Boeing Unveils New Stealthy F-15

[gf0012-aust]

Well, I was talking about the frame shape's RCS impact only - I'm sure it's true that most other aspects of the two designs will favor F-22 in this regard... But in any case, that's interesting info, thanks!

Every manned production version of LO aircraft built by the US has used different principles to manage their signatures.

Every unmanned production version of LO aircraft built by the US has used different principles to manage their signatures.

there has only been one common element in all of them and on the first deliberately built LO platform that modification realised a 90% reduction in its prev signature footprint.

you can't look at RCS on the basis of the design of the F-117 and assume that it will have superiority over latter generations because different principles of management are at play.

ie the F-117 used faceted panels. SR-71, B2, B1, JSF and F-22 all use different management solutions

 

[gf0012-aust]

Bear in mind that the F-22 is the product of more advanced technology and evolved design methods than the F-117 (in addition to the requirements of said design being different), so expecting there to be a necessary "trade-off" between performance and LO for the F-22 on the basis of characteristics inherent to the F-117 could be misleading.

There is no trade off. the F-22 can self escort ie defend itself. the F-117 had to rely on extensive mission planning, traffic management and its LO to enter the threat area and leave safely.

the F-22 doesn't need to - it can fight its way in and/or out if necessary and still has lower RCS than its predecessor..

one is a complete package - the other was evolutionary and gestational

 

[Bonza]

There is no trade off. the F-22 can self escort ie defend itself. the F-117 had to rely on extensive mission planning, traffic management and its LO to enter the threat area and leave safely.

the F-22 doesn't need to - it can fight its way in and/or out if necessary and still has lower RCS than its predecessor..

one is a complete package - the other was evolutionary and gestational

I agree completely, that's what I meant when I said an expectation of such a trade off is misleading. Just because one platform with LO characteristics loses out on performance in other areas, doesn't mean future generations will necessarily have to compromise those same performance characteristics in order to meet their own LO requirements and indeed surpass the LO attained by the previous, "low-performance" platform, and so on.

 

[LS1 Miata]

F-22 body does not minimize radar energy as efficiently as F-117 does, if you discount everything other than the frame shape (and probably overall as well), despite the computer aid. Its design is a compromise between stealth and high maneuverability, unlike that of F-117's. And as long as there are continuous curved surfaces on a plane the signature due to shape will increase with size more or less proportionately. You may have a point in the sense that the shape of F-22 is just one of many contributors to its RCS, with other factors being less or not sensitive to its overall size, so the size is not AS important, but saying that the RCS will be "largely the same" in a bigger frame is just not true.

The F-22 is not a compromise between stealth and maneuverability. And it's stealthier than the F-117. The F-22 is said to be at -40 dBsm.

 

[PhysicsMan]

There is no trade off. the F-22 can self escort ie defend itself. the F-117 had to rely on extensive mission planning, traffic management and its LO to enter the threat area and leave safely.

the F-22 doesn't need to - it can fight its way in and/or out if necessary and still has lower RCS than its predecessor..

one is a complete package - the other was evolutionary and gestational

It's not quite clear to me what the argument is about here. I'm not sure exactly what you mean by saying there's no trade off because there are numerous things that went into F-22 design that increase performance and also increase RCS, and the other way around, making it a trade off between performance and stealth. I don't think it takes much for anyone to notice that certain features in an airplane improve performance at the expense of its RCS and vice versa. Here are some examples obvious even to me:
1. The vertical stabilizers - they are tilted on F-22 - a compromise in performance, yet, if an even smaller RCS was wanted they could be modified further - they are big and they increase RCS, and one could do with much smaller ones or none at all if performance wasn't important
2. Horizontal stabilizers - big, protruding, with a signal off of them. Again, could have been more subtle if the required performance wasn't there.
3. The RAM coatings - a royal pain in the rear that compromises effective all-weather performance.
4. The highly complex engine rotor blade design/materials to minimize RCS - I'm no expert on this but I would be surprised if it didn't have a negative effect on engine performance and/or maintenance.
5. Engine nozzles. A more complex and effective thrust-directing design is possible but that would likely compromise the signature.
6. The overall shape is not exactly the most aerodynamic and maneuverable choice possible, and neither is it the stealthiest variant possible.
I may be off with some of these but I'm sure there are many more examples of design trade offs of this kind. We may drool at the sophistication of the plane all we want but it's not a "perfection", and as in any other complex engineering product there are tons of all kinds of trade offs that went into its design, not the least of which is simply the cost...

