A Pratt & Whitney F135 engine undergoes altitude testing at the Arnold Engineering Development Center. An engine issue forced the fleet to pause flying over the weekend. (US Air Force)
WASHINGTON — Flights of the F-35 joint strike fighter were temporarily halted over the weekend in order to inspect an engine valve, the Pentagon said Monday.
Pentagon officials halted flights Friday in order to inspect the oil flow management valve fitting inside the F135 engines that power the fighter. However, the program office says most F-35s are back flying. The engines are manufactured by Pratt & Whitney.
The decision to inspect the valve was made following a Tuesday incident where a Marine piloting an F-35B model near the service’s Yuma, Arizona, base was forced to make an emergency landing after the plane began warning of oil loss. There were no injuries involved in the incident, but program officials ran an analysis of the situation and concluded the problem could be widespread enough that they required an analysis of the fleet.
That engine issue has been identified as a “supply line to engine bearings and a Rosan fitting that separated from the body of the [valve],” according to a Pentagon statement by program spokeswoman Kyra Hawn.
The statement also noted that the problem was found in three engines inspected at Yuma, but none at the other test sites flying the F-35.
“This one-time fleet-wide inspection takes approximately 90 minutes per engine,” Pratt spokesman Matthew Bates said, before adding that “nearly all” aircraft were back and flying by Saturday evening. Bates said the company anticipates concluding inspections by the end of Monday.
The decision to ground the fleet came just hours after top program officials told reporters during a conference call that the F-35 was largely moving forward as planned.
It’s a potential black eye right before a pivotal movement for the fighter — first flight over international soil at the Farnborough Air Show in July. Program supporters have hailed the plane’s appearance at the show as a milestone achievement that proves the program is on the right track; it could also serve as a way to entice more international customers to consider the plane.
However, a spokesman for Lockheed Martin says the company has not altered plans for flying at the air show.
Richard Aboulafia, an analyst with the Virginia-based Teal Group, said this issue should not be seen as a larger indictment of the program as a whole.
“Glitches are a problem with a complicated program, and the F-35 certainly is no exception,” he said. “It’s far more complicated than most new programs. This is just one of many headaches.”■