These recommendations cover the general field of airplane cabin pressurization equipment and are subdivided. PURPOSE: These Aeronautical Recommended Practice is intended to outline design practices and minimum performance recommendations that are based on sound engineering principles and are intended as guides for future standard engineering practices for the aircraft industry. These recommendations are to be considered as being currently applicable and necessarily subject to revision from time to time due to rapid development of the industry. The basis for these recommendations is practical engineering experience with cabin pressurization equipment currently in general use. The material herein is primarily applicable to multi-engine transport aircraft but in some cases may apply to any type of airplane@ military or civil.