The DC-9 APU Troubleshooting Guide by Garrett is a comprehensive resource specifically designed for troubleshooting and maintenance of the DC-9 aircraft auxiliary power unit (APU). This guide, made in the United States, provides detailed instructions and diagrams to help users identify and resolve issues with the APU system. With a focus on the DC-9 make, this guide is a valuable tool for aviation professionals seeking to ensure the optimal performance and longevity of this aircraft's APU system.