The Armored Gun System: Sheridan Replacement Offers Better Firepower Plus Worldwide Mobility

The United States Army has selected FMC Corporation’s Close Combat Vehicle Light, or CCVL, as the basis for the Army’s new Armored Gun System. The AGS will replace the M551A1 Sheridan Armored Reconnaissance/Airborne Assault Vehicle as the primary armored vehicle providing light contingency forces with an armored direct-fire kinetic energy antitank capability. The Close Combat Vehicle Light will be the basis for the AGS, but there will be changes in the system as testing and evaluation of the vehicle begin. Nevertheless, the basic outline of the AGS can be seen in the CCVL, and most of its capabilities will be similiar to, or better than, those of the existing vehicle. This article will contrast the Armored Gun System with the M551 Sheridan, the weapon system it replaces, examine the tactical roles it was designed to meet, and report on many of the characteristics of the new system. Role and Design Priorities The Sheridan is currently the only armored fighting vehicle that is strategically deployable with contingency forces, yet retains the fuepower and armor protection to engage in close combat with enemy armored vehicles. Officially designated the M551A1 Sheridan Armored Reconnaissance/ Airborne Assault Vehicle, it is a Vietnam-era design with numerous disadvantages; its light aluminum armor does not provide its crew with sufficient protection to defeat modern antitank weapons, and its 152-mm Shillelagh missile-fhg main gun has along time of flight and insufficient range. Taking advantage of newer technologies, the Armored Gun System will accomplish the missions the Sheridan has performed for nearly three decades more efficiently and with a greater degree of crew safety. The AGS, with its XM-35 105-mm main gun, is projected to have a range advantage of more than lo00 meters over the M551A1 Sheridan. Its compartmentalization of fuel and ammunition, and its improved armor technology, will increase crew survivability. In addition to superior mobility on the battlefield, it presents a smaller target than the Sheridan. Several design dilemmas have challenged designers of armored vehicles since Leonard0 da Vinci’s day. The difficulties of combining the right proportions of firepower and armor protection, while retaining battlefield mobility, are amplified in a strategically deployable armored gun system because of weight considerations. In addition to a weapons system capableof acceptable firepower and sufficient armor protection, the system must remain operationally and tactically mobile, packaged within predetermined gross weight limits to ensure strategic mobility. These realities demanded a very different set of design priorities for the Armored Gun System than those that led to the development of the M1 tank. The priorities used to design the AGS were, in order: Deployability: The AGS had to be airdeployable from tactical aircraft.. Lethality: The system had to be able to destroy main battle tanks at extended ranges.. Survivability: The minimum requirement was armor protection for the crew against artillery, small arms, and light antitank weapons. Sustainability: The AGS had to be able to fight for long periods of time with minimal external support. While these priorities differ substantially from those used in the design of the M1 tank, the AGS mission is also substantially different. The AGS is not intended to engage in close battle with enemy main battle tanks. Its survivability comes as much from its low 26 ARMOR - profile, agility, and quickness as from its armor protection. The AGS is designed to be used as part of a combined arms team, protected by infantry, smoke, and tenah features when engaged in combat with superior forces. As such, it meets the infantry’s pressing need for a direct fire kinetic energy tank-killing system, a capability the Sheridan cannot provide. The Competitors FMC’s Close Combat Vehicle Light was only one of four weapon systems the Army evaluated for the Armored Gun System. All of the vehicles were designed to cany the XM-35 105-mm main gun, an already-proven design, At left, the C C M prototype that will be the basis for the Army’s new Armored Gun System. Because it uses existing components - HEMTT engine, Bradley transmission, IAV 105 primary sight, Challenger 2 fire control computer, etc. -less time will be spent in development to be furnished to the winner by the While two of FMC’s competitors also used a traditional turreted design, the team of Gened Dynamics and Teledyne Continental Motors developed a weapon system without a turret: the 105-mm gun was mounted on a pedestal directly above the hull, with the three armored crewmen inside the hull. This design presents advantages in both crew survivability and the ability of the gun to engage targets from a hulldown position without being detected, because of the smaller area exposed to the enemy. However, on balance, the capabilities of the Close Combat Vehicle Light were chosen as those most necessary for the Armored Gun System. Army. The Armored Gun System While the Armored Gun System retains a conventional turret, it represents a major change in American armored vehicle design philosophy. The AGS will have a three-man crew, its loader replaced by an automatic loader with the ability to fire 12 rounds per minute from a 21-round magazine. The rest of the threeman crew sits in positions very similar to those occupied by the tank commander, gunner, and driver of the M1 tank. Much of the rest of the system will be built from components already in the NATO inventory, including a modified M977 HEMl’T engine, a Bradley transmission and Bradley power control handles, and the Challenger 2 fire control computer. Using components already in the inventory cuts costs, improves reliability, and allows the Armored Gun System to be put into production more quickly. The Turret Probably the most unusual feature of the AGS is its autoloader. In addition to the 21 rounds stored in the rotating magazine, each instantly accessible, nine additional rounds are stored in a compartment next to the driver. The vehicle can be uploaded by just two crewmen through a trap door in the rear of the turret. When around is pushed through the trap door into the feed my, the autoloader stores the round in the magazine. The gunner, entering information from a computer terminal at his station, tells the computer what kind of round it is. The autoloader then remembers where each ARMOR - 27

