Aircraft classification number

The aircraft classification number (ACN) is a number expressing the relative effect of an aircraft on the runway pavement for a specified standard subgrade category, using a method defined by the International Civil Aviation Organization (ICAO).

The ACN is a single unique number expressing the relative effect of an aircraft on a pavement for a specified subgrade strength specifying a particular pavement thickness. It consists of a number on a continuous scale, ranging from 0 on the lower end and with no upper limit, that is computed between two pavement types (rigid or flexible), and the subgrade support strength category. ACN values for civil aircraft have been published in ICAO’s Aerodrome Design Manual and in FAA Circular 150/5335-5.

Using the ACN method, it is possible to express the effect of individual aircraft on different pavements by a single unique number, which varies according to pavement type and subgrade strength, without specifying a particular pavement thickness.

The ACN is twice the derived single-wheel load expressed in thousands of kilograms, with single-wheel tire pressure standardized at 1.25 megapascals (= 181 psi). Additionally, the derived single-wheel load is a function of the sub-grade strength.

The ACN of an airplane is a function of not only its weight but also the design parameters of its landing gear such as the distances between the wheels of a multiple-wheel landing gear assembly.

The pavement’s strength is denoted by its pavement classification number (PCN).

The load exerted on a pavement by the landing gear of an airplane is denoted as its ACN, or airplane classification number. The ACN is not permitted to exceed the PCN of the runway to be used, in order to prolong pavement life and prevent possible pavement damage.

The ACN is defined for only four subgrade categories (high, medium, low, and ultra low).

The ACN-PCN system of rating airport pavements is designated by the International Civil Aviation Organization (ICAO) as the only approved method for reporting strength.

“The bearing strength of a pavement intended for aircraft of apron (ramp) mass greater than 5700 kg shall be made available using the aircraft classification number – pavement classification number ACN-PCN method………” (ICAO Annex 14, clause 2.6.2)

The ICAO system for civil airport pavements involves comparison of an airport’s pavement classification number (PCN) with an aircraft classification number (ACN). According to this worldwide ICAO standard, aircraft can safely operate on a pavement if their ACN is less than or equal to the pavement load bearing capacity or PCN. An aircraft having an ACN equal to or less than the PCN can operate without weight restrictions on a pavement. The PCN is formally published in an Aeronautical Information Publication (AIP).

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