YF-22 vs YF-23

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wooster

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Unread post31 Jul 2019, 01:44

f119doctor wrote:One of the complications on the YF-23 all Flying V Tail surfaces was the actuators needed for these large control surfaces. The solution was a stepped piston actuator. Only the smaller inner diameter was used at slow speeds where the dynamic loads were low and large / fast tail movement was necessary. At high speed where high force was needed to move the tail surfaces, the actuator shifted to use the larger diameter of the stepped piston. The smaller surface deflections at high speed allowed the limited flow capacity hydraulic pumps to keep up in this high force / large piston condition. A hydraulic system flow capacity increase (pump sizes, line diameters, coolers, heat rejection, etc) had unacceptable trade offs to use a single large diameter actuator for both conditions.

One of the Northrop flight control challenges was to manage the shift of the actuator from the large deflection mode to the high force mode as the aircraft acellerated and maintain acceptable handling characteristics during the shift. I believe that they were mostly successful, although the test pilots did report that the shift point was noticeable.


Wow, great write up. Never heard of that before. It just shows how much ingenious thought went into making it stealthier and the weight that Northrop put into stealth. I can't believe they publicized that system to the white world. How does that differ from say the tail surfaces of the B1 which are also large and the bone flies subsonic and supersonic and is quite good at maneuvering.
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madrat

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Unread post31 Jul 2019, 02:14

The Bone has much more capacity to power actuators and doesn't require such high performance adjustments.
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zero-one

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Unread post03 Feb 2020, 09:19

Cam across this article from Quora while researching on RCS stuff.
Capture3.PNG


Turns out, RCS measurements, much like maneuverability is not as simple as Airplane A is better than B.
Here we see Northrop's design has better broadband stealth characteristics while Lockheed's design completely wipes the floor in the higher frequencies. Now I'm not saying this is what happened with the YF-22 and 23, All I'm saying is its not as simple as Airplane A > Airplane B
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disconnectedradical

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Unread post03 Feb 2020, 14:11

zero-one wrote:Cam across this article from Quora while researching on RCS stuff.
The attachment Capture3.PNG is no longer available


Turns out, RCS measurements, much like maneuverability is not as simple as Airplane A is better than B.
Here we see Northrop's design has better broadband stealth characteristics while Lockheed's design completely wipes the floor in the higher frequencies. Now I'm not saying this is what happened with the YF-22 and 23, All I'm saying is its not as simple as Airplane A > Airplane B


Wipes the floor?? Range is proportional to the fourth root of RCS, so based on your picture at highest frequency, Lockheed's design only reduces detection range by 25%, while at low frequency Northrop's design reduces detection range by 66%.

Maybe understand the radar range equation before making such statements?
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zero-one

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Unread post03 Feb 2020, 16:36

disconnectedradical wrote:Maybe understand the radar range equation before making such statements?


You're talking about the inverse square law for the Rmax equation, yes I'm familiar, but if you read my statement it says
the Lockheed's design completely wipes the floor in the higher frequencies
This is because in 3 out of the 4 examples given, Lockheed had better results.

But lets take the Rmax equation and say that Peak power, Antenna gain and Noise floor are all equal.

1600 = Lockheed's Rmax is 32% better
8400 = Lockheed's Rmax is 47% better
2300 = Lockheed's Rmax is 66% better
175 = Northrop's Rmax is 76 times better.

Again Lockheed's design had advantages of at least 30% on most frequencies specially on the ones more commonly used for high quality weapons tracking.
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disconnectedradical

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Unread post03 Feb 2020, 21:49

zero-one wrote:
disconnectedradical wrote:Maybe understand the radar range equation before making such statements?


You're talking about the inverse square law for the Rmax equation, yes I'm familiar, but if you read my statement it says
the Lockheed's design completely wipes the floor in the higher frequencies
This is because in 3 out of the 4 examples given, Lockheed had better results.

