On GlidepathBelow Glidepath Above Glidepath
Far Bar
Near Bar
Far Bar
Near Bar
Far Bar
Near Bar
Figure 14-29. Two-bar VASI system.
High
more than 3.5°
Slightly High
3.2°
On Glidepath
3°
Slightly Low
2.8°
Low
less than 2.5°
Figure 14-30. Precision approach path indicator for a typical 3° glide slope.
Below glidepath
Above glidepath
On glidepath
Amber
Red
Green
Amber
Figure 14-31. Tri-color visual approach slope indicator.
A tri-color system consists of a single-light unit projecting
a three-color visual approach path. Below the glidepath is
indicated by red, on the glidepath is indicated by green, and
above the glidepath is indicated by amber. When descending
below the glidepath, there is a small area of dark amber. Pilots
should not mistake this area for an “above the glidepath”
indication. [Figure 14-31]
Pulsating VASIs normally consist of a single-light unit
projecting a two-color visual approach path into the final
approach area of the runway upon which the indicator is
installed. The “on glidepath” indication is a steady white
light. The “slightly below glidepath” indication is a steady red
light. If the aircraft descends further below the glidepath, the
red light starts to pulsate. The “above glidepath” indication
is a pulsating white light. The pulsating rate increases as the
aircraft gets further above or below the desired glideslope.
The useful range of the system is about four miles during the
day and up to ten miles at night. [Figure 14-32]
Runway Lighting
There are various lights that identify parts of the runway
complex. These assist a pilot in safely making a takeoff or
landing during night operations.
Runway End Identifier Lights (REIL)
Runway end identifier lights (REIL) are installed at many
airfields to provide rapid and positive identification of the
approach end of a particular runway. The system consists
of a pair of synchronized flashing lights located laterally
on each side of the runway threshold. REILs may be either
omnidirectional or unidirectional facing the approach area.
Runway Edge Lights
Runway edge lights are used to outline the edges of
runways at night or during low visibility conditions.
[Figure 14-33] These lights are classified according to the
intensity they are capable of producing: high intensity runway
lights (HIRL), medium intensity runway lights (MIRL), and
Below glidepath
Above glidepath
On glidepath
Pulsatingwhite
Pulsating red
Steady
white
Threshold
Slightly below glidepath
Steady
red
Figure 14-32. Pulsating visual approach slope indicator.
Figure 14-33. Runway lights.
low intensity runway lights (LIRL). The HIRL and MIRL
have variable intensity settings. These lights are white, except
on instrument runways where amber lights are used on the
last 2,000 feet or half the length of the runway, whichever
is less. The lights marking the end of the runway are red.
In-Runway Lighting
Runway centerline lighting system (RCLS)—installed on some
precision approach runways to facilitate landing under adverse
visibility conditions. They are located along the runway
centerline and are spaced at 50-foot intervals. When viewed
from the landing threshold, the runway centerline lights are
white until the last 3,000 feet of the runway. The white lights
begin to alternate with red for the next 2,000 feet. For the
remaining 1,000 feet of the runway, all centerline lights are red.
Touchdown zone lights (TDZL)—installed on some precision
approach runways to indicate the touchdown zone when
landing under adverse visibility conditions. They consist of
two rows of transverse light bars disposed symmetrically
about the runway centerline. The system consists of steady-
burning white lights that start 100 feet beyond the landing
threshold and extend to 3,000 feet beyond the landing
threshold or to the midpoint of the runway, whichever is less.
Taxiway centerline lead-off lights—provide visual guidance
to persons exiting the runway. They are color-coded to warn
pilots and vehicle drivers that they are within the runway
environment or ILS critical area, whichever is more restrictive.
Alternate green and yellow lights are installed, beginning
with green, from the runway centerline to one centerline light
position beyond the runway holding position or ILS critical
area holding position.
Taxiway centerline lead-on lights—provide visual guidance
to persons entering the runway. These “lead-on” lights are
also color-coded with the same color pattern as lead-off
lights to warn pilots and vehicle drivers that they are within
the runway environment or ILS critical area, whichever is
more conservative. The fixtures used for lead-on lights are
bidirectional (i.e., one side emits light for the lead-on function
while the other side emits light for the lead-off function). Any
fixture that emits yellow light for the lead-off function also
emits yellow light for the lead-on function.
Land and hold short lights—used to indicate the hold short
point on certain runways which are approved for LAHSO.
Land and hold short lights consist of a row of pulsing white
lights installed across the runway at the hold short point.
Where installed, the lights are on anytime LAHSO is in effect.
