A U.S. Marine Corps F-35B Joint Strike Fighter was significantly damaged when a round fired from its underbelly 25mm gun pod exploded shortly after leaving the muzzle of the cannon mounted within.
on Mar. 12, 2021, F-35B with VMX-1, the U.S. Marine Corps’ test and evaluation squadron based at MCAS (Marine Corps Air Station) Yuma, Arizona, was damaged during a night CAS (Close Air Support) mission .
According to Military.com’s Oriana Pawlyk, who was the first to report about the mishap, the F-35B was operating over the Yuma Range Complex, when a PGU-32/U Semi-Armor Piercing High Explosive Incendiary-Tracer (SAPHEI-T) 25mm round exploded after leaving the fighter’s GAU-22 gun pod.
The aircraft landed safely and the mishap did not result in any injury to personnel, however, the incident is categorized as a Class A mishap.
Class A is the most severe level in the U.S. military’s mishap scale, which covers incidents in the air and on the ground.
For aviation accidents, Class A mishaps are defined as those resulting in at least $2.5 million in property damage, or the total loss of the aircraft, or one or more individuals being killed or permanently disabled.
An investigation is ongoing and, at present, it’s not even clear whether the round was fired deliberately.
The F-35B, as well as the F-35C, can only carry the 25mm GAU-22/A Gatling-type automatic cannon in an underbelly pod, known as the GPU-9/A, while the F-35A has this weapon installed internally.
The first live-fire tests of the gun pod took place in 2016. Despite concerns about the accuracy of the weapon in the past, it has since been cleared for at least some level of operational use, notably being fitted to Marine F-35Bs supporting the withdrawal of U.S. forces from Somalia between December 2020 and January 2021.
Some people have compared the latest stealth aircraft’s mishap with the bizarre incident that occurred on September 21, 1956, when a U.S. Navy Grumman F-11F Tiger collided with its own 20mm cannon shells in flight. That aircraft was completely destroyed in the incident and the pilot was wounded.
In 2018, a Belgian F-16AM Viper fighter jet’s 20mm M61 Vulcan cannon let loose a string of rounds during an apparent inspection. That weapon was loaded with high-explosive ammunition and the incident left another F-16AM destroyed and a third damaged, as well as two ground crew personnel injured.