As yet unaware of their torpedoes' faults, submarine skippers reported an alarming number of prematures, duds and inexplicable misses during the first full year of the war. Frustrated captains watched helplessly as their torpedo wakes passed under sterns or just aft of targets. In response to repeated requests by field commanders, the Bureau of Ordnance conducted check firings to evaluate the depth control of the Mark XIV. By February 1942, the bureau reported a variance of four feet in depth control during the initial 880 yards of a run. Since four feet of depth would make little difference when engaging a capital ship, and most attacks took place at the 1000-yard range, the bureau concluded that the torpedoes were not at fault; rather, it must have been the crews' inexperience and errors that were causing failures. The bureau further argued that even if a torpedo did slip under a shallow-draft target, the magnetic detonator would activate the warhead. Faced with such apparently sound arguments, the submariners could only redouble their fruitless efforts. After five months of desperate action, little tonnage to show for their sacrifice and continued pleas from his skippers for reliable torpedoes, Lockwood decided to conduct his own tests.

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Lockwood and his amateur scientists bought 500 feet of net from a local fisherman and moored it in deep water just outside Frenchman's Bay near Albany, Australia. A Mark XIV was obtained from an incoming submarine, Skipjack, whose crew was more than willing to part company with it. Lockwood's men modified the Mark XIV by replacing the warhead with an exercise head. This replacement head contained a calcium chloride solution that made its weight exactly the same as the warhead. The modified torpedo was loaded into a submarine, and Lockwood ordered a series of test firings.

Set to run at 10 feet, the torpedo was launched from a distance of approximately 900 yards. When divers inspected the net, they discovered the torpedo had cut the net 25 feet below the surface of the water. The next day, two additional torpedoes cut the net at eight and 11 feet deeper than set. Since he believed this extra depth had also kept the magnetic detonator from working, Lockwood ordered all of his skippers to adjust their torpedo depth settings accordingly. Most captains, not taking any chances, set their torpedoes for zero depth. Lockwood and his staff realized, however, that the malfunctioning torpedo needed to be corrected, not merely jury-rigged.

Later in July, the Bureau of Ordnance responded to Lockwood's tests by announcing they were flawed and thus not conclusive. The Stateside bureau claimed improper trim conditions had been created when the field testers used an exercise head that was shorter than the warhead. Undaunted, Lockwood's team lengthened their exercise head to warhead length and immediately produced the same incriminating evidence.

In response, Commander James King was brought out of retirement and made chief of the bureau's Research and Development section to address the depth-control problem. King had earlier been responsible for adding the extra TNT to the Mark XIV warhead and for designing the torpedo's turbine engine, the best in the world. He immediately began to conduct tests similar to Lockwood's, launching torpedoes into nets from submarines, not barges, as had been the common practice. Not surprisingly, King achieved the same results as Lockwood. On August 1, 1942, he advised the fleet that the Mark XIV ran approximately 10 to 12 feet deeper than set.

The initial culprit was the depth-control mechanism. This intricate device sets the tension of the depth spring to correspond with the water pressure at the desired running depth. The two controlling elements within the depth mechanism are the hydrostatic valve, or diaphragm, and the pendulum. Ideally, when the torpedo reached the prescribed depth, the force exerted on the diaphragm by the water would equal the force exerted on the diaphragm by the spring. The setting was adjusted and indicated on a graduated dial called the depth index wheel.

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