2-1-1.
Approach Light Systems (ALS)
a.
ALS provide the basic means to
transition from instrument flight to visual flight for
landing. Operational requirements dictate the
sophistication and configuration of the approach light
system for a particular runway.
b.
ALS are a configuration of signal
lights starting at the landing threshold and extending
into the approach area a distance of 2400-3000 feet
for precision instrument runways and 1400-1500 feet
for nonprecision instrument runways. Some systems
include sequenced flashing lights which appear to the
pilot as a ball of light traveling towards the runway
at high speed (twice a second). (See FIG 2-1-1.)
FIG 2-1-1
Precision &
Nonprecision Configurations
2-1-2.
Visual Glideslope Indicators
a. Visual Approach
Slope Indicator (VASI)
1.
The VASI is a system of lights so
arranged to provide visual descent guidance
information during the approach to a runway. These
lights are visible from 3-5 miles during the day and
up to 20 miles or more at night. The visual glide
path of the VASI provides safe obstruction clearance
within plus or minus 10 degrees of the extended
runway centerline and to 4 NM from the runway
threshold. Descent, using the VASI, should not be
initiated until the aircraft is visually aligned
with the runway. Lateral course guidance is provided
by the runway or runway lights.
2.
VASI installations may consist of
either 2, 4, 6, 12, or 16 light units arranged in
bars referred to as near, middle, and far bars. Most
VASI installations consist of 2 bars, near and far,
and may consist of 2, 4, or 12 light units. Some
VASI's consist of three bars, near, middle, and far,
which provide an additional visual glide path to
accommodate high cockpit aircraft. This installation
may consist of either 6 or 16 light units. VASI
installations consisting of 2, 4, or 6 light units
are located on one side of the runway, usually the
left. Where the installation consists of 12 or 16
light units, the units are located on both sides of
the runway.
3.
Two-bar VASI installations provide
one visual glide path which is normally set at 3
degrees. Three-bar VASI installations provide two
visual glide paths. The lower glide path is provided
by the near and middle bars and is normally set at 3
degrees while the upper glide path, provided by the
middle and far bars, is normally 1/4
degree higher. This higher glide path is intended
for use only by high cockpit aircraft to provide a
sufficient threshold crossing height. Although
normal glide path angles are three degrees, angles
at some locations may be as high as 4.5 degrees to
give proper obstacle clearance. Pilots of high
performance aircraft are cautioned that use of VASI
angles in excess of 3.5 degrees may cause an
increase in runway length required for landing and
rollout.
4.
The basic principle of the VASI is
that of color differentiation between red and white.
Each light unit projects a beam of light having a
white segment in the upper part of the beam and red
segment in the lower part of the beam. The light
units are arranged so that the pilot using the
VASI's during an approach will see the combination
of lights shown below.
5.
For 2-bar VASI (4 light units) see
FIG 2-1-2.
FIG 2-1-2
2-Bar VASI
6.
For 3-bar VASI (6 light units) see
FIG 2-1-3.
FIG 2-1-3
3-Bar VASI
7.
For other VASI configurations see FIG
2-1-4.
FIG 2-1-4
VASI Variations
b. Precision
Approach Path Indicator (PAPI).
The precision approach path indicator (PAPI) uses
light units similar to the VASI but are installed in a
single row of either two or four light units. These
systems have an effective visual range of about 5
miles during the day and up to 20 miles at night. The
row of light units is normally installed on the left
side of the runway and the glide path indications are
as depicted. (See FIG 2-1-5.)
FIG 2-1-5
Precision Approach
Path Indicator (PAPI)
c. Tri-color
Systems. Tri-color visual
approach slope indicators normally consist of a single
light unit projecting a three-color visual approach
path into the final approach area of the runway upon
which the indicator is installed. The below glide path
indication is red, the above glide path indication is
amber, and the on glide path indication is green.
These types of indicators have a useful range of
approximately one-half to one mile during the day and
up to five miles at night depending upon the
visibility conditions. (See FIG 2-1-6.)
