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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.
2-1-3. Runway End Identifier Lights (REIL)
REILs 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. 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
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
LIRLs 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
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). Touch-
down 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 Centerline Lead-Off Lights. Taxi-
way 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
instrument landing system (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.
d. Taxiway Centerline Lead-On Lights. Taxi-
way 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 instrument landing system (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 must also emit yellow light for the lead-on
function. (See FIG 2-1-14.)
e. 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
2-1-6 Airport Lighting Aids