Lockheed Martin has resumed conducting test flights of the new F-35 Lightning II fighter jets after fixing an engine issue that grounded part of its worldwide fleet.
“We resumed F-35 production flight operations today following an F135 engine mitigation action. Safety remains our top priority as we continue to produce the world’s most advanced aircraft,” Lockheed Martin said in a statement published on March 6, 2023.
The resumption marks the end of a three-month saga which started with an F-35 crash landing at a Naval Air Station Joint Reserve Base in Fort Worth, Texas, on December 15, 2024.
A number of F-35 jets were grounded following the crash, and the authorities began an investigation into the cause of the engine issues that caused the incident.
The incident also resulted in a delivery pause on new Pratt & Whitney F135 engines for the aircraft, with testing of the newly assembled aircraft also paused
The engines were found to be affected by “rare system phenomenon involving harmonic resonance,” Pratt & Whitney later explained, as the companies scrambled to find a solution for the problem.
The fix was only found in late February 2023, and the US Department of Defense (DoD) gave the green light for engine deliveries to resume.
The DoD also recommended rolling out the fix, said to be “inexpensive and non-intrusive”, on all aircraft of the global F-35 fleet, despite claiming that the vibration issue was “very rare”.
The almost three-month long delivery pause, and the partial grounding of the F-35 fleet took its toll on combat capabilities of the model. According to a report by the US Congressional Budget Office, availability of A and B variants of the aircraft dropped in 2022 compared to 2021, showing that the jet was less combat-ready than before.