AI Traffic: Difference between revisions

A new traffic file format was introduced with FlightGear 1.9.0, referred to as "Traffic Manager II" format (TM-II), in which aircraft and flights are no longer directly coupled, leading to more flexibility.  

Commercial aviation, in FlightGear and in real life is centered around aircrafts with commercial airliners being used to operate a series of scheduled flights, on a daily or weekly basis. For example, the [[McDonnell Douglas MD11]] operated by KLM flies regularly between Amsterdam and various distant destinations, such as San Francisco or Minneapolis in the United States, Vancouver or Montreal in Canada, Accra and Lagos in Africa, or New Delhi in India. Some of these routes are too long for a return flight to be achieved within a 24h00 day when you account for the turn around time at each airport. As a result, in real-life, this aircraft will be operating a series of flights on multiple routes; given some routes in the series are shorter than the trip to San Francisco, the time lost on one route can be gained on another, averaging the aircraft use to one round-trip a day.

In FlightGear, we wouldn't have to be so strictly considerate about the turnaround times as a real-world airline would, but in the not-so distant future, we also want to be able to see realisticly crowded terminals at our simulated airports, so considering the turnaround time in the schedules is a good thing. Therefore, most of the long-haul aircraft will need to be scheduled to fly more than one route. Hence, each AI aircraft has one or more routes assigned to it, which repeat on a weekly, daily, or hourly basis.  

The FlightGear traffic manager system, periodically checks the approximate position of a each aircraft in its database. This database was originally constructed on the basis of a fixed routing table that was assigned to each aircraft. As in the real-world, when a route ends at one airport the next one has to start from the same airport as well. An important difference between the real world and these FlightGear traffic patterns is that while in the real world aircraft schedules are frequently rotated, the FlightGear routes remain the same unless a major update to the database takes place. Real aircraft require maintenance, and are therefore taken out of service periodically. FlightGear aircraft have the advantage that they do not require maintenance in this respect.

There were still some significant drawbacks to this approach, nevertheless. Consider the MD11 a little further. In real life, KLM operates this aircraft on many routes that are serviced at relatively irregular intervals. For example, many flights to the Carribean are served only two or three times a week, making it extremely complicated to build completely accurate traffic files for these routes.