These lights are off when LAHSO is not in effect.
Control of Airport Lighting
Airport lighting is controlled by ATC at towered airports. At
nontowered airports, the lights may be on a timer, or where an
FSS is located at an airport, the FSS personnel may control the
lighting. A pilot may request various light systems be turned
on or off and also request a specified intensity, if available,
from ATC or FSS personnel. At selected nontowered airports,
the pilot may control the lighting by using the radio. This
is done by selecting a specified frequency and clicking the
radio microphone. [Figure 14-34] For information on pilot
controlled lighting at various airports, refer to the Chart
Supplement U.S. (formerly Airport/Facility Directory).
FunctionKey Mike
Highest intensity available
Medium or lower intensity
(Lower REIL or REIL off)
Lowest intensity available
(Lower REIL or REIL off)
7 times within 5 seconds
5 times within 5 seconds
3 times within 5 seconds
Figure 14-34. Radio controlled runway lighting.
Taxiway Lights
Similar to runway lighting, taxiways also have various lights
which help pilots identify areas of the taxiway and any
surrounding runways.
Omnidirectional
Omnidirectional taxiway lights outline the edges of the
taxiway and are blue in color. At many airports, these
edge lights may have variable intensity settings that may
be adjusted by an ATC when deemed necessary or when
requested by the pilot. Some airports also have taxiway
centerline lights that are green in color.
Clearance Bar Lights
Clearance bar lights are installed at holding positions on
taxiways in order to increase the conspicuity of the holding
position in low visibility conditions. They may also be
installed to indicate the location of an intersecting taxiway
during periods of darkness. Clearance bars consist of three
in-pavement steady-burning yellow lights.
Runway Guard Lights
Runway guard lights are installed at taxiway/runway
intersections. They are primarily used to enhance the
conspicuity of taxiway/runway intersections during low
visibility conditions, but may be used in all weather conditions.
Runway guard lights consist of either a pair of elevated flashing
yellow lights installed on either side of the taxiway, or a row of
in-pavement yellow lights installed across the entire taxiway,
at the runway holding position marking.
Note: Some airports may have a row of three or five
in-pavement yellow lights installed at taxiway/runway
intersections. They should not be confused with clearance
bar lights described previously in this section.
Stop Bar Lights
Stop bar lights, when installed, are used to confirm the ATC
clearance to enter or cross the active runway in low visibility
conditions (below 1,200 ft Runway Visual Range (RVR)).
A stop bar consists of a row of red, unidirectional, steady-
burning in-pavement lights installed across the entire taxiway
at the runway holding position, and elevated steady-burning
red lights on each side. A controlled stop bar is operated in
conjunction with the taxiway centerline lead-on lights which
extend from the stop bar toward the runway. Following the
ATC clearance to proceed, the stop bar is turned off and the
lead-on lights are turned on. The stop bar and lead-on lights
are automatically reset by a sensor or backup timer.
Obstruction Lights
Obstructions are marked or lighted to warn pilots of
their presence during daytime and nighttime conditions.
Obstruction lighting can be found both on and off an airport
to identify obstructions. They may be marked or lighted in
any of the following conditions.
• Red obstruction lights—flash or emit a steady red
color during nighttime operations, and the obstructions
are painted orange and white for daytime operations.
• High intensity white obstruction lights—flash high
intensity white lights during the daytime with the
intensity reduced for nighttime.
• Dual lighting—a combination of flashing red beacons
and steady red lights for nighttime operation and high
intensity white lights for daytime operations.
New Lighting Technologies
A top priority of the FAA is to continue to enhance airport
safety while maintaining airport capacity. Reducing runway
incursions is a major component of this effort. Runway
incursions develop quickly and without warning during routine
traffic situations on the airport surface, leaving little time for
corrective action. The Runway Status Lights (RWSL) System
is designed to provide a direct indication to you that it is unsafe
to enter a runway, cross a runway, or takeoff from or land on
a runway when the system is activated.
Runway status lights are red in color and indicate runway
status only; they do not indicate clearance to enter a runway
or clearance to takeoff. The RWSL system provides warning
lights on runways and taxiways, illuminating when it is unsafe
to enter, cross, or begin takeoff on a runway. Currently, there
are two types: Runway Entrance Lights (REL) and Takeoff
Hold Lights (THL). [Figures 14-35 and 14-36]
REL provide a warning to aircraft crossing or entering a
runway from intersecting taxiways that there is conflicting
traffic on the runway. THL provide a warning signal to
aircraft in position for takeoff that the runway is occupied
and it is unsafe to take off. As of 2016, the RWSL system is
operational at 14 of the nation’s busiest airports with 3 more
airports scheduled to receive the system by 2017.
