Almost forgotten today, the Osorio was a prototype main battle tank developed by Brazilian arms manufacturer Engesa during the 1980s. The Osorio was named in honour of Manuel Luis Osório, founder of the Brazilian Army’s cavalry branch.
The vehicle was developed as a private venture, with little government investment. Only two prototypes were ever constructed. The first being completed in 1985, with the second following in 1986.
Brazil was just beginning to emerge as an industrial democracy at the time of the Osorio’s development, so the vehicle was designed to accommodate that nation’s limited transportation infrastructure. Weight was held to no more than 43 tonnes, the maximum load capacity of most road bridges and overpasses in Brazil. Similarly, the vehicle was sized with Brazil’s existing road and rail tunnels, tank transporters, and rail cars in mind. As this infrastructure was comparable to that of much of the Developing World in the 1980s, it was thought that the Osorio would be ideal for export to these nations.
The Osorio tank was fitted with composite armour at the front of the hull and turret. This composite was broadly similar to Britain’s Chobham armour. It comprised steel, aluminium, carbon fibres and ceramics. Though the Osorio’s armour was kept light, it was also strong, rated to defeat any anti-tank projectile in service at that time.
The EE-T1 version of the Osorio, intended for the Brazilian Army, was armed with a British Ordnance L7A3 105mm rifled gun, and carried a total of 45 rounds. The EE-T2 was intended for export customers and was armed with a more powerful French GIAT G1 120mm smoothbore gun, though ammunition stowage had to be reduced to 38 rounds. Both guns were fully-stabilized and manually loaded. The EE-T2 variant was claimed to have a first round hit probability of 80%, at 2 km range, against moving targets.
Secondary armament of the EE-T1 consisted of two 7.62mm machine guns. One was mounted coaxially, the other placed on the turret roof. The EE-T2 was also fitted with a coaxial 7.62mm machine gun, but a 12.7mm machine gun was placed atop the turret.
Crew consisted of a commander, gunner, loader and driver, the conventional four-man configuration.
Mindful of their tight development budget, Engesa’s buyers shopped the world for proven tank technologies. From Netherlands came the MWM TBD 234 diesel engine, which developed 1040 horsepower, and enjoyed a solid reputation for reliability in demanding industrial applications. Germany supplied the ZF LSG300 automatic transmission, also used in the Korean K1, Italy’s C-1 Ariete, and the Leopard 2. Together, the engine and transmission formed a single power pack, which could be replaced within 30 minutes under field conditions. The Osorio’s Diehl 570 tracks, the same type found on many other western AFVs, also came from Germany. From Britain came the Dunlop hydro-pneumatic suspension system, also used in the Challenger series of tanks, the 105mm L7A3 cannon, and Vickers designed and built turrets.
Once the two Osorio prototypes had been assembled and tested, Engesa began seeking international orders. In a competition held by Saudi Arabia, the Osorio bested such heavyweights as the M1A1 Abrams, AMX-40, and Challenger I. An order never came, however, as, for political reasons, the Saudis ordered the American M1 Abrams tank instead. No other country showed interest in the $3.8 million U.S. dollar Osorio, and the project began to unravel. Ultimately, after investing the equivalent of $100 million dollars into the Osorio project, Engesa filed for bankruptcy.
The only two completed prototypes an EE-T1 and an EE-T2 were handed over to the Brazilian army, which displays them in public only on rare occasions.