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

helmutkohl

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^ thats true.. the YF-35 has this very futuristic next gen look, and perhaps why some like the SU-57 since it has a slight resemblance. That said I actually like the pudgy looking YF-22 over the F-22 tbh.
 

overscan (PaulMM)

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does the ultra version have moving canards? If they are I wonder the notion of having canards degrading frontal stealth more of myth than fact?
dbc-stealth-interceptor-1983-png.561721


The "Xmas Tree Fighter" had rear facing controls on its "canards". Not sure about the ultra stealth fighter which is its logical descendant.

Ultra stealth fighter was a 4 lobe design where everything had to be aligned in one of the 4 primary directions, this forced the "double canard" front section design.

Canards aren't incompatible with stealth if designed correctly.
 
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Ogami musashi

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USF is the one in the background in an alternative, more conventional, iteration, due to the fact the first one (the 4 lobe) was a mess aerodynamically and structurally. It didn't go past scaled wind tunnel testing and was ditched as it didn't work (so has told me Tony Chong).
 
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TomS

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does the ultra version have moving canards? If they are I wonder the notion of having canards degrading frontal stealth more of myth than fact?

I think it does. Both models have pretty clear movable surfaces on the main wing (both leading and trailing edges), with some sort of dots at the joints (set screws, perhaps). The canard has the same dots but no seams for a moving flap. So it seems likely the whole canard could articulate.
 

overscan (PaulMM)

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USF is the one in the background in an alternative, more conventional, iteration, due to the fact the first one (the 4 lobe) was a mess aerodynamically and structurally. It didn't go past scaled wind tunnel testing and was ditched as it didn't work (so has told me Tony Chong).
The more conventional USF is still a 4 lobe design. Look at the nose area.
 

Ogami musashi

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USF is the one in the background in an alternative, more conventional, iteration, due to the fact the first one (the 4 lobe) was a mess aerodynamically and structurally. It didn't go past scaled wind tunnel testing and was ditched as it didn't work (so has told me Tony Chong).
The more conventional USF is still a 4 lobe design. Look at the nose area.
Yes, I was talking about the aerodynamic configuration.
 

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does the ultra version have moving canards? If they are I wonder the notion of having canards degrading frontal stealth more of myth than fact?

I think it does. Both models have pretty clear movable surfaces on the main wing (both leading and trailing edges), with some sort of dots at the joints (set screws, perhaps). The canard has the same dots but no seams for a moving flap. So it seems likely the whole canard could articulate.
I think those planforms definitely put to bed the idea canards are unstealthy
 

Ogami musashi

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does the ultra version have moving canards? If they are I wonder the notion of having canards degrading frontal stealth more of myth than fact?

I think it does. Both models have pretty clear movable surfaces on the main wing (both leading and trailing edges), with some sort of dots at the joints (set screws, perhaps). The canard has the same dots but no seams for a moving flap. So it seems likely the whole canard could articulate.
I think those planforms definitely put to bed the idea canards are unstealthy
It is of course possible to make something not optimal, working with progress, so you could imagine making a stealthy plane with canards (the NATF-23 was to have canards). Now in this precise example, I don't think this really applies. See the original (1983) USF variant was the tailless one (the one with the outer wings angled 40° upwards), and it did not have moveable canards, instead it had flaperons on the second diamond. As you know, it revealed to be a complete mess aerodynamically, something that Paul Metz confirms in the above video (precising that the performance in high AOA was abysmal). The design team behind the USF was not the same than that of the HSF (later to become the F-23), and several attempts were made to make the configuration more workable (not only aerodynamically but also structurally). The configurations are from 1984 so probably posterior to the 1983 USF configuration. So it is probable they made some compromises on stealth to try and make the USF more workable.
 
