M163 / M167 VADS Vulcan Air Defense System
The Romans worshipped Vulcan — the Greeks, Hephaestus — both gods of fire. The Vulcan Air Defense System (VADS) was designated and fielded in two versions: the self-propelled (M163) and the towed (M167). These systems were deployed world wide, with the M167 towed Vulcan primarily in airborne or airmobile divisions. The M167 VADS Vulcan Air Defense System, which has been withdrawn from service, was a short-range air defense gun intended to protect forward area combat elements and rear area critical assets. It also protected against lightly armored ground targets. The M167A2 VADS was a modified M167A1 VADS with an improved fire control subsystem. The improvement was obtained by replacing the disturbed reticle sight with a director reticle sight, the sight current generator with a digital processor, and the azimuth drive assembly with a harmonic drive.
The Arab-Israeli war of 1967 drove home the point that units needed air coverage in support of maneuver. With a surprise attack on both airfields and SAM sites, the Israeli Air Force insured not only air superiority but air supremacy over Arab ground forces thus causing the Egyptians to sue for peace. Over North Vietnam, US aircraft were on the receiving end and saw massive ADA coverages emerge around Hanoi and Haiphong composed of both SAMs and AAA. One outgrowth of the lessons learned by the US Air Force was that US divisions needed an organic air defense unit. As an interim measure until an objective system could be fielded, the Army developed the Chaparral SAM system and the Vulcan 20mm gun. These were then introduced as a battalion size element in the division in the early 1970s.
In June 1946, the US government awarded General Electric a contract for a rapid-fire cannon that became known as the Vulcan. The company delivered a .60-caliber version in 1950, and two years later, a more advanced model appeared in three calibers: .60 mm, 20 mm, and 27 mm. The Air Force and Army adopted the 20 mm as the M61 Vulcan. The Army began development of its version in 1964 and mounted the M61 on an M113 armored personnel carrier as a daytime, clear-weather, air-defense.
VULCAN was fielded in 1967 as an interim short range air defense system. According to the Army, the VULCAN system had very limited effectiveness. For VULCAN to be effective, the target must be hovering or flying a non-maneuvering course toward the gun and be within a range of 1,000 meters. VULCAN provided only a low degree of suppression against maneuvering threats.
When compared with other nations' ADA gun systems, Vulcan was ranked near the bottom in anti-aircraft effectiveness. The system had an 1100 round drum for ammunition and capacity to carry another 1000 rounds. Reload time was approximately five minutes. The Vulcan was developed as an interim system with off-the-shelf parts and deployed until an objective system was deployed. The effective range of the system was 1200 meters, and the system was usually never deployed in less than a platoon, though a pair could be tasked out in specific instances. The mutual supporting distance between systems was 1000 meters. VADS had limited ability to fire on the move, and was best employed when stationary and the stabilization system enabled. It had no acquisition radar but mounted a Range-Only-Radar for calculating firing lead angle and elevation compensations for attacking aircraft. The system was mounted on the M113 Armored Personnel Carrier, which lacked the mobility to stay with the M1 Abrams tank and M2 Bradley fighting vehicle. The gunner had minimal protection from small arms fire and was exposed to any overhead artillery bursts.
The heavy division's ADA battalion of the 1980s had a total of 36 M163 self-propelled Vulcan Air Defense Systems (VADS), 60 Stinger Manportable Air Defense Systems (MANPADS) teams and six Forward Area Alerting Radar (FAAR) systems. Originally it had 24 Chaparral SAMs with the highly effective Sidewinder and 24 VADs and eight FAARs. The battalion was broken down into an Headquarters and Headquarters Battery (HHB) with a 15 team Stinger platoon and three each Gun/Stinger batteries of 12 VADS and 15 Stinger teams.
The M163 chassis is intended primarily for operation over all types of terrain at speeds up to k2 mph and ranges to 300 miles. It has an amphibious speed capability to 3.6 mph. Movement of the tracks propels and steers the vehicle on both land and water. The water-tight hull is welded aluminum plate. The power train components are located in the forward right section of the vehicle. A General Motors 6-V53 diesel engine supplies power through a transfer case to an Allison three-speed automatic transmission. The vehicle is equipped with a suspension lock-out system that is used when firing from a stationary position. The system is air-transportable and weighs approximately 26,000 pounds when combat-loaded with ammunition and a crew of four.
The M61A1 Vulcan cannon is a six-barrel 20mm weapon capable of firing 6,000 rounds per minute. Incorporating the same basic principle invented by Richard J. Gatling in the 1860s, the M61A1 multiple gun barrels rotate rapidly to allow a high rate of fire. Because each barrel fires only one of every six rounds, the wear and heat generated are less than with a single barrel gun. Vulcans can be driven electrically, hydraulically or by a ram-air engine.
