Description
Object description
A training film for Royal Air Force bombardiers using the Mk III bombsight. A mix of photographic images and animated diagrams clearly explain the procedure – the film is notable in that it engages with the viewer who can decide for themselves when the release point has been reached.
Content description
Film opens with an animated diagram; the new Mk III low level bombsight is designed upon a completely new principle: bombing conditions will vary but there is only one point where the bombardier may release the bombs.
" The bombing angle": When the aircraft height is small, the bombing angle is relatively large: animated diagram.
"The sight line": The purpose of the bombsight is to indicate to the bombardier that the aircraft has arrived at the release point, that is, the sight line has been reached. Examples of over-sighting and under-sighting; the correct sight line: explained.
"The angular velocity of the line of sight": explained with animated diagram; three lines of shooting are used, as seen by the bombardier; under, over and the target point; the concept of angular velocity are introduced; the target point has an angular velocity peculiar to itself. A device to indicate this angular velocity would at the same time indicate the correct line of sight; this is the Mk III bombsight.
"The moving graticule": The Mk III bombsight has a moving graticule at a constant speed, set for the conditions of the attack – explained – all the lines in the graticule have the same angular velocity, and enable the identification of the ground target, which has the same angular velocity as the moving graticule – diagram to clarify the procedure. At the bombsight, the bombardier notes how distant objects move more slowly than objects closer to the aircraft, which appear to move faster; at some point the speed of the target and that of the graticule appear to be indentical; it is here the target will be within the graticule sighting lines – animated diagram – this is the moment of bomb release.
"Try it for yourself: say 'now' when you judge the target and graticule speeds to be equal":
Film as seen through the bombsight as the aircraft approaches target area, arrives at bomb release point and flies on. The narrator repeats this exercise three more times.
Film closes with an aircraft flying over a German U-boat submarine, the narrator repeats his request, the aircraft drops its depth charges which explode, sinking the submarine.