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AGSS-569 Albacore 1957-1961 - Phase III

Phase III took place from 1957 to 1961. Phase III testing, completed in August 1961, included a radical "X" configuration for the stern planes, dive brakes, a large sail-mounted rudder, and a new bow dome for a high performance sonar. A succession of sonar and noise studies followed including testing of "Towflex," an early version of the towed sonar array carried by modern attack submarines.

In November 1956, Albacore re-entered the shipyard for engine conversion. She departed New London, 11 March 1957, for operations out of San Juan, Puerto Rico, and Guantanamo Bay, Cuba. The submarine returned to Boston on 2 April 1957 and operated locally out of Boston and Portsmouth. From November 1957 to March 1958, Albacore returned to the Portsmouth Naval Shipyard for engine maintenance followed by further noise reduction studies and tactical training with antisubmarine units.

Albacore entered the Portsmouth Naval Shipyard early in 1958 for an overhaul which lasted until June 1958. The ensuing tests emphasized sound reduction and included extensive evaluation of Aquaplas, a sound dampening plastic which had been applied to the ship's superstructure and tank interiors. The bow diving planes were removed in October 1958 as part of noise reduction testing. This was so successful that they were not subsequently refitted. The submarine ended the year with a fortnight's run to Halifax, Nova Scotia, and back to serve as a target ship for Canadian warships.

In 1959, a newly designed 14-foot propeller was installed and tested. Albacore sailed south late in May and, after operating in the British West Indies for two weeks, proceeded to Key West to serve as a target for the Surface Antisubmarine Development Detachment. After returning north, she spent much of the remainder of 1959 and most of 1960 undergoing widely varied tests for the David Taylor Model Basin. One of the more unusual consisted of evaluating a concave bow sonar dome.

On 21 November 1960, the ship entered the Portsmouth Naval Shipyard for a major overhaul and conversion in which she received: a new, experimental, "X"-shaped tail for increased control; 10 dive breaks around her hull; a new bow which included modified forward ballast tanks; new sonar systems; and a large auxiliary rudder in the after part of her sail. Following the completion of this work in August 1961, she operated along the east coast learning the effect of her new configuration and equipment upon her capabilities and performance.

The designers again experimented with new control surfaces. In this phase, control surfaces were still forward of the propeller but were mounted diagonally, forming an "X"-shaped configuration. This new design was expected to facilitate sharper turns, so a larger dorsal rudder was installed on the sail and re-activated. Ten hinged panels ringing the aft part of the boat were installed on Albacore as speed brakes. These panels were hydraulically operated to slow the boat rapidly if necessary. In addition, a drag parachute from a B-47 bomber was installed on the aft edge of the sail, which could be opened and streamed in an emergency to slow the boat and decrease the down angle. As clever as this idea may have seemed, the parachute ripped out after three test runs and was deleted from future designs.

The "X" stern configuration and dive brakes were potential solutions to a recurring concern about uncontrollable crash-dives. Because the individual control surfaces in the X configuration needed to operate with coordinated motions to affect a dive, no single mechanical failure could cause a crash dive. Because these potentially-dangerous inadvertent dives were less likely, Albacore could attempt more dangerous maneuvers at little risk. Nonetheless, neither of these features would be included in the next design. The dive brakes occasionally opened on their own at high speeds, and the X-stern required computer control at a time when computers were little understood and yet to be trusted.

With the addition of a motor-propeller system to the lower rudder of USS ALBACORE (AGSS 569) the possibility existed that local resonance frequencies of the rudder within the operating speed range of the ship would occur and hence increase the vibratory response of the ship to propeller-blade forces acting on the rudder. Theoretical analysis indicates, however, that the addition of the motor-propeller system to the rudder would not cause excessive vibrations. This conclusion was verified experimentally.