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Airport Lighting Aids


AIM, Paragraph 4−3−11 , Pilot Responsibilities When Conducting Land

and Hold Short Operations (LAHSO)

2−1−6. Runway Status Light (RWSL)


a. Introduction.

RWSL is a fully automated system that provides

runway status information to pilots and surface

vehicle operators to clearly indicate when it is unsafe

to enter, cross, takeoff from, or land on a runway. The

RWSL system processes information from surveil-

lance systems and activates Runway Entrance Lights

(REL), Takeoff Hold Lights (THL), Runway

Intersection Lights (RIL), and Final Approach

Runway Occupancy Signal (FAROS) in accordance

with the position and velocity of the detected surface

traffic and approach traffic. REL, THL, and RIL are

in-pavement light fixtures that are directly visible to

pilots and surface vehicle operators. FAROS alerts

arriving pilots that the approaching runway is

occupied by flashing the Precision Approach Path

Indicator (PAPI). FAROS may be implemented as an

add-on to the RWSL system or implemented as a

stand-alone system at airports without a RWSL

system. RWSL is an independent safety enhancement

that does not substitute for or convey an ATC

clearance. Clearance to enter, cross, takeoff from,

land on, or operate on a runway must still be received

from ATC. Although ATC has limited control over

the system, personnel do not directly use and may not

be able to view light fixture activations and

deactivations during the conduct of daily ATC


b. Runway Entrance Lights (REL): The REL

system is composed of flush mounted, in-pavement,

unidirectional light fixtures that are parallel to and

focused along the taxiway centerline and directed

toward the pilot at the hold line. An array of REL

lights include the first light at the hold line followed

by a series of evenly spaced lights to the runway edge;

one additional light at the runway centerline is in line

with the last two lights before the runway edge (see

FIG 2−1−9 and FIG 2−1−12). When activated, the

red lights indicate that there is high speed traffic on

the runway or there is an aircraft on final approach

within the activation area.

1. REL Operating Characteristics − Departing


When a departing aircraft reaches a site adaptable

speed of approximately 30 knots, all taxiway

intersections with REL arrays along the runway

ahead of the aircraft will illuminate (see FIG 2−1−9).

As the aircraft approaches an REL equipped taxiway

intersection, the lights at that intersection extinguish

approximately 3 to 4 seconds before the aircraft

reaches it. This allows controllers to apply

“anticipated separation” to permit ATC to move

traffic more expeditiously without compromising

safety. After the aircraft is declared “airborne” by the

system, all REL lights associated with this runway

will extinguish.

2. REL Operating Characteristics − Arriving


When an aircraft on final approach is approximately

1 mile from the runway threshold, all sets of taxiway

REL light arrays that intersect the runway illuminate.

The distance is adjustable and can be configured for

specific operations at particular airports. Lights

extinguish at each equipped taxiway intersection

approximately 3 to 4 seconds before the aircraft

reaches it to apply anticipated separation until the

aircraft has slowed to approximately 80 knots (site

adjustable parameter). Below 80 knots, all arrays that

are not within 30 seconds of the aircraft’s forward

path are extinguished. Once the arriving aircraft

slows to approximately 34 knots (site adjustable

parameter), it is declared to be in a taxi state, and all

lights extinguish.

3. What a pilot would observe: A pilot at or

approaching the hold line to a runway will observe

RELs illuminate and extinguish in reaction to an

aircraft or vehicle operating on the runway, or an

arriving aircraft operating less than 1 mile from the

runway threshold.

4. When a pilot observes the red lights of the

REL, that pilot will stop at the hold line or remain

stopped. The pilot will then contact ATC for

resolution if the clearance is in conflict with the

lights. Should pilots note illuminated lights under

circumstances when remaining clear of the runway is

impractical for safety reasons (for example, aircraft

is already on the runway), the crew should proceed

according to their best judgment while understanding

the illuminated lights indicate the runway is unsafe to

enter or cross. Contact ATC at the earliest possible