User Guide

AVID OAV Version 2.0 User Guide Table of Contents Chapter 1 Introduction What is AVID OAV? AVID OAV Features Chapter 2 Using AVID OAV System Requirements Starting AVID OAV The First Time File Types The Project Organizer Mission Analysis Aircraft Optimization Closing the Program Conclusion Chapter 3 Program Customization Editing Initial Data Files Setting Personal Preferences Display Window Options Geometry Rendering Options Display Window Controls Chapter 4 The Geometric Component Editor Introduction Adding a New Component Modifying Components Uninstalling Components Deleting Components Copying Components Chapter 5 Setting the OAV Properties Aerodynamics Geometry Payload Power Circuits Performance Propulsion and Power Engine Accessories 1-1 Battery Propulsion Battery Generator Power Accessories Weight and Balance Edit Inertia Display Total Inertia The Aircraft Editor Chapter 6 Optimizing the OAV Background on the Particle Optimization Method (PSO) Swarm Based Optimization Dialog Box Running Swarm Chapter 7 Mission Analysis Mission Phases Climb (max rate) Phase Climb (max vertical rate) Phase Climb (true airspeed) Phase Climb (vertical) Phase Cruise Phase Cruise (max L/D) Phase Dash (distance) Phase Dash (time) Phase Hover Phase Loiter Phase OpenClimb Phase Perch Phase Mission Dialog Box Mission Results Chapter 8 Trade Studies Trade Studies Dialog Box Single Variable Trade Study Multi-Variable Trade Study Saving and Loading Trade Studies Chapter 9 Help About this User Guide Technical Support 1-2 Chapter 1 Introduction What is AVID OAV? AVID OAV is an acronym for Air Vehicle Integrated Design Organic Air Vehicle. AVID OAV Version 4.0 is an application suitable for conceptual aircraft design, analysis and optimization. It has been designed and built with an emphasis on user-friendliness and maintainability. Traditional aerospace analysis codes and methods are focused on conventional aircraft analysis and design. They rely on empirical data collected during the first century of flight. As we enter the 21st Century, however, military and civilian aircraft need to be designed to meet a whole new set of requirements. Statistics-based methods will not work outside their historical constraints. AVID OAV methodology is geometry and physics-based allowing the design, analysis and optimization of aircraft that fall outside the traditional envelope. This inception of AVID OAV is focused on designing the vertical takeoff and landing (VTOL) ducted fan concept. However, the clever user will find that the code can also be used for more conventional concepts. AVID OAV satisfies the need for an analysis tool that can predict the performance of a small unmanned air vehicle. A conceptual design created with this software includes not only a geometric model of the aircraft but also detailed information on the different subsystems installed on the aircraft. Once properly configured, the design can be analyzed or optimized. The multi-phase mission module calculates the aerodynamics and performance based on the user-specified mission requirements. The optimization module will search for the OAV specifications that improve the ability to fly a specific mission under a given objective. There are four top menu items: File, OAV, View, and Help. This user guide will review the options available under each menu and provide a detailed description of all possible inputs and outputs. 1-3 AVID OAV Features AVID OAV has five types of user data files that can be loaded or saved through the File menu. The OAV (*.oav) data file includes all the information, including geometry, defining an OAV. The Mission (*.mis) data file includes the definition of all the phases comprising a given mission. The Trade Study (*.ts) data file includes the parameters that define a trade study and an optimization. The Project file (*.prj) contains references to the other three file types. Several OAV, Mission, and Trade Study files can be associated together into a project. Component database files (*.oavxls) provide a library of nonairframe components that can be installed in a vehicle. The File menu contains these items: New, Load Project, Save Project, Project, Save Cross-Section Geometry As, Save IGS File As, Edit Initial Data, Launch Vorview, User Options, and Print. New informs the application that you wish to begin working with a new OAV and will prompt you if any of your current data is not saved. Load Project loads a project file (*.prj). Any files that the project owns will also be loaded. Save Project saves your current project as well as any open files the project owns. Project is a sub menu and provides a way to load and save files separately from their association with a project file. The Project sub menu contains eight items: Open OAV, Save OAV, Save OAV As, Save Mission, Load Mission, Save Trade Study, Load Trade Study, and Project Organizer. The first seven menu items provide for loading and saving individual files. The last menu item, Project Organizer, opens the Project Organizer dialog, which allows you to manage what files are in the current project. Save Cross-Section Geometry As generates a file that describes the geometric cross sections of the loaded OAV. Other programs can use this cross section information for analysis. The Vorview application uses this type of cross section information. Save IGS File As also generates a file containing geometric cross section information, but the file type is IGS format. This is useful when porting data from AVID OAV to other computer-aided design programs. Edit Initial Data opens the initial data file editor. When the program starts, the default initial data file, initialdata.oavxls, is loaded. The data file contains the definitions of various components that may be installed on an OAV. You may also load custom-created data files. The initial data file editor allows the manipulation of the information contained in these files. Launch Vorview launches the Vorview application. User Options invokes the User Options dialog. Here you can specify additional data files, whether or not to display the coordinate axes in the Display window, and the colors you would like to show in AVID OAV’s many tables. The final File menu item, Print, is a feature intended for a future release of AVID OAV. The OAV menu provides access to all of the features of AVID OAV that manipulate and study an OAV. There are five items: Design Mission, Edit Aircraft Parameters, Optimize, Properties, and Geometric Modeler. Design Mission accesses the Mission dialog, which is also displayed when a mission file is loaded. The Mission dialog facilitates the definition of a mission that the current OAV will fly. Edit Aircraft Parameters opens the aircraft editor, which allows you to manipulate all of the types of OAV parameters in one dialog. Optimize is a sub menu that allows the optimization of the aircraft using the Swarm Optimization method and the creation of Trade Studies. Its 1-4 menu items are Swarm Optimization, which opens the Swarm Based Optimization dialog, and Trade Study, which opens the Trade Studies dialog. Properties is also a sub menu and facilitates the setup and definition of the OAV’s non-airframe components. Its Menu items are Aerodynamics, Engine Modeling, Geometry, Payload, Performance, Propulsion and Power, Stability, and Weight and Balance. Aerodynamics reports values for lift, drag, and moment for a range of angles of attack. Engine Modeling brings up a dialog for modeling the performance of fossil fuel based engines. Geometry invokes a dialog that allows you to specify parameters that apply to all geometric components. Payload allows you to configure the electrical systems of the OAV. Performance allows the user to specify values for variables that define or affect the performance of the OAV. Propulsion and Power allows the user to configure the propulsion system of the OAV. Stability currently informs you that static stability information is displayed in the results of running a mission. Weight and Balance allows the user to specify the inertial properties for the whole aircraft or by component. The Geometric Modeler submenu provides access to the Edit Geometric Modeler Components dialog through which you can install new geometric components to the vehicle. Within this dialog, you may also uninstall, modify, copy and delete existing geometric components. The View menu allows you to manipulate the Display window. The menu contains eight items: Shaded, Transparent, Wireframe, Side by Side, Single, Multiple, Display Controls, and Refresh. The first three menu items control how the OAV is drawn. Shaded means that the aircraft is drawn with color-shaded surfaces. Transparent means that the aircraft is drawn with transparent surfaces. Wireframe means that the OAV is drawn with lines: a “wire” frame. The next three menu items control how many views of the OAV are shown in the Display window. Side by Side divides the display into two halves, each with a depiction of the OAV at a different angle of view. Single shows one view of the OAV. Multiple divides the screen into four quadrants, each with a depiction of the OAV at a different angle of view. Display Controls opens a dialog that allows you to rotate and move the OAV in the Display window. The display controls also allow you to zoom in and out. Refresh forces the Display window to be redrawn. The Help menu contains an on-line version of this user guide in Contents. Software version number and technical support contact information can also be found in the Help submenu About. On MacOS this information is located in the avid program menu by selecting About avid. 1-5 Chapter 2 Using AVID OAV System Requirements AVID OAV version 4.0 can be executed on Linux, Mac OS 10.2.8, and Windows 2000/XP. Testing under Linux has been done using RedHat 7.2 with the Mesa OpenGL libraries. Other Linux distributions, or newer versions of Linux RedHat may work but we cannot guarantee it. Qt libraries needed to run the program are included along with the corresponding executable file. AVID OAV v4.0 uses version 3.3.1 Qt libraries on Linux, Windows, and Mac OS. Starting AVID OAV Running AVID OAV on any of the platforms requires the execution of different scripts or batch files. It is possible to execute the program directly but you would have to set some environment variables manually. Reading these scripts or batch files may help you if you want to set up your environment manually. You can choose to run the program directly from the distribution CD or install it on your computer. For improved execution it is recommended that you install the program. Read the corresponding Install Notes document for directions for installation. On Linux, using the file browser or a terminal, navigate to the directory in which you want to run the program and click or execute runavid-linux (e.g., type ./runavid-linux). This script will set all the required environment variables and will start the program. For detailed instructions, see the Install Notes. On Mac OS X, the script to be run is runavid-mac-tcsh.command. Using the finder or the terminal, navigate to the location from which you want to run the program and then either double-click the runavid-mac-tcsh.command or type ./runavid-mac-tcsh.command. This script will set the required environment variables and will start the program. For detailed instructions, see the Install Notes. On Windows, there are three scripts to run the program: runfromcd-d-drive.bat, runfromcd-e-drive.bat, and runavid-windows.bat. The first two batch files will set all the required environment variables and execute the program if your CD drive is d:\ or e:\. If your CD drive is mapped to a different letter you can set the environment variables manually or install the program as described in the installation instructions (run setup.exe) and then run the program from the hard drive by executing runavidwindows.bat. For detailed instructions, see the Install Notes. 1-6 The First Time When you launch AVID OAV for the first time, the first dialog box that will pop up is the License Agreement, see Figure 2-1. Click Accept if you accept the license terms. Figure 2-1: License Agreement dialog box Once you click Accept, a second dialog box will pop up and request an Activation Key. See Figure 2-2. Contact us at 540.961.0067 or support@avidllc.biz to request your Activation Key. If you click Reject, the License Agreement dialog box will close and the application will terminate. Figure 2-2: Enter an Activation Key The Activation Key can be typed or pasted into the Enter an Activation Key dialog box. Click OK to enter the key; note that you cannot click OK until the key has been entered. If you enter the wrong key, or if you click Cancel, an error message box will pop up 1-7 notifying you that the application is about to terminate. See Figure 2-3. If the key was entered correctly, a Product Activated message box (see Figure 2-4) will pop up notifying you that the program is now active and when it will expire. Figure 2-3: Invalid Key error message Figure 2-4: Product Activated informational message box Clicking O K on the Product Activated message box will close it and will start the program. File Types There are five types of files associated with AVID OAV. They are mission, oav, project, trade study, and component database files. Mission files have a *.mis extension, oav files the *.oav extension, project files the *.prj extension, and trade study files the *.ts extension. The component database files have the *.oavxls extension. An oav file contains all of the information describing an organic air vehicle (OAV) aircraft. To load an oav file select File > Project > Open OAV… from the main menu. Browse to the location of a file with the *.oav extension, click the file name, and press the Open button. The OAV design parameters are loaded and the aircraft is drawn in the Display window. If you look in the data folder supplied with AVID OAV there is an example OAV in the file example.oav. Note that you can also load an oav file by loading a project file that contains an oav file. The status bar on the main window changes to reflect the oav file loaded. A mission file contains all of the information describing the phases of an oav mission. Missions are used to analyze the current OAV. To load a mission file select File > Project > Load Mission from the main menu. Browse to the location of a file with the *.mis extension, click the file name, and press the Open button. The mission definition is loaded and the Mission dialog opens. If you look in the data folder supplied with AVID 1-8 OAV there is an example mission in the file example.mis. Note that you can also load a mission file by loading a project file that contains a mission file. The status bar on the main window changes to reflect the mission file loaded. A trade study file contains optimization information for an OAV. This data encompasses swarm optimization and trade study parameters. To load a trade study file select File > Project > Load Trade Study from the main menu. Browse to the location of a file with the *.ts extension, click the file name, and press the Open button. The optimization parameters are loaded and the Trade Studies and Swarm Based Optimization dialogs open. Note that you can also load a trade study file by loading a project file that contains a trade study file. A project file provides the means to associate OAVs, missions, trade studies and swarm optimizations together. For instance, a user may have a couple of missions for a particular OAV. The user could associate the two missions with the OAV in a project file. To load a project file select File > Load Project from the main menu. Browse to the location of a file with the *.prj extension, click the file name, and press the Open button. Each of the files contained in a project are loaded. The OAV is drawn in the Display window. The Swarm Based Optimization, Trade Studies, and Mission dialogs open. The Project Organizer dialog also opens. This dialog gives the user a way to manage a project. Note that the status bar of the main window changes to reflect the oav and mission files loaded. Component database files are where non-airframe components are defined. The file initialdata.oavxls is provided with AVID OAV and should not be edited. The user may add component data for the propulsion, power, and electrical devices by selecting File > Edit Initial Data from the main menu. Multiple files can be included under the File > User Options item in the main menu. These features are described in greater detail in Chapter 3: Program Customization. The Project Organizer The project organizer allows the user to manage a project. The project consists of a list of OAVs, a list of missions and a list of trade studies. To open the Project Organizer dialog (Figure 2-5) select File > Project > Project Organizer from the main menu or load a project file as described in the previous section. If a saved project is not loaded then the organizer shows any AVID OAV files that are otherwise currently open. If no files are open and no saved project is loaded the organizer shows only the types of files available. To create a project, open the project organizer. Add a file to the project by selecting the type of file you want by clicking the corresponding type in the tree view (oav, missions, or trade studies). Press the Add button. Browse to the file you wish to add and press the Open button. The path and the name of the file are now shown in the tree view under the appropriate heading. 