Courtesy photo/Darin Russell The F-35 Joint Strike Fighter Integrated Test Force is in the process of testing the F-35A Lightning II...
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Courtesy photo/Darin Russell
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The F-35 Joint Strike Fighter Integrated Test Force is in the process of testing the F-35A Lightning II’s newest munitions asset, a four-barrel Gatling gun that fires 25 mm rounds known as the GAU-22/A.
Unlike the Marine Corps and Navy variants, the GAU-22/A is integrated internally to the U.S. Air Force's F-35A. In the other variants, the gun is mounted to the outside as a pod. A similar weapon, GAU-12, has been used on the AV-8B Harrier.
The first phase of testing started June 9, when the first shots were fired on the ground at the Edwards Gun Harmonizing Range. The test team hopes to finish ground testing sometime during August and start the airborne phase in late September. An operational gun capability will be added with a future block of software, which is in the beginning stages of testing at Edwards AFB.
The tests are done using a target practice round, the PGU-23/U, which fires from the gun but does not explode on impact.
The tricky part about this test phase is that the gun will never operationally fire on the ground. To conduct the test, they have to use software to bypass interlocks to make the aircraft think it's in the air.
The GAU-22/A uses a 25 mm shell, which is significantly more powerful than what have been used in legacy aircraft, like the F-16 (Fighting Falcon), F-15E (Strike Eagle) (and) F-15C (Eagle)-- all those aircraft use a 20 mm shell.
Integrating a weapon into the aircraft is not in itself unique, but what does make this project special is that it's being integrated into a stealth platform. In legacy aircraft, the gun fires through a hole in the outer molding. In this case, to keep the jet hidden from radar signatures, the gun will be kept behind closed doors until the trigger is engaged.
The ground tests are designed to answer questions like: does the gun door open correctly? Does the gun spin up and down correctly? Does the air flow through the vent, and is it adequate to clear the flammable gasses?
Prior to testing the integration of the GAU-22/A into the F-35A, the gun itself was tested as a standalone. It was also flown during test points without firing to ensure that the flight envelope would not overstress the gun mounts. Preparing for the ground gun fire tests in the aircraft took roughly six months.
The testing airframe, tail number AF-2, a highly modified flight sciences aircraft, and underwent four months of instrumentation modifications and had a line production gun installed for this project.
Since AF-2 is a flight sciences aircraft, it does not have all the missionized systems of full-line production aircraft. The gun will be further tested with a line production jet sometime next year for full integration.
To evaluate the gun's performance, the test team is made up of personnel from the U.S. Air Force, Lockheed Martin, Pratt & Whitney and Northrop Grumman.
Source: U.S. Air Force
