Lockheed Martin will retrofit modified bulkheads to early production F-35Bs after cracking was found in the major structural components during fatigue testing.
Speaking at the US Navy League Sea-Air-Space conference on April 7, RAdm Randy Mahr, deputy program manager with the Pentagon’s F-35 joint program office (JPO) said a redesigned bulkhead would be installed on new-build F-35Bs from LRIP 9 onwards, and that F-35Bs built up to Lot 7 would be retrofitted during scheduled depot maintenance.
“The repair for that bulkhead for the [F-35Bs] that are out there in the fleet is known, it’s understood, and we’ll be retrofitting LRIP Lots 1 through 7,” RAdm Mahr told the conference. “On LRIP Lot 9 and forward, we have the redesign finished. The forgings for that design are already done and are sitting waiting for permission to start machining.”
Some LRIP 8 jets currently in production are already being retrofitted on Lockheed’s Fort Worth production line, while others will be retrofitted prior to delivery.
The redesign comes after an aluminium wing carry-through bulkhead cracked at the 9,000 hour mark of fatigue testing, and had started to spread to an adjacent bulkhead when testing was paused at 9,056 hours. Even though the F-35B is rated for an 8,000 hour fatigue life, it was decided to redesign the bulkhead.
RAdm Mahr said the retrofit would not affect the US Marine Corps’ planned 2015 intiial operating capability schedule.