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rooster

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It is of course possible to make something not optimal, working with progress, so you could imagine making a stealthy plane with canards (the NATF-23 was to have canards). Now in this precise example, I don't think this really applies. See the original (1983) USF variant was the tailless one (the one with the outer wings angled 40° upwards), and it did not have moveable canards, instead it had flaperons on the second diamond. As you know, it revealed to be a complete mess aerodynamically, something that Paul Metz confirms in the above video (precising that the performance in high AOA was abysmal). The design team behind the USF was not the same than that of the HSF (later to become the F-23), and several attempts were made to make the configuration more workable (not only aerodynamically but also structurally). The configurations are from 1984 so probably posterior to the 1983 USF configuration. So it is probable they made some compromises on stealth to try and make the USF more workable.
The middle picture clearly says ultra stealthy right below the high agility yf23 config...

Though I cannot find pictures i used to have from around 1987 a VHS I made that showcased a stealthy General Dynamics computer model with canards. I wish for the life of me i still had it.

Maybe someone here also saw that same program or has info about it. It was nothing similar to their famous single tail delta.
 
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Ogami musashi

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I didn't say it is not possible to make a stealthy aircraft with canards, I said the USF version you see here is most likely a version with degraded LO as compared to the original one which has only flaperons. I said that because the 1983 didn't go past mockup wind tunnel testing and was quickly dismissed as being unworkable, but the team behind it tried to make compromises on LO to make it viable (They failed apparently).
 

Cjc

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One thing I have seen repeatedly on this forum about the yf-23 that i would like to clear up now that I have my hands on "Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter" is that the yf-23 wasn't faster then the yf-22, the engine was. When both aircraft used the f-120 the speed was <0.1 mach apart and the range was only 20-30km apart (both in the yf-23 favor) frankly a difference so small as to be basically non existent. The idea that the yf-23 was faster and had more range was because for the vast majority of the tests LM used the less powerful and less fule efficient (but as events showed much more likely to actually be selected) f-119 engine wile McD/N used the better but much more complicated f-120 for all the tests, and consdering how little difference there was with the f-120 I suspect the also wouldn't have been much difference if the f-23 had been selected. The only advantage the yf-23 had over the yf-22 was in stealth, especially in IR detection, and the deeper bays that would work better for multi-role (and maby more missile if they could get the launcher right with the usaf wasn't sure could happen when the selection happened)
 

overscan (PaulMM)

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There is a difference between what was demonstrated by the tech demonstrator, what it potentially was capable of, and the predicted performance of the planned production model.

YF-23s spent 7.2 h at supersonic cruise at speeds between 1.4 and 1.6 Mach out of a total flight time of 65 hours.

YF-23 PAV1 (PW F119) was flown to Mach 1.8. YF-22 PAV2 (PW F119) was flown to Mach 1.81.

YF-23 PAV2 (GE F120) was flown to Mach 1.72. YF-22 PAV1 (PW120) was flown to Mach 2.0 in its very last flight (also to 7g, which was the highest G load demonstrated) after Northrop had concluded their test plan.

Regarding supercruise, YF-23 PAV1 (PW119) achieved Mach 1.43 on 18 September. YF-22 (GE120) achieved Mach 1.58 on 3 Nov.
YF-23 PAV2 (GE F120) achieved Mach 1.6 on 29 Nov. (According to YF-23 test pilot Paul Metz the highest supercruise speed achieved during flight tests is 'still classified".)

YF-22 PAV2 (PW F119) achieved Mach 1.43 on 27 Nov (again, after Northrop's flight test program was completed)

YF-23 PAV2 made only 16 flights in total. The flight test regimes tested were supercruise, not maximum supersonic speed. The YF-23 (GE F120) was predicted to be able to significantly exceed Mach 2.0. The YF-23 was expected to be controllable to 60 deg AOA, but only 25 deg was demonstrated.

You only have to look at how long it takes to expand the envelope of a modern fighter like the Typhoon or or F-35 to realise that in 4 months from first flight, you aren't necessarily exploring the far corners of the envelope. You carefully pick what you are going to do.

What the Dem/Val was supposed to do was show than each design could achieve supercruise with either engine, had a workable weapons bay, and general performance matching the sealed envelope predictions. YF-23 actually slightly outperformed predictions as its drag was a little lower than predicted.

So, no, the YF-23 didn't really fly faster than the YF-22 during Dev/Val. YF-23 intake had some aerodynamic issues that were cleared up in the EMD proposal. However, well-informed people believe that the YF-23 design was potentially faster in both supercruise and maximum speed. Whether this is right, we'll never know.

