A single international method of classifying and reporting pavement bearing strength for aircraft above 12,500 lb (5700 kg) maximum total weight, authorized from the standpoint of the stresses exerted by aircraft loads on pavements. The ACN is a number expressing the relative effect of an aircraft load on a pavement for a specified subgrade strength. The PCN is a number expressing the bearing strength of a pavement for unrestricted operations. A pavement with a particular value can support, without weight restrictions, an
aircraft that has an ACN value equal to or less than the pavement's PCN value. The bearing strengths of pavements intended for aircraft of 12,500 lb maximum total weight authorized or less are reported as the maximum allowable weight and maximum allowable tire pressure. Values of PCNs for runways and other aircraft runways are published in the relevant aerodrome publications. A method of representing PCN is indicated in the illustration.
