Does Sydney J. Freedberg Really Not 'Get' Stealth?

Or does he keep shovelling this crap just to get a steady paycheck?

This week's installment of AOL Defense Ignorance is titled: "Will Stealth Survive As Sensors Improve? F-35, Jammers At Stake". The first half of the title is a legitimate question asked continuously by defense planners, intelligence agencies and engineers. (The answer BTW, is found in the continued fielding and reliance on Low Observable weapon systems: So,Um, Yeahhh.)  The second half of the title is 'Oh Noes!' melodrama.

~Sigh~ Where to begin? I know!

The Experts (one is not)

Freedberg grossly understates the qualification of the real expert who believes that 'stealth' still has a future, retired AF LtGen Dave Deptula, by merely identifying him as:

...a member of AOL Defense's Board of Contributors and the first man to serve as the Air Force's head of Intelligence, Reconnaissance and Surveillance. 

If I had to list General Deptula's qualifications on this subject I think would have perhaps listed a few things missing that are more than just a little relevant to the topic at hand. Things such as General Deptula was a senior member of the 'Checkmate' organization that conceived what would become the Desert Storm air campaign plan, and from there he became the principal attack planner for the Desert Storm coalition working out of the 'Black Hole' in Riyadh. His General Officer assignments prior to last one where he was Air Staff over AF IS&R (2006-2010) included (going backward in time): 

• 2005-2006, Commander of the General George C. Kenney Warfighting Headquarters (P), and Vice Commander, Pacific Air Forces
• 2003-2005, Director of Air and Space Operations, Headquarters Pacific Air Forces,
• 2001-2003, Director of Plans and Programs, Headquarters Air Combat Command, Langley AFB, Va.

Just from the knowledge Deptula gained in performing duties commensurate with his last four  assignments means he probably counts among an extremely small clique of 'most qualified people in the world' to comment on the ramifications of stealth in foreseeable future of force-counterforce application.

Freedberg then compounds his error by trotting out a non-expert 'expert' in a rather egregious fallacious appeal to authority: "long-time stealth skeptic" Norman Friedman "an award-winning military analyst and author with a degree in theoretical physics".  While Dr Friedman has a PhD in 'Theoretical Physics' that predates the information age, his forte since that time seems to be the research and publication of 'serious' books on the developmental histories of various classes of naval ships. I would cut Freedberg some slack on using Friedman, if Friedman's contribution to the article demonstrated any insight into the subject of low observables. Instead his 'argument' consisted of nuggets such as:

 "the Air Force went hot on stealth because it was a way of showing that pilots could survive" in the face of improving anti-aircraft defenses known as "dougle-digit [SIC]SAMs," the highly capable air defense systems that the Soviet Union began developing in the 1980s.
"A lot of this is about whether pilots stay in business," Friedman went on. Especially outside the Air Force, he said, "I would suspect that people worry about stealth not being nearly as good as people claimed it was. The CNO in Proceedings said as much."

I can't say that I've ever seen a fallacious appeal to authority within a fallacious appeal to authority before, but there you go: 'the CNO sez' so it must be true'. Freedberg uses this bit as a segue to regurgitate some of the CNO's embarrassing comments from last July that I took him to task for here, and then Friedman simply parrots some of the CNO's other ill-informed commentary:

"You can't make something disappear, all right?" echoed Friedman. "What you can do is reduce the signature you get back [on the enemy's sensor screens].  More powerful processors buy you back part of the signal" – and thanks to Moore's Law, the processing power available to do that doubles every 18 months. The more powerful the processors and the more sophisticated their algorithms, the more effectively they can sift meaningful data out of the static. And no matter how stealthy an aircraft is, it still makes some noise, it still emits some heat as infra-red radiation, and – most critically – it still reflects back some portion of an incoming radar beam.

 Well I pretty much slapped this down in July too, but perhaps it is worth repeating essentially the same scenario and questions I used the last time. Questions that perhaps Dr. Friedman would have instantly thought of IF his background was in Applied rather than Theoretical Physics.

As to the 'signature' statements:

You are in Command of the control center of an Integrated Air Defense System. I am flying along at 450 Kts at 45000 ft in my Acme Stealth Bomber.  At point X and Time T, one of my ‘angles’ and/or ‘aspects’ is aligned such that my signature is detectable by one of your ‘sensor systems’.
At time T plus 1 microsecond later, that ‘angle’ and/or ‘aspect’ is no longer aligned such that it can be detected. DID your system detect me in the first place? If it did, what useful information did you collect to even process as to my range, altitude, heading, and speed? (Hint: Probably Zilch, Nil, Nada.)
Did I mention that the RCS signal return you were able to detect was the equivalent of a (at most) large insect? How many large insects, or birds, bats, or chunks of vegetable matter are flying through your network airspace at any given time? Know anything about ambient RF noise? What are the chances your system filters out that 1 microsecond of signal as random noise? (Hint: Pretty Frickin' High - and all the processing power in the world doesn't help you if you are integrating a Zero) My RF ‘fuzzball’, in all frequencies where the physics dictate I can be tracked, is defined by very narrow spikes and very deep nulls. My three-dimensional orientation to any and all of your sensors is changing constantly and rapidly-- even if I fly in a straight line, constant speed and elevation.
Oh, did I mention my tiny signal was received among all the other combat environment RF activity... including my onboard EW and offboard jammer support?  

BTW: Did I mention this is ‘day one’ and your radars and control nodes are the primary targets?

As to Dr Friedman's unoriginal gnashing over IR emissions, I'll just paraphrase myself again:

Infra-red tracking is a short range capability. Just like for visible light digital detection systems, digital infrared detection requires at a minimum 1 pixel with detectable contrast to surrounding pixels. (Analog systems, such as the human eye require 1/2 arc-seconds 'width' contrasting against the field of view).These are clear-sky minimums. Any kind of moisture in the air between target and detector, or behind the target will reduce detection range. Typical operating altitudes commonly have a lot of this moisture equal or above them.

The total target contrast is attenuated by the physical properties of the atmosphere itself. The major constituent gases 'absorb' Medium IR frequencies, and those just happen to be the part of the bandwidth emitted by the jet exhaust. The Low IR and High IR bands aren't absorbed nearly as much, but that is OK, because the emissions are much lower as well -- so the management of these emissions is accomplished by selection of outer mold line shaping, coating colors and surface textures.

Fear is the Mind-Killer

Deptula runs rings around Friedman, stating cogent fact after fact. Friedman merely expresses fear after fear with little or poor rationale for that fear:

"The way LPI usually works is you send out a signal that looks like noise and somehow you reassemble that signal when it comes back," said Friedman. That depends on massive processing power and sophisticated algorithms – which are becoming more available to everyone. Are you so much smarter in your processing than the other guy?"

