Note: It is important to follow the restrictions on software copying. Codes purchased or obtained for free, typically from NASA, include restrictions on the use and further dissemination. Violation of these provisions could result in loss of access to codes in the future. Aircraft design is actually a rather small community. The long term professional consequences of not honoring software usage restrictions could be very severe.
1. The Approach Taken at VPI. Analysis codes for aircraft design have been assembled on the design lab IBM and Macintosh computers. The primary CAD effort uses either ACSYNT or CADAM, which both run on the IBM system. The students also have CADKEY available on their PCs. This setup provides the basic computing environment. A series of five manuals have been assembled covering 1) Aircraft Sizing and Performance, 2) Aerodynamics, 3) Stability and Control/Handling Qualities, 4) Propulsion, and 5) Structures. The effort to support codes and create adequate documentation is significant.
2. Public Domain Codes: It's not clear what's available as public domain anymore. However, we can make three simple codes available. These are either original, total rewrites by the author, or for which the non-copyrighted listings can be identified in unlimited distribution reports. Each code should run on any PC. FRICTION: estimates friction and form drag using the van Driest II turbulent skin friction formula and the 1976 standard atmosphere. LIDRAG: computes the span efficiency, "e" for a single planar surface. DESCAM provides the airfoil camber required to obtain a specified chord load for two dimensional incompressible airfoils, using Lan's Quasi Vortex Lattice method formulation. Each code is essentially a FORTRAN implementation of a method originally developed to run on a programmable calculator. We'll make three more codes available with the next issue of the newsletter.
For propulsion, the AIAA codes ONX/OFFX can provide some valuable help. The reference is by Jack D. Mattingly, On-Design and Off-Design Cycle Analysis Computer Programs, AIAA, New York, 1987. The book's good, and the book and codes are relatively inexpensive, although not actually public domain. Rumor has it that a second version has been developed by Mattingly, who is now at the University of Washington.
Recently a new propulsion design tool has been made available by the AIAA in conjunction with Rolls Royce for use in AIAA design competitions (distribution restrictions use for other purposes). The program, ENGINE MAKER, is intended to synthesize unmixed and mixed turbofan engines. It is a design point program, although it is possible to do some limited off design calculations. The code has a very nice graphical interface. It requires an IBM compatible PC running Microsoft Windows 3.x. A minimum of a 386 processor with a math coprocessor is recommended. To obtain a copy, contact Pat Gouhin, AIAA Student Programs Director, 370 L'Enfant Promenade, SW, Washington, DC 20024-2518, (202) 646-2518.
The Smetana Codes: Professor Smetana of NC State is willing to make his performance and stability and control codes available. The reference is: Frederick O. Smetana, Computer Assisted Analysis of Aircraft Performance Stability and Control, McGraw-Hill, New York, 1984. They run on IBM and Macintosh computers. Buy the book and decide if they fulfill your needs. They were developed specifically for GA aircraft, but are useful for other aircraft also.
NASA Codes: NASA has developed numerous aerodynamics codes that are widely available, and useful for design. These codes are officially available only through COSMIC. Members of the USRA Advanced Design program can get them for free. The most useful codes include the so-called "Lamar Vortex Lattice" and the "Harris Wavedrag" programs.
Air Force contribution: Digital DATCOM can be used to help find stability derivatives. It requires a VAX computer. The expertise level seems to stretch the ability of students, although it always seemed to work in industrial applications. Some supplementary notes were developed to help students.
Spreadsheet stability and control evaluation worksheets and a subsonic vortex lattice method code, JKayVLM, oriented toward stability and control derivative estimation is available from the author. This program was the result of a Master's Thesis by Jacob Kay. It can help students assess their designs for adequate stability and control characteristics. This program is available by writing to W.H. Mason.
Chuck Eastlake Codes. Prof. Eastlake has written several useful programs. LITECOST calculates the purchase cost and LITEOPS calculates the the operation cost of light aircraft. EXECCOST calculates the purchase cost and EXECOPS calculates the operation cost of executive aircraft. These programs have been used for several years by Prof. Eastlake, and contain adjustments to previously published algorithms to include his own experience.
Prof. Eastlake has also written some aircraft design programs to use in high school outreach programs. These programs give the weight and size of light and executive jet type aircraft as a function of a number of basic parameters. Both these programs and the cost programs are written in BASIC. Although available in IBM format, I converted them to run in QuickBASIC on the Macintosh quite easily.
The programs are available from Prof. Chuck Eastlake, Aerospace Engineering Department, Embry-Riddle Aeronautical University, 600 S. Clyde Morris Blvd., Daytona Beach, FL 32114-3900, (904) 226-6000, fax: (904) 226-6459.
