AIM 2-1-6

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2-1-6. Runway Status Light (RWSL) System

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 surveillance 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 traffic. REL, THL, and RIL are in­pavement light fixtures that are directly visible to pilots and surface vehicle operators. The FAROS annunciation is by means of flashing the Precision Approach Path Indicator (PAPI). RWSL is an independent safety enhancement that does not substitute for an ATC clearance. Clearance to enter, cross, takeoff from, land on, or operate on a runway must be issued by ATC. Although ATC has limited control over the system, personnel do not directly use, and may not be able to view, light fixture output in their operations.

b. Runway Entrance Lights (REL): The REL system is composed of flush mounted, in­pavement, unidirectional 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 2-1-10). 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. Operating Characteristics - Departing Aircraft:

When a departing aircraft reaches 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. Operating Characteristics - Arriving Aircraft:

When an aircraft on final approach is approximately 1 mile from the runway threshold, all sets of REL light arrays along 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 REL illumination and extinguishing 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. Whenever 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 opportunity.

FIG 2-1-9 Runway Status Light System

c. Takeoff Hold Lights (THL): The THL system is composed of flush mounted, in-pavement, unidirectional fixtures in a double longitudinal row aligned either side of the runway centerline lighting. Fixtures are focused toward the arrival end of the runway at the “line up and wait" point, and they extend for 1,500 feet in front of the holding aircraft starting at a point 375 feet from the departure threshold (see FIG 2-1-11). Illuminated red lights provide a signal, to an aircraft in position for takeoff or rolling, that it is unsafe to takeoff because the runway is occupied or about to be occupied by another aircraft or ground vehicle. Two aircraft, or a surface vehicle and an aircraft, are required for the lights to illuminate. The departing aircraft must be in position for takeoff or beginning takeoff roll. Another aircraft or a surface vehicle must be on or about to cross the runway.

1. Operating Characteristics - Departing Aircraft:

THLs will illuminate for an aircraft in position for departure or departing when there is another aircraft or vehicle on the runway or about to enter the runway (see FIG 2-1-9.) Once that aircraft or vehicle exits the runway, the THLs extinguish. A pilot may notice lights extinguish prior to the downfield aircraft or vehicle being completely clear of the runway but still moving. Like RELs, THLs have an “anticipated separation" feature.

NOTE - When the THLs extinguish, this is not clearance to begin a takeoff roll. All takeoff clearances will be issued by ATC.

2. What a pilot would observe: A pilot in position to depart from a runway, or has begun takeoff roll, will observe THLs illuminate in reaction to an aircraft or vehicle on the runway or entering or crossing it. Lights will extinguish when the runway is clear. A pilot may observe several cycles of illumination and extinguishing depending on the amount of crossing traffic.

3. Whenever a pilot observes the red light of the THLs, the pilot will stop or remain stopped. The pilot will contact ATC for resolution if any clearance is in conflict with the lights. Should pilots note illuminated lights while in takeoff roll and under circumstances when stopping is impractical for safety reasons, the crew should proceed according to their best judgment while understanding the illuminated lights indicate that continuing the takeoff is unsafe. Contact ATC at the earliest possible opportunity.

d. Runway Intersection Lights (RIL): The RIL system is composed of flush mounted, in-pavement, unidirectional fixtures in a double longitudinal row aligned either side of the runway centerline lighting in the same manner as THLs. Their appearance to a pilot is similar to that of THLs. Fixtures are focused toward the arrival end of the runway, and they extend for 3,000 feet in front of an aircraft that is approaching an intersecting runway. They end at the Land and Hold Short Operation (LASHO) light bar or the hold short line for the intersecting runway.

1. Operating Characteristics - Departing Aircraft:

RILs will illuminate for an aircraft departing or in position to depart when there is high speed traffic operating on the intersecting runway (see FIG 2-1-9). Note that there must be an aircraft or vehicle in a position to observe the RILs for them to illuminate. Once that traffic passes through the intersection, the RILs extinguish.

2. Operating Characteristics - Arriving Aircraft:

RILs will illuminate for an aircraft that has landed and is rolling out when there is high speed traffic on the intersecting runway that is ±5 seconds of meeting at the intersection. Once that traffic passes through the intersection, the RILs extinguish.

3. What a pilot would observe: A pilot departing or arriving will observe RILs illuminate in reaction to the high speed traffic operation on the intersecting runway. The lights will extinguish when that traffic has passed through the runway intersection.