FIG 2-1-6
Tri-Color Visual
Approach Slope Indicator
NOTE-
1. Since the tri-color VASI consists of a single light
source which could possibly be confused with other
light sources, pilots should exercise care to properly
locate and identify the light signal.
2. When the aircraft descends from green to red, the
pilot may see a dark amber color during the transition
from green to red.
d. Pulsating
Systems. Pulsating visual
approach slope indicators 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 glide path
indication is a steady white light. The slightly below
glide path indication is a steady red light. If the
aircraft descends further below the glide path, the
red light starts to pulsate. The above glide path
indication is a pulsating white light. The pulsating
rate increases as the aircraft gets further above or
below the desired glide slope. The useful range of the
system is about four miles during the day and up to
ten miles at night.
(See FIG 2-1-7.)
FIG 2-1-7
Pulsating Visual
Approach Slope Indicator
NOTE-
Since the PVASI consists of a single light source
which could possibly be confused with other light
sources, pilots should exercise care to properly
locate and identify the light signal.
e. Alignment of
Elements Systems. Alignment
of elements systems are installed on some small
general aviation airports and are a low-cost system
consisting of painted plywood panels, normally black
and white or fluorescent orange. Some of these systems
are lighted for night use. The useful range of these
systems is approximately three-quarter miles. To use
the system the pilot positions the aircraft so the
elements are in alignment. The glide path indications
are shown in FIG 2-1-8.
FIG 2-1-8
Alignment of
Elements
2-1-3.
Runway End Identifier Lights (REIL)
REIL's 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. REIL's may be either omnidirectional
or unidirectional facing the approach area. They are
effective for:
a.
Identification of a runway surrounded
by a preponderance of other lighting.
b.
Identification of a runway which lacks
contrast with surrounding terrain.
c.
Identification of a runway during
reduced visibility.
2-1-4.
Runway Edge Light Systems
a.
Runway edge lights are used to outline
the edges of runways during periods of darkness or
restricted visibility conditions. These light systems
are classified according to the intensity or
brightness they are capable of producing: they are the
High Intensity Runway Lights (HIRL), Medium Intensity
Runway Lights (MIRL), and the Low Intensity Runway
Lights (LIRL). The HIRL and MIRL systems have variable
intensity controls, whereas the LIRL's normally have
one intensity setting.
b.
The runway edge lights are white,
except on instrument runways yellow replaces white on
the last 2,000 feet or half the runway length,
whichever is less, to form a caution zone for
landings.
c.
The lights marking the ends of the
runway emit red light toward the runway to indicate
the end of runway to a departing aircraft and emit
green outward from the runway end to indicate the
threshold to landing aircraft.
2-1-5.
In-runway Lighting
a. Runway Centerline
Lighting System (RCLS).
Runway centerline lights are 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, and for
the last 1,000 feet of the runway, all centerline
lights are red.
b. Touchdown Zone
Lights (TDZL).
Touchdown
zone lights are 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 which 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.
c. Taxiway Lead-Off
Lights. Taxiway lead-off
lights extend from the runway centerline to a point on
an exit taxiway to expedite movement of aircraft from
the runway. These lights alternate green and yellow
from the runway centerline to the runway holding
position or the ILS/MLS critical area, as appropriate.
d. Land and Hold
Short Lights. Land and hold
short lights are used to indicate the hold short point
on certain runways which are approved for Land and
Hold Short Operations (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 will be on anytime LAHSO
is in effect. These lights will be off when LAHSO is
not in effect.
REFERENCE-
AIM, Pilot Responsibilities When Conducting Land and
Hold Short Operations (LAHSO), Paragraph
4-3-11.
2-1-6.
Control of Lighting Systems
a.
Operation of approach light systems and
runway lighting is controlled by the control tower (ATCT).
At some locations the FSS may control the lights where
there is no control tower in operation.
b.
Pilots may request that lights be
turned on or off. Runway edge lights, in-pavement
lights and approach lights also have intensity
controls which may be varied to meet the pilots
request. Sequenced flashing lights (SFL) may be turned
on and off. Some sequenced flashing light systems also
have intensity control.
TBL 2-1-1
Runways With Approach
Lights
Lighting System
|
No. of Int.