But lets take the Rmax equation and say that Peak power, Antenna gain and Noise floor are all equal.

1600 = Lockheed's Rmax is 32% better
8400 = Lockheed's Rmax is 47% better
2300 = Lockheed's Rmax is 66% better
175 = Northrop's Rmax is 76 times better.

Again Lockheed's design had advantages of at least 30% on most frequencies specially on the ones more commonly used for high quality weapons tracking.


Your math is completely wrong, did you somehow miss the quarter exponent? Your numbers are literally RCS ratio, not Rmax, I don't think you're familiar at all with the radar equation.

16000, Northrop Rmax is 32% higher (Lockheed has 25% lower Rmax)
8400, Northrop Rmax is 20% higher (Lockheed has 17% lower Rmax)
2300, Northrop Rmax is 11% higher (Lockheed has 10% lower Rmax)
175, Lockheed Rmax is 296% higher (Northrop has 66% lower Rmax)

Again relationship between RCS and Rmax is quarter exponent, which you seem to completely ignore except for the first frequency.
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Unread post04 Feb 2020, 09:53

disconnectedradical wrote:Your math is completely wrong, did you somehow miss the quarter exponent?



O thats right, I reviewed the formula and recalculated, you are right I apologize.
The point I was trying to get across was, that we can't say A is better than B. Its not that simple.

But if you were thinking that I implied a 400% decrease in detection range due to a having 4x smaller RCS, then thats not what I was saying at all. But yes, my actual calculation was erroneous, I'm sorry.[/quote]
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disconnectedradical

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Unread post04 Feb 2020, 16:45

zero-one wrote:
disconnectedradical wrote:Your math is completely wrong, did you somehow miss the quarter exponent?



O thats right, I reviewed the formula and recalculated, you are right I apologize.
The point I was trying to get across was, that we can't say A is better than B. Its not that simple.

But if you were thinking that I implied a 400% decrease in detection range due to a having 4x smaller RCS, then thats not what I was saying at all. But yes, my actual calculation was erroneous, I'm sorry.


And yet Northrop's better broadband stealth won them the B-2 over Lockheed's design.

One thing not being appreciated is the political aspect. In the 1990s, Northrop had the B-2 (before the orders were cut down), and there was real worry that giving Northrop both ATB and ATF would be too many eggs in one basket, so if they have two designs that could meet requirements even if one is more optimized, they can choose another to preserve the industry. Pretty sure this is also the reason for giving Boeing F-15X now, since they want to make sure Boeing fighter division (which is really just old McDonnell Douglas after the merger) is still alive.
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Unread post05 Feb 2020, 10:07

disconnectedradical wrote:And yet Northrop's better broadband stealth won them the B-2 over Lockheed's design.


Yes but
https://aviation.stackexchange.com/ques ... -trim-drag
Lockheed was floored by this as they thought they beat them hands down in radar testing

Now as with Northrop's opinion on the YF-23, I take looser comments with a pinch of salt. I don't completely dismiss them, but I know how the human factor of frustration can kick in and cause people to exaggerate statements.


Since Northrop is already said to have better broadband stealth with their flying wing, I think Lockheed may be referring to RCS reduction on specific frequencies particularly the more dangerous higher frequencies,

I used to think that a flying wing or having the least number of protruding surfaces will always be better for Stealth, but here we have Lockheed's tailed design beating the B-2 in at least some aspects of VLO

Possibly, just as with the XST program, Northrop specializes in wide broadband stealth while the Lockheed's expertise is on smaller RCS figures at higher frequencies. Senior Peg also seems to be eerily similar to B-21's art rendering somewhat,
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Unread post05 Feb 2020, 11:57

disconnectedradical wrote:
One thing not being appreciated is the political aspect. In the 1990s, Northrop had the B-2 (before the orders were cut down),


The orders had already been cut down by 1990. Industrial base considerations are perfectly legitimate
to include in the source selection process but they have been stated upfront in the RFP.

