Flight restrictions on Lockheed Martin’s F-35 are hampering the Pentagon’s ability to conduct software tests that the plane must pass before it can be declared combat-ready by next July, according to the Pentagon’s weapons-testing office.
The start of rigorous in-flight testing on the initial software for the Marine Corps version of the fighter is already five months late and may be further delayed by the flight restrictions imposed on the 20 test aircraft and 79 training jets after an engine fire on an Air Force F-35 on June 23.
“Many test points remain blocked or difficult to achieve” because of the restrictions, Jennifer Elzea, a spokeswoman for Michael Gilmore, the Pentagon’s director of operational testing, said in an emailed statement. “This may cause further delays in completing” testing of the software, she said.
The Defense Department initially grounded the entire fleet of 99 F-35s made by Lockheed Martin Aeronautics in Fort Worth after a fire in a plane at Eglin Air Force Base in Florida forced the pilot to abort a takeoff.
The directive was later eased to impose a limit on airspeed and require an inspection of the engines, made by Pratt & Whitney, after every three hours of flight. Last week, that was further relaxed to permit test aircraft to fly six hours between engine inspections when evaluating aerial-refueling and weapons-delivery capabilities, Elzea said.
The progress of the Marine version, the most complex of the three models in the $398.6 billion program, has drawn international attention. The United Kingdom and Italy have committed to buying the version, the F-35B, which is designed for short takeoffs and vertical landings on fields and aircraft carriers.
Software is crucial to delivering the promised capabilities of the F-35 and operating its navigation, communications and targeting systems. Each plane will have more than 8 million lines of code once deployed, more than any previous U.S. or allied jet.
The software for the Marine version of the F-35, known as 2B, is undergoing verification on test aircraft to confirm that it meets contract specifications. The second phase of more rigorous software testing has been scheduled to start in October, five months later than planned, according to a June 17 Pentagon software review that was required by Congress.
Verification testing on the latest version of 2B software started a few weeks before the engine fire, so “not enough has been learned about this version to be certain of the extent” to which its capabilities have improved, Elzea said.
Lockheed spokeswoman Laura Siebert said in an emailed statement that the company continues to work with the program office “to determine the impact on F-35 flight test due to the recent grounding and current flight limitations.”