Fighters burn a lot of gas…a lot…and quickly.
No matter how much fuel we start with, we always burn it and always want more. In legacy fighters, using underwing weapons stations to hang fuel tanks takes up where bombs or missiles could be hung, slows us down and hampers our maneuverability. That’s where Conformal Fuel Tanks (CFTs) come in. Putting fuel tanks flush mounted along the fuselage, reduces the drag penalty from those external fuel tanks, and increases range and endurance…almost for free it would seem. Except there is no free lunch.
Super Hornet Block III promised CFTs and we have seen the promo photos with the fuel tanks bolted on to a new Super Hornet test airplane. But something happened (https://www.forbes.com/sites/davidaxe/2021/08/31/the-us-navy-tried-to-make-its-fighters-fly-farther-it-failed/amp/) and we have to wonder, how did Boeing screw this up? CFTs were to be a game changer, at least for a test pilot like me. All of a sudden, the Super Hornet would have the range capability closer to the F-35 and, for anyone in Canada and the US Navy, the reach of the Super Hornet would increase significantly. One could then argue that with CFTs and the promised improvements of avionics capabilities, certainly in the Canadian context, Super Hornet would be ‘Good Enough.’ CFTs would really help the fuel calculations to fly the distances needed from the Main Operating Bases (Cold Lake or Bagotville) to the Forward Operating Bases (Inuvik and Iqaluit), with extra fuel for a weather diversion if needed. Loading missiles on the weapons stations that were previously taken by external fuel tanks increases offensive capability that will matter in defense of the arctic and the potential of a Russian attack. Without CFTs, the Super Hornet is only marginally better than legacy CF-18 Hornets which never had enough fuel, ever.
So how did Boeing mess up this opportunity? Was there just not enough time to satisfy the US Navy’s requirements? The story of almost all problems discovered during flight testing has been fixes that took months or years and often $$$ millions to rectify. And time; except now, time matters. Super Hornet is on its last major upgrade and there won’t be another in its lifetime, save for periodic minor improvements. In the coming years, Super Hornet will have to fight for funding within the US Navy budget against the 5th Gen F-35C and rapidly coming 6th Gen Next Generation Air Dominance (NGAD). There just isn’t extra money to support large changes and improvements for the 4th Gen Super Hornet and so neat modifications like CFTs have run out of time.
How did CFTs fail? There is no doubt that the promise and relatively sexy addition of CFTs was going to be a visually significant step up for Super Hornet. In Naval aviation, catapult and arrestment capability is everything. Getting on and off the ‘Boat’ is a huge focus. The violence of this environment eclipses anything land-based flying will ever stress on a fighter. Having CFTs bolted on the fuselage is like carrying a heavy backpack all day, every day and the structural loads would be cumulative over time contributing to real fatigue problems. By all accounts, the stress of CFTs during catapult and arrestment testing opened engineering issues that could not be corrected in the small-time window for Super Hornet Block 3 flight testing.
There’s more to the story.
I first saw the CFT mods on Super Hornet at an airshow in Bangalore, India in 2009-time frame. We (the test pilots present at the airshow) all left at the same time each day after flying. We would all arrive back at the airshow the next morning for a repeat performance. Except one day at the end of the airshow, we arrived for our morning briefing to find one of the Super Hornets with Styrofoam shapes bolted on the fuselage. The Boeing workers had been busy overnight to make this new mod look very impressive and compelling. They had even painted over the blemishes on the airplane to make it look close to brand new.
On the Lockheed Martin side, we were there with F-16 E/F models which already had CFTs developed integral to this new variant. As I said in the opening, CFTs are intriguing because they solve fuel, performance and drag problems that all fighters face. During the many years of F-16 E/F testing, we reported often about the CFTs and what we had discovered in flight test and learned about them. Within the test pilot community at symposia like those held by the Society of Experimental Test Pilots, we talked about all the problems that we had encountered; logically the Boeing folks would have listened and learned. And surely, they would have taken our lessons learned home to St Louis to ensure that they did not repeat the mistakes that we made…apparently not.