It's highly unlikely that a program office would risk their source selection bouncing on GAO protest
due to unstated, covert industrial base considerations. ATF source selection
just had too many eyes on it (including the Navy) for that work.
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Unread post05 Feb 2020, 18:58

zero-one wrote:Possibly, just as with the XST program, Northrop specializes in wide broadband stealth while the Lockheed's expertise is on smaller RCS figures at higher frequencies. Senior Peg also seems to be eerily similar to B-21's art rendering somewhat,


Not at all, B-21 is most similar to initial B-2 design before the low altitude requirement forced Northrop to add extra serrations in the back to reduce effect of gust load, and that reduced high altitude performance. In hindsight it was a mistake and made B-2 a lot more expensive for a mission it never should do.

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Unread post06 Feb 2020, 07:14

disconnectedradical wrote:In hindsight it was a mistake and made B-2 a lot more expensive for a mission it never should do.


Laydown delivery of the B83 is about the only way the US can hold many strategic targets at risk.
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Unread post06 Feb 2020, 07:35

marauder2048 wrote:
disconnectedradical wrote:
One thing not being appreciated is the political aspect. In the 1990s, Northrop had the B-2 (before the orders were cut down),


The orders had already been cut down by 1990. Industrial base considerations are perfectly legitimate
to include in the source selection process but they have been stated upfront in the RFP.

It's highly unlikely that a program office would risk their source selection bouncing on GAO protest
due to unstated, covert industrial base considerations. ATF source selection
just had too many eyes on it (including the Navy) for that work.

This was before the cap at 20 aircraft, and with Cold War ending, giving Northrop both ATB and ATF (they also had TSSAM) would even more be seen as too much. In any case the decision to go with Lockheed was because of perception of management.
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Unread post06 Feb 2020, 08:33

disconnectedradical wrote:This was before the cap at 20 aircraft, and with Cold War ending, giving Northrop both ATB and ATF (they also had TSSAM) would even more be seen as too much.


There was already an amendment circulating in 1990 (with very strong support) to cap production at 15 aircraft.
TSSAM was similarly starting to unravel at this time.

disconnectedradical wrote:in any case the decision to go with Lockheed was because of perception of management.


Dem/Val was based on "sealed envelope" predictions of aircraft performance particularly in the risk areas.
One company demonstrated/validated more than the other while on important areas like weapons bay acoustics
the YF-23 fell down. Predictability is a matter of science. Not perception.
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Unread post06 Feb 2020, 09:48

This is from the PCA thread but I think it belongs here:
disconnectedradical wrote:Reading what Metz said in the book, it didn't seem marginal, and he said in page 59 "...the GE powered YF-23 achieved a higher top supercruise speed which remains classified but was shown publicly as "Very Fast".


I don't think the YF-22 was tested to it's absolute top speed as well. It typically takes numerous test flights to see where the actual placard limits are and all prototypes flew less than 100 hrs.

From what Metz showed on his lecture, the YF-22 was simply tested to > 2.0 Mach.
Capture3.PNG


I'm not sure why this graph has the numbers missing at the bottom, is it classified? I don't know, but it could very well be the the information Metz was basing his statements on. The margin doesn't look large judging from the pegs at the bottom
Capture4.PNG


Theres always the possibility that Northrop simply had a more aggressive approach in testing super cruise speeds while Lockheed was more aggressive in maneuverability.

I'm not as well versed as many of you here in aero engineering, but my gut feeling tells me the YF-23 was indeed faster, even though publicly available data says the margin is small. Lockheed never commented on this matter, The F-23 EMD is longer and will also experience substantial weight growth as with all production variants.

We just don't have data on it because it was never built. We know the F-22 experienced unexpected weight growth and had to reduce some of it's performance parameters, but if it was never built and the F-23 experience the same, people would be arguing on how perfect the YF-22 would have been if it won the contract.
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