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OPAS uses five defined arrival segments to analyse aircraft arrival paths, with potential for additional segments based on specific airport layouts.

1. Overview of arrival segments

The diagram below outlines the segments of a typical arrival path.

2. Defining the runway threshold to wheels down segment

This segment captures the flight whilst the arrival is still airborne, from when the flight track enters at the runway edge until shortly after most wheels down events occur.

To build this zone accurately:

1. Use a wide dataset of flight tracks to analyse wheels down patterns.
2. Alternatively, use satellite or aerial imagery to view the distribution of skid marks.
3. Ensure the zone covers the general wheels down area.

Note: There is no guarantee that an aircraft will have wheels down within this zone, as it may continue further down the runway. However, careful analysis ensures a high degree of accuracy.

The image above shows an example of these zones in 3D mode.

3. Defining the wheels down to runway exit segment

This zone covers on-runway time after the wheels down zone event. The height of the zones is lower than the previous zone to exclude aircraft still airborne.

Events in this segment include reverse thrust shortly after entering the zone. Exit time is when the aircraft taxis off the active runway area.

Important: Build these zones so they adjoin the previous zone.

4. Defining runway exit segments

These operational segments are zones covering all potential runway exit points.

To build runway exit segments:

1. Use a detailed map layer of the airport or aerial photography.
2. Define exit points by controller stop points where aircraft may be held to allow other taxiing aircraft to clear.

These segments provide clear data about congestion points and efficiency issues.

5. Understanding taxi and stationary segments

Taxi and stationary segments are not defined by physical selection zones. They are derived via an algorithm that uses exiting Runway Exit segments and entering On Stand segments to bookend the time spent in taxi mode.

The taxi phase can be any route through the airport directed by the tower and is not bound by physical limits, reducing the complexity of detecting this operational segment.

Stationary segments

The OPAS system creates a stationary operational segment whenever an aircraft radar track shows as stationary for more than a few seconds (a configurable time). When the track presents as moving again, the stationary segment is closed and Taxi is resumed.

The taxi phase is the sum total of both taxi and stationary times. It is the complete time taken for the aircraft to go from runway exit to on stand. This means that inside this segment, it could contain one or more stationary segments, allowing you to analyse how many times an aircraft was made to stop whilst taxiing to the stand.

It is equally as likely that the taxi phase would not contain any stationary segments, depending on the level of congestion and efficiency at the airport in question.

Note: Stationary segments are created whenever an aircraft is registering as stationary for a set, configurable amount of time. This means a stationary segment can occur inside any segment where the aircraft must wait. Logically, this means a stationary segment will always be shorter than the total time spent in that segment.

6. Defining on stand segments

The on stand operational segment defines (for arrivals) the end of the ground operation and is the final segment. It also informs the previous segment (taxi) that it is over.

On stand segments will end one minute after they begin. This time is configurable.

Because it is impractical to create such a large amount of selection zones for on stand areas, as large airports have so many on stand terminal areas, the creation and detection for on stand areas is done using a different method.

On stand segments require:

• A detailed and accurate airport polygon map of all areas that can be uploaded as a GIS object
• Stand allocation data provided as part of plan feed or other method

EVS engineers perform database configuration work using this data to ensure accurate on stand segment creation.