Aerial Torpedo - Tactics and Usage - World War II

World War II

On the night of November 11–12, 1940, Swordfish biplane torpedo bombers of the British Fleet Air Arm sank three Italian battleships at the Battle of Taranto using a combination of torpedoes and bombs. In the course of the chase of the German battleship Bismarck torpedo strikes were attempted in very bad seas, and one of these damaged her rudder allowing the British fleet to catch her. The standard British airborne torpedo for the first half of World War II was the Mark XII, an 18-inch-diameter (460 mm) model weighing 1,548 pounds (702 kg) with an explosive charge of 388 pounds (176 kg) of trinitrotoluene (TNT).

German aerial torpedo development lagged behind other belligerents—a continuation of neglect of the category during the 1930s. At the beginning of World War II, Germany was making only five aerial torpedoes per month, and half were failing in air-drop exercises. Instead, Italian aerial torpedoes made by Fiume were purchased, with 1,000 eventually delivered.

In August 1941, Japanese aviators were practicing dropping torpedoes in the shallow waters of Kagoshima Bay, testing improvements in the Type 91 torpedo and developing tactics for the attack of ships in harbor. They discovered that the Nakajima B5N torpedo bomber could fly 160 knots (296 km/h; 184 mph), faster than expected, without the torpedoes striking the bottom of the bay 100 feet (30 m) down. On December 7, 1941, the leading wave—40 B5N torpedo bombers—used the tactic to score more than 15 hits during the attack on Pearl Harbor.

In April 1942, Adolf Hitler made the production of aerial torpedoes a German priority, and the Luftwaffe took the task over from the Kriegsmarine. The quantity of available aerial torpedoes outstripped usage within a year, and an excess of aerial torpedoes were on hand at the end of the war. From 1942 to late 1944, about 4,000 aerial torpedoes were used, but some 10,000 were manufactured during the whole war. Torpedo bombers were modified Heinkel He 111 and Junkers Ju 88 aircraft, but the Focke-Wulf Fw 190 fighter aircraft was successfully tested as a delivery system.

The Mark 13 torpedo was the main American aerial torpedo, yet it was not perfected until after 1943 when tests showed that it performed satisfactorily in only 33 of 105 drops made from aircraft traveling faster than 150 knots (280 km/h; 170 mph). Like the Japanese Type 91, the Mark 13 was subsequently fitted with a wooden nose covering and a wooden tail ring, both of which sheared off when it struck the water. The wooden shrouds slowed it and helped it retain its targeting direction through the duration of the air drop. The nose covering absorbed enough of the kinetic energy from the torpedo hitting the water that recommended aircraft height and speed were greatly increased to 2,400 feet (732 m) high at 410 knots (760 km/h; 470 mph).

In 1941, development began in the United States on the FIDO, an electric-powered air-dropped acoustic homing torpedo intended for anti-submarine use. In the United Kingdom, the standard airborne torpedo was strengthened for higher aircraft speeds to become the Mark XV, followed by the Mark XVII. For carrier aircraft, the explosive charge remained 388 pounds (176 kg) of TNT until later in the war when it was increased to 432.5 pounds (196.2 kg) of the more powerful Torpex.

During World War II, U.S. carrier-based torpedo bombers made 1,287 attacks against ships, 65% against warships, and scored hits 40% of the time. However, the low, slow approach required for torpedo bombing made the bombers easy targets for defended ships; during the Battle of Midway, for example, virtually all of the American torpedo bombers were shot down.