Drawing credit listed below (1)
What jumps out? It’s
that the two are virtually identical !
Be honest now … without labels, how many of you can tell the two apart?
What does this tell us about their relative stealth? Well, it suggests that the frontal stealth of
the two airframes may not be all that much different. Of course, there is more to stealth than just
the shape although the F-35 claims to not use much in the way of exotic
coatings to enhance stealth which suggests that shape is the F-35’s main source
of stealth. There may be materials of
construction or internal shaping that also contributes to stealth but, if so,
I’ve never seen a detailed listing or description of what degree of stealth
they contribute. No one who knows what
the differences are is talking but this suggests they are far less than F-35
proponents claim, at least from the front which is the most important aspect
since it’s the head-on, approaching profile that enemy radars will be seeing
most of the time.
The biggest frontal aspect difference between the two
aircraft is the external, pylon-hung weapons and fuel tanks on the Hornet. Again, no one knows impact those have on the
overall stealth. Do they increase the
Hornet’s radar cross section by 10%?
50%? 700%? Again, anyone who knows, isn’t saying.
My takeaway from this visual comparison is that the two
airframes are likely pretty close in frontal aspect stealth with the Hornet
losing stealth as pylons/weapons are added.
Don’t get too wound up about this. It’s not meant to be much more than an
interesting observation.
(1)Drawing prepared and presented by username=payload, 02
Aug 2015, 21:53,
http://www.f-16.net/forum/viewtopic.php?f=22&t=15013&start=240
Very small differences can have very large impacts, the most visible part on the A10 was the blades inside the turbine, not the giant engine cowling they were inside, the tiny blade.
ReplyDeleteThe biggest return on a destroyer was the guard rail on deck, ect ect.
Without putting both in a room and shooting radar at them we'll never know.
The "stealth is dead" memes look a bit silly now though😉
Very interesting as you say
Heck, one of the RCS reduction measures on the Super Hornet, that nobody ever sees, is the engine intake mesh - it's a small thing that nobody ever thinks about, but it does have an effect.
DeleteIt's a little counterintuitive, but you'd get a better idea of the frontal aspect of both aircraft with a top-down view, because then you can see the different contouring between each aircraft; a lot of the details and shapes are lost in a frontal aspect view.
This little post purports to prove nothing. Just an interesting observation and something to think about. Presumably, whatever materials and blade arrangements/location that the F-35 uses could be reasonably duplicated in the F-18.
Delete"The "stealth is dead" memes look a bit silly now though"
DeleteIndeed? Why is that?
"Presumably, whatever materials and blade arrangements/location that the F-35 uses could be reasonably duplicated in the F-18."
Delete@ComNavOps: To a certain extent it's already being done elsewhere: the USAF is incorporating and leveraging research that went into the F-35's RAM coatings.
https://theaviationist.com/2018/01/29/check-out-this-f-16c-from-nellis-air-force-bases-aggressor-squadron-wearing-the-have-glass-v-paint-scheme/
Basically, the USAF starting to abandon the old two-tone gray for this new dark gray RAM paint (at least for SEAD-tasked squadrons): very little has been said about how exactly the paint works, only that it's speculated to have microscopic metal particles to break up the radar signal.
Essentially the F-35's stealth measures boil down to several components:
- VLO shaping of the airframe
- internal weapons carriage
- RAM coatings
- Sophisticated ECM suite
Conceptually, theoretically the fastest, easiest thing to do would be to ring up the Air Force and get them to make some extra Have Glass V paint and send it the Navy's way, and then work on replacing the F/A-18F's ECM suite with that of the F-35 (although there are serious questions if it'll fit/work and whether there's space to fit it in). You can't do much about the airframe shape and weapons carriage, but Have Glass V is still an RCS reduction and AN/ASQ-239 is a legitimate upgrade in survivability.
WRT to ECM: Yeah, it's not what most people immediately think of when it comes to stealth, but modern systems like AN/ASQ-239 or SPECTRA in deception mode can tai chi enemy radar beams away, using their emissions to dissipate and weaken the strength of the opponent's radar beams, meaning that he gets a weaker strength return signal, and that's before his weakened radar signal hits the VLO shaping and RAM coatings on the airframe.
Delete"Presumably, whatever materials and blade arrangements/location that the F-35 uses could be reasonably duplicated in the F-18."
DeleteWell, yes and no.
Moving or covering an engine can be done, at a price, financial or performance, or both.
Coatings can be adapted, but at best, thats just going to carry on the same problems the F35 has with them, at best.
""The "stealth is dead" memes look a bit silly now though"
Indeed? Why is that?"
Because every platform needs as much stealth as possible and its not a binary choice
"stealth is dead"
DeleteStealth is certainly not dead. In fact, it is the minimum price of admission to the aerial battlefield. The meme is that stealth no longer provides the advantage it once did. When two stealth aircraft battle, neither has an advantage. When various sensors can now detect stealth aircraft, the stealth aircraft no longer has the advantage it once did.
The meme is that stealth no longer confers the advantage it once did and that's hardly silly. We're pouring a ton of effort and money into stealth that no long confers an advantage. It's simply the minimum requirement to have any chance at success. It's like retractable landing gear. Once upon a time, that provided an advantage but now every aircraft has it and none gain any advantage because of it. It's simply become a minimal standard.
"Be honest now … without labels, how many of you can tell the two apart?"
ReplyDelete*raises hand* I can, but then, if you're observant and you know what you're looking for, you can spot the differences. The main thing is that head on, the Rhino has a "flatter" fuselage and distinct canopy, while the F-35's fuselage is more angled and blends its shape leading to the canopy. The shape of the intakes also are distinctly different from the Rhino's rectangular intakes (strictly speaking it's more of a rhombus), and in general from a head on view the F-35 is more angled where the F/A-18E is straight.
Basically, if you're comparing photos of the two aircraft, it's a different matter: the differences are more stark, more noticeable, but then that's just how it is: line drawings lose a certain amount of nuance that a photo has.
DeleteAside from describing what everyone can see in any of a million photos, do you have anything in the way of analysis to offer?
DeleteThe two images are quite different. As you can see the air intake is in front of the wing on the f35 and the outer edge forms a chine which forms the wing. This is a significant stealthy feature the f18 on the left does not have. The air intake is below the wing which increases the exposure over a much greater arc from below as well as creating corner reflectors. Most really stealthy bomber aircraft tend to put the intake as well as the jet exhaust on the topside so that it hides it from most ground radar in level flight. Remember that because the earth is curved and most stealth aircraft travel at high altitude, an aircraft in level flight is actually at a significant angle to the detecting radar, therefore frontal comparisons like this are not that helpful. The aim is to present a flat face with no corner refectors at the bottom of the aircraft. You should be comparing the images from just below the front of the aircraft looking up a valid comparison.
DeleteGiven that even fastener design can have substantial effects on RCS, it's a fools errand to try to judge RCS from photos beyond a certain point. I think what this comparison proves is that we need a single-engined F-18H/I that shares the F-35's F-135 or follow-on adaptive engine to function as lower-cost platform to augment the F-35s while easing sustainment and logistics.
ReplyDeleteOnly analysis I have seen on F-35 stealth shaping and what not comes from Air Power Australia think tank which lobbied for F-22s for Australia.
ReplyDeletehttp://www.ausairpower.net/APA-2009-01-Annex.html#mozTocId787784
http://www.ausairpower.net/APA-2009-01.html
Nice description although I can't assess the degree of accuracy. Would have been informative to see the exact same diagrams and analysis of, say, an F-18 or the F-22.
Delete"My takeaway from this visual comparison is that the two airframes are likely pretty close in frontal aspect stealth with the Hornet losing stealth as pylons/weapons are added."
ReplyDeleteI disagree- there's a world of difference between the two from the frontal aspect.
Sometimes it's not that evident from a frontal comparison; it can come down to the "little things" that add up when it comes to RCS.
The biggest difference is that you can see the compressor blades on the engines of the Super Hornet. That's a nice, flat-ish surface perpendicular to the direction of travel that results in a bigger radar return in something called "engine front face scattering." Here's a picture of the engine being easily visible from the frontal aspect:
https://upload.wikimedia.org/wikipedia/commons/7/79/Boeing_F-A-18F_Super_Hornet%2C_United_States_-_US_Navy_%28USN%29_JP7509785.jpg
The Navy has made alterations to try to minimize the impact that the engine has on RCS, but they can't prevent it from contributing.
In contrast, the F-35 and F-22 were designed from the start such that that there are no frontal aspects where the engine is visible. The engine is hidden by the rest of the RAM-coated fuselage from radar.
RCS on the Super Hornet is something that the Navy is acutely aware of (see the Super Hornet NATOPs - it is available online). The Navy has incorporated some technologies to improve the RCS of the jet:
* Some blended and smoothed surfaces where possible.
* Application of RAM on aircraft features where feasible.
* Modified inlet ducts to try to reduce compressor blade RCS
Even with all that, the Super Hornet is just an evolution of a 70s-era airframe, and there's only so much you can do to get those "little things" to add up. To go back to my compressor example: Unless you radically redesign the aft end of the Super Hornet or do something funky with the inlets, the compressor blades will be visible and will provide a stronger radar return.
Making radical design modifications have their own costs- both in money and airframe performance.
I suspect that's why the upcoming Block 3 Super Hornets will have only modest RCS improvements and will instead focus on other capabilities, most notably additional range and avionics upgrades.
You're quite correct about blade visibility. My question is what is the actual impact? No one seems to know - probably understandable. Does the blade issue increase frontal RCS by 5%? 50%? 5,000,000%? The point is that the blade issue is real but it may have little practical impact - or, it may be hugely significant. Do you have any reference to actual data?
DeleteIf you're aiming for an RCS the size of a golf ball (0.0015m2), fan blades, fasteners, panel joints, edge misalignment, corner reflectors from strakes and intake designs all contribute a lot (each potentially much greater than a golf ball).
DeleteAdd on pylons and external munitions and you have no chance.
Yes, every little bit helps. The question is to what extent? Should we totally redesign the Hornet to hide the blades or do they increase the RCS by 1% and, therefore, are not worth much attention in an existing, older airframe?
DeleteUnderstand, no one is disputing that blades may have an effect. The question is, how much? I don't blame you for not knowing. No one in the general public knows and, as I said, anyone who does know isn't saying.
The larger point related to the post is that without such detailed knowledge, condemning the Hornet's frontal stealth just because its blades are showing is unfounded. It may be true but we don't know. It might also be that, yes, the blades decrease the Hornet's stealth but only fractionally and the frontal stealth of the two aircraft are not that far apart. Again, we don't know.
Feel free to speculate about the relative stealth of the two aircraft. I don't mind speculation as long as it's not presented as fact.
The clean, frontal RCS of a Super Hornet is reportedly in the 0.1-1m2 region.
DeleteThe clean, frontal RCS of an F-35 is reportedly in the 0.0015m2 region.
If true, that's two to three orders of magnitude of difference.
No Super Hornets fly combat missions clean, so, if you believe the reporting, the difference is actually larger.
Those two to three orders of magnitude, if true, translate to huge differences in detection ranges. An S-400 might detect a clean Super Hornet at 100-150nmi, but only detect an F-35 at 30-40nmi.
If you choose to believe the reporting.
If you don't, well,.. ¯\_(ツ)_/¯
"If you choose to believe the reporting."
DeleteI don't believe the actual numbers because I don't believe anyone in the public domain has that kind of data - I'm sure the real data is classified - but I do believe the F-35 is stealthier than the F-18 - so, a disbelief that borders on irrelevant.
The larger question is what practical impact the stealth levels have. Here's an analogous example. Ship A has 10 'power' units of propulsion compared to Ship B which has 100. Wow! Ship B must be an order of magnitude faster! Well, no. As you know, beyond 10 kts, ship propulsion hits a region of diminishing returns in speed for power increases. Thus, the order of magnitude increase in power produces little practical increase in speed. The obvious question, then, is what is the practical difference between an RCS of a golf ball vs an RCS of a marble (or whatever)? If one can be detected at 100 miles and the other at 90, that's not really a practical difference.
So, I'm sure there is a difference in frontal stealth between the two aircraft. What I'm unsure about is whether there's a practical, significant difference between the two.
