The F-15EX, as shown here in this illustration, can carry two more air-to-air weapons than the F-15E. Boeing
Photo Caption & Credits

Joining Up on the F-15EX

Nov. 1, 2020

The Air Force prepares to welcome the first new F-15s since 2004.

Early next year, two Boeing F-15EXs will arrive at Eglin Air Force Base, Fla., for testing. The most tricked-out, advanced Eagles ever built, and the first factory-fresh F-15s acquired by the Air Force since 2004, they’re the lead aircraft in a planned fleet of up to 200 F-15EX fighters to be added over the next 15 years. 

The F-15EX comes with nearly all the bells and whistles Eagle drivers have ever wished for: fly-by-wire flight controls, two new weapon stations, a new electronic warfare suite, advanced radar, a hyper-fast computer, conformal fuel tanks, and a strengthened structure. 

But it’s still a fourth-generation fighter, no stealthier than the F-15A that rolled out in 1974. Low observability is considered crucial for operating near modern adversary air defenses, so this new fighter will have to remain, for the most part, outside enemy airspace until those defenses can be beaten down.

The F-15EX was added to the Air Force’s budget in 2018 when then-Defense Secretary James Mattis, acting on the advice of Pentagon analysts, decided that a modernized fourth-generation Eagle could provide a needed capacity boost and give the Pentagon competitive leverage with Lockheed Martin, maker of the F-35A, USAF’s preferred, fifth-generation fighter.

 The F-15EX is “designed to evolve from Day One.”

Will Roper, USAF acquisition chief

Heather Wilson, then-Secretary of the Air Force, would later admit USAF hadn’t sought the F-15EX. It had been USAF policy since 2004 not to buy any “new-old” airplanes, and concentrate on fifth-generation machines. 

Now that it’s in the budget, though, the Air Force is embracing the F-15EX as a means to shore up its fighter force, facing the hard reality that it just doesn’t have enough iron to go around. USAF never got the 381 F-22s it planned for to replace its F-15C/Ds and carry the air superiority mission through 2040, receiving only 186 Raptors. To meet global force requirements, it had to retain more than 200 of the youngest or lowest-time F-15Cs well beyond their planned service lives. 

Eleven years later, those F-15C/Ds are so worn down that Air Force officials say it’s no longer cost-effective to fix them. To remain safe, they require constant and costly inspections to ensure fatigued structural elements are still viable. 

The first F-15EX taking shape at Boeing’s St. Louis sfinal assembly facility. Boeing invested its own money to get USAF the first two jets ahead of schedule, and testing will begin in early 2021. The first contract was awarded in July. Eric Shindelbower/Boeing

The cost of sustaining the Eagle fleet and other old platforms is “eating me alive,” said Lt. Gen. David S. Nahom, deputy chief of staff for plans and programs., 

Older aircraft are handicapping the Air Force in multiple ways, Nahom said in an interview. “Not only are they costing us too much money, but they’re offering us too much risk,” due to obsolete gear and age-related flight restrictions. He said the Air Force must move out swiftly to bring on the F-15EX “as quickly as we can to recapitalize” F-15C/D units. 

Boeing quotes a flyaway cost for the F-15EX of $80 million a copy—about the same as the F-35A. But operating costs are a differentiator. Recently retired Chief of Staff Gen. David L. Goldfein said USAF has been leery of the F-35’s cost per flight hour, still about $35,000, which is well above the F-15’s $27,000 per hour. The Air Force also wants its fleet to be mostly of the Block 4 version of the F-35, which is not yet in production. That jet will have more advanced sensors and can carry a greater variety of weapons. By waiting, USAF can get a greater number of jets in the more advanced configuration and spend less on retrofitting earlier ones.

To Chief of Staff Gen. Charles Q. Brown Jr., it’s not a matter of one or the other. “It’s capability and capacity,” he said during a Defense One online event in October. While Brown insisted, “We still value the F-35,” he called the F-15EX an “opportunity.” Because foreign customers have invested heavily to modernize the F-15, the Air Force can leverage those investments and acquire an airplane that’s as good as a fourth-generation airplane can be, without laying out big dollars for development or tooling, Brown asserted. 

Saudi Arabia and Qatar have collectively spent about $5 billion developing their own versions of the F-15, said Boeing Vice President Prat Kumar, who heads its F-15 program, in an October interview. The Air Force can reap the benefit of that investment.  

The F-15EX will be almost identical to the F-15QA being built for Qatar. Now in testing, that aircraft builds on the F-15SA developed for Saudi Arabia, the first to trade the old hydraulic actuators and cables for a digital, fly-by-wire system. 

Boeing test pilots have reported that the F-15QA flies very much like the F-15C/D and E models, but reaches the edge of the performance envelope faster. Transitioning from USAF’s old Eagles to the new should be easy, they say, requiring only that pilots adapt to the EX’s new “glass cockpit” displays, which replace the 1980s-era steam gauges in the C/D and E models.  