Figure 14-35. Runway Entrance Lights (REL).
Figure 14-36. Takeoff Hold Lights (THL).
Wind Direction Indicators
It is important for a pilot to know the direction of the wind. At
facilities with an operating control tower, this information is
provided by ATC. Information may also be provided by FSS
personnel either located at a particular airport or remotely
available through a remote communication outlet (RCO), or
by requesting information on a CTAF at airports that have the
capacity to receive and broadcast on this frequency.
When none of these services is available, it is possible
to determine wind direction and runway in use by visual
wind indicators. A pilot should check these wind indicators
even when information is provided on the CTAF at a given
airport because there is no assurance that the information
provided is accurate.
The wind direction indicator can be a wind cone, wind sock,
tetrahedron, or wind tee. These are usually located in a central
location near the runway and may be placed in the center
of a segmented circle, which identifies the traffic pattern
direction if it is other than the standard left-hand pattern.
[Figures 14-37 and 14-38]
The wind sock is a good source of information since it not
only indicates wind direction but allows the pilot to estimate
the wind velocity and/or gust factor. The wind sock extends
out straighter in strong winds and tends to move back and
forth when the wind is gusting. Wind tees and tetrahedrons
can swing freely and align themselves with the wind direction.
Since a wind tee or tetrahedron can also be manually set to
align with the runway in use, a pilot should also look at the
wind sock for wind information, if one is available.
Traffic Patterns
At airports without an operating control tower, a segmented
circle visual indicator system , if installed, is designed to
provide traffic pattern information. [Figure 14-38] Usually
located in a position affording maximum visibility to pilots in
the air and on the ground and providing a centralized location
for other elements of the system, the segmented circle consists
of the following components: wind direction indicators,
landing direction indicators, landing strip indicators, and
traffic pattern indicators.
A tetrahedron is installed to indicate the direction of landings
and takeoffs when conditions at the airport warrant its use.
It may be located at the center of a segmented circle and
may be lighted for night operations. The small end of the
tetrahedron points in the direction of landing. Pilots are
cautioned against using a tetrahedron for any purpose other
than as an indicator of landing direction. At airports with
control towers, the tetrahedron should only be referenced
when the control tower is not in operation. Tower instructions
supersede tetrahedron indications.
Landing strip indicators are installed in pairs and are used to
show the alignment of landing strips. [Figure 14-38] Traffic
pattern indicators are arranged in pairs in conjunction with
landing strip indicators and used to indicate the direction of
turns when there is a variation from the normal left traffic
pattern. (If there is no segmented circle installed at the airport,
traffic pattern indicators may be installed on or near the end
of the runway.)
At most airports and military air bases, traffic pattern altitudes
for propeller-driven aircraft generally extend from 600 feet
to as high as 1,500 feet above ground level (AGL). Pilots
can obtain the traffic pattern altitude for an airport from the
Chart Supplement U.S. (formerly Airport/Facility Directory).
Also, traffic pattern altitudes for military turbojet aircraft
sometimes extend up to 2,500 feet AGL. Therefore, pilots of
en route aircraft should be constantly on alert for other aircraft
in traffic patterns and avoid these areas whenever possible.
When operating at an airport, traffic pattern altitudes should
be maintained unless otherwise required by the applicable
distance from cloud criteria according to Title 14 of the Code
of Federal Regulations (14 CFR) part 91, section 91.155.
Additional information on airport traffic pattern operations
Tetrahedron
Wind sock or cone
Wind tee
WIND
Figure 14-37. Wind direction indicators.
Wind cone
Landing runway
or landing strip
indicators
Landing direction
indicator
Traffic pattern
indicators
Figure 14-38. Segmented circle.
can be found in Chapter 4, “Air Traffic Control,” of the AIM.
Pilots can find traffic pattern information and restrictions, such
as noise abatement in the Chart Supplement U.S. (formerly
Airport/Facility Directory).
