Pratt & Whitney is refining its proposed upgrade path for the
Joint Strike Fighter engine to include increased power and thermal management system (PTMS) capability following feedback on its initially proposed upgrade package from the
Joint Program Office.
Additional power and thermal management capability will enable the use of directed energy weapons and other advanced offensive and defensive systems and, if approved, would feature in an upgrade package called Growth Option 2.0 (GO2). Pratt & Whitney, which would roll PTMS into a suite of compressor and turbine enhancements originally proposed in the first upgrade package, G01, says the complete upgrade could be available within four years of getting the official go-ahead.
Growth Option 1.0, which was floated with the JPO in 2017, offered 5% fuel reductions and as much as 10% higher thrust. Offered as a cost-neutral upgrade, it was always meant to form part of a longer-term, two-stage improvement road map for the F-35 engine under plans first unveiled by the manufacturer in 2015. However, with the move to combine GO1 and 2 into a more complete enhancement package, Pratt is tailoring the revised proposal to closer match the F-35 upgrade road map recently outlined under the C2D2 continuous improvement strategy.
GO1 builds on core technologies evaluated from 2013 onward using the modified F135 test engine XTE68/LF under the U.S. Navy-sponsored fuel-burn reduction (FBR) program. It also incorporates design improvements developed under the U.S. Air Force-supported component and engine structural assessment research (Caesar), which focused on the
engine for the
, the predecessor to the F135 powerplant.
Though focused on integrating enhanced thermal management, GO2 will leverage more of the adaptive engine technology features in development at Pratt through air force and navy-supported initiatives. These largely stem from the air force-led adaptive engine technology demonstration (AETD), as well as the follow-on adaptive engine transfer program (AETP), which is targeting development of the XA101 variable-cycle engine for sixth-generation fighters.
The chief focus for these new AETD, AETP and XA101 engine cycles is the addition of a third airstream to provide additional either added combat power or range, depending on the phase of the mission. However, the “GO” upgrade packages can take advantage of the broader variable-cycle approach, says Matthew Bromberg, president of Pratt & Whitney Military Engines. “‘Adaptive’ refers to many other elements of the engine as well, not just the third stream. Yes, there is a third stream, but we are also looking at adaptive elements in controls and components inside the engine such as an adaptive turbine.
“We have widened the aperture and are looking at adaptive elements across the engine,” he adds. “As these mature we will look at what we can do with the technology in an existing engine, and that’s the concept in GO1. And GO2 is exactly the same thing. It just adds the PTMS capability that we missed last year. We didn’t have that in terms of the requirements when we packaged GO1, and that was the feedback we got from the customer. With a PTMS solution, this can meet all the C2/D2 requirements, and I think that’s compelling.”
Designed to be a drop-in replacement for the current engine, the GO2 package will not require other system upgrades outside of the propulsion system. “There’s more we can do with
and other suppliers if we go outside the engine, but this is all within the engine,” says Bromberg. Although providing few specifics, he adds, “It is leveraging all the bleed systems, the generation systems.”
Pratt meanwhile continues tests of the new technology future fighter engine core that will provide the basis for the XA101. Although the company declines to offer any details of the work, it follows the successful completion of tests of a three-stream fan system on a modified F135 under the AETD program. Results from the core tests will feed into the AETP effort that forms the basis for the XA101 engine.
