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Airport Lighting

Introduction:

  • Airport lighting helps the pilot locate and define the runway and airport environment
  • Airport lighting is not continuous at airports with minimal traffic in order to save money when not in use
  • Runway edge lights, in-pavement lights, and sequence flashing lights may also have intensity controls which may be varied to meet the pilots request
  • Airport lighting may be either continuous or variable, depending on traffic/use

Control of Lighting Systems:

  • Operation of approach and runway lighting may be adjusted at the pilot's discretion and is generally controlled by the Air Traffic Control Tower (ATCT)
  • At some locations, where there is no control tower in operation, the local Flight Service Station (FSS) may control the lights
  • Pilots may request and in some cases control lighting themselves
    • 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 but only some sequenced flashing light systems also have intensity control

Pilot Controlled 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 [Figure 1/2]
  • May request lights be turned on or off, and some lights have intensity control to the Air Traffic Control Tower
    • Variable lighting is used to save the city paying for the electricity some money when no one is using the airport
  • Controlled on one frequency, usually CTAF
    • 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
  • The suggested method is to key the mic 7 times regardless to reach high intensity and adjust from there
  • REMEMBER: after 15 minutes the lights turn off, do now allow this to happen while you are on a short final!
  • Airport/Facility Directory (A/FD) or DoD En-route supplement will list information on type, runway, and frequency used
  • 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 IAPs 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
  • 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

Runways Without Approach Lighting
Figure 2: Runways Without Approach Lighting
Runways With Approach Lighting
Figure 1: Runways With Approach Lighting

  • 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
  • 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 REILs which may be turned off when desired by keying the mike 5 or 3 times respectively)
  • 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 [Figure 3]

Radio Control System
Figure 3: Radio Control System

  • 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 IAPs 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

Aeronautical Light Beacons:

  • An aeronautical light beacon is a visual Navigational Aid (NAVAID) displaying flashes of white and/or colored light to indicate the location of an airport, a heliport, a landmark, a certain point of a Federal airway in mountainous terrain, or an obstruction
  • 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
    • Coded flashes of the auxiliary lights, if employed, further identify the beacon site
  • 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:
    • 24-30 flashes per minute for airports, landmarks, and points on federal airways
    • 30-45 flashes per minute for heliports
  • The light used may be a rotating beacon or one or more flashing lights
  • The flashing lights may be supplemented by steady burning lights of lesser intensity
  • The color or color combination displayed by a particular beacon and/or its auxiliary lights tell whether the beacon is indicating a landing place, landmark, point of the Federal airways, or an obstruction
  • Most effective from 1° to 10° above the horizon visible typically at 40nm
  • May be omni-directional capacitor-discharge device or it may rotate at a constant speed providing the visual effect of a flashing light
  • Operation of the beacon during the day may indicate airport conditions are less than VFR
    • Meaning SVFR or IFR is required for takeoff, landings, and flight in the traffic pattern
  • The colors and color combinations of beacons are: [Figure 3]
    • White and Green: Lighted land airport
    • *Green alone: Lighted land airport
    • White and Yellow: Lighted water airport
    • *Yellow alone: Lighted water airport
      • *Green alone or yellow alone is used only in connection with a white-and-green or white-and-yellow beacon display, respectively
    • Green, Yellow, and White: Lighted heliport
  • Military airport beacons flash alternately white and green, but are differentiated from civil beacons by dual-peaked (two quick) white flashes between the green flashes
  • 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 that of VFR (less than 3 miles and/or the ceiling is less than 1,000'
    • 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 while many airports the airport beacon is turned on by a photoelectric cell or time clocks and ATC personnel cannot control them
    • There is no regulatory requirement for daylight operation and so it is the pilot's responsibility to comply with proper preflight planning as required by 14 CFR Section 91.103
  • Code Beacons:

    • Code Beacons are omni-directional lights used to identify airports and landmarks
    • In the case of airports, they flash the 3 or 4 character airport identifier in Morse code 6 to 8 times a minute
      • Green flashes for land airports
      • Yellow for water airports

Various Airport Beacon Patterns
Figure 3: Various Airport Beacon Patterns

Obstruction Lights:

  • Obstructions are marked and lit to warn airmen of their presence during daytime and night-time conditions
  • Aviation Red Obstruction Lights:

    • During daylight hours, aviation orange and white paint is used for marking
    • During nighttime operation, a flashing red light bacon indicates the marking of an en-route obstruction (20 to 40 flashes per minute)
    • Steady red light indicates an obstruction in the terminal area
  • Medium Intensity Flashing White Obstruction Lights:

    • Medium intensity flashing white obstruction lights may be used during daytime and twilight with automatically selected reduced intensity for night-time operation
    • When this system is used on structures 500 feet (153m) AGL or less in height, other methods of marking and lighting the structure may be omitted
      • Aviation orange and white paint is always required for day time marking on structures exceeding 500' AGL
    • Not normally installed on structures less than 200' AGL
  • High Intensity White Obstruction Light:

    • Flashing high intensity white lights during daytime with reduced intensity for twilight and night-time operation
    • When this type of system is used, the marking of structures with red obstruction lights and aviation orange and white paint may be omitted
  • Dual Lighting:
    • A combination of flashing aviation red beacons and steady burning aviation red lights for night time operation, and flashing high intensity white lights for daytime operation
    • Aviation orange and white paint may be omitted
  • Catenary Lighting:

    Catenary Lighting
    Figure 4: Catenary Lighting
    • Lighted markers are available for increased night conspicuity of high-voltage transmission line catenary wires
    • Lighted markers provide conspicuity both day and night
  • Medium intensity omni-directional flashing white lighting system provides conspicuity both day and night on catenary support structures
    • The unique sequential/simultaneous flashing light system alerts pilots of the associated catenary wires
  • High intensity flashing white lights are being used to identify some supporting structures of overhead transmission lines located across rivers, chasms, gorges, etc.
    • These lights flash in a middle, top, lower light sequence at approximately 60 flashes per minute
    • The top light is normally installed near the top of the supporting structure, while the lower light indicates the approximate lower portion of the wire span
    • The lights are beamed toward the companion structure and identify the area of the wire span
  • High intensity flashing white lights are also employed to identify tall structures, such as chimneys and towers, as obstructions to air navigation
    • The lights provide a 360° coverage about the structure at 40 flashes per minute and consist of from one to seven levels of lights depending upon the height of the structure
    • Where more than one level is used the vertical banks flash simultaneously

Runway Status Light (RWSL) System:

  • 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 surface traffic and approach traffic
  • 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
  • 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 operations
  • 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
  • Aircraft will depart the gate or parking area with the transponder "ON" and will leave it there until the flight is terminated
  • ATC can adjust intensity and can turn off the system but that's about it
  • Processes information from surveillance systems and actives 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)
  • Runway Entrance Lights (REL):

    • Flush mounted, in-pavement, unidirectional fixtures that are parallel 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
    • Red indicates high speed traffic on the runway or aircraft on final approaches
    • Operating Characteristics for Departing Aircraft:
      • 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
    • Operating Characteristics for Arriving Aircraft:
      • 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
    • 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
    • Pilot Actions:
      • 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 opportunity
  • Takeoff Hold Lights (THL):

    • Flush mounted, in-pavement, unidirectional light 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. THLs extend for 1,500 feet in front of the holding aircraft starting at a point 375 feet from the departure threshold (see FIG 2−1−13). 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
      • THL 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
        • 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
    • When a pilot observes the red light of the THLs, the pilot should safely stop if it’s feasible or remain stopped. The pilot must 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
  • Runway Intersection Lights (RIL):

    • The RIL system is composed of flush mounted, in−pavement, unidirectional light 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
    • RIL 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 the conflicting traffic passes through the intersection, the RILs extinguish
    • RIL 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 the conflicting traffic passes through the intersection, the RILs extinguish
    • 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
    • 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
  • The Final Approach Runway Occupancy Signal (FAROS):
    • FAROS is communicated by flashing of the Precision Approach Path Indicator (PAPI) (see FIG 2-1-9)
    • 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
      • NOTE−FAROS is an independent automatic alerting system that does not rely on ATC control or input
    • FAROS Operating Characteristics:
      • If an aircraft or surface vehicle occupies a FAROS equipped runway, the PAPI(s) on that runway will flash. 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. The FAROS system will flash the PAPI when traffic enters the runway and there is an aircraft on approach and within 1.5 nautical miles of the landing threshold
    • What a pilot would observe:
      • A pilot on approach to the runway will observe the PAPI flash if there is traffic on the runway and will notice the PAPI ceases to flash when the traffic moves outside the hold short lines for the runway
    • When a pilot observes a flashing PAPI 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 FAROS indication is in conflict with the clearance. If the PAPI continues to flash, the pilot must execute an immediate “go around” and contact ATC at the earliest possible opportunity
  • Pilot Actions:

    • 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 such as ASDE-X which provide information to the RWSL system
    • Pilots must always inform the ATCT when they have either stopped, are verifying a landing clearance, or are executing a go-around due to RWSL or FAROS indication that are in conflict with ATC instructions. Pilots must request clarification of the taxi, takeoff, or landing clearance
    • Never cross over illuminated red lights. Under normal circumstances, RWSL will confirm the pilot’s taxi or takeoff clearance previously issued by ATC. If RWSL indicates that it is unsafe to takeoff from, land on, cross, or enter a runway, immediately notify ATC of the conflict and re-confirm the clearance
    • Do not proceed when lights have extinguished without an ATC clearance. RWSL verifies an ATC clearance; it does not substitute for an ATC clearance
    • Never land if PAPI continues to flash
    • Execute a go around and notify ATC
  • ATC Control of RWSL System:

    • 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
    • System lights can be disabled should RWSL operations impact the efficient movement of air traffic or contribute, in the opinion of the assigned ATC Manager, to unsafe operations. REL, THL, RIL, and FAROS light fixtures may be disabled separately. Disabling of the FAROS subsystem does not extinguish PAPI lights or impact its glide path function. Whenever the system or a component is disabled, a NOTAM must be issued, and the Automatic Terminal Information System (ATIS) must be update