 

[Bonza]

It's not quite clear to me what the argument is about here. I'm not sure exactly what you mean by saying there's no trade off because there are numerous things that went into F-22 design that increase performance and also increase RCS, and the other way around, making it a trade off between performance and stealth. I don't think it takes much for anyone to notice that certain features in an airplane improve performance at the expense of its RCS and vice versa. Here are some examples obvious even to me:
1. The vertical stabilizers - they are tilted on F-22 - a compromise in performance, yet, if an even smaller RCS was wanted they could be modified further - they are big and they increase RCS, and one could do with much smaller ones or none at all if performance wasn't important
2. Horizontal stabilizers - big, protruding, with a signal off of them. Again, could have been more subtle if the required performance wasn't there.
3. The RAM coatings - a royal pain in the rear that compromises effective all-weather performance.
4. The highly complex engine rotor blade design/materials to minimize RCS - I'm no expert on this but I would be surprised if it didn't have a negative effect on engine performance and/or maintenance.
5. Engine nozzles. A more complex and effective thrust-directing design is possible but that would likely compromise the signature.
6. The overall shape is not exactly the most aerodynamic and maneuverable choice possible, and neither is it the stealthiest variant possible.
I may be off with some of these but I'm sure there are many more examples of design trade offs of this kind. We may drool at the sophistication of the plane all we want but it's not a "perfection", and as in any other complex engineering product there are tons of all kinds of trade offs that went into its design, not the least of which is simply the cost...

I see what you're getting at, but I think it might be overly pedantic - the point is, the aircraft excels both in low observability AND in more traditional performance parameters not associated with previous generations of LO aircraft. Concessions could be made in the design in either direction, but the end result is an extremely low observable, extremely high performance aircraft.

It's not a matter of drooling over the plane - that's pointless when discussing capability, and the F-22 isn't without its share of problems (big problems, if you look at maintenance and sustainability issues) - but the reality is the platform is an improvement on previous generations in terms of LO (F-117) and in terms of agility/performance (F-15).

 

[PhysicsMan]

I see what you're getting at, but I think it might be overly pedantic - the point is, the aircraft excels both in low observability AND in more traditional performance parameters not associated with previous generations of LO aircraft. Concessions could be made in the design in either direction, but the end result is an extremely low observable, extremely high performance aircraft.

It's not a matter of drooling over the plane - that's pointless when discussing capability, and the F-22 isn't without its share of problems (big problems, if you look at maintenance and sustainability issues) - but the reality is the platform is an improvement on previous generations in terms of LO (F-117) and in terms of agility/performance (F-15).

I agree with that. The only reason I brought up the comparison between F-117 and F-22 LO signatures is because of the statement made earlier that their RCSs will scale similarly with size, or rather will not change much at all if one were to change their size. My argument was aimed at that, saying that it may be more or less the case for F-117 with its faceted shape but not so with F-22 or any other smoothly curved plane.

 

[Crusader2000]

Actually, F-117 probably does have a smaller RCS...

I believe the RCS of the F-117 is larger than either the F-35 or B-2. Of course the former is older technology......

 

[SpudmanWP]

It goes F-117 > B-2 > F-35 > F-22

 

[Crusader2000]

It goes F-117 > B-2 > F-35 > F-22

I thought the RCS of the F-35 and B-2 where approximately the same???

 

[PhysicsMan]

I thought the RCS of the F-35 and B-2 where approximately the same???

How do you guys get this info? It's not exactly out there...

 

[SpudmanWP]

Yes, it is out there and was publicly stated as such.

Nov 2005: The U.S. Air Force, in it’s effort to get money to build more F-22s, has revealed just how “stealthy” the F-22 is. It’s RCS (Radar Cross Section) is the equivalent, for a radar, to a metal marble. The less stealthy (and much cheaper) F-35, is equal to a metal golf ball. The F-35 stealthiness is a bit better than the B-2 bomber, which, in turn, was twice as good as that on the even older F-117. Much older aircraft, like the B-52, have a huge RCS, which makes them very easy to spot on radar. But with a smaller RCS, it's more likely that the aircraft won't be detected at all.

