The M163 VADS uses the M168 gun, a variant of the General Dynamics 20 mm (0.79 in) M61A1rotary cannon, the standard cannon in most U.S. combat aircraft since the 1960s. The gun is mounted on a modified M113A1 vehicle (the M741 carrier). Designed to complement the M48 Chaparral missile system, it is limited to fair-weather operations.[3] The M163 uses a small range-only AN/VPS-2 radar and an M61 optical lead-calculating sight, and is incapable of using the radar to scan an area for targets. The system is suitable for night operations with the use of AN/PVS series night vision sights that can be mounted to the right side of the primary sight.
The gun fires at 3,000 rounds per minute in short bursts of 10, 30, 60, or 100 rounds, or it can fire in continuous fire mode at a rate of 1,000 rounds per minute.[4] A linkless feed system is used. Its 20x102mm round gave it a low effective range of only 1,200 meters (3,900 ft), and its standard air-defense load of HEI-T rounds would self-destruct at approximately 1,800 meters (5,900 ft), a hard limit on range. The feed drum holds 1,200 rounds ready to fire, with 800 rounds stowed in reserve for the M163, later increased to 1,030 rounds stowed in reserve for the M163A1 and A2.
Service history
In US and Israeli service, the VADS has rarely been needed in its intended purpose of providing defense against aerial threats—consequently, the Vulcan gun system was in use throughout the late 1980s and early 1990s primarily as a ground support weapon. For example, VADS guns were used to support American ground assault troops in Panama in 1989 during Operation Just Cause. One Vulcan of B Battery, 2/62 ADA sank a PDF patrol boat.[5] The last combat action the VADS participated in US service was Operation Desert Storm.
In order to provide effective battlefield air defense against helicopters equipped with anti-tank missiles that could be fired accurately from ranges of several kilometers, the VADS was slated to be replaced by the M247 Sergeant York DIVADS (Divisional Air Defense System), but that system was canceled due to cost overruns, technical problems, and generally poor performance.[8]
In 1984 the improved PIVADS (Product-Improved VADS) system was introduced, providing improvements in the ease of use and accuracy of fire, but the limitations of the 20x102 mm caliber remained. In 1988, the fourth crewmember (observer/loader) was issued a Stinger launcher and two rounds.[9]
Eventually, the M163 was replaced in US service by the M1097 Avenger and the M6 Linebacker, an M2 Bradley with FIM-92 Stinger missiles instead of the standard TOWanti-tank guided missiles: the Stinger missile providing the necessary range to deal with helicopters with anti-tank missiles far out-ranging the 20 mm gun, as well as considerably extending the reach against fixed-wing targets. The final US Army VADS-equipped unit at Fort Riley Kansas completed turn-in of its Vulcans in 1994.
Ammunition
While a large number of 20x102mm rounds have been developed, not all were issued to M163 units. M246 HEI-T-SD was developed alongside the system and was the primary anti-air round, with M56 HEI being used for ground support.[10] PIVADS units could use Mk 149 APDS rounds, which greatly increase maximum effective range due to their higher velocity and lack of a self-destruct. M940 may have been issued for use prior to withdrawal from service, though sources are unclear.
Designation
Type
Projectile Weight (g)
Bursting charge (g)
Muzzle Velocity (m/s)
Description
M56A3/A4
HEI
102
10.7 g HE (H761, a mixture of RDX/wax/Al) and 1.3 g incendiary (I136)
1,030
Nose fuzed round, no tracer. M56A3 has the explosive filler and the incendiary mixed in one pellet, while the M56A4 has the explosive filler inserted in a separate pellet after the incendiary pellet. Effective range of 4,500 m (14,800 ft) against ground targets.[11]
M246/A1
HEI-T-SD
102
7.5 g HE (H761)
1,030
M56 series derived tracer round, with the M246 using M56A3's loading method and M246A1 using the M56A4's loading method. Tracer burnout triggers the self-destruct after 3–7 seconds of flight time, roughly 1,800 meters (5,900 ft).[12] Effective range of 1,200 m (3,900 ft) against air targets, maximum range of 1,800 m (5,900 ft) against ground targets.
M940
MPT-SD
105
4 g HE (A-4) and 3 g incendiary (I136) with 1.2 g incendiary (I68) nose initiator
1,050
Multi-purpose fuzeless round for ground-based air defence, naval and helicopter applications. The HE charge is initiated by the incendiary charge on the nose on impact. Self-destruct due to tracer burn-through. Penetration: 12.5 mm (0.49 in) RHA at 0-degree impact at 518 m (1,700 ft) range, 6.3 mm (0.25 in) at 60 degrees and 940 m (3,080 ft). Effective range of 2,000 m (6,600 ft) against air targets.[13]
Mk 149
APDS
projectile: 93 penetrator: 70
none
1,120
Spin-stabilized finless sub-caliber round with a 12 mm (0.47 in) depleted uranium penetrator. Penetration: 23 mm (0.91 in) armor at 45 degrees at 1,000 m (3,300 ft) and 19 mm (0.75 in) at 45 degrees at 2,000 m (6,600 ft)[14] Effective range of 2,500 m (8,200 ft) against air targets.
An M163 during the Persian Gulf War's Operation Desert Shield.An M163 Vulcan anti-aircraft gun system vehicle returns to the vehicle staging area after an exercise at the National Training Center in Fort Irwin, California.A close-up of the 20 mm Vulcan cannon on the M163 VADS.
M163
AVADS Automatic track VADS prototype demonstrated by General Electric for the Gun Air Defense Effectiveness Study in 1974.[17] This prototype used a new lead-generating fire control computer paired with a helmet mounted sight. Not adopted.
M163A1 incorporated modifications to improve the reliability, availability, and maintainability (RAM). Type reclassified from M163E1 Improved VADS in September 1976. Newly manufactured M163A1s in 1982 used the improved M741A1 carrier, and the M741s in service were converted to M741A1 through 1985.
M163A2 PIVADS (1984) accuracy and workload improvements developed by Lockheed Electronics Company including a digital microprocessor, director sight and low backlash azimuth drive system. The PIVADS also used the M741A1 carrier vehicle.
M167 towed counterpart utilizing the Gama Goat as the prime mover. After 1989 the Humvee became the prime mover.
Machbet Israeli upgraded version equipped with 4-tube FIM-92 Stinger pod, upgraded tracking system and the ability to share information with local high-power radar.
Operators
Map with M163 operators in blue with former operators in red
Portugal – 36 ex-US M163 Vulcan VADS SPAAG ordered in 1986, but never used. Probably purchased to supply parts for the M113A2.[21]
Israel — following the closing of tactical Anti-Air units in the IDF, both the VADS and the upgraded VADS ('hovet', fitted with stingers) were retired in 2006. In 2024 evaluation started for reuse of old VADS units against drone threats.[22]
