Target angle Angle on the bow provided the basis for submarine attack decisions through the world wars. When angle on the bow was less than 90° , the submarine would continue a submerged approach toward the target to launch torpedoes when angle on the bow increased to 90° indicating the minimum range torpedo launch opportunity for the submarine with the given target course and speed. Unless the target was already within torpedo range, angle on the bow greater than 90° required the submarine to attempt to surface and run around the target beyond visual range to submerge ahead of the target. As
Type 97 90 mm Infantry Mortar Light Trench Mortar, Manufactured in 1942, Osaka Army Arsenal". The Type 97 is approximately lighter than the Type 94 90-mm mortar. This weight saving was created largely by the elimination of the Type 94's recoil mechanism, which weighed . The bipod assembly of the Type 97 is lighter than that on the Type 94. There is a cover for the level on the yoke of the Type 97 which is not on the Type 94, and the sliding bracket of the Type 97 is hinged to permit its easy removal from the leg of the bipod, whereas it is integral