Boeing F-15EX

F-15EX: Careful What You Don’t Ask For

April 2019

John A. Tirpak

While it was an open secret for months that the Air Force’s fiscal year 2020 budget request would include some brand-new F-15s, one of the surprise revelations at AFA’s 2019 Air Warfare Symposium was that those new Eagles weren’t the Air Force’s idea.

Air Force Secretary Heather Wilson, at a Feb. 28 press conference, admitted that while new “F-15EXs” are in the budget—later revealed to be eight airplanes for $1.1 billion, as a down payment on an eventual 144 aircraft—someone else at DOD inserted them in USAF’s budget to help the service address its inadequate fighter force structure.

“Our budget proposal that we initially submitted … did not include additional fourth-generation aircraft,” she acknowledged.

Washington wags initially suggested the F-15 was injected into the Air Force budget by Acting Defense Secretary Patrick Shanahan, who had a 30-year career with Boeing, maker of the F-15. Shanahan has recused himself from matters involving Boeing, however, and dismissed the idea that he is shilling for the company as “just noise.” Nevertheless, Boeing has received a disproportionate share of major defense contracts in the last six months, including the T-X trainer, UH-1N helicopter replacement program, and the MQ-25 Navy aerial tanker drone.

At the rollout of the 2020 defense budget request, however, Pentagon Comptroller Elaine A. McCusker revealed that it was former Defense Secretary Jim Mattis who ordered the Air Force to buy new Eagles.

Creating a “balance between the fourth and fifth-generation aircraft… [was] a decision that was made by Secretary Mattis before he left,” she said, noting that he had paid a lot of attention to “our cost calculus” in the field of tactical aviation.

Gen. Joseph F. Dunford Jr., Chairman of the Joint Chiefs of Staff, told members of the Senate Armed Services Committee a few days later the “framework” for the decision came from a study of the future needs of the military’s tactical aircraft fleet, which showed the Air Force has a shortage in its number of aircraft and the amount of ordnance those aircraft could carry.

When combined with the fact the F-15C will age out in the 2027-28 time frame, Dunford said “the best solution” was to go with the F-15EX to “backfill” the F-15 fleet.

The EX-variant initially would only be “slightly” cheaper to buy than a new F-35, but it will be more than 50 percent cheaper than the Joint Strike Fighter to operate over its life, Dunford said.

More of the calculus was explained by Maj. Gen. David A. Krumm, USAF’s Director of Strategic Plans and Requirements, who told Air Force Magazine the thinking behind the controversial add of Eagles. Essentially, he said, the National Defense Strategy demands more combat capacity immediately, or as soon as possible. And while buying more F-35s is the Air Force’s preferred solution, the F-15EX move could put more iron on the ramp more quickly; mostly because the transition time for individual units would take months rather than years.

“Cost of ownership,” is the key factor in the F-15EX’s favor, Krumm said.

“There’s 80-90 percent commonality” between the F-15C and the F-15EX, Krumm said, noting that the new aircraft can use all the aerospace ground equipment now used for the C-model of the Eagle.

“That’s all already in the inventory,” he said, but the similarity of aircraft also means “we’re looking at a transition time of months—less than six months”—to transition units now flying the C-model to the EX. “Typically, [with] an Active unit, that [process] takes 18 months; with the Guard, it takes three years.” He went on to say that “If you average that out, Active and Guard, each time we do that we save about two years of readiness,” meaning aircraft available for combat, “And that’s important for us.”

He insisted, though, that USAF is “committed to the F-35, and I think we’ve outlined that in the budget.”

Krumm, in a brief interview following a speech at AFA’s Mitchell Institute for Aerospace Studies, said the F-35 “is a game-changer” and “we won’t take one dime” out of 5th gen capability—nor will the F-15EX “take anything away from NGAD,” or Next-Generation Air Dominance, the future family of systems that will complement and/or replace the F-22 and F-35.

Brand-new F-15EXs will have strong bones and could last a long time—Krumm said 20,000 hours—meaning it could potentially serve well into the 2040s or 50s.

The Air Force has said the F-15 won’t be survivable against modern air defenses after 2028, so is it worth it to the service to spend the money to keep a non-stealthy, 1970s design into the 2040s?

“I think what we know is that we’re going to be fighting with 4th gen [aircraft] in 2028, and in 2035, we’re still going to have those,” he said.  “The way to use these things is to collaborate on a network, and it’s going to be, what can those things bring to the fight faster?”

For example, the new Eagle could be a launch platform for “standoff weapons, hypersonics. … They can go a long ways to assist the penetrating forces,” he said.

Air Force leaders have said they are seeking an early, interim hypersonics capability, and having F-15s that are not speed-limited due to their age (as current aircraft are) could be helpful in that pursuit. The F-15 design is technically capable of exceeding Mach 3, and so could accelerate a hypersonic missile close to its Mach 5-plus operating regime. That, in turn, would permit smaller booster rockets for weapons such as the Tactical Boost Glide hypersonic concept. The F-35, which was never designed to be USAF’s high-end dogfighter, has a top speed of Mach 1.6, and the first generation of hypersonic missiles is unlikely to fit inside its weapons bay.

“This is all about making the best use of the resources we’ve been given and building the best Air Force that we can,” Krumm said. The F-15EX is “what we came up with. … We will find a way to make this the best we can. We have to, anyway, and this is a capacity we think we need.”