1-9 Once you have added all of the desired files to the project, click the Apply button to register the changes to the current project and keep the Project Organizer dialog open. Alternatively, you can click the OK button to register the changes and close the dialog. To save the project you have created select File > Save Project from the main menu. Type in a filename and be sure that it has the *.prj extension. Press the Save button to save the project file. The user can also remove files from a project using the organizer. In the tree view click the file you wish to remove from the project and press the Delete button. The file is removed from the tree view. The user can also load each separate file in the project through the organizer. Select the file you wish to load by clicking it in the tree view. Press the Load button. The file is loaded and if applicable, the appropriate dialog is opened to allow manipulation of the file. Pressing the Cancel button will discard any changes made to the project and will close the Project Organizer dialog. Figure 2-5: Project Organizer dialog 1-10 Mission Analysis As described in the previous section, load the example oav and mission files. With an OAV and a mission data file loaded you can now evaluate the example OAV with the example mission. Click Compute Results on the Mission dialog box. A window named Results from Mission will pop up. The results window displays a summary of performance data for parameters and settings defining the loaded OAV. You can save these results as an html file, which can then be loaded into other programs. See Chapter 7 for more details on how the mission analysis works. For now click Cancel to close the results window. Clicking OK on the Mission dialog box will accept the results from the mission and close the dialog box. Aircraft Optimization AVID OAV automates the manipulation of the aircraft design with the goal of satisfying one or more objectives. On the main window, click OAV > Optimize > Swarm Optimization. The Swarm Based Optimization dialog box will pop up. Chapter 6 will explain how this dialog box works and review the fundamentals of the Particle Swarm Optimization (PSO) method. Closing the program Before you exit the program make sure that you have saved all of your data. To save an OAV file select File > Project > Save OAV. To save the OAV to a different file select File > Project > Save OAV As… from the main menu; a save file dialog (Figure 2-6) opens. Enter the desired name of the file followed by the *.oav extension and press the Save button. To save the current mission to a file select File > Project > Save Mission from the main menu; a save file dialog opens. Enter the desired name of the file followed by the *.mis extension and press the Save button. To save the current trade study and swarm optimization select File > Project > Save Trade Study from the main menu; a save file dialog opens. Enter the desired name of the file followed by the *.ts extension and press the Save button. To save the current project select File > Save Project from the main menu; a save file dialog opens. Enter the desired name of the file followed by the *.prj extension and press the Save button. Saving a project file forces AVID OAV to save each file in the project. Any oav, mission, or trade study files associated with the project will be saved to the file names already specified in the project organizer. 1-11 With all of your data saved you can safely exit the program. All windows that opened in this session will close and the program will terminate. Figure 2-6: Save As Dialog Box Conclusion You have seen how to start the program and how to load and save AVID OAV files. See the Tutorial for more information on how to model an OAV and how to create a mission. The rest of this User Guide will describe all the available options and will give you background information on the fundamentals behind the calculations performed by the program. 1-12 Chapter 3 Program Customization This chapter discusses the customization features of AVID OAV. These features allow the user to adjust the program to his or her preferences. Additional aircraft components may also be defined and introduced into AVID OAV using customization features. Editing Initial Data Files With AVID OAV you have the ability to create OAV components based on objects located in the default initial data file (initialdata.oavxls). You can save these new components in your own user-defined data file. You can instruct AVID OAV to load your data files every time the application is started. The ability to create custom components and save them in your own data file provides the capability to separate your organization’s proprietary information from that provided with AVID OAV. It also allows control of available component data between projects. You can generate components with customized characteristics and then decide what information you share. Selecting File > Edit Initial Data from the main menu invokes the Edit Initial Datafiles dialog. As seen in Figure 3-1 the editor displays the components that exist in the initial data files. Components are grouped by type and displayed in a tree view. For example, by clicking on the plus sign (+) or arrow (>) next to cOAVElectrical, you expand the tree view to show you all electrical devices defined in the initial data files. Clicking on the plus sign or arrow next to one of these objects displays the object’s properties as parameter / value pairs. There are three columns in the tree view. The Name column contains the name of the class, the object, or the parameter. The Data column contains the values of the parameters. The Loaded from File column shows you the file from which the object was loaded. Right-clicking (control key + click for Mac users) displays different context-sensitive menus depending on where you click. If you right-click on a class name, New is the only option and allows you to create new objects of the specified class. There are eight classes supplied with AVID OAV: cAuxPropeller, cOAVBattery, cOAVElectrical, cOAVEngComponent, cOAVEngine, cOAVGenerator, cOAVPowerConvCond, and cOAVPropulsionBattery. Each one corresponds to a type of OAV component available for installation within the application. 1-13 Figure 3-5: Edit Initial Datafiles Dialog When a new object is created by clicking New, the new component is automatically given the name “New class-name”, has blank parameter values, and reads as “<>” in the Loaded from File column. For instance, right clicking on cOAVElectrical and selecting New creates New cOAVElectrical with blank parameters. The new component must be assigned to a data file. As shown on Figure 3-2, the dialog will not allow you to click OK or Apply until every object has been assigned to a file. Figure 3-2: All objects must be assigned to a file 1-14 To change the name for new objects click the name in column 1, type in a new name and press enter. To change the value of a parameter click the area in column 2 adjacent on the same row as the parameter you wish to change, enter a value, and press enter. If you right-click (control key + click for Mac users) on an object name there are three options: Copy, Delete, and Assign to File. If the object is one of the defaults supplied with the “initialdata.oavxls”, Copy will be the only option available. Selecting Copy will create a new object named “object-name_copy” with the same parameter values as the original and not assigned to any data file. Choosing Delete allows you to remove unwanted objects. Note that when creating a new component, it is usually easier to copy a pre-existing component and modify a small number of parameters instead of creating an entirely new component. Right clicking on a newly created component and selecting Assign to File brings up the dialog box shown in Figure 3-3. You can select an existing oavxls file or create a new one by typing a new file name. The Loaded from File column will no longer say, “<>” and will instead reflect the file name just entered. Figure 3-3: Assign to File dialog 1-15 After assigning all the newly created OAV components to an oavxls file, the dialog box will allow you to click OK or Apply. New components may be assigned to the same or different oavxls files. Clicking OK or Apply will write the new information to your file system, creating the new file(s) as necessary. Selecting Apply saves the new components without closing the Edit Initial Datafiles dialogue box. The new component is ready to use once you have assigned the new component to a file and pressed the Apply or OK button. Setting Personal Preferences Selecting File > User Options from the main menu invokes the User Options dialog box. As shown in Figure 3-4, the User Options dialog allows you to specify three types of user preferences: color, additional initial data files, and whether or not to draw coordinate axes in the Display window. Figure 3-4: User Options dialog The User Options dialog box lets you decide what background colors you would like to use for the tables used in the program. You can choose both the background of modifiable, or input fields, and non-modifiable, static or output, fields. Clicking on the Change button for either the Current Table Background Color or the Current Color of Modifiable Fields will pop up the Colors dialog box. Figure 3-5 shows the Colors dialog as it appears on Mac OS. This dialog box allows multiple ways to specify a color. 1-16 Once the desired color is obtained, click OK to use it on the User Options dialog. Note that setting these color preferences also affects any tree view in the application. The background color of a tree view is the same as the background of tables. Any modifiable fields listed in a tree view are the same color as the modifiable fields in tables. Figure 3-5: Color selection On the bottom of the User Options dialog box you can choose additional data files that AVID OAV will load every time it starts. Below Additional Component-List Datafiles there is a list box, an Add button, and a Delete button. If the only file loaded at program start-up is the default “initialdata.oavxls” file, then the list box will be empty. You can specify additional data files by clicking Add. This launches a file dialog which can be used to browse for and select the desired file. The file dialog only allows you to select files with the *.oavxls extension. Select the desired oavxls file and click Open. The file you selected will now be shown in the list box. Files may be removed from the list by selecting the file and then clicking Delete. The checkbox labeled Draw X, Y, and Z Axes toggles whether or not x, y, and z coordinate axes are drawn in the Display window. The axes are drawn with the aircraft so that the user understands the orientation of the design space. Figure 3-6 shows the Display window with the axes enabled. The axes are especially useful showing the origin of the design space. Being able to visualize the origin is helpful when positioning individual geometric components. A geometric component’s position is relative to the origin. 1-17 Figure 3-6 Axes Shown in the Display Window Clicking OK closes the User Options dialog box, saves your newly defined preferences into the avid.rc file in your home directory, and makes any changes effective. Clicking Cancel will abandon any modifications made and will leave your avid.rc file unaffected. The components defined in the specified additional data files will now be listed in the appropriate OAV > Properties dialogs. For example, if you have created your own battery, as a new cOAVBattery, you will be able to select it from the Select a Battery Model combo box; which is on the Battery tab of the Propulsion and Power dialog (click OAV > Properties > Propulsion and Power to open it). Display Window Options Under the View menu you can choose how the geometry is displayed. The options Single, Side by Side, and Multiple define the number of views of the aircraft that are shown in the Display window. The default view is Single and is shown in Figure 3-7. You can specify the angle of view for any view in the Display window. CTRL + click (meta key + click on MacOS) on the Display window and a menu pops up with the following view angle options: Isometric, Top, Side, and Front. See Figure 3-12. The 1-18 Isometric view shows the aircraft pointing down and to the left (Figure 3-7). You can change the view angle by selecting one of the other options. Figure 3-7: Single view (Isometric) of an OAV Side by Side view displays two views of the aircraft. As shown in Figure 3-8, the default view angles are the Isometric, and the Top. As in the Single view case CTRL + click on the Display window to show a menu that allows the selection of the desired view angle. This menu is context-sensitive and will only change the view selected. Figure 3-8: Default Side by Side view of an OAV 1-19 As shown in Figure 3-9, Multiple view displays four view angles on the same screen. With the context-sensitive menu you can change each of these view angles independently. Figure 3-9: Default Multiple views of an OAV Geometry Rendering Options The first three options under the View menu are Shaded, Transparent, and Wireframe. These options define how the geometry is rendered in the Display window. Corresponding buttons are located on the toolbar. Figure 3-10 represents an OAV rendered as Wireframe, Shaded, and Transparent respectively. Note that in a Wireframe OAV you can assign the wireframe color to each component by changing the Color field in a component’s General Params tab. In an OAV rendered as Shaded a component’s surface color is specified by the Surface Material field in its General Params tab. See Chapter 4 for more information. A Transparent OAV is useful for visualizing the internal components of the aircraft. 1-20 Figure 3-10: Wireframe OAV, Shaded OAV, and Transparent OAV Display Window Controls AVID OAV provides several view manipulation methods. The user can rotate and move the aircraft inside the Display window. The user can also zoom closer to or farther from the OAV. All of these controls are accessible through the Controls dialog. Selecting View > Display Controls from the main menu opens the Controls dialog (Figure 3-11). 1-21 Figure 3-11: Controls Dialog The Roll, Pitch and Y a w sliders control the rotation of the rendered aircraft. Manipulating the Roll slider rotates the aircraft about the x-axis. Yaw is a rotation about the z-axis and Pitch is a rotation about the y-axis. The X Translation, Y Translation and Z Translation sliders control the movement of the rendered aircraft. Manipulating the X Translation slider moves the aircraft along the x-axis. The Y Translation and Z Translation sliders move the aircraft along the corresponding axis. The last slider on the Controls dialog is the Zoom slider. Manipulating this slider allows you to zoom in on the scene rendered in the Display window and to zoom out from the scene. The Reset button on the bottom of the dialog resets the values of rotation, translation, and zoom factor to their initial values. This causes the aircraft to be rendered as it was before any display control actions. In addition to the Controls dialog, you can manipulate the display window controls using your mouse and keyboard. An emulated trackball allows you to rotate the aircraft by clicking in the Display window and dragging the mouse with the button pressed. 