The distance from 'A' to 'B' measures 120 NM. At a distance of 55 NM from 'A' the pilot realizes a deviation of 7 NM to the right. What approximate course change must be made to reach 'B' directly?
Refer to figures.
Using your Flight/Nav computer, the corrections that must be made to the heading are:
- Degrees to parallel: Align distance off, 7 NM (70) outer scale, with distance travelled, 55 NM inner scale. Above the black arrow (60), read the degrees to parallel: 7.6° (76) on the outer scale.
- Degrees to intercept position B: Align distance off, 7 NM (70) outer scale, with distance to go, 65 NM inner scale. Above the black arrow (60), read the degrees to intercept: 6.4° (64) on outer scale.
Thus, the total heading correction to proceed directly to position B is: 7.6° + 6.4° = 14°. And since the deviation is to the right, the heading correction must be to the left.
An alternative way to calculate the course change to reach B directly based on the 1:60 rule, which states that: "For each degree of track error you will be one NM off-track having travelled 60 NM along track" is:
- Degrees to parallel = (Distance off track x 60) / Miles travelled = (7 NM x 60) / 55 NM = 7.6°.
- Degrees to intercept = (Distance off track x 60) / Miles to go = (7 NM x 60) / (120 NM - 55 NM) = 6.4°.
Thus, the total heading correction to proceed directly to position B is: 7.6° + 6.4° = 14°. And since the deviation is to the right, the heading correction must be to the left.
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