Structural defects mean the earliest F-35Bs delivered by Lockheed Martin could reach a service life limit by 2026 after 2,100 flight hours, according to the Pentagon’s director for weapons testing.
The design specification of the F-35B called for a service life of 8,000 flight hours, but early production models fall “well under” the durability requirement, Robert Behler, director of operational test and evaluation (DOT&E,) wrote in his latest annual report to Congress.
The new DOT&E assessment comes after several years of durability testing that exposed multiple structural cracks. Lockheed completed two service lifetime cycles of durability testing on a static F-35B airframe called BH-1, but canceled a plan in February 2017 to perform a third series.
Structural redesigns, including a new approach for the wing-carry-through, had made BH-1 unrepresentative of the final production standard, the DOT&E report states. The F-35 program has obtained funding to acquire a new structural test article, but it was not yet on contract, the report adds. Bloomberg first reported the DOT&E’s findings on the F-35 program.
“Items identified in the Annual DOT&E report are well understood and have been resolved in partnership with the F-35 Joint Program Office or have an agreed path forward to resolution,” Lockheed said in a statement to Aerospace DAILY.
Planned design changes should allow the early F-35Bs to meet the service life requirement of 8,000 flight hours, a program source says.
Lockheed also discontinued durability testing on a static test article for the F-35C last September instead of beginning a third life cycle assessment, the DOT&E said. The F-35A completed three full life cycles of durability testing, by contrast.
Behler’s office also remains skeptical about the F-35 program’s decision to reorganize parts of the Block 4 modernization plan. Instead of rolling out large increments every two years, the Continuous Capability Development and Delivery plan adopted a year ago calls for releasing smaller software updates adding new features every six months.
The six-month release cycle for the aircraft’s mission systems is not matched with the upgrade schedule for the F-35’s support systems, such as the Autonomic Logistics Information System, mission data and training simulators, Behler’s report states.
The DOT&E is also critical about the readiness of the F-35’s Block 3F software a month after the program entered a critical testing phase. Software updates and fixes rolled out by Lockheed reduced the number of Category 1 deficiencies to 13 in December from more than 100 last May. The program later added two more Category 1 deficiencies to the list after the F-35 entered the initial operational test and evaluation phase on Dec. 5, the report states.