AAA The AAA (Advanced Aircraft Analysis) code is a computerized version of Roskam's eight-volume text: Airplane Design, Parts I-VIII, featuring a user-friendly interface. The code currently operates on a number of workstations. The basic single workstation license is $3,000. A variety of license and support arrangements are available, with a large discount available on node licenses for educational institutions. The code is available from Design, Analysis and Research Corp, 120 East Ninth (2nd Floor West), Lawrence, Kansas, 66044, 913-832-0434.
Desktop Aeronautics Codes These are the codes by Ilan Kroo. Currently they run on Macintosh computers, but some are being ported to IBM. Desktop Aeronautics, P.O. Box 9937, Stanford, CA 94305, (415) 424-8588. Programs currently available include:
LinAir 1.4 - Multiple Lifting Surface Analysis Program ($200), LinAir Pro ($950). These codes treat complete configurations in subsonic flow, using a discrete Weissinger method. They include profile drag integration and Trefftz-plane induced drag calculation. They handle wing canard, aft tail, and winglet configurations. The Pro version includes asymmetric aircraft or sideslip, roll, pitch, and yaw rates, and nearfield drag calculations. PANDA: Program for Analysis and Design of Airfoils ($175). Subsonic, including compressibility effects via Karman-Tsien rule. Includes an integral boundary layer calculation for laminar and turbulent flow. A design option permits interactive change of airfoil geometry and display of the new pressure distribution.
Wing Design ($50), for quick computation and plotting of lift and Cl distributions on swept, tapered, twisted wings. Wing geometry changes effects on lift, drag, moment, and load distribution are found rapidly. SAND-Simulation of Aircraft Nonlinear Dynamics($200). Six degree of freedom time history computation. Interactive specification of control deflections, time and position dependent wind, and built in plotting are included. User supplied subroutines for computation of nonlinear aerodynamics and/or control laws can be included (requires Absoft FORTRAN). Linear dynamics analysis displays root-locus plots.
Aircraft Design Workshop ($295). Developed as an interactive museum exhibit, using a simple expert system to help the user meet field length, climb, range, and thrust constraints. University site licenses are available.
BASIC Aircraft Performance, A series of computer programs for the IBM PC that model the full size programs used in industry reasonably well. The reference is by Sidney A. Powers, BASIC Aircraft Performance Analysis, KERN International, Inc., 575 Washington Street, Pembroke, MA 02359, (617) 826-0095. The source code is provided, and a version that runs in QuickBASIC on a Macintosh is also available at VPI.
RDS Aircraft Design Software. Student Version: This is a software package put together by Dan Raymer, and implements the approach described in his book. It is published by the AIAA and runs on IBM computers. It has a rather restrictive site license. However, it is relatively inexpensive and includes both a CAD package and analysis modules. Professional Version: This is a much more comprehensive and expensive version being sold by Raymer. It appears to be quite capable, but I have not seen it.
Piano. This is complete aircraft design program for the Macintosh II computer from Great Britain. Essentially, it does everything that is needed in conceptual design environment. This includes weight and mass analysis, geometric and wetted area calculations, aerodynamic performance estimates. It then computes a complete performance evaluation and can also be used in an optimization mode. It is oriented toward FAR Part 25 commercial aircraft. Single Copy Academic User License: 1195 U.K. £ Sterling in 1990. This program is distributed by Lissys, 5 Winterburn Way, Loughborough LE 11 OEW, United Kingdom, Phone: 0509 235620, FAX 0509 236953. Dr. S. Simos is the director, and has published numerous papers on aircraft design.
Madsen Aircraft Design Program (M.A.D.) Version: 2.0.1 by Ned Madsen. From the shareware description: This Macintosh program was written to aid the aircraft designer with the conceptual design phase using the Mac user interface. The interactive nature of the program is ideal to quickly modify and reanalyze the design. For example, increasing the wing span has many effects on the aerodynamic characteristics of the aircraft. The program evaluates changes easily. It does not have any fancy graphic capabilities, it is intended to be a number cruncher.
The design should first be sketched with approximate dimensions for easy input to the program. There are over 100 inputs. An input list is available under the FILE menu. The inputs are self explanatory. The program evaluates the design in the areas of weight and balance, lift and drag, stability, controllability, and performance. Many of the outputs are simple. Others require a knowledge of some aircraft design parameters. All of the outputs are explained in the User's Guide.
