NAUTICAL MILES O – 160 (OR 0 – 80): This scale is for use with world Aeronautical charts 1:000,000 (OR 1:500,000) and enables the direct reading of distance in nautical miles.
RADIALS0-45: These radiate from either side of the centre of the baseline, at 5′ intervals to 45″,and are used to determine the alteration to a heading to fly direct to destination from an off course “fix”. It supersedes the 1 in 60 method.
ARCS 80 – 0 – 80 n.m (OR 40 – 0 – 40).: These bisect the RADIALS at intervals and are used to determine the distance flown and distance to fly from an en route “fix”.
GROUND SPEED, TIME, DISTANCE COMPUTER: The central circular slide rule enables the pilot to solve problems involving time, speed and distance. The triangular index, A positioned at the “60 minute” graduation on the rotating scale, is known as the SPEED INDEX The outer fixed scale is known as the MILE SCALE and the inner rotating scale the TIME SCALE.