Dr Friedman reveals much here. If he understood how LPI actually worked he wouldn't imply it  came down to being 'smarter' in processing. The LPI radar 'knows' what type it is, the carrier frequency used at any point in time, the modulation bandwidth used at any point in time, the modulation period, the scan timing that determines where the radar beam(s) is/are pointed at any one time, and when the radar modulation pattern used begins. The air defense systems, do NOT.

Sydney Freedberg does contortions to tie this mess of an article up at the end and there's much that in comparison to the above is simply niggling nonsense.

In closing, let me also note that among the most irritating aspects of these kinds of articles is the framing of the problem as essentially 'static' stealth designs  against an onslaught of rapid progress in low observable detection schemes. Neither is standing still, and neither rely solely on 'technology', they rely on technology AND tactics.

P.S. And I've yet to see anyone make a convincing case to not make a weapon system as stealthy as possible ESPECIALLY in the face of advanced air defense systems.

Air Force Magazine on the Latest From the F-35 Program Vaults: Part 3

Part 3 of what looks like...yep, 3

Part 2 Here

Solomon over at SNAFU! posted a piece centering on an excerpt from an Air Force Magazine article “The F-35’s Race Against Time” (November 2012 issue). I had read it already, and didn’t see anything ‘earth-shattering’ at the time. But with Sol’s posting, it occurred to me that it would probably become more interesting to people the further you got away from those familiar with the current state of aeronautics, and it may draw secondary comments from the anti-JSFers to boot.

 Situational Awareness? You need Data AND Understanding  (Source: www:SLDinfo.com)

Networking & Situational Awareness

As F-35s criss-cross enemy airspace, they also will automatically collect vast amounts of data about the disposition of enemy forces. They will, much like the JSTARS, collect ground moving target imagery and pass the data through electronic links to the entire force. This means the F-35 will be able to silently and stealthily transmit information and instructions to dispersed forces, in the air and on the ground.

I don’t think at this time we can possibly overemphasize how the F-35 systems allow a pilot to gain and exploit superior situational awareness relative to legacy systems nor how much an edge it gives to any F-35 on the network. So I’m going to refer to Barry Watts’ excellent McNair Paper “Clausewitzian Friction and Future War” (Updated PDF version here) for insight on what this means in terms of reducing Clausewitzian Friction for F-35 drivers while increasing the same for their opponents. In the early part of his Chapter 9, Watts leans heavily on R.L. Shaw’s classic "Fighter Combat: Tactics and Maneuvering,"but there is much after it that I’ve read nowhere else.

I’m asking for a slight indulgence here. I’m going to beat a dead horse to again drive home a point the advocates of simple lightweight and ultra-maneuverable fighters NEVER come to grips with: ‘first look’ (almost always) equals ‘first kill’. [To keep clear which quotes are from where, Watts quotes are normal font and the AF magazine quotes are in italics]

What factors have tended to drive engagement outcomes in air-to-air combat? Surprise was linked to general friction in chapter 6. Air combat experience going at least back to World War II suggests that surprise in the form of the unseen attacker has been pivotal in three-quarters or more of the kills. In writing about his experiences flying long-range escort missions over northern Europe with the U.S. Eighth Air Force, P–38 pilot Mark Hubbard stressed that “90 percent of all fighters shot down never saw the guy who hit them.” Hubbard was by no means alone in observing that friction in the form of the unseen attacker from six o’clock played a dominant role in engagement outcomes. The American P–47 pilot Hubert Zemke (17.75 air-to-air kills in World War II) stressed that “few pilots are shot down by enemies they see.” Similarly, the German Me-109 pilot Erich Hartmann, whose 352 kills during World War II made him the top scorer of all time, later stated that he was “sure that 80 percent of kills never knew he was there before he opened fire.”

Subsequent technological developments in the means of air-to-air combat did not change the basic pattern observed by Hubbard, Zemke, and Hartmann during World War II. These developments include the shift to jet fighters for air superiority during the Korean War, the advent of infrared air-to-air missiles by the mid-1950s, and the appearance of radar-guided air-to-air missiles in time for American use in the Vietnam War. The best combat data are from the American involvement in Southeast Asia. From April 1965 to January 1973, American aircrews experienced more than “decisive” air-to-air engagements, meaning encounters in which at least one U.S. or North Vietnamese aircraft was destroyed. These engagements produced some 190 aerial kills of North Vietnamese fighters against 92 American losses. Detailed reconstructions of the 112 decisive engagements from December 18, 1971, to January 12, 1973, revealed that 81 percent of all aircrews downed on both sides either were unaware of the attack, or else did not become aware in time to take effective defensive action. In the jargon of contemporary American aircrews, such failures to be sufficiently cognizant of what is taking place in the combat area around one to avoid being shot by an unseen or unnoticed adversary have come to be described as a breakdown of situation (or situational) awareness. In an air-to-air context, situation awareness (or SA) can be understood as the ability of opposing aircrews to develop and sustain accurate representations of where all the participants in or near the air combat arena are, what they are doing, and where they are likely to be in the immediate future. This understanding of situation awareness is, of course, crucial to appreciating that the driver in 81 percent of the decisive air-to-air engagements in Southeast Asia from December 1971 to January 1973 involved more than just the “element of surprise,” although this was the interpretation at the time. Surprise can certainly affect combatant situation awareness on either side…

… Even without the evidence from subsequent tests like Air Combat Evaluation (ACEVAL) in the late 1970s and the Advanced Medium Range Air-to-Air Missile (AMRAAM) Operational Utility Evaluation (OUE) in the early 1980s , combat data from Europe in World War II and Southeast Asia during 1965–1973 not only confirm the contention in chapter 8 (proposition I) that general friction can dominate combat outcomes, but indirectly quantify what the term “dominate” has meant in historical air-to-air combat. If some 80 percent of the losses have resulted from aircrews being unaware that they were under attack until they either were hit or did not have time to react effectively, then a relative deficit of situation awareness has been the root cause of the majority of losses in actual air-to-air combat. A deficit in situation awareness accounts for four out of five losses. While this statistic may not measure frictional imbalances directly, it does reflect the influence friction has had on outcomes over the course of large numbers of air-to-air engagements.

“You’re only about one-third as efficient as you think you are [at sorting in complex engagements], which is why you go out with a sexy missile and lose your ass anyway.”

