EE-T1 Osório's Historical Background

HISTORICAL BACKGROUND AND CONTEXT:

In the 1970-1980's, the Brazilian company Engenheiros Especializados S.A (known famously as ENGESA), was a world famous company for the manufacturing civilian vehicles, electronics, farming equipments and their infamous military vehicles such as the successful EE-9 Cascavel reconnaissance vehicles and the EE-11 Urutu APC being the company's primary market product, as well the slightly less successful EE-3 Jararaca scout car. At the same time period, the Brazilian Army made a requirement for a new tank to replace its fleet of M41 Walker Bulldogs acquired from the United States around the 1960's. The new vehicle required a cannon at minimum of 90mm and 105mm and weighing less than 30 tonnes, at that time period, Bernardini and ENGESA made an agreement which Bernardini was going to focus on vehicles meant for Brazil while ENGESA focused on the export market. However, around the early 1980's, Saudi Arabia made a new procurement for a new MBT meant to replace their aging AMX-30 MBTs. Initially, Saudi Arabia wanted to acquire Leopard 2 tanks from Germany, but due to extrict german export laws at that time, which prohibited non-NATO countries to acquire german military equipment.

EE-T1 OSÓRIO P1:

ENGESA seeing the opportunity to make a multi-billionaire contract with the Saudis, started the development of their very first MBT in 1981 with the support of the brazilian armed forces and the current government at that time, and with the help of Vickers-Armstrong for the turret and other foreign companies for the turret components, including Belgium, German, British and French companies to make the vehicle. The first prototype was finished in 1985, just in time for the vehicle to be sent for early trials in Saudi Arabia while the 2nd prototype (P2) was being built. The turret of the tank was armed with a 105mm L7 Royal Ordnance tank gun, with 45 rounds in the vehicle, with 12 in the turret and 33 in the hull, the gunner and commander sights were the belgian made OIP LRS-5 (day-night) gun sights with ND:YAG laser rangefinder, with a integrated computer, and the commander's periscope was a OIP SCS-5 8x day-night sights (the same systems which were later used on the EE-18 Sucuri prototype), allowed the vehicle to have night fighting capability, the sights and the cannon were electric-stabilized, which furthermore improved the fire on the move capability, the turrets rotation was documented to be able to traverse the turret at 33.75°/s and a elevation speed of 11.25°/s.

Early EE-T1 P1 about to do night fighting testing in 1985.

P1’s internal turret modules drawing.

EE-T1 OSÓRIO P2:

For the second 120mm tank (P2), the fire control system utilized the Centaur AFCS (Marconi, UK). This version included a VS58010 Vicas system integrated into the periscope sight. To facilitate shooting during nighttime or low visibility conditions, the USFA UA9090 thermal imaging allowed seven times magnification, developed by the Dutch company Philips. Additionally, there was the option to install another thermal imaging system of French production. A desktop for operating thermal imaging equipment was located at the gunner’s position. The thermal image was also stabilized and displayed on monitors positioned for the gunner and commander. The commander had an independent panoramic view marked with the VS58019 symbol. This enabled them to aim and fire the cannon at any time of day independently of the gunner. The VS580’s field of view of 16 degrees equated to a 3x enlargement, while the 5-degree field of view was 10x. According to the VS580 information, the gunner had only a 10x enlargement. In the case of a tank like the P2, it indicated key features in the laser locator based on the YAG rod. The laser wavelength was the same as that used in the P1 rangefinder. Distance measurement could be made in the range of 400-10,000 m with an accuracy of 7m. The laser rangefinder could also be equipped with the commander’s sight, and the stabilization of visual fields from both positions could be activated independently of the cannon stabilization. Information about the relative position of the cannon and mirror was obtained by comparing the mirror and cannon angle positions. Regarding the Centauro system settings for firing, it listed a 16-bit processor converter. Both models featured a backup protection mechanism designed in case of a fire control system failure, located at position L35 (sometimes referred to as L30), providing 10x magnification.

EE-T1 P2 firing its machine gun in a day live fire testing in Brazil.

An excellent drawing of the P2’s internal modules, including the hull’s engine and transmission.