Gen. James M. Holmes, who retired as head of Air Combat Command in August, said he supported the EX purchase because, with congressional funding adds, it’s affordable and the first one will be “ready to fight as soon as it comes off the line.” Even though it will be limited in how close it can get to enemy air defenses—owing to its large radar cross section—the EX will be effective for homeland defense and in areas where the adversary threat is less severe, he said.

Service officials say they are still figuring out how to “shape” the future force, and for the moment, the F-15EX will simply fall in on the mission of the F-15C/D. In the future, however, one senior official said the EX could shift to more of the E model’s ground-attack mission, in the 2030s, as that airplane comes to the end of its service life. The EX will have two cockpit positions, but USAF has officially said it intends to fly the aircraft with a single pilot.

new F-15s
Graphic: Dash Parham and Mike Tsukamoto/staff

“The EX can carry every weapon that a Strike Eagle can carry, plus a few,” a Boeing official said. “I think there’s probably going to be a robust conversation … about what the EX can and cannot do … and what is value-added versus not, from a mission standpoint.”  

Boeing received the first payment of $1.2 billion for the F-15EX on July 13. The cost-plus-fixed-fee, cost-plus incentive contract set a ceiling of $22.89 billion for up to 200 aircraft, although USAF has only spoken of buying 144. Separately, the Air Force awarded GE Aviation a $101.4 million contract for the first 19 GE-F110-129 engines to power the EX test fleet—the same engines that power the F-15SA and the QA. They will be provided as government-furnished equipment. The Air Force will allow Raytheon Technologies’ Pratt & Whitney unit to offer a competitive power plant for the production program, though, as long as Pratt certifies its engine on the F-15EX, at its own expense.

The Air Force’s Future Years’ Defense Plan calls for 76 F-15EXs, but Congress will not approve more until USAF submits an acquisition strategy for the fighter. 

Because of commonality, an F-15C/D squadron will be able to change over to the F-15EXs within about three months of getting them, Goldfein said, using a lot of the existing ground support gear and requiring little new military construction. By contrast, transitioning a unit from the F-15C/D to the F-35 might take several years, given the unique gear, training and milcon required. This speed of fielding is cited by USAF leaders as the most attractive part of the EX program. 

Except for some bridge support by contractor personnel for the test aircraft, the plan is for the EX to be maintained by USAF’s organic capability.

The Air Force plans to put the first operational F-15EXs at Kingsley Field, Ore., where it conducts F-15 training.

In addition to state-of-the art missions systems, the F-15EX is being built with modern technologies and with the idea that it will frequently be upgraded, Kumar said.

“We have improved the wing so that it eliminates base-[level] … and programmed depot maintenance,” Kumar said. The digitally re-engineered wings are being built at Boeing’s St. Louis plant by a team of a dozen technicians and robots, versus the 86 people needed with the earlier design. The digital construction method minimizes mistakes and rework.

The jet will also have “open mission systems and open architecture,” he said, and is a “pathfinder” for the Air Force’s agile software development approach. Known as DevSecOps, it accelerates software development and releases by breaking down barriers between developers, security practitioners, and operators.

Will Roper, USAF acquisition chief, said the F-15EX is “designed to evolve from Day One,” and will be able to keep up with rapidly changing communications and data-sharing systems the service is creating. 

The operating system “can containerize third-party applications” and run new software “without having to go through very extensive flight testing [and] regression testing,” Kumar asserted. 

Squadrons will be able to switch from F-15C/D Eagles to F-15EX aircraft within about three months of getting them since the jets are so similar. Here, Eagles conduct aerial operations in support of Bomber Task Force Europe 20-2 over the North Sea March 16.
Master Sgt. Matthew Plew

The F-15EX can “incorporate future technologies rapidly,” enabling it to become “a testbed for technologies more broadly for the Air Force,” Kumar said. These will include not just what might go into future versions of the EX but other technologies, given that it has the fastest processor flying, as well as a fiber- optic network and physical room inside. 

The F-15EX will be protected by the Eagle Passive Active Warning Survivability System, or EPAWSS, a new electronic warfare suite. While EPAWSS functions remain classified, officials say it will be able to detect, locate, identify, and electronically engage a variety of threat systems. The first two test EX aircraft that reach Eglin will have EPAWSS installed, and Boeing officials said the eight test EXs will give the Air Force more EPAWSS testing capacity. The EPAWSS will also equip the F-15E.

EPAWSS is “included in the price” of the F-15EX, Kumar said, as is the Raytheon APG-82(V) 1 radar, which the Air Force has already installed on many of its C/D and E model Eagles. 

Also included in the $80 million flyaway price will be the Suite 9 common operational flight program, and MIDS/JTRS (Multifunctional Information Distribution System/Joint Tactical Radio System) software-programmable radio. Capability for the Joint Helmet-Mounted Cueing System capability will be built in, but the helmets will be government-furnished equipment.