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A major change in the AGS is the elimination.of me crew member in favor of an automatic loader, seen at left. In sketch above, note compartment wall that separates and protects two turret crewmembers from autoloader mechanism. round is stored in the magazine and loads that type of round when the gunner requests it. All rounds in the magazine are immediately accessible; they rotate rapidly around the autoloader on a chain belt at the base of the loader. After firing, the gun returns to zero degrees elevation. The autoloader extracts the spent shell casing from the important safety feature is the compartmentalization of the crew from the autoloader, a firewall splits the turret neatly down the middle. While the gunner can access the breech of the gun through a trapdoor from his station, doing so turns the autoloader off. This prevents parts of the gunner from being loaded - known to be a problem with Soviet autoloaders. There is breech, then ejects it out of the turret through the same port used to load the autoloader. Once the autoloader has loaded the next round selected by the gunner, the gun retums to the elevation of the last target. The XM-35 main gun Will fire all 105-mm ammunition in the NATO inventory, including APFSDS, HEAT, HEP, WP, and APERS antipersonnel rounds. It will be able to traverse 360 degrees and elevate from +20 to -10 degrees. If the autoloader is disabled or inoperative, the crew can load the AGS at a rate of three rounds per minute. An also a hatch on the top left of the turret - about where the loader’s hatch is located on an M1- to provide additional access to the autoloader. There are, in fact, three hatches on top of the turret; for safety reasons, the gunner and tank commander will both have their own hatches. The Hughes primary sight, adapted from the LAV-105 now in service with the U. S. Marine Corps, will have both narrow and wide fields of view with magnification levels comparable to those of the M1 tank’s fire control system. Like the M60A3, the sight will provide both daylight and thermal channels, and the tank commander will have an extension so that he can view targets seen by the gunner. The laser rangefinder will be similar to the one in the M1. Secondary armament is also the same, with an M240 maxi-ally mounted 7.62-mm machine gun. The commander’s weapon station will be able to mount three different weapons: the M240, the M2 HB SO-caliber machine gun, and the Mark 19 automatic grenade launcher. The mix of secondary weapons mounted on the vehicle at agiven time will depend on the mission and expected enemy situation. Additional protection will be provided by 16 visual/IR smoke grenades and an NBC overpressure system, similar to the one in the MlA1. The Hull The Armored Gun System will be powered by a 580-horsepower Detroit Diesel engine with integral diagnostics and a built-in test system. This powerpack gives the AGS a higher horsepower-to-weight ratio than that enjoyed by the MlAl tank, and enjoys 92 percent commonality of repair prtrts with those for the M977 HEM’TT. Power will be applied to the tracks through the same transmission that has been combat-proven in the Bradley Fighting Vehicle. The AGS will 28 ARMOR - Jtdy-AugUSt 1992 h AGS autoloader magazine is replenished through a port in the turret, above. Gunner‘s computer keeps inventory. indexes proper rounds at gunner‘s command. At right, the powerpack is on a tray that slides out the rear, allowing quick and easy inspection and repair. have a govemor-limited top speed of 45 miles per hour and the ability to accelerate to 20 miles per hour from a standing start in six seconds. With its 150-gallon fuel capacity, the AGS is projected to have a 300-mile cruising range. Its low ground pressure of 8.7 pounds per square inch, coupled with its high horsepower/weight ratio, should give it unparalleled battlefield mobility. An important design feature is the ease of maintenance on the powerpack. Mounted on two tracks, the pack slides out for maintenance within five minutes, and can be run while it sits on the tracks at the rear of the vehicle. It can be reinstalled in another five minutes. Armor protection for the AGS crew is passive and modular. Additional modules can be added to the base vehicle to tailor protection to the scenario; the base vehicle weight of 37,300 pounds when fully combat loaded increases to 49,500 pounds with the addition of the maximum “Level 3” armor. The armor is not intended to defeat tank main gun rounds, but will use spaced armor and other advanced design concepts to maximize crew protection against small arms, indirect fire, and advanced antitank missile fire. In the lightweight “Level 1” configuration, the AGS can be deployed by low velocity air drop from a C-130 or roll-on/roll-off from the C-130. The AGS driver sits in the middle of the hull in a position similar to that occupied by the M1 driver. He will be seated in a reclining seat and use controls very similiar to those that control the M1. Conclusion ’ The Close Combat Vehicle Light is the prototype for the Armored Gun System; the Office of the TRADOC System Manager for the Armored Gun System emphasized that changes in the AGS will almost certainly be made during the move to full production status. A total of 300 vehicles is planned. Low-rate initial production of 69 vehicles is scheduled to begin in September 1994, and full rate production will follow with the remaining 23 1 vehicles. The Armored Gun System will provide the Army with a rapidly deployable vehicle with the firepower, armor protection, and battlefield mobility which U. S. liglit and contingency forces will need to fight and win on the battlefields of the 21st Century. Iraq’s invasion of Kuwait two yean ago proved that the end of the Cold War has not eliminated the threats to American national interests worldwide. With the addition of the Armored Gun System, the Army increases its ability to respond rapidly to the threats it may be forced to counter at any time, anywhere in the world. The soldiers of the U. S. Army Armored Force - and the security of the nation - deserve nothing less. The author would like to express his appreciation to FMC Coporation and Manager for the Armored Gun System for their assistance in preparing this article. the office of the TRADOC system Captain John A. Nag1 is a 1988 graduate of the U. S. Military Academy and received a Master‘s Degree in International Relations from Oxford University. A graduate of the AOBC, Airborne, Air Assault, and Tank Commander Certification Courses, he served as a tank platoon leader and tank company executive officer of N1- 32 Armor, 1st Cavalry Division. He is currently attending AOAC. 29