CNO Nominee Richardson Got These F-35 Questions Too?

I told them I didn't want the job, but I answered them anyway.

Hat Tip "spazinbad" @ F-16.net

SMSgt Mac appearing before SASC?

CNO Nominee Admiral Richardson answered some pre-confirmation hearing questions. I like his answers pretty much, but like my answers better. It comes with the freedom of being long retired (as well as never being an Admiral).

RE: Tactical Fighter Programs
The F-35 Joint Strike Fighter Program, which is the largest and most expensive acquisition program in the Department’s history, was formally initiated as a program of record in 2002 with a total planned buy of 2,443 aircraft for the U.S. At projected procurement rates, the aircraft will be procured by the Department well into the 2030 decade to reach its total quantity buy. The program has not yet completed its systems development and demonstration phase, and is not due to enter full rate production until 2019, 17 years after its inception.

The Navy’s FY16 budget request indicates a program of record of 369 F-35C, with Navy procurement continuing throughout the life of the F-35 procurement program. The overall requirement for 2,443 aircraft was established nearly 20 years ago. Since that time, however, there have been countervailing pressures to: (1) reduce force structure to conserve resources; (2) improve capability to respond to prospective adversary technological advances and increased capabilities from updated threat assessments; and (3) respond to an evolving national defense strategy.

Do you believe the Navy’s F-35C requirement is still valid?
Well Senators, that’s quite a preface to a “yes or no” question. But as it comes from such an august body as the Senate Armed Services Committee, I will use the working assumption it is offered to provide proper perspective to the questions to come, rather than an attempt to ‘poison the well’,and so the Committee’s prefacing informs my response,and I believe due diligence also requires me to to expand upon the very fine points the Committee raises, in part as an answer to this first question. 

As the Committee very well knows, the F-35 Program is as large and expensive as it is because it is really three programs in one. While there have been studies that have reviewed whether or not combining programs was worth the effort, we must note that aside from them all having contentious ground rules and assumptions embedded, that NONE of them measured the costs and benefits of the F-35 program against the typical number of programs we would have to undertake to successfully field three different aircraft. Can there be any doubt looking back at history that at least four or perhaps five programs would have to be attempted to actually field three different jets? Can we possibly fathom the procurement costs per airplane if we had attempted to field the minority F-35B and F-35C as stand-alone programs? Mr. Chairman and Committee Members, the Navy and Marine Corps budgets are very blessed to have the Air Force subsidize The Department of the Navy’s rent-seeking by absorbing a disproportionate percentage of the net development costs.

As the bulk of the development is behind us in sunk cost and schedule, and there is no indication that the way forward is too difficult, completion of the systems development and demonstration phase should not be a problem.

That it will have taken 17 years to reach full rate production would be an issue above my station if I were still on active duty: I would not be in a position to second-guess prior Congressional decisions to stretch development and delay production, trading risk for schedule and cost. It would also not be my place to pass judgement on the actions of prior Congress’ that created the three-in-one program approach in the first place. 

As a retiree who returned to civilian life over twenty years ago however, I am free to answer that the former was typical, foolish, political tinkering and/or ego-stroking on the part of Congress. The latter however, is shaping up to have been a very good idea by your predecessors.

And so the final answer to your question is therefore, of course: “Yes”--the F-35C will be a VITAL part of the future Carrier Air Wing.

Do you believe the Navy can afford and needs to procure 310 more F-35Cs with a procurement cost of over $42 billion?

As to ‘need’, the F-35C provides essential 5th generation strike fighter capability to our Carrier Air Wings. Without this capability, we cannot achieve air superiority. The Department of the Navy currently has a requirement for 340 F-35Cs. That number needed of course is always subject to revision as national strategies change and new information is made available. For example, on the one hand, the Navy doesn’t yet have any operational experience with low observable or fifth generation capabilities. As the Navy gains experience, it will probably create opportunities and incentives to not procure more of or retire older systems faster on the one hand. On the other hand, the Navy has a history of buying aircraft over long timeframes due to expected attrition, and given the F-35C’s stellar initial sea trials, we may just not lose as many jets like we have in the past and so they will not need replacement. If I were confirmed as CNO, I would work with the Chairman and other service chiefs to revalidate the appropriate number of aircraft the Navy requires to meet the mission.

Speaking to the cost figure offered, let us note that the numbers you mention are either future inflated dollars or dollars that include developmental cost dollars that are already sunk, both, and/or are based upon presumptions of future economic factors that may or may not apply. They are also spread over how many years? I would enjoy exploring the nuances of these numbers with the SASC, numbers that should never be aired in a casual manner, as no doubt the SASC would agree.

Do you believe that the Navy will still want to buy the F-35C, an aircraft design that will be 30 years old before the Navy production is scheduled to finish?
Well let’s see, we’re flying the F-18C/Ds and F-18E/F/Gs right now. The current versions are evolutions of a design originally produced in 1975 and are still in procurement. That’s 40 years since inception. So 30 years should not be a stretch at all for the Navy and the F-35, especially considering that unlike its predecessors, the F-35B and C are designed to evolve as required over time. Right now the Navy is committed to making the F-35C the next Carrier Air Wing fighter, complementing the F/A-18E/F until the F-18 reaches the end of its lifetime in the 2030s when the basic design will be over 50 years old. I believe once the fleet gets its hands on the F-35C, the fighter/strike community will set new standards in creative thinking and divining ways to get rid of the older jets and buy more F-35Cs as the older jets obsolescence becomes more obvious.

Do you believe the Navy’s current and planned force mix of tactical aircraft is sufficient to meet current and future threats around the globe, and most especially in the Asia-Pacific theater of operations where the “tyranny of distance” is such a major factor?

Currently, I do. There are capability, inventory, and readiness aspects to delivering the required force mix. If I was ever to be confirmed as CNO, I would work with leadership to determine the best options to pace the threat in a dynamic security environment. The fiscal environment will bound the scope of our efforts, and so I would urge Congress to work harder in creating a fiscal environment that will provide for all of our Constitutionally-mandated needs.

The Secretary of the Navy recently remarked that he believed the F-35 should be and would be the nation’s last manned fighter aircraft. Do you believe this to be true?
If I were to be confirmed as CNO, I would work with the Secretary of the Navy to aggressively advance the development of unmanned systems. It is crucial that we push the boundaries of what unmanned technologies can achieve; the next generation in tactical aviation will play a large part in this transformation.

Having said the above, let me also observe that the Secretary has all of the technical knowledge and expertise in all the relevant knowledge areas and disciplines, with the liberal-arts and legal education sufficient to have once been a competent junior ship’s officer. I’m sure he was a very fine surface warfare officer, once upon a time. His thoughts and opinions on the subject of UAVs carries all the commensurate weight that comes with such an accomplished background.

I thank the Committee for their interest. Now go away.

A Mysterious LM CUDA Missile Update

Just gets more interesting as time goes on...

Major Hat Tip to Marauder for finding the relevant AFIT Technical thesis and passing it along

Regular readers may remember one of my most popular posts on LM’s CUDA missile concept. In that post, I hypothesized some about the CUDA’s weight and resultant performance by using a comparative analysis of what little was known about the CUDA and existing missiles with known physical characteristics. Key assumptions were that the same kind of propellant characteristics and relative scaling of the different components of existing missiles would apply to the CUDA.

Based upon a recent AFIT paper I no longer believe that approach is sufficient.

Employment of a CUDA missile ‘concept’ was used in a thesis written by Army Major Casey D. Connor, and published earlier this year. In his paper “AGENT-BASED MODELING METHODOLOGY FOR ANALYZING WEAPONS SYSTEMS”, Major Connor modeled and examined the relative effectiveness of different missile loadout combinations for a very specific A2A mission using two methods of attack: 'straight-in' and ‘pincer’.
The paper was exploratory in nature, and there’s not enough in the paper to come to any more conclusions than Major Connor did -- but I’m sure someone will read more ‘findings’ into it than he did. In fact, I'd expect 'some' to leap to all kinds of ‘conclusions’ about a lot of different sub-topics because the paper really does raise some very interesting questions that someone else will probably/hopefully pick up and follow-up on going forward.
The value of the paper to us in this instance is that it gives us an indication of some key performance—shall we say—“possibilities” for a CUDA-like weapon system. The paper uses the terms CUDA-like and SACM (Small Advanced Capability Missile) interchangeably. Given the rumblings on the web and in aero media since the CUDA concept’s existence went public, the relationship of the CUDA (a Lockheed Martin concept) to SACM (the programmatic objective of CUDA) is now better known. No surprises there.