ENGINE AND TRANSMISSION:

Both versions of the Osório tank were powered by the turbo diesel engine MWM 834, also referred to in some sources as MWM TBD 234. This 12-cylinder power unit with direct fuel injection was manufactured by the German company Motoren-Werke Mannheim AG. The cylinder block had a 60-degree spread angle, producing a maximum power of 765 kW (1040 hp) with a displacement of 21.63 dm³. The specific fuel consumption of the Diesel engine was 200 g/kWh. The fuel tanks of the P1 and P2 had a capacity of 1380 dm³, providing a range of over 550 km without refueling. Ventilators were mounted beside the engine under the roof of the housing. Special attention was given to ensuring the proper functioning of the cooling system, particularly in regions with high temperatures. Experts from Hélice Howden assisted in adapting the cooling system for use in Brazilian tanks. The cooling system had a capacity of 120 liters of coolant. Despite considerations of the German MTU engine, the MWM engine was ultimately chosen due to arguments emphasizing its durability and reliability, convincing Brazilian decision-makers of its sufficiency for the expected tank mass. Both engines were equipped with the hydro-mechanical transmission system LSG 3000 developed by the German company ZF, although British transmission systems were also considered. Both systems were used as a dual power transport system. The LSG 3000 propulsion system included a torque converter clutch, main shaft, three rows of planetary gears, and a lateral converter P25000.

ARMOR PROTECTION AND LWS:

The armor of the tank was meant to stop 105mm rounds like L28 APDS (Armor Piercing Discarding Sabot) or M735 APFSDS (Armor Piercing Fin-Stabilized Discarding Sabot) rounds at its very best at the frontal arc and 125mm HEAT (High Explosive Anti-Tank) rounds like the 3BK12M rounds thanks to a light composite armor made with collaboration with British companies, although not built to be a competitive design like Chobham armor, it was said to be good enough to stop said rounds. The armor was made using ENGESA already proven bimetallic high-hardness steel design as an outer layer, inner ceramic, aluminium and carbon fiber for the composite armor composition. The vehicle was also modified several times during the time period, mostly on the hull, but the turret was also modified, with the most important modification being the addition of a Racal Savior LWS, with a 360° azimuth coverage, and a -22.5° and 90° elevation coverage.

Commander station, note the LWS display.

Driver station, note the LWS display

LWS sensor, both prototypes had access to LWS.

How the LWS worked.

LWS Modules: https://imgur.com/IMNHOyC

MAIN ARMAMENTS AND AMMUNITIONS:
The two Osório prototypes were marketed with two main armaments opitions: a 105mm Royal Ordnance L7A3 cannon and a 120mm GIAT CN120-25 G1, both NATO standardized cannons. The 105mm cannon had access to L52 APDS-T (Armor Piercing Discarding Sabot with Tracer), L64 APFSDS-T (Armor Piercing Fin-Stabilized Discarding Sabot with Tracer), M456 HEAT-FS-T (High Explosive Anti-Tank Fin-Stabilized with Tracer), L35 HESH-T (High Explosive Squash Head with Tracer), SMOKE shells, and training purpose APDS and HEAT projectiles. For the 120mm ammunitions, it had access to 120 OFL G1 APFSDS-T (Armor Piercing Fin-Stabilized Discarding Sabot with Tracer), 120 OCC G1 MP-HEAT-FS (Multipurpose High Explosive Anti-Tank Fin-Stabilized with Tracer) as well as their training purpose versions. The 105mm L52 APDS projectile could penetrate up to 120mm at 60° obliquity at 1830m and 280mm and 254mm at 0° obliquity at 1000m and 1500m respectively, while the L64 APFSDS could penetrate a NATO Heavy Single target at 4200m, NATO Heavy Triple target at 4800m, the M456 HEAT-FS projectiles could penetrate up to 400mm RHA equivalent at 0° at any range and 200mm RHA equivalent at 60° at any range, its HESH projectile was meant for bunkers, with these projectiles having a maximum range of 2000-2500m, 2500-3000m, 2500m and 2000-3000m respectively. The 120mm APFSDS projectile could penetrate up to 480-500mm RHA equivalent at 0° at 100m, and around 420mm RHA equivalent at 1000m, while its MP-HEAT-FS round could penetrate 480mm RHA equivalent at 0° at any range and 240mm at 60° at any range,with both projectiles having a maximum effective range at around 3000-4000m.

THE FATE OF THE PROTOTYPES:

The Osório P1 was mostly trialed in Brazil and Saudi Arabia, while the P2 was mostly trialed in Saudi Arabia and Emirates Arab States deserts, the trials were all carried successfully, however, due to shift in governmental power and a economic crisis that hit South America in the late 1980's and only started recovering in the 1990's to early 2000's, both prototypes of the vehicles never saw production, and in 2003, both prototypes briefly entered service within the Brazilian Army seeing very limited service as they were mostly used for demonstrations and parades, and in 2013 they were sent to museums in Rio de Janeiro. However, in 2022, the P2 was restored for the Brazilian Army 200 Years Independence Day parade, and in 2024, the P1 was refurbished for a special event for military vehicles collectors where the P1 was parked alongside a restored VETE T-1 Cutia, with the P1 being one of the main attractions of the event.

For better history about the vehicle, check this video by ConeOfArc:

Promotional video with English subtitles:

Thank you for reading this post, I really appreciate for whoever stopped by and read this post! <3
— Type3Kiryu, aka some_random_tank_nerd