The Mark 13 torpedo was the main American aerial torpedo, yet it was not perfected until after 1943 when tests showed that it failed in 70 percent of the drops made from aircraft traveling faster than . 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 high at .