Forty years since the Air Force first started thinking about replacing the eight engines on the B-52, the job is finally underway. The re-engining is the centerpiece of an upgrade that will keep the Stratofortress operationally relevant for another 20 to 30 years.
The contract for the B-52 Commercial Engine Replacement Program (CERP) was awarded last fall and the program is moving forward quickly. Two new F130 engines have been built and if development and testing proceeds as planned, the first re-engined B-52s will be operational in about five years.
“All the things are in place that are really defining what the B-52 looks like … into the 2030s,” said Brig. Gen. John P. Newberry, program executive officer for Air Force bombers. He said upgrades include “new engines, a new radar, Advanced Extremely High Frequency and Very Low Frequency communications improvements, data link updates and cryptologic improvements, as well as several smaller efforts.”
All the things are in place that are really defining what the B-52 looks like … into the 2030s.Brig. Gen. John Newberry, PEO for Air Force bombers
The B-52 will also be the initial platform for the AGM-183 Air-launched Rapid Response Weapon, or ARRW, USAF’s first hypersonic missile, as well as the sole platform for the nuclear AGM-181 Long-Range Standoff
The F130 is a militarized version of Rolls-Royce’s commercial BR725, which the Air Force flies on its C-37 VIP transport and E-11 BACN (Battlefield Airborne Communications Node). After a three-year contest in which Rolls bested GE Aviation and Pratt & Whitney, the company won a $500.9 million initial contract in September 2021, to develop and test the F130 on the B-52. Once complete, Rolls will provide some 650 F130s to equip 76 B-52s. Each F130 engine will replace one Pratt & Whitney TF33. The overall program is valued at about $2.6 billion.
Rolls will provide the engines directly to the Air Force, and Boeing, the B-52s’ original builder, will integrate them on the bomber, ensuring that the new powerplants do not negatively affect the function of existing or new equipment. All the upgrades are expected to be installed concurrently during depot visits.
In January, Boeing trucked a retired B-52 carcass from Arizona’s Davis-Monthan Air Force Base “Boneyard” to the Oklahoma City Air Logistics Center, where it’s being set up in a new building built expressly to test the bomber’s new systems in a hands-on setting, validating the digital designs by upgrade suppliers.
The “high bay” at Oklahoma City Air Logistics Complex is “a Boeing facility that we built specifically for this program and the RMP,” or Radar Modernization Program, said Jennifer Wong, Boeing’s senior director for bombers. “The point is to have a full-scale replica—basically, a mock-up of the aircraft—that we can use for engineering” purposes.
That includes “form, fit function-type testing,” she said, as well as hands-on experience for engineers who have never “been able to touch” a B-52 or crawl around in it.
“Being exposed to the hardware is going to provide tremendous value,” she added.
The mockup will also be used for risk-reduction efforts, to “solve some of the … hydraulic component” challenges “that will be part of the CERP program,” Wong noted.
The F130 should deliver about 30 percent better fuel efficiency and far fewer maintenance hours, while eliminating the TF33’s “vanishing vendor” supply chain problems. That fuel efficiency will pay for the upgrades as much as a decade before the bombers retire circa 2050.
The engine upgrade will not impact the aircraft’s thrust or speed.
“One of the key things we’ve got to do on this program is stay on schedule,” Rolls-Royce B-52 Program Director Scott Ames said. The first major milestone, Preliminary Design Review, is expected this summer, and ground testing will proceed throughout the year.
Boeing will show how its part suppliers and initial design is “coming together in a virtual system prototype … a digital environment [in which] the engineers can make sure they’re making the right design choices.”
Boeing is designing a new engine nacelle to house the F130, and much of the testing in the next couple of years will ensure the engine upgrade has no unintended effects on B-52 performance, such as how the aircraft behaves in crosswind conditions, Ames said.
As is true today, the eight engines will fit in four nacelles. While USAF once considered four large-fan commercial engines instead, it stuck with eight to avoid substantial redesign of the wing, cockpit, and other components, and to minimize risk and delay.
Rolls-Royce is finishing a new $600 million production facility that will be dedicated to the B-52 work at its Indianapolis plant and has begun hiring people for the effort.
“It was a state-of-the-art modernization project and gave us the most competitive offer for the B-52,” according to Ames. “We’ve started the process of procuring all of the tooling and production fixtures we need to build this dedicated assembly line.”
The new plant has benefitted from “everything we’ve learned” producing the BR family of commercial engines, he said. “We’ve got a … dedicated test cell here … that was used during the proposal phase to demonstrate the F130, and it performed flawlessly.” Now, “we’ve got to do some more work to make it fit for a production-type operation, but that’s been launched, as well.”
The two test engines will be evaluated at NASA’s John C. Stennis Space Center in Mississippi, where Rolls-Royce has an outdoor jet engine test facility. “We’ll run the engines in a prototype nacelle configuration to test operability and crosswind effects,” according to Ames.
Ames said he expects the Critical Design Review, the next major milestone, in 2023. Between now and then, physical testing of F130s with and without Boeing’s nacelle will produce new performance data, updating predicted values from software models. That data will inform the control system to be jointly developed by Rolls and Boeing.
