Might Make a Faster Pig

GE's entry


Pratt & Whitney's version

Or they might make a pig with longer range.

But it will still be a pig.

The pig in question is the F-35, and the addition of a variable cycle engine might increase its performance:

The U.S. Air Force is poised to award General Electric and Pratt & Whitney contracts for adaptive cycle technology development that will pave the way toward an active procurement program for a sixth-generation fighter engine as well as the potential reengining of the F-35 Joint Strike Fighter.

Contracts for the Air Force Research Laboratory’s (AFRL) Adaptive Engine Transition Program (AETP) are expected to be valued at up to $1 billion apiece for the two engine-makers, setting the stage for a 21st-century version of the “great fighter engine war” between GE and Pratt over dual-sourced engines for the F-15 and F-16. Although Pratt now runs both key U.S. military development programs with the F135 for the F-35 and the engine for Northrop Grumman’s B-21 Long-Range Strike Bomber, AETP opens up potential competition for both the reengining of F-35s as well as proposed sixth-generation fighters for the U.S. Navy and Air Force.

AETP is specifically aimed at maturing three-stream engine technology now considered vital to achieving the high-speed, long-endurance performance requirements of the Navy’s future F/A-XX and the Air Force’s F-X sixth-generation fighters. Although it remains unknown whether the F/A-XX will emerge as a twin-engine design, the three-stream concept is designed to be scalable across a wide thrust range. The AETP is, however, targeted initially at a 45,000-lb.-thrust-class engine baselined to fit within the existing confines of the F-35A engine bay. This makes it a contender to replace the F135 from the mid-2020s onward.

………

The third stream provides an extra source of air flow that, depending on the phase of the mission, is designed to provide either additional mass flow for increased propulsive efficiency and lower fuel burn, or additional core flow for higher thrust and cooling air. It also can be used to cool fuel that provides a heat sink for aircraft systems. The third stream can also swallow excess air damming up around the inlet, improving flow holding and reducing spillage drag.

At the heart of adaptive engines are variable-geometry devices that dynamically alter the fan pressure ratio and overall bypass ratio, the two key factors influencing specific fuel consumption and thrust. Fan pressure ratio is changed by using an adaptive, multistage fan. This increases fan pressure ratio to fighter engine performance levels during takeoff and acceleration, and, in cruise, lowers it to airliner-like levels for improved fuel efficiency. The third stream, which is external to both the core and standard bypass duct, is used to alter the bypass ratio.

I think that the cooling application might be the most important.

Both the F-22 and F-35 are basically thermos bottles which rely on their fuel as a heat sink for cooling other systems, which creates issues when the aircraft sits on the tarmac too long, or when the fuel becomes hot sitting in the sun, which has the USAF repainting all their fuel trucks white.

Any potential improvement in range or performance would be important for the F-35, which is shaping up to be a major pig.