1-22 Figure 3-12: Display Window Pop-Up Menu To move the aircraft along axes use the directional arrows on your keyboard. The up and down arrows move the aircraft along the y-axis. The up arrow is a positive move and the down arrow is a negative move. The left and right arrow keys move the aircraft along the x-axis. Left is a negative move and right is a positive move. There are currently no keyboard controls to move the aircraft along the z-axis. Zoom in and out by using the plus “+” and minus “-“ keys on your keyboard. Pressing the plus key will make the aircraft appear to grow. You are zooming in on the scene. Pressing the minus key will make the aircraft appear to shrink. You are zooming away from the scene. You can also reset the display to its starting point by pressing the “R” key on your keyboard. This has the same effect as pressing Reset on the Controls dialog. 1-23 Chapter 4 The Geometric Component Editor Introduction To access the airframe component editor select OAV > Edit Airframe Components from the main menu. From this dialog, airframe components can be added, removed, or modified. Figure 4-1 shows the Edit Airframe Components dialog. Figure 4-1: Airframe Component Editor Dialog Adding a New Component To add a new component, click on the drop down box in the upper left-hand corner. Select a component type from the list of the available component types or select one of the predefined components (for example, an Auxiliary Propeller) that are stored in the 1-24 initial data files. At this point the Geometry Component Dialog appears and allows the parameters for this component to be specified. This dialog contains the following tabs: Location, General, Shape, Airfoil or Cross Section (depending on the type of component), Mass Properties, and Fuel Tank. Location Tab Figure 4-2: Location Tab of the Geometry Component Dialog This tab, see Figure 4-2, specifies how the component is oriented with respect to the OAV. The X Translation, Y Translation, and Z Translation fields display the position of the component relative to the OAV's origin. The X Rotation, Y Rotation, and Z Rotation fields display the rotation of the component about the x, y, and z axes of the component. First, the x rotation is applied to the component, then the y rotation, and finally the z rotation. The translations are input in units of inches and the rotations are in degrees. 1-25 General Tab Figure 4-3: General Tab of Geometry Component Dialog This tab, see Figure 4-3, displays options that are available for every type of geometry component. The Local Symmetry and the Create Duplicate About Axis pull down boxes allow mirroring of the component about the plane determined by the selected axes. Local Symmetry is currently not available. Create Duplicate About Axis will mirror the component about a plane through the OAV's origin. For the selected symmetry type, a new component that is symmetric to the original component will be created, and will be displayed in the installed component list. The Line in u and Line in w settings control the granularity of the component's surface rendering only. Increasing the number will increase the density of the wireframe rendering of the surface. The surfaces used with mathematical analysis are C2 continuous bicubic B-spline surfaces. Line Type will determine the style of line used when displaying the wire frame rendering of the geometric component. Likewise, Color will determine the color of the component when viewed in wire frame rendering. 1-26 Shape Tab Figure 4-4: Shape Tab of Geometry Component Dialog The Shape tab, see Figure 4-4, allows modification of each component's design parameters. The parameters seen in this tab vary according to component type. The parameters of each component type are described below. 1-27 After Body Figure 4-5: After Body Schematic Length 1 Angle 1 Angle 2 The distance denoted by “LENGTH” in Figure 4-5. It is the distance between the front cross section and the rear cross section. The angle denoted by “ALPHA 1” in Figure 4-5. It is the angle between the surface tangent at the front cross section and the line connecting the two cross sections. The angle denoted by “ALPHA 2” in Figure 4-5. It is the angle between the surface tangent at the rear cross section and the line connecting the two cross sections. 1-28 Duct Figure 4-6: Duct Schematic Length The distance denoted by “Duct Length” in Figure 4-6. It is the overall length of the duct. Diameter The distance denoted by “Diameter” in Figure 4-6. This shows the diameter of the duct, which is linked to the propeller size if Link Diameter to Prop Diameter Design Variable is checked. Otherwise, the user may manually specify the duct’s diameter. Propeller Surface Length The distance denoted by “l” in Figure 4-6. Corresponds to the width of the propeller, and will determine the size of the flat cut into the airfoil (represented by the bold line in Figure 4-6) Duct Location The distance denoted by “x” in Figure 4-6. It is the distance from the leading edge of the duct to the propeller center. Cut Location Can be set to either “Inside” or “Outside”. Determines whether the cut into the duct is on the inside or outside of the duct. Note: 1-29 Setting the cut location to “Outside” will not change the Diameter parameter from the inside diameter to an outside diameter. 1-30 Mid Section Figure 4-7: Mid Section Schematic Length The distance denoted by “LENGTH” in figure 4-7. It is the overall length of the component, measured from the front cross section to the rear cross section. Nose Figure 4-8: Nose Schematic Nose Length Tip Angle Shoulder Angle Dive Angle The distance denoted by “LENGTH” in Figure 4-8. It is the distance from the cross section center to the tip of the nose. The angle denoted by “TIP ANGLE” in Figure 4-8. The angle denoted by “SHOULDER ANGLE” in Figure 4-8. The angle denoted by “DIVE ANGLE” in Figure 4-8. The angle between the tip and the normal vector at the center of the cross section. 1-31 Pod Figure 4-9: Pod Schematic Nose Length The distance from the front tip to the front cross section (Length1 above). Midsection Length The distance from the front cross section to the rear cross section. (Length2 above) Afterbody Length The distance from the rear cross section to the rear tip (Length3 above). Angle 1 The angle denoted by “Alpha 1” in Figure 4-9. It is the angle between the surface tangent at the front tip and the line from the cross section to the tip. Angle 2 The angle denoted by “Alpha 2” in Figure 4-9. It is the angle between the surface tangent at the rear tip and the line from the cross section to the tip. Note that on the Shape tab of the Geometry Component Dialog for a Pod has an extra option. You can decide to link the location of the pod to the propeller diameter design variable. This is intended to ease resizing and optimization tasks. To enable this relationship, check the Link Location to DV Propeller Diameter check box. You can now specify an offset for the pod with respect to propeller diameter. 1-32 DA Propeller Figure 4-10: Propeller Blade Schematic Number of Blades Number of blades equally spaced around hub. Tip Chord Length The distance denoted by “Ctip” in Figure 4-10. It is the overall length of the tip airfoil. Root Chord Length The distance denoted by “Croot” in Figure 4-10. It is the overall length of the root airfoil. Diameter Overall diameter of the propeller. Hub Diameter The diameter of the hub, on which the blades are mounted. Quarter Chord Sweep Not depicted in the figure. The quarter chord is the line set back 1/4 of the width of the blade from the leading edge. The quarter chord sweep is the angle between the quarter chord and the perpendicular from the centerline. Twist Not depicted in the figure. The angle the tip airfoil will be rotated relative to the root airfoil. Negative twist will make the tip airfoil tilt nose down. Incidence Not depicted in the figure. The pitch angle of the blade with respect to the hub Dihedral Not depicted in the figure. The angle of the airfoil with respect to the horizontal when seen from the front. BVE Propeller Num of Blades Hub Diameter Same as Number of Blades for the Propeller component. Same as Propeller component. 1-33 Tip Diameter Same as Diameter for the Propeller component. The rest of the inputs on the Shape tab of an Auxiliary Propeller describe the shape of the individual propeller blades. You may specify a series of radial stations that describe the shape. The Load RadialStation button allows you to load pre-defined parameters. You can also use a propeller performance map with an Auxiliary Propeller component. On the Shape tab check the Enable Thrust Map check box. This will allow you to load a propeller performance map. To do so, select File > Load Propeller Map, browse to the file and open it. Now you can view the propeller map data by pressing the View Thrust Map button on the Shape tab. A propeller map is processed XRotor output and provides very good thrust estimates for high velocities. Stator Figure 4-11: Stator Schematic The stator inputs are identical to those of the propeller except that the default incidence and twist angles are set to 0. The diameter of the stator is linked to the diameter of the propeller to ease resizing and optimization tasks. Number of Blades Number of blades equally spaced around hub. Tip Chord Length The distance denoted by “Ctip” in Figure 4-10. It is the overall length of the tip airfoil. Root Chord Length The distance denoted by “Croot” in Figure 4-10. It is the overall length of the root airfoil. Diameter Overall diameter of the propeller. 1-34 Hub Diameter The diameter of the hub, on which the blades are mounted. Quarter Chord Sweep Not depicted in the figure. The quarter chord is the line set back 1/4 of the width of the blade from the leading edge. The quarter chord sweep is the angle between the quarter chord and the perpendicular from the centerline. Twist Not depicted in the figure. The angle the tip airfoil will be rotated relative to the root airfoil. Negative twist will make the tip airfoil tilt nose down. Incidence Not depicted in the figure. The pitch angle of the blade with respect to the hub Dihedral Not depicted in the figure. The angle of the airfoil with respect to the horizontal when seen from the front. Vane Figure 4-12: Vane Schematic The vane inputs are nearly identical to those of the propeller except that the default incidence and twist angles are set to 0. The inputs for a cutout to account for vane-tovane clearance are included. The diameter of the vane is linked to the diameter of the propeller to ease resizing and optimization tasks. Number of Blades Number of blades equally spaced around hub. Tip Chord Length The distance denoted by “Ctip” in Figure 4-10. It is the overall length of the tip airfoil. 1-35 Root Chord Length The distance denoted by “Croot” in Figure 4-10. It is the overall length of the root airfoil. Diameter Overall diameter of the propeller. Hub Diameter The diameter of the hub, on which the blades are mounted. Cutout Location The location of the cutout in Figure 4-12. Cutout Angle The angle denoted by “cutout” in Figure 4-12. Twist Not depicted in the figure. The angle the tip airfoil will be rotated relative to the root airfoil. Negative twist will make the tip airfoil tilt nose down. Incidence Not depicted in the figure. The pitch angle of the blade with respect to the hub Dihedral Not depicted in the figure. The angle of the airfoil with respect to the horizontal when seen from the front. Wing Root Chord Length The overall length of the root airfoil. Tip Chord Length The overall length of the tip airfoil. Span The distance from the root airfoil to the tip airfoil*2. Quarter Chord Sweep The quarter chord is the line set back 1/4 of the width of the wing from the leading edge. The quarter chord sweep is the angle between the quarter chord and the perpendicular fuselage centerline. Dihedral The angle of the airfoil with respect to the horizontal when seen from the front. Twist The angle the tip airfoil will be rotated relative to the root airfoil. Negative twist will make the tip airfoil tilt nose down. Fuselage The Fuselage component is actually the combination of the Nose, Midsection and Afterbody components. You can refer to the descriptions of the Shape tabs for the constituent components to learn more about Fuselage shape parameters. 1-36 Airfoil Tab Figure 4-13: Airfoil Tab of Geometry Component Dialog The Airfoil tab, as seen in Figure 4-13, is available for duct, wing, vane, stator, and propeller components. For components with a single cross section, like the duct, a single airfoil can be specified. For components with root and tip cross sections, like wings, an airfoil can be specified for each. Airfoils have the following parameters: Airfoil Type Input in the form of the NACA 4-digit code. The first digit defines the maximum camber in percent chord, the second defines the location of the maximum camber in tenths of chord, and the last two digits define the airfoil maximum thickness in percent of chord. Currently not available. Corresponds to the curvature of the airfoil. Measures maximum distance of wing surface from the mean camber line as a percentage of chord length. Currently not available. Measures the distance from the leading edge in percentage of chord length. Camber Camber Location 1-37 Camber Thickness Currently not available. Measures the maximum thickness of the airfoil in percentage of chord length. Cross Section Tab Figure 4-14: Cross Section Tab of Geometry Component Dialog The Cross Section tab, in Figure 4-14, is available for nose, mid-section, pod, and afterbody components. For components like the nose, a single airfoil can be specified. For components like the mid-section an airfoil can be specified for its beginning and end. The number of cross sections and points per cross section control the smoothness of the lofted resulting shape. There are two types of cross sections: elliptic and circular (conic). Each has its own parameters which are explained below: 1-38 Elliptic Cross Section Figure 4-15: Elliptic Cross Section Radius 1 Radius 2 The distance from point 1 to 2 in the Y direction, denoted by “RADIUS 1” in Figure 4-15. The distance from point 1 to 3 in the Z direction, denoted by “RADIUS 2” in Figure 4-15. 1-39 Circular (Conic) Cross Section Figure 4-16: Circular (Conic) Cross Section X,Y,Z coordinates for P1, P2, P3, P4, and P5 - as depicted in Figure 4-16. Note P0 is always located at the origin. Rho 1 The ratio of the distance from point a to point b to the distance from point b to P2 in Figure 4-16. If the ratio is less than .5, the curve is an ellipse. If the ratio is .5, the curve is a parabola. If the ratio is greater than .5, the curve is a hyperbola. Rho 2 The ratio of the distance from point c to point d to the distance from point d to P4 in Figure 4-16. If the ratio is less than .5, the curve is an ellipse. If the ratio is .5, the curve is a parabola. If the ratio is greater than .5, the curve is a hyperbola. 