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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.
VFR requires a pilot to be able to see outside the cockpit to control the aircraft's altitude, navigate, and avoid obstacles and other aircraft. [3] Governing agencies establish specific requirements for VFR flight, including minimum visibility, and distance from clouds, to ensure that aircraft operating under VFR are visible from enough distance to ensure safety.
The aircraft need not necessarily be equipped for flight under IFR, and the aircraft must remain clear of clouds with the surface in sight, and maintain a certain flight visibility minimum (1,500 metres according to ICAO, one statute mile in the US, 1,500 m visibility, in sight of surface and clear of cloud in Europe). The pilot continues to be ...
With good visibility, pilots can determine the aircraft attitude by utilising visual cues from outside the aircraft, most significantly the horizon.Without such external visual cues, pilots may be subject to sensory illusions and must use an alternative reference for the attitude, which is usually provided by gyroscopically-driven instruments such as the attitude indicator ("artificial horizon").
The international definition of fog is a visibility of less than 1 km (3,300 ft); mist is a visibility of between 1 km (0.62 mi) and 2 km (1.2 mi) and haze from 2 km (1.2 mi) to 5 km (3.1 mi). Fog and mist are generally assumed to be composed principally of water droplets, haze and smoke can be of smaller particle size.
The minimum weather conditions for ceiling and visibility for VFR flights are defined in FAR Part 91.155, and vary depending on the type of airspace in which the aircraft is operating, and on whether the flight is conducted during daytime or nighttime.
An aircraft approach category is a grouping which differentiates aircraft based on the speed at which the aircraft approaches a runway for landing. They are used to determine airspace, obstacle clearance and visibility requirements for instrument approaches . [ 1 ] :
A pilot's view of Lisbon Airport's runway 21 in fog; runway visual range is about 200 m (660 ft). In aviation, the runway visual range (RVR) is the distance over which a pilot of an aircraft on the centreline of the runway can see the runway surface markings delineating the runway or the lights delineating the runway or identifying its centre line.