Raytheon Technologies (RTX) company Pratt & Whitney is now working on an engine core upgrade (ECU) for the F35 fighter's F135 powerplant. The U.S. Department of Defense chose the upgrade in March instead of developing a new adaptive cycle engine. That option would have cost a lot more, according to Pratt & Whitney, and would have required considerable adaptation to meet the needs of the three versions of the F-35.
The current engine iteration is performing well, but it is being increasingly taxed to provide power and cooling for onboard systems. For many years it has operated with roughly twice the amount of bleed air being drawn off than required in the original specification.
That situation will become critical with the forthcoming Block 4 aircraft, which introduces a wealth of new capabilities. Moreover, to leave the current engine unchanged would bring with it growing maintenance costs that could cost $40 billion more over the F135 engine's lifecycle. The ECU retains more than 60 percent commonality with the current F135, and the upgrade can serve as retrofits to existing engines.
The ECU program is nearing its preliminary design review in early 2024, at which point it moves into the detailed design phase. The ECU remains on schedule for deployment in 2028. While the upgrade increases thrust and aircraft range, driving efficiencies for better power management, improved reliability, and addressing the current power/cooling shortcomings are the focus.
Another RTX business—Collins Aerospace—is simultaneously developing an enhanced power and cooling system (EPACS) for the F-35 that could partner with the ECU engine to support Block 4 power and cooling requirements. EPACS fits within the existing F-35 envelope and not only meets expected Block 4 requirements but also provides additional capacity for growth.
Collins Aerospace has built a new laboratory at its Windsor Locks, Connecticut, site to test the new system, and the EPACS has recently undergone its first tests. Results show that it can provide 2.5 times the cooling rate of the incumbent system. The EPACS incorporates an air cycle system, electric power generator, and controller from Collins, along with an auxiliary power unit from Pratt & Whitney. The system provides cooling, main engine start, and emergency power functionality.