The High Survivability Test Vehicle (Lightweight) (HSTV(L)) was a

U.S. Army The United States Army (USA) is the primary land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of the United Stat ...

light tank A light tank is a Tank classification, tank variant initially designed for rapid movements in and out of combat, to outmaneuver heavier tanks. It is smaller with thinner vehicle armour, armor and a less powerful tank gun, main gun, tailored for ...

manufactured by

AAI Corporation AAI Corporation is an aerospace and defense development and manufacturing firm, located in Hunt Valley, Maryland, US. Formerly a wholly owned subsidiary of United Industrial Corporation, AAI was acquired by Textron in 2007. It currently opera ...

. It was developed under the

Tank-automotive and Armaments Command The United States Army Tank-automotive and Armaments Command (TACOM), and its subordinate Life Cycle Management Command (LCMC),

(TACOM) Armored Combat Vehicle Technology (ACVT) program.

History

In early 1977 the Army selected proposals from AAI and

Pacific Car and Foundry The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is bounded by the continen ...

for HSTV(L) concept feasibility analysis. In December 1977, the Army awarded the HSTV(L) fabrication contract to AAI. One reported early challenge was meeting the HSTV(L)'s weight target. As of September 1981, no significant problems were reported with the HSTV(L).

Martin Marietta The Martin Marietta Corporation was an American company founded in 1961 through the merger of Glenn L. Martin Company and American-Marietta Corporation. In 1995, it merged with Lockheed Corporation to form Lockheed Martin. History Martin Marie ...

expressed interest in a joint venture with the AAI Corporation to enter a version of the HSTV-L into the U.S. Army's

Armored Gun System The Armored Gun System (AGS) was a U.S. Army competition in the 1990s to design a light tank to replace the M551 Sheridan and TOW-equipped HMMWVs. It was the ultimate incarnation of several research programs run in the 1970s with the aim of provi ...

competition. The corporation apparently decided that the technology was not sufficiently advanced to proceed with radical changes in the HSTV-L to meet the new AGS requirements, therefore, they did not bid on the program.

Design

Mobility

The AAI HSTV(L) is powered by a Avco Lycomming 650hp gas turbine (derived from the

LTS101 The Lycoming (now Honeywell) LTS101 is a turboshaft engine family ranging from 650 to 850 shaft horsepower, used in a number of popular helicopters, and, as the LTP101 turboprop, light aircraft. Both models carry the US military designation T702 ...

). It is connected to an automatic 4-speed X-300 transmission made by Detroit Diesel Allison, the turbine being placed behind the transmission. It used a fixed height hydro-pneumatic suspension system and tracks modified from those used on the

M551 Sheridan The M551 "Sheridan" AR/AAV (Reconnaissance vehicle, Armored Reconnaissance/Airborne Assault Vehicle) was a light tank developed by the United States and named after General (United States), General Philip Sheridan, of American Civil War fame. It ...

. The Pacific Car and Foundry HSTV(L) is powered by a General Motors 8V71T diesel engine connected to a General Electric HMPT-500 transmission.

Armament

The main armament consisted of an

Ares Incorporated Ares Incorporated is an American weapons manufacturer and firearms engineering company co-founded by the American weapons inventor and developer Eugene Stoner in 1971. The company is based in Port Clinton, Ohio, and produces fire control systems ...

XM274 The Ares Incorporated XM274 (originally designated as the medium caliber, antiarmor automatic cannon, MC-AAAC) was an American smoothbore 75mm autocannon designed by Eugene Stoner. It used a rotating breech block with cased telescopic ammunitio ...

75 mm CTA

autocannon An autocannon, automatic cannon or machine cannon is a automatic firearm, fully automatic gun that is capable of rapid-firing large-caliber ( or more) armour-piercing, explosive or incendiary ammunition, incendiary shell (projectile), shells, ...

with 2-axis stabilization capable of firing

Armour-piercing fin-stabilized discarding sabot Armour-piercing fin-stabilized discarding sabot (APFSDS), long dart penetrator, or simply dart ammunition is a type of kinetic energy penetrator ammunition used to attack modern vehicle armour. As an armament for main battle tanks, it succeeds a ...

and

high-explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An exp ...

