Marine F-35 Fighter Jet Nearly Shoots Itself Down

One shell from the fighter's externally mounted GAU-22 cannon exploded immediately after leaving the muzzle, damaging the stealth fighter's fuselage. It remains unclear whether the pilot was triggering the GE-designed General Dynamics four-barrel rotating "gatling" cannon at the time, or if the discharge was accidental.

On the F-35B and C naval variants, the 25-mm GAU-22 is mounted on a pod slung under the fuselage, well aft. Meant for both close-in air-to-air dogfighting and ground attack, it fires at a rate of 3,300 rounds per minute and carries 220 rounds---just four seconds' worth. The U.S. Air Force F-35A carries its GAU-22 internally and fires through an opening above the wing on the left side of the aircraft.

The ammunition in the Marine F-35B was reported by Military.com as PGU-32 semi-armor-piercing high-explosive incendiary tracer, meaning each shell emits a visible glow as it travels toward the target so the pilot can track it. Cannon shells are meant to explode on impact, but this one appears to have detonated prematurely---extremely prematurely. Muzzle velocity of the GAU-22 is reported as 3,280 feet per second, so if the round blew under the fuselage, it would have done so around 1/200^th of a second after leaving the muzzle.