Watts goes on to iterate the ‘surprising’ (to some) AIMVAL/ACEVAL and the AMRAAM OUE results, then follows up with a discussion that hints as to what the F-35’s SA advantage brings to the mix (Boldface mine):

By 1984, Billy R. Sparks, a former F–105 “Wild Weasel” pilot with combat experience over North Vietnam, had been involved in analyzing or running three major humans-in-the-loop tests: AIMVAL/ACEVAL, the AMRAAM OUE, and the Multi-Source Integration test (also conducted in simulators). Yet, in reflecting on all that experience, Sparks felt that he had not once witnessed perfect sorting in 4-v-4 and more complex engagements. “You’re only about one-third as efficient as you think you are [at sorting in complex engagements], which is why you go out with a sexy missile and lose your ass anyway.” As Clausewitz wrote, in war “the simplest thing is difficult,” and it is hard for normal efforts to achieve even moderate results. Such observations go far to explain why even small SA deficits relative to the opposition have been statistically more dominant in engagement outcomes than differences in aircraft, weapons, force ratios, or other conditions such as having help from GCI. It also strongly suggests that friction’s influence on outcomes in air combat during World War II was not noticeably different in Korea’s “MiG Alley,” the Vietnam War, the Middle East in 1967, 1973, and 1982, or even in Desert Storm. In this sense, general friction’s “magnitude” does not appear to have diminished noticeably over the course of all the technological advances separating the P–51 from the F–15.

Could information technology be used to mitigate this longstanding pattern of very low sorting efficiencies in complex engagements arising from seemingly small lapses in situation awareness? Early experience in 4-v-4 and more complex engagements with the recently fielded Joint Tactical Information Distribution System (JTIDS) indicates that the answer is “yes.” JTIDS not only provides integrated, all-aspect identification of friendlies and hostiles based on available information, but even displays targeting decisions by others in one’s flight. The aggregate gains in air-to-air effectiveness resulting from these improvements in situation awareness and sorting have been nothing less than spectacular. During Desert Storm, F–15Cs, aided in most cases by E–3A Airborne Warning and Control Systems (AWACS) aircraft, downed 28 Iraqi fighters without a single loss, including 15 kills from engagements that began with BVR shots. When JTIDS–equipped F–15s flew against basically the same fighter/AWACS combination that had done so well in the Gulf War, the JTIDS “information advantage” enabled them to dominate their opponents by exchange ratios of four-to-one or better. Hence technology, properly applied, can certainly manipulate the differential in friction between opposing sides to one’s advantage at the tactical level.

The F-35 MADL capability adds another dimension beyond the JTIDS/LINK16 capability: More information and more kinds of information integrated and synthesized for easy (i.e. transparent) operator consumption and shared over a more secure link for use while skulking about in ‘Indian Country’. The system ‘sorts’ for the pilot. (Now you know why Northrop Grumman bothered with highlighting this capability in producing this video.)

Hey, Here’s That ‘Maneuverability’ Thing Again!

Because it was designed to maneuver to the edge of its envelope with a full internal combat load, the F-35 will be able to run rings around most other fighters, but it probably won’t have to—and probably shouldn’t.

"If you value a loss/exchange ratio of better than one-to-one, you need to stay away from each other," said O’Bryan, meaning that the fighter pilot who hopes to survive needs to keep his distance from the enemy.

He noted that, in a close-turning dogfight with modern missiles, even a 1960s-era fighter such as the F-4 can get into a "mutual kill scenario" at close range with a fourth generation fighter. That’s why the F-35 was provided with the ability to fuse sensor information from many sources, triangulating with other F-35s to locate, identify, and fire on enemy aircraft before they are able to shoot back.

The F-35’s systems will even allow it to shoot at a target "almost when that airplane is behind you," thanks to its 360-degree sensors.

According to O’Bryan, the F-35 also can interrogate a target to its rear, an ability possessed by no other fighter.

If you survive a modern dogfight, O’Bryan claimed, "it’s based on the countermeasures you have, not on your ability to turn."

I think that last comment is a slight overstatement. You want to be able to get out of a jam if you get your self into one. The fact that the F-35 probably won't lead you into a bad spot, doesn't mean it won't keep a really determined pilot from getting into one on his own.

Options… Options…

If the situation demands a turning dogfight, however, the F-35 evidently will be able to hold its own with any fighter. That is a reflection on the fighter’s agility. What’s more, a potential future upgrade foresees the F-35 increasing its air-to-air missile loadout from its current four AIM-120 AMRAAMs to six of those weapons.

Since the F-35’s biggest advantages (that are talked about publically anyway) in going up against large numbers of adversaries are its Stealth and its situational awareness provided by on-board/off-board systems, I’d say even the 4 AMRAAM loadout should be seen as ‘sufficient’ for otherwise pretty scary “bad guy/good guy” ratios of 3-4 to one. A 6 AMRAAM (or follow-on missile in perhaps greater numbers) loadout? Even better.

The F-35, while not technically a "supercruising" aircraft, can maintain Mach 1.2 for a dash of 150 miles without using fuel-gulping afterburners.

That works out to about 12 ½ minutes of ‘dash’ at 30K feet. The fact there is a time limit indicates that supersonic drag is slowly pulling the plane down to subsonic at Mil Power. The fact that it would take about 12 and a half minutes at 30K feet is indicative the plane is pretty slick aerodynamically without external stores. Even if the reason has to do with having no external stores and nothing else, that makes the F-35 far superior to any alternative that would be dragging around external stores.

"Mach 1.2 is a good speed for you, according to the pilots," O’Bryan said.

This is a mildly interesting data point, as M1.2 is commonly understood as the point where the definition of “transonic” ends and true “supersonic” begins (see chart below).

At Mach 1.2, you are usually still high on the supersonic drag rise. Source: DESIGN FOR AIR COMBAT,, Pg 46,  Ray Whitford   Update: Graphic now showing drag rise for swept wing configuration vs. straight wing.

 If Mach 1.2 is a ‘good speed’, then I would deduce that probably means that the F-35 supersonic aerodynamic drag, the F-35 installed thrust, or simply the F-35 thrust/drag ratio is among the best possible for a fighter operating within the laws of physics and given current propulsion/airframe technologies.Though may not be a ‘worldbeater’, it will hold its own aerodynamically, and it definitely means the F-35 is nowhere near a ‘dog’ as some might fear (or hope).

A Questionable Advantage (AKA “4th Gen Fighter Think in a 5th Gen World”)

The high speed also allows the F-35 to impart more energy to a weapon such as a bomb or missile, meaning the aircraft will be able to "throw" such munitions farther than they could go on their own energy alone. 

As I noted in the comments at Sol’s SNAFU! site, I really don’t see a very large benefit here. I do see an artifact of the ‘speed is life’ religion.

'Fairly Easily'?

There is a major extension of the fighter’s range if speed is kept around Mach .9, O’Bryan went on, but he asserted that F-35 transonic performance is exceptional and goes "through the [Mach 1] number fairly easily." The transonic area is "where you really operate."

Agreed.
But I wonder about the earlier ‘warning signs’ that the transonic acceleration time KPPs were unlikely to be met? Perhaps this hints at changes to the KPP? If so, I believe it would be completely justified: The spec was originally written to surpass or equal those of legacy systems, but as far as I can determine, all legacy aircraft performance was verified/validated using a clean, unarmed configuration.
Since there is no aerodynamic difference between the F-35 in its primary unarmed or armed configuration (internal stores only), the KPP should have been written to be one that was based upon legacy platforms combat capabilities with loadouts comparable to the F-35’s internal load. This would have kept the relative measure comparison an ‘apples to apples’ exercise. A potential side-benefit of changing the KPP might be the entertainment value from inducing know-nothings to whine about the F-35 ‘cheating’ on KPPs…again.

