Italian AV-8B II+ Mission Simulator Aerodynamics Model Development: D-Six to Trainer in Less than 15 Minutes!!!
Background
The development of a new and improved aerodynamic simulation model to form the basis of the latest AV-8BII+ mission simulator was a primary goal in the deployment of the new device S2F176 for the Italian Navy. The current AV-8 simulation, the device 2F150, had been cited for a number
of deficiencies in its modeling of the II+ configuration, and these were to be resolved in this latest mission trainer. The need to update this model required a number of analytical tasks that dictated a highly flexible simulation environment. As a result, Bihrle Applied Research Inc.
was tasked to assist in the development of the new aerodynamic model, and Bihrle’s simulation development and analysis environment, D-Six, played a key role in the model evolution and validation. Some of the tasks required during the engineering analysis of the existing models and
the formulation of the revised model are summarized below:
Detailed evaluation of the existing models – Because of the varied aerodynamic database background of this model, and the number of both trainer and engineering simulations, the development of a new database required
the assessment of the complex databases from each of the models, as well as any other available AV-8 data.
Implementation of the existing trainer and its associated flight control, weight and balance, stores and engine models. Because the aerodynamic database update was to use the current trainer model components, their operation
needed to be validated on the current 2F150 trainer device code, before the new aerodynamic database could be evaluated.
Development and validation of a new AV-8BII+ mission simulation database. The new model, along with any code revisions, were to be delivered to an full mission trainer for hosting in their unique simulation hardware
environment.
D-Six proved to be the ideal simulation environment for the successful completion of these complex tasks. Because of the variety of it’s imbedded tools, and its ability to import and export a wide range of formats, it proved particularly adept at coexisting with the
customer’s need to move the models into their full mission simulation hardware. The following discussion highlights some of the specific operations and how D-Six enabled them.
AV-8BII+ Aerodynamics Model Evaluation
The creation of a baseline aerodynamics model for the development of the IMS trainer required the evaluation of three existing AV-8B aerodynamics models. The models were acquired from the US NAVY and implemented in D-Six as individual projects. The implementation of the two engineering
models took advantage of the Aeroport utility, where the existing trainer model required a custom database converter.
Once implemented into D-Six the models were "exercised" then compared against each other and evaluated. "Exercising" the models involved using the D-Six Overdrive tool to sweep the models at user specified configurations and at fixed state breakpoints (i.e., a = 0 to 90 , D 5 ) and
then exporting the resulting output as a database file that could be compared with similar output from other disparate models. This exercise of the three aerodynamics models allowed the comparison of identical configurations, which was impossible by merely comparing the individual model
table data because of the simulations structural differences. The overdrive work included driving the inputs of the model with several different variable sweeps, allowing, for example, the definition of each aerodynamics model’s prediction of pitching moment variation with angle of
attack. Once the major functional dependencies were exercised and saved to files, the resulting output from the models were compared against one another using the D-Six Plotting tools.
From this evaluation of the models, decisions were made as to how to combine parts of each model to create a new model baseline for the devise S2F176 trainer.
Trainer Flight Model Implementation
During the database development task , two simulation models were maintained to support the required activities. The first model was a D-Six natively hosted database that allowed the developers full access to all D-Six’s analytic and interface options. The flight control, weight
and balance, and engine models from the S2F176 trainer were also implemented into the D-Six simulation environment. A second model implementation was then hosted that used the same simulation model code that is used in the full mission trainer (including all table calls, integration
routines, and all simulation functions). The full mechanization of this model code enabled Bihrle to verify any model changes or updates in the identical model structure and code as used by the trainer, while still in the D-Six simulation environment. This mechanization was performed by
implementing a program variable mapping function to pass information between D-Six and the trainer code functions.
The D-Six implementation verified against trainer check-case data using the D-Six Overdrive utility.
Aerodynamics Model and Database Modification and Validation
Since the new aerodynamics baseline was implemented into the D-Six InfoFile, database modifications were able to be made real time during the model validation using this tool’s graphical interface. As model development progressed, aerodynamics model changes were made using the
D-Six Database Editing tools as well as D-Six’s ability to easily import new data files interactively during the simulation session. New data were implemented into the model by graphically manipulating specific areas of the database or by incorporating new data base files that were
created using external tools.
Aerodynamics Model Validation
Model validation was carried out using both D-Six Overdrive as well as real-time simulation runs. Comparisons with criteria data required driving the complete six-degree-of freedom flight model with other simulation inputs, flight data, user-defined control stick deflections, and
user-defined control surface deflections. Real-time desk-top simulation sessions using a game joystick for pilot inputs were also used to replicate maneuvers when no digital data were available.
Aerodynamics Model Export
Since the aerodynamics model for the S2F176 Trainer was implemented in D-Six using the same structure and interface as used in the trainer, the aerodynamics model logic code was instantly portable to the trainer. For this transfer, the database was exported from the InfoFile structures
using Aeroport. Once converted, the new database, now in the real time trainer format, could be re-implemented into the D-Six mechanization of the real time trainer code. This process permitted the in-house validation of the successful deployment of the new model data and code into the
real time trainer format. This step insured the rapid integration of the new model onto the full up mission trainer.
Model Verification
To ensure that the database conversion was performed correctly a model verification was performed. The aerodynamics database under the real time trainer format was exercised using D-Six and compared to data collected from exercising the same aerodynamics database in the native D-Six
database format. This was as easy a performing a simulation run, saving the data, switching the flag to access the alternate database format, then driving the simulation with previously saved data.
Implementation into the Trainer
Once development iterations were complete, model updates were delivered to the customer via email. Because of all the previous model update code and data validation described above, the mechanization of the model updates merely required the customer to link and compile the model
changes into their mission simulation environment. As a result, the customer was able to implement the changes into the trainer simulation environment and be up and flying in less than 15 minutes! With this capability, Bihrle was also able to easily support on site database updates
requests and quickly export to the full mission trainer for pilot evaluation.
Summary
The success of the Italian Navy AV-8BII+ trainer development has shown that the D-Six Simulation Environment is fully capable of supporting other real-time environments that may be "tied" hardware configurations etc. The ability to use the same code during model development and piloted
evaluation proved to be key in the efficient development and propagation of the new simulation database.
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