1. Primary Model Category

Airport capacity and delays.

2. Summary

The Airport Machine is a tool for simulating in detail all aspects of airfield operations (including runways, taxiways and apron areas). Its principal measures of performance (and outputs) are flows and throughput capacity on the airfield per unit of time and delays experienced at the various airfield facilities. It is based on a node-link structure similar to that of SIMMOD, and covers all aircraft activities from a few minutes before landing until a few minutes after take-off. This commercial software package was developed by Airport Simulation International (ASI).

The Airport Machine relies on high-level-of-detail network representations of airfields. Traffic moves along a network of links and nodes with each link being able to accommodate a single aircraft at a time. Whenever two aircraft converge on the same link, the operating strategies programmed into the model determine which of the two candidates will occupy that link first and which will incur delay.

Competing models include TAAM, SIMMOD and HERMES.

3. Input Requirements

The airport under study needs to be entered into the tool as a node-link network. Other inputs include schedule files, airport structure and ATC procedures. Aircraft types and wind information can also be model inputs. Up to eight aircraft types (user defined) and their characteristics can be specified. Control actions may either be entered manually in real time, as the simulation is being performed, or coded as a rule-base to be executed automatically.

4. Outputs

The Airport Machine is equipped with a good graphical interface which is very useful for model calibration and validation purposes. The post-processor computes flows and delays at specific locations, identifies potential bottlenecks, and produces flow/delay graphs.

Examples of information available include: numbers for arrival and departures for specified periods of time;. gate occupancy times; statistics on towing operations; number of occupied gate positions; number of aircraft in the various airport queues

5. Major Assumptions

The Airport Machine assumes a node-link structure for aircraft operations. It begins simulating operations as arriving aircraft reach the outer marker and stops immediately after take-off. It assumes that take-off operations are independent from the eventual route taken by the aircraft past the fix, so that no airborne trajectory is shown. This has been reported as a problem in some cases.

The Airport Machine can perform only single-airport studies. The flight schedule includes information about flight routes, aircraft class and parking positions. Average taxi time is "minimized" by default by The Airport Machine.

6. Computational Characteristics

The Airport Machine runs on a standard PC (MS-DOS) plus a graphics card. Two screens are necessary, one for text editing and one for graphics display. Memory requirements are 4Mb of RAM. The source code is not provided. The code was originally written in Pascal.

The support and documentation are both reportedly very good.

A typical run time for a major and very busy airport takes about 10 minutes for 24 hours of traffic.

The startup effort is about 2 to 4 weeks for people with prior exposure to simulation tools. The user interface is reportedly very good.

7. Modularity and Flexibility

The Airport Machine is a closed-architecture software. No evolution seems to be planned in the future.

8. Status of Model

Mature.

9. Extent of Model Validation

The model has been used in numerous airport studies by now and can be considered validated under a wide range of conditions. Users report good agreement of model outputs with field observations.

10. Principal Applications

Numerous applications at many airports in the United States and Europe. For instance, the model was used recently in studies of alternative strategies for increasing capacity at Boston and Frankfurt airports.

11. Model Availability

The Airport Machine is available from Airport Simulation International, Inc.. The Airport Machine is licensed to users on an airport-by-airport basis. The price is about $20K for the first license and about $10K for each additional airport. Contact Airport Simulation International, Huntington, N.Y. 11743, USA.

12. Information Base for Model Evaluation

Interview with Ingrid Gerdes (49) 531 295 2279 (ingrid.gerdes@dlr.de) and Franz Knabe (49) 531 295 2496 (fl1g@brzsp7.bs.dlr.de), both from DLR on January 9, 1996. Discussions with several model users.

13. Summary Evaluation

The Airport Machine is a commercial product to evaluate airport capacity and delays. It is intended to support detailed design-level studies, offering "fine granularity" simulation of airport surface operations. It is a mature, quite user- friendly software package that has been used extensively and whose results have been validated. Users must undergo a significant amount of training and the cost of acquiring the model is considerably higher than that of SIMMOD. On the other hand, the current user interface of The Airport Machine is superior to that of SIMMOD.