F-35 Grounding Lifted

The F-35 joint program office authorized developmental test aircraft at Edwards AFB, Calif., and NAS Patuxent River, Md., to resume flight operations Aug. 18, following a three-week grounding. Both ground and flight ops were suspended Aug. 3 after the integrated power package on AF-4, an F-35A test aircraft, malfunctioned. The integrated power package is a turbo machine that provides power to start the engine and helps cool the aircraft. Ground operations resumed Aug. 10, with the exception of AF-8 and AF-9—the first two production aircraft to be delivered to Eglin AFB, Fla. An Air Force Safety Investigation Board is still reviewing the incident, according to a JPO release. “The root cause of the investigation indicates that an IPP valve did not function properly. Monitoring of valve position is a mitigating action to allow monitored operations. A permanent resolution is in work,” according to the release. It went on, “The completion of the root cause investigation and any corrective actions are required to return to unmonitored operations.” It is not clear how the grounding will affect the execution of system development and demonstration test flights; however, officials say there was a built-in margin in the test schedule to accommodate such incidents.