The XM168 gun is a six-barrel Gatling type automatic weapon. It is electrically operated and fired, with power supplied by batteries charged by either the vehicle or an auxiliary power unit. Rate of fire depends upon the speed of barrel cluster rotation, with a high and low rate of 3,000 and 1,000 rounds per minute, respectively. Burst length may be pre-selected by the gunner on the high rate of fire only for controlled bursts of 10, 30, 60, and 100 rounds. The system employs M56A3 20mm high explosive incendiary ammunition and XM220 target practice tracer in a 7:1 mix, respectively. XM206 self-destruct ammunition was also available.
The XM157 gun mount is a one-man operated, power driven, servo-controlled turret of new design. The turret has unlimited travel in azimuth at speeds up to 75° per second. The gun has an elevation range of -5° to +80° at speeds up to 5° per second. The armament system may be operated without interfering with the maneuverability of the vehicle. The system carries 2,000 rounds of ammunition; 1,000 rounds are available for firing without reloading. Approximately 200 rounds remain in the feed system during the reloading of the 800-round reserve.
The AN/VPS-2 ROR [Range-Only Radar] is an integral part of the VULCAN system and is used in the air defense role. Early warning of enemy air activity would be normally received by the fire units in the same manner as other ADA AW units. The Rapid Alerting Identification Display Data Link would provide adequate intelligence for these units.
In the years between World War II and Vietnam, AAA was used primarily in a ground support role. Places like Pork Chop Hill and Heartbreak Ridge saw AAA supporting convoy movements and maneuver elements by providing overwatching direct fires. The same was basically true in Vietnam when the M42 Duster and the Quad .50 (Whispering Death) AAA units were used to defend fire bases and convoys.
The Army Concept Team in Vietnam evaluated the XM163 VULCAN Air Defense System to determine its effectiveness in a combat role. The l80 day Department of the Army evaluation began on 26 November 1968. Because of the tactical situation the VULCANs were retained in RVN for an additional period. The evaluation terminated on 20 April 1969. The evaluation was oriented toward a ground role, and the air defense role should targets of opportunity appear. There was no enemy air activity during the evaluation.
The VULCAN was designed primarily as an air defense weapon. Thus there were some inherent problems in the transition from a ground support configuration to one of air defense. If the VULCAN system were operating with all its air defense equipment on board, then the problem of transition from the ground support to the air defense would be minimal. If the VULCAN were operating without a portion of its air defense equipment, such as the ROR, as was common in RVN, then the transition would be lengthier. The transition time would depend upon the proximity of the VULCANs to the storage location of the other related equipment, the availability of transportation, and the availability of personnel to perform the retrofit.
The combat effectiveness of the VULCAN was superior to the Duster and the Quad 50. It exceeded both these vehicles in all categories except ammunition resupply. The VULCAN was more compatible with the cavalry and mechanized vehicles with which it usually operated than were the Duster or Quad 50. Its high cyclic rate of fire ensured a high degree of lethality. The relatively small basic load of the VULCAN, together with its high cyclic rate of fire, posed a constant ammunition resupply problem.
The VULCANs were employed in a variety of missions similar to those supported by the Duster batteries - usually with cavalry or mechanized infantry units. They were not committed in less than a section (two weapons) size element. The VULCANs operated with the Armored Cavalry Assault Vehicle (ACAV). The ACAV and the VULCAN were highly compatible, having identical chassis, similar signature characteristics,and generally the same mobility and maintenance requirements. Both were used in roles approaching those of an armored reconnaissance vehicle or light tank.
Specific data on the relative effectiveness of the VULCAN/Duster/Quad 50 against various targets was not available because of the wide variation in characteristics of these targets and the combat environment. Weapons effects data could be obtained under controlled test conditions in CONUS. There was a general feeling among all personnel involved in the evaluation that the VULCAN was more effective than the Duster or Quad 50 against all types of targets encountered in RVN.
The cyclic rate of high explosive fire of the VULCAN was unsurpassed by any ground combat weapon in RVN. Field comments indicated a belief that the VULCAN could destroy any target within its range. Firing was usually executed in 10- and 30-round bursts. Field observations revealed this method was the most effective, providing the best target coverage with the least dispersion. This method aided conservation of ammunition because the gunner knew exactly how many rounds were being expended.
Supported troops were highly complimentary of the VULCAN system. They were particularly impressed by its increased mobility, flat trajectory of its projectile, and firepower. They would have welcomed the immediate deployment of additional VULCANs in support of their operations in RVN.
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