Pratt & Whitney has changed its proposed upgrade path for the F135 engine powering the F-35 Lightning II stealth fighter. It is now offering two stages of improvements over a four-year period, compared with the three-stage, 10-year plan ending with a completely new engine that it
revealed a year ago. The stages are labeled Growth Option 1.0 and 2.0 and include greater thrust, lower fuel burn, and better thermal management.
Matthew Bromberg, president of P&W Military Engines, told
AIN that since last year, P&W has combined the informally labeled “Growth 1A” thrust-increase option for the F-35B STOVL version within the overall Growth Option 1.0 package. This package offers 10 percent more thrust than the F135’s current nominal 40,000 pounds and 5 percent better fuel burn. But for the F-35B, P&W is working with Rolls-Royce to also provide a 5 percent increase in vertical thrust during the hover.
P&W previously described Growth Option 2.0 as an all-new production engine that would result from its adaptive-cycle research and development under the U.S. Air Force Research Laboratory Advanced Engine Transition Program (AETP). Both General Electric and P&W are working on engineering, manufacturing, and development (EMD) contracts from the Pentagon for the AETP, which could power a sixth-generation fighter aircraft.
However, Bromberg said that Growth Option 2.0 for the F135 could now provide the F-35 with “a significant increase in power and thermal management capability” within four years, rather than being a completely new engine design, which might not be available until a decade hence.
P&W is offering the new optional package as a result of the perceived need for an improved power and thermal management system (PTMS) to accompany the upgrades to the F-35 that Lockheed Martin is proposing. Lockheed Martin describes these as a continuous capability development and delivery (C2D2) strategy, but some are also known as the Block 4 upgrade. The upgrade program is scheduled to begin next year but is still under negotiation by the F-35 Joint Program Office.
The Growth Option 2.0 upgrades will result from P&W’s adaptive-cycle R&D effort focusing on third-airstream capability, adaptive-cycle controls, and new materials, with the company planning to “take the technologies as they mature and insert them into existing engines,” said Bromberg. “It’s a whole suite of technologies; we will look at everything. We’re leveraging the bleed systems, the integration system, and the control system.” In addition to the adaptive-cycle fan’s third airstream, P&W is also “looking at adaptive elements in the controls, the components, and the core,” he said.