4. Whenever a pilot observes the red light of the RIL array, the pilot will stop before the LAHSO stop bar or the hold line for the intersecting runway. If a departing aircraft is already at high speed in the takeoff roll when the RILs illuminate, it may be impractical to stop for safety reasons. The crew should safely operate according to their best judgment while understanding the illuminated lights indicate that continuing the takeoff is unsafe. Contact ATC at the earliest possible opportunity.

e. The Final Approach Runway Occupancy Signal (FAROS) is activated by flashing of the Precision Approach Path Indicator (PAPI) (see FIG 2­1­9). When activated, the light fixtures of the PAPI flash or pulse to indicate to the pilot on an approach that the runway is occupied and that it may be unsafe to land.

1. Operating Characteristics:

If an aircraft or surface vehicle occupies a FAROS equipped runway, the PAPI(s) on that runway will flash or pulse. The glide path indication will not be affected, and the allotment of red and white PAPI lights observed by the pilot on approach will not change. Some FAROS systems will flash or pulse the PAPI when traffic enters the runway whether or not there is an aircraft on approach. Others will flash the PAPI only if there is an aircraft on approach and within 1.5 nautical miles of the landing threshold.

2. What a pilot would observe: A pilot on approach to the runway will observe the PAPI flash or pulse if there is traffic on the runway and will notice the PAPI ceases to flash or pulse when the traffic moves outside the hold short lines for the runway.

3. Whenever a pilot observes a flashing or pulsing PAPI, the pilot will verify the FAROS activation. At 500 feet above ground level (AGL), the contact height, the pilot must look for and acquire the traffic on the runway. At 300 feet AGL, the pilot must contact ATC for resolution if the clearance is in conflict with the FAROS indication. If the PAPI continues to flash or pulse, the pilot must execute an immediate “go around” and contact ATC at the earliest possible opportunity.

f. Pilot Actions:

1. When operating at airports with RWSL, pilots will operate with the transponder “On" when departing the gate or parking area until it is shutdown upon arrival at the gate or parking area. This ensures interaction with the FAA surveillance systems which provide information to the RWSL system.

2. Pilots must always inform the ATCT when they have either stopped, are verifying a landing clearance, or are executing a missed approach due to RWSL or FAROS indication that are in conflict with ATC instructions. Pilots must request clarification of the taxi, takeoff, or landing clearance.

3. Never cross over illuminated red lights. Under normal circumstances, RWSL will confirm the pilot's taxi or takeoff clearance. If RWSL indicates that it is unsafe to takeoff from, land on, cross, or enter a runway, immediately notify ATC of the conflict and confirm your clearance. Never land if PAPI continues to flash or pulse. Execute a go around and notify ATC.

4. Do not proceed when lights have extinguished without an ATC clearance. RWSL verifies an ATC clearance; it does not substitute for an ATC clearance.

g. ATC Control of RWSL System:

1. Controllers can set in-pavement lights to one of five (5) brightness levels to assure maximum conspicuity under all visibility and lighting conditions. REL, THL, and RIL subsystems may be independently set.

2. The system can be shutdown should RWSL operations impact the efficient movement of air traffic or contribute, in the opinion of the ATC Supervisor, to unsafe operations. REL, THL, RIL, and FAROS subsystems may be shutdown separately. Shutdown of the FAROS subsystem will not extinguish PAPI lights or impact its glide path function. Whenever the system or a component is shutdown, a NOTAM must be issued, and the Automatic Terminal Information System (ATIS) must be updated.

1. Operating Characteristics - Departing Aircraft:

When a departing aircraft reaches 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 a REL equipped taxiway intersection, the lights at that intersection extinguish approximately 2 to 3 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 lights will extinguish.

2. Operating Characteristics - Arriving Aircraft:

When an aircraft on final approach is approximately 1 mile from the runway threshold all sets of REL light arrays along the runway will illuminate. The distance is adjustable and can be configured for specific operations at particular airports. Lights extinguish at each equipped taxiway intersection approximately 2 to 3 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 REL illumination and extinguishing 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. Whenever a pilot observes the red lights of the REL, that pilot will stop at the hold line, or along the taxiway path and 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 (i.e., 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 opportunity.

c. Takeoff Hold Lights (THL): The THL system is composed of in-pavement, unidirectional fixtures in a double longitudinal row aligned either side of the runway centerline lighting. Fixtures are focused toward the arrival end of the runway at the “position and hold" point, and they extend for 1,500 feet in front of the holding aircraft (see FIG 2-1-9). Illuminated red lights provide a signal, to an aircraft in position for takeoff or rolling, that it is unsafe to takeoff because the runway is occupied or about to be occupied by another aircraft or ground vehicle. Two aircraft, or a surface vehicle and an aircraft, are required for the lights to illuminate. The departing aircraft must be in position for takeoff or beginning takeoff roll. Another aircraft or a surface vehicle must be on or about to cross the runway.

