An F-35B lands on the amphibious assault ship Wasp. Cracks were found in the fuselage of a test model of the jump-jet variant of the joint strike fighter. (Lockheed Martin)
WASHINGTON — Cracks were found in the fuselage of a test model of the F-35B, the US Marine Corps variant of the joint strike fighter, Defense News has learned.
The discovery will have no impact on flights occurring on any of the three F-35 variants, but will require that the test model be shut down for two to four months while inspectors look at the issue.
“During a late August 2013 inspection of the F-35B short takeoff/vertical landing (STOVL) ground article used for durability testing, two minor cracks were identified in one of the ground article’s four primary wing carry-through bulkheads,” Kyra Hawn, an F-35 program spokeswoman, said in an Oct. 10 statement.
The cracks appeared after more than 9,400 equivalent flight hours, or roughly 17 years of flight time. The F-35 program of record requires a lifecycle of 8,000 hours per plane; the test vehicle will eventually go through a simulation of two lifetimes, or 16,000 hours.
In other words, while the cracks are hardly a good thing, this was a problem discovered after extensive stress testing designed to find such problems. That said, a fix will need to be introduced into the production line, as well as added to previously produced models.
“A combined effort by government and Lockheed Martin engineering teams is underway to address modifications to the bulkhead that will be incorporated into production and the fleet as part of the normal program concurrency process to ensure aircraft full life,” Hawn’s statement said.
Hawn added that the cost and time needed to retrofit fixes for the issue into the current F-35B fleet are unknown at the moment. About 50 of the F-35Bs will require retrofitted bulkhead repairs.
The program office estimates modifications would add “less than two pounds” to the overall weight of the aircraft.
The F-35, a stealthy fifth-generation fighter, comes in three varieties. The F-35A is a conventional takeoff and landing model; the F-35B is a jump-jet design; and the F-35C is designed for use on aircraft carriers.
The F-35B will be used primarily by the US Marine Corps, which have targeted July 2015 for Initial Operational Capacity (IOC). That IOC date will not be impacted by this issue, according to Hawn.