ANTI SUBMARINE WARFARE ATTACKS [Main Title]

A film focusing on the conditions necessary for a successful airborne attack on a submarine. The element of surprise is absolutely critical, the attack must be initiated before the (submarine) observers spot the attacker. Failure to do so usually results in an aborted operation.

Reel 1: Film opens with submarine on the surface, the three lookouts scanning the skies for enemy aircraft. When an aircraft is searching for U boats there are certain problems to overcome before an attack can be made. Having sighted the target, the pilot approaches carefully to minimise the chance of detection before he completes his attack. A U-boat can crash dive in 30 seconds and in the following 30 seconds submerge to 60 feet well below the danger line of a depth charge. Cut to U-Boat preparing to crash dive. The search aircraft is 3 nautical miles away and takes 60 seconds to reach the submarine, which has submerged an additional 45 feet. Clearly, the aircraft needs to be closer before detection. The amount of cloud cover and type is critical, particularly so in the absence of radar facilities on the aircraft. The different cloud formations are illustrated. The merits of flying above, in, and below cloud formations explained. A series of animated diagrams list a range of attack plans based on the cloud parameters at a given location. For a U Boat submerging its water track is used by the aircrew to calculate a dropping point ahead of the U Boat, allowing time for the depth charge to sink to its detonation depth. Success depends upon the aircraft remaining un-detected before being detected itself. Reel 2: Detailed instructions for attacking a U Boat that has just submerged, leaving a swirl in the sea, are given in a series of diagrams. The character and size of the swirl are used to determine the dropping point for a series (stick of 6) depth charges, set to detonate at a specific depth. Weapons. Cut to depth charges loaded into the bomb bay of a Lockheed Hudson aircraft. Depth charges have the most lethal effect for their weight, and the aircraft can fly very low over the target without fearing the explosion will damage the aircraft. Depth charges are set to detonate at comparatively shallow depths to sink a U-Boat near the surface. Charges set to detonate at great depth will not cause any permanent damage to a U-Boat. After an attack it is important to assess the damage; debris, clothing, bodies on the surface are sure signs of a kill. At shallow depths, a mortally damaged U-Boat will in all probability rise to the surface, the crew exit rapidly, and sink again. Oil alone may give the wrong impression since it is often carried in saddle tanks, outside the pressure hull. Damaged but not sunk. The relationship between the swirl and the depth charge disturbance may be taken as a guide to the extent of damage. Photographs of the disturbed water are taken with a mirror camera; measurements of identifiable patterns seen in the photographs are made by photo interpreters (cut to office of the Photo Interpreters) and can give a valuation of the damage sustained by the U-Boat. Film closes with a Whitley aircraft successfully attacking a U-Boat.