Advanced

Chapter 18.23

Wind Corrections

If the wind is known, the wind correction can be calculated and a WCA (Wind Correction Angle) can be flown at which the QDR, QDM or Deviation Bar no longer moves.

Wind Corrections

With a speed range of 115kts ±5kts (TAS), the following rule of thumb for wind corrections has proven effective:

The 180° sector to the left or right of the desired track is divided into sectors of 30°. Now determine from which sector the wind is blowing and assume 1 to 3 thirds headwind or tailwind or crosswind according to the graphic. It is special that the sum of the wind components is 4/3.

Wind Corrections: Example 1

Example 1:

QDM 090°, Wind 020/30kts
Headwind component:
Crosswind component:

1/3 of 30 kts = 10 kts
3/3 of 30 kts = 30 kts from the left

Based on the crosswind component, the WCA can now be calculated using the rule of thumb mentioned above, which applies to speeds of 115kts ±5 kts:

The WCA must be added or subtracted to the QDM in the direction of the wind.
Thus, for the above example: WCA = 30 kts / 2 = 15°.
Wind corrected HDG to stay on the QDM = 075°.

Wind Corrections: Example 2

Example 2:

QDR 245°, Wind 295/15kts
Headwind component:
Crosswind component:

2/3 of 15 kts = 10 kts
2/3 of 15 kts = 10 kts from the right

Based on the crosswind component, the WCA can now be calculated using the rule of thumb mentioned above, which applies to speeds of 115kts ±5 kts:

The WCA must be added or subtracted to the QDR in the direction of the wind.
Thus, for the above example: WCA = 10 kts / 2 = 5°.
Wind corrected HDG to stay on the QDR = 250°.

Wind Corrections

With modern navigation displays, the wind and the ground track are usually displayed. In these cases, the ground track is used for navigation instead of the heading and therefore does not need to be corrected for wind.

Interception Inbound

If a radionavigation station is to be approached at a certain angle (primarily for IFR), the following procedure is used. Due to the meanwhile sparse distribution of NDBs, only the procedure for VOR is described in the following.

Example:

Starting from the current position, you are to intercept the radial 080°. You will receive the following instruction from the air traffic controller: Intercept and follow Radial 080 inbound to the VOR.

The following steps explain how to identify and perform the correct interception procedure.

Interception Inbound

Step 1: ACTUAL RADIAL

Determine the current radial and name it with an approximate cardinal direction. (e.g. ACTUAL RADIAL 040, NE of the station).

Rotate the OBS until the Course Devaition Bar is centred and you have a FROM reading. Now you can read the current RADIAL 040° on the VOR.

Interception Inbound

Step 2: Requested Radial

Determine the requested radial and name it with an approximate cardinal direction. (e.g. REQUESTED RADIAL 080, E of the Station).

In our example, you have received the Requested Radial from the air traffic controller. This may also result from an approach procedure or you may have determined it yourself.

Interception Inbound

Step 3: Difference

Determine the difference between the actual radial and the requested radial and from this determine the PROCEDURE to be applied.

With a difference ≤10°:
Analogous to the correction procedure (chapter 18.22.3)

With a difference >10° to ≤30°:
45°-Interception

With a difference >30° to ≤70°:
90°/45°-Interception

With a difference >70°:
First homing, then special IFR procedure

Our difference is between >30° and ≤70°. Thus, a 90°/45° interception is performed.

Interception Inbound

Step 4: INTERCEPT HEADING

Determine the intercept heading:

With a difference ≤10°:
Correct your heading with twice the deviation in the direction of the COURSE DEVIATION BAR until it is centred again analogous to the correction procedure (chapter 18.22.3).

Interception Inbound

Step 4: INTERCEPT HEADING

Determine the intercept heading:

With a difference >10° to ≤30°:
45° Interception: Set the requested radial +180° with the Course Selector.

The intercept HDG is calculated from the requested radial +180° ±45° in the direction of the COURSE DEVIATION BAR on the side of the TO display.

Interception Inbound

Step 4: INTERCEPT HEADING

Determine the intercept heading:

With a difference >30° to ≤70°:
90°/45° Interception: Set the requested radial +180° with the Course Selector.

The initial intercept HDG is calculated from the requested radial +180° ±90° in the direction of the COURSE DEVIATION BAR.

Interception Inbound

Step 4: INTERCEPT HEADING

Determine the intercept heading:

With a difference >70°:
First perform a homing according to 18.22.2, then a special IFR procedure.

Interception Inbound

Step 5: FIRST TURN

With a difference ≤10°:
Turn initial away from the station (unless the difference between the ACTUAL HEADING and the INTERCEPT HEADING is less than 50°).

Example: actual HDG 360°; RIGHT TURN.

Interception Inbound

Step 5: FIRST TURN

With a difference >10° to ≤30°:
Turn initial away from the station (unless the difference between the ACTUAL HEADING and the INTERCEPT HEADING is less than 50°).

Example: actual HDG 360°; RIGHT TURN.

Interception Inbound

Step 5: FIRST TURN

With a difference >30° to ≤70°:
Turn initial away from the station (unless the difference between the ACTUAL HEADING and the INTERCEPT HEADING is less than 50°).

Example: actual HDG 360°; RIGHT TURN.

Interception Inbound

Step 6: Follow-up procedure for 90°/45° interception

Difference between >30° and ≤70°:
Initially, an interception angle of 90° is flown. In the example, the interception heading is 170°.

As soon as the deviation bar (approx. 20° before the REQUESTED RADIAL) moves, turn directly to the 45° interception heading, in the example to 215°.

To determine when you are 20° before the Selected Course, you can use a second VOR or you can first set the radial on the primary VOR which is 20° before the REQUESTED RADIAL.