The Government Accountability Office (GAO) is raising questions about an envisioned power and thermal management system (PTMS) upgrade for the Raytheon Technologies‘ [RTX] Pratt & Whitney F135 engine on the Lockheed Martin [LMT] F-35 fighter.

The Air Force decided to move forward on an Engine Core Upgrade (ECU) for the F135 and included $245 million for ECU in the service’s fiscal 2024 budget request, which ends the service’s Advanced Engine Transition Program (AETP) for the F-35 (Defense Daily, March 13).

Air Force Secretary Frank Kendall has said that the Air Force’s decision to pursue ECU and end AETP for the F-35 was based on affordability and that the service may have pursued AETP for the fighter “if the [AETP development] cost had been lower.”

The new comments by GAO may lend support to lawmakers who want to keep the AETP option open for the F-35. General Electric [GE] has backed its AETP-funded XA100 engine for the F-35 in lieu of the F135 ECU.

“Based on our preliminary observations, the [F-35] program did not conduct an analysis of alternatives [AoA] when determining which engine and PTMS upgrade options to evaluate,” Jon Ludwigson, GAO’s director of contracting and national security acquisitions, said in prepared testimony to the House Armed Services Committee’s air and land forces panel on March 29. “To support informed acquisition decisions, DoD typically requires programs following the major capability acquisition pathway to conduct planning activities to support the decision to move to
technology development.”

“In lieu of completing an analysis of alternatives, our ongoing work indicates that the program office completed what it refers to as a business case analysis [and released it] in March 2023 to compare different PTMS and engine options,” per Ludwigson. “The analysis evaluated preselected options for improving power and cooling by upgrading the PTMS as well as modernizing or replacing the engine. It also compares some risks associated with each option and identified potential improvements needed for multiple other air vehicle subsystems. According to program officials, they intended for the analysis to provide the services with information to help them make engine and PTMS modernization decisions. Program officials acknowledged, however, that the analysis did not follow any particular DoD guidance related to business case analysis [BCA] or analysis of alternatives.”

Without a traditional AoA or BCA, the F-35 program may lack an informed cost and schedule baseline, Ludwigson said.

F-35 program and industry officials have said that the F-35 needs a new engine or an F135 upgrade to account for the addition of new mission systems and weapons on the fighter.

Ludwigson told lawmakers on March 29 that the original F135 specifications “were not reflective of the eventual full cooling and power needs of the aircraft, which contributed to accelerated wear and tear on the existing engine.”

“Further, the existing cooling system and engine faces limits in supporting new, planned capabilities,” he testified.

Air Force Lt. Gen. Michael Schmidt, the F-35 program executive officer, said that “we have been eating into the life of this [F135] engine since the beginning of the program because we did under spec the engine.”

Andrew Hunter, the Air Force acquisition chief, testified that “business case analysis is designed to inform a decision and so, depending on what decision one is making, the way that one structures the BCA can be different.”

“I do think that the work the [F-35] JPO [Joint Program Office] performed did inform the decision that was in play at the time, which was an investment decision on what path forward to take between ECU and AETP,” he said. “And I think the Department [of the Air Force] did have the information needed to make that decision.”