Implementation of Wright Laboratory F-16 MATV Simulation into D-Six
Background
The F-16 MATV flight simulation model, currently in use in Wright Laboratory’s unique LAMARS motion-base simulator facility, is a highly-validated implementation of the Lockheed-Martin model developed in Fort Worth. Like the model used by Lockheed-Martin, the Wright Laboratory
model has the ability to simulate flight of a basic Block 40 F-16, but can also be instantly reconfigured to emulate the F-16 MATV. In MATV mode the model has a toggle between the initial control laws implemented during the initial phases of the program, and the final control laws
developed as a result of flight testing and flying qualities refinement. In addition, in MATV mode the standard F-16 alpha limiter can be activated as well as a variety of "dial-a-gain" parameters which can be set to tailor dynamic response about all axes. All of these features are
identical to those implemented on the actual flight vehicle. It was discovered, however, during high-angle-of-attack flight testing of the F-16 MATV that the aerodynamic modeling of the simulation was inadequate. Since Bihrle Applied Research (Bihrle) has extensive experience testing
and modeling the F-16 (with and without MATV) at high angles of attack, the Flight Dynamics and Controls Branch at Wright Laboratory requested that a rehost of the complete F-16 MATV model be made into the D-Six simulation environment with an upgraded high-angle-of-attack aerodynamic
model.
In order to accomplish this task, all of the FORTRAN code modeling the flight control system and all of the aerodynamic data files were needed. The flight control system is comprised of nearly 100 files and thousands of lines of FORtrAN code written both by Lockheed-Martin and Wright
Laboratory. The aerodynamic model is made up of over 1100 data files including static, dynamic and hinge moment data for dozens of different aircraft configurations. The task of rehosting and upgrading this model into D-Six was divided into three main subtasks:
1. Aerodynamic data file conversion and mechanization
2. Flight control system incorporation into D-Six and check-out
3. High-angle-of-attack aerodynamic model upgrade
Aerodynamic Data Conversion and Mechanization
The entire aerodynamic database for the Wright Laboratory F-16 MATV simulation is contained in one file in their Genesis data format. It was necessary to break this file into approximately 1100 two-dimensional data files. Fortunately, Aeroport , a data conversion tool developed for
D-Six, allowed the data files to be broken, arranging independent variable breakpoints where desired, in just a few hours. During this process, a log file is generated which allows D-Six to directly read in and mechanize the data structure. All that is left to the engineer was to
implement coefficient multipliers, store loading flags, etc. Using D-SIX, the entire database for the F-16 MATV was converted, implemented and mechanized in less than one man-week.
Flight Control System Implementation
Since the F-16 MATV FCS is essentially a self-contained computer program, the only significant task involved is determination of the inputs required from D-Six and the outputs generated by the FCS code. Initially, two subroutines are identified ad the gateways in and out of the FCS.
Once these subroutines are identified, a simple companion program to D-Six, CodePort, identifies the variables which are not assigned a value in the input gateway subroutine. These variables are then cross-referenced to the appropriate D-Six variables using a graphical interface. In
similar fashion, the control deflection variables required by the D-Six aerodynamic model are matched cross-referenced to the appropriate variables in the output gateway subroutine. If the user is very familiar with the FCS code, this task can be accomplished in one or two days.
Inevitably, however, a learning process is required to become familiar with the code. Fortunately, the FORTRAN code provided to Bihrle by Wright Laboratory was very well organized and documented. This minimized the startup time which is invariably required to become familiar with the
structure and content of the flight control system (FCS) or any legacy code. In the case of the F-16 MATV FCS model, the process described above, including validation of the model in all flight modes, was accomplished in approximately three man-weeks.
High-Angle-of-Attack Aerodynamic Model Upgrade
This process required conversion of the entire database from stability axis to body axis. In addition, to maintain continuity of the data structure, approximately 70% of the Wright Laboratory database was incremented to provide the mach and altitude database increments. The Bihrle
high-angle of attack database was then used as the basis for all low-speed data as well as for the increments generated from the Wright Laboratory database. Great care was taken to ensure that the low speed data from both the Wright Laboratory database and the Bihrle database matched
identically. Although examining hundreds of files individually can be painstaking, data analysis tools developed by Bihrle expedite this process considerably. The high-angle-of-attack database upgrade is nearly complete and has taken approximately five man weeks to date.
Summary
In summary, starting with only the D-Six simulation environment, the most complete simulation model of the F-16 MATV, and one of the more complicated fighter simulation models currently in use, was implemented in its entirety, with validation in all flight modes, in under five man
weeks. This simulation runs in real time on a current technology personal computer at the identical frame rate (50 Hz) used by the primary users. In just over 10 man weeks from the beginning of the project, the aerodynamic database will be completely upgraded to make the D-Six F-16 MATV
simulation the most accurate available.
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