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

We're starting a new topic now: navigation using the 1 in 60 rule. Let's pick it up from where the rule has already been introduced, because we're going to build on it. So far, you've learned that if you're 4 NM off track after 30 NM, that's a 1 in 60 error, which gives you an 8° track error angle. And you've seen the basic correction: you turn 8° right to parallel the track, then you fly until you're back on track, and then you turn back 8° left. That's the double track error angle method. Now, here's the key insight I want you to grasp. When you do that — turn 16° right, then 8° left — you finish up on a heading that is 8° right of your initial heading. Think about why. Your initial heading took you 8° left of track, which is why you had the track error in the first place. By turning a total of 8° right, once you're back on track, you're now on the heading that, if you had followed it from the start, would never have taken you off track at all. So you continue on that heading for the rest of the leg, or until the wind changes again. But sometimes you don't want to just regain track. Sometimes you want to head directly for the destination, or the next turning point. And there's another situation: if you're more than halfway along the track when you get your first pinpoint, the double track error angle method won't get you 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. As before, after 30 NM along track, you get a pinpoint 4 NM left of track. As before, your track error angle is 8° to the left. Turning 8° right will only parallel the track. We now need to calculate the closing angle to proceed to the turning point. Here's how it works. If you've gone 30 NM along a 78 NM track, there must be 48 NM remaining. You're 4 NM off track in 48 to go. That's 1 in 12, which is 5 in 60. So your closing angle is 5°. So you turn 8° right to parallel the track, and a further 5° right to converge, making a total turn of 13° required. To summarize: the required amount of turn is the sum of the Track Error Angle and the Closing Angle. Now, there's a quicker arithmetical method that gives exactly the same answer, but doesn't require you to calculate the Track Error Angle at all. Only the Closing Angle needs to be established, and it's then multiplied by a factor dependent upon the proportion of your distance along track to the total leg distance. This can be quicker. Let's use the same problem. Track is 78 miles long, after 30 miles along track you're 4 miles left of track. This time, don't bother working out the Track Error Angle. Just consider the Closing Angle. We'll work through that calculation next.