In the early 1910s, only a dozen years after inaugurated the Navy's undersea force, naval strategists had already begun to wish for submarines that could operate as long range
reconnaissance vessels, in closer collaboration with the surface fleet than the Navy's existing classes, which had been designed primarily for coastal defense. These notional "fleet" submarines would necessarily be larger and better armed, but primarily, they would need a surface speed of some to be able to maneuver with the 21-knot
battleships the battle fleet was built around. This was the designed speed of the and later battleships, including the
Standard-type battleships that were under construction and proposed in 1913. In the summer of 1913,
Electric Boat's chief naval architect, former naval constructor
Lawrence Y. Spear, proposed two preliminary fleet-boat designs for consideration in the Navy's 1914 program. In the ensuing authorization of eight submarines, Congress specified that one should "be of a seagoing type to have a surface speed of not less than twenty knots." This first fleet boat, laid down in June 1916, was named
Schley after
Spanish–American War hero
Winfield Scott Schley. With a displacement of 1,106 tons surfaced, 1,486 tons submerged, on a length of ,
Schley (later
AA-1, and finally
T-1) was twice as large as any previous U.S. submarine. To expedite production Spear simply expanded an existing partial double hull design for a foreign customer without thickening the hull plating or strengthening the framework. This resulted in a complicated tank arrangement and a diving depth that was limited to . To achieve the required surface speed, two
diesel engines arranged in tandem on each shaft drove twin screws, and a separate diesel generator was provided for charging batteries. Although
Schley and two
sister boats authorized in 1915 -
AA-2 (later
T-2), and
AA-3 (later
T-3) - initially all made their design speed of , they could only maintain that speed for short periods of time before extreme torsional vibration problems with their tandem engines forced them to slow. As the engines were clutched together, it was impossible to perfectly synchronize their operation and that resulted in an unbalanced situation. That and other circumstances resulted in poor engine reliability. The engineering plant included four
New London Ship and Engine Company (NELSECO) 6-EB-19
four-cycle six-cylinder diesels, each in two tandem pairs, and two
Electro Dynamic main electric motors, each,
directly driven by the engines. Two 60-
cell Exide batteries provided submerged power. One NELSECO four-cycle four-cylinder auxiliary
diesel generator was included to charge batteries while the main engines were operating at high speed. From 1923 to 1927,
T-3 was re-engined with two German-built
Maschinenfabrik Augsburg Nürnberg AG (MAN) four-cycle ten-cylinder diesels, each. In addition to the usual four bow
18 inch (450 mm) torpedo tubes, the design incorporated two twin trainable external torpedo tubes in the deck superstructure, immediately forward and aft of the sail. These could fire on either broadside, but not dead ahead or dead astern. Two
3-inch (76 mm)/23 caliber retractable
deck guns were in the original design for the submarines, but they were never installed. As with other contemporary U.S. submarine designs, the
AA-1 class was optimized for a high submerged speed, with a small conning tower fairwater and no bridge structure, although "chariot" style bridge structures were later added to all three boats. In August 1918
T-1 was experimentally rearmed with a single
4-inch (102 mm)/50 caliber non-retractable gun at the expense of the forward trainable torpedo tubes, probably to test the effect of a bigger gun on submerged speed as well as provide more anti-ship firepower. Larger submarine deck guns were considered because many German
U-boats were equipped with guns of up to and some were equipped with 150 mm (5.9 inch) guns. The 4 inch gun would later become standard on the
S-class submarines. The trainable tubes were eliminated from the design by the time AA-2 and AA-3 were commissioned, and only AA-1 was so equipped. == Service ==