Final answer:
The APU OVERSPEED warning procedure is located in the aircraft's Quick Reference Handbook (QRH) or the APU section of the aircraft's operating manual, providing instructions for pilots and technicians.
Step-by-step explanation:
The procedure for an APU OVERSPEED warning message is typically found within the aircraft's Quick Reference Handbook (QRH) or the Auxiliary Power Unit (APU) section of the aircraft's operating manual. Pilots and aircraft technicians turn to these manuals for step-by-step instructions to address and troubleshoot the issue at hand. The QRH provides concise, step-by-step emergency and abnormal procedures for pilots to follow in a variety of situations, whereas the APU section of the operating manual offers detailed information about the operations, limitations, and warnings related to the APU.