The F-35 Joint Strike Fighter program is on a roll with gun trials of the Air Force version of the jet underway just ahead of a declaration by the Marine Corps that its model is battle ready, which was expected to come any day within the week of July 27.
Ground testing of the F-35A’s four-barrel 25mm Gatling gun began June 9 at the gun harmonizing range at Edwards Air Force Base in southern California, according to a statement released July 23 by the base command.
The General Dynamics [GD] GAU-22/A cannon is internally-mounted in a “blister” on the Air Force F-35A’s left wing. The Marine Corps F-35B and Navy F-35C will have the option of carrying the gun externally in a belly-mounted pod. The gun is a more powerful version of the GAU-12 used on the AV-8B Harrier jump jet that the F-35B will replace. The 25mm round is larger than that carried by any of the Air Force’s legacy fighter aircraft, which fire 20mm rounds.
First shots were fired from an Air Force F-35 designated AF-2, a specially instrumented aircraft to gather data on stress loads and other metrics during the burst firing. Engineers are checking multiple systems connected to the gun’s operation, including the opening and closing of the door through which the rounds are fired, the spinning of its four barrels, air flow through vents that siphon off flammable gases and that the airframe itself can withstand the forces exerted by firing the powerful cannon.
Air Force and Lockheed Martin [LMT] engineers hope to finish ground testing sometime during August and start the airborne phase late September. Lockheed Martin is developing the F-35 along with BAE Systems and Northrop Grumman [NOC].
Integrating the internal gun with the F-35 is a unique challenge because the aircraft must maintain its stealth capabilities. Therefore, the cannon fires through a door that lifts up, creating a hole in the outer skin of the aircraft when the pilot pulls the trigger, then lowers back into place preserving the aircraft low radar signature.
The cannon already has been test fired independent of the aircraft and has been flown without firing to test the gun’s mounts during flight maneuvers. AF-2 was specially outfitted with instruments and data sensors over a six-month period prior to the ground test firing. It is not outfitted with the same avionics and other operational equipment that a production aircraft has. The gun will be tested with a production aircraft sometime in 2016 prior to the Air Force’s IOC declaration. At IOC, the Air Force’s jets will have a version of the F-35’s mission systems software that will not initially allow for operation of the cannon. Gun functionality will come with later software iterations.
Meanwhile, the Marine Corps is on the cusp of declaring its first operational F-35 squadron ready for combat. An operational readiness evaluation of VMFA-121 at Marine Corps Air Station Yuma, Ariz, was wrapped up about 10 days ago and has been passed up the chain of command all the way to Commandant Gen. Joseph Dunford. He is expected to declare IOC before the end of July.