Flight Training - March/April 2024 - 16

PERSPECTIVES FLIGHT LESSON
PREFLIGHT HOW IT WORKS
BY DENNIS K JOHNSON
BY JILL W. TALLMAN
INSTRUMENT LANDING SYSTEM
RADIO SIGNALS TO GUIDE YOU HOME
INSTRUMENT LANDING SYSTEMS ENABLE
pilots to make safe landings in both visual
and instrument meteorological conditions.
You'll find them at airports with
ILS instrument approaches. There are at
least two components to the system. They
operate independently but in tandem to
provide pilots with lateral and vertical
precision guidance to a runway. Proceeding
to an airport to perform what's known
as an ILS approach, the pilot tunes in the
correct radio frequency on an airplane's
navigational radio to pick up that guidance
in the form of radio signals. An ILS
may also include high-intensity lighting
arrays to help the pilot spy the runway
when in instrument conditions.
The first component, the glideslope,
resembles a cellphone tower and is stationed
close to the approach end of the
runway near any visual approach slope
indicator lights. The glideslope transmits
a UHF signal to the aircraft modulated
by signals on two frequencies: 90 Hz and
150 Hz.
The frequencies overlap at the
proper glideslope, so when an airplane is
descending and its glideslope receiver is
picking up those frequencies, they will be
translated into vertical guidance displayed
on a VOR receiver whose horizontal needle
rises or falls to show you where you
are in relationship to the glideslope.
Lateral guidance is provided via a
localizer, located at the opposite end of
the runway and resembling a cluster of
TV broadcast antennas on their sides.
Similar to the glideslope, a the localizer
sends a VHF signal and modulating 90-Hz
and 150-Hz signals at the approaching
airplane. Where the signals intersect is
the course that will guide the airplane
down the centerline of the runway. The
airplane's receiver translates those signals
to show the pilot where the airplane is in
relationship to the course. Drift too far to
the right, and the needle on the localizer
will swing to the left-telling the pilot to
adjust course to the left.
VFR pilots can use an ILS too-not
in instrument conditions, because that
wouldn't be legal unless you declared an
emergency-but under visual conditions
or at night. If you're flying to an unfamiliar
airport, you can dial in the ILS
frequency and pick up the localizer to
help you navigate to the runway. At night,
keeping on or above the glideslope will
prevent you from running into obstacles
such as trees, wires, or buildings before
you touch down.
jill.tallman@aopa.org
35º
Localizer
Antenna Array
700 feet wide
Runway
3º- 6º
Glideslope
Antenna
10º
35º
16
FLIGHT TRAINING MARCH/APRIL 2024
APRIL 2017
150 Hz
90 Hz
10º
STEVE KARP
10 NM
18 NM

Flight Training - March/April 2024

Table of Contents for the Digital Edition of Flight Training - March/April 2024

Contents
Flight Training - March/April 2024 - Intro
Flight Training - March/April 2024 - Cover1
Flight Training - March/April 2024 - Cover2
Flight Training - March/April 2024 - Contents
Flight Training - March/April 2024 - 2
Flight Training - March/April 2024 - 3
Flight Training - March/April 2024 - 4
Flight Training - March/April 2024 - 5
Flight Training - March/April 2024 - 6
Flight Training - March/April 2024 - 7
Flight Training - March/April 2024 - 8
Flight Training - March/April 2024 - 9
Flight Training - March/April 2024 - 10
Flight Training - March/April 2024 - 11
Flight Training - March/April 2024 - 12
Flight Training - March/April 2024 - 13
Flight Training - March/April 2024 - 14
Flight Training - March/April 2024 - 15
Flight Training - March/April 2024 - 16
Flight Training - March/April 2024 - 17
Flight Training - March/April 2024 - 18
Flight Training - March/April 2024 - 19
Flight Training - March/April 2024 - 20
Flight Training - March/April 2024 - 21
Flight Training - March/April 2024 - 22
Flight Training - March/April 2024 - 23
Flight Training - March/April 2024 - 24
Flight Training - March/April 2024 - 25
Flight Training - March/April 2024 - 26
Flight Training - March/April 2024 - 27
Flight Training - March/April 2024 - 28
Flight Training - March/April 2024 - 29
Flight Training - March/April 2024 - 30
Flight Training - March/April 2024 - 31
Flight Training - March/April 2024 - 32
Flight Training - March/April 2024 - 33
Flight Training - March/April 2024 - 34
Flight Training - March/April 2024 - 35
Flight Training - March/April 2024 - 36
Flight Training - March/April 2024 - 37
Flight Training - March/April 2024 - 38
Flight Training - March/April 2024 - 39
Flight Training - March/April 2024 - 40
Flight Training - March/April 2024 - 41
Flight Training - March/April 2024 - 42
Flight Training - March/April 2024 - 43
Flight Training - March/April 2024 - 44
Flight Training - March/April 2024 - 45
Flight Training - March/April 2024 - 46
Flight Training - March/April 2024 - 47
Flight Training - March/April 2024 - 48
Flight Training - March/April 2024 - 49
Flight Training - March/April 2024 - 50
Flight Training - March/April 2024 - 51
Flight Training - March/April 2024 - 52
Flight Training - March/April 2024 - 53
Flight Training - March/April 2024 - 54
Flight Training - March/April 2024 - 55
Flight Training - March/April 2024 - 56
Flight Training - March/April 2024 - Cover3
Flight Training - March/April 2024 - Cover4
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