One of the differences in approach was that Lockheed demonstrated some things that weren't strictly required for the Dev/Val requirements, but which went down well with the Air Force evaluators, while Northrop stuck to the script.
 
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BDF

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When Cjc posted recently referencing the book "Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter", I was reminded that its a book that I haven't read before but have been wanting to. So thanks to him I went ahead and grabbed a copy. Highly recommended for those whom haven't read it. For those unaware, two of the authors were involved in the ATF on the civilian side and Col. Piccirillo was part the ATF program in the mid 80s then served on the source selection board during contract award.

As mentioned it's a great book with lots of interesting technical details. Two jumped out at me that I found interesting, one relating to this thread. That is that F-22 had a higher gross weight than the F-23. To quote the passage:

"In fact, Lockheed's winning ATF design reportedly had a higher gross weight than Northrop's due in part to the use of thrust vectoring on the Lockheed aircraft as well as having four tails surfaces instead of the two used in the Northrop design." pp 249 in the conclusion

If that's true that's interesting as the Northrop design is quite a bit larger in the cardinal dimensions but I'm not sure how they compare volumetrically. I know that Northrop was planning on using 15% more composites than Lockheed's original plan but I'm not sure if that plus the structural differences in the tail as listed above would be enough to compensate for that. Of course ultimately we'll never know for sure but I found that interesting.

The other item that stuck out to me was in the appendix discussing LO technologies, in particular in the IR spectrum. It's harder to find information on IR signature measurement and reduction so this is a welcome addition in this book. When discussing skin friction and solar heating for long wave IR detection, at the ATF supercruise point of M1.5 that aerodynamic heating raises to 150 deg F but is "largely negated by the cold (-70 deg F) temperatures at cruise altitude." (pp 284-285 in the appendix)

I'm sure there's more to it than this but this seems to suggest that the design goal of M1.5 could've been driven in part by this factor. It would be very interesting to see how the two designs compared in overall detect-ability in the IR spectrum. As this book was first published in 1998 I'm certain that IR detector technology has changed enough that this factor may not be quite as relevant now as it was back then.
 

icyplanetnhc (Steve)

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From Tony Landis.

Four generations of stealth preceded the design concepts for the first stealthy air-to-air fighters. To survive in the current air combat environment, the new designs combined stealth and high maneuverability with a long range supercruise capability. In addition to shape, these aircraft needed to prevent detection from radio transmissions, heat from the engines and other forms of energy detectable by specialized ground sensors.

The concept of an Advanced Tactical Fighter (ATF) dates back to 1971 during early studies of using stealth in the design of a modern fighter aircraft. Over the next decade, the U.S. Air Force’s Tactical Air Command (TAC) and other commands began to refine the requirements of the next generation of fighter aircraft. Despite limited and sporadic funding for these studies, most of the major aircraft manufacturers produced design concepts for the ATF.

In mid-1981 the Air Force released a formal Request for Information (RFI) to the leading aircraft companies. With no government funding for these one-year studies, each company absorbed the cost. The RFI was sent to nine companies: Boeing, Fairchild Republic, North American Rockwell, General Dynamics, Lockheed, McDonnell Douglas, Grumman, Vought and Northrop. Of these nine, seven chose to participate, submitting a total of 19 concepts. Vought and Fairchild Republic chose not to participate.

The 19 design concepts differed considerably in size, shape and maneuverability. As the studies progressed, the design parameters were refined from ‘Reduced RCS’ to ‘Low Observability’, to also include supercruise capability, advanced avionics and radar as well as high maneuverability. Concepts from each company incorporated some feature that would eventually be included in the design for the ATF. Winners of the competition were announced on October 31, 1986 with Lockheed and Northrop coming out on top. Instead of there being 5 losers, each prime contractor teamed with another member from the competition. Northrop teamed with McDonnell Douglas while Lockheed teamed with Boeing. The new aircraft received the designations of YF-22 for Lockheed’s design and YF-23 for Northrop’s.