What is Surprising?

What IS surprising (to me at least) are the characteristics used for the CUDA/SACM in Major Connor’s thesis. Specifically, Connor provides the CUDA/SACM weight used in his simulations as 49Kg (108 lbs). This has HUGE implications. 

If by my original speculation where I extrapolated known data about existing technology, I had arrived at a weight estimate that was 45.5 lbs higher (153.5 lbs) than the 108lb weight Connor uses, then it almost certainly speaks of significantly more advanced/miniaturized technology than simply scaling down 'more of the same' from existing systems.

I had toyed with putting a wedge in my original estimate for a reverse-weight spiral (less structural weight is needed the lower the non-structural weight), but thought that would have been pushing all the ‘estimating’ a little too far. As it turns out I would have come closer, but still nowhere near a mere 108 lbs for a CUDA weight estimate by my using current weapons for baseline info. I think now that ‘Next generation’ guidance, control, structure, and maybe  propulsion technology breakthroughs almost certainly permeate that CUDA/SACM design concept. As the scaling of RM propellant weight probably still applies (harder to make lighter propellant than other components), I don't think there's much weight change per cubic inch of volume there. But even so, this new lower weight could potentially drive the CUDA/CACM higher in the ‘Delta V’ performance than what I had previously estimated.

What Changed?

If only the weight is lower, with the other factors such as the ratio between pre-launch and expended rocket motor weights, and propellant/rocket factors, etc., then the CUDA potential top speed would not necessarily be higher than my first estimate (~24% higher than AMRAAM using existing missiles as guides). But I don’t think that at this new lighter weight, the same ratio CAN still hold true: a larger percentage of the total CUDA/SACM weight is now more likely found in the rocket motor -- if only just because everything else got lighter.
This shift in weight contribution, in turn, would mean a larger percentage of pre-launch weight is propellant that will be expended in acceleration. The scope of the impact of such a change is unknown, but here is a parametric exploration of the impact of various possible RM weight ratios from no change (54.53%) and up to a little more than 5% increase (60%):

What if the CUDA has a higher percentage of propellant weight than the AMRAAM?
(updated verbiage for more clarity less obfuscation)

As you can see, very little increases in the ratio of propellant weight to total weight yields significantly higher potential Delta V that could be tapped into to:

1. increase range, 
2. enable shaping complex flyouts, and/or 
3. increase end-game dynamics. 

That this improved performance is likely a ‘truism’ in the CUDA/SACM design concept is reflected in Major Connor’s findings.

Connor’s modeling of the engagements he selected resulted in outcomes where the ‘pure’ CUDA/SACM loadout successfully engaging the RED AIR targets at significantly greater distances (32%-38% greater, depending on attack method used) than the Medium Range Missile Model (AMRAAM-basis) used (see Fig. 43 below from the source). That kind of range advantage would be consistent with a higher Delta V for the CUDA/SACM weapon.



[Note: Read the paper for information on the mixed loads of a short range missile (AIM-9X ‘like’), medium range missile (MRM) and the CUDA/SACM weapons]

The higher performance of the CUDA/SACM also shows up in the higher 'effectiveness' ratings of the pure CUDA/SACM loadout over the pure MRM loadout. As Figure 42 from the paper below illustrates, the pure CUDA/SACM missile loadout kills targets at better than a 2 to 1 advantage over the MRM’s kill rate as well as doing so at ranges farther than the MRM. 

This increased effectiveness suggests perhaps an even better end-game kinematic CUDA/SACM design performance than the MRMs due to a higher percentage of propellant design weight, working with the hit-to-kill Attitude Control Motors (ACMs) in the front-end. 

Connor’s focus in the paper isn’t on getting into the nuances of the CUDA/SACM’s capabilities, but the higher performance of the CUDA concept indicated by the data is supported by his observations within the text as well:

The main characteristics of the new missile technology examined in our research include hit-to-kill technology in which the missile uses a kinetic warhead to attack the target, agility in that the missile’s guidance, propulsion, and control surfaces allow it to maneuver more flexibly towards a target, and a smaller size allowing each fighter to carry more missiles. These new weapons have the potential for dramatically changing the range of possible tactics and mission roles allowed. (p.1)

And…

Tactics best suited to the new missile are ones that maintain BVR to take advantage of the increased engagement ranges and possibly combined tactics that allow the flexible maneuvering characteristics of the new missiles to engage enemy aircraft at angles that the enemy aircraft will be unable to counter. (p.102)

There’s a lot of other ‘food for thought’ on many air combat topics in the paper. Connor was meticulous in documenting what he could of the methodology that he used including the limitations, ground-rules and assumptions. There’s also some excellent sources listed for further reading in the list of references.

Time will tell if the SACM concept will be developed into a full-up weapon system. But I must say that if it doesn’t go forward in some iteration or another I will be even more surprised than I have been so far in following the CUDA/SACM story.

Note: minor edits for readability and clarity made 16 July @ 1945 CST.

F-35 'Reporting' : A Study in Contrast

Take a look at the serious article at AIN on the effects of the latest F-35 cost reduction efforts here, and contrast it with the crap dropped to days ago over at 'David Axe Is Boring' for the low-information crowd.

Yeah, the author (Bill Carey) in the AIN piece brought up the unrelated GAO audit gripe with Pratt and Whitney, but he did so without any of the overwrought uninformed voices of 'doom' we usually have wade through -- and he included the official Program Office response (retort!) to the GAO 'report'. I thought it was a palate cleanser compared to the even-worse-than-usual-drivel that came out of  the 'collaboration' of two punk-journalistas at Axe's place titled: "The F-35 Just Catches on Fire Sometimes".

Duuuude! Heh heh. Heh. Uhhh um Heh...what was I saying?

I bet they thought it was a 'real cool' story when they wrote it. You can almost hear the snickering as they passed whatever they were 'smoking' back and forth trying to weave their contrived tale of woe:

What happened is not entirely surprising. Some personnel and testers have already raised concerns that the F-35 engine — known as the F135 — is prone to safety hazards.
As early as the 2007 fiscal year, engineers warned that a serious fire could break out if fuel leaked into the engine compartment, according to the latest annual report from the Pentagon’s top weapons tester.
By Fiscal Year 2013, tests had confirmed these fears. “Engine live fire tests in FY13 and prior live fire test data and analyses demonstrated vulnerability to engine fire, either caused by cascading effects or direct damage to engine fuel lines,” the report noted.

Hey 'Duuudes'? An engine shatting about 12 feet of metal spears through a fuel tank is going to cause a fire no matter effing what else you do.

For the record, the Punk Journalism employed oversimplifies things greatly. The  FY 2013 report says:

The first test series confirmed Polyalphaolefin (PAO) coolant and fueldraulic systems fire vulnerabilities. The relevant protective systems were removed from the aircraft in 2008 as part of a weight reduction effort. A Computation of vulnerable Area Tool analysis shows that the removal of these systems results in a 25 percent increase in aircraft vulnerability. The F-35 Program Office may consider reinstalling the PAO shutoff valve feature based on a more detailed cost‑benefit assessment. Fueldraulic system protection is not being reconsidered for the F-35 design.
The program’s most recent vulnerability assessment showed that the removal of fueldraulic fuses, the PAO shutoff valve,and the dry bay fire suppression, also removed in 2008, results in the F-35 not meeting the Operational Requirements Document (ORD) requirement to have a vulnerability posture better than analogous legacy aircraft.

