The Defense Department last week took a step toward fixing a F-35 fuel system issue first discovered in late 2014.
F-35 Joint Program Office (JPO) spokesman Joe DellaVedova said Thursday in an email that a “low-probability” potential for air in the F-35 fuel system to over-pressurize the fuel tanks beyond design limits was discovered in late 2014 during lightning protection qualification and was confirmed via flight test in early 2015. He said Tuesday if air in the fuel system over-pressurized to the point of a structural failure, the fuel tank could leak.
DellaVedova said Tuesday a precautionary flight limit of a lower acceleration limit while at high fuel quantities was implemented. This, he said, is to control the pressures until a corrective action can be implemented. DellaVedova said the potential for over-pressurization exists on all F-35 variants.
The Navy on Jan. 12 issued F-35 prime contractor Lockheed Martin [LMT] a $29 million not-to-exceed, cost-plus-fixed-fee delivery order providing for air vehicle retrofit modifications associated with F-35A fuel tank overpressure engineering change proposal in support of the Air Force and Australia, Italy, the Netherlands and Norway (Defense Daily, Jan. 15). DellaVedova said this contract action will retrofit 41 F-35As. Additional aircraft, he said, will receive this modification utilizing currency funding provided under previously-awarded low rate initial production (LRIP) contracts.
DellaVedova said the F-35A fuel tank overpressure engineering change proposal as referenced in the Jan. 12 contract award will install pressure relief valves that will enable removal of associated flight limits. He said the valves were successfully flight tested in December and modifications are scheduled to begin this month to support Air Force initial operational capability (IOC) in August. Lockheed Martin, he said, is currently working an engineering change proposal for correction of the over-pressurization issue for the F-35C variant.
F-35 JPO did not respond to requests for comment by press time Tuesday. Lockheed Martin declined to comment for this story.