Description
Object description
A technical training film for aircrew operating air-to-surface vessel (ASV) equipment on anti-submarine patrols. The operational elements of the ASV are explained, in particular the choice of forward or sideways looking antennae, dependant on the target of the patrol. The controls of the ASV are set according to the prevailing conditions to enhance the detection of the enemy. Film of an actual attack on a U-Boat is shown.
Content description
Reel 1:
Film opens with Whitley aircraft attacking U-boat seen on the surface.
"ASV types": Two types of ASV in service. The first type searches forward only and is fitted to medium aircraft (e. g. Hudsons). The other type can search forward or sideways (beam on), and is fitted to larger aircraft (Whitleys, Wellingtons, Liberators, Catalinas and Sunderlands) Cut to photography of these aircraft, displaying their antennae.
"Height": Area covered increases with aircraft height. Explained with animated diagrams for both antenna types. Choice of height; weather, minimum height to take advantage of low cloud, sea returns and other tactical considerations.
"Attitude and size of target": ASV range depends upon size and attitude of the target; 50 miles for a destroyer, seven miles for a surfaced submarine. Cut to Hudson over the sea, making an end-on approach. Cut to ASV receiver, has three range scales 10, 40, 100 miles. Close up of ASV console and VDU (visual display unit). How to select ranges and why.
"Sea returns": Caused by reflections from the sea surface. This effect increases with height and roughness. Rough seas can swamp any target responses. Only the forward search covers the sea return area. Beam on search has a blind area to port and starboard beneath the aircraft (the sea returns are within this area), which may require a visual search. Some aircraft have both types of antennae to overcome this limitation. Cut to Whitley, four in-line vertical antenna on top of fuselage, on patrol. Choice of speed, height, range, antenna, to achieve full coverage of area. Examples shown on VDU.
"Cross over patrol": To detect any vessel passing between two fixed points (e. g. a navigation channel) a cross over patrol is mounted.
Content description
Reel 2:
"Anti submarine patrol": Film returns to the patrolling Whitley. The tactical approach to a target must consider that a submarine can be submerged 30 seconds after it has spotted the aircraft. The film considers a daylight approach (good visibility) with visual scanning and complementary radar scans, and a nigh-time approach in bad visibility, entirely dependent on radar scans.
"Anti submarine search, good visibility": Forward looking antenna deployed. Beam on (broad side) of little use. Good visual lookout. Maximise use of cloud coverage. A series of annotated diagrams give examples of the parameters chosen for the search. Explanation given.
"Anti submarine search, bad visibility, cloud, and at night": As a rule, submarines only remain on the surface at night or conditions of poor visibility. Cut to submarine on surface under heavy cloud. The A S V comes into it's own under these conditions. Flying parameters are chosen. Beam-on antenna to cover a larger area. Supplemented with forward looking antenna. Best flying height circa 1500 feet.
A submarine will often sail head into the wind when on patrol. For the best chance of success, the aircraft flies at right angles to the wind direction using forward looking antenna, and parallel to the wind using beam-on antenna. In this manner the largest possible 'blip' on the VDU may be obtained.
The film closes with footage of an actual operation. A Whitley aircraft takes off and flies over the sea. Close up of pilot visually scanning the area as he flies the aircraft. The A S V operator is scanning electronically. Cloud thins as the flight proceeds at 1500 feet. A S V operator reports a blip at 5 miles, changes range and antenna, guiding the pilot towards the target. View of CDU screen. Cut to submarine on the surface. Pilot has visual contact with the submarine; he goes to action stations. Cut to U Boat U28. The conning tower lookouts have spotted the aircraft. Submarine prepares to dive. Cut to bomb operator in aircraft scanning the VDU. Aircraft approaches. Submarine starts to dive. Bombs dropped as aircraft flies over the submerging submarine. Sea erupts as depth charges explode.