Aerial Torpedo - Tactics and Usage - Interwar Years

Interwar Years

The United States bought its first 10 torpedo bombers in 1921, variants of the Martin MB-1. The squadron of U.S. Navy and Marine fliers was based at Naval Weapons Station Yorktown. General Billy Mitchell suggested arming the torpedo bombers with live warheads as part of Project B (the anti-ship bombing demonstration) but the Navy was only curious about aerial bomb damage effects. Instead, a trial using dummy heads on the torpedoes was carried out against a foursome of battleships steaming at 17 knots. The torpedo bombers scored well.

In 1931, the Japanese Navy developed the Type 91 torpedo, intended to be dropped by a torpedo bomber from a height of 330 feet (100 m) and a speed of 100 knots (190 km/h; 120 mph). In 1936, the torpedo was given wooden attachments to the tail to increase its aerodynamic qualities—these attachments were shed upon hitting the water. By 1937, with the addition of a breakaway wooden damper at the nose, the torpedo could be dropped from 660 feet (200 m) and a speed of 120 knots (220 km/h; 140 mph). Tactical doctrine determined in 1938 that the Type 91 aerial torpedo should be released at a distance of 3,300 feet (1,000 m) from the target. As well, the Japanese Navy developed night attack and massed day attack doctrine, and coordinated aerial torpedo attacks between land- and carrier-based torpedo bombers.

The Japanese divided their bomber squadrons into two groups so as to attack an enemy battleship from both frontal quarters and make it extremely unlikely for it to be able to avoid the torpedoes by maneuvering, and more difficult for it to direct anti-aircraft fire at the bombers. Even so, Japanese tactical experts predicted that, against a battleship, the attacking force would be able to score hits at a rate of only one-third that observed during peacetime exercises.

Beginning in 1925, the United States began designing a special torpedo for purely aerial operations. The project was discontinued and revived several times, and finally resulted in the Mark 13 torpedo which went into service in 1935. The Mark 13 differed from aerial torpedoes used by other nations in that it was wider and shorter. It was slower than its competitors but it had longer range. The weapon was released by an aircraft traveling lower and slower (50 feet (15 m) high, 110 knots (200 km/h; 130 mph) than its Japanese contemporary.