1. Operating Characteristics - Departing Aircraft:

THLs will illuminate for an aircraft in position for departure or departing when there is another aircraft or vehicle on the runway or about to enter the runway (see FIG 2-1-9.) Once that aircraft or vehicle exits the runway, the THLs extinguish. A pilot may notice lights extinguish prior to the downfield aircraft or vehicle being completely clear of the runway but still moving. Like RELs, THLs have an “anticipated separation" feature.

NOTE - When the THLs extinguish, this is not clearance to begin a takeoff roll. All takeoff clearances will be issued by ATC.

2. What a pilot would observe: A pilot in position to depart from a runway, or has begun takeoff roll, will observe THL illumination in reaction to an aircraft or vehicle on the runway or about to enter or cross it. Lights will extinguish when the runway is clear. A pilot may observe several cycles of illumination and extinguishing depending on the amount of crossing traffic.

3. Whenever a pilot observes the red lights of the THLs, the pilot will stop or remain stopped. The pilot will contact ATC for resolution if any clearance is in conflict with the lights. Should pilots note illuminated lights while in takeoff roll and under circumstances when stopping is impractical for safety reasons, the crew should proceed according to their best judgment while understanding the illuminated lights indicate that continuing the takeoff is unsafe. Contact ATC at the earliest possible opportunity.

d. The Final Approach Runway Occupancy Signal (FAROS) is activated by flashing of the Precision Approach Path Indicator (PAPI) (see FIG 2­1­9). When activated, the light fixtures of the PAPI flash or pulse to indicate to the pilot on an approach that the runway is occupied and that it may be unsafe to land.

1. Operating Characteristics:

If an aircraft or surface vehicle occupies a FAROS equipped runway, the PAPI(s) on that runway will flash or pulse. The glide path indication will not be affected, and the allotment of red and white PAPI lights observed by the pilot on approach will not change. Some FAROS systems will flash or pulse the PAPI when traffic enters the runway whether or not there is an aircraft on approach. Others will flash the PAPI only if there is an aircraft on approach and within 1.5 nautical miles of the landing threshold.

2. What a pilot would observe: A pilot on approach to the runway will observe the PAPI flash or pulse if there is traffic on the runway and will notice the PAPI ceases to flash or pulse when the traffic moves outside the hold short lines for the runway.

3. Whenever a pilot observes a flashing or pulsing PAPI, the pilot will verify the FAROS activation. At 500 feet above ground level (AGL), the pilot must look for and acquire the traffic on the runway. At 300 feet AGL, the pilot must contact ATC for resolution if the clearance is in conflict with the FAROS indication. If the PAPI continues to flash or pulse, the pilot must execute an immediate “go around” and contact ATC at the earliest possible opportunity.

e. Pilot Actions:

1. When operating at airports with RWSL, pilots will operate with the transponder “On" when departing the gate or parking area until it is shutdown upon arrival at the gate or parking area. This ensures interaction with the FAA surveillance systems which provide information to the RWSL system.

2. Pilots must always inform the ATCT when they have either stopped, are verifying a landing clearance, or are executing a missed approach due to RWSL or FAROS indication that are in conflict with ATC instructions. Pilots must request clarification of the taxi, takeoff, or landing clearance.

3. Never cross over illuminated red lights. Under normal circumstances, RWSL will confirm the pilot's taxi or takeoff clearance. If RWSL indicates that it is unsafe to takeoff from or taxi across a runway, immediately notify ATC of the conflict and confirm your clearance. Never land if PAPI continues to flash or pulse. Execute a go around and notify ATC.

4. Do not proceed when lights have extinguished without an ATC clearance. RWSL verifies an ATC clearance, it does not substitute for an ATC clearance.

f. ATC Control of RWSL System:

1. Controllers can set in-pavement lights to one of five (5) brightness levels to assure maximum conspicuity under all visibility and lighting conditions. REL and THL subsystems may be independently set.

2. The system can be shutdown should RWSL operations impact the efficient movement of air traffic or contribute, in the opinion of the ATC Supervisor, to unsafe operations. REL, THL, and FAROS subsystems may be shutdown separately. Shutdown of the FAROS subsystem will not extinguish PAPI lights or impact its glide path function. Whenever the system or a component is shutdown, a NOTAM must be issued, and the Automatic Terminal Information System (ATIS) must be updated.

Aeronautical Information Manual (AIM) — Chapter 2
2-1-1 - 2-1-2 - 2-1-3 - 2-1-4 - 2-1-5 - 2-1-6 - 2-1-7 - 2-1-8 - 2-1-9 - 2-1-10 - 2-2-1 - 2-2-2 - 2-2-3 - 2-3-1 - 2-3-2 - 2-3-3 - 2-3-4 - 2-3-5 - 2-3-6 - 2-3-7 - 2-3-8 - 2-3-9 - 2-3-10 - 2-3-11 - 2-3-12 - 2-3-13 - 2-3-14 - 2-3-15