"Those two to three orders of magnitude, if true, translate to huge differences in detection ranges. An S-400 might detect a clean Super Hornet at 100-150nmi, but only detect an F-35 at 30-40nmi."
Unless you have access to classified data (and data from the Russians!) you're engaged in pure speculation. Nothing wrong with that as long as you make it clear that it is speculation. You used the word 'might' so I assume you're engaged in speculation. Therefore, equally, the detection ranges 'might' be 100-150 nm vs 90-120 nm, right?
This link (posted by another Anon) spells out essentially what I said.
Deletehttps://aviationweek.com/site-files/aviationweek.com/files/uploads/2017/12/12/State%20of%20Stealth%20FINAL%20121317.pdf
Their estimate for Super Hornet forward sector stealth is 0.66-1.26m2, mine was 0.1-1m2 - pretty close guess. Their "golfball" is slightly smaller than mine, but same order of magnitude. As is their resulting radar range difference.
Their S-400 engagement ranges are 100-145mi (87nmi-126nmi) for 4.5 Gen fighters like the SH, and 21mi (18nmi) for the F-35.
I estimated the S-400 detection range, which uses a different radar, but similar orders of magnitude for both.
So it's not just my speculation, it's industry-wide reporting.
"Their estimate for Super Hornet forward sector stealth is 0.66-1.26m2, mine was 0.1-1m2 - pretty close guess. "
DeleteThe data you cite is meaningless for multiple reasons.
1. Stealth is not a constant for a given aircraft. It is a continuous function of incident angle of the radar, aspect of the aircraft, and a host of other factors. There's no such thing as a constant RCS. Without very specific descriptions of the conditions under which the cited RCS is obtained, the number is meaningless.
2. The data cited is a very precise calculation of a very imprecise comparative description of the subject aircraft's stealth. Here's the exact quote from the article:
"The F-35 RCS is compared to a “golf ball”"
They then calculate the area of a golf ball to get a supposed RCS. That's about as imprecise as it gets!
Again, I'm not disputing that a difference exists between an F-35 and an F-18. I'm stating that there are no actual data in the public domain and yet people latch on to numbers that seem very precise but, at their root, are just vague, comparative descriptions! The article you referenced clearly proved that and I thank you for helping me demonstrate that.
I've also pointed out that because a numerical difference exists do no, necessarily, mean that a practical difference exists and I've provided a real world example of that phenomenon. No one who's speaking in the public domain knows what degree of difference translates to a practical difference. You might want to review this post:
"Stealth and Mission Accomplishment"
"So it's not just my speculation, it's industry-wide reporting."
It's crystal clear that there is also industry-wide lack of understanding of the subject matter!
"If you choose to believe the reporting.
DeleteIf you don't, well,.. ¯\_(ツ)_/¯"
The following quotes (see, Stealth demonstrate the confusion and contradiction that exist around stealth discussions.
In the following quote, note that the F-35 is claimed to be MORE stealthy than the F-22.
"During a flight debriefing, Col. Chris Niemi and Maj. Nash Vickers both said a comparison of the radar-absorbing F-35 to its nimble but less stealthy twin-engine F-22 cousin might not reveal the whole story."
Contradicting that statement, consider this one that states the exact opposite.
"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."
Now, here's a quote that is vague and ambiguous about the F-22 vs the F-35.
"On a radar map, a 747 would appear the size of a hot air balloon and an F-16 would look like a beach ball. Drill down to legacy stealth aircraft and Lockheed’s F-117 Nighthawk would show up as a golf ball while an F-22 Raptor might appear as a pea. With the F-35, Lockheed is getting down to pebble size, according to Robert Wallace, senior manager for F-35 flight operations."
So, a pea and a pebble. How big is each and which is bigger? This is what passes for data in the public domain. Note that the F-117 is described as a golf ball as is the F-18. Taken at face value, that would make the F-18 equivalent in stealth to an F-117. Is that true? I have no idea.
Its better to use radii cross section than an object. The comparisons are made are againt idelised metal sphere. The f18e has a radio cross section of 0.5m sqr the grippen is 0.1m sqr. The f35 is reported to be 0.002 m squared or about 500 times less than the superhornet.
