The US Joint Program Office (JPO) has cleared seven of its F-35 JSFs to return to flight after a generator failure and oil leak on test aircraft AF-4 last Friday (March 11) saw the entire fleet grounded pending further investigation.
Aviation Week and the Navy Times reports that a newer generator installed on AF-4 may have been the cause of its primary dual generator failure, due to a “design artefact” unique to the electrical starter/generator configuration. Test aircraft BF-5 and CF-1 are also equipped with the newer system, and have remained grounded. Meanwhile, seven other F-35s installed with an older generator configuration (AF-1, 2, 3 and BF-1, 2, 3, 4) have been cleared to resume flight testing after the JPO rescinded its stop-flying order, JSF program executive officer VADM David Venlet told US Congress on Tuesday (March 15).
AF-6 and AF-7, the first two LRIP F-35s, were also fitted with the newer generator system and join AF-4, BF-5 and CF-1 in being ground bound while investigations continue.