Later, the report also says:

In 2008, the JSF Executive Steering Board (JESB) directed the removal of PAO shutoff valves from the F-35 design to reduce the aircraft weight by 2 pounds. Given the damage observed in this test, the JESB directed the program to re-evaluate installing a PAO shutoff system through its engineering process based on a cost/benefit analysis and the design performance capabilities. The ballistic test results defined the significance of this vulnerability. However, the test also showed that a shutoff system needs  to outperform other fielded systems. To be effective, it must trigger on smaller leak rates, down to 2 gpm versus the 6 gpm typical of other aircraft designs, without causing excessive false alarms. - The program is currently working to identify a low leak rate technical solution. The Program Office will consider operational feasibility and effectiveness of the design, along with cost, to decide if PAO shutoff valves will be reinstated as part of the production aircraft configuration. 

 Translated, the above passage says 1) the Program Office is considering its options, 2) the big thing about 'fuses' that DOT&E is all hot about would require engineering and effort to improve the state of the art because 3) the thingy the DOT&E office wants doesn't exist and are 4) beyond current state-of-the-art engineering.

I predict the JPO will develop the d*mned fuses (if they don't cost TOO much) if only to give the DOT&E their (two) pound(s) of flesh. I also note here (perennially it seems) that a '25% increase in vulnerability' gives no true perspective on vulnerability (25% more than "very little" is still "very little") nor the higher impact to 'survivability'. The DOT&E still provides no budget to the programs they write-up to help comply with their whims, and does not EVER weigh the importance of "vulnerability" relative to the "susceptibility" in considering the real metric of "survivability". This is not, per usual, a case of DOT&E actually being an authority on what is best. It a conflict in opinion and judgement between two presumptive 'authorities', of which only the JPO also has the 'responsibility'.

I'll stand with the ones who have the responsibility for draining the swamp, not the ones filming the docudrama, thank you very much.

So just who is writing this junk? 

Kevin Knodell is a professional multimedia journalist and comic writer. He writes about veterans, military history, peacekeeping and refugees for War is Boring at Medium.com. He's the current writer of War is Boring's regular comic series with artist Blue Delliquanti, as well as the writer of the comic mini-history 'How The World Forgot Darfur' with artist Keith Badgely.
From June 2014-April 2015 he was the coordinator of War Is Boring's field team in Northern Iraq. That meant supervising an international team of contributors covering the war with Islamic State, the mounting humanitarian crisis and the ongoing political struggle. The team's work has been cited by Fox News, The New Yorker, Huffington Post, France 24, and Yahoo News. He has been interviewed by Vice Germany and Rudaw English to provide insight on military tactics and new media conflict reporting.

Writer, Comic Writer, Combat Voyeur. Gets quoted by other media every now and then - got it.
At least he's a redhead and can grow a beard:

Very Van Gogh-ish

Joseph Trevithick is a "Journalist and researcher with experience using various open source and public domain resources, as well as traditional research methods (including informational interviewing and familiarity with the IRB process). Has written pieces for print publications such as Small Arms Review, and online outlets, such as a contributor to Small Wars Journal and Tom Ricks’ The Best Defense. Is also a regular contributor to David Axe’s War is Boring, hosted by Medium.com. Has been interviewed for television by BBC World, CNN International, ABC News, and Al-Jazeera English, on topics ranging from unmanned aerial vehicles to the situation in Afghanistan. Is currently working on a number of projects concerning various military topics for a range of audiences."

Also "He graduated from Carnegie Mellon University in 2006 with a dual BA in History and Policy and International Relations"

Summed up: Writer, likes history (small history from what I read), 'policy', and not just mediation -- international mediation . Gets quoted by other media every now and then - got it.

This article is a new low for Trevithick. Which is remarkable, because his old low isn't even a week old yet.

Well, he has access to a big map. Nothing says 'pro' like a big map... I guess.

Weird Days for the 'Death Spiral' Eh?

While there's really no question as to how the "Who's Death Spiral is It?" game is going to be inevitably played out from where I'm sitting, it looks like The Borg and their F-18E/F are going to get at least one more year without too much loss of altitude via the generosity of Congress. But that generosity is not being granted exclusively to just the F-18:

The vote was 278-149 in favor of the bill, which drew stiff opposition from Democrats because it uses a war-fighting account to raise defense spending next year. The measure provides $8.4 billion for 65 next-generation F-35 fighters, eight more than requested by the Pentagon, as well as $16.9 billion toward nine Navy ships.
In the Senate, the Appropriations Committee approved a $576 billion defense bill that also boosts spending on the F-35 program and adds funds to speed replacement of a Russian-made engine used to launch U.S. satellites.
The Senate bill would increase the number of F-35s made by Lockheed Martin in Fort Worth to 67 from the 57 requested in fiscal 2016. It would shift $730.3 million to buy six additional Marine models of the F-35 and add $97.6 million that, when combined with other previously approved but unspent funds, would buy four additional Air Force models, according to the bill report.
The Senate measure for the year that begins Oct. 1 would also add about $978 million for 12 F/A-18 E/F Super Hornet jets made by Boeing Co., rejecting the Pentagon’s plan to end Navy purchases of the plane.

Everyone's a winner!

The F-18 buy doesn't bug me all that much. Yeah the Taxpayer pays (again), but it may be worth it, if only as a wedge to help keep LM's F-35 on the cost reduction slope, And its not as if the Navy isn't going to use up the F-18E/Fs they already anyway even after they field the F-35C. Once the Navy catches up to the AF in fully exploiting LO aircraft however, those new F-18s may last years longer than planned: because they just won't be used all that much once it happens.

Speaking of Cost Reductions. 

Evidently the F-35 unit cost is ALREADY dropping due to LM's  ‘Blueprint’ To Drive Down F-35 Costs proactively, instead of just relying on Economic Order Quantities to survive Congress' penchant for micro-management and irrational change:

Initially, the manufacturer expected that it would see the first cost savings during F-35 low-rate initial production (LRIP) lot 9, which Lockheed Martin and the DOD were negotiating at the time of [Lorraine] Martin’s presentation in mid-February. But it realized early benefits while producing LRIP 8 airframes, cutting about $260,000 from the cost of each of 43 fighters that it will begin delivering in 2016. “So that’s not chump change,” Martin declared. “I rolled that cost savings into the offer I made to the government when I negotiated the contract,” which the parties signed last November...

...At the time of the LRIP 8 contract award, Lockheed Martin said the average unit price of airframes for the three F-35 variants was 3.6 percent lower than the LRIP 7 price. The company reports that the LRIP 8 cost of an F-35A for the U.S. Air Force without its F135-PW-100 engine was $94.7 million. The price of an F-35A with its engine was $108 million, which was $4 million lower than Lot 7 prices, according to the Pentagon’s F-35 Joint Program Office (JPO).
Martin said the manufacturing improvements her company is implementing could knock another $780,000 from the price of LRIP 9 jets. Ultimately, the blueprint’s goal is to deliver an F-35 with an engine for $80 million in then-year dollars, accounting for inflation. Martin has generated news by saying the price could be even less. “If this works, and we have confidence that it will, [the government is] potentially willing to invest on the tail end $300 million. With these two sets of investments, that’s what gets us down to under an $80 million aircraft,” she said.

Sweet!

Norway's First F-35 Leving 'Major Mate' for Final Assembly

Let's see what the URF cost of the 2016 F-18E/F buy is going to be in then-year dollars is when the next SAR covering the buy is  released. Should make an interesting comparison. At some point in time the mouth-breathers are going to have deal with the reality and stop amortizing F-35 sunk costs over future buys, but it won't be soon. I think they will want to pretend a little longer, if only because there isn't anything else big to b*tch about.

The One DOT&E, er DoD SAR Quote You Probably Won't See Anywhere Else

Now with Don Bacon! 
(As in Corrected, Updated and Bumped with Hat Tip to Same)

Don't expect the Punk Journalists, Loyal Babblers, or Faux Reformers (abetted by Punk Journalists) to bother with putting proper perspective around all their little doomsday accounts of what is going on inside the F-35 program. Remember, its all about either trying to kill a program and/or coming up with enough rent money. "P.A.C.E." is the vehicle that they'd drive off the cliff before they'd ever move away from it.

