the 'CUTIE'

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The 'CUTIE'

The standard torpedo for the Bergall was the Mk.14. These were 21" across and 246" long. They were not very effective in shallow water or against shallow draft ships like the escorts that haunted Lombok Strait. The Navy was busy developing a solution. One solution was the Mk.27. Being only 19" x 92", two could be carried in a single torpedo rack. It was an anti-escort, passive acoustic homing torpedo designed to 'swim out' of the torpedo tube under it's own power. This left no 'tell-tale' air bubbles that was normal for a standard torpedo that was pushed out the tube with compressed air. This prevented the enemy from observing the source of the torpedo, especially useful in shallow water or in near proximity to a target. At 720 total pounds, it carried 95 pounds of Torpex explosive. It was limited in use as it's speed was only 12 knots at a maximum range of 5,000 yards.

Homing torpedoes are dramatically different from the gyro-controlled, set depth torpedoes used against surface ships in that once they acquire their target, they home on it autonomously using on-board controls. In addition to the obvious advantage of homing in the horizontal plane in attacking surface targets, homing can operate in the vertical plane thus providing an important capability against shallow draft escorts.

Target detection was accomplished by four hydrophones symmetrically arranged around the circumference of the torpedo mid-section in the left, right, up and down positions. Such an array is useful for target acquisition because the four hydrophones together cover essentially all directions from the torpedo and for homing because "body shadow", meaning that the hydrophone on the right side, for example, being in the acoustic shadow of the torpedo body could not hear a target on the left side, provides directionality. The basic idea is to compare the signals from the left and right hydrophones and move the rudder in such a way as to steer towards the stronger signal. In the BTL implementation of this scheme, the hydrophone signals were amplified, rectified and subtracted. This net signal was combined with the voltage from a potentiometer which was coupled to the rudder. The combined signal drove a DC amplifier which, in turn, controlled a differential relay that caused the rudder motor to move in the appropriate direction to reduce the input voltage (hydrophone derived voltage plus rudder potentiometer voltage) to zero. The vertical control circuit was identical except for including inputs from a hydrostat that measured depth and a pitch pendulum, which were also voltages derived from potentiometers. These signals caused the torpedo to operate at a fixed depth until a sufficiently strong acoustic signal was received. When such a signal was detected, the hydrostat/pendulum control was disabled and acoustic depth control prevailed. As a safety feature, acoustic depth control was disabled and hydrostat/pendulum control re-established if the torpedo dove below a limit set to about 150 feet. These control systems produced rudder angles that were proportional to the difference in strength between the signals from the right and left (or up and down) hydrophones.

It was recounted by J.J. Ott, that it was fun (during operational checks) to make noises from several directions and watch the 'cutie' rudder and elevator wiggle around, trying to acquire the source. As they were an acoustic device, all effort must be made to insure that the submarine is quiet immediately after the launch or (being closer to the sub than the target) the torpedo would acquire the submarine. Since the Bergall failed to remove engine power before firing the first 'Cutie', it was the "loudest" target found when the 'Cutie' was released. The first 'Cutie' used fired by the Bergall against an enemy vessel, almost acquired the Bergall!

The enemy ship had to be "drawn" into close proximity to the submarine in order for the 'Cutie' to acquire the target. On the Bergall this was accomplished by rising to periscope depth, raising the periscope and "wiggling" the scope around, giving the enemy a better chance of seeing the periscope head. At this point the patrol craft would begin a run on the submarine. The Bergall would then drop to about 150 feet depth and wait as the enemy before firing.

