Important definitions and terms

In the field of aviation precise definitions are essential. This glossary provides important definitions and terms that are required for both the operation of UAS and the theoretical study for the examination.

These terms are not intended to replace common key-word lists or lists of abbreviations, which are available in legal documents; rather, these are selected terms that are important for all areas of UAS operation.

You will also find an example checklist and the “I’M SAFE” checklist as an attachment. It is important to remember that the former serves only as a basis; you may have to adapt it to the specific situation and the UAS.

Automatic Operation
Automatic operation is any UAS operation that follows an automated processes but still allows manual intervention. Examples are the “returnto-home” function, stabilisation systems or automatic landing systems.

Autonomous Operation
In autonomous operation, the UAS is completely independent and there is no possibility of manual intervention. This mode operation currently has no legal basis, especially in the OPEN category.

Involved People

Persons who help/assist in the operation of an unmanned aircraft are referred to as involved persons. Possible areas of responsibility are airspace observation, communication or securing the take-off and landing area.

It is important to have a detailed briefing and precise agreement of responsibilities before the flight (see “Uninvolved Persons”).

“BVLOS” stands for “Beyond Visual Line of Sight” and means that the UAS is out of the pilot’s sight. This is not allowed in the OPEN category (see “VLOS”).


In aviation, the most important flight altitudes are: the height above ground (AGL – Above Ground Level) and the altitude, which is measured above mean sea level (MSL – Mean Sea Level).

AGL indicates the height above a certain point on the ground (e.g., the starting position). In hilly terrain this can quickly become inaccurate or incorrect.

The altitude above mean sea level (MSL) is usually used by low flying manned aircraft and refers to a published reference pressure (the so-called QNH). You can obtain the QNH from the nearest airport or some weather reports (e.g., METAR).

FPV flights
“FPV” stands for “First Person View” and describes flying the UAS as if you were on board. This can be done using a camera attached to the unmanned aircraft and which sends signals to FPV goggles or even a video screen. Such an operation is classified as VLOS because the UAS is in direct line of sight of the obligating observer.

Geographical Area

The geographical area is the part of an airspace specified by the responsible aviation authority that either facilitates, restricts or excludes UAS operations. These areas are essential for the lawful operation of unmanned aircraft.

As a remote pilot, you are responsible for updating current data for the area of operation. This information is published by the responsible aviation authority.


“GNSS” stands for “Global Navigation Satellite System”. This term generally includes systems such as GPS, GLONASS or Galileo.

Mass terms
In aviation, there are various terms denoting different types of mass; the most important type of mass for UAS operation is “Maximum Take-Off Mass”. The maximum take-off mass is specified by each individual UAS manufacturer, including payload and fuel: the entire system must not exceed this mass at any time. The abbreviation “MTOM” is often used for “Maximum Take-Off Mass”.

Assemblies of people

Assemblies of people are gatherings where persons are unable to move away due to the density of the people present. This definition gives cause for caution, as you will often not be able to assess this situation with certainty from a distance; if you have the slightest doubt, assume that there will be a “gathering of people” on ski slopes, on forest paths and particularly in urban areas.

All parts of a UAS that are not used to operate or control the unmanned aircraft are called “payload”. This does NOT include the airframe, the engine or the propellers. Instruments, equipment, accessories and any other optional part as well as additional communication equipment and cameras – are part of the payload. It does not matter whether the parts are built-in or attached.

UAS / Drone
There are now numerous names and abbreviations for unmanned aircraft. In this training material and the training questions, the terms “UAS” (for “Unmanned Aircraft System”) and “unmanned aircraft” are predominantly used. Precisely defined, a UAS not only includes the unmanned aircraft itself, but also the equipment for its remote control (“system”).

Uninvolved persons
Uninvolved persons are those who are not involved in the operation of the UAS and/or do not know about the instructions and regulations of UAS operation. It is irrelevant whether or not the individuals are directly exposed to the UAS; for example, people in cars, buses, trains or aeroplanes are also considered to be “uninvolved”. Particularly sensitive rules apply to uninvolved people, which as a remote pilot you must bear in mind at all times (see “Involved people”).


“VLOS” stands for ‘Visual Line of Sight’ and denotes a direct line of sight between you as a remote pilot and the unmanned aircraft. Operation of a UAS in the OPEN category is only permitted as “VLOS operation”. An important point to note is that the line of sight must be from actual, practical visibility rather than a theoretical visibility or with the help of technical aids. In fog, for instance, the maximum practical visibility is 2 metres (see “BVLOS”).