So there is one DOT&E DoD Selected Acquisition Report (SAR) quote out of all the reports and testimonies that comes out of the unexpurgated December 2014 (for 2015) DOT&E Report DoD SAR that I don't see anyone pushing out to the uneducated masses anytime soon. It is the final paragraph of the report's Executive Summary, Page 10:

In summary, the F-35 program is showing steady progress in all areas – including development, flight test, production, maintenance, and stand-up of the global sustainment enterprise. The program is currently on the right track and will continue to deliver on the commitments that have been made to the F-35 Enterprise. As with any big, complex development program, there will be challenges and obstacles. However, we have the ability to overcome any current and future issues, and the superb capabilities of the F-35 are well within reach for all of us. 

Everything else in the media that surrounds the F-35/DOT&E, DoD SAR, GAO, blah ,blah, blah, reportage is about either rallying the mouth-breathers or herding the sheep.

About the Update: I had meant to identify the report I linked to as the SAR, but let myself get in a hurry and used the incorrect reference at the link that originally led me to the document instead. My 'bad', but it doesn't change the essence of the post or the point either. This update exists because I loathe inaccuracies, even mine and no matter how they are identified.
If anything, the quote is more relevant to my point coming from the SecDef Office SAR than the DOT&E annual report:

F-35 Transonic Acceleration vs. an F-16 Block 60 'Hot Rod'

UAE's Block 60 in early livery
over the Arizona Desert (original source)

Updated (at bottom of post) and 'bumped'

'Tim A,' in the comments of my last series of posts covering F-35 KPPs and 'Transonic Acceleration', piqued my interest in doing a comparative analysis of the F-35A's transonic acceleration KPP against a hypothetical, lightweight Block 60 F-16E that LM built for UAE. We can only 'estimate' and in the case of the F-16E/F the estimates can, I believe, be regarded as fair approximations since they are based upon F-16 Block 50 data in hand. Excursions away from the F-35 KPP data will be more presumptive, but we will not venture too far away from 'firmer ground'.

To do the comparison that we want to do, will first require us to make some reasonable assumptions (and remember they are assumptions) concerning the Block 60 aircraft and how they differ from, or are materially the same as, the more well-known Block 50 aircraft.

Major Differences between Block 50 & 60 Aircraft 

There is little 'hard' data available beyond certain basic information on the Block 60 configuration. The United Arab Emirates funded the development of this version in its entirety, and there is no 'Dash 1' manual in the public domain (that I am aware of) that could provide us with the 'authoritative' source for the information we seek. In any case, the factors most important to our discussions will be the establishment of an acceptable aircraft empty weight, and evaluation on what effect the Block 60's higher thrust engine (32,500 lbs vs 29,000 lbs of thrust in afterburner) would have on overall performance.
A major factor that might warp our evaluation of the Block 60 against the F-35A KPP performance--if we let it --would be quantifying the effect of wave and other drag differences between F-16 Block 50 and Block 60. My approach will be to do so in a manner that passes the "Reasonable Man' test.
As the purpose of this exercise is to get an idea as to  how well the 'future' (i.e. F-35A) stands up in comparison to the 'present' (aka F-16 Block 60), I intend to give the Block 60 performance every reasonable benefit of the doubt in surveying the drag differences between the Block 50 and Block 60. I choose to do so in part because I expect the non-wave drag differences between the Block 50 and 60 aircraft will be seen as less important compared to the wave drag contributions. (This should be seen as reasonable, if only because of the relative contributions of the factors proportional to the drag total). I do not expect to be able to characterize the effect of the differences exactly, but we should be able to identify the differences and their effect within a comparatively narrow range with the data in hand.

Block 50 vs Block 60 F-16 Drag and Weight Differences

For our earlier F-16C Block 50 comparison to an F-35A KPP configuration we used this Block 50 configuration:

F-16C Baseline: Full Internal Fuel, 2 AMRAAMs on wingtip launchers and full 20mm load.

The table above was just for a 'baseline' configuration. The source document for the data actually provides us with a wealth of information concerning many different F-16C/D weight and drag configurations that effectively define the F-16C/D transonic performance across a wide region of weight/drag possibilities: 

F-16 Block 50 Drag Count and Weight Differences.
Note that at low drag counts the differences in weights have a greater impact on acceleration times than the differences in drag, In particular, the increases in acceleration time due to a DI below 30 are small (interpolation looks like ~5-6 secs at 32K lbs)

We'll use this information to characterize the effect of the Block 60's external configuration and weight on its total 'drag'. 

For this exploration, we have selected a slightly "better armed" F-16E Block 60 configuration: 

F-16E Block 60 Configuration: Full Internal fuel load not includng CFTs,
Empty CFTs, 4 AMRAAMs and full 20mm load 

The four AMRAAM load was suggested by 'Tim A,', though I kept the CFTs empty because I wanted to keep the Block 60 configuration reasonably light.

The drag differences between the Block 50 and Block 60 F-16 configurations are reduced to the effect of the Block 60's greater total weight and increased drag profile. For the drag numbers in the selected Block 60 configuration I'm using the HAF F-16 manual and an article on CFTs found here. The CFT article mentions specifically the CFT set as "12%" of 300 gallon tank, but that is a general statement that may be the average drag reduction for the 300 in the subsonic region. I selected using 4 as the estimated DI for the CFTs for the transonic region, but even if it is less (perhaps '2') the difference between DI totals of 22 and 24 won't be seen in any guesstimate we can do. In addition, I have elected to treat the Block 60 basic airframe drag the same as the Block 50 in spite of the fact the Block 60 is designed to use and carry sensors/systems that are specific to the type.

Block 50 and lower pods on the left, Block 60 targeting system shown
on the bottom right. Some of the extra weight of the Block 60
comes from carrying an internal infrared search and tracking system,
of which only the FLIR ball can be seen just ahead of the canopy

These Block 60 systems, while they are no doubt 'lower drag' than the Block 50's 'add on' LANTIRN pods etc, they are also not "drag free". This is especially treu of the Sniper XR-derivative targeting system installation shown above. To give the Block 60 every advantage in the quantitative analysis, I choose to ignore the drag of the Block 60's unique installations. I do so for a couple of reasons. First, I doubt it will make as much 'drag difference' as accounting for all the weights involved, and second there is photographic evidence that while the Block 60-specific targeting system installations were initially expected to be carried all the time, in practice it hasn't always the case(Google "Block 60 F-16" and check out the photos). We'll just keep the 'drag factor' of these systems in the back of our minds going forward.

Block 50 vs Block 60 F-16 Engine & Thrust Differences

F-16 Block 50 Engine (source)

F-16 Block 60 Engine (source)

The differences between the Block 50 F110-129 engine and the Block 60 F110-132 engine are slight, but the -132 engine yields 2600 more pounds of thrust at sea level (standard day):
The key differences between the two engines that drive the increased thrust for the -132 variant aren't relevant to our analysis but for the sake of completeness, let us observe that the -132 has a slightly higher airflow than the -119, and that is at least partly due to the ever-so-slightly lower bypass ratio (more 'fast hot' air) for the -132 design. There are also some 'efficiency' improvements in the -132, some of which can be retrofitted to -129 engines for better durability if the users want to pay for the 'goodness'.
Normally, I would be loathe to try and extrapolate what a difference in engine thrust between planes would mean to the relative transonic acceleration performance, but given we are looking at essentially the same aircraft at different weights (and thrust to weight ratios), I think we can make a reasonable accommodation for the effect (on Block 50 acceleration) of the the extra thrust based upon looking at comparable Block 50 thrust-to-weight ratios. We can-- and WILL!-- apply that analysis to arrive at a fairly narrow region of impact of the higher thrust to the Block 60's transonic acceleration performance estimates.

Deriving an Estimation of F-16 Block 60 Performance Based Upon Block 50 Performance

We'll do this in a two-step process to bracket the likely transonic performance of the Block 60 compared to the Block 50. It doesn't make a difference in what order the process is applied, but we'll start with the simplest to explain first, and we'll just keep the F-35A KPP performance in sight as a sort of benchmark for now.