F-15EX vs. F-35A

May 2019

John A. Tirpak

Two jets from different eras, with different missions, strengths, and weaknesses, face off in a battle for today’s funds.

The F-35 Lightning has been the Air Force’s sole new fighter program since 2009, when the F-22 Raptor program was prematurely terminated. While behind schedule, the program has been a top Air Force priority for more than a decade and until recently, was expected to remain USAF’s  only fighter program until a future capability, still undefined, comes online.

Now the F-35 faces a new challenge from an old jet design, a variant of the F-15 Strike Eagle; an airplane from an earlier era, built for a different mission. Though the Air Force denies it, the two jets are competing for inevitably limited dollars within the service’s fighter portfolio.

The Air Force’s fiscal 2020 budget request includes $1.1 billion to buy the first eight of a planned 144 F-15EX aircraft. The new airplanes are very similar to the export versions now being built for Qatar. The F-15EX is a two-seat fighter that can be flown by one or two aviators and is meant to replace F-15Cs and Ds that are reaching the end of their service lives.

Under the plan, the Air Force would receive two F-15EX airplanes in 2022, six more in 2023, and a total of 80 airplanes in the next five years. Separately, the 2020 budget request also includes $949 million to upgrade existing F-15s.

Adding new F-15s was not an Air Force idea, but instead came out of the Pentagon’s Cost and Program Evaluation office, or CAPE, and was endorsed by former Defense Secretary James Mattis. While the Air Force’s long-held position has been to invest only in fifth generation fighter technology, it has defended the plan to buy new F-15s as a way to maintain fighter capacity, given the aging of the F-15C fleet and the slow pace of F-35 acquisitions.

While the Air Force is adamant that buying F-15EXs will not reduce the requirement to build 1,763 F-35s, history and the Air Force’s own budget request suggests otherwise. The 2020 budget submission shows the Air Force buying 24 fewer F-35s over the next five years compared to last year’s plan.

The opening for the F-15EX results from the age and condition of today’s F-15Cs. Designed as air superiority fighters and first fielded in the 1970s, the F-15Cs were planned to have retired by now. But the premature termination of the F-22 after acquiring 186 aircraft—less than half the planned production—compelled the Air Force to extend their service. Now, key structural components are reaching the end of their engineered service life—so much so that many F-15Cs must operate today under significant speed and G-loading restrictions.

The Air Force’s arguments for the F-15EX turn on preserving capacity. The F-15Cs will age out of the inventory faster than new F-35s can come on line, reducing the available fighter fleet at a time when the Air Force argues it’s already seven squadrons short of the 62 officials say they need to meet the National Defense Strategy.

The F-15EX, USAF argues, is essentially an in-production aircraft. It has upward of 70 percent parts commonality with the F-15C and E already in USAF service and can use almost all the same ground equipment, hangars, simulators and other support gear as the Eagles now in service. At a unit price roughly comparable to that of the F-35, F-15 squadrons could transition to the F-15EX in a matter of weeks, whereas converting pilots, maintainers, facilities and equipment to the F-35 takes many months, the Air Force says.

The F-15EX, though, is a fourth generation aircraft which lacks the stealth characteristics and sensor fusion of the F-35 and F-22 and therefore won’t be able to survive against modern air defenses for very much longer. USAF has said that 2028 is probably the latest the jet could conceivably operate close to contested enemy airspace. However, CAPE and Air Force officials see viable continuing missions for the F-15EX in homeland and airbase defense, in maintaining no-fly zones where air defenses are limited or nonexistent, and in delivering standoff munitions.

While the Air Force has maintained since 2001 that it will not buy any “new old” fighters, and that it needs to transition as quickly as possible to an all-5th-gen force, proponents argue that buying F-15s and F-35s concurrently would fill gaps in the fighter fleet more rapidly. Moreover, USAF leaders, defending the new F-15 buy, have said that the F-35 still hasn’t proven it can be maintained at the advertised cost (comparable to the F-16, at about $20,000 per hour) and the service prefers to wait to make large bulk buys of the airplane after the Block 4 version starts rolling off the assembly line in the mid-2020s. This approach, they say, will also avoid spending large amounts of money to update earlier versions of the F-35 to the Block 4 configuration.

An F-35 performs a weapons bay door pass during Demonstration Team training over Luke AFB, Ariz.  Photo: SrA. Alexander Cook

This isn’t the first time the Air Force has considered buying new F-15s, but the F-15EX isn’t the same as upgraded models previously offered by the jets’ maker, Boeing. The most recent offerings would have required extensive development work. In 2009, Boeing proposed the F-15 “Silent Eagle,” which would have added stealth characteristics. That jet would have carried weapons internally in conformal stations and featured canted vertical fins and surface treatments to reduce its radar signature. Boeing offered another concept, the “Advanced” F-15, or F-15 2040C, last year. That jet would have had a substantially increased payload and advanced avionics.

Instead, the F-15EX requires almost no new development, would be able to execute a test program very quickly, and requires minimal additional development.     

Air Force officials say one potential mission for the F-15EX would be carrying “outsize” munitions, such as hypersonic missiles, and as a possible standoff weapons magazine working in conjunction with the F-22.

The F-35 and F-15EX were designed in different eras for different missions.

The F-15C was designed for air superiority in the pre-stealth era; the F-35 to be the battlefield “quarterback,” gathering vast amounts of information from behind enemy lines while executing stealthy strikes and picking off enemy fighters. Yet, as Congress decides how to invest in future aircraft, comparisons are necessary as the two planes compete for resources.

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