By Adrian Rosevear 

Last month I introduced a series of articles discussing the basics of visual navigation and I touched on the concept of accurate flying and how important it is for successful navigation.

This article will discuss a concept that the student pilot would be well served to think before heading off on their first navigation flight. What I would like you to do is consider how you read your map and relate it to what you see on the ground. Here, I am referring to the workcycle ‘clock, map, ground’. It’s the order in which these things are done that is important.

Consider the lead up to a check point on your map (let’s say a large town), which has been pre-planned to be no more than 20 minutes since your last check or turn point. There are basically two ways of finding the town. The first method: you look out the front or side window for a town to appear under the nose and when one appears near the expected time, assume it to be your checkpoint. While this may work, it is surprising how many towns are out there and, more importantly, how many towns look alike from 8000 feet. Using this method, the pilot can easily find a town on the ground then, referring to the map, assume it is the town of the check point. I have often seen features mistaken in this way by students and it is easy to do. The other danger with this ‘ground then map’ method is that you do not refer to the clock or, if you do, it is after you have convinced yourself the town on the ground is the one on the map. Get lost using this method and there is no way to backtrack through your log to work out where you went wrong.

The second (and correct) method brings in a constant - time. While navigating visually, work on a 10 – 15 minute cycle. 15 minutes after your last check point, begin to prepare for the next event planned approximately 20 minutes from the last event. Here, look first at the clock: 15 minutes have elapsed, and at a (given) 120 knots ground speed the aircraft has travelled 30 nm. Then look at the map and find where you are (note, we have not yet looked at the ground) purely by heading, time and speed. At this point, identify the prominent check point features on the map working big to small and then, look out the window and identify these prominent features on the ground. Clock, map then ground. In this way the chances of misidentifying a feature on the ground and ‘reading the map to make that feature fit’ is less likely to occur.

An important aspect of using the clock, map, ground workcycle are the features you select for turn and check points. In military pilot training the emphasis is on natural features such as mountains, coastlines, ridge lines, lakes and rivers. Man-made features are used, but usually only when fine tuning your position with reference to the large natural features. In this way the ‘big to small’ technique is taught. Here, your aircraft’s position is worked out firstly from reference to large features, such as ‘south of the large mountain range’ and then smaller ‘north of the river mouth’ until you have reduced your focus to small features such as ‘overhead the road intersection’. Use clock, map, ground. For example, looking at the map I see that at 15 minutes elapsed I need to be south of a large mountain range and four miles north of the river mouth. I then look out the window towards where I expect to see the mountain range and the river and find them on the ground. Instantly I know I am in the general area. I then return to the map and use smaller features to pin point my position.

By using time I know where on the map I should be and can reference with confidence what I see out of the window. Next month I will discuss the navigation workcycle in more detail.