More Range? Mo Bettah!

In combat configuration, the F-35’s range exceeds that of fourth generation fighters by 25 percent. These are Air Force figures, O’Bryan noted. "We’re comparing [the F-35] to [the] ‘best of’ fourth gen" fighters. The F-35 "compares favorably in any area of the envelope," he asserted.

Conclusion:

The F-35 is an all aspect low observables, net-centric systems, long-range, yankin’, bankin’, killin’ machine.

Works for me.

Questions for Aerospace/Defense “Journalists”

A few questions for the Aerospace/Defense “Journalists” out there.

What are the odds that two different ‘news’ sources (one, two -- and two is worse) would come up with--shall we say, “twisted” articles concerning the standup of the first USMC F-35 squadron in Yuma within a day of each other without pre-coordination or as a reflex to information coming from a common pro-active source?

4:10 (F-35) to Yuma

What are the odds that the articles would also have the same basic twist (emphasis on the work ahead and not goals achieved, consistent repetition of old problems minimizing or ignoring progress made on known issues, and using the same sort of breathless reporting to make relatively minor technical problems appear as if they were of grave consequence) ? Again, without pre-coordination, or in reflex to information from a common, pro-active source?

What are the odds of these same articles being issued at essentially the same time after months of nothing but a long string of good news and successes coming out of the F-35 program?

What are the odds this ‘coincidence’ occurred after the election by design? It seems the closer we got to the election, the quieter the anti-JSF crowd became.

I don’t smell conspiracy coming from the usual circle of defense writers.

I smell sloth, smug ignorance, gullibility and possibly the spoor left behind by the usual suspects in the rabid Anti-Defense Establishment.

Fess up boys. Who’s writing your first draft these days?

Did your 'sources' get wind of this version of the story ahead of time and exhort you to perform damage control?   

Air Force Magazine on the Latest From the F-35 Mavens

Part 2 of How Ever Many It Takes
Part 1 Here 

Solomon over at SNAFU! posted a piece centering on an excerpt from an Air Force Magazine article “The F-35’s Race Against Time” (November 2012 issue). I had read it already, and didn’t see anything ‘earth-shattering’ at the time. But with Sol’s posting, it occurred to me that it would probably become more interesting to people the further you got away from those familiar with the current state of aeronautics, and it may draw secondary comments from the anti-JSFers to boot.

Dramatic Stealthiness (The Air Force Magazine Heading Not Mine)

The F-35’s radar cross section, or RCS, has a “maintenance margin,” O’Bryan explained, meaning it’s “always better than the spec.” Minor scratches and even dents won’t affect the F-35’s stealth qualities enough to degrade its combat performance, in the estimation of the company. Field equipment will be able to assess RCS right on the flight line, using far less cumbersome gear than has previously been needed to make such calculations.

 This will generate a major military culture change. If not, dollars to donuts either wing kings will start having strokes if they are told they shouldn’t touch “minor scratches and even dents” or someone with a paint can just won’t be able to resist making his jet ‘purtier’. The second alternative future already occurred when the Navy first fielded the F-18E/F.

Low Observability: In From the Start or Not At All

Stealth, said O’Bryan, has to be "designed in from the beginning" and can’t be added as an afterthought or upgrade. That means radar, electronic warfare, data links, communications, and electronic attack "need to be controlled" and must be fused from the start to work in concert with the special shapes and materials of the airframe itself.  

And that beauty has to be more than skin deep. You cannot underestimate the requirement to design the low observability into a plane as an integrated whole. Every academic/scientific text I’ve ever read on the subject stresses this point. Which makes Carlo Kopp’s latest as noted by David Axe over at Wired seem even more clownish. (I got a call from a friend and colleague who told me about it this weekend amid hearty laughter. I may slap it down with extreme predjudice in the very near future.)

The F-35A fighter has an active electronically scanned array radar and unique antennas spaced around the aircraft so that it can direct radar energy precisely, with minimal "bleed" in unintended directions. That puts more power where it’s wanted and reduces emissions that can give away the F-35’s position.  

In addition, it uses machine-to-machine communications with other F-35s. Emitters such as the radar and the electronic warfare system can flash on and off among all the F-35s in a flight.

AESA radars have most of this in common. What is intriguing is the question of what is meant by ‘unique antennas’? Could we guess what some are? Probably. Will we? No.
This also lists or hints at several advantages of modern radars with integrated EW suites. They’re not just 'spread-spectrum'. The 'low probability of intercept' idea is reinforced by beam control and short duty cycles, which tend to make the radars appear to be ‘noise’ more than anything else to most systems most of the time (nothing is certain).

'Only' 25% of “Too Much Signature” is… Still Way Too Much

O’Bryan took skeptical note of other fighter makers’ boastings that they have reduced by up to 75 percent the radar signatures of their fourth generation aircraft. He finds the claim perplexing; their original signatures are so massive, he says, that even a 75 percent reduction still leaves a huge radar return. These uprated fighters are visible within the maximum range of adversary air-to-air missiles, he said.  

"You basically haven’t really done anything, in terms of a practical tactical advantage against an enemy," said the Lockheed official. Worse, the RCS reductions evaporate once nonstealthy ordnance, fuel tanks, and other stores are hung on the "clean" aircraft.

"Until you have a first-shot, first-look, first-kill" capability, said O’Bryan, "you’re still at the same standoff [range], hoping that training and tactics are going to overcome a potential adversary." 

The most shocking thing is the fact that those points even needed to be said out loud.

Imitation is the Sincerest Form of Flattery

China and Russia have recognized the fallacy of trying to make a silk stealth purse out of a nonstealthy sow’s ear. That is why China is vigorously pursuing the J-20 and Russia the PAK-FA stealth fighter designs. If their programs pan out as expected, said O’Bryan, "fourth gen airplanes are really going to be at a serious disadvantage" against them.  

In a modern A2/AD environment, no fourth generation fighter can survive, O’Bryan insisted, no matter how much support it receives from jammers. In such an environment, however, the F-35 can fly in relative safety, with more range than the F-16 and with the same combat payload.  

When enemy defenses have been beaten down, and the need for stealthiness is not so strong, the F-35 will use both internal and external stations. That would boost its carrying capacity to a full 18,000 pounds of ordnance—more than triple the F-16’s max load of 5,200 pounds.

The transition to a non-LO configuration will always be situational: a judgment call, based upon a Commander’s weighing of the relative risks and benefits. Immediately after Desert Storm, the assumption was that once the IADS were taken care of, the switch to non-LO assets could be made in short order. After Operation Allied Force, where the Serbs made a decision to shepherd and conserve their air defense assets as much as possible, the thinking shifted away from simply assuming the transition from LO to Non-LO operations would occur.