CFTs create a bump on the top of the airplane which changes the way the airflow comes over the fuselage which, in turn, changes lift. Changing lift means that the jets will fly differently especially at slow speeds. The boundaries where the jet goes out of control would change, and how the jet would recover back flying may also change. That means that the CFT-equipped jet would have to undergo a whole series of testing in this regime. New flight control software logic, changes in the structural loads, changes in how fast the jet accelerates, maneuvers and even aerial refueling (F-16 E model used to snake during refueling behind an air force tanker) would need to be tested. Ultimately, bolting CFTs on the shoulders of a fighter means embarking on a full, expensive, time consuming flight test program. Did someone at Boeing really believe that this was going to be easy? The Hornet suffered significant fatigue issues to the fuselage over its lifetime and cost the users like the US Navy, US Marine Corps, Canada, Australia, Switzerland and Finland $$$ millions to manage, retrofit and maintain over the life of those legacy jets. Block 3 Super Hornet promised an even longer flying life than previous versions and the CFTs were guaranteed to be an issue to crush that promise. The fatigue life of a Super Hornet with CFTs bolted on would have to be ground tested to ensure that the newly promised increase in structural life had not been compromised. Those ground tests are painfully long but cannot be avoided in developing a significantly modified airplane.
Who’s going to pay for it now?
In the US Navy, increasing the reach for the Super Hornet closer to F-35C would have made executing strike packages more effective being able to send fighters even further from the aircraft carriers against enemy targets. Closer to home, CFTs helped neutralize the range advantages that F-35 would hold in operating distances in the Canadian arctic.
Loading up Super Hornets without CFTs to carry the fuel needed for arctic operations means not being able to carry the extra missiles needed to defend against an attack on North America. And if the US Navy is not going to pay for CFT integration to be fixed, who would? The testing would involve the complex work done at Naval Air Station Patuxent River, require a full time, dedicated test aircraft, control rooms for each flight full of many different engineering disciplines, chase airplanes and the ground tracking stations to monitor how the aircraft is behaving. All told, that means a test program which is enormously complicated to coordinate, takes years to execute and funding for the jets, people, facilities and support needed, which means lots of $$$…lots of $$$. Canada certainly is not going to dish out that money. The expectation as a customer is that this work has been done already and certainly not a cost to be added to the price of the jet. Paying for CFT development would be the ultimate sticker shock. Knowing this and based on the news releases from the US Navy, CFTs, for all intents and purposes, are dead in the water.
Why does it matter?
I want to ask my Boeing friends how they messed this up when so much was at stake. Not everyone has bought F-35, even though it has, thus far, won all competitions against 4th Gen fighters. Finland (64 jets), Canada (88 jets) and other nations still have competitions up in the air. Boeing needed to close the gap against F-35 and CFTs certainly helped. This was an elegant step to equalize the marketability between Super Hornet and 5th Gen, at least in one dimension. One would have thought that Business Development ‘Suits’ could have worked better with Engineering ‘Geeks’ at Boeing to get the CFTs through flight test and on to the fleet. But alas…something was missed.
And once again, we relearned that there is no free lunch.
Hey! Great article 🙂 Just a tiny correction, I think the title of one of the sections has a typo: “How’s going to pay for it now?”, shouldn’t it be “Who’s going to pay for it now?”
Perfect pick-up…thanks
Billie:
Your comments are very informative, but they concern technology. The Canadian uphill battle to procure the F-35 is not a technological competition, but purely a political one. It resides in the immature mind of Trudeau. He is on the record as stating that the “F-35 does not work”, and managed to out maneuver Laurie Hawn when Hawn inadvisedly tried to ram through the F-35 purchase. How can Trudeau now buy the F-35 and survive politically? This even with Boeing successfully killing Bombardier’s A220, and killing that company as a competitor. Trudeau has invited Boeing back into the competition for a reason.
This is what happens when a country elects as its leader a person who has never had a real job, disdains the military, and has the maturity of a 17 year old. I would suggest Lockheed raise the Boeing A220 issue again. Bombardier has great influence in Ottawa.
Marty. All true. Please go back and read my blog entitled “It’s the Economy, Stupid”. I have said for a long time that while I love talking technology, this decision will come down to jobs and cost. A couple of key things play into those issues. Switzerland uncovered the cost issue for everyone when they debriefed that it would cost the Swiss government 2 Billion Euros less to purchase and operate the 36 F-35As over a 30 year period versus Super Hornet or the other 4th Gen fighters in that competition. That’s an astonishing number and cannot be ignored. The sole source purchase of Boeing Super Hornets in the summer of 2016 did not crash because of the Boeing / Bombardier trade rift. Instead the amazing sticker shock of what Boeing and the US Government offered for the 18 Super Hornets. That is what killed the deal.
Jobs from Boeing will be linked to commercial work and will be easy for Boeing to jack up those numbers. However it is only 88 jets from a Boeing win versus 3000+ as an F-35 partner if Canada picks this jet. 3000 and building airplanes for 30+ is a lot of jobs for a lot of years. That becomes a really compelling tale of leading edge, high tech at a time when Canada needs to accelerate its investment in the future.
3000+ … Spot on Billie! No other fighter can offer long-term production opportunities like the F-35 can!
