Increased demand for measurements of airport pavement strength

The International Civil Aviation Organization (ICAO) has issued new guidelines for classifying the strength of airport runways. As previously, the new method consists of one classification for aircraft and one for runways. However, the new method replaces the current Aircraft Classification Number (ACN) and Pavement Classification Number (PCN) with Aircraft Classification Rating (ACR) and Pavement Classification Rating (PCR). The purpose of the change is to obtain a more accurate and more diverse picture of the physical capacity of runways.

Håkan Carlsson is laboratory manager for measurement technology at VTI. He spends a good deal of his time measuring the pavement strength at airports all over Sweden. Carlsson explains that, although the classifications are new, the measuring equipment and methods are the same. Tests are still conducted using VTI’s falling weight deflectometer (FWD), which applies a dynamic load to simulate the passage of a heavy wheel load. The FWD applies a force of at least 100 kilonewton (kN) and measures the resulting strain. The measurements show the stiffness of the structure and the elastic moduli of the bearings at the measurement points. These values are then analysed to measure pavement strength.

“It is in the analysis that the new method comes in. It is more comprehensive and takes more parameters into consideration than previously, such as the various types of aircraft and amount of traffic using an airport,” says Carlsson.

The old method used calculations based on standard loads for aircraft, but now different aircraft types are added together to obtain a summary of the different planes that operate at the airport. If an aircraft that has a greater impact on the runway starts using an airport, or if the overall amount of traffic increases, it may be necessary to perform a new analysis.

As a result of the new guidelines, Carlsson and his colleague, senior researcher Abubeker Ahmed, have had to delve deeply into how to perform calculations and analyses using the new method. Ahmed is an expert on surface degradation processes and the pair have jointly adapted the guidelines to Swedish conditions in consultation with Swedavia, which owns and operates Sweden’s airport infrastructure, and other stakeholders.

“Climate and materials have a significant impact on the pavement strength and working life of runways, so we can’t directly apply the ICAO’s basic method here in Sweden or elsewhere in the Nordic region.”

While the Swedish Civil Aviation Administration (LFV) is not officially introducing the new guidelines in Sweden during 2025 or 2026, Carlsson has noticed increased demand for new measurements and analyses. Rather than the usual 5 to 10 airports per year, he anticipates that VTI will have performed measurements and analyses at 15 to 20 airports by the end of the year.

Text: Hillevi Ternström

Translation: CBG