1-40 Mass Properties Tab Figure 4-17: Mass Properties Tab of Geometry Component Dialog The Mass Properties tab, shown in Figure 4-17, displays the weight (lb), density (slug/in3), thickness (in), center of mass offset (in), and moments of inertia for the component (lb*in*sec2). The user can manually set the values of these quantities. However, they can also be calculated from the component’s geometry if a density is given. There are two methods available for calculating these mass properties: one in which the component is considered a homogeneous solid and the other is to consider the component a thin shell with a given thickness. To calculate the “solid” mass properties, first supply a value for the density, and then click the button Reset as Solid. To calculate the “shell” mass properties, first supply a density and thickness, and then click the button Reset as Shell. Either of these actions will populate the fields for mass, moments of inertia, and the center of mass offset. The Offset of C.M. is the location of the center of mass relative to the component's origin in its local coordinate system. Ixx, Iyy, and Izz are moments of inertia respectively about the X, Y, and Z axes through the component's center of mass. Ixy, Ixz, and Iyz are the products of inertia with respect to the 1-41 component's center of mass. The Non Optimal factor is a scalar multiplier applied to each inertial value, but is currently not available. Note: • The density is specified in units [slugs/in3]. If the density of a material is specified in lbf/in3, it must be divided by 32.2 ft/sec2 to convert it to the proper units. • The mass properties values in this dialog default to zero for all new components. The user must initialize these values to ensure accurate overall vehicle mass properties. • The accuracy of the calculated values using the “Solid” and “Shell” buttons is dependent upon the fineness of the approximation of the smooth b-spline surface of the component. The calculated mass property values for components with default settings can have up to 10% error in their accuracy. Therefore to improve the accuracy, increase the number of cross sections and number of points per cross section specified for the component. • To ensure proper behavior, components should be created and visible in the graphics display window before calculating mass properties via the “Solid” or “Shell” buttons. Densities of Common Aerospace Materials Density [slug/in3] 0.0017629 0.0013474 0.0016506 0.0014934 0.0016618 0.0016057 0.0016506 0.0010892 0.0030318 0.100385 0.0099711 0.0088707 0.0050529 0.0035932 0.0016394 0.0001740 0.0003593 Material Plastics/Composites Carbon Epoxy Composite Epoxy Nylon 46, glass reinforced Polyetheretherketone (PEEK), unreinforced Polyetheretherketone (PEEK), glass reinforced Polyetheretherketone (PEEK), carbon reinforced Silicone Spectra Metals Aluminum (6061-T4) Copper Nickel Stainless Steel (ANSI 202) Titanium Ceramics Silicon Nitride (ceramic) Woods Balsa wood Basswood Foams 1-42 Glassy Carbon Foam Core PVC Foam Core 0.0004379 0.0000621 Fuel Tank Tab Figure 4-18: Fuel Tank Tab of Geometry Component Dialog The Fuel Tank tab, as seen in figure 4-18, is used to designate a component as a fuel tank. A component that has the box “Use Component as a Gravity-Based Fuel Tank” checked will be used as a fuel tank if gravity-based fuel analysis is enabled (see Chapter 5, Edit Mass Properties section). Fuel Density is the density, in slugs/inch^3, of the fuel that the tank will carry. Ullage is the amount of empty space, in percent of total volume available, left in filled tanks to account for expansion of the fuel at high altitudes. Internal Structure is the amount of the component’s volume, in percent of total volume available, reserved for the structures inside of the tank such as pumps and baffles. Number of Pitch Angle Samplings and Number of Fuel Level Samplings control the accuracy of the mass property calculations of the fuel. Larger numbers may yield more accurate results, but could reduce application performance. 1-43 Calculated Maximum Fuel Capacity is the weight, in pounds, of the fuel that the fuel tank can carry. The geometric parameters of the component are used to calculate a maximum available volume, from which Internal Structure and Ullage are removed. Finally, the Density of the fuel is multiplied to the calculated volume to determine the maximum fuel weight that the component can carry. It is important to note that this tab will not work for components that are being newly created. Components must appear in the Installed Components table of the Edit Airframe Components dialog and have been applied before the Fuel Tank tab can be used. It is also important to note that creating a fuel tank component does not enable gravitybased fuel analysis. Please read Chapter 5, Edit Mass Properties section for information about enabling gravity-based fuel analysis. Modifying Components To modify a component’s properties, select it from the list of installed components on the right of the dialog and click the Modify button to display the Geometry Component Dialog. A description of how to use this dialog is given in the "Adding a New Component" section above. Uninstalling Components To uninstall a component from the OAV, select it from the list of installed components, and click the Uninstall button. This will move the component to the list of available components on the left of the Edit Airframe Components dialog. These components are not used in any of the calculations pertaining to the OAV nor are they drawn in the Display window. Deleting Components Once a component has been uninstalled, it may be deleted be selecting it from the available components list and clicking the Delete button. Copying Components If multiple copies of a particular component are needed in the OAV, this can be accomplished by selecting a component from the available component list and clicking the Copy button. To copy a component that is already installed, it must first be uninstalled and then copied (installed) multiple times. 1-44 Chapter 5 Setting the OAV Properties AVID OAV allows you to specify detailed information about the OAV you are designing. Chapter 4 discussed the types of geometric components that can be used to create an OAV. This chapter will show you how to define all the other properties describing an OAV. Aerodynamics Selecting OAV > Properties > Aerodynamics invokes the Aerodynamics dialog as shown in Figure 5-1. This dialog provides a report about conventional aerodynamic characteristics as they apply to the currently loaded OAV. Figure 5-1: Aerodynamics Dialog You may specify the velocity (ft/sec), thrust (pounds), temperature (degrees Fahrenheit) and altitude (feet) conditions for the aerodynamic calculations. Selecting the Wind 1-45 Tunnel Features, option disables the thrust input but allows for an RPM ranges and an Angle-of-attack range (in degrees) to be entered. This feature allows data to be obtained that matches a particular wind tunnel test condition(s). The selection of the wind tunnel features option also enables the geometry radio buttons and the output axis system selection button. The geometry radio buttons allows specification of the components to use for the aerodynamic buildup. The All Components radio button allows computation of aerodynamic data for the complete configuration. The Skip Vanes button produces results for the complete configuration, minus the effect of the vanes. Only vane aerodynamics are computed with the selection of the Deflect Vanes radio button. The Output Results in Six-Degrees-of-Freedom Format option provides for force data in the body X, Y, and Z directions and moments about the X, Y, and Z-axis to be computed. The default is for the computation of lift, drag, and pitching moment. Pressing Response will generate the requested aerodynamic data displayed in a table (figure 5-2). Note that the data is computed over an angle-of-attack range of 0° to 90° at one degree increments when the wind tunnel feature option is not selected. Figure 5-2: Tabular Aerodynamic Data The Aerodynamics Results window (figure 5-2) provides functionality to Plot the data to the screen and to Save the data to a file. Note that the Carpet Plot button is not active in the current release. Selection of the Plot option results in the “Define Two-Dimensional Plot” dialog shown in figure 5-3. This dialog allows selection of the independent and dependent plot variables as well as the specification of the plot title. The dialog in the left half of figure 5-3 corresponds to that displayed when the “Wind Tunnel Features” option is not selected; the dialog on the right is typical of that displayed when wind tunnel features are specified. Here, the user can select from among Velocity, RPM, and Alpha as the independent plotting variable while specifying the value of the remaining two variables from the pull down lists. The dependent plotting variable(s) may be selected from the available variable list by highlighting the variable name and then selecting Add. Variables may be removed from the selected list by highlighting the 1-46 variable name in the list of selected variables and selecting Remove. The data is plotted to the screen upon selection of Plot. A typical plot is presented in figure 5-4. Selecting the Save button on the aerodynamics results window displays the Save dialog shown in figure 5-5. Through this dialog, the user may select the location to save the, specify the name by which the file is saved, and may specify the saved file format. Currently, the user may select between HTML, a comma delimited data file (CSV), or as an array of data in a MATLAB .m data file. Figure 5-3: Plot Specification Dialogs Figure 5-4: Plotted Aerodynamics Data 1-47 Figure 5-5: Aerodynamics Results Save Dialog Engine Modeling AVID OAV uses a response surface methodology to model the performance of a fossilfuelled engine. Chapter ?? discusses the response surface model, its implementation and limitations. This section will show you how to implement an engine response surface model in AVID OAV and take advantage of the other additional engine performance plotting features. Inputting an engine response surface model into AVID OAV An engine must first be installed in the vehicle before the engine response surface method can be used. This task can be done in the Propulsion and Power dialog box. Instructions on how to do this can be found in Chapter ?? Select OAV > Properties > Engine Modeling to bring up the Engine Modeling dialog box. This dialog box is shown in Figure 5-6. Select the Enable Engine Response Surface checkbox to have AVID OAV use the engine response surface. Enter the sealevel temperature that corresponds to the conditions for the response surface data in the Sea Level Temp field. Select either a Piston or Turbine engine in the Engine Type box. Notice that the values for the Max Power and Limit RPM fields is grayed out. These two engine properties are in the XX section. See Chapter ?? for more details. If the engine does not have a limit RPM, enter the value of the Maximum RPM instead. Enter values for the response surface coefficients for both the SFC and Power calculated as explained in the previous section. If you are unsure of which fields in which to enter 1-48 the response surface coefficients, move your mouse pointer over the field to reveal an explanation of its use. Also, enter the thrust lapse coefficient for the particular engine. If this is unknown, use a value of 0.7 for turbine engines or 7.55 for piston engines. The slider bars may also be used to change the values of the response surface constants and thrust lapse coefficient. This is particularly useful when creating or modifying the SFC and/or power behavior for the engine. The slider bars can be manipulated to change the shape of the SFC and power curves displayed below the input boxes. Size the dialog box larger to reveal more detail in the displayed SFC and power curves. Entering an altitude in the Altitude field at the top of the dialog box will adjust the behavior of the displayed SFC and power curves at that particular altitude. Entering an altitude will not affect the behavior of the response surface model, as it only applies to the SFC and power curves displayed in this dialog box. It should be noted that the SFC and power curves displayed show the response surface results for an RPM ratio (RPM/ Maximum RPM) range of 0 to 1. However, the user must keep in mind that although plotted in the box, the response surface model only applies to ranges of the RPM ratio where the initial modeling data is valid. Any data shown outside of the valid ranges represents an extrapolation of the response surface model. The user should make sure that the engine RPM reported in AVID OAV is within this valid range. Click on the Apply button at the bottom of the dialog box to apply the changes to the vehicle. Figure 5-6: Engine Modeling Dialog Box. 1-49 Plotting Engine Performance The engine performance predicted by the response surface model can be further investigated using the plotting function within the Engine Modeling dialog box. First specify an altitude at which the performance of the engine is to be predicted. For plots that involve a variation in altitude, the altitude field sets the highest altitude at which the plotting function will be evaluated. For example, if plotting the predicted Altitude vs. Max Power performance of the model, the results will have an altitude range between 0 and the value specified in the altitude field. Once the altitude field has been specified, select a plot from the plotting pull-down menu. A second window will appear like that shown in Figure 5-7. This window reports the table of data of the quantities that is to be plotted. Pressing the Save button at the bottom will allow you to save the table of data either as an html, comma-separated value or MATLAB format. Pressing the Plot button will bring up a Define Two-Dimensional Plot dialog box like that shown in Figure 5-8. In this dialog box, select the quantity in the Available box under Dependant variables. Click on the Add button to select that quantity for plotting. Press the Plot button to display the selected plot in a Plot Dialog box that is displayed. Figure 5-7: Engine modeling results box. 1-50 Figure 5-8: Define Two-Dimensional Plot dialog box. Generic Engine Models Table 5-1 gives representative values of the response surface inputs for both piston and turbine engines. Generic Piston Piston 59°F 6000 60 HP 5600 40.0 -50.0 50.0 -0.3 2.0 -0.6 7.55 Generic Turbine Turbine 59°F 5000 50.0 38.0 8.0 1.1 -0.1 1.7 Engine type Sea Level Temperature Maximum RPM Maximum Power Limit RPM Quadratic coefficient for SFC Linear coefficient for SFC Constant coefficient for SFC Quadratic coefficient for Power Linear coefficient for Power Constant coefficient for Power Thrust lapse coefficient Table 5-1: Sample response surface input values for a piston and turbine engine 1-51 Geometry The Geometry dialog box, shown in Figure 5-9, allows you to enter all geometric properties that affect more than one component. The user inputs to this dialog box vary depending on whether you want to use the component-based or the vehicle-based aerodynamics. By default component-based aerodynamics will be used and the Component-Based Aerodynamics check box is checked. To use vehicle-based aerodynamics, click on the Coefficient-Ratio-Based Aerodynamics check box. Note that checking this check box makes CfnToCftRatio and Cft user inputs. These two variables represent the force coefficient in the directions tangential (axial) and normal to the duct/propeller axis of rotation. Note that the value entered for CfnToCftRatio is the ratio of the normal force to the tangential force and not a pure force. Lip Radius, Pylon Packaging Factor, and Maximum Allowable Launch Box Width are always user inputs, independent of the aerodynamics method selected. Lip Radius is used to calculate the Duct Outside Diameter. Pylon Packaging Factor defines how close the duct and the pylons are and is used to calculate the Actual Launch Box Width. The Actual Launch Box Width must be smaller than the Maximum Allowable Launch Box Width. The relationship between the actual and allowable launch box width is a constraint available to the Particle Swarm Optimization method. The Solve for Pitch Trim check box specifies if trimmed solutions are to be calculated for the vehicle. Currently, the vehicle may only be trimmed in pitch, utilizing pitch-vane deflections. Selecting Assume Fixed Geometry for Trades prevents each geometric component from being regenerated every time there is a system wide update (which happens many times during simple operations). This feature will also prevent the updating of the automatic mass properties. 