shape where the other types of drag are equal, the tube like shape will have less parasitic drag, as it exposes less area to the airflow. If 2D design were more aerodynamic and flight efficient, bullets would not had a round shape now would they? The main advantage of using 2D Nozzles is in heat management and better easier LO integration with the rest of the design.

A highly swept design has nothing to do with the above argument.

Quote
Ability to change the direction of the exaust trust without moving parts. X-36 had such technology on it.

Assuming that's not clasified, how the hell do they do that?

I hope you run a google search before you asked that. If not try it and check one of the many articles on the subject. It's not rocket science but its not a short explanation either.

And please keep your questions relevant to the topic, or create another one after you have made the relevant search.

 

[KJ_Lesnick]

I would almost swear I read that the 2D design (with delta-wings, but the compression ramp was wedge shaped) produced lower overall drag...
So a highly-swept design is more efficient?

I think, this is actually quite simple geometry. A Circle will always have less circumference than a Rectangle for a similar area. So, if for any shape where the other types of drag are equal, the tube like shape will have less parasitic drag, as it exposes less area to the airflow. If 2D design were more aerodynamic and flight efficient, bullets would not had a round shape now would they? The main advantage of using 2D Nozzles is in heat management and better easier LO integration with the rest of the design.

A highly swept design has nothing to do with the above argument.

Makes sense, but I specifically remember being told on hypersonic waveriders that the 2D shape results in less drag...

 

[flateric]

Damn, this is YF-23 topic!

 

[Sundog]

I take it this is a what-if design? If so, I'd change the nozzles (same shape but cover more of the top) to make a thrust vectoring design more like the F-22.

Northrop considered thrust vectoring for the YF-23, IIRC, but didn't go with it because the YF-23 met the maneuvering specs without them and they decided to go for more L.O. instead.

 

[SOC]

I take it this is a what-if design? If so, I'd change the nozzles (same shape but cover more of the top) to make a thrust vectoring design more like the F-22.

Northrop considered thrust vectoring for the YF-23, IIRC, but didn't go with it because the YF-23 met the maneuvering specs without them and they decided to go for more L.O. instead.

The initial requirement had for thrust vectoring had to do with short field performance. When the USAF dropped the short field requirement, Northrop deleted the TVC system. However, both PAVs were built with nacelles and nozzles sized to take the TVC system. Production aircraft would have had slimmer overwing nacelles.

 

[Sundog]

You're confusing thrust vectoring with thrust reversing. Thrust reversing is a kind of vectoring, but not the same thing. The thrust reversers the YF-23 would have had would have been ahead of the nozzle, I believe similar to how the F-15 SMTD's reversers were mounted, but on the top side only on the YF-23. That's why the production version would have had shorter, lower weight nacelles, compared to the EMD which had nacelles designed to fit them.