Aquila′s new machinery, and the bow flare increased to increase seaworthiness and provide additional space for air requirements. In order improve resistance to underwater damage, the ship was heavily subdivided with 18 watertight bulkheads extending up to 'C' or 'D' deck, 11 of which were double. The designers worked in of armor over the magazines and aviation fuel tanks. The fuel tanks copied British practice and consisted of cylinders or coffer dams separated from the ship's hull by water-filled compartments. This was a safety measure intended to prevent fracturing of the fuel system and the inadvertent spread of volatile AvGas fumes due to severe vibration or "whip" from bomb hits, near misses and torpedo hits. armor was applied on external plating to protect the steering gears. Machinery Self-propulsion tests at the Freude tank at La Spezia in January 1942 indicated that for a trial displacement of 26,700 tons, a speed of 29 knots could be achieved with 132,660 shp. This indicated that a sustained speed of 29.5 knots could be reached with an output of 140,000 shp, and 30 knots if the propulsion system could develop 151,000 shp without being forced. Aquila′s new propulsion system was taken from two canceled Capitani Romani-class light cruisers (Cornelio Silla and Paolo Emilio), as despite their cancellation the fabrication of their propulsion systems was in an advanced stage. Totaling eight boilers and four turbine groups, each of these was capable of generating 55,000 shp at 310 rpm, more than adequate for the needs of Aquila. Each boiler operated at a pressure of , with the superheated steam being fed to the turbines at a pressure of and a temperature of . As installed on Aquila, the overall output in shaft horsepower was reduced, to a maximum of 37,750 shp per turbine group at full normal power. The propellers used were also modified to a type more suitable for a larger ship - whereas the original propellers used by the Capitani Romani-class had three blades and a diameter of , those used by Aquila had four blades and a diameter of . In order to increase survivability, the propulsion systems were grouped into four engine rooms, each with one turbine group and two boilers - a similar solution to what the Americans adopted for the North Carolina-class battleships. This solution made it possible to simplify piping of all kinds (steam, water, oil, etc.), ventilation systems,