Step A: The Weight/Drag Impact 

As mentioned earlier, we can use the HAF T.O. GR1F 16CJ 1 1 Change 8 document containing the max acceleration performance data for the Block 50 to derive an approximation of the effect of the Block 60's weight and drag relative to the Block 50, We've approximated the drag index of the Conformal Fuel Tanks and added the known drag index of the Block 60's launchers and extra (2) AMRAAMs to arrive at a drag index 'upper' of  24 over a baseline Block 50. As this drag index is approximately halfway between a known DI=0 and DI=50, and the Block 60's selected configuration weight of 31,503 lbs is slightly lower than the the Block 50 32K lb configuration, the effect of weight and drag differences ALONE would indicate a transonic acceleration time of about 53 seconds (plus or minus). This is a performance better than the Block 50 at 32K lbs (DI=50) but not so good as a Block 50 at 28K lbs and with a DI=50 (obviously).

Note: This step would have been a lot easier to show/follow if the Block 50's DI=0 performance at 28K and 32K lbs were 'feasible' configurations. We could have just bracketed the DI=0 and the DI=50 values for a 32K weight.         

Estimating the Effect of Block 60 Weight Drag ONLY based upon Block 50 data. 

As we observed earlier within the 'F-16 Block 50 Drag Count and Weight Differences' chart, large aircraft weight difference have more effect on acceleration times than Drag Indexes when Drag Indexes are low:

Effect of Low Drag Count at relevant weights

Step B: The Impact of the Engine Difference

This step is a little more involved than the other. We again will rely on using the Block 50 data from HAF T.O. GR1F 16CJ 1 1 Change 8, but in estimating the impact of this factor we have to normalize the data for the Block 50 before applying it to the Block 60.

In the first section of the following graphic, I have charted the relative thrust-weight values for both the Block 50 and Block 60 aircraft. Notice how close  both the absolute values and the relative step functions are for the highlighted ratios shown for each F-16's Block data. The highlighted Block 60 ratios and step functions are slightly lower than the Block 50's but still very close.

If we ignore all other differences between the ircraft and assume acceleration differences are purely a matter of thrust to weight, and  generously assume all increased thrust-to-weight for the Block 60 translates proportionally into better acceleration at every weight AND look at the acceleration times for the Block 50 configurations between weight steps, we can express those step 'time deltas' for the Block 60 as a function of the ratio of  Block 50/Block 60 thrust ratios times the time deltas for any selelcted drag index. If that sounds confusing, it is because it is...without a spreadsheet.

To simplify, for this specific example I divided the 'Raw' Block 50 Thrust-Weight Ratio for the 28K weight by the 'Raw' Block 60 thrust-Weight Ratio for the 32K weight (1.0357143/1.0156325). I then  treated the Block 50 28K DI=24 acceleration time shown in the 'Normalized for Drag' portion of the chart below as being solely a product of thrust-to-weight, multiplied the Block 50 acceleration time for the 28K weight (44 seconds) times the 'ratio of thrust ratios used.

Stated more clearly without an audit trail: We assume the heavier block 60 will accelerate like a Block 50 at the same thrust to weight ratio. 

I am giving the Block 60 further benefit of the doubt by not accounting for the higher weight, but that's OK!: we're estimating remember?

Plotting the Step B as standalone estimate on the same graph with the Part A standalone estimate we find:

Estimating the Effect of Block 60 Weight Drag ONLY (A) and Block 60 Thrust to Weight ONLY (B), based upon Block 50 data. 

Obviously the actual Block 60 performance should fall somewhere between the outcome for each as independent factors:

Block 60 Transonic Acceleration Estimate: A Near-32K pound Block 60 with 4 AIM-120s accelerates like a Block 50 F-16 DI=50 at 28K Lbs.   

So in the end, the big advantage of the Block 60 aircraft appears to be the increased range and better/equal performance at a slightly higher weight than the Block 50. Nothing to sneeze at, but nothing too surprising either.

But HEY! What about the Block 60 in comparison to the F-35A KPP performance? 

We've covered the whole F-35A configuration setup already elsewhere. The big thing we do not really 'know' still is how much fuel is aboard the F-35 for the KPP measurement. We DO however understand that the KPP was written based upon a load of two 2K Lb JDAMs and 2 AMRAAMs carried internally. If we simply swap the two JDAMs for two more AMRAAMs the F-35A's weight would be about 4,000 pounds less (Most 2K Pound JDAMS weigh more than 2K lbs with the kits).

This F-35A KPP configuration performs almost exactly the same as a 36K pound Block 50 with a DI=50, the removal of 4000 pounds of weight should yield performance approaching that of a 32K pound Block 50 with a DI=50:

If the F-35A in an A2A configuration wants to match this F-16 Block 60 A2A configuration in transonic acceleration, it can probably just dump some fuel, or more likely simply 'unload'.  Conversely, in an A2G configuration similar to the F-35A KPP setup, the F-16 Block 60 would probably fair not so well against the F-35A KPP configuration

I'm not even going to plot this one (DI=74? Yikes!)

Housekeeping: Note that the Block 50 data in hand starts the acceleration run at Mach .79 and not the Mach.8 used for the F-35 KPP performance. That's OK! At the weights we are looking at, this translates to about 1 second or less difference: well within any margin of error.

*********************************************************

Update 29 April 15: About the presumed KPP configuration

(This ‘Update’ driven by conversation in the thread, because covering all the aspects of a complex subject in a comment thread is futile)

It doesn’t really matter if the F-35A configuration for the transonic acceleration KPP includes 2 JDAMs or if the JDAMs have already been dropped. It really doesn’t matter for three fundamental reasons, only one of which we’ve discussed in any detail.

First Fundamental Reason: Ambiguity of KPP Configuration

The KPP configuration and weight ‘is what it is’, and all our analysis has been focused on the relationship between those factors that affect transonic acceleration, and how (and how much) changes to those factors affect performance.

We do not ‘know’ the payload carried for the KPP values for any of the explorations we’ve made, and I’ve been comfortable in doing these parametric examinations using the assumption that the internal payload for the F-35A consisted of (2) 2K JDAMs, (2) AMRAAMs and a nose load of 25mm cannon rounds. Unlike an F-16 or any other aircraft that carries bulk fuel and weapons externally, it really didn’t matter what the F-35 was carrying internally from a drag POV except as in how whatever weight the F-35 was bearing increased the drag due to lift. While I used the assumption that the plane was carrying the JDAMs, We’ve never asserted or implied a total F-35 weight as the basis for the estimates. We have seen that at whatever the baseline weight basis is, the F-35A in its KPP configuration (whatever that is) accelerated from M.8 to M1.2 very much like an F-16 Block 50 at 36K lbs and a Drag Index =50.

I then posed a ‘what if’ scenario where the F-35A was 4K Lbs (or so) lighter to estimate performance at an “X”-4K pound F-35A. I took away the hypothetical 2k JDAMs because they were convenient to quantify. This is acceptable because, as I have mentioned many times, these analyses are about gaining an understanding of the factors involved and their impact/effects.

The data in-hand can’t be used to prove anything either way, it can only point to ‘possibilities’.

I am completely agnostic as to whether or not the F-35A KPP includes carriage of the JDAMS. If, as it has been suggested by ‘Tim A.’ in the comments that the KPP weight of the F-35 for the transonic acceleration performance does NOT include the 4K+ of JDAMs, I am good with that. BUT, I still cannot make a claim either way with certainty. If one takes at face value [1] then-Commander Bowman’s statement that

“The fuel levels and payloads at which maneuverability is calculated differs for each variant but generally focuses on a post-weapons release payload and fuel state at 50% of the required combat radius”

…do we assume that the transonic acceleration KPP falls within both the “post-weapons release” AND “50% fuel” ‘generalities’, or just one? Or the other? Or neither?

We don’t know. 

Looking at the key table in the Bowman paper….