Steps
|
Status During
Nonuse Period
|
Intensity Step
Selected Per No. of Mike Clicks
|
|
|
|
3 Clicks
|
5 Clicks
|
7 Clicks
|
Approach Lights
(Med. Int.) |
2 |
Off |
Low |
Low |
High |
Approach Lights
(Med. Int.) |
3 |
Off |
Low |
Med |
High |
MIRL |
3 |
Off or Low
|
u |
u |
u |
HIRL |
5 |
Off or Low
|
u |
u |
u |
VASI |
2 |
Off
|
* |
* |
*
|
NOTES:
uPredetermined
intensity step.
*Low
intensity for night use. High intensity for day
use as determined by photocell control.
|
TBL 2-1-2
Runways Without Approach
Lights
Lighting System
|
No. of Int.
Steps
|
Status During
Nonuse Period
|
Intensity Step
Selected Per No. of Mike Clicks
|
|
|
|
3 Clicks
|
5 Clicks
|
7 Clicks
|
MIRL |
3 |
Off or Low
|
Low |
Med. |
High |
HIRL |
5 |
Off or Low
|
Step 1 or 2
|
Step 3
|
Step 5
|
LIRL |
1 |
Off |
On |
On |
On |
VASIL* |
2 |
Off
|
u |
u |
u |
REILL* |
1 |
Off |
Off |
On /Off
|
On |
REILL* |
3 |
Off |
Low |
Med. |
High |
NOTES:
uLow
intensity for night use. High intensity for day
use as determined by photocell control.
*The
control of VASI and/or REIL may be independent of
other lighting systems. |
2-1-7. Pilot Control of Airport
Lighting
Radio control of lighting
is available at selected airports to provide airborne
control of lights by keying the aircraft's microphone.
Control of lighting systems is often available at
locations without specified hours for lighting and where
there is no control tower or FSS or when the tower or
FSS is closed (locations with a part-time tower or FSS)
or specified hours. All lighting systems which are radio
controlled at an airport, whether on a single runway or
multiple runways, operate on the same radio frequency.
a.
With FAA approved systems, various
combinations of medium intensity approach lights,
runway lights, taxiway lights, VASI and/or REIL may be
activated by radio control. On runways with both
approach lighting and runway lighting (runway edge
lights, taxiway lights, etc.) systems, the approach
lighting system takes precedence for air-to-ground
radio control over the runway lighting system which is
set at a predetermined intensity step, based on
expected visibility conditions. Runways without
approach lighting may provide radio controlled
intensity adjustments of runway edge lights. Other
lighting systems, including VASI, REIL, and taxiway
lights may be either controlled with the runway edge
lights or controlled independently of the runway edge
lights.
b.
The control system consists of a 3-step
control responsive to 7, 5, and/or 3 microphone
clicks. This 3-step control will turn on lighting
facilities capable of either 3-step, 2-step or 1-step
operation. The 3-step and 2-step lighting facilities
can be altered in intensity, while the 1-step cannot.
All lighting is illuminated for a period of 15 minutes
from the most recent time of activation and may not be
extinguished prior to end of the 15 minute period
(except for 1-step and 2-step REIL's which may be
turned off when desired by keying the mike 5 or 3
times respectively).
c.
Suggested use is to always initially
key the mike 7 times; this assures that all controlled
lights are turned on to the maximum available
intensity. If desired, adjustment can then be made,
where the capability is provided, to a lower intensity
(or the REIL turned off) by keying 5 and/or 3 times.
Due to the close proximity of airports using the same
frequency, radio controlled lighting receivers may be
set at a low sensitivity requiring the aircraft to be
relatively close to activate the system. Consequently,
even when lights are on, always key mike as directed
when overflying an airport of intended landing or just
prior to entering the final segment of an approach.
This will assure the aircraft is close enough to
activate the system and a full 15 minutes lighting
duration is available. Approved lighting systems may
be activated by keying the mike (within 5 seconds) as
indicated in TBL 2-1-3.
