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BasicsFlight Rules

Flight Rules

The primary way of differentiating aircraft and relevant procedures is by flight rule. In general there are 2 types of flight rules, Instrumental Fight Rules (IFR) which are most widely used in commercial aviation and Visual Flight Rules (VFR) which are mostly used by general aviation and alike. There are some sub-types of VFR, such as SVFR, however this page will go over the primary differences between IFR and VFR flights and/or aircraft.

Things that are common for all airborne vehicles

While this might be different for other regions of the world, in Europe the vast majority of airspace requires some kind of radio communications for all traffic passing through it. Said radio communications may be either 1-way or 2-way depending on airspace class and aerodrome staffing.

In the vicinity of smaller airfields and in uncontrolled airspace a Common Traffic Advisory Frequency (CTAF) will most likely be used for aircraft to communicate between each other.

In controlled airspace a frequency for 2-way communications is available. Such a frequency is staffed by an Air Traffic Control Officer (ATCO) on the ground who is responsible for a certain portion of the airspace that is covered by that frequency.

Instrumental Flight Rules (IFR)

The key features of traffic following IFR are as follows:

  • A valid flight plan is required
  • 2-way radio communications are required at all times
  • IFR traffic uses navigational databases and coordinate-defined/radially defined navigational points to navigate through airspace
  • IFR departures need to follow a Standard Instrument Departure (SID) or be coordinated individually among ATCOs
  • IFR arrivals need to follow a Standard Terminal Arrival (STAR), be vectored, or be coordinated individually among ATCOs
  • There are no particular visibility (horizontal or vertical) requirements to execute an IFR flight as long as the weather conditions are deemed sufficient and safe by the crew
  • ATC is responsible for IFR separation in almost all instances (see Airspace Classes for more information).

Visual Flight Rules (VFR)

  • In most regions of the world having a flight plan is not mandatory
  • 2-way radio communications required in class A, B, C, and D airspaces, but not E, F, and G
  • As the name suggests, pilots following VFR use Visual Reference Points (VRPs) and other distinct visual terrain features for navigation instead of a navigational database
  • VFR traffic is not bound to any particular route as long as it does not disturb other traffic and does not violate the boundaries of restricted and/or reserved airspaces
  • Since VRPs are used for navigation, certain visibility requirements are in force for VFR traffic. The most common requirement in Europe is cloud ceiling of 1500ft or greater and horizontal visibility of 5000m when departing and flying below FL100/10000ft (depending on the transition altitude/level). VFR traffic must also maintain visual contact with the ground at all times
  • In most instances the crew is responsible for maintaining visual separation to other traffic (see Airspace Classes for more information).

Special Visual Flight Rules (SVFR)

  • Used when visibility is insufficient for regular VFR
  • Traffic must remain in controlled airspace at all times and maintain two-way communications
  • In most cases the aircraft and the pilot must be IFR-rated for night flights
  • Helicopters and especially emergency services often use SVFR to gain priority and avoid being sent outside of controlled airspace
TAFAirspace Classes