The air force revealed this information, which is usually kept secret, because it wants to make the case that it makes more sense to cut production of the F-35 (which cost $30-50 million each), so that more F-22s (that cost over $100 million each) can be bought. Most of the air force generals are former fighter pilots, and the F-22 is a much hotter fighter than the F-35 (which is basically a fighter-bomber, with emphasis on the latter function.) This is causing an international uproar, because of the many foreign countries that are buying the F-35. Some of these countries have contributed money for the development of the F-35. The F-22 will not be exported, because it uses so much top secret technology.

Warplanes: F-22 Stealth Ability Revealed by USAF

Still looking for the original source.

 

[PhysicsMan]

Yes, it is out there and was publicly stated as such.



Warplanes: F-22 Stealth Ability Revealed by USAF

Still looking for the original source.

Thanks for the link May be a bit of a PR thing but still interesting...

 

[gf0012-aust]

Thanks for the link May be a bit of a PR thing but still interesting...

Its hardly PR, we are getting more than anecdotal evidence from pilots going up against them in exercises.

hence my frustration with proof of life claims based on the internet.

besides, from a capability perspective, it is completely irrelevant what we see on the internet. the data is made available via exchange pilots and through shared channels.

people on the internet can argue as much as they like, it doesn't impact on the actual warfighting community

 

[gf0012-aust]

I agree with that. The only reason I brought up the comparison between F-117 and F-22 LO signatures is because of the statement made earlier that their RCSs will scale similarly with size or rather will not change much at all if one were to change their size. My argument was aimed at that, saying that it may be more or less the case for F-117 with its,

they don't. for the unmpteenth time, there is no exponential scalability on a platform in signature management. It does NOT work like that.

. My argument was aimed at that, saying that it may be more or less the case for F-117 with its faceted shape but not so with F-22 or any other smoothly curved plane.

again, what is the relevance in trying to extrapolate one (and earlier) generation of sig management which uses completely different concepts to another - when its been quite clearly indicated by exchange pilots that the latter is far harder to acquire both visually and electronically even when WVR.??

its got nothing to do with facets vs curves. its about technology relativity and design intent. it is an iterational if not spiral development issue.

seriously. this is going around in circles.

 

[gf0012-aust]

It's not quite clear to me what the argument is about here. I'm not sure exactly what you mean by saying there's no trade off because there are numerous things that went into F-22 design that increase performance and also increase RCS, and the other way around, making it a trade off between performance and stealth. I don't think it takes much for anyone to notice that certain features in an airplane improve performance at the expense of its RCS and vice versa. Here are some examples obvious even to me:

again, the increase in RCS is nonsense. repeating yourself and ignoring what is being patiently explained is not going to further the argument - and I'm starting to question your technical competency when the issue has been explained ad nauseum

1. The vertical stabilizers - they are tilted on F-22 - a compromise in performance, yet, if an even smaller RCS was wanted they could be modified further - they are big and they increase RCS, and one could do with much smaller ones or none at all if performance wasn't important

rubbish. its a st george cross design - its exactly the same reason why that design on subs outperforms the traditional celtic cross design.

2. Horizontal stabilizers - big, protruding, with a signal off of them. Again, could have been more subtle if the required performance wasn't there.

and the evidence of that is where? I'm curious as to what credible references you can cite when all of the electronic warfare and sig management evidence points to other factors.

3. The RAM coatings - a royal pain in the rear that compromises effective all-weather performance.

rubbish. it does not. RAM management for the B2 was changed 3 years ago. the F-22 uses different technology - where's the empirical evidence when the processes were changed years ago?

4. The highly complex engine rotor blade design/materials to minimize RCS - I'm no expert on this but I would be surprised if it didn't have a negative effect on engine performance and/or maintenance.

how and where? exposed blades have not been evident in any LO aircraft since 1958. there is a reason why shock ramps exist.

5. Engine nozzles. A more complex and effective thrust-directing design is possible but that would likely compromise the signature.

why have complex designs when the functional spec requires the aircraft to have other capabilities. what good is 3D thrust against a missile with tri-seekers, a narrow NEZ and a higher mach speed, and in some instances, TVC on the missile.