Lockheed and Northrop used the prevailing years to refine their designs for the ATF so that by the time the selection was made, the ATF designs for each company evolved into a vehicle that closely matched those actually built. Along with airframe designs, two engine manufacturers were chosen to compete in the ATF competition. Pratt & Whitney entered with their YF-119-PW-100 design and General Electric went with the YF120-GE-100. One ATF prototype from each company would be powered using engines from each manufacturer. The first YF-22 and second YF-23 received the GE engines while the second YF-22 and first YF-23 received Pratt & Whitney powerplants.

Construction began almost immediately in order to meet the tight deadlines for the competition. Northrop was first to unveil their prototype in a rollout ceremony held at Edwards AFB on June 22, 1990. Northrop began engine runs the following month and the YF-23 moved under power for the first time on July 7. The YF-23 rapidly completed taxi testing with increasing speeds, culminating in the final high-speed test to 120 knots on August 11.

Unofficially dubbed ‘Black Widow II’, Northrop’s Prototype Air Vehicle (PAV) number 1 took to the air for the first time on August 27 making a near flawless one hour flight. Climb out was brisk, requiring the F-16 chase to use afterburner to stay with the YF-23 using military (non-afterburning) thrust. Northrop test pilot, Paul Metz, stated the aircraft was abnormally “solid” yet agile requiring few pilot stick motions to remain in tight formation with its safety chase aircraft. Lockheed unveiled their YF-22 prototype the following day in a ceremony held at Plant 10 in Palmdale, CA on August 28.

With the first flight completed, flight testing ramped up quickly. In order to maximize time aloft, the YF-23 qualified for air refueling on its fourth flight. Flying behind a KC-135 tanker, the YF-23 spent nearly three hours behind the tanker performing hookups and disconnects at various airspeeds and throughout the tanker’s boom envelope. Flight number 5 saw the YF-23 fly supersonic for the first time under the control of McDonnell Douglas’s test pilot, Bill Lowe. Afterwards the aircraft began testing supercruise speeds out to Mach number 1.5 and by flight number six, the first four YF-23 pilots received check out with the final pilot check coming with the program’s operational test pilot, Con Thueson, on flight number 11.

PAV-2 joined the flight program on October 26, 1990 with Jim Sandberg taking the GE powered aircraft on its first flight. Flights progressed rapidly with PAV-1 testing going well until October 30, when Bill Lowe experienced a shattered forward windscreen at Mach 1.5 during flight number 16. The glass outer layer of the windscreen cracked and the inner polycarbonate layer remained intact allowing for a safe landing. The same scenario repeated on PAV-2 nearly a month later.

Early flights in PAV-2 were troublesome. Its second flight was shortened when the left engine entered a sub-idle condition and would not accelerate and the plane made an uneventful single-engine landing. Flight number 3 on November 21 almost saw the end of PAV-2 when a plugged air sense line caused the fuel tanks to overpressurize. As the aircraft climbed in altitude, the internal pressures reached the structural limits of the fuel tanks. Quick action by the ground control room helped get the aircraft on the ground before serious damage to the airframe occurred. With these incidents behind them, PAV-2 settled in and became a reliable test aircraft. Both air vehicles now returned excellent performance data on the airframes, avionics and engines. The two prototype air vehicles flew together only once during the test program when Paul Metz in PAV-1 and Jim Sandberg in PAV-2 flew formation over the Mojave Desert on November 29. PAV-1 ended its flight testing career the following day with a six-flight surge and flutter test out to Mach 1.8, the highest speed attained by PAV-1. PAV-1’s flight test program lasted only 93 days.

With PAV-1 retired, all efforts were concentrated on expanding the supercruise envelope with PAV-2. The max supercruise speed with PAV-2 has never been publicly released, but it is stated to have been significantly faster than PAV-1. With funding running out, PAV-2 continued flight testing. On the next to last flight of PAV-2, a 15 minute formation with the first YF-22 occurred on December 18, this was the only time the two different prototypes flew together. The final flight of the program came during the second flight on December 18 when Ron ‘Taco’ Johnston took PAV-2 took up on a nearly 2 hour test mission. PAV-2’s flight testing lasted a mere 82 days.
Both aircraft were placed in flyable storage awaiting the decision on a winner of the ATF program. PAV-1 moved under power only three more times in January, February and March, 1991 during slow speed taxi runs to keep the aircraft in flyable condition.

