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F135 Damage 'Significant' Or Easy Fix?


UPDATED: Congressional Staffer Questions Pratt; OSD Document Says Damage to Engine Was "Significant"

This is a tale of at least two perspectives. Pratt & Whitney says it knows what failed on the F135 test engine and can fix it relatively painlessly. The company has identified a "worn bushing" as the likely cause of the recent test engine failure and can make changes to the engine "with little to no impact on cost or schedule," a senior company official said.

"During a recent qualification test on an F135 CTOL engine, an incident occurred resulting in damage to the forward section of the engine. Pratt & Whitney conducted a thorough review and inspection of the engine," the senior program official said.

The investigation found that a worn bushing is the "potential cause, which tells us this issue can be addressed with little or no impact on cost or schedule. Pratt & Whitney will immediately implement a minor modification to the fan section for all F135 initial service release (ISR) flight and production engines. This modification can be incorporated into an assembled engine without teardown," the senior program official said.

But a congressional aide, told of Pratt's comments, dismissed them, saying that the company was trying to make things look as good as possible to protect the company while funding for the engine programs is decided.

The aide noted that a Sept. 14 Pentagon fact sheet about the incident says that the engine damage was "significant."

A Pratt spokesman said "we can argue about significant and whether it is or not."

However, the congressional aide also noted that this is the third failure the F135 has experienced, adding that caution is warranted given that significant problems with the F100 engine that powers most F-15s and F-16s "didn't really show themselves until two years after initial operational capability."

The OSD document says that "an approximately 1 inch by 1.5 inch piece separated from a blade on Rotor 1 of the fan. At the time the separation occurred, High Cycle Fatigue sweep tests were being conducted, but high loads at this location on the fan blade were not expected."

The OSD document said the engine would "undergo tear down and root cause analysis. This is a lengthy process that includes very detailed metallurgy and crack propagation analysis and will take several weeks."

The Pratt spokesman said the company "will continue to do further metallurgical examination" but did not need to tear down the entire engine. The fixes to the blades are "imminent" and will be done as each engine comes down the line, the spokesman said.

No decision has yet been made about the failure's impact on the test program, the OSD document says. The engines being used for current flight tests "uses an older design of this fan airfoil, and is not expected to exhibit a similar problem," the OSD document adds.

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