Components of the CR-3 Wind Side

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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

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