The Air Force spent the first four months of 1991 evaluating the two airframe and engine proposals. On April 23, 1991, Secretary of the Air Force, Donald Rice announced that the Lockheed F-22 and Pratt & Whitney F119 won the competition for the ATF production contract. Secretary Rice’s announcement stated that both aircraft met the requirements for the ATF but the USAF had more confidence in Lockheed and Pratt & Whitney to ”manage” the program to deliver the weapons system on time and at cost.

After the ATF decision, both PAV’s, stripped of all government furnished equipment, including usable avionics & engines, were placed in outdoor storage in a small fenced area next to the B-2 test facility at Edwards AFB. After sitting in storage for nearly two years, ownership of both PAV’s was turned over to NASA on December 1, 1993. NASA Dryden Flight Research Center proposed doing structural testing of composite airframes but money was never found and both vehicles sat in outdoor storage in various locations around the center. 18 months after receiving the YF-23’s, NASA realized that no testing would be done and offered the airframes to museums. Ownership of PAV-1 transferred to the National Museum of the United States Air Force and the vehicle moved to the AFFTC Museum at Edwards AFB in May 1995 for temporary display. In August, PAV-2 was disassembled and transported to the Western Museum of Flight originally located in Hawthorne, CA but later moved to Torrance, CA. In 2000, PAV-1, disassembled and transported via C-5 Galaxy, went to the National Museum of the United States Air Force in Dayton, Ohio, where it is currently on display.
 
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X-39

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A bit of a silly story, guess it was not so stealthy in the acoustic aspect:
"Pratt & Whitney[..] did their engine tests in the Florida swamps so that they would be away from population.[..] Many years later[..] civilization moved out there, and the people got used to the sound [..]and the alligators got used to the sound, but the first time they ran the engine in full afterburner[..] there were reports the next morning of alligators climbing the fences of people's homes and diving into the swimming pools to get away from the noise"
 

donnage99

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One of the differences in approach was that Lockheed demonstrated some things that weren't strictly required for the Dev/Val requirements, but which went down well with the Air Force evaluators, while Northrop stuck to the script.
The fact that Lockheed had a workable weapon bay probably added to the prototype's weight, lowering its speed in comparison to the northrop prototype I'm guessing.
 

rooster

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One of the differences in approach was that Lockheed demonstrated some things that weren't strictly required for the Dev/Val requirements, but which went down well with the Air Force evaluators, while Northrop stuck to the script.
The fact that Lockheed had a workable weapon bay probably added to the prototype's weight, lowering its speed in comparison to the northrop prototype I'm guessing.
The kind of weight you're taking about is practically totally irrelevant to the speed difference between the 22 and 23. Look you want an example: with or without 2x 2000lb internal bombs, the 35s top speed is still m1.6. that's a 4000lb difference in a single engine aircraft and no penalty to max speed. The 23 was simply more aerodynamic. Having 4 tail surfaces the 22 had more drag to push through. Look at the thrust weight ratio of the sr71 and it's max speed
 

icyplanetnhc (Steve)

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Another aspect may be the YF-22 airframe was simply less refined than the YF-23, as the Lockheed team conducted a 3-month "fire drill" in summer of 1987 where Lockheed's original 090P proposal for Dem/Val was completely abandoned for an entirely different configuration. The EMD/production F-22 would also have a considerably slimmer rear fuselage around the engines, which may have reduced drag at the cost of fuel capacity. On the other hand, the YF-23 was very much similar to Northrop's original DP110 proposal, and would carry through to the EMD proposals, albeit more volumetric.

Of course, the purpose of Dem/Val wasn't an aircraft versus aircraft flyoff.
 

lantinian

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Another aspect may be the YF-22 airframe was simply less refined than the YF-23, as the Lockheed team conducted a 3-month "fire drill" in summer of 1987 where Lockheed's original 090P proposal for Dem/Val was completely abandoned for an entirely different configuration. The EMD/production F-22 would also have a considerably slimmer rear fuselage around the engines, which may have reduced drag at the cost of fuel capacity. On the other hand, the YF-23 was very much similar to Northrop's original DP110 proposal, and would carry through to the EMD proposals, albeit more volumetric.

