The Shocking Resurrection of the F-15

Who says you can’t teach an old eagle new tricks?

As the Air Force likes to say, the two-crew F-15E Strike Eagle can fight its way into a target and fight its way out. It has to. A pre-stealth, fourth-generation multi-role fighter, the F-15 can’t hide from radar. Nor does it hide from the many photographers staking out the Machynlleth Loop, Wales, where U.S. 48th Fighter Wing jets based at Lakenheath, England scream by low. (Neil Bates)
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The future of fighter aircraft production is showcased in Building 27A at the sprawling Boeing manufacturing facility in St. Louis. Complex components that once were screwed and riveted together from five pieces of metal are now monolithic units machined out of single billets of titanium. Thousands of holes that previously had been drilled laboriously by union workers are now punched out with matchless precision by a robot. Even as a pair of massive wings takes shape, the building is eerily quiet. Thanks to automation, the wings are assembled by 20 laborers rather than the 80 required in the past.

But what’s really strange about the scene under way in this St. Louis factory is that these advanced manufacturing techniques are being applied to an airplane whose original design dates back to the Vietnam War. Stranger still, they will soon be used to build an upgraded version of this 48-year-old warhorse, which is about to become the newest fighter in the Air Force arsenal.

 F-15E Strike Eagles taxiing into formation
You want some of this? The Air Force wants more of it. F-15E Strike Eagles taxiing into formation last June at Mountain Home Air Force Base, Idaho, may soon be supplemented by eight advanced F-15EXs the service wants to order. (USAF / Staff Sgt Jeremy L. Mosier)

The Boeing F-15EX will be the latest and most capable variant of an airplane that has been in uninterrupted production since its first flight in 1972. It began life as an air-superiority fighter known as the McDonnell Douglas F-15 Eagle and later morphed into a two-seat, multi-role ground pounder dubbed the F-15E Strike Eagle. Long after the Air Force took delivery of its final F-15E in 2004, the St. Louis plant continued to build F-15s for sales to allies ranging from Israel to South Korea. Today, the wings being put together in Building 27A will be attached to an F-15QA destined for Qatar, while completed F-15SAs coming out of Building 67 are headed for Saudi Arabia. But the F-15EX will be smarter and more powerful than both.

“It’s a living, breathing, evolving platform,” says Boeing vice president for F-15 programs Prat Kumar. “The most recent avatar of F-15 is nothing like what was used 45 years ago. Frankly, it’s nothing like what the Air Force bought 15 or 20 years ago. F-15EX has a fly-by-wire flight-control system and one of the fastest, most capable mission computers in the world. It has an advanced, all-glass cockpit that can display synthesized data in a way that is useful for the warfighter. It has the most advanced radar on any fighter jet, and it carries more weapons than any other fighter.”

The Department of Defense 2020 budget request includes $1 billion to procure eight F-15EXs for the Air Force, with plans to acquire an additional 72 airplanes over the next four years to replace outdated and overworked F-15Cs and Ds that are ready to be retired. This would be a financial bonanza for Boeing, which has already landed a Navy contract for another so-called legacy aircraft, the F/A-18 Super Hornet.

But the Air Force decision to acquire the F-15EX has drawn a lot of flak—an especially appropriate metaphor considering the size and clarity of the fighter’s radar signature. Like the Super Hornet, the EX is a fourth-generation airplane, so designated because, though it incorporates a host of sophisticated avionics and digital flight-control systems, it lacks the signal attribute of fifth-generation fighters, such as Lockheed Martin’s F-22 and F-35: stealth technology. And critics say that investing in the F-15EX makes about as much sense as stocking up on slide rules.

“Over 80 percent of the Air Force inventory is non-stealth, legacy technology,” says Douglas A. Birkey, executive director of the Mitchell Institute for Aerospace Studies at the Air Force Association. “Types like the F-16, B-52, and F-15E will be in service for decades. We don’t need more of that sort of capability. We need to rebalance the force toward newer fifth-generation capabilities like the F-35, B-21 [a stealthy strategic bomber under development by B-2 builder Northrop Grumman], and the next-generation fighter, termed NGAD.” (NGAD stands for Next Generation Air Dominance.)

