This project dealt with the development of a mathematical foundation and practical algorithms to compute the safety fans to be used in conjunction with aerodynamic deceleration payload delivery systems tests. It started from the development of mathematical models to compute a descent / gliding trajectory for a generic multiple-stage system in the nominal (controlled) configuration and with a series of different failures (of canopy and controls).
Within this project the concept of ballistic winds was introduced and mathematically verified in multiple simulations. These ballistic winds simplify calculation of the safety fans, so that the computer is no longer needed. They can be calculated based on the best known winds aloft (measured or predicted).
Finally, the graphical user interface (GUI) was developed as a standalone Windows-friendly application and then fully tested using the YPG winds and aerial delivery system database. This GUI provides test planning officers with a unique variety of trade-off options, as well as allows effective representation of all safety-related information both to the ground personal and to the crew performing a payload delivery from a transport aircraft or helicopter. Figure A presents a screen shot of the developed GUI which performs various computations and manipulations (the factual data is replaced with fake data). This GUI was developed in the MATLAB development environment using the Open GUI Layout Editor GUIDE. The code that runs this GUI contains over 3000 lines and the GUI itself is subdivided into several panels.
Figure A. Safety fans GUI.
The Winds panel allows the user to browse for wind files and chose the most appropriate one. The wind source files are sounding, Windpack, balloon and JAAWIN winds. The GUI automatically recognizes what type of file was chosen and how to read it properly. The wind data is then loaded into the appropriate winds matrix. Auxiliary data such as the name and type of the file, when and where the winds data were taken, and altitude range is also read and displayed in the corresponding windows.
The Drop Zone panel allows the user to choose one of the drop zones stored in an ASCII file. The script behind this panel loads latitude, longitude and mean-sea-level altitude of a chosen drop zone. The corresponding map appears on the left. By default the center of the chosen DZ becomes an intended impact point (shown in the corresponding windows). It can be changed by selecting a new point on the map or typing new values in the windows. (The map can be any graphical image scaled into a rectangle with respect to the Universal Transverse Mercator (UTM) coordinates.) The user can zoom the map in and out, move it, measure distances between selected points, get the coordinates of any point selected with the cursor, and read the coordinates of any point in one of the chosen formats (UTM on the map, or Lat/Lon in the windows).
The Test System panel allows the user to choose one of the ADSs stored in an Excel file. This system can have one, two, or three stages. The corresponding windows for unused stages are shadowed. The only ADS data needed for fan computation are the system’s descent rate, glide ratio and altitude to deploy (altitude loss for the first stage). The user is allowed to change any of these three parameters in the corresponding windows or create an entirely new system. This data along with winds aloft and release point information is used to compute safety fans.
The idea behind the Release Point panel is that based on the system being tested and available winds data, the user enters various release points and computes safety fans. If the safety requirements are not met, the user moves the release point and a new safety fan can be generated. The release point can be moved by clicking on a new location in the map, in which case the new coordinates immediately appear in the corresponding panel windows, or by entering a new latitude and longitude in the panel windows. Altitude, airspeed, and direction at the release point are provided by the user. When a satisfactory release point has been chosen, its coordinates will be provided to the crew for execution.
Since the ground crew and the deployment crew can speak different technical languages (units), the Units panel allows the user to change units from the International System of Units (SI) to English and back. In addition, Lat/Lon coordinates can be visualized throughout all panels in one of the following three formats:
- Deg – degrees.decimal degrees
- DM – degrees, minutes.decimal minutes
- DMS – degrees, minutes, seconds.decimal seconds
If using the DM or Deg formats, the unused windows are shadowed. For example, the chosen format in Fig.A is DM, and therefore the first windows in all Lat/Lon readings are shadowed.
Other operational functions in the GUI include timing, fan computation, loading and saving data, and commenting. The “Start Clock” button asks the user for the computer’s time zone setting and starts a continuously updating clock in Coordinated Universal Time (UTC). When all the necessary data for fan computation has been selected and entered, the user can compute the current safety fan. Corresponding graphics appear on the map. The time of the most recent calculation appears under the running clock. The GUI can be saved with the Save Data button. Once a GUI has been saved, it can be loaded with the Load Data button. When reloaded, the GUI is still interactive. This means that though it can be used as a simple figure capturing one state in time, it can also be used as the starting point for continuing operations. If using a loaded GUI, the clock must be restarted but all other data are available. The user can enter comments on a particular configuration in the Comments panel. These comments will be saved with the GUI. The Stop GUI button stops all activity in the figure and is used just prior to closing the application.