We see two distinct CTOL (F-35A) loadouts specified for two KPPs in the footnotes. Are these the only two ‘possible’ exceptions to the “general” configuration to which Boman refers, or are they the ONLY exceptions? Are they just configurations that Bowman highlighted because he thought they were important to his arguments? We don’t know.

I’ve always been struck by the reference to the 2 empty external tanks in the first footnote, given the F-35 at this time does not carry external wing tanks and to-date they have not been seen as ‘value-added’ enough to be pursued by the program (an interesting topic for another time), but of interest to our discussion here is the second footnote as it relates to Bowman’s introduction to the table.

If it is worth mentioning in the footnote that “60% of internal fuel load” is carried as an exception to the ‘general’ rule, why would it be worth mention that the JDAMs had been “jettisoned/released” as if it were not part of the ‘general’ rule as well? I believe there is enough incongruity between the text and the table to prevent anyone from asserting the F-35A’s transonic acceleration KPP configuration MUST include or exclude JDAMs OR must be at 50% or 60% (or ‘n%’?) fuel [2] carried. This ambiguity is the primary reason I resisted establishing a baseline weight for the F-35A in doing the acceleration modeling and analysis. (Observant readers will note the only time I quantified F-35 variant weights in looking at the F-35 acceleration performance was when we examined possible discriminants between variants as drivers for variations in acceleration times.)

To go beyond the point that we have already gone can only add more uncertainty. Which leads us to Fundamental Reason #2

Second Fundamental Reason: The F-35A Baseline Design Itself is NOT Final

And the ramifications of this point are HUGE. Much of it relates to what will be the final weight/drag of the aircraft itself, but some of it relates to how the ‘books’ are being kept that prevent any definitive performance statements until SDD is complete (see Reason #3).

The weight uncertainty factor we touched upon under Reason #1 looms larger than many people might realize. We can assume all KPPs are based upon all or part of a fuel load required to achieve some unknown-to-us mission utility, objective and/or point, so weight is a factor in all KPPs.

Aircraft total weight will be driven by Aircraft Empty Weight, Fuel Weight, and Payload Weight. To meet ANY KPP objective listed, changes in the basis for Aircraft Empty Weight will have a compounding effect on total weight; creating a fuel-weight ‘spiral’ that can be positive or negative. The lighter or heavier the aircraft, the more or less fuel weight will need to be carried, and reciprocally, less or more payload can be carried. For every pound of empty weight added, how much more fuel weight is needed or how much payload weight will be affected? (Answer: “It depends”.) Whatever a percentage of fuel load weight used for each KPP, and the primary driver for specifying a max weight for each variant appears to vary [3], it can only be of importance as part of a total weight (assuming all weight is carried internally for all KPPs allowing us to ignore external drag ‘adders’), and what we do NOT know about this value and how it relates to performance parameters far outweighs what we do know. Keep this in mind going forward, as the first thing that we DO know about the F-35A’s empty weight is that it is currently below design objectives (DOT&E FY14 PDF):

Weight management of the F-35A is important for meeting air vehicle performance requirements and structural life expectations. These estimates are based on measured weights of components and subassemblies, calculated weights from approved design drawings released for build, and estimated weights of remaining components. These estimates are used to predict the weight of the first Lot 7 F-35A aircraft (AF-72), planned for delivery in August 2015, which will be the basis for evaluating contract specification compliance for aircraft weight.
-- According to these reports, the program has reduced weight by 16 pounds in CY14 (from January to October estimate). The current estimate of 29,016 pounds is 355 pounds (1.2 percent) below the planned not-to-exceed weight of 29,371 pounds.
-- The program has demonstrated positive weight management of the F-35A over the past 38 months, showing a net loss of 123 pounds in the estimates from August 2011 to October 2014. The program will need to ensure the actual aircraft weight meets predictions, as well as continue rigorous management of the actual aircraft weight beyond the technical performance measurements of contract specification in CY15 through the balance of SDD to avoid performance degradation that would affect operational capability.

An empty weight that is 355 pounds lower than the modeled KPP weight implies a much larger weight in fuel that does not to be carried to achieve the F-35A’s combat radius (or ‘60%’ mission radius/endurance distance/time). JETA-1 fuel weighs 6.71 lbs per gallon. How many pounds of fuel can be left behind by not having to carry 355 pounds of dead weight over 1200+ nautical miles out-and-back? We don't know. the uncertainties are certainly adding up.

While the AF-72 aircraft is the target point that is “the basis for evaluating contract specification compliance for [F-35A] aircraft weight”, we also do not know how much margin is in the “planned not-to-exceed weight of 29,371 pounds” target weight. I’ve seen indicators[4] that prevent me from completely assuming the weight targets are the weight assumptions used for KPPs. If the targets aren’t the limits, then there is further weight margin that the KPP model may not be accounting for in performance modeling. I personally wouldn’t assume this to be the case, but we don’t know. Time will tell.

Third Fundamental Reason: The KPP Ground Rules and Assumptions and/or their Impacts aren't fully known or accounted for either.

The ‘unknowns-unknowns’ here might outweigh any factor we have examined in trying to compare an F-35A to any legacy aircraft. The 'known-unknowns' are bad enough. Example? We know the KPPs are based upon a ‘pessimistic’ engine performance with 5% thrust and fuel efficiency degradation (Ref #8 here). We do NOT know what impact that factor has on the overall ‘standard’ aircraft weight or acceleration, but just as important, we do not yet know if that the ‘engine of record’ in the models is the original 40K Lb thrust engine, or an engine with the newer 43K Lb thrust rating. So, what else do we NOT know about the model GR&As?

Finally,

I don’t lose any sleep over the F-35A’s transonic acceleration because in the end it still gets back to the fundamental fact that you can always just ‘unload’ the plane to shed all that wave drag due to lift… if you so desire. Using such a technique, the F-35A should be able to run away to, from, or with any current or future aircraft through the transonic region unless that other aircraft is heavier AND with a higher Thrust/Weight ratio, and there are always other ways to deal with such contingencies (TANSTAAFL). I’ll THINK about getting concerned when the JPO and users get concerned.

Notes:
1. While I used the Bowman paper data, I put no weight on what was discernible as Bowman’s own analyses or observations surrounding the data. I treated the paper in this way, because I cannot divine if his positions/opinions come from ‘fact’ or from his ‘views’ on the facts: especially since I see several assertions/conclusions (unrelated to any of the KPP discussions so far) within that I know are erroneous--if only through their over-simplification. Further, Air Command and Staff papers tend to be advocacy papers and Bowman’s certainly falls into that description. I know enough about ACSC papers to know that they are just like almost all college papers, they are usually done for a ‘grade’ and not posterity. False data can get you a failing score in ACSC, but I’ve not seen evidence that faulty reasoning will-- unless you argue it ineffectively.

2. As an aside, if I HAD to pick a fuel quantity for the transonic KPP I would pick a value above 50% fuel on the assumption that the operators would desire at least 50% fuel on hand after a transonic dash, presumably to get to or get away from a fighting position.

3. For the F-35B model, the obvious weight constraint beyond those affecting range, acceleration and turning is Vertical Lift Bringback (VLBB) weight. For the F-35C, the Maximum Carrier Landing Weight is a driver as well as whatever weight will be essential to NOT bust the approach speed limitations.

4. One example is a chart online (that is marked US/FOUO, so I won’t post or link to here) shows the F-35C’s Weight Status in 2012 with a 'target' weight well below the key Carrier Landing Weight limit.

The F-35 and the Infamous Transonic Acceleration Change

Part 3 : Updated and Bumped

(Part 1 here: Part 2 here, and 'Bonus' Block 60 Comparison Here)

I'm still working on the F-35A vs Block 60 F-16 comparison, but wanted to add a reference to a comment I made at Breaking Defense in response to one 'Peter Goon': a former FTE (best known as a talking head for Air Power Australia ). I'm repeating it here because for some reason, the graphics accompanying my response did not post, and one is an update of a chart shown already in this series.  Mr Goon dropped a series of snarky comments, any of which can be discarded, but none so readily as this one:

RE: Q: How does an aircraft that takes over 60 seconds to accelerate from 0.8M to 1.2M at 30k ft ISA have "at least" the maneouvrability of a Block 50 F-16C which does this in less than 30 seconds, with 4 missiles on board?