A similar recommendation was made in a report released last March by the Center for Strategic and Budgetary Assessments, a national-security policy think tank. “While F-15Xs are more capable ‘4th generation-plus’ aircraft, they would not be able to operate in future contested and highly contested environments,” the report states. “The Air Force should instead consider replacing some retiring F-15C/Ds with modified F-35As as a bridge to its future air superiority family of capabilities.”

During 2017 Red Flag exercises at Nellis Air Force Base, airmen with the 27th Aircraft Maintenance Unit check for structural damage on an F-22. Stealth specialists must repair any scuffs to ensure the aircraft maintains low observability. (USAF / Staff Sgt Natasha Stannard)
At Sheppard Air Force Base, Texas in May 2018, a Royal Saudi air force liaison officer (standing, second from left) observes Saudi airmen training alongside U.S. maintainers. (USAF / John Ingle)
Airman 1st Class Kyle Segura, 332nd Expeditionary Maintenance Squadron, inspects components on the underside of an F-15E fuselage. Inspections are conducted every several hundred flight hours on the jets, some of which have flown for more than 30 years. (USAF / Staff Sgt Joshua Kleinholz)
Boeing employees Darrien Moody (left) and Michael Reppert inspect an Advanced F-15 under construction for foreign object debris. (Courtesy Boeing)
The F-15 is assembled in St. Louis from parts sent in by 400 suppliers all over the world. (Courtesy Boeing)

However unpopular the Air Force decision may be, people on both sides of the debate agree that the current crisis—what defense strategists believe is an air-dominance fighter gap—was caused by the decision to cut production of the Lockheed Martin F-22 Raptor. Developed to replace the F-15C/D, the F-22 turned out to be so expensive—$350 million per airplane, by some estimates, if development costs are factored in—that beginning in the 1990s, successive presidential administrations hacked away at the number of fighters their budget offices would approve. In 2009, the Obama administration ended F-22 production at 187. When he canceled the program, then-Secretary of Defense Robert Gates explained that the Air Force would still have an adequate number of fifth-generation fighters because it had contracted to buy more than 1,000 of Lockheed’s newer F-35A. He predicted that by 2020, the Air Force would have 1,100 fifth-generation F-22s and F-35s.

But F-35 production has had its own problems, and by March 2017, early in the Trump administration, the Air Force had only 358 fifth-generation fighters. The fighter gap was becoming real, and the government-relations teams at both Lockheed and Boeing primed their PowerPoints. Lockheed began pushing for an increased rate of production for its entry—the most advanced fighter in the world—while Boeing argued that a bells-and-whistles update of the Advanced F-15 was the most affordable, most reliable way to fill the gap. The Office of the Secretary of Defense picked Boeing.

With an anticipated price tag of less than $80 million per unit, the F-15EX costs roughly as much as the F-35 does today (the F-35’s manufacturing costs have been steadily dropping), but proponents argue that the F-15 will be cheaper to maintain than a fighter with stealth coating that requires special treatment. The Air Force Association estimates the cost of flying an F-35A at $35,000 an hour; the F-15EX, at $27,000 an hour. Pilots and maintenance crews, says Boeing, would need less training on the legacy fighter, but there is nothing legacy about its new sensors, processing power, and data links. “All of that changes,” says Birkey, “and you have to send guys to school [to fly and maintain it].” Still, the F-15 is faster, can fly higher, and is able to haul a significantly heavier payload than any other fighter—up to 12 air-to-air missiles or 15 air-to-ground weapons, including the big bunker buster. So it would be a more useful weapon in lower-threat environments—everywhere other than a shooting war with China or Russia—that don’t require a next-generation, air-dominance whiz.

