Inhauma class light patrol frigates

These German-design patrol frigates/corvettes were intended for general patrol duties. It is no secret that stability at sea has always been the great headache of the Inhaúma project. Up to 16 were planned but only 4 were built. The clearly suffer topweight problems, but more generally suffer from trying to jam too much capability into not enough ship. The effort to achieve a frigate's worth of capability in a corvette's worth of hull was doomed to failure from the outset.

The origins of the project that resulted in the "Inhaúma" class corvets go back to 1977, when the Brazilian Navy began studies to replace the ten "Imperial Sailor" class corpses in service in the District Forces, by a new class of ocean patrol vessels (NaPaOc), with a loaded displacement of 700 t. In addition to the urgent need to replace the old destroyers of American origin, the Brazilian Navy needed a larger ship in response to the construction of the new Espora-class corvettes (a project derived from the MEKO-140 class produced by the Blohm + Voss German shipyards) being built in Argentina by AFNE, Rio Santiago).

The specifications of the Brazilian Navy were changed and the "NaPaOc Project" gave rise to the "Corvette Project". In their final version, the ships had a displacement of more than 1,900 tons, thus, much larger than originally planned. The "Corvette Project" was developed by the Directorate of Naval Engineering (DEN) with technical advice from the German company Marine Technik, through a contract signed on October 1, 1981.

The "Inhaúma" class corvettes were designed to provide escort to cabotage and transoceanic trains, with capacity for anti-submarine warfare, surface warfare, antiaircraft warfare and naval fire support in amphibious operations. "Inhaúma" class corvettes are capable of operating in environments saturated with electronic emissions and locks, under air and missile threat, and can develop high speeds at low cost for long periods. They can detect, collect, evaluate, inform and react in sufficient time, in the face of rapid and precise threats, thanks to their modern sensors, integrated into an agile tactical data processing system.

In 2008, the corvette modernization process (MOD / CORV Program) was started together with the General Maintenance Period (PMG) and aimed at revitalizing mainly the machines and replacing some systems and sensors. Tactical command, control and combat systems have been replaced as well as some sensors. There is no provision for arms replacement. The modernization comprised the following facilities: Sistema SICONTA Mk.4; combined search radar Selex Sistemi RAN-20S two-dimensional DT Radar Selex Sistemi RTN-30X; Navigation radar Furuno FR 8252; MAGE Defender; Inertial Navigation System SIGMA 40 INS; SCM Control and Monitoring System; General maintenance of machinery; Review of hydraulic and electrical systems; Revitalization and improvement of habitable areas.

The system of propulsion of the corvettes is of the type CODOG (Combined Diesel or Gas Turbine combination with diesel engine or gas turbine), with a Gas turbine General Electric LM-2500 (nationalized in 15%, base, envelope, group of discharge of gas and other parts) of 27,000 HP and two MTU 16V 596 TB91 diesel engines (nationalized at 42%.) of 3,900 HP each, moving two shafts with KaMeWa controllable pitch propellers and two rudders, and ships equipped with Vosper stabilization system active by fins. The maximum sustained speed is 27 knots (50 km / h) with gas turbines and 18 knots with diesel engines.

The Inhaúma Class were planned as a combat vessel much cheaper to acquire than the Class Niterói frigates, but with almost the same firepower (Exocet and Mk 46 torpedoes) mounted on a smaller hull. They would essentially be "frigates in an Ocean Patrol Vessel", which consequently required a smaller crew than Niteroi. The Corvettes required a great number of hours of maintenance by the crew which was incompatible with the number of man-hours available for its accomplishment.

The well-known 4.5-inch Vickers cannon turned out to be very heavy for the corvettes and its positioning in the bow multiplied the tendency of the ship to "bite", oscillate in the longitudinal axis, which combined with the bow low in seas a little more strong, would eventually produce a lot of seawater inlet on the front deck. This caused a greater wear of the cannon's own gears due to the frequent contact with the salt water, besides making very dangerous the presence of military in the bow. This restriction hampered a series of operations on the bow deck, especially the very important oil transfer at sea.