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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.
The Canadian rules specify that an aircraft may be operated in VFR OTT flight during the cruise portion of the flight during the day, at a vertical distance from clouds of at least 1000 feet. When the aircraft is operated between two cloud layers, the vertical distance between the layers must be at least 5000 feet.
BKN003 OVC010 indicates a broken (5 ⁄ 8 to 7 ⁄ 8 of the sky covered) cloud layer at 300 ft (91 m) above ground level (AGL) and an overcast (8/8 of the sky covered) layer at 1,000 ft (300 m). M02/M02 indicates the temperature is −2 °C (28 °F) and the dew point is −2 °C (28 °F).
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.
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.
ATC authorization will include a cloud top report and a request to report upon reaching the top; it may also include a clearance limit, routing, and an alternative clearance if VFR-on-top is not reached by a specified altitude. Pilots operating on a VFR-on-top clearance must advise ATC before any altitude change. [2]
However, typical daytime VFR minimums for most airspace is 3 statute miles of flight visibility and a distance from clouds of 500 feet below, 1,000 feet above, and 2,000 feet horizontally. [4] Flight conditions reported as equal to or greater than these VFR minimums are referred to as visual meteorological conditions (VMC).
A pilot's view of the runway just before landing in thick fog at night. In aviation, instrument meteorological conditions (IMC) are weather conditions that require pilots to fly primarily by reference to flight instruments, and therefore under instrument flight rules (IFR), as opposed to flying by outside visual references under visual flight rules (VFR).