FLOWSIM (FAA)
(Last update: 3/6/96 JKK)
1. Primary Model Category
Model of traffic flow subject to airport capacity constraints.
2. Summary
FLOWSIM is a fast-time simulation of aircraft flow between major airports to determine delays and ripple effects induced by capacity constraints. The user enters flight plans from ETMS data, and FLOWSIM uses airport capacity models to determine delays. There is no simulation of en route operations: sectors are assumed to have unlimited capacity and aircraft are simulated by flight plan, not by dynamics. Airports have fixed capacity based on weather and configuration. Tactical and strategic studies can be conducted by using the traffic management editor to implement ground delay programs, miles-in-trail restrictions, or ground stops which then adjust the flight plan for simulation.Competing models include AND, NASPAC, and TMAC.
3. Input Requirements
Requires ETMS data for aircraft flight plans. A database of capacity figures for 38 major airports is included with the model. These capacity figures are based on FAA EPS (Engineered Performance Standards) information.
4. Outputs
Delay metrics. The user can view delays as a function of airport and time.
5. Major Assumptions
All aircraft are assumed to follow pre-defined flight plans: there is no tactical rescheduling. En route sectors have unlimited capacity. Delays are produced based on miles-in-trail restrictions and airport capacity constraints.
6. Computational Characteristics
Code exists (written in C++) of approximately 10,000 - 20,000 lines and is very fast. The flight profile modeler and the timing routine are very robust and have been ported to other models. Platform, software, and hardware requirements have not yet been determined. Documentation quality is currently in draft for the prototype version.Typical run time (for a complete 24 hr simulated period) is approximately 5-6 minutes.
7. Modularity and Flexibility
Extensive work would be needed to incorporate en route operations modeling and aircraft dynamics. The object structure for the flight profile model includes all characteristics of model sectors. Actual interactions between aircraft has not been developed. The code is relatively generic because some routines have been ported to other models.
8. Status
The model is intended as an experimental tool, is a "first prototype", and is not mature. The FAA has not worked on further development for the last 2 years and has no plans at this time to do so in the future. Metron, Inc. is utilizing and modestly improving the model.
9. Extent of Model Verification
Unknown.
10. Principal Applications
Strategic delay modeling given flight plans and airport capacity constraints. Specific applications are unknown.
11. Availability
Available through FAA, Metron, Inc., and ATAC. The primary constraint is that the model requires ETMS data. Contact: Steve Bradford, FAA, (202)-358-5234, sbradford@mail.hq.faa.gov
12. Information for Model Evaluation
Interview with Steve Bradford, FAA, 12/18/95.
13. Summary Evaluation
FLOWSIM at this point is an experimental tool used to estimate flight delays as a function of aircraft flight plans and airport capacity constraints. The model has no provisions for aircraft dynamics or interactions between aircraft while flying. Flight plans must be specified in advance (using ETMS data) and can be changed while the model is running by using the traffic management editor to implement ground delay programs, miles-in-trail restrictions or ground stops which then adjust the flight plan for simulation. The model allows for the rapid simulation of flight plans to determine if ripple effects may occur among airports. The simplicity of the model (as compared to TMAC, for example) allows FLOWSIM to operate rapidly (approximately 5 minute run times). The short run time suggests that a number of different flight planning strategies can be evaluated quickly, although only in an approximate manner. The code is apparently generic because some routines have been ported to other models.
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