Frequently-Asked Questions (FAQ)


Aircraft System Identification: Theory and Practice

by Vladislav Klein and Eugene A. Morelli



What does the SIDPAC acronym stand for? 


System IDentification Programs for AirCraft



What programming language is SIDPAC written in?


SIDPAC is written in standard MATLAB.  SIDPAC version 2.0 was validated on MATLAB version 7.1, R14, service pack 3.  However, much of SIDPAC was written on earlier versions of MATLAB, so SIDPAC should work fine on earlier or later versions of MATLAB. 



Who wrote SIDPAC? 


Dr. Eugene Morelli wrote and tested all the programs in SIDPAC over a period of years, beginning in 1991.  Some of the algorithms implemented in SIDPAC were developed by Dr. Morelli, but others are from the literature or are adapted from legacy FORTRAN programs developed and used at NASA over the years.  SIDPAC is the toolbox used routinely at NASA Langley for aircraft system identification.  SIDPAC is a dynamic collection of programs, in that Dr. Morelli continually updates, expands, and improves the programs in SIDPAC. 



How do I install SIDPAC on my computer?


SIDPAC is a collection of MATLAB M-files, so there is no installation to be done, other than the standard installation of MATLAB.  The SIDPAC M-files are extracted from a .zip file available by download when you purchase the textbook: Aircraft System Identification Theory and Practice, by V. Klein and E.A. Morelli. 



Do I need any special MATLAB toolboxes to run SIDPAC? 


No, SIDPAC requires only standard MATLAB. 



How can I obtain the SIDPAC software?


The SIDPAC software is distributed only with the textbook Aircraft System Identification Theory and Practice , by V. Klein and E.A. Morelli.  To get SIDPAC, you must purchase the book.  Information on purchasing the book can be found here. 



I bought the book, but there is no CD.  How do I get the SIDPAC software?


Instructions for downloading the SIDPAC software are in the Supporting Materials section near the back of the book. 



How do you run SIDPAC? 


Because SIDPAC is a collection of programs (implemented as MATLAB M-files), there is no single command that can be used to run SIDPAC.  Any program in SIDPAC can be run from the MATLAB command line, and each program has clear instructions and descriptions in its header.  Any file header can be displayed by typing help filename at the MATLAB command prompt, where filename is the name of the SIDPAC M-file, without the .m file extension.  Assuming the SIDPAC files are in the current MATLAB path in a directory named sidpac, you can type help sidpac to get a list and description of all the functions in SIDPAC.  Alternatively, you can invoke the SIDPAC graphical user interface (GUI) by typing sid at the MATLAB prompt.  The GUI makes plotting and analysis easier, and helps you invoke SIDPAC programs by automatically setting up inputs to the programs according to your point-and-click mouse inputs.  More details are available in Chapter 12 of the textbook Aircraft System Identification Theory and Practice, by V. Klein and E.A. Morelli. 



What is the best way to learn to use SIDPAC?


SIDPAC includes many demonstration scripts that show how to use the SIDPAC programs, along with sample results, using real flight data and wind-tunnel data.  The directory called Demos in the SIDPAC folder contains the demonstration scripts.  These demonstration scripts all have names that include the characters _demo.m.  The other characters in the name refer to the main SIDPAC program that is being demonstrated.  For example, oe_demo.m demonstrates the use of the output-error program oe.m.  The code inside oe_demo.m gives a detailed, realistic example of how to use the oe.m program.  In addition, the folder called Text_Examples contains a script called sidpac_text_examples.m.  This script allows the reader to re-create the results from examples in the textbook.  Studying the code inside the _demo.m files and sidpac_text_examples.m is a good way to learn how to use SIDPAC programs. 



Who uses SIDPAC?


A list of organizations that use SIDPAC is available here. 



Is training available for SIDPAC?


Yes, there is a professional development short course taught by Dr. Eugene Morelli, author of SIDPAC and co-author of the textbook Aircraft System Identification Theory and Practice.  Contact Dr. Eugene Morelli (, (757) 864-4078) for more information.