Conflict Detection

The primary purpose of Air Traffic Control (ATC) is to prevent aircraft collisions by maintaining safe separation between all airborne aircraft.

Aircraft are separated horizontally or vertically.
A conflict occurs when both horizontal and vertical distances between a pair of aircraft breach separation thresholds.

Conflict detection is an \(O(n^2)\) problem because every aircraft pair must be checked:

The MTCD solution to the \(O(n^2)\) problem is to limit the size of \(n\).

Our solution is to reduce processing per aircraft pair to increase capacity.

The primary goal of our conflict detector is to detect all potential conflicts. Its secondary goal is to handle as many aircraft as possible.

The graph shows the processing times required by our prototype conflict detector to detect all potential conflicts between airborne flights on Eurocontrol Network Managers’ busiest day: 28th June 2019.

Trajectory data was extracted from the Eurocontrol R&D data archive.

The maximum number of:

• airborne flights were 3749,
• conflict paths discovered per flight were 1981,
• conflicts detected per flight were 113.

And the maximum processing time for a flight was 0.425 seconds.

The conflict detector calculates horizontal separation on the WGS-84 ellipsoid. It was built with rustc 1.92.0 and run on a 16-core AMD Ryzen processor with 32GB of RAM.

Conventional conflict detectors calculate horizontal distances between aircraft’s simultaneous predicted positions to determine separation.

This inefficient, computationally intensive process limits capacity.
It also encourages calculating vertical separation before horizontal, which makes conflict detection sensitive to the vertical accuracy of predicted trajectories.

For example, even if the trajectories of both aircraft involved in AIRPROX REPORT No. 2023054 had been sent to both sectors, their MTCDs would not have detected the conflict because their predicted trajectories were vertically separated.

Our algorithm prioritises horizontal separation.

It creates horizontal paths from predicted aircraft trajectories and determines whether pairs of paths can lose separation.
If so, it calculates their conflict paths, i.e., where they can lose horizontal separation.

An aircraft pair is safely separated:

• if they don’t have conflict paths,
• or outside of their conflict paths.

Separation needs to be calculated only in trajectory sections that correspond to conflict paths, and only if the aircraft can occupy them simultaneously. Separation is assured once an aircraft has flown past its conflict path.

The capacity and safety of MTCDs could be improved if horizontal separation were calculated only within conflict paths and prioritised over vertical separation.