Frankly, I don’t care what Canaduh buys for its new tactical fighter. I do, but I don’t. However, Canaduh is one of the original JSF “partners,” and has reaped the economic benefits of F-35 work for many years. In my opinion, if Canaduh does not select the F-35, then all the F-35 work should be re-distributed to partner nations and FMS customers, in a manner similar to how all Turkey work has been re-distributed.
Has Trudeau factored this loss of economic benefit into his calculations? Has the Canaduhian press raised this point at any time?
(When Canaduh starts acting with some intelligence, then I pledge to start typing its national name correctly.)
My issue with the F-35 is the availability of spare parts which will result in jets sitting around not being able to be used because they are waiting on parts. The other issue is only one engine.
Interestingly enough, F-35 had a better availability rate than legacy fighters like the F-16 and F-15 last year. And sparing in F-35 is done completely differently than ever before. There is no hoarding of spare parts as we traditionally managed aircraft fleets.
Finally one engine is a topic that I have discussed in earlier blogs. Old adages and myths have long since been dispelled in fighter engine development and decades of single engine operation in the arctic by the US Air Force have taken away the arguments by some about single engine reliability. Please feel free to scroll back in the blog section to read that one.
Billie, those Arctic operating areas are unique. I was curious to take a look at locations of Inuvik and Iqaluit and some pictures.
I also remember having heard about the CFT’s that there are also fatigue challenges related to manoeuvring stress of structures connecting the tanks and fuselage, not only in carrier operations. On top of that there’s also the normal fatigue management. Certainly a single customer has no interest to carry the integration and development burden.
Ossi – You have correctly identified the fatigue issue that Finland or Canada would face with CFTs. There certainly would not be a 12,000 airframe life with the weight and structural fatigue imposed on the fuselage of the Super Hornet. Our air forces have spent millions managing fatigue from the legacy Hornets. We know better this time around about how vulnerable the Hornet fleet is to structural problems.
Why didn’t Boeing get around to designing CFTs for the Super Hornet?
You mentioned that Boeing was looking at this in about 2009. But in 2009, they also were in the thick of designing and testing the 787 Dreamliner. In December 2010, rival Airbus announced the A320neo, a re-engined, more efficient version of its A320. To compete in that space against Airbus, Boeing started thinking about modifying the 737. They conceptualized the 737 MAX. And they cut corners big time on the 737 MAX to accelerate time to market. That obviously didn’t work out well.
Many people think that the problems at Boeing began in the late 1990s with the Boeing / McDonnell Douglas merger:
What Boeing Has Taught Us About Not Neglecting Company Culture
https://www.forbes.com/sites/brettonputter/2019/12/18/what-boeing-has-taught-us-about-not-neglecting-company-culture-culturegene/?sh=5c2d1fc6496a
Given that Boeing had its hands full with the 787 and then the 737 MAX, and an increasing focus on profits, I’m not surprised that they didn’t get around to designing CFTs for the Super Hornet. Redesigning and requalifying the Super Hornet with CFTs might not have translated to significant sales. It was not worth it for Boeing, especially with everything else they’ve been dealing with in the last 10 years.
I still think the 787 is an amazing airplane and an engineering marvel. But its just not possible to be an all singing all dancing aircraft manufacture and, at the same time, meet the unrealistic expectations of the financial markets.
First issue is that CFTs would have cost millions to develop, test, manufacture and field. There certainly was not a launch customer back then but the foam shapes gave Boeing something to talk about. In that case potentially the Indian Air Force could have funded the test work had Boeing won that competition, which it didn’t. CFTs would / will take years to test and mature and will undoubtedly lead to some redesign and modification work during the flight testing period…which will cost even more.
Boeing Seattle was not the same company, culture or engineering expertise as existed with McDonnel Douglas in St Louis. The merger has everyone looking at defence company as though they were the slow lumbering commercial aircraft manufacturer.
The F-35 is the fighter to compete with the SUKHOI PAK. The world will not be destroyed by those who do evil, but by those who watch without doing anything (AE)
” The merger has everyone looking at defence company as though they were the slow lumbering commercial aircraft manufacturer.”
Boeing Seattle is also a defence company.
And McDonnell Douglas, St. Louis, was a commercial aircraft manufacturer. They built the DC-10.
https://www.upi.com/Archives/1982/09/14/Seventh-fatal-accident-involving-DC-10/5937400824000/
How This Plane Earned A Dangerous Reputation: The DC-10 Story
https://www.youtube.com/watch?v=l-085TjhUPo
Not quite. Boeing Seattle never built a fighter plane though they did provide the 757 test bed flown for F-22 support and built part of the fuselage plus did some avionics work. They never built a fighter plane….big airplane culture
McDonnell built F-4s and then F-15s and F/Z-18s. Douglas built the A-4 long ago but were known for MD-11 and C-17…..big airplane culture….not fighters…two very different worlds.
