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CCL X1A1 Carcará
In 1973, the X1 tank was introduced as an upgrade to the M3 Stuart, initiated by the Parque Regional de Motomecanização da 2a Região Militar (PqRMM/2), alongside Brazilian companies Bernardini and Biselli. Supervised by the Diretoria de Pesquisa e Ensino Técnico (DPET), responsible for coordinating military projects, the X1 aimed to modernize existing tanks due to limited access to new materials during the Vietnam War.
The project, led by the Centro de Pesquisa e Desenvolvimento de Blindados (CPDB), focused on developing a new family of light tanks based on the M3 Stuart. The choice was influenced by its abundance, cost-effectiveness, and suitability for Brazil’s terrain. Moreover, it provided valuable experience for eventually building a domestically produced tank.
Despite initial success, flaws in the X1 design prompted the development of the X1A1, a lengthened variant with improved components. Delays led to a final delivery of the pre-series of 17 X1A1 vehicles in 1976.
Development
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The development of the X1A1 began sometime between 1975 and September 1976, following extensive testing of the original X1 in 1974 and its public debut in 1976. The main goal was to address issues identified in the X1 design, particularly regarding its suspension and transmission.
One major change involved replacing the oversized idler wheel from the 18-ton M4 Artillery Tractor suspension, which caused premature wear due to the X1’s higher speed. To remedy this, the idler was swapped with one from the M4 Sherman, necessitating the addition of an extra bogie on each side of the vehicle.
This modification required lengthening the hull by approximately 0.8 meters to accommodate the redesigned suspension and maintain adequate track length. The extended hull also allowed for increased fuel and ammunition storage, with the capacity expanding from 10 to 34 90 mm rounds.
The larger hull size also facilitated the installation of a larger turret bustle for the BT-90A1 turret, enhancing storage capacity and allowing for the addition of an extra radio. These alterations resulted in an overall increase in weight, necessitating the installation of larger brakes.
The X1A1 was completed before the Independence Day Parade of September 7th, 1976, earning the nickname “Carcará” after an indigenous crested bird. Its official designation was Viatura Blindada de Combate – Carro de Combate MB-1A (VBC-CC MB-1A), with MB referring to Medio Bernardini (Medium Bernardini). It likely retained the same vehicle number, EB11-376, previously assigned to an M3A1 Stuart owned by the CPDB.
Hull and Armor
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- The X1A1 utilized a lengthened and modified M3A1 Stuart hull, identifiable by its curved rear plate.
- Overall, the X1A1’s hull offered similar protection to the M3 Stuart.
- Specific armor thickness included 38 mm at 17º vertical for the upper front plate, 16 mm at 69º for the middle front plate, and 44 mm at 23º for the lower front plate.
- Transitioning frontal cheek plates to side plates were 28 mm thick.
- Side plates were 25 mm thick and angled at 10 degrees, while the engine bay sides had two spaced 25 mm plates.
- The rear armor remained consistent with the M3 Stuart at 25 mm.
- The top plate was 15 mm thick, and the floor plate thickness decreased from 13 mm at the front to 10 mm at the rear.
- The X1A1 featured a familiar layout similar to the Stuart, including headlights, towing hooks, and a .30 caliber hull machine gun.
- The driver’s hatch was two-piece, while the co-driver’s was single-piece.
Mobility
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- Engine: The X1A1 was equipped with a Scania-Vabis DS-11 A05 CC1 6-cylinder in-line 256 hp diesel engine.
- Drive Components: Unlike the X1, the X1A1 utilized more drive components from the 18-ton M4, including its 3-speed transmission.
- Steering Mechanism: Notably, the X1A1 featured steering levers mounted on the top of the hull instead of the bottom.
- Speed and Range: It boasted a top speed of potentially 50 to 55 km/h (31 to 34 mph) on roads and an operational range of 520 km (323 miles).
- Suspension: The X1A1 adopted a modified VVS suspension system from the 18-ton M4 artillery tractor, featuring 6 road wheels divided over three bogies per track, along with 3 return rollers on each side.
- Ground Pressure and Mobility: With a ground pressure of 0.55 kg/cm2 (7.8 psi), the X1A1 had an on-ground track length of about 3.66 meters (12 foot) and could traverse a trench of 6.1 meters (4.9 foot).
Turret
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- Turret Design: The X1A1’s turret closely resembled the X1’s BT-90A1 turret, with the addition of an extended turret bustle.
- Armor: Armored with 28 mm thick steel plates at various angles to withstand .50 caliber machine gun fire at 200 m, while the turret top and gun shield were protected by 15 mm plates.
- Influence: The turret layout and internal components were likely inspired by the French H-90 turret, with similarities in shape and construction.
- Armament: Featured a mount for a .50 caliber machine gun on the left side in front of the commander’s cupola.
- Commander’s Cupola: Positioned slightly raised from the turret top to offer a 360º view, with the radio set antenna located behind the gunner’s cupola.
- Placement Differences: Spare tracks were mounted on the turret bustle sides for additional armor, while smoke dischargers were relocated to the front of the turret, with three dischargers on each side. Additionally, a small light was installed on the turret side of the commander’s cupola.
Armament
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- Main Armament: Equipped with the 90 mm D-921 low-pressure gun, allowing for significant armor penetration capabilities on light platforms like the X1A1 and the AML-90.
- Ammunition Types: Accessible ammunition included HEAT (High Explosive Anti Tank), HESH (High Explosive Squash Head), and High Explosive (HE) rounds. HEAT rounds were utilized for anti-armor purposes, while HESH rounds were for bunkers, walls, and light vehicles. HE rounds served as general-purpose support ammunition.
- Limitations: Due to the low-pressure nature of the gun, AP (Armor-Piercing) rounds were not available. These guns had limited combat range and decreased velocity compared to high-velocity guns, resulting in decreased accuracy at longer ranges.
- Ammunition Stowage: The turret stored 24 rounds, with an additional 34 rounds stored in the hull, totaling 58 rounds of 90 mm ammunition.
- Secondary Armament: Supplementary armament included a turret-mounted .50 caliber machine gun for the commander, a coaxial .30 machine gun, and a .30 machine gun for the co-driver in the hull.
Pictures
Source
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CCL X1A1 Carcará - Tank Encyclopedia
Brazilian Stuart – M3, M3A1, X1, X1A2 and their Derivatives – Hélio Higuchi, Paulo Roberto Bastos Jr., Reginaldo Bacchi
Army Guide
Blindados no Brasil – Expedito Carlos Stephani Bastos
