Visibility

{
  "id": "MLC-T-AVN-001093",
  "term": "Visibility",
  "field": "Aviation and air traffic control",
  "definition": "The ability, as determined by atmospheric conditions and expressed in units of distance, to see and identify prominent unlighted objects by day and prominent lighted objects by night. Visibility is reported as statute miles, hundreds of feet or meters.\n\na. Flight Visibility- The average forward horizontal distance, from the cockpit of an aircraft in flight, at which prominent unlighted objects may be seen and identified by day and prominent lighted objects may be seen and identified by night.\n\nb. Ground Visibility- Prevailing horizontal visibility near the earth's surface as reported by the United States National Weather Service or an accredited observer.\n\nc. Prevailing Visibility- The greatest horizontal visibility equaled or exceeded throughout at least half the horizon circle which need not necessarily be continuous.\n\nd. Runway Visual Range (RVR)- An instrumentally derived value, based on standard calibrations, that represents the horizontal distance a pilot will see down the runway from the approach end. It is based on the sighting of either high intensity runway lights or on the visual contrast of other targets whichever yields the greater visual range. RVR, in contrast to prevailing or runway visibility, is based on what a pilot in a moving aircraft should see looking down the runway. RVR is horizontal visual range, not slant visual range. It is based on the measurement of a transmissometer made near the touchdown point of the instrument runway and is reported in hundreds of feet. RVR, where available, is used in lieu of prevailing visibility in determining minimums for a particular runway.\n\ne. Touchdown RVR- The RVR visibility readout values obtained from RVR equipment serving the runway touchdown zone.\n\nf. Mid-RVR- The RVR readout values obtained from RVR equipment located midfield of the runway.\n\ng. Rollout RVR- The RVR readout values obtained from RVR equipment located nearest the rollout end of the runway.",
  "synonyms": [
    "Flight visibility",
    "Ground visibility",
    "Mid RVR",
    "Prevailing visibility",
    "Rollout RVR",
    "Runway visual range (RVR)",
    "Touchdown RVR"
  ],
  "see_also": [
    "Flight visibility",
    "Ground visibility",
    "Runway visual range (RVR)",
    "Visibility [ICAO]"
  ],
  "references": [
    "14 CFR part 91",
    "AIM",
    "FAA Pilot/Controller Glossary"
  ],
  "url": "https://mlchart.com/terminology/aviation/visibility/"
}