My response reads thusly:

Well Skippy, your first big problem is that the only F-16C Block 50 that can go from M.8 to M1.2 in "30 seconds" can only carry two missiles and....its about out of fuel.

Your second big problem is that you are comparing your infeasible F-16 loadout with an F-35 KPP configuration that is carrying 60% (of a much larger capacity than the F-16) fuel load AND 2 tons of bombs.

To answer your question more fully, and as a object lesson to others that it is YOU who are really pedaling the "indifference to reality" with hyperbolic nonsense, the F-35A at KPP weights and loadouts SPANKS the Block 50 F-16 in transonic acceleration for all but at the very lightest weight/drag combinations identified in the F-16's operating manual.

I dropped two graphics with data extracted from the Hellenic AF Block 50/52 Change 8 Operators manual, but they didn't 'take' for some reason. First, the F-16 Block 50 basic weight/drag data:

This is the heaviest a Block 50 F-16 can get without adding drag by hanging stuff off the outside 

...and then an updated table (data and comment added for clarity only: no existing data changed) of the Block 50's transonic acceleration times:

Only at the lowest weight/drag combinations can a Block 50 transonic performance best the F-35A KPP configuration. Remember the F-35A is carrying 60% internal fuel AND two 2K Lb JDAMs. 

Conclusion?

YES, the F-35A has:

  "at least" the maneouvrability of a Block 50 F-16C. 

Deal with it.

Original Post, as posted on 1 March below this point...... 

KPP Requirement or no, ‘What If’ the F-35 will someday really need to get rid of all or part of extra seconds in the new KPP enroute to Mach 1.2?

(Part 1 here: Part 2 here, and 'Bonus' Block 60 Comparison Here)

The F-35 Transonic Acceleration KPPs were ‘changed’. This change was almost immediately decried far and wide as a failure by the ill-informed and self-serving critics. I’m certain some have forgotten or missed the discussion in Part 1 where I referenced the DoD documentation describing the process by which KPPs are established, and changes are made, and that they are only changed if the changes are validated as being operationally acceptable. I’m certain others will miss the references in Part 2 where it was highlighted that they changes were always going to happen, if only because you cannot violate the laws of physics. (Those people may be sputtering at their computer screen soon if they aren't already). That the F-35 KPP changes were implemented at all proves the changes were acceptable by those responsible for the integrity of the requirements and supporting system engineering process.

This post and series is not for those people.

It has been for people who want to understand more about the changes and their ramifications. Agreement or approval by me or anyone else as to the acceptability of these KPP changes is irrelevant. The agencies to which they are relevant have already decided.(Right about here those ‘other people’ would mentally register a need to utter a Circumstantial Ad Hominem against those responsible that when you strip away all the unsupported assertions, logically translates into little more than “those people are the experts, what do they know?...oh and “they must be lying!” or “what are they hiding?”)

BUT!... probably, someday, someone flying one of the F-35 variants is going to REALLY need to accelerate M.8 to M1.2 as quick as the original KPP specified or even more quickly (just not often enough to pursue it as a KPP). Truth be told, there’s probably going to be a time or twelve where somebody is going to wish ‘instantaneous’ translation to Mach 10, but you have to draw the line someplace within the laws of physics.

IF there is some operational need to shave all or part of 8 seconds (or the longer times for the other variants) going from .8M to 1.2M, can it be accomplished? If so, HOW would it be done, and is the remedy needed so onerous that it will adversely impact the F-35’s viability or operational utility? With the F-35A needing only to overcome 8 seconds, the program office could have easily just specified a lower weight to accomplish the feat, and a checklist item added to the effect of “if you want to do ‘this’, then ensure fuel and weapons on board do not exceed X lbs”. But as fuel on board at a mid-mission point tends to be a valuable commodity, and weapons carriage is a fighter aircraft’s reason for being, I presume everyone can see why the users, JROC and program office didn’t take that route.

“One Weird Trick”

If, by chance, “8 seconds” is a big deal, even for an aircraft with a ‘greater initial acceleration than an F-16’ and it still means those 8 seconds crossed some breakpoint minimum needed operationally, then the good news is it is rather easy to accommodate. In fact, fighter pilots have been using ‘this one weird trick’ (Man, I hate those ads) for decades to squeeze extra acceleration out of the transonic region.

It’s called ‘Unloading’

Hat tip to Pat ‘Gums’ McAdoo, USAF Lt Col (Ret), at F-16.net for first reminding me of this ‘way back when’:

“RE: transonic accel....... I'll bet that the profile was st-and-level and then gofor it. We who have done it know that all ya gotta do is reduce AoA by lowering the nose a tiny amount and shazaam!”

You can also bet any future opponent that the F-35 runs into WILL also be doing the same thing. Sometimes ‘unloading’ will be the best thing for a pilot to employ, sometimes something else will be the best thing to do. Aeronautics has advanced to exploit the medium to its maximum. There is no magic airplane that does everything better than any other airplane within each generation or two: there's always a 'catch'.

Unloading the wing during an acceleration run through the transonic region pays off in increased acceleration (or reduces the decline of acceleration if that is all that is desired) immediately. It is also the key part of employing the Rutowski Profile (Ref #10 in Part 2) in reducing climb times for the same reasons. When a pilot completely 'unloads' the wing, all of the wing wave drag coefficient contribuion due to lift goes to zero, and the aircraft ‘sinks’ (altitude decreases). This is a relatively slower rate of descent compared to an actual ‘dive’, by the way. But a dive is also an option for even greater acceleration, and as Shaw observes (Fighter Combat, p. 407) it is even more effective the heavier and ‘cleaner’ an aircraft is-- assuming the dive does not take the aircraft past its structural limits. When that much wave drag suddenly disappears, the acceleration rate increases dramatically (Shaw recommends a “sharp pull-down” to a dive attitude then an ‘unload’ as particularly effective). Higher acceleration rates are like compound interest: the more you have earlier, the more the distance you cover and the more speed you have at the end: If the wing is unloaded early in a run when acceleration rate is already high but late enough that the aircraft is near Critical Mach, the time the plane would need to be unloaded might be exceedingly small for an F-35A to achieve 1.2M those eight seconds faster. It might help people to be able to visualize how little difference there is between M.8 and M1.2 at 30K feet if we use a graphic (we're keeping the numbering of figures as beginning in Part 1):

Figure 20: Every tenth of a Mach is about 40KIAS at 30K ft Altitude

An eight second difference for the F-35A in all probability translated into achieving something like Mach 1,1-Mach 1.18 in the original 55 seconds. That's small potatoes as far as overall speed goes. 

Here’s the example of a straight wing drag profile shown earlier:

Figure 21: Typical Drag Curve for a 'Loaded' Straight Wing 

Now, here’s a representation of what the ‘straight wing’ drag curve looks like if unloading the wing reduces the wing wave contribution by a conservative 40%:

Figure 22: Typical Drag Curve for an 'Unloaded' Straight Wing 

The total peak drag coefficient in this instance is reduced by 25%. Observe in the next figure that the peak drag coefficient ‘unloaded’ at around M1.1 is about the same as just before Mach 1 ‘loaded’, and that even in the typical Critical Mach range for fighter aircraft between M.8 to M.9 (Shaw, “Fighter Combat”, Pg. 399) the drag coefficient is reduced. 

Figure 23: Straight Wing Drag, Loaded vs Unloaded

IMHO, the F-35 Critical Mach Speed, like most advanced fighters, should be well into the upper half of that range IF the performance measures in the Bowman paper are to be believed (We’ll get to that in a moment). 

