How the rules are structured

Why a self-built drone is treated differently

Class marks, the C0 to C4 labels, are issued against a manufacturer's conformity assessment. An aircraft you assembled yourself has not been through one and cannot carry a class mark, so the rules that key off those marks do not apply to it in the way they apply to a shop-bought drone.

This is the fact no component retailer mentions at checkout, and it puts most self-built aircraft into A3, the most restrictive subcategory of the EU Open category: at least 150 m from residential, commercial, industrial and recreational areas.

There is a narrow exception in the regulation for a privately built aircraft under 250 g that is also incapable of exceeding 19 m/s, about 68 km/h. Both conditions, not just the weight. Most FPV aircraft pass 19 m/s easily, and maximum speed is almost never published, so the honest answer for most builds is that it cannot be determined from recorded specifications. That is more useful than it sounds: it tells you that staying under 250 g is only half of the requirement.

Registration follows the camera, not the weight

"Under 250 g means no paperwork" is widely repeated and false for FPV. Operator registration is generally required if the aircraft weighs 250 g or more OR carries a camera or other sensor able to capture personal data.

Essentially every FPV build has a camera. So essentially every FPV build needs the operator registration, regardless of how light it is, and the operator number has to be marked on the aircraft.

Goggles change who has to be present

The camera feed does not satisfy the requirement to keep the aircraft in sight. Flying in goggles under the Open category requires a second person standing with you as an unmanned-aircraft observer, keeping unaided visual contact and able to warn you without technical aids.

This attaches to the build rather than to any one component: it becomes true the moment the build contains goggles. Some countries have begun to diverge from it, which is exactly why this is scoped to the country you select rather than stated once for everyone.

The three subcategories of the Open category

Where you may fly, and what the pilot needs. The class mark on the aircraft decides which of these it can be used in.

The class marks, for the aircraft that carry them

These apply to manufactured drones. A self-built aircraft has no class mark at all.

Transmitter power is a separate question again

Video transmitter output is limited by radio regulations rather than aviation ones, and the limits differ sharply by region. The figure that governs a legal setting in one country will be well under what hardware sold in another is capable of, and most transmitters ship able to exceed their local limit.

This is a setting rather than a purchase in most cases: the same transmitter is legal or not depending on what it is turned down to. Buildlas reports it against the country you choose for that reason.