The U.S. Air Force grounded most Lockheed Martin F-35As on July 29 to inspect a component in the stealthy fighter’s ejection seats that manufacturer Martin-Baker said could be faulty, a service spokesman says. 

The stand-down order reverses the Air Force’s original decision to continue flying the F-35A fleet despite the known flaw, even as several other U.S. military fleets with Martin-Baker ejection seats paused some operations to deal with the issue. 

In mid-July, Martin-Baker informed operators of a defect that affects a certain range of serial numbers for cartridge actuation devices, which ignite to propel the seat out of the aircraft and deploy the parachute. The defect affected multiple seats, including the Mk. 14, SJU-5/6, Mk. 16 and the F-35 fleet’s US16. 

In response, the services published Time Critical Technical Directives in mid-July, ordering inspections of cartridges with the affected serial numbers. Cartridges that fail inspections can be replaced by maintainers at the squadron level, which avoids the need for an unscheduled depot visit. 

Although the US16 seat is affected, the Air Force said on July 28 there were no plans to ground the F-35A fleet due to the problem. The US16 has dual-redundant initiators for the cartridges, which the Air Force said mitigated the safety risk. The Air Force also grounded portions of its Northrop T-38 and Beechcraft T-6A trainer fleets.

But the service decided to stand-down F-35As on July 29 in order to expedite the process of inspecting all of the cartridges exposed to the production defect, an Air Combat Command spokesman says.

The US16 ejection seat also is equipped on F-35Cs flown by the Navy and Marine Corps and F-35Bs flown only by the Marines. Spokespersons for both services had not yet responded to calls and emails about the status of the F-35B and F-35C fleets. 

The issue is limited to the fleet types equipped with Martin-Baker ejection seats. Most Air Force fleets, including the Lockheed F-22 and F-16, Boeing F-15 and T-7A, Fairchild Republic A-10 and all of the bombers, use versions of the Collins Aerospace Advanced Concept Ejection Seat.