6.38 In-flight Revisions

During a cross-country flight, the aircraft may not remain exactly on the planned track, or the actual ground speed may differ from that planned.

In-flight revisions are quick mental calculations used to correct the aircraft back onto track and revise the navigation plan, including heading, ground speed and ETA, while airborne.

6.38.2 Estimate:

(a) a heading change, using the 1:60 rule (± 2º);

The 1 in 60 rule provides a quick mental method of estimating the heading change required to regain the planned track.

For this exercise, plan to regain track over the same distance as has already been flown.

First estimate the Track Error (TE):

TE = 60 ÷ Distance Gone x Distance Off Track

Then double the Track Error to obtain the Total Heading Correction:

Total Heading Correction = TE × 2

The first part of the correction allows for the Track Error, and the second part provides the Closing Angle required to regain track.