When planning to fly, we know our start point and our intended destination, so it should be a simple matter to draw a straight line on the map which joins these points and then fly along it.
However, several factors can make such a simple straight line less than ideal. It may not pass over many obvious features which could be used for fix points. It may pass over areas over which we do not wish to fly (large built up areas or inhospitable terrain. For example: It may pass through, or very close to, controlled or restricted airspace, and weather phenomena such as low cloud over hills may cause problems on the direct route. Finally, we may want interesting views while flying. The planned route should be a compromise between two considerations. We want to minimize the distance flown (therefore time, and fuel used), but we also need to minimize the effort required for navigation.
The altitude we plan to fly is important. In general, in a single-engined aircraft, we should always be able to select and glide to a safe landing area if we have engine problems. That usually means that the legal minima of 500 feet away from possible
human activity or 1000 feet above the smallest built up ‘congested’ areas (for those of us who may fly over them) are unlikely to be sufficient. How much height above ground do you need for a forced landing pattern? We might consider an altitude which gives at least 2000 feet clearance above most of the ground and 1500 feet above any particularly high points to be adequate.
A clear plastic ruler placed on the map between our start point and destination, as if we were about to draw a straight line, allows us to make some initial assessments.We can see the ground elevations in the general area and choose a suitable cruising
altitude. We can then look along the ruler’s edge at the direct route.
Does this cross or pass close to (we cannot guarantee that we shall follow our track exactly) controlled or restricted area boundaries, aerodrome traffic zones, parachuting or gliding sites or other airfields? If so, can we fly over, under or through these areas at our planned altitude? Is there a safe margin for error? If not, we should split the route into sections or “legs” with one or more turning points between them. We should choose an obvious fix point as the turning point and study each leg individually.
Does the direct route take us over areas where it would be difficult to land in an emergency (for example a large unbroken stretch of woodland)? Again we may need to choose one or more turning points before selecting the actual route we plan to fly.
Route planning can be done well in advance of the actual flight, when wind direction and runways in use are unknown. Although it is perhaps easy to plan to fly from one aerodrome “overhead” to another, accurate navigation would require us to climb to
cruising altitude (following the circuit pattern as we climb) then set heading from that overhead. To reduce time and fuel, we may wish to choose a suitable fix point in the general direction of our first track which we can see (and keep in sight) while climbing from whichever runway is in use at the time, and start navigation proper from there.
Place the ruler between this start point to either the first turning point or the destination overhead (a standard join is always advisable at a new aerodrome, but follow whatever procedure is published). The line of the ruler is the intended track. Look along the track and note whether suitable fix points are available at around 6 minute intervals (ideally dividing the track into halves, thirds or quarters). If not, consider changing the previously selected turning points or insert an additional one to make things easier.
Once detailed planning is complete on the day, place small marks along the legs at intervals of one or two minutes flying time from the start of each leg. Calculate the heading and time you expect to take from take-off to your start point, because many
pilots have mis-identified that point. Calculate the headings and times from the previous turn you expect to arrive over each fix point, and write these down (but do not be too exact – the nearest half minute is usually accurate enough). Also calculate
timings to the boundaries of any controlled airspace you intend to fly through.
The essentials for safe navigation are a map, a compass, and a clock. However, some form of written plan is also needed to assist in calculations and to record them for use in the future (most trips are initially planned several days in advance). It is
used to record information which you might need during the flight, such as radio frequencies, and to record any important information received during the flight, such as an air traffic clearance. It is also useful to keep a record of what actually happened in
flight, especially if you change your original plan, or become unsure of your position.
The navigation log shown at the figure contains all the essential information as well as many other useful items, but many other versions are available. Items such as leg tracks, distances, safe and planned altitudes, TAS, magnetic variation and fuel consumption can be measured or calculated and listed on the log.
Pilots can use one line for each leg, but one line for each fix point allows easier reference in flight. Other information such as radio frequencies and navigation aid details can also be included well in advance of the flight, as can the altimeter setting
regions whose pressure settings may be used.
On the day of the flight, the winds and other weather information can be written down and used to calculate the IAS and headings required, and also the groundspeeds, which can in turn be used to find times and fuel used. Before take-off, we can copy
down any airfield information and departure clearance onto the log, and also the
regional pressure settings.
In flight, we can refer to the log before and after each of our turning points, and when amending headings and ETAs. We can also log the actual times at turning points and fixes, as well as any allocated transponder codes and radio frequencies. Any radio aid
position lines or fixes can also be recorded.
LOG ON CHART
Although some form of navigation log is important, many pilots choose to write much of the information contained in it on the map itself to reduce cockpit clutter, especially important in an open cockpit. A soft pencil is ideal for writing on paper charts, but if
the chart is laminated with clear plastic, grease pencils (sharp ones) or special pens are required.
At the start of each leg, you may wish to write all the information needed for the routine checks you will carry out. A box containing the information, and a reminder to start the clock, may be placed alongside the track itself at sufficient distance to allow all
necessary map features to be read. In-flight information can be written on the chart as it happens or is passed to the pilot,
but the map becomes cluttered and the information difficult to decipher. You might prefer to use a log form in flight for recording information, even if you duplicate the planning information on the map.