F-35 Grounding Could Last Weeks

By Bill Sweetman william_sweetman@aviationweek.com WASHINGTON

Flight and ground tests of the 20-strong F-35 Joint Strike Fighter force could be suspended “for a few weeks,” according to an industrial source close to the program, after the secondary power system of F-35A AF-4, a USAF-variant test aircraft, failed on Aug. 2 at Edwards AFB, Calif., during a ground maintenance engine run. However, another government source says that foreign object damage has not yet been ruled out, and notes that such a finding would allow a more rapid return to flight. A clearer picture is expected to emerge next week. The failure occurred in the integrated power pack (IPP), which combines the functions of the engine starter, emergency and auxiliary power unit, environmental control system and backup generator. This is the third grounding inside a year for the Lockheed Martin program, but the first for which ground operations were also suspended. In October, a potential problem with software controlling the fuel pump was detected in ground tests and flights were suspended while a fix was installed. In March, AF-4 lost both engine-driven starter-generators in flight. That grounding was traced to a redesigned generator, allowing earlier aircraft to return to flight within days, and the problem was ascribed to a maintenance error. F-35 flight testing has been running ahead of the revised schedule that was adopted as part of the restructuring and stretch-out announced in January. At the Paris air show this year, deputy program office director USAF Maj. Gen. C.D. Moore said the flight test success would provide the program with margin, but not allow the schedule to be brought forward.

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