Chapter 6 M61A1 Gun Installation

CHAPTER 6 M61A1 GUN INSTALLATION Gun systems installed in high-speed aircraft must meet demanding performance requirements and provide firepower. The General Electric M61A1 20-mm automatic gun system, installed in the F-14 and F/A-18 aircraft, meets these requirements. The M61A1 (fig. 6-1) is a six-barrel, rotary-action, automatic gun based on the machine-gun design of Richard J. Gatling. The gun consists of a revolving cluster of barrels. Each barrel is fired once per revolution. The M61A1 automatic gun is hydraulically driven, electrically controlled, and can fire M50 and PGU-series ammunition at 4,000 to 7,200 rounds per minute. As installed in Navy aircraft, the gun has a pilot selectable firing rate of either 4,000 (GUN LOW) or 6,000 (GUN HIGH) rounds per minute. It is designed for either air-to-ground or air-to-air gunnery missions. Ammunition is supplied to the M61A1 gun by an ammunition handling and storage system that functions within a specific aircraft. The system uses an endless conveyor that transports 20-mm ammunition from the ammunition drum to the gun. The conveyor then returns the expended cases and unfired rounds to the ammunition drum. Although the physical location of components varies between different aircraft gun installations, the function and description of the components are essentially the same. M61A1 AUTOMATIC GUN LEARNING OBJECTIVE: Identify the components of the M61A1 automatic gun and recognize the operating principles. The primary parts of the gun are the barrels, housing assembly, and rotor assembly. The following paragraphs contain a description of each gun component and an explanation of how each component works. Figure 6-2 shows an exploded view of the gun components, and figure 6-3 shows the gun component locations. As each component is discussed, you should look at these figures. GUN COMPONENTS The primary parts of the gun are described in the following paragraphs. Muzzle clamp assembly. The muzzle clamp assembly is positioned at the outer end of the barrels. It restrains individual barrel movement during firing. It is positioned against the flange on the barrels and secured by the pressure of the self-locking nut assembly against the opposite side of the shoulders. Mid-barrel clamp assembly. The mid-barrel clamp assembly is positioned near the center of the barrels. The clamp tabs are engaged in the slots of the stop shoulders on the barrels. Secure the clamp in this position by rotating the locating disk to the locked position. The direction of rotation of the gun and barrel hue prevents the clamp from unlocking. Insert a cotter pin through the locking disk and clamp plate as an additional safety measure. Barrels. The M61A1 automatic gun has six rifled barrels. The stub rotor attached to the rotor body supports them. The three rows of interrupted locking lugs on the barrel engage similar interrupted locking lugs in the rotor to secure the barrel. There are three 6-1 Figure 6-1.—M61A1 automatic gun.