DeleteDoes it make a practical difference? The answer is clearly yes. A f35 can sit about 50km from a fleet of ships and not be seen. It than uses its aesa radar to send low probability messages back to other non stealthy platforms such as the hornet that then release lrasm to target the targets. Remember the pantsir that was blown up by the israelis in the middle of damascus. It was destroyed by an f35i unseen.
As the radar detection range is the 4th route of the ratio of the radio cross sections one can quickly compare the detection ranges of aircraft. If an f18 is detected at 100km, a f35 will be detected at 20km by the same radar for a ratio of 500.
Delete"The f18e has a radio cross section of 0.5m sqr the grippen is 0.1m sqr. The f35 is reported to be 0.002 m squared"
DeletePlease cite a source for your numbers as I don't believe they're actual data.
Strategy page november 20 2005. Grippen by swedish government.
DeleteWhat is that? Give me a link or reference.
DeleteIn terms of pea,pebble, golf ball. Base ball soccer ball beach ball etc. The reason these are used is that they are idealised metal spheres by which a standard curve can be made.
DeleteLets say you are measuring the rcs of an object. You measure these items to make the standard curve. You then measure the item and plot it against this curve. This allows you to compare results conducted by different radars at different locations.
If you read enough technical radar papers it explains how the measurement is performed.
As the detectibility partially depends on the frequency of the radar and thus the rcs changes with frequency, it is just easier to report the object it is closest to rather than report a rcs which changes markedly with frequency. They have to dumb it down so they can report to Congress etc.
Gold. The F35 has a sheet of gold in the glass which prevents cockpit radar returns. The pilots seat used to be a "reflector".
ReplyDeleteIts also on the Cirrus Vision jet. You don't need sun shades on the inside of windows on tarmac, very little heat comes through.
That would seem a pretty simple change for the F-18 if it hasn't already been done.
DeleteDidn't the EA-6B have that?
DeleteIt did, but that was for electromagnetic shielding of the avionics from the onboard jammers.
DeleteThe turbine blades are also obscured by the fuselage on the Cirrus if AOA is adjusted. Cheap 2.2 mill stealth. Buy a hundred and use them as disposables.
ReplyDeleteEvery aircraft's blades are hidden if you make the AOA high enough!
DeleteThis may be of interest : https://defence.pk/pdf/threads/rcs-of-the-f-35-vs-f-22.581900/
ReplyDeleteI discourage links with no value added. What is of interest about it?
DeleteIt reported that a person involved in the Canadian military with access to detailed info had placed the RCS of a F-35 at 1/20th the RCS of the CF-18 at 0.5m2. I'm assuming that the F/A-18E, though bigger, has a better RCS than the CF-18.
DeleteIf you are correct about the rcs then the detection range of the f35 is 40% that of the cf-18
DeleteBuried in the page is an interesting link from Aviation Week Special Report
ReplyDeleteThe State of Stealth
https://aviationweek.com/site-files/aviationweek.com/files/uploads/2017/12/12/State%20of%20Stealth%20FINAL%20121317.pdf
Navy began the Sixth/Next Generation Air Dominance AOA back in May 2016 to determine what aircraft would follow the F/A-18E/F Super Hornets and EA-18G Growlers, which are scheduled to retire in the 2030s, with report expected this summer.
ReplyDeleteNavy looking at manned and unmanned aircraft with varying stealth characteristics, advanced standoff weapons, sensors, networks and powered by the new gen advanced jet engine, same size as F135, under development by GE AND PW targeting 20% higher thrust, improve fuel consumption by 25% to extend range by 30%+, and provide significantly more aircraft heat dissipation capacity.
Must say I'm confused how Navy talk of air dominance and F-18 in same breath, F-18 and F-35 are basically Mach 1.6 attack/bomb trucks, the F-14 was a Mach 2.3 air dominance/air superiority fighter with its large radar.
"and unmanned aircraft"
ReplyDeleteWhich still fact a leap of faith that it will work in a contested environment. The persistent rumor that the air farce had to un mothball the f-117 for Syria because of Russian jamming (the f-117 being the only thing designed to fly all by itself with on board navigation and aim itself)does not make me feel warm and fuzzy about how a fleet of drones or robots will turn out. If the shit really hits the fan I think having the meatware on board and on board backups for targeting and navigating are essential. Floating about in backwaters for the forever war on global on terror might be useful and cheap but I still would rather have more F-222s while we wait for the 6 gen plain(s).
