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indications should therefore not be
relied upon.
282 Canadian Professional Pilot Studies
Inside your aircraft will be a large
black box, with a remote indicator in
the cockpit:
Once you select a radial by turning
the Omni Bearing Selector (the small
knob just under the dial), the Course
Deviation Indicator needle will be in
the centre, or either side of the
centreline, up to 10° away from the
radial, so each dot left or right
represents 2°, if there are 4 dots on
your display (2 ½ ° if there are 3).
When in the middle, you will be on
the radial, which traditionally is from
the station when on the same side,
shown by To/From Flag, which, on
later instruments, will be a small
white triangle pointing in the
relevant direction. If the indicator
shows To, you are on the reciprocal, or
on the other side (in the above
example, the radial is N, or 360°,
because the To flag is showing).
This is a common trap in exam
questions – if you are tracking
inbound on a radial, remember to set
the reciprocal at the top of the display,
since radials go from the station.
All you have to do then is watch the
needle – if you are going away from
a station on a radial, and the needle
is pointing left, then you fly left until
it centres:
If you are going to the station, then
you fly right. The thing to remember
is that the needle always points to where
the radial is, which is nothing to do with
the heading of the aircraft (remember
this for exams). All you do is follow
the needle (when coming down the
ILS, you follow the cross formed by
the localiser and glideslope needles).
In short, the radial is where the
needle is, and you do not necessarily
turn that way to get to it -
sometimes, having the needle on the
left means turn right! Only if your
heading is the same direction as the
OBS will it be on the correct side.
For any radial, there are boundaries
formed by the CDI and the
To/From indicator, forming
quadrants around the station (that is,
there are four distinct areas). You
will be in one of them.
Common routes between stations
may use a shared radial which may
Electricity & Radio 283
be identified with a Victor number if
used as an airway, such as V-24.
You can therefore take the
indications from two VOR stations,
draw the lines of position (i.e. bearings)
from the compass roses and the
intersection point is your position:
Remember to ensure that the CDI is
centred in both cases and the FROM
flags are showing.
If you have to use another VOR to
provide a fix as a reporting point
along the airway, select the required
radial, and when the needle is
centred you are over the fix:
In the exam, you will need to
determine whether you have passed
it or not. In this case, the needle will
be to the left of the station is on the
left, and vice versa if you are not there
yet, assuming your heading is the
same as the OBS. Otherwise, the
needle will point the opposite way if
you have already gone past (oops!).
When tracking along an airway, tune
and identify the station you are going
from, track the selected radial until
near the mid-point, then tune and
identify the next station. The
To/From flag should change over.
To intercept an inbound radial, tune
and identify the VOR station, select
the reciprocal of the desired radial,
by turning the OBS until you get a
TO reading. Fly to whichever side
the needle is displaced, turning the
shortest way to a heading 90° away
from it, until the needle starts to
move, at which point reduce the
intercept angle to 45°:
As the needle centres, reduce the
intercept angle again and maintain
the track with suitable adjustments
for drift.
284 Canadian Professional Pilot Studies
Do the same outbound, except look
for a FROM reading.
A good rule (inbound and
outbound) is to subtract the
intercept angle if the needle goes
left, and add if it goes right to find
the heading to steer. For example,
280°-90°=190°. To bracket for drift,
turn onto a zero wind heading and
see what the drift actually is. Get
back on track, make a large
correction the opposite way and see
what happens. Get back on track
and half the original correction.
Keep doing this until the correct
heading is found.
Range
The (theoretical) VOR reception
range can be estimated with this
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