F-35 engine upgrade clears key design review, Pratt says

A Pratt & Whitney F135 engine undergoes accelerated mission testing in Sea Level Test Cell 3 at Arnold Air Force Base, Tenn., Nov. 15, 2021. (U.S. Air Force photos by Jill Pickett)

NATIONAL HARBOR, Md. — An upgrade for the F-35 stealth fighter’s engine has passed a crucial design review, teeing up the program to move into subsequent testing and eventually production, according to a top executive at manufacturer Pratt & Whitney.

“It means that we’ve been working integration work with the airframe. It means that the design is solid. It means that we’re ready to move forward from an industrial base as well,” Jill Albertelli, president of Pratt’s military engines business, said of the design review in an interview with Breaking Defense on Monday. (Today, Pratt’s parent company RTX announced that Albertelli has been promoted to serve as Pratt’s president, effective Jan. 1, 2027.)

The enhancement, known as the Engine Core Upgrade (ECU) for the stealth fighter’s F135 powerplant, specifically passed what’s known as a risk reduction design review. Albertelli explained on the sidelines of the Air and Space Forces Association conference here that the milestone is essentially the same as a critical design review — Pentagon parlance for analysis that confirms a system design will perform as expected, among other criteria.

About one-third of unique hardware for the first engine to test in the upgrade program is “in process,” Albertelli said.

Among the next steps is the first engine test, according to Albertelli. She declined to comment directly on when specific milestones are planned and referred questions to the F-35 Joint Program Office. A top Air Force official, however, previously told reporters that ground testing will kick off in 2027, followed by flight testing around 2030.

When Pratt pushed the ECU plan several years ago, officials projected the program could be ready to enter service by 2028. But according to a review by the Government Accountability Office last year, ECU production isn’t slated to begin until 2031.

Asked about Pratt’s assumptions for fielding ECU, Albertelli said, “We always want to make sure we are giving the customer what they’re prioritizing,” noting as well that “funding isn’t unlimited, so we have to balance those equations on what the need is.” Pratt, she emphasized, is “meeting [the government’s] milestones.”

Military officials say the engine program will deliver greater thrust and fuel efficiency. The upgrade is also meant to restore expected engine life and support a suite of forthcoming upgrades known as Block 4 .

The engine upgrade — which officials selected after passing over a whole new, so-called “adaptive” propulsion system for the F-35 — will save “tens of billions” of dollars in maintenance costs compared to foregoing an enhancement for the F135, Albertelli said.

All three variants of the F-35 are expected to benefit from the ECU, which is planned to be retrofitted into existing jets. The Pentagon recently awarded a roughly $240.8 million modification for ECU work, following a $1.3 billion base contract issued in September 2024.

2021年11月15日，一台普惠F135发动机在田纳西州阿诺德空军基地的3号海平面测试舱内进行加速任务测试。（美国空军照片，摄影：吉尔·皮克特）

马里兰州国家港——据制造商普惠公司的一位高管称，F-35隐形战斗机发动机的升级方案已通过关键的设计审查，为该项目进入后续测试并最终投入生产做好了准备。

“这意味着我们一直在与机身进行集成工作。这意味着设计方案已经成熟。这也意味着我们已经准备好从工业基础层面推进项目，”普惠公司军用发动机业务总裁吉尔·阿尔贝泰利周一在接受《防务新闻》采访时谈到设计评审时表示。（今天，普惠公司的母公司RTX宣布，阿尔贝泰利已晋升为普惠公司总裁，将于2027年1月1日生效。）

这项名为“发动机核心升级”（ECU）的改进方案，是针对隐形战斗机F135发动机的，它通过了一项名为“风险降低设计评审”的专门审查。阿尔贝泰利在空军和太空部队协会会议间隙解释说，这一里程碑式的审查本质上与关键设计评审相同——这是五角大楼对关键设计评审的术语，指的是确认系统设计能够按照预期运行的分析，以及其他一些标准。

阿尔贝泰利表示，升级计划中首台待测试发动机的独特硬件约有三分之一“正在研发中”。

据阿尔贝泰利透露，下一步工作包括首次发动机测试。她拒绝直接评论具体里程碑的计划时间，并将问题转给了F-35联合项目办公室。不过，一位空军高级官员此前曾告诉记者，地面测试将于2027年启动，飞行测试则预计在2030年左右进行。

几年前，普拉特公司力推ECU计划时，官员们预测该计划可能在2028年投入使用。但根据美国政府问责局去年的一项审查，ECU的生产预计要到2031年才会开始。

当被问及普拉特公司部署ECU的假设时，阿尔贝泰利表示：“我们始终希望确保为客户提供他们优先考虑的服务。”她还指出，“资金并非无限，因此我们必须根据实际需求来权衡利弊。”她强调，普拉特公司“正在按时完成（政府设定的）里程碑”。

军方官员表示，该发动机升级项目将提升推力并提高燃油效率。此次升级还旨在恢复发动机的预期寿命，并为后续一系列名为“Block 4”的升级项目提供支持。

阿尔贝泰利表示，与放弃对 F135 进行改进相比，官员们最终选择了发动机升级方案，而不是为 F-35 配备全新的所谓“自适应”推进系统。升级后的发动机将节省“数百亿美元”的维护成本。

所有三种型号的F-35战机预计都将受益于电子控制单元（ECU），该控制单元计划改装到现有战机上。五角大楼最近授予了一份价值约2.408亿美元的ECU改装项目合同，此前该公司于2024年9月签署了一份价值13亿美元的基础合同。