6. The overall shape is not exactly the most aerodynamic and maneuverable choice possible, and neither is it the stealthiest variant possible.

what? your info is again based on what? exchange pilots have already said that when in WVR they cannot get into the kill zone. there will always be exceptions., the plane is not invincible. human factors always count at some point - but aircraft like the F-16 up have higher systems override and mgt for a reason.

I may be off with some of these but I'm sure there are many more examples of design trade offs of this kind. We may drool at the sophistication of the plane all we want but it's not a "perfection", and as in any other complex engineering product there are tons of all kinds of trade offs that went into its design, not the least of which is simply the cost...

what is your actual engineering background here - as you are making some claims that I would not expect of an engineer - and I work with a variety of them on a number of weapons and systems projects.

 

[gf0012-aust]

I have some fundamental concerns about the direction and tone of this thread.

It needs to get back on track - and like all other threads there is an expectation that claims made can be either supported or argued coherently.

Its getting locked for a few days while the Mods go into discussion about its progress to date.

 

[Preceptor]

Thread re-opened. Having had issues within the thread previously, discussion will be monitored to ensure that it follows forum rules.
-Preceptor

 

[OPSSG]

Boeing Looks To First Silent Eagle Flight

Jan 16, 2010 - With radar-cross-section (RCS) trials for Boeing’s Silent Eagle semi-stealthy F-15 prototype complete, company officials are now focusing on South Korea as a possible first customer. The RCS testing took place during a two-week period last August and September, although Boeing has only just acknowledged it because of proprietary issues, says Mark Bass, vice president of F-15 programs.

The company is eyeing South Korea’s forthcoming F-X3 competition for 60 fighters as the first sales opportunity for the Silent Eagle. The South Korean parliament’s recent hesitancy about investing in all-stealth aircraft “validates our approach” with the aircraft, says Bass. The company is considering potential international co-development partners for a Silent Eagle conformal fuel tank, although no announcements have been made. Boeing is developing the variant for international customers that already operate F-15s and are seeking additional aircraft. The system is a possible alternative for nations interested in the Lockheed Martin F-35 Joint Strike Fighter. The Silent Eagle is not as stealthy as the JSF, but it could provide flexibility for countries trying to stretch their defense dollars...

The RCS tests on F-15E1, an Air Force test asset leased to Boeing, took place at the company’s anechoic chamber in St. Louis. Various coatings were evaluated and a final candidate has been selected and applied to the appropriate portions of the airframe...

The RCS testing took place with the standard vertical fins on the F-15, not the 15-deg. canted structures unveiled last year by Boeing. Data needed about an optional canted tail can be gathered mathematically, Bass says. The RCS testing is a step leading toward first flight, which is slated for late July...

Following first flight, the focus will shift to demonstrating the ability of the conformal tank to safely deploy an Advanced Medium-Range Air-to-Air Missile. The test is slated to be conducted at roughly 20,000 ft. at Mach 0.6, a benign scenario for the first shot. This demonstration will likely occur in July or early August, says Bass. In the meantime, Boeing has applied for an export license and expects a ruling this spring...

South Korea is expected to issue a request for proposals by early 2011 for new fighters. At a later date, Saudi Arabia may accept solicitations to replace up to 80 early model F-15s, says Bass. Singapore is also a possible customer. Boeing has cited a rough cost for Silent Eagle of $100 million per aircraft, although that would depend on factors such as co-development plans that have not yet been established.

More Boeing news...

 

[bruceedwards]

More Boeing news...

$100 million each - that sounds dangerously close to the per aircraft cost of the F-35.

Obviously the advantages Boeing will be pushing are quicker access to the airframe (rather than waiting up to a decade for an F-35, you can get this in just X years!) and lower maintenance.

However, the last figure I heard for the F-35 was $35 million per airframe. That's a significant difference, however I've *also* read that the flyaway cost for an F-35 is $83 million (here: http://www.saffm.hq.af.mil/shared/media/document/AFD-080204-081.pdf).

Is anyone aware of the projected maintenance costs of the F-35? Given their planned international reach, and commonality of parts and systems, I imagine the F-35 could well be more cost effective to maintain than a 'stealthified' F-15, but I have no figures to back up this assumption.