TBL 2-1-3
Radio Control System
Key Mike
|
Function
|
7 times within 5
seconds |
Highest intensity
available |
5 times within 5
seconds |
Medium or lower
intensity (Lower REIL or REIL-off) |
3 times within 5
seconds |
Lowest intensity
available (Lower REIL or REIL-off) |
d. For all public use
airports with FAA standard systems the
Airport/Facility Directory contains the types of
lighting, runway and the frequency that is used to
activate the system. Airports with IAP's include data
on the approach chart identifying the light system,
the runway on which they are installed, and the
frequency that is used to activate the system.
NOTE-
Although the CTAF is used to activate the lights at
many airports, other frequencies may also be used. The
appropriate frequency for activating the lights on the
airport is provided in the Airport/Facility Directory
and the standard instrument approach procedures
publications. It is not identified on the sectional
charts.
e.
Where the airport is not served by an
IAP, it may have either the standard FAA approved
control system or an independent type system of
different specification installed by the airport
sponsor. The Airport/Facility Directory contains
descriptions of pilot controlled lighting systems for
each airport having other than FAA approved systems,
and explains the type lights, method of control, and
operating frequency in clear text.
2-1-8.
Airport/Heliport Beacons
a.
Airport and heliport beacons have a
vertical light distribution to make them most
effective from one to ten degrees above the horizon;
however, they can be seen well above and below this
peak spread. The beacon may be an omnidirectional
capacitor-discharge device, or it may rotate at a
constant speed which produces the visual effect of
flashes at regular intervals. Flashes may be one or
two colors alternately. The total number of flashes
are:
1.
24 to 30 per minute for beacons
marking airports, landmarks, and points on Federal
airways.
2.
30 to 45 per minute for beacons
marking heliports.
b.
The colors and color combinations of
beacons are:
1.
White and Green- Lighted land
airport.
2.
*Green alone- Lighted land airport.
3.
White and Yellow- Lighted water
airport.
4.
*Yellow alone- Lighted water airport.
5.
Green, Yellow, and White- Lighted
heliport.
NOTE-
*Green alone or yellow alone is used only in
connection with a white-and-green or
white-and-yellow beacon display, respectively.
c.
Military airport beacons flash
alternately white and green, but are differentiated
from civil beacons by dualpeaked (two quick) white
flashes between the green flashes.
d.
In Class B, Class C, Class D and Class
E surface areas, operation of the airport beacon
during the hours of daylight often indicates that the
ground visibility is less than 3 miles and/or the
ceiling is less than 1,000 feet. ATC clearance in
accordance with 14 CFR Part 91 is required for
landing, takeoff and flight in the traffic pattern.
Pilots should not rely solely on the operation of the
airport beacon to indicate if weather conditions are
IFR or VFR. At some locations with operating control
towers, ATC personnel turn the beacon on or off when
controls are in the tower. At many airports the
airport beacon is turned on by a photoelectric cell or
time clocks and ATC personnel can not control them.
There is no regulatory requirement for daylight
operation and it is the pilot's responsibility to
comply with proper preflight planning as required by
14 CFR Section 91.103.
2-1-9. Taxiway
Lights
a. Taxiway Edge
Lights. Taxiway edge lights
are used to outline the edges of taxiways during
periods of darkness or restricted visibility
conditions. These fixtures emit blue light.
NOTE-
At most major airports these lights have variable
intensity settings and may be adjusted at pilot
request or when deemed necessary by the controller.
b. Taxiway
Centerline Lights. Taxiway
centerline lights are used to facilitate ground
traffic under low visibility conditions. They are
located along the taxiway centerline in a straight
line on straight portions, on the centerline of curved
portions, and along designated taxiing paths in
portions of runways, ramp, and apron areas. Taxiway
centerline lights are steady burning and emit green
light.
c.
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.
d. 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 in paragraph
2-1-9c, Clearance Bar Lights.
e. 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). 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.
CAUTION-
Pilots should never cross a red illuminated stop bar,
even if an ATC clearance has been given to proceed
onto or across the runway.
NOTE-
If after crossing a stop bar, the taxiway centerline
lead-on lights inadvertently extinguish, pilots should
hold their position and contact ATC for further
instructions.
|