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need of immediate assistance (like
when your a single engine fails), you
can use the letters SOS in Morse
Code (… --- …), or the spoken
words MAYDAY, repeated 3 times,
followed by relevant details, like your
position. You can also fire rockets or
red lights at short intervals, together
with parachute flares.
If and when the threat is over, the
Distress call must be cancelled by
notification on ALL frequencies on
which the original message was sent.
To cancel a MAYDAY:
· State MAYDAY once
· Say ALL STATIONS x 3
· Aircraft ID
· Station called
· Time
· Name of station in distress
· DISTRESS TRAFFIC
ENDED
· Station called
· OUT
Urgency
The Urgency call (or "PANPAN")
spoken three times, indicates a very
urgent message concerning the
safety of a ship, aircraft or other
vehicle, or of some person on board
or in sight. If you just wish to
mention you are compelled to land,
but don’t need help right away,
switch the landing lights and/or
navigation lights on and off in an
irregular pattern.
Some Questions
1. Why does attenuation occur?
2. As frequency increases, does the
dead space become larger or smaller?
What happens to the skip distance?
Some Answers
1. The circumference of the wave
front increases, the Earth's surface
absorbs some of the energy, and so
does the ionosphere.
2. It gets larger. The skip distance
increases.
Navigation
Navigation involves taking an
aircraft from place to place without
reference to the ground, except,
perhaps, for checking you’ve got the
right destination! To do this, a
system called Dead Reckoning is used,
which is actually short for Deduced
Reckoning, based on solving a triangle
of velocities, discussed below.
First, however, we need to get
acquainted with the Earth, which is
not actually round, but flatter at the
Poles than at the equator. For our
purposes, though, and the
mathematical models inside the
average GPS, it is a sphere
(technically, an oblate spheroid).
To help find your position, a series
lines is drawn from Pole to Pole
through the Equator, called lines of
longitude. They may also be called
meridians, when split in half, and by
convention are drawn for every
degree you go round the Equator.
Also, by convention, they start at
Greenwich, in London, England
(with the Prime Meridian at 0°), and
are calculated to 180° East or West:
The opposite side to any meridian is
its anti-meridian. (Technically, the
longitude of any point is the smaller
arc of the Equator between the
Prime Meridian and the one passing
through the point).
Since the Earth takes 24 hours to
spin on its axis, 15 lines of longitude
represent 1 hour, and it is noon
when the Sun is overhead any
particular meridian. The spinning is
anticlockwise when viewed from the
top of the Earth, so the Sun will
appear to rise from the East and set
in the West.
Having only one vertical line,
however, is not enough, since you
310 Canadian Professional Pilot Studies
could be anywhere on it, so more
imaginary horizontal lines are drawn,
parallel to each other, North and
South of the Equator, up to 90° each
way, called lines of latitude. Now you
can get lost more accurately! The
latitude of any point is the arc of the
meridian between the Equator and
the parallel through the point:
Latitude lines are always parallel to
each other, whereas longitude lines
(meridians) converge. They are also
fixable by natural means - the Sun,
Moon and planets pass over the
Equator, for example, and the
tropics of Cancer and Capricorn
represent the limits of the Sun's
travel North and South as it rises
and sets every day (it sets further
South each day, until, on December
21st, it stops for three days to go
North again. On June 21st, it stops
going North to go South).
Ptolemy had plotted some sort of lat
& long system by 150 AD, but he
used the Canaries for the Prime
Meridian, which has also been at the
Azores, Cape Verdi, Rome and Paris,
to mention but a few (it wouldn't
surprise me to learn the Ancient
Egyptians used the pyramids).
Eventually, it was placed in
Greenwich, because King George
was a keen astronomer.
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