Airspace, ground and the difference between them

Airspace is a volume, and the map that shows it is a plan view of volumes rather than of land. Above the United Kingdom the sky is divided into classes, with controlled airspace descending to the surface around the busiest aerodromes and rising in steps around others, and a hobby flight at low level passes in and out of it without anything on the ground marking the boundary. Overlaid on that are restrictions of a different kind: flight restriction zones around protected aerodromes, permanent restricted areas over certain sites, and temporary restrictions raised for an event and then withdrawn.

The ground is a different subject with a different owner. A landowner, a local authority, a national park authority or a body that admits the public to its land can restrict taking off and landing on that land, through byelaws or through the conditions of entry. That restriction bites on the launch and the recovery, not on the air. The practical result is the rule that catches most people out: a restriction is usually about the air above the ground rather than about the ground itself, and where it is about the ground it is about the ground only. A field you may stand in can sit under airspace you may not enter, and airspace with nothing in it can sit above a car park whose owner forbids launching from the tarmac.

Which of these falls on you

The airspace requirements fall on the person at the controls. It is the flyer who is answerable for where the aircraft goes, not the person whose name is on the operator registration and not the owner of the field. Somebody who borrows a machine for an afternoon takes on the whole of that responsibility for the afternoon, and the requirement does not divide between two people simply because two people are present. The identifiers each of them may need are a separate matter, dealt with under The drone licence question.

The separation distances fall on the flyer as well, and they are measured from the aircraft rather than from where the pilot is standing. The requirements set a distance to be kept from people who are not involved in the flight, and a larger distance from crowds and from residential, commercial, industrial and recreational areas. The exact figures depend on the weight of the aircraft, read against the 250 gram boundary, and on its class marking, so a flyer who has learned one number has learned the number for one machine. The CAA publishes the current set, and the height ceiling that sits above all of it is 400 feet, which is 120 metres, measured above the surface.

What checking a place asks of you, in order

Checking a place asks for a short sequence, run in the order below, and it takes a couple of minutes once it is familiar.

1. Look up the take-off point on a published airspace map before leaving the house, rather than at the field.
2. Read what sits above it: the class of airspace, any flight restriction zone, any restricted area and any temporary restriction in force that day.
3. Establish who owns or manages the land you intend to launch from, and whether that body permits it.
4. Walk the site on arrival and note where uninvolved people are, where they are likely to appear, and what stands up out of the ground: masts, cables, trees and buildings.
5. Fix a working ceiling and a working boundary for yourself, both inside the published limits, and fly to those rather than to the limits.
6. Keep the aircraft in unaided sight throughout, since every distance limit above assumes you can see where it is.

The maps themselves are the part readers most often ask about. The CAA publishes airspace restriction information, and NATS, the United Kingdom air navigation service provider, publishes a drone map and an app called Drone Assist that presents restrictions and ground hazards on a phone. Both are references rather than permissions: a green area on a screen tells you what the airspace is, not that a particular flight is acceptable, and neither of them knows who owns the field.

The places where none of this applies as expected

Indoors, the airspace requirements do not apply in the way people expect, because an aircraft inside a building is not in the open air at all. A sports hall or a large room is the one setting where the separation distances and the ceiling stop being the governing constraint and the walls take over. That is why the smallest machines, the ones under 250 grams, are so often flown indoors while a flyer learns the controls.

National parks are the mirror case, and they are frequently misunderstood in the other direction. A national park is not a no fly zone as a class. The land inside one belongs to many different owners, and access authorities and bodies such as the National Trust apply their own restrictions on taking off and landing on the land they hold. So the answer for a given spot inside a national park is a landowner answer, sometimes yes and sometimes no, sitting underneath whatever the airspace above happens to be. Learning to fly a drone in the UK is far easier at a model flying site or an open recreation ground where the landowner question has a plain answer.

Finally, none of this reaches beyond the United Kingdom. Other countries divide their airspace differently, set different distances and publish their own maps, and a UK check tells you nothing about a holiday flight abroad.

The misreadings that cause the most trouble

The first misreading is that a no fly zone can be flown in if the aircraft is small enough or low enough. It cannot, and the question "how to fly a drone in a no fly zone" has no technique behind it: a flight restriction zone around an aerodrome is a restriction on the volume, and permission for a flight inside one is a matter for the aerodrome and the CAA scheme rather than for a setting on a controller. Machines from the larger manufacturers refuse to arm or to climb in some of these areas, and readers occasionally take that geofencing as the definition of the rule. It is not: the software is a manufacturer's own approximation, it lags the published maps, and its absence is not permission.

The second is treating an app as authority. A map on a phone is a rendering of information published elsewhere, made at some moment before you opened it. The third is assuming that permission from a landowner settles the airspace question, or that clear airspace settles the landowner question. They are independent, and both have to come out right. The UK rules, in order sets out how this question sits among the others, and Insurance covers what happens when a flight goes wrong over somebody else's property.

Has the field you have in mind actually been checked?

To work out whether a particular field is flyable, run the three checks separately and in this order: what is the airspace above it, who manages the land under it, and where will uninvolved people be while the aircraft is up. If any of the three has no clear answer, the honest position is that the place has not been checked rather than that it is clear. Then weigh the aircraft against the 250 gram boundary and read its class marking, because the separation distances that apply to it follow from those two attributes.

Those checks tell you what to ask. They do not settle a particular flight, and this page describes what the airspace and distance requirements are about rather than interpreting them for any one site or offering legal advice. The Civil Aviation Authority publishes the airspace and separation requirements for this kind of flying, the CAA amends them and airspace itself is redrawn, so the CAA's own pages carry the version that describes the position today.

Where to go next

RULESThe UK rules, in orderWhat the law asks of a hobby flyerRULESThe drone licence questionDo you need a drone licence in the UK?RULESInsuranceWho needs cover and why