Pooley’s CRP-5 Techniques

Finding the Track and Groundspeed

Example 1: Given: TAS = 205 kt, HDG (T) = 180°, W/V = 240/25kt.  Calculate the drift and GS?

Step 1: place the centre dot over TAS “205”;

Step 2: rotate wind direction “240°” under true index.

Step 3: make a wind mark on the centre line 25kt below (180kt) centre dot.

Step 4: rotate the heading “205” under the true index.

The marker now indicates a ground speed of 194kt and a drift of 6°L

Richting in navigatie wordt gemeten als een hoek ten opzichte van een referentiepunt.

Heading, Track and Drift

The heading of an aircraft is the direction the airplane’s nose is pointing, measured as an angle from the north (T, M or C).

The track is the aircraft’s path over the ground, of which we distinguish two:

• Required track, the track we wish to follow;
• Track made good, the actual track;

Track Error (TKE), is the angle between the required track and the track made good.

Drift, is the angle between the aircraft heading and the track made good (actual).

Drift is expressed as to the left (port) or to the right (starboard). Where, important to remember, drift goes from heading to track (air to actual).

Drift goes from heading to track (air to actual).

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Wind Correction Angle

If there is wind hitting the airplane, let’s say, from the left, and we don’t compensate for it, then it will push (drift) the plane to the right. So with the same heading, the actual track will be drifted to the right of the required track.

In order to maintain the required track, we have to compensate for the wind, by pointing the noise of the plane slightly into the wind. Actually, by the same angle as the drift would have been, but in opposite direction. This what is called the Wind Correction Angle (WCA).

So the WCA applied to the required track, gives the required heading to be flown. For example: