Alexander Burton, CFI

Pacific Rim Aviation Academy Inc.

Pitt Meadows Regional Airport

393-11465 Baynes Road

Pitt Meadows, BC V3Y 2B4

- John Dryden-

I like to tell students the best way to avoid getting lost is to stay found.

It sounds simple enough; it just sort of rolls off the tongue, but “staying found” does take

a certain amount of situational awareness and a continual effort to pay attention. We

normally know where we are when we take off. We normally know where we are headed

on any particular flight. The trick is to get from here to there without the inconvenience

of becoming disoriented and “lost”.

Lost, of course, is relative term. We are never totally lost; we may just not know our

precise location. In VFR flight in small aircraft, it’s pretty hard to become confused about

which hemisphere we are in or which country or even which province. If we find

ourselves unsure of our exact position, we more than likely have a pretty good idea of

where we were not long before, if, of course, we have been paying attention. VFR cross

country flight is, after all, conducted with reference to the ground: point to point along a

given track.

One of the skills that can be very helpful in the process of staying found is using Lines of

Position from identifiable references either visual or electronic. The principles are the

same; we just use different equipment.

For visual reference, we make use of our eyes, our heading indicator or compass, and a

chart. For electronic reference, we make use of radio navigational aids. Even if we are

equipped with sophisticated navigational aids, it is an excellent plan to keep track of our

position on a chart as we fly so we are not risking disorientation in the event of a

navigational aid failure.

Learning to develop a Line of Position is an excellent practice and can be very helpful

while enroute to assist us in pinpointing our position. Whether we do this visually or with

reference of a navigational aid, the same principles apply. We want to determine where

we are in relation to one or more fixed points.

We’ll leave GPS aside for the moment. If the device is working properly, it will give us

our exact position immediately—by establishing several Lines of Position from

satellites—and provide us with a direct track from our position to wherever else we might

want to go.

Using more conventional navigation aids, VOR or ADF, is simple and quick, so let’s start

there. If you are planning to or considering using your navigational aids during a flight, it

is an excellent idea to make sure you know how to operate them and to perform the

appropriate checks on the ground prior to takeoff to make sure they are functioning

properly.

To establish a Line of Position with VOR, tune in the appropriate frequency, perform the

identification procedure using the Morse Code identifier indicated next to the station on

the chart and turn the omni bearing selector (OBS) which turns the azimuth dial until you

see a “From” flag and the course deviation indicator (CDI) is centred. At the top of the

azimuth dial, you will find the degree number of the radial over which you are currently

flying, the track outbound from the station.

On your map, draw a line extending outward FROM the station along the radial indicated

at the top of your azimuth dial. You are somewhere along that line. You have established

a Line of Position. If there is a handy geographic feature, for example a road, river, power

line, coastline, or railroad track nearby, you can find yourself quite accurately by

reference to the point where your Line of Position crosses that geographic feature. Ideally

the Line of Position and the feature will lie ninety degrees to one another.

Using the ADF is a similar process and, since ADF is not dependent on line of sight

reception, you may have more flexibility in available stations. There are some accuracy

issues involved with the ADF-NDB system and it might be wise to be aware of those.

However, for our purposes we can normally obtain sufficient accuracy to achieve our

goal of establishing a workable Line of Position.

With a fixed card ADF, tune, identify, and test the equipment to make sure all is working

properly, observe your relative bearing—oh dear—take the reciprocal of that bearing,

draw your Line of Position FROM the station, and carry on as you would with the VOR.

Don’t get too excited about the fancy terminology. If the head of the needle points thirty

degrees to the right, the tail of the needle will point 150 degrees to the left of your current

heading (relative bearing 210 degrees). Remember, the fixed card ADF dial always uses

“0” as the direction your aircraft is flying. Simply transfer that 150 degrees left indicated

by the tail of the needle to your heading indicator. If the head of the needle indicates a

relative bearing of 30 degrees, the bearing FROM the station is 150 degrees to the left of

your current heading.

If the head of the needle is to the left, the tail will be to the right. Keep it simple.

Using the tail of the needle automatically gives us the reciprocal of the bearing TO the

station and allows us to determine the Line of Position without a lot of complex

computation. We may already be under some level of stress if we are unsure of our

position. There is no sense adding to our difficulties with a math problem. Practicing this

procedure on the ground or in your local area when you know exactly where you are is an

excellent plan. Then, when you need it, it will be second nature.

Of course, two NDBs, two VORs or an NDB and a VOR can be used together to develop

two Lines of Position, or more if we really want to be precise, which will locate or “fix”

our position fairly precisely. Typically, when using three or more stations, we will end up

with a small triangle rather than a single point of intersection. We are located within that

triangle (1). We’ll talk about fixes in more detail next month.

We can apply the same principle visually, also with excellent results, and we don’t need a

navigational beacon handy to do it.

Sailors who have done some coastal cruising will be familiar with this technique. On a

boat, mariners typically will make use of a pelorus which provides a relative bearing

similar to a fixed card ADF or an azimuth compass which provides a magnetic bearing.

At sea, out of sight of land, a sextant, and before that an octant and before that a quadrant

served the same purpose: to establish a Line of Position from the sun, the moon or a star.

My father's generation, with the help of a few simple calculations and a table of

corrections, navigated aircraft across the Atlantic to Europe using a sextant .We don’t

normally carry any of these instruments with us in an aircraft, but we can perform

essentially the same function using our chart, our eyes, and a little imagination.

Orient your chart so what you are seeing outside is the same as what you are seeing

inside: look straight ahead and match the chart to the direction of flight. Find some

identifiable reference point within visual range: a lake, a bridge, a mountain peak, an

island. Almost any point will do as long as we can see it outside and find it on our chart

inside.

What is the relative bearing FROM your aircraft to the geographic reference? Is it left or

right? You can use a compass rose, if one is handy on the chart, or you can simply make

a reasonable estimate using the clock method referencing the aircraft’s nose as 12:00

o’clock: 1:00 o’clock is 30 degrees; 10:00 o’clock is 300 degrees; 15:30 is 105 degrees

(3.5 x 30 = 105) (2).

You can translate that into its reciprocal by laying a pencil or your hand on the map and

drawing a line outwards FROM the reference point on the correct bearing. You have

established a Line of Position.

If you can locate yourself within a couple of miles, all the rest should fall into place quite

nicely. Why not? It isn’t rocket science. People have been using this type of navigational

technique quite successfully for more than 3000 years.

Playing with and practicing the techniques of developing Lines of Position both visually

and electronically in a safe and known environment will enable you to make use of these

techniques when venturing into unfamiliar areas. Having a few extra tricks up your sleeve

is all to the good, and it’s pretty cool to learn something new.

Enjoy.

Notes:

1. Ideally, the angle of interception between Lines of Position extending from reference points will equal

90 degrees. If the reference points are too close together, or, for that matter, too far apart, the angle of

interception formed by the Lines of Position will be too steep (acute) or too shallow (oblique) to

determine an accurate “fix” or position. You can easily draw some triangles and see the problem. As the

reference points get closer or farther apart the inevitable error in the bearing of your Lines of Position is

magnified.

2. Time times 30 equals True bearing: 2 o’clock times 30 = 60 degrees True; 10 o’clock times 30 = 300

degrees True. Or, we can use our relative bearing and add that to our indicated heading on the HI, giving

a magnetic bearing to or from a reference point. It’s probably easier to just work with True bearings on

the chart rather than worry about translating True to Magnetic and back again. The idea is to find our

location not necessarily to establish a particular heading to fly. Once we have established our location,

we can make decisions about headings.