FDA – CAD
FLIGHT DYNAMICS ANALYSIS – CONTROL AUGMENTATION DESIGN
Introduction
FDA-CAD is an interactive computer program designed to support the post graduate
lecture courses Flight Dynamics Principles and Flying Qualities and Flight Control taught
by the author in the School of Engineering at Cranfield University. The program has been
developed in a piecemeal fashion by the author’s students as MSc thesis projects over a
period of about 15 years. The program is written in MATLAB and provides an easy to use
tool for linear flight dynamics analysis, command and stability augmentation system design
and handling qualities assessment. Version 3.01 of FDA-CAD is a slimmed down version
of the program, tailored to support the third edition of Flight Dynamics Principles[6], and is
offered as a free download from the publishers web site to purchasers of the book.
History
First attempts at developing a set of computer software tools to support the courses in
flight dynamics were made by Cruciani[1], Sverkmo[2] and Oakley[3]. These were made at a
time before MATLAB had become fully established locally as the software of choice for
studies in flight dynamics. However, these early studies provided some ground rules for
the design of relevant computational algorithms and set out the ideas for subsequent
studies.
The first study to embrace fully the computational facilities of MATLAB was made by
Spathopoulos[4], and his work established the algorithms required for the routine solution
and analysis of the linear equations of motion of an aircraft. This suite of software tools
became the foundation for the subsequent development of FDA-CAD.
Some years later, the continuing development of MATLAB and the introduction of
Graphical User Interface (GUI) tools opened up the possibility for an altogether more
ambitious attempt at writing a software tool for flight dynamics analysis. Accordingly,
Rees[4] produced the first version of FDA-CAD. This was an exceptionally complex task
and in the limited time available for the project, he established a framework for, and the
basic functionality of the program, building on the work of Spathopoulos [3].
From a satisfactory beginning, it was soon recognised that the first version of FDA-CAD
had a few minor errors and imperfections, and that its scope could be expanded. A major
revision and further development of Rees’ program [5] was undertaken by Siliverdis[6], to
result in version two of FDA-CAD. All of the known errors were corrected (and replaced
with a few different errors!) and the functionality was expanded to include additional tools
for stability augmentation design and analysis, and handing qualities assessment. Again,
project time constraints prevented a complete development of the more advanced
additions.
FDA-CAD Version 1.0
Written by Shane Rees[5]. The user is presented with two GUI screens, an opening screen
on which the basic analysis requirement can be selected – selection then opens the
second screen configured either for longitudinal analysis or lateral-directional analysis.
Access to stability augmentation design functions and some limited handling qualities
assessment is also made from either of these two screens. Interactive analysis then
involves opening a variety of figure windows to show the results of the computations
selected. Tools are included for entering and saving aircraft data, outputting the results of
the computations and facilities for recording a variety of graphical plots. The program is
personalised by Rees, who at the time was member of the Royal Australian Air Force, and
the opening screen includes attractive aircraft imagery promoting the RAAF. Also, a
distinctive feature of the GUI screens is the prominent display of a large button sporting
the obsolete Cranfield College of Aeronautics logo.
FDA-CAD Version 2.0
Written by Konstantinos Siliverdis[6]. This version of FDA-CAD builds on the first version
developed by Rees[4]. The basic functionality and structure remains unchanged and most
of the computational routines are retained with only minor changes. The general
appearance of the program is therefore very similar. The main structural difference
concerns the way in which the analysis screens are presented. The user is now presented
with an opening screen, transferring to a basic aircraft analysis screen, transferring to a
stability augmentation screen, transferring to a handling qualities assessment screen.
Each screen has been developed as a separate GUI, which simplifies the callback
structure to a certain extent. Unfortunately, the handling qualities screen, which includes
considerable complexity of choice has not been developed sufficient for reliable general
utilisation. A central feature of the design is that the user can step back and forth between
screens during the process of analysis or design. Again, the program has been
personalised to reflect Siliverdis’ affiliation, and in this instance the opening screen depicts
attractive images of the F-16 aircraft as operated by the Hellenic Air Force.
FDA-CAD Version 3.0
Developed by the author by significantly editing version two to match the computational
requirement of the book Flight Dynamics Principles[7]. The main changes include removal
of the handling qualities assessment screen and supporting functionality, replacement of
the personalised opening screen, correction of computational errors, correction of
functional ‘bugs’ and general refinement of the GUI screens. The general appearance of
the screens remains as originally designed by Rees[4] as these have been shown to be
more than adequate for the task.
System Requirements
FDA-CAD v3.01 was developed on a laptop computer having the following specification:



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Intel Pentium III processor.
512 MB RAM.
Screen resolution 1024×768 pixels
Screen physical size 12×9 inches (305×229mm)
MS Windows XP
 MATLAB v7.0.4 with Service Pack 2
 MATLAB Control Systems Toolbox v6.2
Disclaimer
The original development of the software was intended as an exercise for students to
demonstrate their ability to utilise computational tools for application to flight dynamics
analysis problems. The contributing students were free to make and justify their own
design choices during the course of the software writing process. It has not been
developed to professional standards and it is offered on the understanding that its
performance, accuracy, suitability and reliability are not guaranteed. The user is therefore
advised to confirm the plausibility of results obtained with FDA-CAD by standard flight
dynamics analysis methods. FDA-CAD is sufficient to demonstrate the computational
solution of many of the examples described in Flight Dynamics Principles[6], but it is the
responsibility of the user to establish the suitability of the software for other applications.
Copyright
Ownership of the copyright of all theses supporting the development of FDA-CAD resides
with Cranfield University, and copies may be obtained on application to the University
Library.
The opening screen image is reproduced from the cover of Flight Dynamics Principles[6],
the copyright is owned by BAE Systems who kindly provided the image and permission to
use it for this publishing project.
Bibliography
1.
Cruciani, H. The development of a general purpose flight dynamics analysis
computer software package. MSc thesis 1990, Cranfield University.
2.
Sverkmo, M. The development of a flight dynamics analysis software package. 1992
3.
Oakley, P.C. The development of a flight dynamics analysis computer software
package. MSc thesis 1993, Cranfield University.
4.
Spathopoulos, V.M. The development of flight dynamics analysis macros for
MATLAB. MSc thesis 1996, Cranfield University.
5.
Rees, S. Development of MATLAB graphical user interface for flight dynamics
analysis. MSc thesis 2003, Cranfield University.
6.
Siliverdis, K. Further development of FDA-CAD, a MATLAB graphical user interface
for flight dynamics analysis and command augmentation design. MSc thesis 2004,
Cranfield University.
7.
Cook, M.V. Flight Dynamics Principles. 3rd Edition. Butterworth-Heinemann, October
2012.
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Michael V Cook
February 2013
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