12. Fundamental design limitations in MIDAS limit the scalability and practicality of MIDAS as a tool to model human performance in systemwide analyses. For example, human operators cannot be created dynamically (i.e., during the simulation either conditionally based on the state of the system or at a later time than the start of the simulation) in that all operators must be initialized at the start of the simulation. Also, all operator tasks, procedures, or resource loadings (and any changes to them for alternative scenario assumptions) must be coded into the computer program rather than input as data. Further model development to relax these limitations is both technically feasible and needed.
Recommendations for Further Research and Development
The successful demonstration of a dynamic linkage between the two model systems, MIDAS and RFS, is a significant research accomplishment. MIDAS and RFS, built for different purposes and using different simulation technologies and computer systems, have been made to work together as a single system model for purposes of a practical analysis application. We have shown that explicit models of human performance can be integrated into a systemwide air traffic simulation and that their presence makes a difference to the results of the simulation.
As important a beginning as this is, it is only a beginning, akin to that first telephone call of Alexander Graham Bell down the hall to his assistant Watson. Much research and development remain to be done to achieve a system that is credible and useful in actual applications to real problems. Some recommended steps in that direction follow:
1. An essential step is to rigorously verify that the operation of the linked RFS-MIDAS system is internally logically consistent and behaves as intended and consistently with expectations and first principles. Such a verification process would include at least the following elements:
Tracking analysis to check the timing and logic of all that happens to a selection of flights as each progresses through the system, including radio communications
Sensitivity analysis to assess whether the direction and magnitude of changes in system performance in response to incremental changes in selected parameters are reasonable with respect to expectations based on first principles and model-building assumptions and intentions
Stress analysis to assess system performance when selected parameters, singly and in combination, are set to extreme values at the ends or outside of a realistic range
Each of these verification assessments typically involves logic and statistical tests as well as the judgement of independent aviation experts familiar with the dynamics and performance of the system being modeled. A convenient vehicle for conducting these tests could be the experimental design described in Chapter III. Once reasonable system performance is verified, the analytical results of the CAT sensor experiment would be meaningful and useful, and thus a practical demonstration of the utility of this approach and modeling technology. It is important to note, however, that some of the RFS and MIDAS developments recommended below would need to precede such verification tests.
2. Following verification, validation assesses the degree to which the behavior of the simulated system reflects the behavior of the real-world system it is supposed to represent. An essential element of validation is comparison of numerical values of selected system performance measures with values recorded from observed behavior of the real-world referent, where such data is available. These comparisons are often made using formal statistical tests. Again, the judgement of experts in the field also needs to be a component of the validation process.
3. With respect to the CAT sensor technology assessment itself, it would be useful to extend the experimental design to consider other factors in addition to lookahead, such as false alarm rate, detection rate, traffic loading, and pilot responses to continuous (rather than one-time) alarms, and to allow route changes as well as altitude changes for CAT avoidance. Such an effort would serve to extend the verification process for this model and test the flexibility and scalability of the modeling approach in general. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：DEVELOPMENT OF FAST-TIME SIMULATION TECHNIQUES(39)
