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LESSON 2 SHORT-RANGE AIR DEFENSE (SHORAD) GUN SYSTEMS
TASK
This lesson does not specifically relate to any enlisted or officer task but provides general information on the Duster, Vulcan, and SGT York Gun systems.
CONDITIONS
Use only the lesson material to complete the examination.
STANDARDS
You must attain a grade of 70 percent on the examination to receive credit for this subcourse.
REFERENCES
Lesson material.
Learning Event 1: THE DUSTER GUN
DUSTER
The M42A1 Duster is a self-propelled (SP), twin 40-mm antiaircraft gun designed to provide defense against very-low-to-low-altitude air attack.
System Description
The M42 or M42A1 (Figure 44) is a full-track-laying, armored, antiaircraft vehicle which can operate in temperatures ranging from -65 degrees to +120 degrees F. Major armament is a 40-mm dual automatic gun M2A1 mounted in the 40-mm twin-gun mount M4E1. This vehicle was designed for use with the maneuver forces against low-altitude air attack. Because of the rapid rates of fire, the gun has proved to be effective as a support weapon against ground targets. The interior of the vehicle is divided into three areas: driving compartment at the front, stowage compartment in the center, and engine compartment in the rear. The driving compartment contains the driving controls and instruments. The seats for the driver and commander-radio operator are in the driving compartment. The stowage compartment serves as a base for the gun mount and has stowage space for 12 boxes of 40-mm, ammunition. The engine compartment houses the main engine, auxiliary generator and engine, transmission, and fuel tanks. The gunner, squad leader, and cannoneer ride in the gun mount. The squad leader commands, via the intercommunications set AN/VIC-1, either from the commander's seat or the gun mount.
System Operation (Engagement Sequence)
The Duster engagement sequence (Figure 45) begins when the squad leader (1) designates the target, estimates target speed, direction of flight, and the angle of dive or climb, (2) and sets these values into the computing sight M38 (8). The gunner (3) engages the power drive mechanism and traverses the gun mount and elevates the dual 40-mm guns (4) until the target is centered in the reticle of the reflex sight M24C (5). The sight mechanically computes the lead angle (6) based on target speed and flight direction; super-elevation is automatically inserted based on gun elevation. When target tracking is steady, the gunner reports, "ON." Upon receiving the report, "ON," and having determined that the target is within range, the squad leader commands, "FIRE." The gunner commences firing and continues to fire until the target is destroyed or the squad leader commands, "CEASE FIRING." The normal mode of firing is that of POWER CONTROL, using the M38 computing sight. An alternate mode of operation is that of MANUAL. In this latter mode, the mount and dual gun are moved in azimuth and elevation by hand-operated cranks. When operated in the MANUAL mode, speed ring sights (8) are used for fire control.
System Characteristics
Duster system characteristics are found in Figure 46.
Learning Event 2: THE VULCAN GUN
VULCAN
Employment
The Vulcan gun system protects forward area combat elements and other critical assets from attack by threat aircraft operating at very-low-to-low altitudes. Vulcans also provide rear area command protection for air bases and other critical corps/theater level assets. Vulcans can also deliver effective ground fire against troops and lightly armored vehicles.
The Vulcan has two configurations. One is the self-propelled (SP), and the other is the towed. Both configurations use the same weapon system but have different carriers.
System Description
The SP Vulcan 20-mm M163A1 (Figure 47) is carried on a full- tracked, diesel-powered, lightly armored vehicle model M741. It mounts the weapon and provides space for the crew, auxiliary equipment, crew's personal gear, and about 1,031 rounds of ready-to-load ammunition. SP Vulcans are found in Chaparral/Vulcan battalions of armored, mechanized infantry, and infantry division.
The towed version of Vulcan is used in nondivisional Chaparral/Vulcan battalions and the Vulcan battalions organic to airborne and air assault divisions to counter the low-altitude air threat. It can also be used to engage ground targets. Since the towed Vulcan system uses the same 20-mm cannon, range only radar (ROR), and ammunition as the SP Vulcan, weapon characteristics are similar except that only 500 rounds of ready-to-fire ammunition are available on the weapon. Reload time is less than three minutes. Emplacement time is about two minutes.
The towed Vulcan gun system M167 (Figure 48) consists of a six-barrel, 20-mm cannon, and a fire control system mounted on a trailer carriage having dual wheels on each side. Vulcan system characteristics are shown in Figure 49.
Learning Event 3: THE SGT YORK GUN
SGT YORK
Purpose. The SGT York Gun (Figure 50) is a quick-reacting, all-weather, radar-directed gun system. It uses twin 40-mm cannons in an armored turret and is mounted on an M48A5 tank chassis. The SGT York Gun provides AD for the forward combat forces in the Army's heavy divisions, nondivisional brigades, and SHORAD units. The system uses the latest computer, laser, armament, and radar technologies. These and other advances in weapon system development have provided the Army an AD system with unique capabilities. The SGT York Gun, which will eventually replace the SP Vulcan gun system, is air transportable in C5A aircraft.
System Description
The SGT York Gun consists of twin L/70 40-mm automatic guns with a rate of fire of 300 rounds per minute per gun. The guns are interoperable with other L/70 guns and have a linkless feed system with upper and lower magazines for each gun with a capacity of 502 rounds. Three types of ammunition are available for the SGT York Gun: training target practice tracer (TPT), proximity fuze, and point detonating. The proximity fuze round has a delayed action high explosive charge. This is the primary round for aerial targets and is interoperable with NATO 1/70 guns. The point-detonating round is primarily for ground targets and is used in a self-defense role only.
The search/track radar for the SGT York Gun is a fully automatic, F-16 aircraft derived, pulse doppler with three beams providing full elevation coverage. The radar contains an integrated identification, friend or foe (IFF), system and ECCM provisions. SGT York Gun characteristics are shown in Figure 51.
Additional Features
Additional features of the SGT York Gun are--
o Automatic threat prioritization.
o Automatic selection of ammunition type and burst schedule.
o Automatic lead angle computation and meteorological inputs.
The fire control system has a manual override for all computer functions and provides a self-defense direct/indirect fire capability against ground targets. The combat display within the SGT York Gun is comprehensive. Targets (friend or foe) are displayed with a prioritization symbology for threat targets. Primary target line, search sector limits, and range rings are displayed, as well as the hull heading, gun orientation, gunsight line of sight, periscope line of sight, ammunition status, acquisition mode, and system status. The SGT York Gun's integrated laser range finder gun-sight has a stabilized day/night sight with a 5 °-day/ 3° -night field of view. There is a squad leader's periscope, independent of the gunsight, which has a 360° under armor, stabilized day/night search, and a 20° -day/12°-night field of view. The crew compartment in the SGT York Gun's turret is environmentally controlled.
The SGT York Gun is capable of performing all target acquisition, tracking, and engagement functions while moving cross-country. This makes it an excellent weapon for providing AD for maneuvering forces.