Example: Key to Traffic Pattern Operations—
Single Runway
1. Enter pattern in level flight, abeam the midpoint
of the runway, at pattern altitude. (1,000' AGL is
recommended pattern altitude unless otherwise
established.) [Figure 14-39]
2. Maintain pattern altitude until abeam approach end of
the landing runway on downwind leg. [Figure 14-39]
3. Complete turn to final at least ¼ mile from the runway.
[Figure 14-39]
4. After takeoff or go-around, continue straight ahead
until beyond departure end of runway. [Figure 14-39]
5. If remaining in the traffic pattern, commence turn to
crosswind leg beyond the departure end of the runway
within 300 feet of pattern altitude. [Figure 14-39]
6. If departing the traffic pattern, continue straight out,
or exit with a 45° turn (to the left when in a left-hand
traffic pattern; to the right when in a right-hand traffic
pattern) beyond the departure end of the runway, after
reaching pattern altitude. [Figure 14-39]
Example: Key to Traffic Pattern Operations—
Parallel Runways
1. Enter pattern in level flight, abeam the midpoint
of the runway, at pattern altitude. (1,000' AGL is
recommended pattern altitude unless otherwise
established.) [Figure 14-40]
2. Maintain pattern altitude until abeam approach end of
the landing runway on downwind leg. [Figure 14-40]
3. Complete turn to final at least ¼ mile from the runway.
[Figure 14-40]
4. Do not overshoot final or continue on a track that
penetrates the final approach of the parallel runway
5. After takeoff or go-around, continue straight ahead
until beyond departure end of runway. [Figure 14-40]
LEGEND
Recommended standard left-hand traffic
pattern (depicted) (standard right-hand
traffic pattern would be mirror image)
RUNWAY
Final
Departure
Downwind
Base
Crosswind
Departure
Departure
Entry
Application of traffic
pattern indicators
Segmented circle
3 4 6
6
5
2
1
Figure 14-39. Traffic pattern operations—single runway.
6. If remaining in the traffic pattern, commence turn to
crosswind leg beyond the departure end of the runway
within 300 feet of pattern altitude. [Figure 14-40]
7. If departing the traffic pattern, continue straight out,
or exit with a 45° turn (to the left when in a left-hand
traffic pattern; to the right when in a right-hand traffic
pattern) beyond the departure end of the runway, after
reaching pattern altitude. [Figure 14-40]
8. Do not continue on a track that penetrates the departure
path of the parallel runway. [Figure 14-40]
Radio Communications
Operating in and out of a towered airport, as well as in a good
portion of the airspace system, requires that an aircraft have two-
way radio communication capability. For this reason, a pilot
should be knowledgeable of radio station license requirements
and radio communications equipment and procedures.
Radio License
There is no license requirement for a pilot operating in the
United States; however, a pilot who operates internationally
is required to hold a restricted radiotelephone permit issued
by the Federal Communications Commission (FCC). There
is also no station license requirement for most general
aviation aircraft operating in the United States. A station
license is required, however, for an aircraft that is operating
internationally, that uses other than a VHF radio, and that
meets other criteria.
Radio Equipment
In general aviation, the most common types of radios are
VHF. A VHF radio operates on frequencies between 118.0
megahertz (MHz) and 136.975 MHz and is classified as
720 or 760 depending on the number of channels it can
accommodate. The 720 and 760 use .025 MHz (25 kilohertz
(KHz) spacing (118.025, 118.050) with the 720 having a
frequency range up to 135.975 MHz and the 760 reaching
up to 136.975 MHz. VHF radios are limited to line of sight
transmissions; therefore, aircraft at higher altitudes are able
to transmit and receive at greater distances.
In March of 1997, the International Civil Aviation Organization
(ICAO) amended its International Standards and Recommended
Practices to incorporate a channel plan specifying 8.33 kHz
channel spacings in the Aeronautical Mobile Service. The
8.33 kHz channel plan was adopted to alleviate the shortage of
VHF ATC channels experienced in western Europe and in the
United Kingdom. Seven western European countries and the
United Kingdom implemented the 8.33 kHz channel plan on
January 1, 1999. Accordingly, aircraft operating in the airspace
of these countries must have the capability of transmitting and
receiving on the 8.33 kHz spaced channels.
Using Proper Radio Procedures
Using proper radio phraseology and procedures contribute to
a pilot’s ability to operate safely and efficiently in the airspace
system. A review of the Pilot/Controller Glossary contained
in the AIM assists a pilot in the use and understanding of
Figure 14-40. Traffic pattern operation—parallel runways.
LEGEND
Standard left-hand
traffic pattern (depicted)
Right-hand traffic
pattern (depicted)
Final
Departure
Base
Crosswind
Final
Departure
Base
Crosswind
Downwind
Entry
No transgression zone
No transgression zone
Segmented circle
3 4
6
6
5
2
1
3 4 6
6
5
2
1
standard terminology. The AIM also contains many examples
of radio communications.