" the air farce had to un mothball the f-117 for Syria"
DeleteThat's a new one on me. Where did you hear that?
Probably a dumb question, but why haven't we redesigned the weapon pylons and at least a2g ordnance to have stealth from the front? Seeing as most everything is guided now, even with a less the optimal aerodynamic profile, we would still have a good accuracy.
ReplyDelete"What does this tell us about their relative stealth? Well, it suggests that the frontal stealth of the two airframes may not be all that much different."
ReplyDeleteI think there is more to the shape of the two airframes than the figure suggests. The RCS of a sphere is lower than that of a flat plate. The F-35 fuselage bulges out some midway up from the bottom of the fuselage giving it a somewhat "spherical" shape when viewed head on. And, the cockpit blends with the upper fuselage. I think these features contribute to the lower RCS of the F-35.
Two other observations about the F-35. First, there appears to be "bulge" just inside the inlet which might cause some of the radar energy to bounce off the sides of the engine inlet duct. Second, bottom of the engine inlets are curved slightly upward which might direct some radar energy downward and away from the aircraft.
DeleteThe bump in the intake, is a diverterless supersonic inlet. Look at the splitter plate on a F-4, the bump
Deleteyou see in F-35 inlet is a different way to slow the air airflow. Splitter plates make lovely corner reflectors.
Back on topic.
I put in a FOI with PLAAF for RCS numbers the F-35 and F-18, I'll let you know what I get back. ;-)
Unlike most other aircraft, the F-35 inlets are canted forward. I wonder if the bump in the intake has a secondary purpose of redirecting radar energy to the outer edge of the engine inlet which deflects or absorbs that energy.
DeleteI'm not an F-35 supporter. The program should have been cancelled years ago, and still should be, with perhaps ongoing funding of some of the aircraft's useful technologies (the engine in particular is excellent).
ReplyDeleteThat said, it is considerably stealthier than the F/A-18. The most obvious aspect of this is that the F/A-18's turbine blades are exposed (if meshed), whereas the F-35's fan is not. This cannot be duplicated on the F/A-18 because it is a twin-engine design. The F-22 (and canceled YF-23) has complex, serpentine ducts to shroud the turbine blades. The Russian Su-57 also has exposed turbine blades. The Su-57 is more appropriately a stealth-hunting fighter rather than a stealth fighter, so the Russians accepted the tradeoff of reduced stealth in exchange for increased performance (supermaneuverability, L-band cheek radars).
The F-35 also clearly has stealth shaping throughout the frontal area which the F/A-18 does not. Note the sawtooth edges on all doors, the sharp angles, and angles that match throughout the airframe. This can't be duplicated on the F/A-18 since it would ultimately be a new airframe.
The best online resource for this is Carlo Kopp's website Airpower Australia. Unfortunately it is no longer updated, perhaps because Kopp failed in his mission. He wanted to stop Australia from acquiring the F-13, keep the F-111s in service, and acquire the F-22. The website however still has an excellent wealth of knowledge.
http://www.ausairpower.net/jsf.html
Some stealth features could be added to the F/A-18 of course. Boeing has obviously been thinking about this with its F-15 "Silent Eagle" proposal.
Personally I think the Navy should acquire and Americanize the French Rafale. It's a superior design to the F/A-18 and available now. Selecting a foreign design would send a useful message to America's gold bricking defense contractors.
This would only be an interim measure of course. Ultimately new aircraft are required (and not just fighters).
"it is considerably stealthier than the F/A-18"
DeleteThis is what I have a problem with. "Considerably stealthier". Is it? And if it is, how much is "considerably"?
I don't doubt that the F-35 is stealthier. How much is the question. 1%? 50%? 5,000,000%? No one knows. People latch on to things and then make grand, sweeping statements. Sure, from what we know, exposed turbine blades degrade stealth but how much? If they add 1% to the RCS, that's insignificant. If they double the RCS, that's significant. No one knows. I've never seen any data on the subject.
