VLOS, EVLOS and BVLOS drone flights: what they are and how they differ

What you can do with a drone is limited by the type of flight you are allowed to carry out. Those limits break down into three different kinds of flight, each with its own requirements — both for the aircraft and for the pilot’s qualifications.

Below is what each of the three permitted flight modes involves and the conditions that govern them.

Types of drone flight

There are essentially three variants, and what separates them is the maximum distance the drone may fly from the pilot’s position. They are:

• VLOS.
• EVLOS.
• BVLOS.

Each takes its name from an English acronym, and they differ both in distance and in how the operation is run.

VLOS drone flights

The first and by far the most common is VLOS, from “Visual Line of Sight”: flights carried out within the pilot’s visual range.

VLOS operations cover most classes of drone across the different categories and, as a general rule, are flown up to a maximum of 500 metres from the pilot’s position.

As the name says, the drone must stay in sight at all times, without the pilot needing distance-viewing or magnifying equipment to make it out (ordinary prescription glasses are fine). If the pilot cannot maintain that visual contact, the working area has to shrink.

External conditions count here too. Fog, or natural and man-made obstacles, can cut that maximum range down considerably. The rule does not bend: the drone stays inside the pilot’s field of view.

EVLOS drone flights

There is a second mode that extends the visual range so you can operate beyond 500 metres. It is called EVLOS (Extended Visual Line of Sight), and it works by extending the pilot’s field of view through assisting observers.

Each observer may monitor the drone up to a maximum of 500 metres from their own position. So if observers are spaced 500 metres apart, the working range can be extended to 1,000 or 2,000 metres.

Every observer taking part has to keep frequent, active radio contact with the pilot to report how the drone is behaving throughout the flight.

For this to be lawful, the observers must be trained and hold professional drone pilot accreditation (see our drone pilot courses) in line with what AESA requires, so that they know how to fly a drone properly.

BVLOS drone flights

The third mode is BVLOS, “Beyond Visual Line of Sight”, which means exactly that: past the pilot’s field of view. Here the pilot does not keep direct visual contact with the aircraft; it is flown from a remote control station.

This is the most demanding of the three and it takes serious professional preparation. The aircraft also has to carry equipment that makes safe flight possible without anyone watching it directly. Drones used for BVLOS must therefore meet the following conditions:

• They may only be flown with drones up to 2 kg MTOW.
• They must carry systems that detect other aircraft, people on the ground and obstacles.
• They must be fitted with a forward-facing camera so the pilot can keep the aircraft correctly oriented.

Limits that apply to BVLOS flights

Because it is such a demanding mode, the requirements to run any operation are higher. Among the limits that apply:

• You have to request the publication of a NOTAM so that other pilots are aware of an aircraft operating BVLOS. That request has to go in with enough notice for the notification to actually be issued.
• BVLOS flights over built-up areas are not permitted, nor over gatherings of people.
• The drone must maintain a reliable link with the control station, so flying beyond the safe connection range is not allowed.
• The flight may only be carried out by professional drone pilots accredited to AESA’s requirements.

Those are the three kinds of drone flight, and the line between them is where most of the regulation lives.