National Geographic NG770A, Instruction Manual

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USING SLIDE RULE
This rule is good for…
Multiplication Division
Proportion Square root
Time required Fuel consumption
Estimated flight time Other flying problems
Note: Use the control turning bezel located above the crown to move
the outer scale. This scale cannot place a decimal point; therefore,
the calculation of this watch should be used as a guide only.
(1) Time Required
Example: Obtain the time required for the flight of an aircraft at 180
knots for 450 nautical miles.
Operation: Align "18" on the outer scale with the SPEED INDEX on
the inner scale. Then, "45" on the outer scale corresponds to "150.1"
on the inner scale (time scale). Thus, the time required for the flight
is 2 hours and 30 minutes.
2