Of course, the purpose of Dem/Val wasn't an aircraft versus aircraft flyoff.
You can actually go further and argue that the YF-22 airframe started in the summer of 1987. Lockheed actually abandoned their own design front and middle sections in favour of using Generall Dynamics ATF design.

Given the longer and much more area ruled airframe, the YF-23 design had significanly better supersonic performance even with the heavier trust reverser compatble aft section.
 

icyplanetnhc (Steve)

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You can actually go further and argue that the YF-22 airframe started in the summer of 1987. Lockheed actually abandoned their own design front and middle sections in favour of using Generall Dynamics ATF design.

Given the longer and much more area ruled airframe, the YF-23 design had significanly better supersonic performance even with the heavier trust reverser compatble aft section.
Yup. The F-22 ended up looking very much like a 4-tailed version of General Dynamics' ATF design, as discussed here. That design was optimized for maneuver and supercruise but struggled with all-aspect VLO due to the single vertical tail. Even so, it's likely that the revised tail design added cross section, and per Sherman Mullin, the YF-22's wave drag wasn't at acceptable levels until the thrust reverser requirements were deleted. The EMD/production F-22 further slimmed down the rear fuselage compared to the YF-22, although it may have lost fuel capacity and therefore range by doing that.

This is in contrast with the YF-23, where the "bread loafs" meant to accommodate thrust reversers were carefully factored into the area ruling. When the thrust reverser requirements were deleted, the EMD F-23 design kept the same cross section in the rear by smoothing over the nacelles and filling in the space between them to preserve the area ruling.
 

rooster

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You can actually go further and argue that the YF-22 airframe started in the summer of 1987. Lockheed actually abandoned their own design front and middle sections in favour of using Generall Dynamics ATF design.

Given the longer and much more area ruled airframe, the YF-23 design had significanly better supersonic performance even with the heavier trust reverser compatble aft section.
Yup. The F-22 ended up looking very much like a 4-tailed version of General Dynamics' ATF design, as discussed here. That design was optimized for maneuver and supercruise but struggled with all-aspect VLO due to the single vertical tail. Even so, it's likely that the revised tail design added cross section, and per Sherman Mullin, the YF-22's wave drag wasn't at acceptable levels until the thrust reverser requirements were deleted. The EMD/production F-22 further slimmed down the rear fuselage compared to the YF-22, although it may have lost fuel capacity and therefore range by doing that.

This is in contrast with the YF-23, where the "bread loafs" meant to accommodate thrust reversers were carefully factored into the area ruling. When the thrust reverser requirements were deleted, the EMD F-23 design kept the same cross section in the rear by smoothing over the nacelles and filling in the space between them to preserve the area ruling.
Had Lockheed not teamed with GD they would have lost. Lockheed was stuck on faceting ever since have blue. They were like your uncle who would come over for Christmas wearing a 20 year old suit with bell bottoms. Their bomber and fighter concepts were just variations on the have blue theme. Even the f35 is just a rehash of the f22. I remember the early days well of the yf22 and I recall congress actually was briefed that they shouldn't worry about the lack of radar stealth from side aspects because only the front mattered in combat. If you read the tea leaves and paid attention the yf23 was superior in every regard that mattered to the concept of the ATF except perhaps the weapons bay which again was GDs design. It doesn't matter too much as with barely 120 combat coded fighters, it's almost irrelevant.
 

BDF

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The EMD/production F-22 further slimmed down the rear fuselage compared to the YF-22, although it may have lost fuel capacity and therefore range by doing that.
The fuel capacity and weight gain issues that are often talked about as the Raptor went into EMD are often talked about but finding concrete information is difficult. I've been sifting through old AvWeek and Flight International articles and I'm fairly certain that the Raptor didn't put on nearly as much weight as was often been suggested. From what I've been able to piece together the contractor responsible weight, ie. just the air frame, gained roughly 4% and the original empty weight goal with the engines was around 40,000lbs. It gained just under 1,400lbs and the difference between the "official" weight is probably unusable fuel and fluids.