Runway Lights:

  • Threshold Lights:

    • Threshold lights mark the beginning of the landing surface
    • They consist of four or more green lights, two on each side of the runway
  • Runway End Identifier Lights (REIL):

    • Runway End Identifier Lights are installed to provide rapid and positive identification of the approach end of a runway
    • They consists of synchronized flashing lights located laterally on each side of the threshold which may be either omni (facing all areas) or unidirectional (facing the approach area)
    • Helps identify the runway when it is surrounded by other lighting, lacks contrast with surrounding terrain, or during periods of reduced visibility
  • Runway Edge Light Systems:

    • Runway edge lights are used to outline runway edges during darkness or restricted visibility
      • Should define the usable runway area, AC-150
    • Classified by intensity:
      • HIRL: High Intensity Runway Lights
      • MIRL: Medium Intensity Runway Lights
      • LIRL: Low Intensity Runway Lights
    • HIRL and MIRL have variable intensities while LIRL does not
    • The runway edge lights are white except on instrument runways, yellow replaces white on the last 2,000' or half, whichever is less, to form a caution zone for landings
    • 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
  • In-Runway Lighting:

    • Runway Centerline Lighting System:

      • Runway Centerline Lighting Systems (RCLS') are installed on some precision approach runways to facilitate landing under adverse visibility conditions
      • RCLS are spaced at 50' intervals along the centerline markings, offset to the side of the centerline closest the terminals
      • When viewed from the landing threshold, the runway centerline lights are white until the last 3,000' when they alternate red and white for 2,000' and eventually red at 1,000'
    • Touchdown Zone Lights (TDZL):

      • Installed on some precision approach runways to indicate the touchdown zone during adverse visibility
      • TDZLs consists of two rows of transverse light bars disposed symmetrically about the runway centerline
      • Steady burning white lights, which start 100' beyond the landing threshold, extend to 3,000' or half the runway length, whichever is less
    • Taxiway Lead-Off Lights:

      • Installed to 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
    • Taxiway Lead-On Lights:

      • Installed to provide visual guidance to persons entering 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 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
    • Land and Hold Short Lights:

      • Used to indicate the hold short point for certain runways where Land and Hold Short Operations are approved
      • Consist of a row of pulsating white lights installed across the runway at the hold short point
      • They will be on any time LAHSO are in effect, but off when not in effect

Taxiway Lights:

  • Taxiway Edge Lights:

    • Outline edges of taxiways during periods of darkness or restricted visibility
    • They are omni-directional blue lights [Figure 5]
    • At some airports they may be adjusted at the pilots request or when deemed necessary by the controller
Taxiway Lighting
Figure 5: Taxiway Lighting
  • Taxi Centerline Lights:

    • Facilitate ground traffic under low visibility conditions by illuminating the taxiway centerline
    • 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
    • Steady burning green light [Figure 5]
  • Clearance Bar Lights:

    • Installed at holding positions to increase visibility of the holding position
    • They may also be installed to indicate the location of an intersecting taxiway during periods of darkness
    • Consists of three in-pavement steady burning yellow lights
  • Runway Guard Lights:

    • Runway guard lights are installed at taxiway/runway intersections
    • Enhances visibility of taxiway/runway intersections during reduced visibility
    • Consists of either a pair of elevated flashing yellow lights on either side of the taxiway or a row of in-pavement yellow lights across the entire taxiway, at the runway holding marking
    • Some airports may have a row of three or five in-pavement yellow lights installed at taxiway/runway intersections which should not be confused with clearance bar lights described above
  • Stop Bar Lights:

    • Used to confirm ATC clearance to enter or cross the active runway during periods of low visibility (below 1,200 ft Runway Visual Range)
    • Consists of a row of red, unidirectional, steady in-pavement lights installed across the taxiway at the runway holding position and elevated steady burning red lights on each side
    • Operated in conjunction with the taxiway centerline lead-on lights which extended 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 lights reset automatically by a sensor or backup timer
    • Pilots should never cross a red illuminated stop bar even if cleared
    • If after crossing a stop bar, the taxiway lead-on lights inadvertently extinguish, pilots should hold their position and contact ATC

Approach Lighting System (ALS):

  • The ALS provides the basic means to transition from instrument flight to visual flight for landing [Figure 5]
  • Configuration of signal lights starting at the threshold and extending into the approach area [Figure 2]
    • 2,400-3000' for a precision, instrument runway
    • 1,400-1,500' for a non-precision, instrument runway
  • Some of these systems include sequenced flashing lights, which appear to the pilot as a ball of light traveling toward the runway at high speed (twice a second)
  • Instrument approaches can be continued if red side row bars or red terminating bars are visible (ALSF 1 and 2)

Approach Light Systems
Figure 5: Approach Light Systems

Conclusion:

  • Operational requirements dictate the sophistication and configuration of the approach light system for a particular runway

References: