The Mark 14 Torpedo: Problem Child of the US Navy

In the early months of World War II, the US Navy was finding it difficult to get a leg up on their Japanese opponents. One of the thorniest issues was a piece of weaponry used by American submarines throughout 1942 and 1943. Though the United States had turned the tide of the war by the middle of 1942, submarines were still proving largely ineffective against the Japanese fleet. A big part of the problem was found to be linked to the Mark 14 torpedo.

Multiple Problems with the Mark 14

Periscope view of Gifu Maru sinking after being hit by USS Seawolf (SS-197)

Attesting to the failure of the Mark 14 was Lieutenant Commander Frederick B. Warder, captain of the USS Seawolf (SS-197). Over the course of six patrols, Warder noted an issue with the torpedoes as they seemed to be unable to hit their mark. Seawolf recorded multiple instances where the Mark 14 failed to perform as intended. After approaching a Japanese invasion force that had anchored off of Christmas Island, Seawolf fired a spread of torpedoes at the light cruiser Naka. Only one torpedo struck the Japanese cruiser, allowing her the chance to limp away for repairs. On several different occasions, Seawolf fired on enemy ships and though her crew heard explosions, there was never any indication that the target was struck. When Warder switched back to the older Mark 10 torpedo, the ship saw a noticeable improvement in successful hits.

Finding Solutions

Determining what was wrong with the Mark 14 required a series of tests. Designed to be superior to the Mark 10, the tests found that there was a flaw in the torpedo's design and testing. It was an expensive flaw, as the torpedo was found to dive 10’ deeper than what it was intended to. In many instances, this meant the torpedo glided beneath the intended target. That discovery was only the first of the Mark 14’s problems, however. Continued testing also found that the torpedo often detonated prematurely due to faulty magnetic detonators, and the contact detonators jammed when the Mark 14 actually hit its target.

Mark 14 torpedo on display in Florida

Addressing the issue of the Mark 14’s inaccurate running depth was as simple as moving the depth control valve, but finding a solution for the magnetic detonator was a more difficult task. So difficult, in fact, that the magnetic detonator was scrapped completely in favor of just using the contact mechanism. Unfortunately, there were still kinks to work out with that component. Further testing on the Mark 14 found that the firing pin was too heavy for the torpedo and the solution to this problem came from a very surprising source.

During the attack on Pearl Harbor, multiple Japanese planes were shot down, giving the US military the opportunity to study the craft. Upon inspection of the propeller blades of these aircraft, they were found to be made from a lightweight metal that would work perfectly as the material for the firing pin.

By the end of 1943, the Mark 14 had been redesigned to be a more effective weapon of war. The improvement was noticed almost immediately when the USS Haddock (SS-231) sank two Japanese ships with four torpedo hits.

After the improvements were implemented, the Mark 14 remained in use in the US Navy until 1980.