1-52 Figure 5-9: The Geometry Dialog Box Payload The Electronic Payload subsystem, which may be accessed from the Payload menu under OAV > Properties, is divided in four types of electrical components: Avionics, Communication, Electronic Payload, and General Electrical Device. The Electrical dialog, Figure 5-10, allows the selection of the type of electrical device to be installed. Click on the Electrical Device Type combo box to select one of the four types of electrical components. The list under the combo box, Device Name, displays a list of devices that can be installed on the OAV. The table below shows the properties of the component selected. The list on the right-hand side of the dialog box displays the electrical components currently installed on the OAV classified by electrical device type. The Add button will install the device currently selected in the Device Name list. Note that you can install the same component as many times as necessary. Any installed device 1-53 may be attached to a power circuit. By default, each item as it is installed is attached to one of the two default power circuits: Default Avionics or Default Propulsion. To chose the circuit to which an item is attached, select the installed item in the right hand list. Next, select the desired power circuit from the Attached to Circuit combo box in the lower left corner of the Electrical dialog. To remove an item from the aircraft, select the component you want to remove from the installed components list and click Remove. As with other dialog boxes, clicking Cancel will discard any changes and close the dialog box, clicking O K will accept any modifications and close the dialog box, and clicking Apply will accept any changes and keep the dialog box open. The list of components that are available to be installed is managed through the File > Edit Initial Data menu item and described in detail in Chapter 3. Figure 5-10: The Electrical Dialog Box Power Circuits AVID OAV provides the concept of multiple electrical circuits. Having more than two circuits allows the creation of an OAV that may use its propulsion battery as a power supply for avionics. Multiple batteries may also be used for different avionics circuits, each with multiple power conditioners with differing efficiencies. Being able to create and manipulate a number of circuits enhances the design capability of AVID OAV by 1-54 improving the ability to accurately account for electrical device requirements during concept development. The Power Circuits dialog shown in Figure 5-11 is accessed by selecting OAV > Properties > Payload > Power Circuits from the main menu. To create a new power circuit, enter a name for the circuit in the Enter New Circuit input box and press the Add button. The name of the new circuit appears in the list of existing circuits. Press the Apply or OK button to accept any new circuits you have entered. Apply will keep the Power Circuits dialog open while OK will close it. Now the new circuit is ready for use. You may add components to the circuit through the Propulsion and Power and Electrical dialog boxes. The two default circuits, Default Avionics and Default Propulsion, cannot be removed from the aircraft. However, any user-defined circuit may be removed. To remove a power circuit, select the circuit from the existing circuits list and press the Remove button. Press the Apply or OK button to accept the removal. Any components attached to the circuit that you delete will be reattached to one of the two default circuits depending on the type of the component. Remember that the Cancel button discards any changes you make to the aircraft’s power circuits. Apply accepts your changes and keeps the Power Circuits dialog open while OK accepts your changes and closes the dialog. Figure 5-11: The Power Circuits dialog 1-55 Performance The Performance dialog box (Figure 5-12) allows you to specify parameters that affect the performance of the aircraft. Clicking OAV > Properties > Performance accesses this dialog box. Figure 5-12: The Performance dialog The following is a list of the variables controlled by the Performance dialog box, with their default values and a brief description. Figure of Merit 0.8 The figure of merit of hovering rotor is equivalent to a propeller static thrust efficiency and is defined as the ratio between the ideal power required to hover and the actual power required to hover: where Pi is the induced (ideal) power . Note that this figure of merit corresponds to a free propeller. Duct Gain Factor 70 % The Duct Gain Factor is defined as the increase on performance when comparing a free propeller with a ducted one. 1-56 Duct Loss Factor 20 % The Duct Loss Factor is defined as the loss on performance due to friction and obstructions inside the duct. The obstructions include the stators and vanes, the engine, and the center pod or fuselage. The free propeller, the duct gain factor and the duct loss factor can be used to evaluate the overall, ducted, figure of merit of an OAV: Propeller Efficiency 60 % Propeller efficiency is defined as the percentage of brake horsepower (bhp) that is converted to usable thrust horsepower (thp) by the propeller. That is: Min. Allowable Disc Loading Max. Allowable Disc Loading 10 lb/ft2 30 lb/ft2 The disc loading is defined as the ratio between the rotor thrust and the rotor disc area. The range of allowed disc loadings is bounded by these two variables, which can be used as constraints during the optimization process. If these constraints are active, only OAVs inside the given range of disc loadings will be acceptable. If the actual disc loading is lower than the minimum allowable disc loading, then the “Min Disc Loading (lb/ft^2)” constraint on the Swarm Dialog Box will be “Violated” and highlighted in red. Conversely, if the actual disc loading is higher than the maximum allowable disc loading, then the “Max Disc Loading (lb/ft^2)” constraint on the Swarm Dialog Box will be “Violated” and highlighted in red. Note that these are not required physical limitations but user defined limitations. It is left to the user to decide their values. A disc loading too low may result in control power being lower than desired. A disc loading too high may surpass the strength of the material used on the propeller or fan. 1-57 System Energy Rate Factor 1.5 The System Energy Rate Factor is the system battery safety factor. This safety factor is used to determine the amount of system battery available. The default value of 1.5 implies that the system batteries are discharged 50% faster than their nominal rate. A value greater than 1.0 insures that extra battery capacity will be available at the end of the design mission. Structure Mass Fraction 0.33 This is defined as the minimum mass fraction of the OAV structure. The structure mass fraction is the structure weight divided by the total weight. Without such a lower limit, and, if allowed, the optimizer will try to make the structural weight zero. If the optimizer specifies a structural weight that results in a mass fraction less than the Structure Mass Fraction value, the Structural Weight constraint on the Swarm Dialog Box will be “Violated” and highlighted in red. Motor Energy Rate Factor 1 The Motor Energy Rate Factor is the propulsion battery safety factor. This safety factor is used to determine the amount of propulsion battery available. The default value of 1 implies that the propulsion batteries are discharged at their nominal rate. A value greater than 1 insures that extra battery capacity will be available at the end of the design mission. Fuel Flow Factor 1 The fuel flow factor is a safety factor that increases or reduces the engine specific fuel consumption (sfc). The default value of 1 assumes that the calculated sfc is correct. A value of 1.1 would increase the sfc used by a factor of 10%. Propulsion and Power The propulsion and power subsystem can be set through the Propulsion dialog. It is displayed by clicking OAV > Properties > Propulsion and Power. As shown in Figure 5-13, there are six tabs in this dialog box: Engine, Accessories, Battery, Propulsion Battery, Generator, and Power Accessories. The database of available Propulsion and Power components can be edited under the File > Edit Initial Data menu item that is explained in detail in Chapter 3. 1-58 Underneath the tabs there are three buttons: Apply, OK, and Cancel. The behavior of these buttons is the same as the buttons of the same name in other dialog boxes. Cancel discards any changes and closes the dialog box. OK accepts any changes, validates the OAV model and closes the dialog box. Apply is the same as OK but the dialog box will remain open. Figure 5-13: The Propulsion Dialog Box Engine The Engine tab allows the selection of the engine installed on the aircraft. When an engine is selected from the Select an Engine Model combo box its properties are displayed in the table underneath. Once an engine has been selected, the Add button will install the engine and its name will show up in the Engine(s) Installed on Current OAV list. Note that the list needs to be empty for the engine installation to be successful. The program is designed to analyze OAVs with one engine; therefore only one engine can be installed at a time. Attempting to install more than one engine will cause an error message to pop up. See Figure 5-14. Any installed engine may be attached to a power circuit. To chose the circuit to which an engine is attached, select the installed engine in the right hand list. Next, select the desired power circuit from the Attached to Circuit combo box in the lower left corner. 1-59 Figure 5-14: Error Message When Trying to Install More than One Engine Accessories The Accessories tab presents two tables with propulsion related components. The table on the top contains components that are typically installed on an OAV propelled by an internal combustion engine: a starter interface, a starter motor, fuel tank, spinner, and plumbing. The table on the bottom contains components that are only needed on an OAV propelled by an electric motor. Although engine accessories are listed in two separate tables, you can decide which of these components are installed, independently of the propulsion system. The heat sink, for instance, is listed in the Electrical Motor table but may be installed on IC engines or electrical motors. To install a component, change its quantity from zero to an integer of one or more. The weight of the component is calculated as a mass fraction of some base weight. With the exception of the Fuel Tank, the base weight of all the engine accessories is the weight of the internal combustion engine or the electrical motor. The base weight of the Fuel Tank is the total weight of the fuel: mission fuel plus reserves. The reserve fuel is considered to be 10% of the mission fuel, and is specified in the Swarm Based Optimization dialog. Battery The Battery tab allows the selection of the battery to be installed. When a battery is selected from the combo box its properties will be displayed in the table below the combo box. Install will install the selected battery. Installed batteries are listed on the right hand side list. To uninstall a battery select it from the Batteries Installed on Current OAV list and click Remove. Each installed battery may be attached to a power circuit. To attach a battery to a circuit, select the installed battery in the right hand list. Next, select the desired power circuit from the Attached to Circuit combo box in the lower left corner. The batteries available through this tab are also known as non-propulsion batteries. The name is used to denote the difference with propulsion batteries, which can be selected in the next tab. Non-propulsion batteries are used to power all the electrical devices installed on the vehicle. There are two types of non-propulsion batteries: rubber and fixed. A fixed battery has a known weight and power, while power per weight is the only data known for a rubber battery. The design variable named Rubber Battery Weight is what controls the weight of a rubber battery. The Swarm Optimization method, when 1-60 minimizing total weight, ensures that the lightest battery able to provide the required electrical power is used. Propulsion Battery The Propulsion Battery tab allows the selection of the propulsion battery. When a propulsion battery is selected from the combo box its properties will be displayed in the table below the combo box. Install will install the selected battery and add it to the Propulsion Batteries Installed on Current OAV list. To uninstall a battery select it from the Propulsion Batteries Installed on Current OAV list and click Remove. Note that an OAV may have only one propulsion battery installed at a time. Any installed propulsion battery may be attached to a power circuit. To choose the circuit to which a battery is attached, select the installed battery in the right hand list. Next, select the desired power circuit from the Attached to Circuit combo box in the lower left corner. The batteries available through this tab are also known as propulsion batteries. The name is used to denote the difference with non-propulsion batteries, which can be selected in the previous tab. Propulsion batteries are used to power an electrical motor installed on an OAV. Although there are two types of propulsion batteries, rubber and fixed, all the propulsion batteries available on the default initial data file (initialdata.oavxls) are rubber. The Weight design variable determines the weight of a rubber propulsion battery. When optimizing an OAV, this weight will be minimized while ensuring there is enough electricity to power the electrical motor during a given mission. Generator The Generator tab allows the installation of a generator component. The default initial data file (initialdata.oavxls) provides only a rubber generator. Additional generators can be made available through additional data files. The table under the combo box will display the properties of the generator selected. Install will install the selected generator and add it to the Generators Installed on Current OAV list. To uninstall a generator select it from the Generators Installed on Current OAV list and click Remove. Any installed generator may be attached to a power circuit. To choose the circuit to which a generator is attached, select the installed generator in the right hand list. Next, select the desired power circuit from the Attached to Circuit combo box in the lower left corner. Power Accessories The Power Accessories tab allows the installation of Power Conditioners and Power Converters. The combo box has a list of all the power accessories available. The properties of a selected Power Accessory are displayed in the table below the combo box. Install will install the power accessory selected. To uninstall a power accessory select it from the Power Accessories Installed on Current OAV list and click Remove. Note that power accessories can be fixed or rubber. Any installed accessory may be attached to a power circuit. To choose the circuit to which an accessory is attached, select the 1-61 installed accessory in the right hand list. Next, select the desired power circuit from the Attached to Circuit combo box in the lower left corner. 