US Airforce Boeing B-52H Stratofortress Engine Replacement Update

The US Air Force (USAF) has provided an update on its Commercial Engine Replacement Program (CERP) – which seeks to replace the powerplant of its venerable Boeing B-52H Stratofortress fleet.

The update comes via the Director Operational Test and Evaluation (DOT&E) FY2019 Annual Report, which explains that CERP is a government-led engine source selection campaign that will provide new engines for the USAF’s B-52H strategic heavy bomber fleet, replacing its legacy TF33 turbofans. The report states that the programme is “built around a five-phase integrated test strategy designed to maximise operational test data collection during the prototyping phase” and “includes a limited operational demonstration using prototype aircraft followed by a comprehensive [Initial Operational Test & Evaluation (IOT&E)] using Low-Rate Initial Production (LRIP) aircraft prior to a Full-Rate Production decision.”

B-52H Stratofortress of USAF
Boeing B-52H Stratofortress - registration 61-0006 (c/n 464433) - of the 96th Bomb Squadron 'Red Devils' departs RAF Fairford, Gloucestershire, to train with Norwegian counterparts during Bomber Task Force Europe 20-1 in October 2019. USAF/SA Stuart Bright

Three primary engine contractors are vying for the contract, comprising General Electric (GE) Aviation, Pratt & Whitney and Rolls-Royce. The companies are expected to deliver their initial aerodynamic models early this year – ahead of the air arm’s final selection, which is due to take place in January next year. The USAF aims to procure roughly 650 engines to modify and support its 76-strong fleet of B-52H Stratofortress aircraft. 

The programme began in February 2018 and it has since been designated as a middle tier of acquisition (MTA) rapid prototyping development effort. The air arm is following a “rapid prototyping strategy” starting with the development of “a Virtual Power Pod Prototype (vPPP) digital model for each candidate engine to assess two-engine, side-by-side pod design options”. The results collated from the vPPP will support the development of a Virtual System Prototype (vSP), which is a full aircraft design digital model of the selected engine “to support a preliminary system design assessment”, which will then be followed by the “physical modification of two B-52H prototype aircraft to support initial aircraft performance, flying quality and structural test activities”.

B-52H Stratofortress B-52H - registration 61-0006 (c/n 464433)
B-52H - registration 61-0006 (c/n 464433) - of the 96th Bomb Squadron 'Red Devils' undergoes maintenance from the 96th Aircraft Maintenance Unit, 2nd Maintenance Squadron, at RAF Fairford, Gloucestershire, during a deployment in October 2019. USAF/SSgt Philip Bryant

Of the 76 B-52s, 11 will receive new engines under LRIP as part of the final phase of system development testing/IOT&E and the remaining 65 will go through the process in six full-rate production lots.

Rolls-Royce is offering a version of the BR700 turbofan engine – designated F130 by the USAF – in its campaign to supply the B-52H’s engine replacement. The BR700 is a proven platform, boasting more than 25 million flight hours powering business jets. It has also racked up approximately 200,000 combat flight hours with the USAF, with which it is employed by the C-37 and the E-11 Battlefield Airborne Communications Node (BACN). The company states that when “installed in the B-52, this engine will provide vastly greater fuel efficiency while increasing range and reducing tanker requirements”. It adds that “the F130 offers outstanding reliability with high mission readiness and low maintenance demands” and it “can stay on wing for the planned B-52 lifetime”. 

Rolls-Royce F130 Engine
A cut out of the F130 engine. Rolls-Royce (via Twitter)

Pratt & Whitney – the manufacturer of the bomber’s current TF33 – is planning to offer its PW815 turbofan, which is currently employed by the Gulfstream G600 business jet. As an alternative, the company is also offering to provide a life extension of its TF33 engines – a route the USAF may be unlikely to take, given that the service wants to replace these engines to improve maintenance costs and to make the aircraft 20% more fuel efficient.

PW815 Turbofan Engine
The PW815 turbofan. Pratt & Whitney

GE Aviation is offering two engines: the CF34-10 and the Passport. The company states that the CF34-10 – a scaled down and improved version of the CFM56. The company states that it is “GE’s most reliable engine operating day in and day out under the harshest duty of the commercial world-regional aviation”. More than 1,600 CF34-10s are in service with multiple operators and the CF34 family has amassed over 159 million flight hours to date. The Passport engine is GE Aviation’s most advanced 18,000lb+ thrust-class engine, with the company claiming that it has “99.96% dispatch reliability” and can increase the B-52’s mission range, while providing low emissions and the lowest fuel burn of any engine in its thrust-class, being “30% better than the B-52’s current engine”.

CF34-10 Engine by GE Aviation
The CF34-10 engine (above) is one of two engines being proposed by GE Aviation. Below is the Passport engine which is also being offered. Both images from GE Aviation
Passport Engine by GE Aviation

The B-52H is a long-range, all-weather strategic heavy bomber manned by two pilots, two weapon systems officers (WSO) and an electronic warfare (EW) officer. It can carry up to 80,000lb (36,287kg) of precision-guided or unguided munitions in its internal bomb bay and/or on external pylons. In recent years, the bomber has been employed in the testing of hypersonic missiles.

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