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Pratt Rules Out Worst-Case Cause For F-35 Blade Crack

By Reuters

February 27, 2013

Pratt & Whitney is 99% sure the fan blade problem that grounded the Pentagon’s 51 new F-35 fighter jets was not caused by high-cycle fatigue, which could force a costly design change, according to two sources familiar with an investigation by the enginemaker.
Company engineers have concluded that a 0.6 inch-long (1.5 cm) crack found on a turbine blade in the engine of an F-35 jet at Eglin Air Force Base in Florida was almost certainly caused by lesser issues, such as high heat exposure or a manufacturing problem, that would be easier to solve, the sources said.
“They’re 99% sure that it’s not the worst-case scenario of high-cycle fatigue,” said one of the sources.
Flights of the single-engine, single-seat F-35 fighter could resume as early as this week if the Pentagon accepts the findings of Pratt, a unit of United Technologies Corp, after additional tests to be done Wednesday, said one of the sources, who was not authorized to speak publicly.
The Pentagon announced the grounding of all F-35 warplanes on Friday after an inspection revealed a crack on a turbine blade in the Pratt-built jet engine of an F-35 jet being tested at Edwards Air Force Base in California.
It was the second engine-related grounding in two months of the $396 billion F-35 Joint Strike Fighter built by Lockheed Martin Corp, the Pentagon’s largest weapons program.