The 'data' that I've found, when traced back to its roots, inevitably stems from some vague, descriptive statement like the aircraft has a RCS the size of a 'golf ball' or 'pebble'. Then, someone calculates the area of a golf ball or pebble and the resulting number gets reported as the RCS and repeated until it becomes an exact RCS measurement. As you know, the reality is that RCS is not a constant. It's a continuously varying function of aspect angle, incident radiation angle, frequency, and a host of other factors. Anyone who pronounces that the F-whatever has an RCS of xxx clearly doesn't understand how stealth works. An RCS is valid only for a single, very specific set of conditions out of an infinite number of possible condition sets.
While I'm occasionally guilty of making them, I abhor generic statements. I absolutely don't know that the F-35 is 'considerably' stealthier than an F-18 because I've never seen actual data generated from identical sets of conditions for the two aircraft - and neither has anyone else. So, the F-35 MAY be 'considerably' stealthier or it may be 'somewhat' stealthier or it may be 'slightly' stealthier, whatever any of those descriptors mean, but we don't have any data to base the assessment on. If you have actual data, please share it!
It's obvious enough by looking at it. The F-35, in common with other aircraft designed for reduced radar cross-section, employs extensive orthogonal angular shaping with dihedrals and trihedrals, particularly in the frontal area. Unlike the more advanced F-22 this is not employed in the rear area and is less employed in the lower area. Note also that many of the angles are the same so as to reflect radar energy into specific directions instead of diffuse directions better picked up by radar receivers.
DeleteYes, "considerably" is not very descriptive. Likewise statements given by industry lobbyists like "RCS the size of a golf ball" aren't helpful since that doesn't tell us what the RCS is from a particular direction or for which radar wavelengths (mostly X-band).
Then there's the complicating factor of materials. Airframe shape is known to any observer and subject to mathematical analysis. I'm sure this analysis has already been done on the F-35 by all technologically competent air forces and various competing manufacturers. But material properties can't be known without having the materials in hand, and even then the performance of the materials will change in service owing to degradation.
Copp's take on the F-35's stealth: http://www.ausairpower.net/APA-2009-01.html
http://www.ausairpower.net/XIMG/JSF-RCS-Qualitative-A-XLVHF.png
Study of the shaping of the aircraft and comparison with other designs shows that the Joint Strike Fighter can provide genuinely good stealth performance only in a fairly narrow ~29° sector about the aircraft’s nose, where the shaping of the nose, engine inlets, panel edge serrations, and alignment of the leading and trailing edges of the wings and stabilators results in the absence of major lobes or “spikes” in the radar signature.
I'm comfortable stating "considerably" because the F-35 was observable designed with RCS-reduction shaping techniques, whereas the F/A-18 employs none other than the canted vertical stabilizers (which were canted in order to increase stability at high AOA, not for stealth).
The F-35 seems to generally be presented to the public (and policymakers) as being a "stealth" design, which isn't really true. It's stealthy in a very limited area to facilitate forward penetration only.
"If you have actual data, please share it!"
ReplyDeleteSo you're asking people to shared data that is or *should* be proprietary/classified?" But issue statements like this:
"If they add 1% to the RCS, that's insignificant. If they double the RCS, that's significant. "
That's a fundamentally wrong statement with respect to stealth. The degree of RCS reduction isn't significant, the EFFECT is. If a "1%" RCS reduction prevents a KUa or KUb band seeker from targeting me, it's significant, even if an X-band or S-band radar can see me.
"The degree of RCS reduction isn't significant, the EFFECT is."
DeleteAbsolutely!!!! Could not agree more. Unfortunately, if you think we have nothing in the way of RCS data, we have even less (than nothing?) in the way of what the effects are. I've already addressed this (see, Stealth and Mission Accomplishment
"So you're asking people to shared data that is or *should* be proprietary/classified?" "
I know no one has actual data and anyone who does isn't going to share it. It's simply a way to emphatically remind people that no one has actual data. It's also a way of telling people to stop quoting 'data' that isn't real. To be fair, you did not attempt to quote any data. You merely made a qualitative statement and I've already addressed that.
Perhaps the F-35 use some sort of active stealth technology rather than relying on a passive system that utilizes shape and airframe coatings.
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