Developing a statistically based correlation between ACN and ACR for conversion of runway PCN to PCR under the new international airport pavement strength rating system

Abstract

Since 1981, runway pavement strength has been controlled by an international rating system. The system is operationally simple, with an index of relative aircraft induced damage compared to an index of pavement strength, with aircraft operators requiring permission to operate when the aircraft damage index ex- ceeds the pavement strength index. The original system was based on the simple mathematics available for pavement thickness determination at the time it was developed. However, pavement thickness determination now uses more sophisticated methods. For consistence between strength rating and design, a new runway strength rating system was introduced in 2024. For many regional airports, transitioning to the new system is a burden, with limited operational benefit, and a simple conversion is therefore desired. Based on comparison of old and new aircraft index values, a statistically reasonable correlation was developed. For runways with a clear and reliable existing strength rating, the correlation between the old and new aircraft damage index can be used to estimate the new pavement strength rating from the old strength rating. Although this approach is likely to be reasonable for flexible runways with a known critical aircraft forming the basis of the old strength rating, it still remains preferable to calculate the actual aircraft damage index for the identified critical aircraft, and adopting that value as the basis of the new strength rating.