B-52 Engine Replacement Could Keep Bomber Flying Through Its 100th Birthday

It was 75 years ago this June that the U.S. Army Air Forces first awarded Boeing a modest $1.7 million contract to begin work on a new strategic bomber. Later this year, the 76 remaining B-52 Stratofortresses will start to get new engines that just might keep the venerable bomber flying through its 100th birthday.

The “biggest modernization program in its history” will replace the eight Pratt & Whitney TF33 engines that have powered each jet since the 1960s, said Air Force B-52 senior materiel leader Col. Louis Ruscetta. 

By the time the replacement is complete, the Stratofortress will have outlasted both of its current contemporaries, the B-1 Lancer conventional bomber and the B-2 stealth bomber. The new engines are intended to enable the B-52 to serve alongside the future B-21 Raider as the airborne leg of the nuclear triad into the 2050s.

“When we built the B-52, it was supposed to be a high-altitude nuclear bomber, right? Going to the adversary,” said Maj. Gen. Andrew Gebara, director of strategic plans, programs, and requirements at Air Force Global Strike Command. “Then it became a low-altitude nuclear bomber. And then it became a high-altitude carpet bomber in Vietnam. And then it became a standoff cruise missile shooter in Desert Storm. And then it became a precision strike close air support platform in Afghanistan and Iraq. 

“And now we're going to make it the first hypersonic shooter in the American inventory,” Gebara said, referring to the integration testing underway to fit the B-52 with the AGM-183A Air-launched Rapid Response Weapon.

“I don’t think the original plan was to go 75 years,” said Jennifer Wong, Boeing senior director for bomber programs. “But the way the aircraft was designed, it was designed with a lot of structural margin.” 

Wong and Gebara said the B-52’s designers erred on the side of caution in calculating the stresses the aircraft would face in its original high-altitude mission. That precaution has made it cheaper to hang new weapons on an old frame than to design a new aircraft, Gebara said. 

“Today, when we design something, it's computerized, and it's perfected for that one, you know, mission,” Gebara said. “Back in the day, when they had slide rules, they had to have a lot of margin, because they just weren't sure in their calculations. And it turned out that the B-52 was massively over-engineered.” 

The bomber has shown signs of structural strain and has been updated with modern parts over its years. Several changes were made after a B-52 carrying two hydrogen bombs broke apart over Goldsboro, N.C., in 1961. As the plane spun to the ground, one of the bombs activated — but did not detonate. After that incident, which killed three crew members, sections of the outer skin on the plane’s wings, spine, and tail were replaced with a tougher aluminum alloy. Some structural changes were made to the bomber’s internal frame. 

But “the bones of it are still a 60-year-old airplane,” Gebara said. Each of the remaining 76 bombers was built between 1961 and 1962. The engine overhaul won’t change that—the $11.1 billion CERP, or commercial engine replacement program, is expected to replace only about 10 percent of the bomber’s overall components, Air Force officials said.  

The older airframe’s analog technology and design also means that, unlike the military’s modern jets, maintenance crews cannot simply download a list of things that need attention after each mission. B-52 maintainers have to rely on post-flight debriefings from flight crews and their own familiarity to uncover problems. 

“You'll find various cracks in the fuselage, or in specific areas, when you're looking, where the metal actually cracks,” said Master Sgt. Matthew J. Tobey, a B-52 crew chief with the 2nd Maintenance Squadron at Barksdale Air Force Base.

“On a fifth-gen fighter aircraft, you plug up your computer, and it will say, ‘Hey, this part is broken, I've already ordered it,” Tobey said. 

“The B-52 is different. It's all manual, everything on this aircraft, you know, is done by people that are trained to do it,” Tobey said. “We've always got tech data that guides us on what we're supposed to be looking for, but it's all discovered by the individual. There's no computer that tells us what's broken on this aircraft.” 

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Boeing’s YB-52 prototype took its maiden flight in April 1952. Its future partner in the airborne leg of the nuclear triad, Northrop Grumman’s B-21, is expected to take flight next year. The Air Force anticipates buying at least 100 of the highly classified futuristic bombers, which will use  advanced radar-absorbent materials to help it fill the role of deep penetrator for contested environments after the B-2 is retired in the 2030s. The B-52 will continue to serve as the B-21’s complementary standoff weapon. 

“We will continue to have capability to do, you know, the kind of the traditional things that we've seen in Afghanistan and the like,” Gebara said. “But most of our focus is moving to that stand off capability. We think that's very relevant for the national defense strategy in the future, whoever that threat is, whether it's to the east or to the west.”

While the replacement engine hasn’t been selected or announced yet, Tobey said just the prospect of a new engine is encouraging. Work on the engines is often the most time-consuming aspect of maintenance.

In fiscal 2017, B-52s flew a peak of 2,591 sorties totalling 19,770 flight hours. Midway through fiscal 2021, the aircraft have flown 1,424 sorties and 8,597 hours. 

“Demand for bombers remains high worldwide,” the Air Force said in a statement, citing recent B-52 deployments to Europe, U.S. Africa Command, and U.S. Southern Command. 

The new engines won’t increase the bomber’s speed; even the existing engines could fly faster but don’t, to reduce stress on the airframe. Ruscetta expects that the new engines could increase the bomber’s fuel efficiency by as much as 30 percent, which could ease demand for the aerial refueling tanker fleet. 

Other modifications to the bomber that are already underway include replacing the B-52s original AN/APQ-166 radars with active electronically scanned array (AESA) radars, new nuclear command-and-control radios, and fitting the B-52 with new long-range stand-off weapons. 

Those swaps have the Air Force considering further reducing the size of the crew, Gebara said. 

“We think with the large number of upgrades we're doing on B-52, to the radar, and the mission we expect it to do, we're going to come off of five, down to four. We'd like to combine the navigator position and the electronic warfare officer position.” 

But the bomber can hold up to a crew of 10, which has had the Air Force thinking of other possibilities too, Gebara said. 

“Normally, in combat, you would only fly five. When we get to four, I can see a world in which we could, you know, if I fly three B-52s on a bomber task force mission. I could put six maintainers in every one of those extra seats, and we could self-deploy in some limited circumstances. So it’s exciting.” 

With all the changes, maintainers just might be rolling a computer up to the bomber in the future, Gebara said. 

“With those engines are going to come, you know, a re-do of the controls and displays and those modern techniques that are common in today's airframes,” Gebara said. “So it’s probably going to be a hybrid.”