The Mk.27 torpedo was based on the Mk.24. The original Mk.27 Mod 0 was a minimally modified Mk.24 with wooden rails to fit 21" torpedo tubes, and various arming, warm-up and starting controls to suit a torpedo tube, swim-out launch mode. Eleven hundred Mk.27 Mod.0 torpedoes, known as CUTIE, were built by Western Electric and delivered between June 1944 and April 1945

From Clay Blaire's book... Silent Victory, vol 2 pages 762 and 763

New Inventions for U.S. Boats

In the fall of 1944, scientists and technicians in the States, working hand in glove with submariners, developed several secret new devices for the fleet submarine designed to enhance its effectiveness in combat. These were: (1) a “noisemaker," a decoy device fired from a submarine undergoing depth-charge attack, to fool enemy sonar; (2) a "night" periscope (one that admitted much more light in darkness), also fitted with a radar known as the ST; (3) a new and extremely short-range sonar, QLA (but called PM because frequency modulated); and (4) a small electric acoustical torpedo, called a "Cutie," which would home on the noise of an enemy ship. Lockwood, forever fascinated by new gadgets that might improve sinkings or provide greater protection for his boats, took a deep and personal interest in each of these devices.

The most promising in many ways were the Cuties, which Spike Hottel and Harry Hull (ex-Thresher), Lockwood's force gunnery and torpedo officer, began receiving in the summer of 1944. They were based on a German design and manufactured by Westinghouse. Like all new torpedoes produced by the Bureau of Ordnance, they were imperfect. In tests, they repeatedly malfunctioned, and the first models were useless against a target going more than 81/2 knots--a severe limitation.

In the fall, when the Cutie had been improved somewhat, Carter Bennett arrived in Pearl Harbor in a new boat, Sea Owl. Since Bennett had a master's degree in torpedo ordnance and much combat experience, Lockwood selected him to make the first combat test of the Cutie. Bennett led a wolf pack consisting of Sea Owl, Piranha, commanded by Harold Ruble, and Sea Poacher, commanded by Francis Michael Gambacorta, to the East China and Yellow seas. Bennett carried several Cuties in his racks.

The pack, often diverted to lifeguard B-29 raids (staged from bases in China), had little opportunity to conduct coordinated attacks, but Bennett made three opportunities to test the Cutie. The first was in the shallow waters of the Yellow Sea. Bennett picked up a small patrol craft, then took position ahead and dived to 150 feet, the depth considered safe to fire a Cutie (anything less and the Cutie might turn and home on the launching submarine). The Cutie performed as designed, presumably, homing on the propeller noise of the patrol craft. Hearing an explosion, Bennett surfaced to investigate. He found the patrol craft in "sinking condition" and left, judging this first combat employment of the secret weapon an unqualified success.

The next two opportunities were not so conclusive. On the second, Bennett found what he believed to be a destroyer off Nagasaki. Employing the same tactics, Bennett fired a Cutie, heard an explosion, and surfaced. The target (not a destroyer but a patrol craft) appeared to be damaged but not severely. Bennett approached from dead ahead of the target and fired a Mark XVIII electric from 1,000 yards. The electric hit solidly and the patrol craft disintegrated; Bennett ran through the debris to make certain.

Not long afterward, Bennett saw what he believed to be a destroyer coming out of Nagasaki, presumably to aid the ship Bennett had just sunk. Bennett submerged (it was almost dawn by then), took position on the enemy track, and fired a couple of more Cuties. This time, no luck, either because the target was going much too fast or because it spotted the torpedoes and evaded. "The last time we saw him," Bennett said later, "he was going over the hill for Nagasaki."

When Bennett returned from patrol, Lockwood was pleased. Although the test had been "spotty" (as Lockwood described it), it seemed to him that the Cutie had merit, especially as a weapon to use against shallow-draft antisubmarine vessels. Even if the Cutie didn't sink them, it might damage the propellers and force them to stop, as had been the case in Bennett’s first two attacks. Then, once they had been stopped, a submarine might actually sink them with another Cutie or with a regular electric set to run at shallow depth from short range, as Bennett had done in his second attack. However, follow-up combat tests of the Cutie were not so successful. Hull, Hottel, and others went on trying to debug it and waited for later models, that could hit faster targets.

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