Speed drift & direction calculator - airship

Speed, drift & direction calculator, used on RN airships during the First World War. It is also known as a course and distance calculator.

Three plates revolve around a central nut. The largest plate has scales for time or distance, the middle plate for points of the compass and minutes, and the smallest plate is a grid with four sets of graduations at 90 degree intervals, of 30-110, radiating from the centre. There are also two arms graduated 20-110 radiating from the centre.
Rear surface: plain, painted cream/white.

Appears to be the earliest pattern of this form of calculator as it does not carry the later Mk I or Mk II designations. Its purpose is to solve the vector navigation triangle of speed, direction, distance.

Diameters of plates: large 7" (17.8 cm), Medium 6.5" (16.5 cm), Small 4.75" (12.1 cm)
Length of arms: 2.5" 96.4 cm)

Object Details

ID: NAV0137
Type: Speed drift & direction calculator - airship
Display location: Display - Forgotten Fighters
Creator: Unknown
Events: World War I, 1914-1918
Date made: circa 1915
People: York-Moore, Thomas Philip
Credit: National Maritime Museum, Greenwich, London
Measurements: Overall: 10 mm; Diameter: 180 mm
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