The nacelle is one of the crucial elements. The “twin-pod arrangement is fairly unique,” Ames said. Boeing and Rolls share a digital model of the B-52’s wing so that both are working from the same baseline.
The digital design and “constant integration meetings” ensure components do not interfere with each other and that the final configuration is easy to maintain. Ames said, “At Stennis, the two-engine pod and nacelle will be mounted on a test stand and run at various power settings, and under various weather conditions to gain “insight into how the engine is operating” and also provide feedback on the control systems.
Boeing is responsible for wiring and hydraulics that connect the cockpit and the engines.
Boeing will modify the first two B-52Hs with the F130 engines in 2024, doing the work at its San Antonio modification facility. The first eight planes will join a B-52 test force at Edwards Air Force Base, Calif.
In addition to new engine controls, the engine replacement work includes “physical wiring, hydraulic changes, power changes, [and] cooling changes”, Wong said.
The controls will be “what we’re calling a hybrid mechanical to digital throttle system. … When you’re in the cockpit, and you’re controlling the aircraft, there will be a mix between digital and wire.”
Two aircraft will be assigned to test the engine; two to test the new radar; and two each to test the new ARRW and LRSO missiles.
The flight-test effort is notionally to run from 2025-2026, Newberry said. “In very short order” after demonstrating safe flight, one aircraft will be modified with the new radar to begin collecting data on how the two function together.
The other upgrades will then be added one at a time, Newberry said. There are “many interdependencies.”
Newberry said the bomber directorate is working closely with the Air Force Sustainment Center to increase capacity at Tinker Air Force Base, Okla., where the installs will be done. “We have to be mindful of readiness and keeping a certain number of aircraft in the operational fleet, so we can’t take too long,” he said.
It’s still premature to gauge when the low-rate initial production and Milestone C, or full-rate production decisions will come, Newberry admitted. Those decisions will determine how fast the modifications take place. But at the rate of 10 to 11 a year, production will run to about 2035 to complete all 76 aircraft.
“We’re working with Global Strike Command on future roadmaps across all capabilities,” Newberry said. The time is now to begin “planning and preparing for what the B-52 of 2035 to 2040 looks like.”
Structurally, the B-52s are in great shape. While the bomber is 60 years old, “we have a great depot program and the iron is young,” Newberry stated. Years of sitting runway alert did not wear out the airframes.
Boeing is “very confident in the structure of the aircraft,” Wong said. The B-52 was designed “with a lot of structural margin.”
Newberry said the B-52 CERP was a pathfinder for accelerating an acquisition using an all-digital approach, but the program will be converted to a standard Engineering and Manufacturing Development (EMD) effort sometime this year. By using “other transactional authorities,” the Air Force saved a lot of red tape. It ended up as a “standard, best-value competition,” but the approach compressed the schedule, saving “years of schedule” by being able to “jump into actions with the contractor faster” and by accelerating the requirements process by skipping the Joint Capabilities Integration and Development System (JCIDS), Newberry said. In all, that saved “roughly three years over a traditional … approach.”
The CERP is now being regarded as “our flagship program” for doing a digital acquisition of an off-the-shelf product. While other programs, like the Ground-Based Strategic Deterrent and Next Generation Air Dominance are also using digital prototypes, creating a “digital twin” of the B-52 is not necessary, Newberry expressed. Digital twins are created for “the propulsions system … the wing … the electrical,” but not the full aircraft, the new systems won’t impact the bulk of the airframe.
The initial contract will carry the program through development and production of 24 engines: Four, for ground test and 20 for the test airplanes and spares, Ames said. It is not clear yet if the test engines will eventually join the pool used by the B-52 fleet. The first ones will be heavily instrumented, so it might not be cost-effective to remove that equipment for operational service.
A production contract would come right around the time EMD concludes, Ames said. But before that can happen, “there’s a big milestone hanging out there that could flow left or right a bit, called ‘production rate readiness.’” The PRR milestone certifies that all the suppliers and materials are ready to support production, and much of that is government-furnished equipment outside the scope of Rolls-Royce’s contract.
As for simulators and training devices for maintainers, “it’s early days for that,” Ames reported.
“We have demonstrated, through some of our augmented reality and virtual reality tools, some different training packages we can offer the Air Force,” he said.
Rolls-Royce can “leverage what we’ve done on other programs” and provide USAF with “a fantastic solution to maintenance, support, and training.” By 2026, “we’ll have a lot more clarity” on what the production and fielding element of the program will look like, he added.
It’s “premature” to assign the upgraded B-52H a new designation, although “B-52J” has been mentioned. That will be a “future conversation,” he said.
“The reason we do letter designations like that really has to do with operations and training,” he explained. If there’s a “significant difference” in how the aircraft is flown and employed, “the aircrew need to be fully aware” and nomenclature accomplishes that.
“This is the … largest modification to the B-52 in its history,” said Newberry, noting that April marks the 70th anniversary of the B-52 prototype’s first flight, “and we’re going to ask …the B-52 to continue to 2050.” Its long life is a testament, he acknowledged, to the bomber’s design and value.