O’Bryan said the F-35 is an all-aspect stealth aircraft—that is to say, stealthy from any and all directions. 

Now, this is not news. But watch the watchers parse the above as consistent with their current views of F-35 low observability. Expect exclamations akin to “He didn’t say it was all aspect VLO or other such drivel. I can call it drivel because if the F-35 low observability meets the design requirements, it is ‘stealthy enough’. If it were more ‘stealthy’ than it needed to be, the same people would b*tch about it driving cost.

No Vectored Thrust, No Woe Is Us

Cost and performance trade-offs were made when it came to designing the F-35’s exhaust system, O’Bryan said. Lockheed Martin chose not to employ a two-dimensional thrust-vectoring nozzle, as it had on the F-22 Raptor.  

For one thing, the decision reduced cost. For another, it eliminated one of the larger practical challenges to maintaining the stealth characteristics of the F-35.  

The classified "sawtooth" features that ring the nozzle help consolidate the exhaust into a so-called "spike" signature, while other secret techniques have been employed to combat and minimize the engine heat signature.  

"We had to deal with that, and we dealt with that," O’Bryan said, declining to offer details.

This is kind of funny, because by logical extension, the question of “why not F-22-like thrust vectoring?” could also be logically carried forward to “Why only two-dimensional thrust vectoring?” for the F-22. The answer is of course the same: "insufficient performance return for the investment".

O’Bryan certainly couldn’t go into the subject of the fighter’s EW/EA suite in any detail, or the way it might coordinate with specialized aircraft such as the E-3 Airborne Warning and Control System, RC-135 Rivet Joint, E-8 JSTARS, or EA-18G Growler jammer aircraft.  

He did say, however, that F-35 requirements call for it to go into battle with "no support whatever" from these systems.  

"I don’t know a pilot alive who wouldn’t want whatever support he can get," O’Bryan acknowledged. "But the requirements that we were given to build the airplane didn’t have any support functions built in. In other words, we had to find the target, ... penetrate the anti-access [defenses], ... ID the target, and ... destroy it by ourselves."  

O’Bryan said the power of the F-35’s EW/EA systems can be inferred from the fact that the Marine Corps "is going to replace its EA-6B [a dedicated jamming aircraft] with the baseline F-35B" with no additional pods or internal systems.  

Asked about the Air Force’s plans, O’Bryan answered with several rhetorical questions: "Are they investing in a big jammer fleet? Are they buying [EA-18G] Growlers?" Then he said, "There’s a capability here."  

O’Bryan went on to say that the electronic warfare capability on the F-35A "is as good as, or better than, [that of the] fourth generation airplanes specifically built for that purpose." The F-35’s "sensitivity" and processing power—a great deal of it automated—coupled with the sensor fusion of internal and offboard systems, give the pilot unprecedented situational awareness as well as the ability to detect, locate, and target specific systems that need to be disrupted.  

Translation: I’m not ‘saying’, but look at what you know already. Nudge, Nudge, Wink,Wink.

DEAD vs.SEAD

When it comes to electronic combat, the F-35A will make possible a new operational concept, O’Bryan said. The goal is not to simply suppress enemy air defenses. The goal will be to destroy them.  

"I don’t want to destroy a double-digit SAM for a few hours," he said. "What we’d like to do is put a 2,000-pound bomb on the whole complex and never have to deal with that ... SAM for the rest of the conflict."  

At present, that is difficult to do. Adversaries, O’Bryan pointed out, recognize that the basic American AGM-88 High-Speed Anti-Radiation Missile has a light warhead able to do little more than damage an air defense array. Thus, they have adapted to the threat by deploying spare arrays with their mobile systems.

I’d say 1. DEAD vs SEAD is not new and 2. O’Bryan is somewhat over-simplifying. One 2K bomb’s blast radius wouldn’t take down a double digit SAM complex, He’s obviously talking about going against the control van or other control node with a single weapon. I think more likely would be single pass with SDBs en mass against multiple aimpoints. Basically a scaled down version of what the B-2 did in Allied Force against targets such as the Krivovo Support Base:

Krivovo Support Base, Post Strike, Operation Allied Force

In the photo above are very large warehouses struck in one pass by 2K JDAMs in Operation Allied Force. Note how the bombs were placed at alternate ends of the inside two warehouses for each four building set. The overpressure/blast also damaged the adjoining buildings, staggering and spreading the weapons allowed for maximum destruction in minimum time and aimpoints. Note also how the ends of the buildings that were struck were selected to also impede access to the target by the adjacent road as much as possible.

Since 1999, weapon accuracy and flex target capabilities have only gone up, and while the subject SAM radar, control, and transporter-erector-launchers are smaller targets, they are also "soft" when you find them. And between the EOTS (video) and the AESA(video), they will be found. And we won’t even go into how easy they are to find post-launch when you can track a missile back to the launch point (video at http://www.youtube.com/watch?v=qF29GBSpRF4, link will not embed for me right now). Postt launch detect and destroy is not a trivial point because there are alot fewer TELS than missiles. Destroying TELs early pays off big as you go down the timeline of a conflict.   

End of Part 2
Part 3 Here

Air Force Magazine on the Latest From the F-35 Mavens

Part 1 of How Ever Many it Takes

Earlier this week, Solomon over at SNAFU! posted a piece centering on an excerpt from an Air Force Magazine article “The F-35’s Race Against Time” (November 2012 issue). I had read it already, and didn’t see anything ‘earth-shattering’ at the time. But with Sol’s posting, it occurred to me that it would probably become more interesting to people the further you got away from those familiar with the current state of aeronautics, and it may draw secondary comments from the anti-JSFers to boot.


500th Sortie of an F-35A Lightning II joint strike fighter from the 33rd Fighter Wing at Eglin Air Force Base, Fla., flies over the Emerald Coast Sept. 19, 2012 preparing to land. (From Original U.S. Air Force photo/Master Sgt. Jeremy T. Lock)

The magazine itself is the monthly publication of the Air Force Association, so one could almost view it as an ‘unofficial’ Air Force’s newsletter. It’s a glossy-photo publication designed mostly for consumption by AF/Defense insiders and Hoi Polloi, so you won’t find improperly leaked technical details or rants about programs, policy or planning. There are special topics the magazine takes on from time to time where they go into great depth on the topic, but that is not their normal fare. What you will find frequently are general info articles that sometimes yield nuggets of gold: first glimpses of information as it is officially released into the public domain. The excerpt Sol was excited about was the first public revelations of the F-35s capability to travel some distance over Mach 1 without afterburner. Not really ‘supercruise’, but surely a performance surprise for the F-35’s more ardent critics.

