By Andrea Shalal-Esa
WASHINGTON (Reuters) - Faulty fuel lines blamed for the grounding of the Marine Corps version of the Lockheed Martin Corp
The Pentagon on Monday said it found that a fuel line built by Stratoflex, a unit of Parker Hannifin Corp
The defect caused the fuel line to detach and fail just before a training flight took off at a Florida Air Force base on January 18.
The incident led to the grounding of all 25 Marine Corps versions of the new warplane, raising questions about the program's ability to keep an aggressive flight test schedule on the $396 billion program.
U.S. military officials want all the lines produced by Stratoflex for the F-35 B-model inspected using CT scans since the variance was measured in thousandths of an inch and would not be easily detected otherwise, according to a defense official who was not authorized to speak publicly.
CT scans are most commonly used in medical procedures, but can also detect flaws within components.
Normally the lines would be inspected at a facility of Britain's Rolls-Royce Plc
But Rolls-Royce and Pratt & Whitney, a unit of United Technologies Corp
Rolls builds the lift fan used on the engine of the B-model, which can take off from shorter runways and land like a helicopter. The conventional and carrier versions of the F-35 were not affected because they don't use the same fuel lines.
Some replacement fuel lines are already available and some test pilots could resume flying by the middle of next week, said the source, who was not authorized to speak publicly.
"The third-party businesses are helping us to accelerate return to flight, (versus) sending them back to Rolls Royce in the UK," said Matthew Bates, a spokesman for Pratt & Whitney.
A spokesman for Rolls Royce said his company was working closely with the Pentagon's F-35 joint program office and Pratt & Whitney.
Neither Bates nor a spokesman for Rolls-Royce identified the companies that would perform the scans.
It also remains unclear who will pay for the additional inspections and the shipping of the fuel lines, since the problem involved faulty manufacturing, not a design flaw or maintenance problems.
The statement issued by the Pentagon's F-35 program office on Monday made it clear that it holds Pratt and Rolls responsible for inadequate quality controls. It said both companies were taking steps to improve their quality assurance and ensure product integrity.
Last year, quality issues with a parachute under the pilot's ejection seat forced the program to suspend ground and flight operations of 15 F-35s. The company responsible for the improperly packed parachutes took a proactive role in resolving the issue, and paying for the additional work.
One source familiar with the program said the Pentagon should not be expected to pay for the problems this time either.
A spokeswoman for Parker Hannifin said the company, which makes many other components for the aircraft, was working around the clock to support the Pentagon's investigation.
Lockheed is building three different models of the F-35 fighter jet for the U.S. military and eight countries that helped pay for its development: Britain, Canada, Italy, Turkey, Denmark, the Netherlands, Australia and Norway.
The Pentagon plans to buy 2,443 of the warplanes in coming decades, although many analysts believe U.S. budget constraints and deficits will eventually reduce that overall number.
(Reporting by Andrea Shalal-Esa; Editing by Lisa Shumaker)