The RDA Fortran computer code is a general purpose tool for linear rotor vibration analyses. It is developed on the FE formulations derived in Chapter 2, Section 2.3. First written for use on early generation PCs, it was initially limited to fairly simple rotor-bearing configuration models with 10 or less mass stations (40 DOFs or less) because of the memory limitations of early PCs. RDA was initially written to simulate rotor-bearing systems as part of research efforts on active control of rotor vibration in the author’s group at Case Western Reserve University (CWRU). Validation tests and other background information for RDA are provided by Maghraoui (1989) in his PhD dissertation (see Bibliography at the end of this chapter). RDA has been distributed and used by the author in machinery dynamics courses and student research projects at CWRU for over 20 years and in professional short courses in the United States and Europe. The current enlarged version supplied with this book, RDA99, has now been exercised by countless users since being provided free with the 2001 first edition of this book. RDA99 has been successfully used by the author in modeling several large power plant machinery, in vibration troubleshooting missions (see Part 4 of this book). It has also been successfully used by the author in troubleshooting and redesigning a high-speed vertical spin-pit test rig specially configured for research on aircraft jet engine blade-on-casing tip-rub-induced blade vibrations and transmitted blade-casing interaction dynamic forces.