The September crash of a U.S. Marine Corps F-35 Lightning II fighter jet was caused by a faulty engine fuel tube supplied by project subcontractor Pratt & Whitney, according to a new report from congressional investigators.
In the first official statement on the incident in months, the nonpartisan Government Accountability Office said a manufacturing defect “caused an engine fuel tube to rupture during flight, resulting in a loss of power to the engine.”
The report, included in a lengthy review of the Department of Defense’s advanced weapons systems, largely confirmed what is already known about the Sept. 28 crash, in which an F-35B short takeoff variant went down near a Marine Corps air base in Beaufort, South Carolina.
The pilot ejected safely and no injuries were reported as a result of the crash.
The Pentagon in October briefly grounded its entire F-35 fleet after preliminary findings from its ongoing investigation of the accident pointed toward the potentially flawed tubing.
The Defense Department told auditors that it ultimately identified 117 aircraft with the same type of fuel tube needing replacement. Pratt & Whitney subsequently provided new fuel tubes, which were installed on most of the affected F-35s by the end of the year, according to the Government Accountability Office.
A Pratt & Whitney spokesman on Monday said the company had no comment on the watchdog’s report.
The F-35 Joint Program Office, which oversees development of the next-generation stealth fighter, said investigations by a U.S. Navy aircraft mishap board and the Marine Corps are still underway.
The September accident marked the first total loss in the F-35’s 13-year operational history and reinforced mounting concerns among defense officials and lawmakers that the notoriously pricey aircraft was still not meeting Defense Department safety standards after years of technical issues.
An F-35 engine caught fire shortly before a training mission at Eglin Air Force Base in Florida in 2014, and in 2017 several pilots assigned to Luke Air Force Base in Arizona reported symptoms of oxygen deprivation while in flight. Operators have also encountered extreme pressure in the cockpit across all variants during certain maneuvers, according to the Government Accountability Office’s findings.
No injuries were reported in connection with those incidents, and all pilots were able to land their aircraft safely.
Last month, a second F-35 crashed while on a Japanese Air Self-Defense Force training mission over the Pacific Ocean about 80 miles off the coast of the northern Aomori Prefecture.
Japanese authorities recovered floating debris from the wreck but were unable to locate the pilot. The U.S. deployed salvage vehicles and surveillance aircraft to the area in hopes of retrieving closely guarded military technology from the sunken jet and preventing its recovery by either China or Russia but called off the fruitless search late last week.
The likely fatal crash has so far baffled both American and Japanese defense officials, and neither country has suggested even a possible cause. The pilot — a 41-year-old major — did not send a distress signal before disappearing from radar, and no nearby pilots witnessed the F-35 drop into the sea.
The incident is under investigation.
Japan committed to an expanded order of 105 F-35As and 42 F-35Bs last year, and the nation’s defense minister has said that deal will not change in light of the April crash.
Bethesda, Maryland-based Lockheed Martin produces the F-35 in cooperation with numerous subcontractors, including Pratt, BAE Systems, Martin-Baker, and Northrop Grumman.
