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Practice Exam

# Crosswind Component

This is a practical method used to mentally calculate crosswind components while airborne. For crosswind & headwind questions in the exam, you should use an accurate navigational computer (CRP-1). See the lesson CRP-1: Calculating Headwind & Crosswind Components to learn how to use the CRP-1 for this.

When the wind is at an angle (other than 90°) to the aircraft’s heading, there will be both a headwind/tailwind component and a crosswind component. We can use something known as the ‘clock code‘ to help with this. Let’s look at an example to explain it:

## Crosswind Component Calculation Example

You are flying on a heading of 090° with a true airspeed (TAS) of 90 knots. The wind is 045/20. What is the strength of the crosswind you are experiencing?

1 Find the angle between the wind and our heading

In this case it is 45°

2 Use the ‘clock code’. Take this number of degrees and think of it as minutes on a clock:

15 is ¼ of an hour, so when the wind is 15° off our heading, the crosswind is ¼ of the wind strength
30 is ½ of an hour, so when the wind is 30° off our heading, the crosswind is ½ of the wind strength
45 is ¾ of an hour, so when the wind is 45° off our heading, the crosswind is ¾ of the wind strength
60 is a full hour, so when the wind is 60° or more off our heading, the crosswind is equal to the full wind strength

3 In this case, the wind strength is 20 knots so the crosswind component is 15 knots

## Drift Angle Calculation Example

Let’s use the same example to see how the clock code can be used to calculate the drift:

You are flying on a heading of 090° with a true airspeed (TAS) of 90 knots. The wind is 045/20. What drift will you experience?

1 Find the angle between the wind and our heading

In this case it is 45°

2 Determine the max drift for this TAS and wind speed (see the previous lesson for more information on this)

3 Use the clock code to determine how much of the max drift needs to be applied

45 is ¾ of an hour, so when the wind is 45° off our heading, the drift is ¾ of the max drift

Max Drift = 13°
Drift Experienced = ¾ of 13° = 10° (approx.)