Not included, however, will be any additional sensors, such as Sniper or Litening pods, or Legion Infrared Search-and-Track (IRST) pods, a Boeing official said. 

“Everybody wanted it to be crystal clear on what they’re getting for what price,” the official said. “The Air Force gave us a list of what … the F-15EX configuration should be, and it had to do with two things: One, the capability they wanted, but the other was commonality with what they were already doing.” The Air Force didn’t want sensor pods in the package “because [they] said, ‘Hey, look, we’ve already got Sniper pods. We’ve got IRST pods.’” While the EX doesn’t come with the IRST, it can use it. 

Boeing says the F-15EX has a 28 percent larger payload than the F-15E, with two more weapons stations. The extra stations add loadout flexibility, company officials said.

The F-15EX’s central pylon can carry a notional 22-foot, 7,000 pound weapon. This artist’s concept shows an F-15EX after firing a hypersonic missile from that station.
Sherif Wagih/Boeing

Some theater air commanders wanted “different loadouts that might be more applicable” to their regions. “An airplane that can carry seven 2,000-pounders, which an EX can, makes a big difference. In other places they have lots of targets … so carrying 28 (Small Diameter Bombs) in that theater” makes  more sense. The EX “can now carry four air-to-air missiles while it’s doing all that other … air-to-ground” work. 

The Air Force initially expects to use the EX as an air-to-air platform, directly substituting for the F-15C. In that role it can carry 12 air-to-air missiles, and on the new stations, either the AIM-120 or AIM-9 can be carried.

At the Air Force Association’s virtual Air, Space & Cyber Conference in September, Boeing’s virtual exhibit included an image of an F-15EX launching a hypersonic weapon. Asked about it, Kumar said only that the aircraft’s central pylon “can carry a 22-foot, 7,000-pound weapon.” Another Boeing official said there have been “fit checks” with an unspecified missile. “We’ve done … work in the simulator on this,” the official said. 

The first jets will reach Eglin nine months ahead of contract schedule. Boeing has fronted some of its own money to build them, to show the Air Force it can deliver swiftly.

“We’re excited to deliver these two airplanes just … a few months after contract award, and let the Air Force start flying them,” Kumar said. “They’re going to get … almost two years of flying on the first two airplanes before the rest of Lot 1 delivers, and [of] the next six, … four of those will also be test-wired for data collection.” The last four will probably be a “top off” to testing, as most developmental tests will be completed by the time they arrive. 

The Saudi government paid the U.S. Air Force to flight-test the F-15SA, which was the first to use the fly-by-wire system. That program—for which testers received an award by their peers—“tested every flight-test point the F-15 had ever flown,” a Boeing official reported. “And, the thought now is that we simply don’t have to go back and do a lot of that because it was great data.” The Qatari jets aren’t that different from the Saudi aircraft; it has “a smaller test program” focusing on the radar, displays, and computer, “so a lot of that obviously doesn’t have to be redone.”

Moreover, the F-15 test force at Eglin is already shaking out the EPAWSS, MDS/JTRS and Suite 9, so the addition of eight F-15EX jets with all those features will add capacity and speed to the test force, he said. “There’s a ton of synergy,” he added. Developmental test pilots are already checked out in the QA aircraft, “so they’ve got a leg up, already. … The airplane is already very known to the test community.” 

What will be new on the EX will be the Suite 9 operational flight program and a new armament control suite, which will require shooting some missiles. 

A new simulator is being put together, but the changes needed to convert an F-15C/D or E sim to an EX are minimal, a Boeing official said, and won’t require new buildings or other large investment. Likewise, there shouldn’t be a problem integrating the F-15EX into Defense Department wargaming simulations, because the adjustments will be small.  

Because the F-15EX didn’t go through the typical process of the Air Force setting a requirement and following a development process, it won’t conform to typical programmatic milestones, Kumar said.

“This is different. … We’ll go through the Milestone C decisions” by combining them with a benchmark called Integrated Design Review, rather than Critical Design Review.

“These are really production-ready jets,” he said, “so it should be fairly straightforward to get into production right after” Integrated Operational Test and Evaluation.

Boeing is planning to build about four F-15EXs per month, including foreign jets. Can the F-15C/D fleet last long enough for the F-15EX to get onboard? 

“The Air Force is looking at that by tail number, and with a lot of attention,” a Boeing official said. “They’re doing inspections … and [looking] at the data, and … looking at what the implications are on the fleet.” He said he thinks the Air Force is “cautiously optimistic … but we’re certainly supporting them in every way we can think of.” 

Kumar said the Air Force’s adoption of the F-15EX will potentially expand the number of countries that might buy the jet, including current users Israel, Japan, Qatar, South Korea, and Saudi Arabia.

“The world watches what the U.S. Air Force buys,” Kumar said. “So clearly there’s interest in our existing customer base across the world.” Israel is “taking a look” at the new F-15, he said, while Japan is planning to incorporate many of the EX features except the fly-by-wire system.