As the U.S. Air Force embarks on a major re-engining of the Boeing B-52H, its leadership is under no illusions about the difficulty of the task at hand.
Delivered by Boeing in 1960 and ’61, the Stratofortress has been the service’s principal nuclear-armed strategic bomber for almost six decades. So when it comes time to crack open those old engine cowlings and run new wiring through the wings, artisans can expect to find plenty of surprises.
“Every time you renovate an old house, you didn’t realize there was going to be asbestos behind the walls,” says Lt. Gen. Jack Weinstein, the Air Force’s Deputy chief of staff for strategic deterrence and nuclear integration. “Am I going to stand here and say we’re not going to have problems with the re-engining? I’m not going to say that. But there has been an awful lot of work gone into evaluating how to re-engine it, and what’s the best way to do that.”
Over the past few years, the Air Force has engaged with engine manufacturers and potential prime contractors about the possibility of upgrading the B-52H’s eight Pratt & Whitney TF33-103s. In the past, the Air Force has considered a four-engine swap, but that approach isn’t practical.
Instead, the Air Force will replace eight TF-33s with eight modern, reliable and fuel-efficient business jet-class engines from the commercial sector. This plan has been deemed technically feasible and shouldn’t require a major recertification of the airframe and weapons.
This sounds enticing in theory, but re-engining an aircraft as old as the B-52 is easier said than done. The Air Force’s two largest re-engining efforts were the KC-135R Stratotanker (CFM International CFM-56) and Lockheed Martin C-5M Super Galaxy (General ElectricCF6). Boeing installed new engines on 415 Stratotankers, while Lockheed upgraded 52 Super Galaxys.
The B-52 will remain the backbone of the Air Force’s bomber force until large numbers of Northrop Grumman B-21 “Raider” stealth bombers are fielded in the 2020s and ’30s. The service estimates that this warrior of the Cold War will remain in active service at least through 2050.
GE Aviation has proposed replacing the TF33s with either its Passport or GF34 turbofan engine products. Rolls-Royce would offer an engine from its BR700 family, most likely the BR725 that powers Gulfstream’s G650 business jet.
Pratt & Whitney maintains that an overhaul of the TF33 sustainment process is required, along with a series of component upgrades to improve the engine’s efficiency, reliability and maintainability. The company disagrees with statements by service officials that the TF33 “is not sustainable past 2030.”
But since the Air Force has ruled out a life extension of the TF33, Pratt & Whitney could instead offer the newly certified PW815 that powers Gulfstream’s G600. General Atomics Aeronautical Systems has also selected the PW815 to power its tanking drone for the U.S. Navy’s MQ-25 Stingray competition, which could offer a pathway toward military certification.
“Why have we decided not to do a life extension? If you look at the civilian industry, overall, engines last forever now and are extremely reliable; hence why nobody in this room has a problem getting on a two-engine airplane and flying to the Pacific or Atlantic—because of the reliability of the engines,” Weinstein explained at a Mitchell Institute for Airpower Studies event in Washington on May 1.
“If you look at re-engining the B-52, it’s not something where we woke up one day and said, ‘We need to re-engine the B-52.’ A lot of work has gone into this.
“We’ve been talking about re-engining the B-52 for a long time. What gives me cautious optimism is that I’m proud of the people I work with who have been brought in to help us. The senior acquisition executive, Will Roper, is an extremely talented individual, and the people we’ve put in charge of these programs are really talented, too.”
The Air Force will likely work with Boeing or another prime contractor to install the engines. The service needs 650 engines, which includes 42 spares, to upgrade its remaining inventory of 76 B-52s. Twenty engines will be needed initially for the retrofit of two bombers for flight testing.
A notional schedule presented by the Air Force would upgrade 10 bombers by fiscal 2026, the same year the B-21 Raider comes online. The remaining 64 bombers would be upgraded from 2028-34.