. Secondary armament consisted of a

coaxial In geometry, coaxial means that several three-dimensional linear or planar forms share a common axis. The two-dimensional analog is ''concentric''. Common examples: A coaxial cable has a wire conductor in the centre (D), a circumferential ou ...

7.62 mm

M240 machine gun The M240 machine gun, officially the Machine Gun, 7.62 mm, M240, is the U.S. military designation for the FN MAG, a family of Belt (firearms), belt-fed, gas-operated reloading, gas-operated medium machine guns that chamber the 7.62×51mm NA ...

and a commander's M240. AAI had originally planned to place a .50 caliber (12.7 mm)

heavy machine gun A heavy machine gun (HMG) is significantly larger than light, medium or general-purpose machine guns. HMGs are typically too heavy to be man-portable (carried by one person) and require mounting onto a weapons platform to be operably stable or ...

at the commander's hatch. Pacific Car's proposal mounted the Ares 75 mm gun in an external elevating

trunnion A trunnion () is a cylinder, cylindrical Boss (engineering), protrusion used as a mounting or pivoting point. First associated with cannons, they are an important military development. In mechanical engineering (see the Trunnion#Trunnion bearin ...

mount alongside a

25 mm

M242 Bushmaster The M242 Bushmaster chain gun is a 25 mm caliber, 25 mm (25×137mm) single-barrel chain-driven autocannon. It is used extensively by the United States Armed Forces, U.S. military, such as in the Bradley fighting vehicle, as well as by other NAT ...

autocannon. Twenty-two 75 mm ready rounds (11 APFSDS and 11 HE respectively) could be carried in a magazine and thirty-three more could be carried in hull storage. A 40 mm grenade launcher was originally included, but removed during a review of the proposal. The AAI proposal called for sixty 75 mm rounds. As built, the test vehicle had only 26 rounds, but provisions existed for the original 60 rounds in the turret. The projectiles were stored vertically in a magazine beneath the right side of the turret and fed vertically into the rotating breech, with the shell casing being ejected vertically upwards. Unlike the Pacific Car and Foundry proposal all rounds were accessible to the autoloader and there was no secondary ammunition storage.

Armor

The armor thickness and layout are unknown; however it most likely used an aluminum alloy similar to the M2 Bradley and M113.

Crew

The AAI HSTV(L) had an unconventional crew layout, with the commander located in the turret, and the driver and gunner being located in the hull. The commander had access to a 2-axis stabilized hunter sight produced by

Texas Instruments Texas Instruments Incorporated (TI) is an American multinational semiconductor company headquartered in Dallas, Texas. It is one of the top 10 semiconductor companies worldwide based on sales volume. The company's focus is on developing analog ...

that was independent of the turret and allowed him to freely locate targets, and then slave the turret to his sight. The gunner would then engage the target while the commander looked for the next target. Both the gunner's sight and commander's hunter-killer sight were 2-axis stabilized, had both direct vision and

FLIR Forward-looking infrared (FLIR) cameras, typically used on military and civilian aircraft, use a thermographic camera that senses infrared radiation. The sensors installed in forward-looking infrared cameras, as well as those of other thermal ...

optics, and with the gunner's sight having access to a CO2 eye safe laser rangefinder made by

Raytheon Raytheon is a business unit of RTX Corporation and is a major U.S. defense contractor and industrial corporation with manufacturing concentrations in weapons and military and commercial electronics. Founded in 1922, it merged in 2020 with Unite ...

. Any crewmember could use the armament as both the hunter-killer sight and gunner's primary sight were available through a tv screen mounted at each crew station, but only the gunner and driver could drive. there was also a fixed rear view tv camera to help with reversing. HSTV-L Armor and Cavalry Collection

For the Pacific Car HSTV(L) the crew layout was more conventional, having the commander and gunner located in the turret in the turret basket below the external gun system.

References

Sources

* {{cite book , last1=Hunnicutt , first1=Richard Pearce , author1-link= R. P. Hunnicutt , title=Sheridan: A History of the American Light Tank , volume=2 , date=2015 , orig-date=1995 , publisher=Echo Point Books & Media , location=Battleboro, VT , isbn=978-1-62654-154-2 Light tanks of the United States Trial and research tanks of the United States Cold War tanks of the United States Light tanks of the Cold War