While the U.S. Air Force is looking at boosting engine power on Boeing [BA] B-52H bombers for future missions, the service and Boeing also want to reduce the risk in the development program for the Commercial Engine Replacement Program (CERP) which is one of a number of modernization efforts to keep the Air Force fleet of 76 B-52Hs flying beyond 2040.
In the realm of increasing overall engine power of the aircraft, limiting CERP risk means not going through the process of developing new gear boxes or larger generators per engine, for example.
“We need to increase probably the power for future usage on the B-52, if we’re looking at another 30 years, but you’ve got to balance that with not driving a whole new development program that defeats the whole concept of as much off-the-shelf as possible for the engine solution,” Scot Oathout, Boeing’s director of bomber programs, said in a Sept. 8 telephone interview.
Boeing is the sole-source integrator for CERP and other B-52 initiatives, including internal weapons bay upgrades, communications network/electronics upgrades, and a new radar.
The existing TF33-PW-103 engine architecture for the eight engined B-52 includes four generators–one generator for every two engines. “Those generators each have a capacity of 125 kVa [kilovolt-amperes],” said Jim Kroening, the Boeing CERP program manager. “What we’re looking at on CERP is one generator per engine, but a lower overall power capacity generator relative to the 125, perhaps something in the 65 kVa range.”
Assuming 10 percent power loss and the outage of one generator, the CERP architecture would still allow nearly 410 kVa, versus about 338 kVa on the current B-52.
For the initial CERP award expected in the fourth quarter of next year, Pratt & Whitney is pitching its PW815 engine, which powers the Gulfstream [GD] G600 business jet; while Rolls-Royce is offering its F130 engine, based on the commercial BR725 carried on Gulfstream G650 business jets; and GE Aviation [GE] is offering two engines–the CF34-10, aboard Bombardier CRJ series airliners, and the Passport 20, carried on Bombardier’s Global 7500 business jet.
The Rolls-Royce F130 powers the Air Force’s Battlefield Airborne Communications Node (BACN)-enabled E-11A Bombardier jet, as well as the Gulfstream Aerojet C-37A VIP transport jet.
In May, the Air Force released its request for proposals for CERP to build 608 new commercial engines, plus provide additional spare engines and other support equipment and data over a 17-year performance period (Defense Daily, May 20). That includes one six-year basic period, one five-year option period and six one-year options, currently slated for fiscal year 2021 through FY 2035.
The winner will deliver 16-64 engines initially for integration onto at least two prototype aircraft.
The Air Force requested $299.4 million in research and development funds for CERP in fiscal year 2021 and nearly $1.3 billion for the program across the Future Years Defense Plan (FYDP). The Air Force has spent about $235 million over the past two fiscal years on the CERP, and expects to spend $7 billion to $8 billion over the program’s lifetime, officials have said.
The Air Force has said that despite being the oldest bomber, the B-52 has the most service life remaining among the B-1, B-2, and B-52. In addition, while the B-52’s mission capable rate was just 66 percent in fiscal 2019, that rate was higher than the B-2–60 percent–and the B-1–46 percent.
Congress has had some concerns on the Section 804 rapid prototyping strategy for CERP. The fiscal 2020 National Defense Authorization Act conference report required the Air Force to submit a report on the program, including its key performance parameters, and withheld 25 percent of the $175 million allocated that year for CERP until the report was submitted. The CERP RfP largely included the information requested by Congress, according to the Congressional Research Service.
Boeing’s CERP integration work includes designing new nacelles and engine pylons, accommodating the greater power capacity of the new engines, replacing the steam gauge engine instruments in the cockpit with LED displays, new sensors, a new air data system with a full authority digital engine control (FADEC) on each engine to tune engine performance, and a conversion of the mechanical positioning system for the pilot’s throttle to an electronic signal.
On Dec. 5 last year, Air Force acquisition chief Will Roper signed a CERP “Justification and Approval for Other than Full and Open Competition,” which acknowledged the “significant risk” in integrating commercial engine technologies on the B-52. The document said, however, that requirements on the CERP competitors to perform virtual prototyping and submit risk analyses on their proposed engines would mitigate that risk.