I thought I’d add to Sol’s posting with some more excerpts and observations on some things that may be of interest in the same article.

Lockheed Martin Vice President Stephen O’Bryan, the company’s point man for F-35 affairs, declared that the fighter meets requirements. A former Navy F/A-18 Hornet pilot, O’Bryan said the combat capability of even the earliest baseline model will greatly exceed that of the most heavily upgraded fourth generation fighters and strike aircraft, such as the F-15, F-16, and F-18.

The one thing I think we should take away from this point is the implied fact that the first full-rate production versions of F-15, F-16, and F-18 aircraft were NOT representative of the fully capable type, and many were bought in relatively large numbers compared to the total buys. ALL underwent significant, mostly preplanned design ‘upgrades’ before their definitive types were finally fielded. By ‘definitive’ I mean most or all the capabilities that were programmed to be part of the platform when production began were either installed or ruled out.

Example: The Lightweight Fighter Mafia and their fellow travelers consider the early F-16s to be ‘definitive’ from their POV, but until the Block 30/32 aircraft were brought to realization, there were considerable shortcomings seen in the type, and they were seen by the responsible players from the start:

Gen John J. Burns, a man with impeccable fighter-pilot credentials antedating any of those belonging to members of the “Fighter Mafia,” enthusiastically endorsed missiles— especially the BVR variety. This inclination largely accounted for his skepticism about the lightweight fighter. As it stood at the time, because the F-16 did not have a sufficient radar for semiactive AIM-7s, it could usually fire on an enemy only from the rear quadrant— whereas an enemy with a radar missile could shoot one in the face of the F-16 pilot. Since World War I, the plane taking the first shot has a rather pronounced tendency to win.  

As noted, not until the AMRAAM got its initial operational capability in the early 1990s did the Viper acquire a BVR weapon—itself a “high-tech” answer. General Burns’s attitude is neither new nor limited to senior officers. From the beginning, one could find in the Fighter Weapons Newsletter of the late 1950s great enthusiasm for the new missiles among junior fighter pilots. For example, Capt Robert Thor, writing in 1958 while Boyd was still assigned to Nellis, argued that in the near future a fighter pilot who came back claiming a gun kill would be confessing a failure to use his missiles properly. -------Dr David Metz “Boydmania” (some solid debunking of ‘Boyd’ myths at the link)

Capabilities

The Air Force Magazine article continued…

The fighter’s capabilities will make it a three- or four-for-one asset, said the Lockheed briefers, meaning that it will be able to simultaneously perform the roles of several different aircraft types—from strike to electronic attack, from command and control to battlefield surveillance.  

O’Bryan pointed out an important truth about air combat: Fourth generation strike aircraft assigned to hit targets guarded by modern anti-access, area-denial systems (A2/AD, in military parlance) require the support of "AWACS, electronic attack, sweep airplanes, SEAD" (suppression of enemy air defenses) aircraft and cruise missiles. Such a package could run to dozens of aircraft.  

The same mission, he claimed, can be achieved with just a quartet of F-35s. Each would be capable of operations that go well beyond air-to-ground missions. The four-ship would be a potent factor in any scenario calling for the employment of airpower, O’Bryan asserted.

The first paragraph is OK as long as we’re talking about missions versus numbers. Lanchester’s Square laws still apply, though the ratios may vary, and keep in mind one airplane can’t be in more than one place. The assertions made in the two paragraphs following the first indicate that this is O’Bryan’s intent, but I can see people confusing missions and end strength if they don’t know any better.

Next the discussion moved to ‘Maintainable Stealth’….

When it comes to maintainable stealth design, the F-35 represents the state of the art, O’Bryan said, superior even to the F-22 Raptor, USAF’s top-of-the-line air superiority aircraft.  

The F-22 requires heavy doses of regular and expensive low observable materials maintenance. F-35 stealth surfaces, by contrast, are extremely resilient in all conditions, according to the Lockheed team. 

"We’ve taken it to a different level," O’Bryan said. The stealth of the production F-35—verified in radar cross section tests performed on classified western test ranges—is better than that of any aircraft other than the F-22.  

This, he went on, is true in part because the conductive materials needed to absorb and disperse incoming radar energy are baked directly into the aircraft’s multilayer composite skin and structure.  

Moreover, the surface material smoothes out over time, slightly reducing the F-35’s original radar signature, according to the Lockheed Martin official. Only serious structural damage will disturb the F-35’s low observability, O’Bryan said, and Lockheed Martin has devised an array of field repairs that can restore full stealthiness in just a few hours.

This is a mixed bag to comment on. On the one hand, yes the F-35 LO design approach was heavy on incorporating lessons-learned from prior systems, and it appears the result is solid. But if you want to make commentary on any earlier LO designs, you have to also acknowledge the reason why the lesson ‘took’ was that designers figures out that the first peacetime priority for wing commanders is flying schedule and pilot proficiency.

I suspect the F-22’s peacetime LO maintenance burden is skewed by commanders opting to NOT fix LO discrepancies when they appear and let them fester and grow lest they threaten the flying schedule. Funny thing how metrics can drive the performance instead of measure it: if Commander performance reports are involved they usually cause people to care about what they measure MORE than measuring what they should care about.

I also have a minor problem with the blanket F-35 RCS performance “is better than that of any aircraft other than the F-22”. If he would have said ‘fighters’, I’d MIGHT be fine with it. But since LO design is tailored to the mission and operating environment, non-fighter LO systems’ LO performance are not comparable. I won't even mention that he couldn't possibly be briefed on every program to make such an assessertion, nor would the people running the range likely tell him more than he needed to know, and he wouldn't need to know the performance of other systems.

End of Part 1
Part 2 Here

Extreme Angle of Attack: What is It Good for?

Not as much as you might think.

In looking at AoA papers related to the series I just concluded, I ran across a paper that was able to express what good Aeros everywhere already know. Higher maximum AoA does not translate into more "vector" change if it sucks down your "smash".

Perhaps this gives some indication as to why there is a 'specified' AoA for the F-35?

(and all the AoA over and above that point probably won't count for much.)

From: EVALUATION OF FUNCTIONAL AGILITY METRICS FOR FIGHTER CLASS AIRCRAFT, B.W. Cox and D.R. BrDowning University of Kansas, AIAA-92-4487-CP, 1992.[boldface emphasis mine]

 

The following conclusions are drawn from the evaluation of the metrics:

1) The Combat Cycle Time metric is dominated by the sustained turning and acceleration phases which are already assessed by traditional measures of merit. However, the metric provides insight into two features of aircraft capability not considered by traditional measures of merit. First, the metric provides a measure of the ability of the aircraft to transition between two sustained aircraft maneuver states. Second, the metric's time based value rewards quick flight path whose pointing maneuvering while simultaneously balancing this reward with a penalty for large energy losses.


2) The Dynamic Speed Turn plots do not measure any new aircraft capabilities and thus do not assess capabilities not already addressed by traditional measures of merit. Rather, the strength of these plots is derived from a) their ease in depicting the penalty paid for achieving certain performance levels at various airspeeds and b) their ability to clearly compare the maneuver capability of dissimilar aircraft. To obtain the same information from traditional energy maneuverability diagrams requires a more timely and detailed analysis and the resulting comparisons between dissimilar aircraft are not as concise.


3) The Relative Energy State metric has two features not addressed by traditional measures of merit. First, the metric stresses the importance of retaining maneuver potential since either defensive or offensive maneuvers may be required after a turn in a multi-bogey environment. Second, the deceleration to corner speed is clearly quantified.


4) The quantification of these metrics showed that the angle of attack load factor limiter in the F-16A provided that aircraft with a definite advantage over the F-18A, F-5A, and X-29A. The limiter, although reducing the maximum turn rate, prevented the aircraft from reaching high energy bleed rate conditions. This limiting essentially relieves the pilot of the responsibility of having to set up an optimum maneuver. However, the metrics quantified here do not provide an ability to assess the benefits of performing high angle of attack maneuvering - a capability which could potentially offset the associated energy losses.

THE DESTROYER MEN: A Veteran's Day Tribute

The evolution of a WW1 tribute to destroyer crews.

(Something different for Veteran’s Day )

Berton Braley is little heard of today, but early in the 20th Century he was quite a celebrity…and prolific poet. I wonder how much his obscurity today is due to him being a commercial success AND a ‘Philosopher of Freedom’? I discovered him quite by accident, trying to track down the origins of a poem titled “Destroyer Sailors” that my Grandfather had scribed in the back of his ‘Cast Iron College’, aka Machinists Mate School, notebook in 1926. He attributed the work to ‘Sunset Red the Poet’. Using that as a starting point, trying to find who wrote the original turned into an interesting journey: it appears the poem has been adapted to different eras, with slightly different titles, and attributed to various people as it has been handed down through time. The original poem was written during World War I, titled The Destroyer Men, and back when ‘destroyers’ themselves were relatively new:

Source: Navy.mil

 
THE DESTROYER MEN
There’s a roll and pitch and a heave and hitch
To the nautical gait they take,
For they’ re used to the cant of the decks aslant
As the white-toothed combers break
On the plates that thrum like a beaten drum
To the thrill of the turbines might,
As the knife bow leaps through the yeasty deeps
With the speed of a shell in flight!

Oh ! their scorn is quick for the crews who stick
To a battleship s steady floor,
For they love the lurch of their own frail perch
At thirty-five knots or more.
They don t get much of the drills and such
That the battleship jackies do,
But sail the seas in their dungarees,
A grimy destroyer s crew.

They needn’t climb at their sleeping time
To a hammock that sways and bumps,
They leap kerplunk ! in a cozy bunk
That quivers and bucks and jumps.
They hear the sound of the seas that pound
On the half-inch plates of steel
And close their eyes to the lullabies
Of the creaking frame and keel.

They scour the deep for the subs that creep
On their dirty assassin s work,
And their keenest fun is to hunt the Hun
Wherever his U-boats lurk.
They live in hope that a periscope
Will show in the deep sea swell,
Then a true shot hits and it s "Good-bye, Fritz"
His future address is Hell!

They’re a lusty crowd and they’re vastly proud
Of the slim, swift craft they drive ;
Of the roaring flues and the humming screws
Which make her a thing alive.
They love the lunge of her surging plunge
And the murk of her smoke screen, too,
As they sail the seas in their dungarees,
A grimy destroyer s crew!

The Poem Evolves

As you can tell from the original, it would have been quite dated post-WW1 if it hadn’t been allowed to evolve. Here is the version of the poem again as my Grandfather put it to paper less than a decade after WW1, titled ‘Destroyer Sailors. I submit this is may be the earliest record of the post-Braley versions, as it is the earliest I could find.

Read more Berton Braley online here, or more about the man and his works here.

Barry Graff's "Why the F-35" Added to My Blogroll

A Force Multiplier for Truth

I've been meaning to reciprocate a link to Barry Graff's Why the F-35? blog for some time now. He's doing yeoman's work making sure the good news about the F-35 doesn't get drowned out by the anti-JSF drumbeat.
If you haven't visited, please do so frequently from now on. There you will find all the news that should be getting out in the usual venues, but 'somehow' never seems to reach their 'front pages' (at least without a trip through the spin machine). Barry's keeping abreast of the news cycle let's me spend time on other topics and activities just as near to my heart. So... Thanks! 

Note: I'm also keeping a couple of links in my blogroll that some may wonder why, as they don't get updated very often. It's just that when they do, I don't want to miss it!  

GO VOTE!



Election 'After Battle' Report: 

It 'Aint Over'-The job just got a whole lot tougher.

 

With the exception of the usual brain dead zones (including Moscow on the Brazos), and the usual NAACP illegalities in Houston, Texas pretty much did what it could against the Rise of the "Loser Nationtm" . Too bad about much of the rest of the country. Expect more polarization at the state level as the sentient beings who can cut their strings with the 'Blue' states move to where Makers outnumber the Takers. Welcome! -- just leave any silly ideas at the state line. Concealed Carry permit applications are first door on the right.

 



Image Courtesey of the Chicago Boyz

The F-35: What Will Happen While Exploring ‘High Angle-of-Attack’, Part 4

‘Old School’ F-15: Entry to the modern world of ‘High-Performance’

Part 4 (and last) in a series of posts where we document The Profound Truth of High Angle-of-Attack (AoA) flight testing of high performance aircraft. What is “The Profound Truth”?

Discovery and rectification of undesirable aircraft behaviors during High Angle-of-Attack testing of High Performance Aircraft is not only the ‘Norm’, but those behaviors needing rectification/mitigation are usually complex, sometimes bizarre, and often ‘spectacular’.

The F-15 and AoA: A Surprisingly Short Story

My whole family had just moved to Antelope Valley to be near my Dad while he worked another flight test program at Edwards AFB-- only the month before the F-15’s first flight at the same location. I joined the Air Force before the whole family moved back to Texas six months later (Dad would often refer to himself as a “migrant aerospace worker” or “Aero Bracero”).



F-15 First Flight, July 1972 With Square Wing Tips Shown to Good Effect (US AF Photo)

I joined the Air Force before Dad’s assignment ended, but still got to see the first F-15s in the skies over Eddy and the AV quite a bit before I left. In a way, the F-15’s ‘career’ began the same time mine (paying anyway) did, and I got to watch most of the F-15’s maturation, successes, and evolution in ‘real time’ before and after I retired in 1993.

