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A typical device in the cockpit will
have a red PULL UP light and an
amber BELOW G/S light within
your field of vision (pushing the
PULL UP light tests the system and
illuminates all the lights). An INOP
light will come on if the system fails
or it loses a source of input. For
non-standard flap settings, there is a
FLAP OVRD (override) switch.
ELT
The Emergency Locator Transmitter
operates on 121.5 MHz, the VHF
International Distress Frequency for
aviation (the UHF one is 243 MHz).
ELTs are supposed to come on
automatically in a crash, or large
impact, and they generally do on
fixed wing aircraft, assuming the
batteries are kept up to scratch and
they are checked regularly, but, with
helicopters, there are fewer
guarantees that this will happen. For
a start, there's a lot more vibration,
and there are less places to attach
them, as they should be fitted as far
aft as possible, aligned fore-and-aft
so the shock forces activate the G
switch properly. Where it's fitted in
the cabin, it's often switched off so it
doesn't get kicked or bashed and set
off accidentally, which is why it's a
good idea to include switching the
thing on as part of your emergency
checklist on the way down.
Refer to the Aviation Law chapter.
MLS
The Microwave Landing System uses a
time referenced scanning beam with
differential phase shift keying to provide
guidance for 3D positioning on
approaches that can be curved with
varying glide paths, especially useful
in mountainous areas. It suffers less
from interference than ILS, and has
more channels available.
Information can be displayed in the
cockpit through normal instruments
or multipurpose displays.
306 Canadian Professional Pilot Studies
The identification is a four-letter
code beginning with M, transmitted
in Morse at least 6 times a minute.
The azimuth station is broadly
equivalent to the ILS localiser, but
does a lot more, transmitting over
200 channels between 5031-5090
MHz. The elevation station uses the
same frequencies. The Precision DME
is similar to the normal type, but
works between 962-1105 MHz on a
paired frequency system, and is more
accurate (down to 100 feet).
Approach signal accuracy is ± 40°
either side of the centreline to at
least 20 nm and 20,000 feet (15°
above the horizontal in elevation).
The back azimuth at the other end of
the runway, on the other hand, is
±20° to 5 nm and 5,000 feet, and is
used for missed approaches, etc.
Radio Procedures
Like aircraft, pilots need radio
licences in order to use the airwaves.
This is normally a separate licence,
which needs you to pass an exam
before it is granted. Although your
use of the airwaves is limited (it's a
subset of the amateur radio
regulations), you still need to know
the phraseology so that other people
don't suffer.
Due to licence restrictions, aircraft
equipment is meant to have as few
controls as possible, including
displays, so some frequencies may
not be completely shown (122.075,
for example, comes up as 122.07).
The Squelch quietens down the
output when no signal is being
received, so you don't get
continuous earfuls of white noise. A
signal coming in cancels this and
activates the audio (a variable
squelch merely determines the signal
level when this occurs). The correct
procedure with the Squelch control,
therefore is to rotate the knob until
the hiss just stops, and leave it there,
although it is true to say that this will
hide a weak signal, so lifting the
squelch may help in this case.
Although the phraseology can be a
bit longwinded (day-se-mal for
decimal, for example), and you may
feel a bit stupid pronouncing some
of the words, remember they are
that way to reduce ambiguity.
Naturally, a continuous listening
watch should be maintained at all
times, as a matter of airmanship, but
especially when transiting controlled
airspace during notified hours of
watch. You must report your
position and height on entering and
just before leaving an ATZ.
There are one or two other points
about radios that aren't often taught
properly during training. The first is
to wait a split second to speak after
pressing the transmit button, which
gives all the relays in the system a
chance to switch over so your
message can get through in full, that
is, not clipping the first bit.
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