8/15/19 1/30/20  Pilot/Controller Glossary Pilot/Controller Glossary  9.  ODALS- Omnidirectional Approach Light- ing System consists of seven omnidirectional  flashing lights located in the approach area of a  nonprecision runway. Five lights are located on the  runway centerline extended with the first light  located 300 feet from the threshold and extending at  equal intervals up to 1,500 feet from the threshold.  The other two lights are located, one on each side of  the runway threshold, at a lateral distance of 40 feet  from the runway edge, or 75 feet from the runway  edge when installed on a runway equipped with a  VA S I .  (Refer to FAA Order JO 6850.2, VISUAL  GUIDANCE LIGHTING SYSTEMS.)  b.  Runway Lights/Runway Edge Lights- Lights  having a prescribed angle of emission used to define  the lateral limits of a runway. Runway lights are  uniformly spaced at intervals of approximately 200  feet, and the intensity may be controlled or preset.  c.  Touchdown Zone Lighting- Two rows of  transverse light bars located symmetrically about the  runway centerline normally at 100 foot intervals. The  basic system extends 3,000 feet along the runway.  d.  Runway Centerline Lighting- Flush centerline  lights spaced at 50-foot intervals beginning 75 feet  from the landing threshold and extending to within 75  feet of the opposite end of the runway.  e.  Threshold Lights- Fixed green lights arranged  symmetrically left and right of the runway centerline,  identifying the runway threshold.  f.  Runway End Identifier Lights (REIL)- Two  synchronized flashing lights, one on each side of the  runway threshold, which provide rapid and positive  identification of the approach end of a particular  runway.  g.  Visual Approach Slope Indicator (VASI)- An  airport lighting facility providing vertical visual  approach slope guidance to aircraft during approach  to landing by radiating a directional pattern of high  intensity red and white focused light beams which  indicate to the pilot that he/she is “on path” if he/she  sees red/white, “above path” if white/white, and  “below path” if red/red. Some airports serving large  aircraft have three-bar VASIs which provide two  visual glide paths to the same runway.  h.  Precision Approach Path Indicator (PAPI)- An  airport lighting facility, similar to VASI, providing  vertical approach slope guidance to aircraft during  approach to landing. PAPIs consist of a single row of  either two or four lights, normally installed on the left  side of the runway, and have an effective visual range  of about 5 miles during the day and up to 20 miles at  night. PAPIs radiate a directional pattern of high  intensity red and white focused light beams which  indicate that the pilot is “on path” if the pilot sees an  equal number of white lights and red lights, with  white to the left of the red; “above path” if the pilot  sees more white than red lights; and “below path” if  the pilot sees more red than white lights.  i.  Boundary Lights- Lights defining the perimeter  of an airport or landing area.  (Refer to AIM.)  AIRPORT MARKING AIDS- Markings used on  runway and taxiway surfaces to identify a specific  runway, a runway threshold, a centerline, a hold line,  etc. A runway should be marked in accordance with  its present usage such as:  a.  Visual.  b.  Nonprecision instrument.  c.  Precision instrument.  (Refer to AIM.)  AIRPORT REFERENCE POINT (ARP)- The  approximate geometric center of all usable runway  surfaces.  AIRPORT RESERVATION OFFICE- Office  responsible for monitoring the operation of slot  controlled airports. It receives and processes requests  for unscheduled operations at slot controlled airports.  AIRPORT ROTATING BEACON- A visual  NAVAID operated at many airports. At civil airports,  alternating white and green flashes indicate the  location of the airport. At military airports, the  beacons flash alternately white and green, but are  differentiated from civil beacons by dualpeaked (two  quick) white flashes between the green flashes.  AIRPORT STREAM FILTER (ASF)- An on/off  filter that allows the conflict notification function to  be inhibited for arrival streams into single or multiple  airports to prevent nuisance alerts.  AIRPORT SURFACE DETECTION EQUIPMENT  (ASDE)- Surveillance equipment specifically de- signed to detect aircraft, vehicular traffic, and other  objects, on the surface of an airport, and to present the  PCG A-8  (See INSTRUMENT FLIGHT RULES.)  (See SPECIAL VFR OPERATIONS.)  (See ICAO term AERODROME BEACON.)  (Refer to AIM.) 