From knowledge gained going way back to the early 70’s and the heady days of the F-15’s flight test and OT&E, I thought I’d just be able to search up some early scholarly papers using a select few keywords like ‘F-15 flutter’ and ‘F-15 buffet’ and then just quote the source data as to what actually ‘happened’. But my research surprised me. There was almost NOTHING written in peer-reviewed or official literature on F-15 High AoA exploration and behaviors while they were being discovered that I could find in the public domain.

Some of this void could be due to the time frame: we were going toe to toe with Russian fighter designs in Vietnam until at least six months into the F-15’s flight test program, and the Cold War was still ‘freezing’. Absence of hard data could also be due to the priorities given to the challenges, controversies, and manufactured scandal surrounding the F-15’s engine development history. That was always in the news at the time, and the news was (usually) wrong about what was really happening with the F100 engine and why.

From forensic examination of the larger body of available ‘retrospective’ literature, it seems for the most part the Air Force was just extremely happy to be able to do what the F-15 design was intended to do: fly much deeper into the High AoA regions before onset of buffeting and stall at higher speeds than its predecessors.

In the past 10 years, U.S. military aviation has progressed from the generation of F-4/F-8 air superiority fighter to that of the F-15/16/18 aircraft, which are demonstrating significant improvements in maneuver performance. These improvements result from more sophisticated aerodynamic design, lower wing loading, and higher thrust-to-weight ratio, and they permit the newer fighters to maneuver as well at 7 to 8 g’s as the earlier aircraft did at 4 to 5 g’s. The limited assessment to date of the newer fighters indicates that they also track as well at 7 to 8 g’s as their predecessors did at 4 to 5 g’s. This is attributed largely to their improved aerodynamics and more sophisticated control systems, which permit them to operate at higher load factors with lower levels of buffet intensity and wing rock than their predecessors. – Precision Controllability of the F-15 Airplane, T.R. Sisk and N.W. Matheny, NASA Technical Memorandum 72861, 1979.

Sisk and Methany’s 'Precision Controllability of the F-15 Airplane' is particularly valuable to our examination because it recounts NASA’s experience exploring F-15 handling qualities using a pre-production F-15 (Airframe number 8). Sisk and Methany offers some insight into what needed to be ‘fixed’ on the early F-15s and why, when after 6 of 10 Gunsight Tracking tests, key systems had to be upgraded to ‘production standard’. The ‘Gunsight Tracking’ test involved making a windup turn from 1 g (trimmed) to the “maximum allowable load factor or angle of attack”.
That “adverse pilot comments concerning the airplane’s handling qualities” in the early tests drove the testers to upgrade the control system to “meet production standards with regards to friction, hysteresis, and breakout forces”, ‘replace roll and trim actuators”, and replace the ARI (Aileron-to-Rudder Interconnect) with a production unit, among other changes is a pretty good indication that the first F-15s were hairy (or at least hairier) beasts at higher AoAs.

Findings of particular note are 1) that the F-15’s buffet as experienced in the cockpit is considerably higher than that experienced in the YF-16 and YF-17 prototypes and 2) the F-15 wing buffet is “severe” at higher AOAs, with mild to moderate wing-rock at airspeeds of interest when the AoA is above “Approximately” 10 degrees.[This raises an interesting question: If the comparison holds for F-16s and F-18s, and the F-35 exhibits buffeting somewhere in between the spread, may we expect F-15 pilots transitioning to the F-35 to think of the F-35’s buffeting as “meh” and pilots transitioning from the F-16 or F-18 react to the same as “OMGWTFO!”?].

A key point to remember here is that the F-15 has no lift augmentation devices, either trailing or leading edge, so there is no way to alter wing high AoA performance without redesigning the wing itself or tweaking your primary flight controls.

Fighter Weapons Center F-15C with Conformal Fuel Tanks and Speed Brake Deployed. When I was at Nellis in the late 70s, F-15 Crew Chiefs were kept 'moist' with cases of beer that pilots would have to buy them after pushing their aerodynamic braking 'show' too far and dragging their tail feathers.

Obvious Changes as a Result of Initial Flight Test

The two most obvious changes made to the F-15 as a result of flight testing were the wingtip design and the speed brake design and operation. I can find no detailed scholarly or otherwise authoritative references to the hows and whys behind the changes were made, but the reasons seem to just be presented now in the ‘everybody knows’ matter-of-fact manner. It is common to find references to the raking of the wingtips due to transonic flutter after the third F-15 was built, but only some sources mention the flutter was occurring at higher g’s and AoAs.

The speed brake design changed at some time during the F-15’s fielding, but I haven’t found an authoritative source I can corroborate as to exactly ‘when’. It is now apparently common knowledge that the dual changes of increasing the size of the speed brake and greatly reducing the angle it can be raised on a different schedule allows the same effectiveness at higher AoAs without adding to the F-15s total buffeting.

Other Issues for Perhaps Another Time

There’s a lot more ‘back story’ on the F-15 development and later discovery of peculiar flight characteristics that have nothing directly to do with ‘just’ high angle of attack. There is the twin vertical stabilizer buffeting issue [1], that seems to affect ALL twin-tail fighter designs to one degree or another, but caused severe cracking and redesign of the F-15 vertical surfaces. There is the “Bitburg Roll” [2] phenomenon, whereby the effects of aerodynamic asymmetry caused by having the 20mm Gatling gun only on one wing root “first surfaced in 1990 as an uncommanded yawing and rolling motion on a F-15C at Bitburg” Air Base in Germany. The Bitburg Roll manifests itself as either an uncommanded roll “up to 60 degrees per second” to the right or yawing motions at higher altitudes between 250 and 350 KIAS. There is also the horizontal stabilator flutter problem [3] that was ‘solved’ by putting a ‘snag’ in the leading edge of the stabilators. The solution was found by trial and error in a wind tunnel, and only recently has the art of computational fluid dynamics reached a point where, 40 years later, it is believed the ‘why’ of the solution can be understood.

There's more back story, but the point is made that:

Operation and test has shown that aerodynamic performance can and will remain unpredictable to any exactness when aircraft are operated in regions where non-linear (the definition of ‘turbulent’) airflow occurs.

__________________

Note: Apologies for the posting drought. I've been way 'out of pocket' part of the time on business travel and been working killer hours at work and home catching up on priorities that could wait no longer.

[1] F-15 Tail Buffet Alleviation: A Smart Structure Approach; Georgia Institute of Technology; WPAFB Contract Number F33615-96-C-3204; 1998.

[2] An Investigation Into The Effects Of Lateral Aerodynamic Asymmetries, Lateral Weight Asymmetries, And Differential Stabilator Bias On The F-15 Directional Flight Characteristics At High Angles Of Attack; D.R. Evans; AFIT/GAE/ENY/96M- 1; 1996.

[3] Flutter Mechanisms of a Stabilator with a Snag Leading Edge; R. Yurkovich; 19th Structures, Structural Dynamics and Materials Conference, 4 - 7 April 2011, Denver, Colorado; AIAA 2011-1847