ICAO has adopted a phonetic alphabet that should be used in
radio communications. When communicating with ATC, pilots
should use this alphabet to identify their aircraft. [Figure 14-41]
Lost Communication Procedures
It is possible that a pilot might experience a malfunction of
the radio. This might cause the transmitter, receiver, or both
to become inoperative. If a receiver becomes inoperative and a
pilot needs to land at a towered airport, it is advisable to remain
outside or above Class D airspace until the direction and flow
of traffic is determined. A pilot should then advise the tower of
the aircraft type, position, altitude, and intention to land. The
pilot should continue, enter the pattern, report a position as
appropriate, and watch for light signals from the tower. Light
signal colors and their meanings are contained in Figure 14-42.
If the transmitter becomes inoperative, a pilot should follow
the previously stated procedures and also monitor the
appropriate ATC frequency. During daylight hours, ATC
transmissions may be acknowledged by rocking the wings
and at night by blinking the landing light.
When both receiver and transmitter are inoperative, the pilot
should remain outside of Class D airspace until the flow of
traffic has been determined and then enter the pattern and
watch for light signals.
Radio malfunctions should be repaired before further
flight. If this is not possible, ATC may be contacted by
telephone requesting a VFR departure without two-way radio
communications. No radio (NORDO) procedure arrivals
are not accepted at busy airports. If authorization is given
to depart, the pilot is advised to monitor the appropriate
frequency and/or watch for light signals as appropriate.
Morse Code Telephony Phonic PronunciationCharacter
r
R
0
q
Q
9
p
P
8
o
O
7
n
N
6
5
5
5
4
4
4
3
3
3
2
2
2
1
1
1
z
Z
Z
y
Y
Y
x
X
X
w
W
W
v
V
V
u
U
U
t
T
T
s
S
S
r
R
R
q
Q
Q
p
P
P
o
O
O
n
N
N
m
M
M
L
L
L
k
K
K
j
J
J
i
I
I
h
h
H
g
G
G
f
F
F
e
E
E
d
D
D
c
C
C
b
B
B
a
A
A
Figure 14-41. Phonetic alphabet.
easily be aware of your presence when they are expecting
the standard radio calls.
Air Traffic Control (ATC) Services
Besides the services provided by an FSS as discussed in
Chapter 12, “Aviation Weather Services,” numerous other
services are provided by ATC. In many instances a pilot
is required to have contact with ATC, but even when not
required, a pilot may find their services helpful.
Primary Radar
Radar is a device that provides information on range, azimuth,
and/or elevation of objects in the path of the transmitted
pulses. It measures the time interval between transmission and
reception of radio pulses and correlates the angular orientation
of the radiated antenna beam or beams in azimuth and/or
elevation. Range is determined by measuring the time it takes
for the radio wave to go out to the object and then return to the
receiving antenna. The direction of a detected object from a
radar site is determined by the position of the rotating antenna
when the reflected portion of the radio wave is received.
Modern radar is very reliable and there are seldom outages.
This is due to reliable maintenance and improved equipment.
There are, however, some limitations that may affect ATC
services and prevent a controller from issuing advisories
concerning aircraft that are not under his or her control and
cannot be seen on radar.
The characteristics of radio waves are such that they normally
travel in a continuous straight line unless they are “bent” by
atmospheric phenomena, such as temperature inversions,
reflected or attenuated by dense objects such as heavy clouds
and precipitation, or screened by high terrain features. Radar
signals degrade over distance, cannot penetrate through solid
objects such as mountains, and the fastest radar updates every
4.7 seconds. By contrast, the satellite signals used with
Automatic Dependent Surveillance−Broadcast (ADS−B) do
not degrade over distance, provide better visibility around
mountainous terrain and allows equipped aircraft to update
their own position once a second with better accuracy.
ATC Radar Beacon System (ATCRBS)
The ATC radar beacon system (ATCRBS) is often referred to
as “secondary surveillance radar.” This system consists of three
components and helps in alleviating some of the limitations
associated with primary radar. The three components are an
interrogator, transponder, and radarscope. The advantages of
ATCRBS are the reinforcement of radar targets, rapid target
identification, and a unique display of selected codes.
Growing air traffic in the National Airspace System (NAS)
will be addressed through the use of ADS-B, which not only
If radio communication is lost, it may be a prudent decision
to land at a non-towered airport with lower traffic volume, if
practical. When operating at a non-towered airport, no radio
communication is necessary. However, pilots should be extra
vigilant when not using the radio. Other traffic may not as