1-62 Weight and Balance CG Envelope A plot showing the static limits of the aircraft center-of-gravity can be displayed by selecting OAV > Properties > Weight and Balance > CG Envelope. Display Total Mass Properties The Aircraft Mass Properties dialog (see Figure 5-15) displays the calculated overall mass, center of mass, and moments of inertia of the OAV. The dialog may be displayed by clicking OAV > Properties > Weight and Balance > Display Total Mass Properties. You can specify your own values for these properties if you wish to do so. Check the Use User-Defined Values checkbox and you will be able to enter your values for the moments of inertia and the center of mass for the currently loaded aircraft. Figure 5-15: The Aircraft Mass Properties dialog 1-63 Edit Mass Properties The Mass Properties dialog box gives the user the ability to edit the values of the mass properties of every component in the OAV, specify whether or not the system should use gravity-based fuel tanks during analysis, and define some parameters of the fuel tank. The dialog box (see Figure 5-16) may be displayed by clicking OAV > Properties > Weight and Balance > Edit Mass Properties. Each component listed in the Aircraft Components table has fields for its category, name, mass (or density and thickness), moments and products of inertia, position, rotation, and center of gravity offset. The second table, Fuel in Gravity-Based Tanks, displays the category, owning component, weight, density, moments and products of inertia, position, rotation, and center of gravity offset for the fuel that is stored in the tanks. Fields that are editable are shown in yellow; fields that are read-only are shown in gray. If a field is read-only, its value is either predetermined or may be edited in another area of the program. A description of each column is given below. Figure 5-16: The Aircraft Component Mass Properties Dialog Box 1-64 Category The Category column specifies the subgroup of components to which the entry belongs. Some examples of category values would be: Air Frame, Propulsion, Payload, Design Variable, etc. Generally there is another area of the program for each of these categories. For instance, all entries listed with a Propulsion category were added to the OAV through the Propulsion dialog, and may be modified through that same dialog. Another example would be the Design Variables, which can be viewed and edited through the Swarm Optimization dialog. Fields in the Category column are read-only. Name This column displays the name of the component. Fields in the Name column are readonly. Weight This column displays the total mass of the component. For components that were selected from a list of available components, this value will be predetermined and readonly. To change the mass value in this case, the initial data file must be modified (Click File > Edit Initial Data). If the component was created by the user, such as an AirFrame component, then the weight can be modified. In the second table, Fuel in Gravity-Based Tanks, Weight displays the weight of the fuel in the tank. For multiple tanks, the amount of fuel placed in each tank is allocated automatically by the code and cannot be modified. The method used for allocating fuel will be described below. Thickness and Density These fields are currently not available, but will be functional in a future version of AVID OAV. They will be used to calculate the mass, center of gravity, and moments of inertia for geometry components. Ixx, Iyy, Izz, Ixy, Ixz, and Iyz These fields represent the moments and products of inertia. Ixx, Iyy, and Izz are moments of inertia respectively about the x, y, and z axis through the component’s center of mass. Ixy, Ixz, and Iyz are the products of inertia with respect to the component’s center of mass. These values can also be edited via the Mass Properties tab of the Geometry Component dialog. Xpos, Ypos, and Zpos These fields display the position of the component relative to the OAV’s origin. These values can also be edited via the Location tab of the Geometry Component dialog. 1-65 Xrot, Yrot, and Zrot These fields display the rotation of the component about the x, y, and z axes of the component. The order in which these rotations are applied to the component is as follows: first the x rotation, then the y rotation, and finally the z rotation. These values can also be edited via the Location tab of the Geometry Component dialog. X’CMOff, Y’CMOff, and Z’CMOff These fields represent the location (or offset) of the center of mass of the component relative to its own origin. These values can also be edited via the Mass Properties tab of the Geometry Component dialog. Owning Component This column appears in the Fuel in Gravity-Based Tanks table and displays the name of the component that is carrying the fuel. Above the second table, Fuel in Gravity-Based Tanks, is the checkbox Use GravityBased Fuel Analysis. When this is checked, the program uses a dynamic, gravity-based analysis method for calculating the mass properties of the fuel being carried by the vehicle. If left unchecked, the program uses a static method instead. Clicking the checkbox and then clicking the Apply button causes the Fuel design variable to be moved from the Aircraft Components table into the Fuel in Gravity-Based Tanks table and distributed between any components that have been designated as fuel tanks in the Edit Airframe Components dialog. The design variable Mission Fuel Weight controls how much fuel the vehicle will carry and can be set within the Swarm Optimization dialog. Gravity based fuel tanks provide a more detailed analysis of the contributions of fuel to the weight, center of gravity, and moments of inertia. When this option is checked, geometric fuel tank components created through the Edit Geometric Modeler Components dialog will simulate how liquid fuel would fill the tank defined by the parent component's geometry as a function of total fuel weight and vehicle orientation. As fuel is burned, and as the vehicle pitches down into the wind in high speed cruise, the center of gravity of the fuel will shift due to the nature of a liquid conforming to its container. Gravity based fuel tanks also allow for multiple fuel tanks to be used. There are filled using a "first in, first out" rule. The first fuel tank in the order of components in the Edit Geometric Modeler Components is considered the primary tank and is filled first; if any fuel is left over, it begins to fill the next tank. As fuel is used, it draws from the primary tank first and then subsequent reserve tanks. If this option is unchecked, the fuel is simulated by a single static component (unchanging center of gravity as fuel is burned). Its position, center of gravity, and mass properties can be edited through the Edit Mass Properties dialog. 1-66 It should also be noted that when this option is checked, the application speed might decrease due to the extra calculations needed to analyze the fuel. Underneath the table of values, there are three buttons: Apply, OK, and Cancel. The behavior of these buttons is the same as the buttons of the same name in other dialog boxes. Cancel discards any changes and closes the dialog box. OK accepts any changes, validates the OAV model and closes the dialog box. Apply is the same as OK but the dialog box will remain open. 1-67 Chapter 6 Optimizing the OAV AVID OAV currently incorporates two optimization methodologies: a conjugate gradient method and a particle swarm method. A short description of each method will be presented below and then a description of the common user interface. Conjugate Gradient-based Optimization Conjugate gradient description goes here… Particle Swarm Optimization Method Particle swarm optimization (PSO) is an evolutionary computation method with roots in psychology, artificial intelligence, engineering, and computer science. Its population members, called particles, are modeled after bird flocks, fish schools, and swarms of insects. Swarm may be defined as a population of interacting elements that is able to optimize a global objective through collaborative search of a space. PSO is similar to a genetic algorithm (GA) as both are population based and search for optima by updating generations. Particle swarm optimization is much simpler than GA because there are fewer parameters to adjust and it has no evolution operators. Each particle keeps track of its position in the design hyperspace along with the best value it and its family have obtained so far. The particle also keeps track of the global best value. Design “goodness” is determined by the fitness function. For every generation, or time step, each particle accelerates towards the best of its family and the global best. These accelerations are randomly weighted and result in a new velocity for the particle. At the end of the generation, the best of each particle’s family and the global best are selected by evaluating the fitness function. Note that these velocities and accelerations are rates of change in the design hyperspace but can be visualized as velocities and accelerations in three dimensions. In AVID OAV, each particle is a model of an OAV. The design variables are the characteristic coordinates defining each particle. These design variables are input through the Swarm Based Optimization dialog box described below. The creation of the swarm of particles, the population size, the evaluation of the best one for each particle's family and the evaluation of the global best are all done transparently. The values controlling the optimization are: population size maximum number of iterations convergence criterion 40 40 0.001 The PSO will stop when either of these conditions is satisfied: The maximum number of iterations (40) is reached. 1-68 At least half of the maximum number of iterations plus one (21) are executed and the difference between the global best of two consecutive generations is less than the convergence criterion. That is, the optimization converges. Swarm Based Optimization Dialog To open the Swarm Based Optimization dialog box, click OAV > Optimize > Optimization. As seen in Figure 6-1, this dialog box is divided into three sections. The top section contains a table with the Design Variables, the middle section includes a table with the Constraints, and the lower part allows the selection of the objective function and displays its value along with the values of the Objective Value, Penalty and Fitness function. Underneath these three sections there are located buttons to control the behavior of the dialog box. 1-69 Figure 6-1: Swarm Based Optimization dialog The Design Variables table displays the values of the selected design variables and whether they are locked. Click the Design Variables button to select which design variables to use in the optimization. The Select Design Variables dialog appears and lists the independent variables that define the OAV (Figure 6-2). Click the Name field to select or deselect a variable. The checkbox in the same row becomes checked or unchecked if a variable is selected or deselected. Press the OK button to use the selected variables. 1-70 Figure 6-2: Select Design Variables dialog A locked design variable will not change its value during optimization. Unlocked variables are allowed to take any value between the lower and upper bound. The Status column displays whether or not a design variable is locked. To lock or unlock a design variable click either the Name field or the Status field. The Constraints table displays the normalized value of the variables with respect to some constraint. To select which constraints to use in the optimization click the Constraints button. The Select Constraints dialog appears and lists the available constraints (Figure 6-3). To select or deselect a constraint click the Name field. The checkbox in the same row becomes checked or unchecked if a constraint is selected or deselected, respectively. Press the OK button to use the selected constraints. You can also define your own relational constraints. You can select two different variables and define the relation that must hold true between them. The relations are limited to “greater than” or “less than”. Therefore, you can define a custom relational constraint that must hold true for an optimization to be “satisfied”. 1-71 Figure 6-3: Select Constraints dialog The Status column allows for quick visualization of the validity of the current OAV as defined by the design variables. A constraint may still be excluded from use in the optimization by clicking the Name or Status fields. There are three possible values for status. If the variable takes a value beyond the constraint’s value, its normalized value will be positive and it will display a “Violated” status with a red background. If the normalized value is between 0 and -0.03, then the status will be “Active” and will have a yellow background. An active constraint means that we are very close to the constraint, within 3% of its value, and the yellow color is intended to act as a warning that further change in the same direction may result in a violated constraint. As long as the variable is inside the design space and its value is at least 3% away from the constraint its status will be “Satisfied” and will have a green background. The Penalty is zero when the constraint is satisfied or active and a large number when the constraint is violated, so that the PSO will try to avoid results with violated constraints. This large penalty is calculated with the following equation: penalty = 100 + 1000 * value2, where “value” is the normalized value of the second column of the table. 1-72 To select an objective for the fitness function, press the Objective Function button. The Select Objective Function dialog appears (Figure 6-4). Any dependent or independent trade study variable may be selected as the fitness function. (Only dependent variables will provide a reasonable optimization result.) To select one of the variables click the Name field. The checkbox in the same row becomes checked or unchecked if the variable is selected or deselected. Press the OK button to use the selected fitness function. Figure 6-4: Select Fitness Function dialog Selected objective functions may be maximized or minimized by selecting the appropriate radio button. The Objective Value is the current value of the selected objective function variable. The Penalty is the sum of all the penalties from the Constraints table. Fitness is the sum of the Objective Value plus the Penalty. The Cancel, OK, and Apply buttons behave as similar buttons do in other dialog boxes. Cancel will close the dialog box dismissing any changes, OK closes the dialog box saving any changes, and Apply saves changes while keeping the dialog box open. 1-73 The Optimize and Randomize buttons correspond to the two methods of running the optimization. Optimize uses the current OAV to seed the first population of the optimization. Randomize will run the optimization without seeding the first population with the current design and will instead use a random set of design variables. Running Swarm If the design space is too large then more than one run of swarm may be necessary. The number of unlocked variables and the difference between the lower and upper bounds determines the size of the design space. The larger the design space the more likely that the maximum number of generations (40) will be reached before a solution that satisfies the objective function is obtained. If this is the case, keep running the optimization until your objective is achieved. The number of constraints that are used will also affect converging on a solution since using more constraints makes finding a solution that meets all constraints more difficult. Some of the constraints are directly linked to the current mission. The Sufficient Fuel constraint, for example, will be violated if there is not enough fuel to complete the mission. Clicking Optimize or Randomize will run the Particle Swarm Optimization method. It is usually more expedient to run the swarm with seed because the result from previous runs will be used as inputs. Occasionally, a local rather that global optimum will be found that the optimizer may be unable to leave. If you run the optimizer several times and get the same result, you have reached an optimum point. To determine if it is a local or a global optimum, use the Randomize button. If a randomized swarm leads to a better solution, a local optimum has been reached. On the other hand, if a randomized swarm arrives at the same solution as the seeded swarm, the solution is a global optimum. A particle swarm optimization can be run indefinitely by checking the NonStop Optimization checkbox. If you run the optimization in non-stop mode, a mutant swarm member is added at the end of each generation to replace the least fit member of the population. The mutation prevents the solver from focusing exclusively around the fittest member, which might be a local ‘maximum’. 