This document provides recommended practices for the design of tubing systems that are used for the transmission of liquid and gasses in fluid power systems for aerospace vehicles such as aircraft, missiles and boosters. The primary emphasis is given to recommended practices for line sizing, tube routing, supports and clamping, stress considerations and permissible defects, and provisions for flexure through the use of flexible hoses, coiled tubes, swivel joints, and expansion glands. The sections regarding tubing materials and fitting types are included for reference, but particular recommendations are purposely avoided since their selection is dependent upon the specific requirements of each particular vehicle system and many other factors. Fluid power systems are differentiated from the normal aircraft fuel and oil systems and the various fluid systems used for environmental control and air conditioning systems; however, the practices cited herein will in many cases be applicable to these other systems.
The original version of ARP994 was published in 1976 and, prior to this revision, had not undergone any major revision. In order to update this document to reflect current aerospace design and manufacturing processes, it was decided to break this task into two stages as ARP994 is a large, complex and multi-disciplinary document. The two stages are: a. A basic update of the document to delete obsolete/redundant information and to update references, etc. b. A comprehensive technical update of the document Revision A is the first stage of this update of ARP994.