"The scope of this SAE Aerospace Standard (AS) shall cover the methodology of defining and determining the ""internal volumes"" of both the main deck and lower deck aircraft cargo compartments. The minimum required clearance between the compartment envelope and the unit load devices (ULDs) shall also be stated in order to provide the maximum ULD external contour and the methodology to define the ULD internal volumes. Purpose: The purpose of this document is to establish a uniform methodology for defining and determining the usable internal volume of aircraft cargo compartments and usable external envelope for ULDs which can be accommodated within these compartments. This will provide the aircraft industry with a set of standard terminology which when specified@ can be utilized by the airlines when comparing similar type aircraft. The minimum essential criteria are defined by the key word ""shall."" Recommended criteria are identified by the key word ""should"" and while not mandatory@ are considered to be of primary importance."