Navigation Using the 1 in 60 Rule — Page 208, Lesson 183

I want to walk you through the 1 in 60 rule and how we apply it when navigating. We've already seen the basic idea: if you're 4 nautical miles off track after 30 nautical miles, that's a 1 in 60 ratio — 4 in 30 is the same as 8 in 60 — so your track error angle is 8 degrees. You turn 8 degrees toward track to parallel it, then later turn back the same amount to stay on track. Let me recap that scenario so the new material makes sense. In Figure 11.8, we had a pinpoint showing we were 4 NM left of track after 30 NM. We turned 16 degrees right — that's the double track error angle method — to regain track. Once back on track, we turned 8 degrees left. That leaves us on a heading 8 degrees right of our initial heading. Notice: our initial heading had us 8 degrees left of track, which caused the original track error. By turning a net 8 degrees right, we're now on the heading that, if we'd flown it from the start, would never have taken us off track. So we continue on that heading for the rest of the leg, unless the wind changes again. Now, sometimes we don't want to just regain the original track line. We might want to head directly for the destination or the next turning point. Also, if we're more than halfway along the leg when we get our pinpoint, the double track error angle method won't get us back on track before the next turning point. In those cases, we use a combination of the Track Error Angle and the Closing Angle. Let me set up the situation. Your total track distance is 78 NM. After 30 NM along track, you get a pinpoint 4 NM left of track. As before, your track error angle is 8 degrees to the left. Turning 8 degrees right will only parallel the track — it won't converge toward your destination. We now need to calculate the closing angle to proceed directly to the turning point. Here's how it works. We've gone 30 NM along a 78 NM track, so there are 48 NM remaining. We are 4 NM off track with 48 NM to go. That's 4 in 48, which simplifies to 1 in 12. To express that in 60, 1 in 12 is the same as 5 in 60. Therefore, our closing angle is 5 degrees. So, we turn 8 degrees right to parallel the track, and then a further 5 degrees right to converge toward the destination. That makes a total turn of 13 degrees required. To summarize: the required amount of turn is the sum of the Track Error Angle and the Closing Angle. There's also a quicker arithmetical method that gives exactly the same answer without requiring you to calculate the Track Error Angle separately. You only need to establish the Closing Angle, then multiply it by a factor dependent on the proportion of your distance along track to the total leg distance. Let's use the same problem: a track 78 miles long, after 30 miles along track you're 4 miles left of track. This time, don't work out the Track Error Angle — just consider the Closing Angle. Figure 11.11 shows this: you have the 30 NM you've flown, the 48 NM remaining, and the 4 NM off-track distance. The closing angle is still 5 degrees, as we calculated. The factor comes from the ratio of distance gone to total distance, and multiplying the closing angle by that factor gives you the total correction directly. But the key takeaway is that whether you do it in two steps or one, the total turn needed is the sum of the track error angle and the closing angle.