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VFR / VMC visibility requirements in the US. In aviation, visual meteorological conditions (VMC) is an aviation flight category in which visual flight rules (VFR) flight is permitted—that is, conditions in which pilots have sufficient visibility to fly the aircraft maintaining visual separation from terrain and other aircraft.
[1] In some countries pilots are required to get an air traffic control (ATC) clearance, or in absence of a controller, advise the nearest flight service station or center. Pilots are required to adhere to VFR minima when climbing and descending over the clouds. Flight in cloud is not permitted. [1]
Under visual meteorological conditions, the minimum visual range, distance from clouds, or cloud clearance requirements to be maintained above ground vary by jurisdiction, and may also vary according to the airspace in which the aircraft is operating. [4] In some countries, VFR flight is permitted at night, and is known as night VFR.
ii. Broken down into geographical areas, and/or states; iii. Describes cloud and weather affecting VFR flight operations, including precipitation, thunderstorms, and sustained surface winds 20 Kts or greater. Also includes visibility when the forecast to visibility is between 3 and 6 SM and/or obstructions to visibility
"Few" = 1–2 oktas SCT "Scattered" = 3–4 oktas BKN "Broken" = 5–7 oktas OVC "Overcast" = 8 oktas, i.e., full cloud coverage TCU Towering cumulus cloud, e.g., SCT016TCU CB Cumulonimbus cloud, e.g., FEW015CB VV "Vertical visibility" = clouds cannot be seen because of fog or heavy precipitation, so vertical visibility is given instead.
The height above the ground or water of the base of the lowest layer of cloud below 6000 meters (20,000 feet) covering more than half the sky. [2] United Kingdom The vertical distance from the elevation of an aerodrome to the lowest part of any cloud visible from the aerodrome which is sufficient to obscure more than half of the sky. [3] United ...
Cloud-cover symbols used on weather teleprinters and aviation reports in the US [6] In the early 20th century, it was common for weather maps to be hand drawn. The symbols for cloud cover on these maps, like the modern symbols, were drawn inside the circle marking the position of the weather station making the measurements.
The sectionals are complemented by terminal area charts (TACs) at 1:250,000 scale for the areas around major U.S. airports, and until 2016 by World Aeronautical Charts (WACs) at a scale of 1:1,000,000 for pilots of slower aircraft and aircraft at high altitude. [1] Since February 2021, the charts have been updated on a 56-day publication cycle. [2]