ACR-PCR method

The Aircraft Classification Rating (ACR) - Pavement Classification Rating (PCR) method is a standardized international airport pavement rating system developed by ICAO in 2022. The method is scheduled to replace the ACN-PCN method as the official ICAO pavement rating system by November 2024. The method uses similar concepts as the ACN-PCN method, however, the ACR-PCR method is based on layered elastic analysis, uses standard subgrade categories for both flexible and rigid pavement, and eliminates the use of alpha factor and layer equivalency factors.

The method relies on the comparison of two numbers:

• The ACR, a number defined as two times the derived single wheel load (expressed in hundreds of kilograms) that expresses the relative effect on an airplane of a given weight on a pavement structure for a specified standard subgrade strength;
• The PCR, a number (and series of letters) representing the pavement bearing strength (on the same scale as ACR) of a given pavement section (runway, taxiway, apron) for unrestricted operations.

Aircraft Classification Number (ACR)

The ACR calculation process is fully described in ICAO Doc 9157 Aerodrome Design Manual – Part 3 "Pavements" (3rd ed.).

The procedure to calculate the ACR is as such:

1. Design a theoretical pavement according to a defined criterion:
   • For flexible pavements, design the pavement for 36,500 passes of the aircraft according to the layered elastic analysis (LEA) design procedure
   • For rigid pavements, design the pavement to reach a standard flexural stress of 2.75 MPa at the bottom of the cement concrete layer according to the LEA design procedure
2. Calculate the single wheel load with a tire pressure of 1.50 MPa that would require the same pavement – this is the Derived Single Wheel Load (DSWL)
3. The ACR is defined as twice the DSWL, expressed in hundreds of kilograms