1-74 Chapter 7 Mission Analysis The vehicle performance requirements are evaluated using the AVID OAV Design Mission module. The user can specify a multi-leg design mission that sizes the vehicle for fuel weight, battery weight, overall size and power required. The fuel and energy consumed are calculated for each phase. The engine is also tested to determine if it can deliver the power required. If an actuator disc propeller is installed, this is based on figure of merit, but for a BVE propeller, the propeller map is used and maximum engine RPM also becomes a constraint. It is possible to include some “point performance” requirements by inserting the desired capability, such as a high, out-of-ground-effect hover, or a dash speed requirement, and setting time to a small value. If all the phases on a mission are “Accomplished”, the mission itself is “Accomplished”. If a phase fails, the mission fails and the program will display the reason for the failure. The violation, if any, of optimization constraints during the performance of a mission phase is also noted in the mission results. Mission Phases There are twelve types of phases available in AVID OAV: • OpenClimb • Climb (max rate) • Climb (max vertical rate) • Climb (true airspeed) • Climb (vertical) • Hover • Cruise • Loiter • Dash (distance) • Dash (time) • Cruise (max L/D) • Perch For each phase there are ten possible input variables. Each one corresponds to one of the columns on the Mission Dialog Box. The following is a list of these variables, along with a brief description and units used (if applicable): Name Any of the twelve phases available in the combo box may be selected. Initial Velocity The phase initial velocity, in feet per second (ft/s). Since the phases have constant speed (zero acceleration) the user interface will ensure that initial and final speeds are equal. 1-75 Final Velocity The phase final velocity, in feet per second (ft/s). Since most of the phases have constant speed (zero acceleration) the user interface will ensure that initial and final speeds are equal. Initial Altitude The phase initial altitude, in feet (ft). This variable depends on the type of phase and is explained in detail in the subsection below. Final Altitude The phase final altitude, in feet (ft). This variable depends on the type of phase and will be explained in detail in the subsection below. Time The amount of time the phase takes, in minutes (min). Horizontal Distance The horizontal distance, in feet (ft.) covered during the phase. Note that is may not be equal to the distance flown. For example, the climb phase may differ in distance flown and horizontal distance. Delta Weight An instantaneous increase or decrease of weight, and it is expressed in pounds (lb.). The weight is dropped at the beginning of the phase. Examples include dropping or recollecting sensors. A positive value represents a decrease in vehicle weight. Delta Power Consumed An instantaneous increase or decrease of electrical power consumed, and is expressed in watts (W). Examples include turning on or off some of the electrical payload. All the electrical devices installed on the OAV are assumed to be on during the entire mission; this variable allows turning off those electrical subsystems that are not being used. A positive value represents a decrease in power consumption. Comment The user may enter a brief description of the phase. Unless edited, it will contain the default comments associated with a phase type. You may find a detailed description of the phase useful for later identification. The text may be formatted using html tags. Since the information you enter here will be contained within an html cell on the mission results, you may want to limit the amount of information included here, however, the program will not impose any limitation on the length of the comment. If you have a large amount of information you may want to put it on an html page and then include a link to it. 1-76 Climb (max rate) Phase During this phase type, the aircraft is required to increase its altitude as fast as possible. The phase finds the velocity and horizontal distance traveled for maximum rate of climb, performed at maximum power available. Initial Altitude, Final Altitude, Delta Weight and Delta Power Consumed must be specified. The Velocities are given along the flight path, rather than along the ground. Climb (max vertical rate) Phase This phase determines the performance of the vehicle in a purely vertical climb. This phase is performed at maximum power available. Initial Altitude, Final Altitude, Delta Weight, and Delta Power Consumed must be specified. This phase can be used to determine the vehicle’s maximum vertical rate of climb at any given altitude. Climb (true airspeed) Phase During this phase type, the aircraft ascends with the velocity of the vehicle being constant. The vehicle will climb as fast as possible for a given true airspeed at maximum power. Initial Velocity, Initial Altitude, Final Altitude, Delta Weight, and Delta Power Consumed must be specified. . The Velocities are given along the flight path, rather than along the ground. Climb (vertical) Phase This phase measures the performance of an aircraft in a vertical climb. In this phase, the aircraft is required to ascend vertically at a fixed rate from one altitude to another. Initial Velocity, Initial Altitude, Final Altitude, Delta Weight, and Delta Power Consumed must be specified. Cruise Phase This phase measures the performance of an aircraft flying a given distance at a given velocity. During a Cruise phase, the aircraft travels a horizontal distance with no change in altitude. Power is adjusted to set thrust equal to drag. Initial Velocity, Initial Altitude, Horizontal Distance, Delta Weight and Delta Power Consumed must be specified. Cruise (max L/D) Phase This phase measures the performance of an aircraft flying a given distance such that the aircraft maintains its maximum lift to drag ratio by adjusting its velocity as weight changes. If the vehicle maintains its optimal lift to drag ratio, it flies at approximately the speed for best range. Power is adjusted to set thrust equal to drag. Initial Altitude, Horizontal Distance, Delta Weight, and Delta Power Consumed must be specified. Dash (distance) Phase This phase measures the performance of an aircraft flying a given horizontal distance at its maximum power condition. This phase will search for the maximum level speed. Initial Altitude, Horizontal Distance, Delta Weight, and Delta Power Consumed must be 1-77 specified. This phase can be used to determine the vehicle’s maximum level speed at any given altitude. Dash (time) Phase This phase measures the performance of an aircraft flying at its maximum power condition for a given amount of time. This phase will search for the maximum level speed. Initial Altitude, Time, Delta Weight and Delta Power Consumed must be specified. This phase can be used to determine the vehicle’s maximum level speed at any given altitude. Hover Phase This phase measures the performance of an aircraft in hover. Power is adjusted to hold thrust equal to weight. Initial Altitude, Time, Delta Weight and Delta Power Consumed must be specified. Loiter Phase This phase measures the ability of an aircraft to travel horizontally at a given velocity for a specific period of time. This is comparable to a Cruise, but time is specified rather than distance. Power is adjusted to set thrust equal to drag. Initial Velocity, Initial Altitude, Time, Delta Weight and Delta Power Consumed must be specified. OpenClimb Phase This phase allows the user to specify values for all mission phase parameters. OpenClimb serves as a general climb phase over a given time / distance. The user interface, given two of distance, time, or velocity, will calculate the third for you. If you then change one of the input values, the information will become inconsistent. The program will display an error message and highlight in red the background of the Horizontal Distance column. To correct the error, select the cell with the contents you want to delete then press the spacebar. You can enter the correct value or re-enter one of the other known values for the program to calculate the value of the blank cell. Note that depending on which values are supplied others are calculated. Initial Velocity and Final Velocity will remain equal, regardless of whether they are entered by the user or calculated automatically. The Velocities are given along the flight path, rather than along the ground. Perch Phase Perch is defined as “stationary on the ground”. For the perch phase, the inputs are Time (duration of perch), Delta Weight and Delta Power Consumed. The engine / motor is assumed to be off during a Perch phase, so no fuel or propulsive power is consumed. Mission Dialog Box There are two ways to access the Mission dialog. You can click OAV > Design Mission and the dialog box will pop up with the current mission. Alternatively, when you load a 1-78 mission file by clicking File > Load Mission, the Mission dialog will open and display the loaded mission. As seen in Figure 7-1 this dialog box contains a table of the phases that compose a given mission. Columns contain the variables defining each phase. Phases are displayed in the order they are flown. This order can be changed by clicking on the up and down arrows located to the left of the table. Figure 7-1: Mission dialog On the right of the table Add and Delete buttons allow the insertion or removal of phases. By default, a new phase is added to the end of the mission and is a Perch phase. The type of phase can be changed by clicking on the arrow next to its name and selecting the appropriate phase type from the pull down menu. The flight order of the new phase can be changed by using the arrows as described above. To delete a phase, select it by clicking anywhere on that row and then click Delete. Each time you click Compute Results the OAV will “fly” the mission described and a window called Results from Mission (Figure 7-2) pops up. The hyper-links in the top left hand corner will move the selected section into the display window. With Save, you can save the contents of this window as an html file or you can click Cancel to close this window. You can click Compute Results repeatedly allowing you to modify the mission and quickly see the results. Once you are satisfied with the results click Apply or OK. The only difference between the Apply and OK buttons is that the latter will close the dialog box while Apply will keep it open. You can also generate a graphical depiction of the current mission. On the Mission dialog press the Depiction button. A new window opens displaying a graphical representation of the mission. For an example, see Figure 7-3. 1-79 Figure 7-2: Results from Mission dialog 1-80 Figure 7-3: Depiction of a Mission Mission Results Data displayed in the Results from Mission dialog can be saved. This html formatted file can be viewed or printed with another program, including web browsers, spreadsheets, or word processors. This capability allows external calculation and/or creation of graphs and charts to help you visualize the results. This also enables the user to compare results from several different AVID OAV design sessions. The results include a summary of the mission, a description of the OAV, its inertia properties, and the results from the iSTAR spreadsheet for a vehicle with the same dimensions. 1-81 Chapter 8 Trade Studies Trade study is a process that provides a visualization of the effect of one or two variables on the performance of the aircraft being modeled. When you create a trade study in AVID OAV, you will need to specify the trade study variables and the objective variables to be traced during the study. While the trade study variables will take a range of input values, the variables being traced, or objectives, are considered the output of the study and their value depends on the current OAV. Understanding the relationships between different variables allows for a better understanding of the OAV design space. Trade Studies Dialog The Trade Studies dialog allows the selection of the variable or variables to be used for the trade study. Click OAV > Optimize > Trade Study to bring up the Trade Studies dialog box, Figure 8-1. You can also click on the Perform Trade Study button, , on the toolbar to bring up the dialog box. Figure 8-6: Trade Studies Dialog Box 1-82 The four text boxes at the top allow you to specify the variable to be studied, its minimum and maximum values, and the increment. The Increment is the value that will be added to the minimum value, as many times as necessary, until the maximum is reached. The objective variables will be evaluated for each value of the trade study variable from the minimum to the maximum. To select a new trade study variable, click the Change button next to the desired Trade Study Variables text box to bring up the Trade Study Variable Selector Dialog window. The Trade Study Variable Selector Dialog box, shown in Figure 8-2, is a long list of variables available for the trade study. Click on a variable's name to select it. Note that only one variable can be selected at a time; selecting a variable deselects any previously selected variable. Figure 8-2: Trade Study Variable Selector Dialog Box For each variable you must specify the minimum and maximum values and the increment. The Trade Studies dialog box will attempt to validate the data you enter. For instance, the maximum value must be greater than the minimum; if it is not and you click on the Perform Study button, an error dialog box (see Figure 8-3) will appear. 1-83 Figure 8-3: Invalid Study Error Dialog Box If the Enable Multi-Variable Trade Study box is checked, the second set of text boxes becomes active and you can select a second variable following the same procedure as the first variable. As with the fist trade study variable, you must specify the minimum and maximum values and the increment. Once you have specified the trade study variable or variables, you must select the variables whose values you want to trace. Click the Objectives button to view the Trade Study Variable Selector Dialog box. Within this dialog you can select multiple variables to be traced by clicking on their names. When you are satisfied with the variables to be traced and with the input variables for the trade study and their range of values, click the Perform Study button. The Trade Study Results from Trade Studies dialog will pop up after the program has performed the calculations. See Figure 8-4. Results can be saved in an html file and imported into a spreadsheet program such as Microsoft Excel. 1-84 Figure 8-4: Trade Studies results window A multi-variable trade study presents the user two plotting options: a carpet plot, or an xy plot. Only the x-y plot Plot option is available with results from a single variable trade study. Selecting Carpet Plot, the Define Carpet Plot dialog window is opened (figure 85). Through this dialog, the user can select the dependent variables from the list of trade study objective variables as well as specify the carpet plot title. Selecting Plot produces the carpet plot, an example of which is presented in figure 8-6. In this plot, the constraints as specified in the optimization dialog are plotted as the colored regions. The Constraint Name combo box can be used to display the color of each constraint. The white shaded area signifies combinations of design variables that specify aircraft that satisfy the mission requirements, the design space. Figure 8-5: Carpet Plot Definition Dialog Figure 8-6: Carpet Plot Showing Design Space in White The carpet plot Plot Settings option provides access to the dialog through which plot attributes may be specified (figure 8-7). The majority of the controls this dialog presents 1-85 are self-explanatory; descriptions of those requiring more explanation follow. The Carpet Plot Shift control allows the specification, in pixels, of the offset of the origin of successive 2-dimensional plots making up the carpet plot. The Curves tab provides the capability to specify the label location, line width, and RGB color for each line, independently, drawn in the carpet plot. Any point along the line may be specified as the label location using it cardinal. Several cardinal numbers have special meanings. An entry of 0 specifies the first point, -1 specifies in the middle of the line, -2 specifies at the last point, and an entry of -3 specifies beside the last point. Line width is specified in pixels. Figure 8-7: Carpet Plot Settings Dialog Two-dimensional plots of trade study results may be obtained by selecting the Plot option on the Trade Study Results window (see figure 8-4). Selecting Plot displays the Define Two-Dimensional Plot dialog shown in Figure 8-8. For a multi-variable trade study, one of the two trade study variables is selected as the independent variable while the other is set to a fixed value. The independent variable defaults to the trade study variable for a single variable trade study. The dependent plotting variable is selected from the list of trade study objective variables. Multiple dependent variables may be selected for plotting by highlighting the variable in the list on the left hand side and then selecting Add. Items may be removed from the plot by highlighting the variable in the Selected for Plot list and then selecting Remove. A representative two-dimensional plot is presented in figure 8-9. 