* Investigation under way to determine cause
* Engine being taken off test line (Adds comment from congressional aide)
By Andrea Shalal-Esa
WASHINGTON, Sept 13 (Reuters) - United Technologies Corp (UTX.N) on Sunday said the forward section of the F135 engine it builds for the Lockheed Martin Corp (LMT.N) F-35 fighter jet was damaged during a qualification test on Friday.
Pratt & Whitney, the United Technologies unit doing the work, said an investigation was ongoing and it was working closely with Lockheed and the Pentagon’s F-35 program office to find the root cause of the problem and resolve the issue.
Pratt spokeswoman Erin Dick said the issue was not expected to affect the F-35 flight test schedule since those aircraft are powered by the first generation of the F135 engine, which has been fully tested, while the damage occurred to a second generation of the engine that was still being tested.
The company said the engine would be taken off the test line, but the F-35 program office estimated it would take five days to determine root cause and any corrective action.
The incident comes just after the Pentagon launched an independent assessment of projected cost growth in Pratt’s F135 engine, and could provide fodder for backers of a multibillion- dollar program to develop an alternate F-35 engine that the Obama administration calls wasteful.
President Barack Obama and Defense Secretary Robert Gates say the Pratt engine is performing well, and the fighter does not need an alternate engine that is being developed by General Electric Co (GE.N) and Britain’s Rolls-Royce Group PLC (RR.L).
Pratt said the incident occurred during a qualification test on an F135 engine built for the conventional takeoff and landing version of the fighter to be flown by the Air Force.
It said there was no damage to the turbine section of the engine, which was redesigned after problems two years ago.
A company program expert said the incident occurred on Friday evening, during the fifth of 11 hours of planned testing of the engine under supersonic conditions, when the engine began producing “sparks out the tail pipe.”
He said the damage was mostly to the first and second fan blades, and the engine continued to run and produce thrust.
Pratt had completed about 95 percent of the qualification test when the incident occurred, and the engine had run through 2,455 cycles, an amount equal to eight years of operation, he said, adding, “This engine was pushed very, very hard.”
It was not immediately clear if the incident occurred because the engine ingested some foreign object, such as a nut or bolt from testing equipment, or if the damage resulted from some manufacturing defect or a structural issue triggered by the supersonic conditions, said the program expert.
To fix the damaged engine, the company would have to make some “very specific targeted hardware replacements,” but not a significant overhaul of the entire engine, the expert said.
Dick said the company wanted to disclose incident as quickly as possible, especially given the ongoing debate over funding for the alternate GE-Rolls engine. “We recognize that this is a heated discussion. We wanted to make sure that we got the right information out as quickly as possible,” she said.
Dick said Pratt had had relatively few incidents during the development of the new F135 engine, partly because it was based on the Pratt F119 engine that powers the F-22 fighter jet.
Gates recently said most of the high-risk elements associated with the F-35 had been addressed. He said he continued to oppose funding for the GE-Rolls engine and that engine could face similar problems later in its development.
One congressional aide, who asked not to be named since funding for the second engine is still being debated, said the latest problem with the Pratt engine further underscored the importance of continuing competition for the F-35 engine.
“There is no way you can say that the highest risk is behind us,” said the aide, noting that the Pentagon’s own testing director had said the F-35 program had significant risk due to the concurrent production and testing of the plane.
Dick said this incident showed that having a single engine did not make the F-35 more susceptible to a fleetwide grounding. The program office had not ordered any hold on flight testing because the engines powering the test aircraft were from an earlier generation, while this incident occurred with a “second-generation” engine, or later model.
“If you have something that impacts one generation, you still have the other previous generations that have been proven,” she said, calling the chance of a fleetwide grounding that would affect all generations “almost nill.” (Reporting by Andrea Shalal-Esa, editing by Maureen Bavdek and Diane Craft)