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

[RadicalDisconnect]

So the F-23 is reported to have lower empty weight than the F-22, but I'm wondering how? It seems to have more volume than F-22 and is also longer. According to Wikipedia which cites Sweetman and Aronstein/Hirschberg, YF-23 apparently has 29,000lbs empty weight which is 2,000lbs lighter than YF-22 empty weight although that's claimed to be aircraft contractor weight without engines.

 

[martinbayer]

So the F-23 is reported to have lower empty weight than the F-22, but I'm wondering how? It seems to have more volume than F-22 and is also longer. According to Wikipedia which cites Sweetman and Aronstein/Hirschberg, YF-23 apparently has 29,000lbs empty weight which is 2,000lbs lighter than YF-22 empty weight although that's claimed to be aircraft contractor weight without engines.

Oh I don't know, but maybe more competent actual aerospace engineering capability (which at least at the time NG had a pretty stellar reputation for) might have had something to do with it? LM always seems to be great at debuting dazzling shiny new concepts (remember for example that nifty lifting body Venturestar SSTO RLV concept?), but falling miserably short on execution. Exhibit A: Mars Climate Orbiter.

 

[Hydroman]

Remember, the YF-22 did not look anything like the concept but the YF-23 changed very little.

 

[Sundog]

So the F-23 is reported to have lower empty weight than the F-22, but I'm wondering how? It seems to have more volume than F-22 and is also longer. According to Wikipedia which cites Sweetman and Aronstein/Hirschberg, YF-23 apparently has 29,000lbs empty weight which is 2,000lbs lighter than YF-22 empty weight although that's claimed to be aircraft contractor weight without engines.

Partly because of the diamond wing. The small tip chord and the long root chord are outstanding for minimizing structural weight since it greatly reduces the bending moment and also excellent for minimum wave drag at moderate super cruise speeds. Just look at the drawing where it shows the mach-volume distribution and you can see the production version was very damned close to the ideal at M=1.5.

 

[RadicalDisconnect]

Partly because of the diamond wing. The small tip chord and the long root chord are outstanding for minimizing structural weight since it greatly reduces the bending moment and also excellent for minimum wave drag at moderate super cruise speeds. Just look at the drawing where it shows the mach-volume distribution and you can see the production version was very damned close to the ideal at M=1.5.

Yes but the F-23 wing root chord doesn't seem much different from F-22?

 

[Sundog]

Yes but the F-23 wing root chord doesn't seem much different from F-22?

I never said the F-22 was poor in that regard, but the F-23 still has the larger root. I haven't analyzed the structures of both, but having the same sweep at the LE and TE may help as well. Also, the F-23 only had to take the load of two tail surfaces, versus four tail surfaces and TV on the F-22.

 

[Hydroman]

The F-23 in the middle, stretch it somewhat and you got the FB-23 (proportions about the same) and definitely built for high speed performance and LO. Any with the area of those v-tails, serious pitch authority. I may be wrong but it seems the F-23 would be good down on the deck as well.

 

[RadicalDisconnect]

2. What's the supercruise speed? (I answered that our current status is Mach 1.76)

Answering Question 2 is the only time his facial expression changed from that World Poker Tournament look.

Thought I'd share this experience with the forum.

What does this imply? Is the F-23 supercruise faster or slower?

I never said the F-22 was poor in that regard, but the F-23 still has the larger root. I haven't analyzed the structures of both, but having the same sweep at the LE and TE may help as well. Also, the F-23 only had to take the load of two tail surfaces, versus four tail surfaces and TV on the F-22.

True but the F-23 tails individually are also much larger and all moving, would that contribute to the weight?

 

[Trident]

I think it is hard to conclude from the available information that the F-23 would have been lighter than the F-22 on a like-for-like basis - are the quotes in the public domain for both aircraft truly comparable, without any unspoken asterisks? Extrapolating from the demonstrators is fraught with pitfalls IMHO, as mentioned by Hydroman one changed quite dramatically while the other would've less so. Then there's the essential fact that we cannot know how much weight growth the F-23 would ultimately have experienced if built, for the trivial reason that it never was!

Even between the airframes as configured during the fly-off you have certain discrepancies that are not easily accounted for, since the YF-22 performed tests (e.g. missile launches) that Northrop chose to skip. That means the YF-23 probably lacked equipment that Lockheed installed in their aircraft.

I will say that as a gut instinct I agree that the F-22 turning out heavier seems counter-intuitive. It is packaged very tightly which is typically a benefit, and the wing planforms are actually pretty close (although the aspect ratio on the F-23 does appear to be a hair lower still). The v-tail could be an advantage, a comparison of total tail area might give an indication - isn't tail surface weight considered to be proportional to area during weight budgeting in design? Also crucial mid-fuselage frames (wing carry-through) might have fewer "holes" thanks to the tandem arrangement of main and SRAAM weapons bays? Perhaps, counter-intuitively, tight packaging in fact operates as a disadvantage in aircraft with internal bays in this respect?

 

[BDF]

FWIW- Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter, which was written by three authors who were part of the ATF program (one is Al Piccirillo), states that the Northrop submission was lighter with the reasons given that the thrust vectoring solution was heavier as well as not having a conventional 4 post tail design. It seems extraordinary to me as well but I am not a engineer.

 

[Hydroman]

I know the YF-23 had a really good percentage of composite structure for a demonstrator, if I recall, upper and lower sections were one piece (books show the YF-23 large upper composite section) as an example. Also remember that Lockheed was touting using a lot of thermoplastic composites but eventually backed away in favor of thermoset resin-type of material and the YF-22 used a lot of metallics. Our composites folks at Northrop knew thermoplastics at the time were premature to use for large composite structures. So the YF-23 did use more composites for the structure as compared to the YF-22 and it was the thermoset resin-type. The F-23A on the other hand, was to exploit the use of composites to the maximum extent possible which could have gave the aircraft a very good empty weight.

