# THE CALCULATOR SIDE OF THE FLIGHT COMPUTER

THE CALCULATOR SIDE OF THE FLIGHT COMPUTER

- The calculator side consists of a stationary portion with a flat circular portion attached. The circular portion can be turned.
- The numbers along the outside of the stationary portion are referred to as the OUTER SCALE in this document.
- The outer scale is used to represent distance, fuel, groundspeed, true airspeed, or corrected (true) altitude, depending on the calculation being performed.

- The numbers on the edge of the rotating portion are referred to as the INNER SCALE in this document.
- The inner scale is used to represent time, calibrated or indicated airspeed, and calibrated or indicated altitude, depending on the calculation being performed.
- The number “60” on the inner scale has been replaced with a triangular-shaped arrow, referred to as the Index ().
- This arrow is used as a reference to a rate, such as knots (nautical miles per hour) or gallons per hour.

- In the center of the rotating portion are three “holes” (windows) used to compute corrected (true) altitude, density altitude, and true airspeed.

- The numbers along the outside of the stationary portion are referred to as the OUTER SCALE in this document.
**Scale Values**- The numbers on the outer and inner scales represent multiples of 10 of the values shown.
- EXAMPLE: The number “20” on either scale may represent 0.2, 2.0, 20, 200, or 2,000.

- On both the outer and inner scales you will notice that the number of tick marks, or graduations, vary between numbers.
- EXAMPLES:
- The first tick mark to the right of “10” may represent 10.1, 101, 1,100, etc.
- The first tick mark to the right of “17” may represent 1.72, 17.2, 172, etc.
- The first tick mark to the right of “35” may represent 3.55, 35.5, etc. The second tick mark to the right of “35” may represent 3.6, 36, 360, etc.

- EXAMPLES:
- On the inner scale, minutes may be translated to hours and minutes by reference to the hour scale, which is below and inside the inner scale.
- EXAMPLE: 120 min., or “12” on the inner scale is also 2 hr. as indicated by “2:00” below the “12.”

- On the hour scale, the tick marks represent either 5 min. or 10 min.
- EXAMPLE: Between “1:50” and “2:00” the tick mark represents 5 min. Between “4:00” and “4:30” each tick mark represents 10 min.
- The tick marks on the inner scale can be used to supplement the hour scale.

- The numbers on the outer and inner scales represent multiples of 10 of the values shown.
- The calculator side of the flight computer is constructed so that any relationship, or ratio, between a number on the outer scale and a number on the inner scale will remain constant for all other numbers on both scales.
- Rotate the inner circle so the “10” is opposite the “10” on the outer scale, and note that all the numbers around both circles are identical.
- Next, rotate “20” under “10” on the outer scale; now all numbers on the inner scale are double those on the outer scale.