This well regarded series for students taking the commercial and airline transport pilot licences has been substantially revised to bring it into line with the new European Joint Aviation Requirements (JARs) for flight crew licensing. Each volume deals with the material required by one of the new JAR papers. This volume covers those subjects traditionally referred to as 'Radio Aids'. It includes not only those systems, ground and airborne equipment, comprising the JAR Radio Navigation paper, but also the basic principles of radio wave propagation and communications required in the Aircraft General paper. The volume also covers those warning systems which use radio principles. It continues to cover basic principles, as well as communications and navigation equipment. Emphasis on obsolete systems has been reduced to allow increased coverage of modern equipment. Coverage has been expanded on displays and satellite communications and navigation systems, as well as warning systems for terrain and collision avoidance and altitude monitoring. The opportunity has been taken to simplify the presentation of information so as to aid revision work. Many test questions and answers have been included, based on the JAR syllabus.