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Aircraft Movement Module

The main objectives of the aircraft movement module are to identify the location of emissions release from aircraft in flight and to predict airborne delay characteristics.


Deviation from 4D optimal trajectories result from ATC structures such as flying along standard jetways, avoiding terrain/restricted airspace and flying via standard fixes into and out of the terminal area. Assessment of the impact of these factors requires consideration of current and future routing structures for different regions of the world. This can be achieved through examination of ATC charts, as well as actual flight and performance data for representative regions of the world, coupled to parametric modelling for other areas.

Deviations for conflict avoidance with other aircraft are largely an unavoidable consequence of needing to keep aircraft separated, and the amount of deviation involved increases with traffic density in a given piece of airspace. Similar deviations are also required to keep aircraft separated from adverse weather conditions. Flight data will be used to parameterise these effects.

En route restrictions such as miles or minutes-in-trail are required to account for airspace capacity limitations, while terminal area holding patterns are required to account for airport capacity limitations. In the Aircraft Movement Module, needs for these restrictions are identified in a Delay Calculator by comparing the capacity of a given airspace (from the Airspace Capacity Model) to the demand imposed upon it at a given time. Holding patterns in the terminal area are identified from the Airport Activity Module which performs a similar comparison between capacity and demand on the ground. Airspace restrictions which require termination of further departures from a given airport (i.e. ground stop requirements), as well as total airborne delay per segment are fed back to the Airport Activity Module for its use. Consideration of future airspace sector capacity and demand evolutions in different regions is also required. Future evolutions of the ATC system and its users will therefore need to be predicted, for example in terms of ATC infrastructure, technologies and traffic redistribution.

From this set of processes, modifications to the optimal 4D trajectories are made in the Airborne Operations Model in terms of an “inefficiency factor” which are applied in the various axes to generate the actual predicted route, distance and time involved in a given flight segment. We are currently estimating these factors using US ETMS radar track data. The complete set of trajectories across all segments is then converted to emissions production (using information from the Aircraft Technology & Cost Module) and distance flown by grid cell and altitude layer for the region of interest (or globally), which is then output to the Global Climate Module.
Sample policy levers that can be specifically tested by this module revolve around those that affect how aircraft are flown en route and in the terminal areas, including policies that:

  • Change airspace infrastructure including airspace design (e.g. dynamic re-sectorisation and polar routings) and technologies (e.g. surveillance systems)
  • Change procedures, such as enhanced coordination between en route sectors, arrival metering to allow quiet approach procedures, “Free flight”, reduced separation minima, etc.
  • Change aircraft being operated, including size, capabilities (e.g. RNAV, RNP), configuration, etc.