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. They are the opposite of instrument meteorological conditions (IMC). The boundary criteria between IMC and VMC are known as the VMC minima and are defined by: visibility, cloud ceilings (for takeoffs and landings), and cloud clearances.
The exact requirements vary by type of airspace, whether it is day or night (for countries that permit night VFR), and from country to country. Typical visibility requirements vary from one statute mile to five statute miles (many countries define these in metric units as 1,500 m to 8 km). Typical cloud clearance requirements vary from merely remaining clear of clouds to remaining at least one mile away (1,500 m in some countries) from clouds horizontally and 1,000 feet away from clouds vertically. For instance, in Australia, VMC minima outside controlled airspace are clear of cloud with 5,000 m visibility below 3,000 ft AMSL or 1,000 ft AGL (whichever is higher), and 1,000 ft vertical/1,500 m horizontal separation from cloud above these altitudes or in controlled airspace. Above 10,000 ft, 8,000 m visibility is required to maintain VMC. Air traffic control may also issue a "special VFR" clearance to VFR aircraft, to allow departure from a control zone in less than VMC – this reduces the visibility minimum to 1,600 m.
Generally, VMC requires greater visibility and cloud clearance in controlled airspace than in uncontrolled airspace. In uncontrolled airspace there is less risk of a VFR aircraft colliding with an instrument flight rules (IFR) aircraft emerging from a cloud, so aircraft are permitted to fly closer to clouds. An exception to this rule is class B airspace, in which ATC separates VFR traffic from all other traffic (VFR or IFR), which is why in class B airspace lower cloud clearance is permitted.
The following minima apply in Europe and the UK.
At and above FL 100:
8 km flight visibility, 1500 m horizontally from cloud, 1000 ft (300m) vertically from cloudBelow FL 100:
5 km flight visibility, 1500 m horizontally from cloud, 1000 ft (300m) vertically from cloudAt or below 3,000 ft:
5 km flight visibility, clear of cloud and in sight of the surface
or, for an aircraft, other than a helicopter, operating at 140 kt or less:
1,500 m flight visibility, clear of cloud and in sight of the surface
For helicopters:
Clear of cloud and in sight of the surface at a speed which is commensurate with the visibility.[1]
At and above FL 100:
8 km flight visibility, 1,500 m horizontally from cloud, 1,000 ft (300m) vertically from cloudBelow FL 100:
5 km flight visibility, 1,500 m horizontally from cloud, 1,000 ft (300m) vertically from cloudAlternatively at or below 3,000 and operating at 140kt or less ft:
For helicopters:
Clear of cloud and in sight of surface with a flight visibility of 1500m
At and above FL 100:
8 km flight visibility, 1,500 m horizontally from cloud, 1,000 ft (300m) vertically from cloudBelow FL 100:
5 km flight visibility, 1,500 m horizontally from cloud, 1,000 ft (300m) vertically from cloud[1]
Day: Clear of Cloud. 2 statute miles for fixed wing, 1 statute mile for helicopter
Night: Clear of Cloud. 3 statute miles visibility.
Day: 2000 feet horizontally, 500 feet vertically from cloud. 1 statute mile visibility
Night: 2000 feet horizontally, 500 feet vertically from cloud. 3 statute miles visibility
1 mile horizontally, 500 feet vertically from cloud. 3 statute miles visibility.[3]
Maintain at least 500 feet AGL except when taking off or landing.[4]
VFR flight prohibited in Class A airspace.
United States Visual Flight Rules are provided in Title 14 of the Code of Federal Regulations, Part 91, Section 155:
| Airspace class | Time | Altitude | |||||||
|---|---|---|---|---|---|---|---|---|---|
| Surface to 1200 feet AGL | 1200 feet AGL to 10,000 feet MSL | 1200 feet AGL and above 10,000 feet MSL | |||||||
| Visibility | Clearance from clouds | Visibility | Clearance from clouds | Visibility | Clearance from clouds | ||||
| G | Day | 1 | clear of clouds | 1 | 500 below, 1000 above, 2000 horizontally | 5 | 1000 below, 1000 above, 1 SM horizontally | ||
| Night | 3 | 500 below, 1000 above, 2000 horizontally | 3 | 500 below, 1000 above, 2000 horizontally | |||||
| Airspace class | Time | Altitude | |||||||
| Below 10,000 feet MSL | At or above 10,000 feet MSL | ||||||||
| Visibility | Clearance from clouds | Visibility | Clearance from clouds | ||||||
| E | Day or night | 3 | 500 below, 1000 above, 2000 horizontally | 5 | 1000 below, 1000 above, 1 SM horizontally | ||||
| Airspace class | Time | Any altitude | |||||||
| Visibility | Clearance from clouds | ||||||||
| D | Day or night | 3 | 500 below, 1000 above, 2000 horizontally | ||||||
| C | |||||||||
| B | Clear of clouds | ||||||||
| A | Prohibited | ||||||||