The M.A.D. 2.0 program is shareware, and costs $25. With this fee you get a copy of the program without the shareware screen, the User's Guide and future upgrades. The User's guide contains a comprehensive overview of the execution of the program, all of the equations used, and a detailed explanation of the inputs and outputs from the program. The outputs are also shown in graphical form to further assist the designer in evaluating the design. The code is available from Ned Madsen, 44616 Foxboro Court, Lancaster, CA 93535 or: America on Line E-Mail to: NedM123456
Note: I have used this program, and am waiting for the user's manual. It is oriented toward general aviation aircraft, and contains an excellent database of airfoils and engines for GA aircraft. It appears to be well worth the shareware fee.
COMPUTER AIRCRAFT DESIGNER. This is a design program written by RC modelers, This program is for IBM and compatibles, and is oriented toward RC models. It prints out plans on dot matrix printers, and is CAD oriented. Interestingly, it handles multi-fuselage, asymmetric and canard aircraft. It also evaluates the design for stability characteristics. The program costs $79.95, and is available from COMPUTER AIRCRAFT DESIGNS, P.O. Box 1110, Sterling, VA 20167, Phone: (703) 444-0308. email: cad@digex.com.
Note: I have not used this program.
Airplane Design by Donald R. Crawford. This is a book collecting a series of articles that appeared in Kitplanes, together with BASIC listings. It contains a variety of useful design codes. This book is for sale by the book sellers listed below. A disk of BASIC codes is available for IBM computers. Crawford Aviation, P.O. Box 1262-S, Torrance, CA 90505, (213) 375-9227. A performance book and disk are also available. Some of my students have been happy with this program. The book is about $25, and and the disk is about $40. However, it would be informative to type in the listings and examine exactly what is going on. Naturally this book is also oriented toward GA aircraft.
FLOFT/WLOFT. These are new three-dimensional DOS-based IBM PC Programs. They are CAD programs for developing fuselage(FLOFT) and wing(WLOFT) lines. They compute all geometric properties, and can provide geometry for arbitrary section cuts. They can generate surface meshes, and the models can be ported to AutoCAD. The method of conic sections is used in FLOFT. WLOFT is designed to work with airfoil definitions, and prints wing sections in a variety of forms. The two programs are $350, and academic discounts are available reducing the price to $245. They are for sale by Peter Garrison, 1613 Altivo Way, Los Angeles, CA 90026, (213) 665-1397, fax: (213) 953-8378.
Note: A recent note on the sci.aeronautics newsgroup provided some useful comments related to these programs. Mike Logan, NASA Langley (mlogan@avd47.larc.nasa.gov) relayed the results of a study made at another school. In that study, Mike's Quickmod code was judged to be better than FLOFT/WLOFT for developing aircraft geometry. AutoCAD was judged second, followed by Raymer's RDS code, DesignCAD and finally FLOFT/WLOFT. For an individual doing a particular job, each of these methods should be evaluated to decide which one is most appropriate.
4. The ACSYNT Institute
ACSYNT is PHIGS based and runs on all workstations. It is an extremely sophisticated aircraft configuration sizing and optimization code, which can also be used for mission analysis. The code is available to members of the ACSYNT Institute, which is located at the CAD Lab of Virginia Tech, and is directed by its government, industry, and university members. The official NASA contact is Paul Gelhausen, NASA Ames Research Center, Mail Stop 237-11, Moffett Field, CA 94305, (415) 604-5701, and Professor Arvid Myklebust, Mechanical Engineering Department, Virginia Tech, Blacksburg, VA 24061, (703) 231-7195.
Fully interactive, ACSYNT allows the user to create geometry parametrically (using design parameters such as wing area and taper ratio) instead of specifying 3-D points and curves. The CAD capability now includes a "spreadsheet" format for entering data for the analysis modules. The spreadsheet has on-line help for all the analysis variables, formula capabilities, and can be custom-tailored for individual user's needs.
5. ESDU
Many of the ESDU data sheets have been computerized. Every imaginable engineering area of aerospace is covered by ESDU. A British company, ESDU stands for Engineering and Scientific Data Unit, and is a descendent of the old Royal Aeronautical Data Sheets. Although not cheap, the support is be very good. In the US, ESDU is located at PO Box 1633, Manassas, VA, 22110, (703) 631-4187.
6. Design Software Review
A review of aircraft design software, together with a design implementation in MathCAD has been presented recently by Anthony M. Agone, "Using MathCAD in Aircraft Design Instructions," ASEE, 1993, Session 0011. This is a good review of several of the codes listed above.
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direct comments and suggestions to W.H. Mason, mason@apollo.aoe.vt.edu