The fuel capacity issue is of similar vein. It's been often reported that the ATF prototypes carried around 25,000lbs of fuel. But Metz's F-23 book states that the YF-23 had a fuel capacity "a bit more than a F-15C with a center line external tank." That 18,000lbs. I'd be surprised if the YF-22 carried significantly more than the YF-23. So I suspect that the Raptor didn't loose a ton of internal capacity. I could be wrong though.
 

icyplanetnhc (Steve)

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Had Lockheed not teamed with GD they would have lost. Lockheed was stuck on faceting ever since have blue. They were like your uncle who would come over for Christmas wearing a 20 year old suit with bell bottoms. Their bomber and fighter concepts were just variations on the have blue theme. Even the f35 is just a rehash of the f22. I remember the early days well of the yf22 and I recall congress actually was briefed that they shouldn't worry about the lack of radar stealth from side aspects because only the front mattered in combat. If you read the tea leaves and paid attention the yf23 was superior in every regard that mattered to the concept of the ATF except perhaps the weapons bay which again was GDs design. It doesn't matter too much as with barely 120 combat coded fighters, it's almost irrelevant.

Well, not quite. Certainly during the ATF RFI phase, when the emphasis on stealth was increased, Lockheed's proposal shifted from an SR-71-like design to a highly faceted design resembling a tailed F-117. Of course, Lockheed would initially do rather poorly during the RFI phase (they were last place at one point), and after their faceted Senior Peg design lost the ATB competition to Northrop's Senior Ice (B-2), they shifted away from faceting, although their analytical methods appear to still trail Northrop at that time. The 090P design that Lockheed had submitted for the Dem/Val RFP had curved surfaces; again, the Dem/Val RFP focused on system engineering and technology development over point aircraft design, and the 090P was just one of several that Lockheed considered, and it's not certain if the company had proposals with delta wings.

That said, based on articles and diagrams from Lockheed Martin's Code One, the current F-22 can trace a significant part of its fuselage and wing configuration to General Dynamics' ATF proposal. After the RFP down-select, in the summer of 1987, the baseline 595-6 design proposal with trapezoidal wings and four tails was abandoned, and a variety of configurations was explored, with wings ranging from trapezoidal to diamond-like delta. Out of the various proposals, it appears that 607-0 with diamond wings similar to General Dynamics' proposal and four tails evolved into the 614, which became the chosen configuration and would evolve into the YF-22, design 1131/631, and the EMD/production F-22 configuration, design 645, we see today.

F-22 design evolution from Code One.

I apologize for taking this off topic, so I'll transfer the contents over to the F-22 thread. But to circle back to the YF-23, in contrast to the Lockheed/Boeing/General Dynamics collaborative process, I think it's clear that the Northrop/McDonnell Douglas F-23 is largely a gradual evolution of Northrop's original DP110 that submitted to the Dem/Val RFP. Aside from the smoothing over of the "bread loafs" nacelles and filling in the space in between, some of the visible evolutions include the nose shaping, which was gradually enlarged from the Dem/Val DP110 to the YF-23 DP117K, and even more so in the EMD F-23 DP231/232 proposals. The chines of the EMD F-23 would also be much less pronounced than the YF-23's (which in some ways is reminiscent of the SR-71's).

Also interesting to note is the change in IRST configuration; the original DP110 had the sensor on top of the nose in front of the cockpit and covered by a transparent panel that doesn't protrude from the OML. The EMD proposal would have the sensor under the nose with a protruding fairing, presumably for better look-down capabilities given the high operating altitudes. Interestingly, this is similar to one of the AIRST positions proposed and laboratory-tested for the F-22 some time during EMD.

In any case, this is now water under the bridge (this all took place before I was born!). For what it's worth, when taken as an overall system, in the eyes of USAF ATF chief engineer Rick Abell, both contractor teams' proposals had enough merits and were competitive such that the USAF would have an outstanding aircraft regardless of what was chosen, in contrast to some of the programs in his opinion (TFX/F-111 being one example).
 

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