The actual amount of drag reduction will vary depending upon the total aircraft design (and remember it will also vary by airspeed and altitude). Shaw’s “Fighter Combat” provides a convenient graph highlighting the increases in acceleration that can be expected at different altitudes over a wide speed range for legacy aircraft. It is modified here to illustrate the altitude and Mach range of interest:

Figure 24: Typical Benefits of Unloading on Acceleration (Original source as noted, modified by Elements of Power)

We see in Shaw’s chart that for legacy fighter designs flying from .8 Mach to Mach 1.2, unloading increases the acceleration rates between ~17% at M1.0 to as much as ~20% at Mach 1.2 and ~25% at .8 Mach at the 30K ft KPP altitude (Ref #9). This appears consistent with what we would expect from the differences in the drag curves shown in our examples. It should also be readily apparent that both the F-35B and F-35C could employ the ‘unload’ technique in the same manner as the F-35A. Obviously, the F-35B would only need a small ‘bump’ compared to the F-35C. The smaller the time/speed difference needing to be closed, the more flexibility on timing and duration is available for the pilot to choose when and how long to ‘unload’.

Figure 25: Unloading and/or Diving to Achieve Original KPP times.

The F-35C’s obviously much greater wave drag due to lift than the other two variants (expanded upon in Part 2) also means it would just as obviously benefit MOST OF ALL from the unloading technique. If a dive would be necessary for the F-35C (as the ‘worst case’) to meet the old transonic acceleration standard, it could be able to carry that acceleration beyond 1.2 to perhaps even M1.6  (F-35 Max Speed in level flight. We do not know what the 'never exceed' speed is, so we’ll stick with what we know the F-35C can do. If ending the acceleration run at the same altitude (30K feet in the KPP) is important, the F-35 pilot can accelerate beyond M1.2 and so after climbing at the end of the run, trading smash for altitude, the plane is still flying M1.2 or better.

This might be a good time to interject the observation that if there was ever evidence the original KPPs were established before the aircraft design was even undertaken, it is the original common KPP of 65 seconds for the F-35B and F-35C: two airplanes with vastly different weights and wing areas. This tells me the trade space for the F-35C design might not have been fully understood when the Navy laid down the requirements or the KPP really was a 'let's see what we can get' figure.
We should also note here that the KPPs were/are against a predicted weight standard and that all indicators are that the predicted weights are being beaten, with all variants coming in (for now) below the modeled weights used for the KPPs.  Those lower weights mean lower wave drag to begin with, and in turn better transonic acceleration.   

Shaw asserts that unloading for best transonic acceleration is done close to ‘Critical Mach’. Bowman (Part 2 Ref #9) identifies the F-35A KPP threshold for max speed at 30K ft altitude without afterburner at >.96 Mach. This speed cannot be too far above or below F-35A Critical Mach because “at speeds faster than the Critical Mach number the drag coefficient increases suddenly, causing dramatically increased drag”. Afterburners (and/or unloading) would soon be required to go any faster once Critical Mach is reached.
Bowman BTW, is now a Navy Captain, and as far as I know continues to NOT be an F-35 'fan'. I'm still hoping for some karma backlash that will tie him to the F-35 program as a developer or operator, just for the entertainment value alone.   

Conclusions?

Other than changing the KPPS evidently was not a 'big deal', there's not much to conclude: just a lot of open questions remain.
That the program was warning far ahead of the KPP change that the spec was unrealistic (Ref #3 and #4 in Part 2), makes the initial acceleration KPP looks more like it was a ‘show us what you can do and we’ll revisit the issue later’ placeholder. An entirely likely possibility is that as the program matured, different advantages were seen in areas of aircraft capabilities that shifted design emphasis to 'someplace else'. A KPP may be set based upon an assumption of X capability would require KPP X to be one thing, and then as the design matures, and operational concepts evolve or even threat perceptions shift, it becomes apparent that X capability isn't as important as Y capability, which if is addressed would require more or less out of the KPP X.  

Examples? Program news over the years seemed to talk a lot about range and carrier approach handling as being 'big deals'. Did range become more important than acceleration? If so, fuel could have been added which increased weight and that reduced acceleration. For the C model, did the Navy decide a bigger, higher drag wing meant fewer carrier landing mishaps? It is also entirely possible one or more of the variant KPPs started simply as a wish-list item.

We've heard before about he F-35 KPPs being based upon aerodynamically 'clean'  legacy aircraft specs. Was that a 'miss' where the initial KPP-setters failed to recognize the physics involved, or they did recognize it but since there was no design to evaluate at the time, they let it go: leaving it as an admirable goal but also knowing the KPP could always be changed later? That last explanation makes most sense to me. I've dealt with the acquisition system bureaucracies for decades, and that kind of development  seems totally in character for how the system works. But whatever the reason, we can only 'guess'. We don’t really know 'why', and I wouldn't be surprised if no one is still around within the program who remembers the 'why'. It would make a terrific question for some politico to enquire about, especially if there was some dark secret behind the change as F-35 detractors seem to often insinuate.  

The Bottom Line, Again

For the F-35A model, the 8 second difference between new and old KPP appears to be trivial. The F-35B would probably have to unload a few seconds earlier or for a few seconds longer to meet the old KPP and the F-35C may have to unload a lot earlier and for a few more seconds to do the same.

But it is hard to say for certain, because the B and C early acceleration profiles may be just as good as pilots flying the F-35A assert about the CTOL version. The F-35C might have the toughest time making up the acceleration difference because it has a much larger non-lift contributor to wing wave drag to go with the larger lift contribution. But as it is also slightly longer overall and especially longer in the wing and tail surface areas, the F-35C shape in its entirety may (I don't think so but I can't rule it out) be lower drag than the others above Mach 1.1+. Or the F-35C may have other lower drag advantages due to something like its ‘cleaner’ wing attachment transition on the bottom surface. Who knows?

The newer 'changed' KPPs are as far as we know, still based upon modeled F-35 performance using “end-of-life, worst-case” scenario relative to the F135 engine’s power capacity” (Ref #7 Part 2) and “two per cent thrust” penalty (Ref #8 in Part 2). These ‘wedges’ against the F-35's performance could also be the difference between meeting the old KPP and needing the new KPP in the case of the F-35A, and part of the difference for the F-35B and C. 

The changes might also (almost certainly for the F-35C) have been due to encountering an ever-so-slightly higher than planned/predicted peak transonic drag coefficient, or some combination of the above. Contrary to what some might think, computational fluid dynamics and wind-tunnel testing do not prevent small surprises when the aircraft finally flies, they just lower the chances and severity. Sometimes those surprises go undiscovered for years (Bitburg Roll anyone?), and frankly I'm STILL surprised at how little difficulty the F-35 has had in some performance areas compared to legacy aircraft.  Beginning at about .8 Mach, even the tiniest drag [design] differences affect an aircraft’s [drag] performance out of proportion to the differences. The ability to cruise in military power at Mach 1.2 for some distance (Part 2, Ref#2) indicates that for the A and the B model at least, that ‘peak’ in the Drag Coefficient around Mach 1.1 is a fairly narrow one. 

The importance of the KPP change all comes back to what Tom Burbage was quoted as saying in Ref #4:

“...the biggest question is: are the acceleration characteristics of the airplane operationally suitable?”

The people buying and flying the airplane apparently say ‘yes’. And they've got the data and required knowledge and judgement to make the call. The voices outside the program do not.

Acceleration Sidebar: Is Acceleration More Important to Offensive or Defensive capabilities?

If I had to make a guess as to whether or not F-35 transonic acceleration was more critical in the A2A arena for closing on an enemy or escaping an enemy, I would say it is more important as an offensive attribute for closing on an enemy. Why? For two main reasons. First, I seriously doubt there is a fighter in existence or on the drawing board that can be expected to consistently attempt to overtake an F-35 without hesitation: or any aircraft that will competently shoot missiles over the shoulder at their pursuers. Second. The F-35 is being fielded as an optimal pack hunter: any aircraft pursuing one F-35 will always be a little more cautious if the pilot has reason to expect there to be another F-35 or two that he has no clue as to where it or they are.

Next Up: 

Stimulated by Commenter 'Tim A.' in Part 2, I'm going to do a quick parametric examination  of transonic acceleration differences between the 'ultimate' F-16 (Block 60) and the F-35A at A2G and A2A weights and loadouts. Nothing too extensive-- just something to ponder.