Components of the CR-3 Wind Side

COMPONENTS OF THE CR-3 WIND SIDE

AIRSPEED SCALE

The outer most scale (Figure 4.5-9) represents True Airspeed (TAS) when initially setting

up the problem, but also represents crosswind component values when computing

crab/drift angles.

TRUE AIRSPEED INDEX

This index, located on the second disk (Figure 4.5-9), is where the TAS is applied to the

problem. TAS is required to accurately compute the crab/drift angle.

TRUE COURSE INDEX

The True Course Index is used to input the True Course (TC) in a preflight wind

calculation, or Track (TK) in an in-flight wind calculation (Figure 4.5-9). Remember that

either of these directions can represent the direction of the Ground Vector (Figure 4.5-7

(page 6)).

CRAB AND DRIFT ANGLE SCALE

The numbers on the edge of the middle disc (Figure 4.5-9) are used for either CRAB or

DRIFT angle, depending on the type of problem.

COMPASS ROSE

The Compass Rose is a standard 360 degree scale showing one-degree increments

(Figure 4.5-9). This disk also includes range rings that correspond with the wind scales and

direction lines that originate from the center.

COMPUTER WIND SCALES

There are two wind scales depicted on the horizontal and vertical lines that radiate from the

center of the computer (Figure 4.5-9). These scales are printed in black. The large scale

(which represents speeds from 0 to 80 knots) is used if the wind is less than 60 knots while

the smaller scale (higher speeds, from 0 to 160) is used if the wind is greater than 60

knots. Once a desired scale is chosen, that same scale MUST be used throughout the

entire problem. Care should be taken not to mix the two scales within the same problem.

10% RULE

If the crosswind component is 10% of the True Airspeed, the Crab Angle should be 6

degrees. This is a consistent relationship throughout the range of airspeeds that apply to

tactical aviation. Therefore, as the crosswind component increases the corresponding crab

angle will also.

4.6-115