True but the F-23 tails individually are also much larger and all moving, would that contribute to the weight?

 

[Hydroman]

What does this imply? Is the F-23 supercruise faster or slower?


True but the F-23 tails individually are also much larger and all moving, would that contribute to the weight?

The F-23 would have had a much higher supercruise speed from what I understand.

 

[TJDougherty01]

YF-23 at the US Air Force Museum back in 2010. Sheltered under the forward section of the B-70. At that point, the museum "overflow" hanger was on Wright-Patterson AFB pending additions to the main Air Force Museum.

 

[Trident]

FWIW- Advanced Tactical Fighter to F-22 Raptor: Origins of the 21st Century Air Dominance Fighter, which was written by three authors who were part of the ATF program (one is Al Piccirillo), states that the Northrop submission was lighter with the reasons given that the thrust vectoring solution was heavier as well as not having a conventional 4 post tail design. It seems extraordinary to me as well but I am not a engineer.

Good point about the TVC, though I doubt it constitutes a major contribution. Divergent-section vectoring, axisymmetric nozzles like PYBBN, AVEN or KliVT typically come with a weight penalty in the low dozens of kilogrammes per engine, even the Saturn ball-joint system is quoted at a mere 50kg. While the F-23 SERN-style nozzle is mechanically much simpler, it does share one of the issues that make the F-22 nozzles so heavy: the non-axisymmetric cross-section. So I would be surprised if the TVC system alone adds up to more than 100 - 200kg per aircraft, which in a ~20t airframe is almost negligible.

 

[icyplanetnhc (Steve)]

I think the phrases "much faster" was used to compare the YF-23 to the YF-22 by Paul Tackabury, manager of YF-23 test & evaluation, and with it being potentially supercruising at Mach 1.8, which is 0.2 M faster than the YF-22's Mach 1.58, that is considerable. That said the difference between the F-23A and F-22A is much narrower, and Advanced Tactical Fighter to F-22 Raptor book by Aronstein, Hirschberg, and Piccirillo (one of the ATF SPO managers and was on the decision board) characterized the difference as "slight".

As far as weight goes, I think the F-23 not having to contend with thrust vectoring loads helped with weight, not just in the nozzles, but also the airframe structure to handle the vectoring loads. The F-15 STOL/MTD aircraft identified the need for reinforcements of the aft fuselage to handle the vectoring loads. Also, with most of the aircraft volume being in front of the wing's trailing edge, the horizontal tails of the F-22 extend well past the main fuselage structure on booms, which needed to be pretty strongly built in order to handle the loads as well as mitigating ballistic vulnerability.

Northrop also did seem to be much more aggressive in terms of composite usage on the F-23, but I have to wonder if this wounded up being a major risk area. The F-22 did not use as much composites as hoped for, something Sherm Mullin acknowledged in his interviews, and during EMD unforeseen issues, such as live-fire testing of the wing structure and tail fin buffeting, both of them resulting in increased usage of titanium in lieu of composites. Thermoplastics were largely supplanted by thermosets as well. This isn't to say that the F-23 would have ran into the same issue since aircraft development issues can't be transplanted like that, but I would wager that it's another area of high risk, similar to the risks of aft deck strength and heating. Given the budget pressure it would have faced in the 1990s, while it's not certain, I wouldn't be surprised if the F-23 design would have also experienced weight growth.

 

[BDF]

Good point about the TVC, though I doubt it constitutes a major contribution. Divergent-section vectoring, axisymmetric nozzles like PYBBN, AVEN or KliVT typically come with a weight penalty in the low dozens of kilogrammes per engine, even the Saturn ball-joint system is quoted at a mere 50kg. While the F-23 SERN-style nozzle is mechanically much simpler, it does share one of the issues that make the F-22 nozzles so heavy: the non-axisymmetric cross-section. So I would be surprised if the TVC system alone adds up to more than 100 - 200kg per aircraft, which in a ~20t airframe is almost negligible.

Yes as Steve says it's not the extra weight of the engine but rather the beefed up structure to support the additional loads. That was not explicitly discussed in that book however. The exact quote is:

In fact, Lockheed's winning ATF design reportedly had a higher gross weight [sic] 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

As far as potential weight growth, Northrop was at the leading edge of composite material applications in the 80s and 90s. The ATB program led to the B-2 having something like 50-80% composites (depending on the source). I think it was less of a risk for Northrop than it was for Lockheed. That certainly doesn't preclude weight growth which seems to happen in every program to some extent.

 

[icyplanetnhc (Steve)]

Looking at the F-23A EMD drawings again, it appears that even though the inlets have a conical compression bump, there are still boundary layer control vents and doors. Was it ever documented whether or not the F-23 compression bump had any intention of diverting the boundary layer? The arrangement was also said to have reduced distortion from the trapezoidal profile from the PAVs.

It’s possible that these were designed in as a contingency for certain conditions that may require additional boundary layer bleed. The F-22A had additional BLC bleed doors right behind the inlets for high AoA conditions that were removed in later production lots (starting from 02-4028, I believe) when testing found them to be unnecessary.

 

[lantinian]

I personally haven't seen that video. Hope it's new to more people.

I am also willing to bet the angle it pulled around at 20 sec into it exceeded 25 AoA which was my first red flag that video probably isn't real but it looks dam cool.

Yeah, its not reall but I wish it was