F-35A
The Air Force has taken delivery of 196 of the 1,763 F-35As it ordered. The most advanced fighter in the world has had a tough time living up to that handle; some teething problems (misaligned guns, for instance) persist. (USAF / Alex R. Lloyd)

Once upon a time, the F-15 was the next-generation, air-dominance whiz. A twin-engine, twin-tail, single-seat scimitar capable of exceeding Mach 2.5 and 60,000 feet, it was the brainchild of a cadre of Air Force visionaries who had seen the F-4 Phantom bested by MiG-21s in Vietnam War dogfights. With a thrust-to-weight ratio greater than 1:1, it could fly fully vertical immediately after takeoff.

“It’s got all the power and oomph of a 1970s muscle car, but it’s got the handling of a Ferrari,” says Boeing chief test pilot Dan “Dragon” Draeger, who flew F-15s in the Air Force and has since tested every variant other than a Japanese model built under license by Mitsubishi. “The air crews see it as a heavy hitter that can carry the throw weight and get it where it needs to go, but if they need to mix it up with somebody, it’s going to hold its own in the air-to-air arena. And because it’s a twin-engine airplane, there’s a lot of confidence that it can take some battle damage or some failures and still get back.”

Some of that confidence is inspired by the well-known good fortune of Israeli pilot Zivi Nedivi, who in 1983 miraculously landed an F-15 after losing a wing in a midair collision. Even more miraculously, the airplane was repaired and later helped shoot down a Syrian MiG-23.

Over the years, fighting in various forms for various countries, the F-15 has amassed an unblemished air-to-air combat record of 104 victories to zero losses. Yet despite this enviable history of air supremacy, members of the fighter mafia never warmed to the airplane. They wanted a pure fighter; during F-15 development, their mantra—largely ignored—was “not a pound for air to ground.” Disenchanted with the heft of the F-15, they began lobbying for a lighter, nimbler alternative, which eventually took form as the General Dynamics F-16.

Meanwhile, McDonnell Douglas doubled down on multi-role capabilities—especially air-to-ground missions—and teamed with Hughes to create the two-seat F-15E. The Strike Eagle entered the Air Force fleet in 1988. Since then, several slightly different models have been produced for foreign customers. (McDonnell Douglas and Boeing merged in 1997.) When fly-by-wire flight controls were added to the Saudi Arabian fighters in 2016, the Strike Eagle was renamed the Advanced F-15.

“The air-superiority mission, supported by 186 F-22s and 234 F-15C/Ds, demands a fourth-gen refresh to support needs past the mid-2020s,” says Air Force spokesman Captain Jacob N. Bailey. “The average F-15C/D is 35 years old and has over 8,400 hours. The payload capacity and range of F-15EX make it appropriate for missions where stealth isn’t the priority.” In other words, the F-15s operated by Air National Guard units to protect the United States against intruders don’t need a stealth capability that foils sophisticated air defense systems.

Retired Air Force General John Michael Loh, past commander of Air Combat Command, isn’t buying it. “The F-15 has been the mainstay of Air Force air superiority for 40 years, from the ’70s through the millennium,” he says. “I sent them into combat many times, and they performed with perfection—the most feared fighter in the world in its time. But missions, requirements, threats, concepts of operation, and technology all change. Nostalgia cannot replace innovation. If a fighter can’t penetrate defenses, engage and defeat the enemy, then survive under fire to fight another day, it has little value.”

broken formation of F-15Cs
In 2015, a four-ship of Mach 2.5, single-seat F-15Cs of the 493rd Fighter Squadron dramatically breaks formation during training operations at Royal Air Force Lakenheath in the United Kingdom. Once unbeatable, the 1970s-era fighters will soon exceed their service lives; many are operating today under speed and G-load restrictions. (USAF / Ioannis Lekkas)

Despite objections, production of the F-15EX has already begun in St. Louis. This is welcome news to the 1,000 or so Boeing employees assigned locally to the F-15 program. Not just for the obvious financial reason—that it will mean job security for workers who have been reduced to building one airplane a month to fulfill the Qatar contract. But also because the newest customer won’t be a country that most of them have never visited.