1-86 Figure 8-8: Two-dimensional Plot Definition Dialog Figure 8-9: Representative Two-dimensional Trade Study Results Plot Besides the Perform Study button, the Trade Studies dialog box has Apply, OK, and Cancel buttons. Cancel will close the dialog box discarding any changes, Apply will save changes and leave the dialog box open, and OK will close the dialog box and save any changes. 1-87 Single Variable Trade Study The default in AVID OAV is to perform a single variable trade study. Select the design variable from the Trade Study Variable Selector Dialog box, choose minimum and maximum values, and define an increment. Select a set of objective variables whose value will be traced and click the Perform Study button. For each value of the trade study variable, the values of the objectives will be computed and displayed in the Trade Study Results from Trade Studies dialog box. The first column of the Trade Study Results from Trade Studies dialog box contains the input variable, the last column describes whether the current mission was successful or not. The message “Mission Failed” is displayed in the event of failure (shown in Figure 8-4 above). No message is printed if the mission is successful. 1-88 Multi-Variable Trade Study Checking the Enable Multi-Variable Trade Study box allows you to specify a second trade study variable. For each value of the second variable, the first variable will take all the values specified in its range and the values of the objectives will be computed. The steps for this trade study are the same as in the single variable trade study; the only difference is that a second variable along with its minimum and maximum values and its increment must be entered. The first two columns in the Trade Study Results from Trade Studies dialog box correspond to the two input variables, while the last column describes whether the current mission was successful or not. The message “Mission Failed” is displayed in the event of failure. No message is printed if the mission is successful. Optimization Trade Study The Optimize During Study option allows for the vehicle to be optimized at each combination of trade study variables. For this to be successful, several requirements are placed on the optimization. First, if the variables selected as Trade Study variables are be set as design variables in the optimization dialog window, these variables must be set with a “locked” status. The second requirement is that the variable selected as the objective function in the optimization dialog must also be set as an objective in the trade study. Be forewarned, this capability can result in significant run times. Consider that an optimization is being preformed for each vehicle originally defined by the trade study variables. For a single trade study variable consisting of N steps, this results in N optimizations. For a multi-variable design study, with the second variable having M steps, this equates to NxM optimizations. Saving and Loading Trade Studies Similar to OAVs and missions, trade studies can be saved to and loaded from a file. This allows you to save your work and perform the same trade study on a variety of OAVs flying different missions. Once a trade study has been created as described in this chapter and you have clicked Apply or OK in the Trade Studies dialog box you can save the trade study. First, select File > Project > Save Trade Study from the main menu. A Save dialog box will prompt you to give the trade study a name and save it. Give your trade study filename the extension *.ts so that it can be identified as a trade study data file. When you need to load a saved trade study, select File > Project > Load Trade Study. An Open dialog box appears and allows you to select the file with the desired trade study. 1-89 1-90 Chapter 9 Help About this User’s Guide This user guide is available from the Help menu. While the program is running click Help on the main toolbar, and then click Contents. A Help window will appear displaying the Table of Contents. From there you can choose which chapter you would like to read. Technical Support For support, please contact us via: Email support@avidllc.biz Telephone 540.961.0067 Fax 540.961.0068 Mail 1750 Kraft Drive, Suite 1400 Blacksburg, VA 24060 Contact information is available in the Help menu. On Linux or Windows click on the Help menu and then click About. On the MacOS click avid and then click About. 1-91 The Aircraft Editor The aircraft editor of AVID OAV provides a way to edit all of the trade study variables associated with the currently loaded OAV. To access the aircraft editor, select OAV > Edit Aircraft Parameters from the main menu and the Aircraft Editor dialog appears (Figure x-1). The aircraft editor organizes the editable information of an aircraft into a tree view. The tree view has two columns: Name and Value. Variable categories and variable names are listed in the Name column and the associated value in the Value column. Figure x-1: The Aircraft Editor dialog There are nine categories of variables in the tree view: AirFrame, Classic Design Variables, Electrical, Geometry, Mission, Performance, Propulsion, System Level, and Total Inertia. If you click the plus sign (+) or arrow (>) next to one of these categories, the tree view will expand to show you the available sub-categories or variables. For example, the AirFrame category, when expanded, displays a subcategory for each 1-92 airframe component of the aircraft. If you expand one of these subcategories, you can see the design variables for that airframe component. The current value of each design variable is shown in the Value column. To change the value of a design variable click the space where its value is displayed in the Value column, type in the desired value, and press the Enter or Return key. To accept your changes you can press either the Apply button or the OK button. Apply will accept the changes to the aircraft and keep the Aircraft Editor dialog open. OK will accept the changes and close the dialog. Clicking the Cancel button discards any changes you have made to the design variables of the aircraft and closes the Aircraft Editor dialog. 1-93 Chapter ?? Engine Modelling Engine Performance Response Surface Methodology Two different response surface models are used in AVID OAV, depending on whether the engine is a turbine or internal combustion (piston) engine. The basic performance of the modeled engine is represented by polynomial curve fits of two quantities, as a function of RPM fraction: 1. a. (piston) engines where HP † HPMax 2. a. = 100% throttle shaft horsepower at a specific RPM, = 100% throttle shaft horsepower at the limit or maximum RPM Referred specific fuel consumption (SFC): q ⋅ SFC ⋅ HP for turbine engines. d Referred 100% throttle horsepower: HP for both turbine engines and internal combustion HPMax b. † q ⋅ SFC ⋅ HPMax for internal combustion (piston) engines. d where q = ratio of the atmospheric absolute temperature and the sea-level standard absolute temperature d † = ratio of the atmospheric pressure and the sea-level standard pressure SFC = specific fuel consumption The horsepower lapse rate with altitude is modeled using the following equations: 1. 2. engines. † where HPMax @ SL † = 100% throttle shaft horsepower at the best/maximum RPM at sea-level HPMax = HPMax @ SL ⋅ s K for turbine engines. Ê 1- s ˆ HPMax = HPMax @ SL ⋅ Ás ˜ for internal combustion (piston) Ë K ¯ 1-94 s K = ratio of the atmospheric density and the sea-level standard density = thrust lapse coefficient By specifying the coefficients for the polynomial curve fits of the two quantities and the horsepower lapse rate coefficient K, the performance of the engine can be modeled within AVID OAV. The specific fuel consumption (SFC) is calculated based on the RPM that is required from the engine shaft, while the throttle setting is calculated from the power required from the shaft and the shaft horsepower available from the engine. The response surface model for an internal combustion engine (piston) only models the engine performance up to the limit or ‘stall’ RPM. The limit or ‘stall’ RPM is the RPM where the engine horsepower begins to decrease with increasing RPM. An illustration of this behavior is shown below in Figure ??-1. The performance in this region is generally undesirable, since this region has a higher SFC with lower available horsepower. In AVID OAV, the limit RPM can be specified, and the aircraft mission will fail if an RPM above that of the limit RPM is required. Figure ??-1: Representative Horsepower vs. RPM/ Max RPM curve showing the difference between Limit RPM and Maximum RPM. Creating an Engine Response Surface Model There are two different engine response surface models, depending on the type of engine. The following instructions describe the needed steps to create an engine response surface 1-95 model in Microsoft Excel. Any other spreadsheet program can also be used, as long as it is capable of specifying a polynomial curve fit or trend line for a set of data. Procedure for Turbine Engines If the data being used are at sea-level conditions, use the following instructions: 1. Input sea-level data of RPM, Horsepower at 100% throttle (HP) and SFC into Microsoft Excel RPM HP 2. Calculate columns for and . RPM Max HPMax 3. Calculate an additional column for SFC ⋅ HP RPM 4. Plot the SFC ⋅ HP vs. curve. RPM Max † † 5. Add a trend line (linear) to the curve. Make sure to select “Display equation on † chart” in the Options tab. †Record the linear and constant coefficients of the linear trend line – these 6. † coefficients will be for the SFC response surface model. They will be needed as input values in AVID OAV. HP RPM 7. Plot another curve for vs. . HPMax RPM Max 8. Add a trend line (linear) to the curve. Make sure to select “Display equation on chart” in the Options tab. 9. Record the linear and constant coefficients of the linear trend line – these † coefficients will be for † power response surface model. They will be needed as the input values in AVID OAV. 10. If additional engine data at altitude is available, the thrust lapse coefficient can be calculated. a. Find the value of s for the specific altitude from a standard atmosphere table. b. Calculate K (thrust lapse coefficient) using equation: Ê HP ˆ Max @ Altitude ˜ lnÁ Á HP ˜ Max @ SL ¯ Ë K= ln(s ) 11. If additional engine data at altitude is not available, use K = 0.7. If the data being used is at a specific altitude condition, use the following instructions: † 1. Input data of RPM, Horsepower at 100% throttle (HP) and SFC into Microsoft Excel RPM HP 2. Calculate columns for and . RPM Max HPMax 3. Find the values of d (Pressure ratio), q (temperature ratio) and s (density ratio) for the altitude the data is for from a standard atmosphere table. q † 4. Calculate an † additional column for Normalized SFC = SFC ⋅ HP ⋅ d † 1-96 RPM curve. RPM Max 6. Add a trend line (linear) to the curve. Make sure to select “Display equation on chart” in the Options tab. 7. Record the linear and constant coefficients of the linear trend line – these coefficients will be† the SFC response surface model. They will be needed as for input values in AVID OAV. HP RPM 8. Plot another curve for vs. . HPMax RPM Max 9. Add a trend line (linear) to the curve. Make sure to select “Display equation on chart” in the Options tab. 10. Record the linear and constant coefficients of the linear trend line – these † coefficients will be for † power response surface model. They will be needed as the input values in AVID OAV. 11. If additional engine data at another altitude is available, the thrust lapse coefficient can be calculated. a. Find the value of s at both altitudes from a standard atmosphere table. b. Calculate K (thrust lapse coefficient) using equation: Ê HP ˆ lnÁ Max @ Altitude 1 ˜ Á HP ˜ Ë Max @ Altitude 2 ¯ K= . Ês ˆ Altitude 1 ˜ lnÁ Ás ˜ Altitude 2 ¯ Ë 12. If additional engine data at another altitude is not available, use K = 0.7. 5. Plot the Normalized SFC vs. † Procedure for Internal Combustion (Piston) Engines If the data being used are at sea-level conditions, use the following instructions: 1. Input sea-level data of RPM, Horsepower at 100% throttle (HP) and SFC into Microsoft Excel RPM HP 2. Calculate columns for and (up to the limit RPM – the RPM RPM Max HPMax above which the maximum shaft HP decreases) 3. Calculate an additional column for Normalized SFC = SFC ⋅ HPMax RPM 4. Plot Normalized SFC vs. † curve † RPM Max 5. Add a trend line (2nd order polynomial) to the curve. Make sure to select “Display † equation on chart” in the Options tab. 6. Record the quadratic, linear and constant coefficients of the 2nd order polynomial † trend line – these coefficients will be for the SFC response surface model. They will be needed as input values in AVID OAV. HP RPM 7. Plot another curve for vs. . HPMax RPM Max † † 1-97 8. Add a trend line (2nd order polynomial) to the curve. Make sure to select “Display equation on chart” in the Options tab. 9. Record the quadratic, linear and constant coefficients of the 2nd order polynomial trend line – these coefficients will be for the power response surface model. They will be needed as input values in AVID OAV. 12. If additional engine data at altitude is available, the thrust lapse coefficient can be calculated. a. Find the value of s for the specific altitude from a standard atmosphere table. b. Calculate K (thrust lapse coefficient) using equation: 1- s K= HP s - Max @ Altitude HPMax @ SL 13. If additional engine data at altitude is not available, use K = 7.55. If the data being used is at a specific altitude condition, use the following instructions: † 1. Input sea-level data of RPM, Horsepower at 100% throttle (HP) and SFC into Microsoft Excel RPM HP 2. Calculate columns for and . RPM Max HPMax 3. Find the values of d (Pressure ratio), q (temperature ratio) and s (density ratio) for the altitude the data is for from a standard atmosphere table. q † 4. Calculate an † additional column for Normalized SFC = SFC ⋅ HPMax ⋅ d RPM 5. Plot the Normalized SFC vs. curve. RPM Max 6. Add a trend line (2nd order polynomial) to the curve. Make sure to select “Display † equation on chart” in the Options tab. 7. Record the quadratic, linear and constant coefficients of the 2nd order polynomial † trend line – these coefficients will be for the SFC response surface model. They will be needed as input values in AVID OAV. HP RPM 8. Plot another curve for vs. . HPMax RPM Max 9. Add a trend line (2nd order polynomial) to the curve. Make sure to select “Display equation on chart” in the Options tab. 10. Record the quadratic, linear and constant coefficients of the 2nd order polynomial † † trend line – these coefficients will be for the power response surface model. They will be needed as input values in AVID OAV. 13. If additional engine data at another altitude is available, the thrust lapse coefficient can be calculated. a. Find the value of s at both altitudes from a standard atmosphere table. 1-98 b. Calculate K (thrust lapse coefficient) using equation: Ê HP ˆ Á Max @ Altitude 1 ˜ ⋅(1- s Altitude 2 ) - (1- s Altitude 1 ) Á HP ˜ Ë Max @ Altitude 2 ¯ K= . Ê HP ˆ Á Max @ Altitude 1 ˜ ⋅ s Altitude 2 - s Altitude 1 Á HP ˜ Ë Max @ Altitude 2 ¯ 14. If additional engine data at another altitude is not available, use K = 7.55. † 1-99 1-100