To fly Visual Flight Rules (VFR), you must be flying in Visual Meteorological Conditions (VMC).
Yet while VFR is typically wrapped up into a quick statement like: ‘Able to see the ground’. Visual Meteorological Conditions vary.
Airspace
Airspace is broken up into a number of categories (A to G).
The type of airspace dictates if you’re allowed to fly VFR at all and if so, what visibility you must have both horizontally and vertically.
So for example, VFR flight in Class A airspace is not permitted.
Class C..E airspace: Requires 5km forward visibility, 1500m horizontal and 1000ft vertically from cloud (below FL100 [~10,000ft subject to air pressure]).
Class F..G airspace: Below FL100 and Above 3000ft Above Mean Sea Level (amls), Requires 5km forward visibility, 1500m horizontal and 1000ft vertical from clouds. Below 3000ft amls & 140knots indicated air speed, you need the same forward visibility but be insight of the surface and free of cloud (i.e. no clouds).
* Class B airspace in the UK is only allocated above FL245, outside of the ceiling range of aircraft like Cessna’s so you don’t need to worry about it.
Eight, Five and Three….
The visibility rules are fairly straight forward because in almost all airspace the distances group into sets. Above FL100 you need Eight kilometres of forward visibility. At all times you need at least five kilometres forward visibility. Above three thousand feet you need 1000ft vertical height from cloud, 1500ft horizontal, below it you need to be clear of cloud.
….The exceptions to this are Class A and Class B airspace, you can’t fly in either. Eight and Five still apply, but if you could fly there you’d need to be clear of cloud.
Radio Contact
An aircraft cannot fly in Class B, C or D airspace during the notified periods of Air Traffic Control operation until the pilot has obtained an air traffic clearance to do so. While in the airspace the pilot must listen to the appropriate radio frequency and comply with ATC requests wherever able to do so – therefore the plane must have a working radio (and the pilot must hold a license to use it [or be ‘permitted’ to use the radio]).
In Class E, F and G airspace, radio contact with air traffic control is not mandatory outside of Aerodrome Traffic Zones (ATZ’s).
It is worth noting that the pilot is responsible for keeping his/her plane flying legally, so while Air Traffic Control can request you to do something in controlled air space, if this would stop you from flying in VFR/VMC conditions, it is the pilots responsibility to say they cannot comply with the request.
Special VFR
…..The get out for how to fly into an aerodrome that is within a Class A control zone (i.e. London). And something for another post.