“This is a piece of freedom that we’re building here,” says Chris Harris, a lead assembly mechanic on the aft fuselage. “It helps our troops. It helps overseas. It helps us here. Now we’re going to sell it to our own people. That’s super exciting. And who else gets to brag that they build one of these? I could work on an assembly line building cars, but everybody’s got one of them. This thing is a beast.”

Kumar says he doesn’t foresee any problem building EX models alongside QAs. The airframes will be identical, but the Air Force version will be outfitted with proprietary (read: better) avionics, radar, and weapons systems. The biggest challenge, as always, will be getting all the components—400,000 individual parts sourced from 400 vendors spanning the globe—to fit together seamlessly. Two years ago, Boeing started to digitize components so they could be machined by computer-numeric-controlled mills. The accuracy of the parts coming out of CNC machines allowed the company to start using a process called full-size determinant assembly: digitally defined holes in the parts can be aligned perfectly without being mounted in a fixture and manipulated by hand.

“We assemble them in Lego-like fashion,” Kumar says. “This adds speed and agility to the process. It makes the airplane more affordable. It makes it more maintainable.”

Josh Scroggins was skeptical when he first heard the sales pitch. Although he’s now the senior manager for assembly of the F-15, the Missouri native started working at Boeing as an F-15 mechanic on the shop floor, performing many of the tasks that were being rendered superfluous. “One, I’m from the Show-Me State,” he says. “And two, when you tell me that all these holes are going to come together from different suppliers to within a thousandth of an inch, and this thing’s going to snap together, I’m like, ‘Yeah, right.’ But I had to eat a lot of words on that because it came out perfect.”

To date, the new production techniques have been limited primarily to the nose barrel and the wings. The rest of the airplane is put together in much the same fashion that McDonnell (later McDonnell Douglas) workers once cranked out two F-4 Phantoms a day in nearby Building 2, where production of the first F-15s began lo those many years ago. But today, the heart of the assembly line is Building 101, which was originally erected to supply the Mercury and Gemini space programs.

At 101,000 square feet, with a ceiling six stories high, Building 101 is a cavernous space where conversations echo and industrial-grade whistles mark the start and end of each of three shifts. About 75 percent of the work on the F-15 is done here, most of it devoted to the fuselage. Because production is so slow at the moment, the workforce is limited to 240 to 280 people. The vast majority are assigned to first shift, which, by tradition dating back to the F-4, runs from 6:18 a.m. to 2:23 p.m. (The idea was to limit rush-hour traffic around the plant.) Skins and bulkheads are delivered and built up in sections that are later spliced together.

As it wends from station to station, and subsystems are installed at various points along the line, the assembly begins to look like an airplane. Altogether, half-a-million holes are drilled—by hand. Even with power tools, cutting through titanium, which accounts for roughly one-third of the airplane, is nobody’s idea of fun. Yet in some cases, the tolerances have to be within one one-thousandth of an inch, which is half the width of a piece of notebook paper. Kumar and Scroggins are convinced that digital machining and determinant assembly will eventually do the job better than the men and women on the shop floor. But Lois Cuffie has her doubts.

Now 78, Cuffie started working at McDonnell Douglas in 1966, drilling air-duct skins for the F-4, and she later worked on the F-111, the F/A-18, the C-17, and the Harrier. “The F-15 is the hardest airplane I ever worked on because there’s nothing the same on it,” she says as she meticulously assembles a secondary heat exchanger. “I find no fault in robots, but machines have malfunctions, and robots go haywire sometimes. You still need a body with some skills to make sure that robot drills those holes in the correct place. A person has to know that product that he’s building.”

The production line in St. Louis introduces other factors that the Air Force may have weighed when it decided to buy new F-15s: maintaining a skilled labor force and a design capability among several manufacturers, for example. Writing for the Center for a New American Security, Air Force Colonel Brad Orgeron offered another perspective on the F-15EX. “This should not be a discussion specifically about whether the F-15EX or the F-35A is a better weapon system. Rather, discussion should focus on how to best meet airpower demands given finite resources and an F-15C fleet well past its service life…,” he wrote. Maybe the discussion should be even broader than that.

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