Procedural Control - Procedural Approaches

Procedural Approaches

Every runway used by IFR aircraft normally has a procedural approach defined and published. This generally involves the aircraft flying over a fix (navaid or 'beacon') on or close to the airport (where the aircraft can hold if necessary), flying away from the airport on a set track while descending (going 'beacon outbound'), then at some point (perhaps ten miles) from the airport turning back towards the airport aligned with the runway to make an approach (becoming 'inbound track established' or just 'established').

In procedural approach control, separation is maintained by allowing only one aircraft to be making an approach at any one time; the proceeding aircraft must either be in visual contact by the airport's control tower, or have reported that it has landed before the next aircraft is allowed to leave the hold and commence the approach.

At airports equipped with radar, procedural approaches normally are used only in the event of an aircraft suffering a radio failure, or for training purposes. At non-radar airports or when radar is not available, these are the only means of IFR flights making approaches to the airport.

At some non-radar airports, the procedural approach may be combined with aerodrome control, thus providing a control service for all aircraft at the airport, and all inbound and outbound flights within its terminal airspace. Because most aircraft fly to/or from the same place (i.e. an airport runway) within this airspace, procedural controllers use a variety of separation standards to achieve a safe and expeditious flow of air traffic to and/or from the airport.

One commonly used separation in these locations is track separation, which states that two aircraft on different tracks to/from a navigational aid must be separated from each other provided at least one is a minimum distance from the navaid. The distance required varies dependent upon how far apart the tracks are. For example, two aircraft on tracks that are 60° apart do not have to be far from the navaid to be clear of each other in comparison to two aircraft whose tracks are 13° apart.