My original point in this thread was that Boeing has been busy with the 787 and 737 Max since 2009. As you point out, integrating conformal fuel tanks would have taken design, validation and testing to be accomplished. This would have been an expensive proposition with a questionably return on investment. The decision not to move forward CFTs probably was a corporate financial decision and not one made at any individual Boeing location.
CF-105: ah shit, here we go again.
Billie – I just found your blog thru F-16.net, great stuff!
Actually, Boeing has stated the CFTs will be available for SH export customers, so its unsuitability for the USN may be due to their harsh carrier operating environment.
https://www.flightglobal.com/defence/boeing-offers-update-on-super-hornet-cfts-t-
7a-wing-rock-fix/146025.article
Boeing (McAir) were early and leading exponents of CFTs, and have a very successful design on the F-15, not just for gas, but other functions.
Going further back, the original Boeing developed and tested conformal stores carriage on the phabulous F-4 Phantom, and the remarkable thing was, even with the bombs onboard, the F-4 performed nearly as well as a clean jet!
https://phantomphacts.blogspot.com/2017/11/conformal-weapons-carriage-and-f-4.html#comment-form
Interesting reference to F-4 days and conformal weapons. The F-15E example worked for so many years however their structural concerns were different than the Hornet where the fuselage ‘spine’ issues have haunted the fleet since it was first introduced more than 40 years ago. That problem didn’t go away with Super Hornet. The CFT problems for Super Hornet included requiring frequent access to maintenance panels underneath where the CFTs were installed which meant removing them more often than was planned. These are not take on, take off kits (based on my experience in F-16 E/F) which means a lot of work by crews to remove part of a CFT, conduct maintenance and then reinstall after the aircraft maintenance is complete. That task becomes incredibly hard when aboard a ship with so little room for maintenance personnel to work already and adding a CFT crane to remove and re-install becomes too much to manage.
Foreign customers can still order CFTs, except who is going to pay the $$$ millions for the flight testing that was not completed including full envelope expansion, out of control flight, flight control modifications, performance testing to gather data, and the list goes on. Perhaps Qatar has money to burn but perspective customers like Canada and Finland will never pay that. By all accounts from Boeing test pilots and engineers, CFTs are a dead issue.
The CFT issue w/ the Super Hornet further reinforces my belief that Boeing should be offering, and Canada should be considering, the new F15 EX and not the Block 3 SH. The new EX flies farther, faster & higher, can carry more weapons, has a bigger radar, the new EPAWSS EW system, a 20,000 hour service life and, importantly, a longer in-service life with the USAF. It wasn’t approved for purchase by the USAF at the time the Canadian competition started which probably explains Boeing’s offer of the SH, but a lot has changed and the SH is now on its way whereas the new EX is just now being inducted into service with the US. F35 proponents are aghast, but the USAF seems committed to operating the EX alongside the JSF. outand #s I get that you aren’t a fan of Boeing due to their tactics in sinking Bombardier’s CS220, but that aside the EX seems worthy of consideration – especially if paired withthe JSF which is why I’d love to see Canada acquire 48 of each type – which would allow the RCAF to operate three 16 plane squadrons of each type and mirror what the USAF is doing which would make cross training at red flag exercises seamless.
Buying some of both planes would also allow Canada to get some additional Boeing work and still remain part of the JSF consortium so as to be able to bid for JSF work. Curious as to your thoughts about the foregoing mixed fleet suggestion.
Note that I think the Gripen E also has some merit as part of a mixed fleet with the JSF, but the synergies of operating the same 2 planes as the USAF would seem to outweigh the seeming operational cost advantage of the Gripen.
Canada can barely afford a single fleet let alone think about two fleets, with infrastructure, sparing, training and CONOPS issues. Any 4th Gen asset will have the same limitations. Not being survivable in a future conflict without being VLO is just one of the major issues. Super Hornet means carrying all the extra weight an bulk in an airframe meant to operate from an aircraft carrier. F-15 EX might work well in the domestic role for the US but does not fit in the interoperability needed for Canada with Western nations. Gripen is a great small fighter but unable to conduct the role needed to cover the largest coastline and arctic ranges of Canada. I love that Gripen has become a fan favorite in Canada but could never meet the 5 Eyes integration required.
Interoperability?????
https://www.thedrive.com/the-war-zone/no-conformal-fuel-tanks-for-first-f-15ex-operational-units
CFT saga continued as summarized by Billie.
Cheers from Munich #teamsplitflap