ACR-PCR: The New Airport Pavement Rating Method Explained

Airport pavements produce a significant amount of greenhouse gas emissions throughout its lifetime. The International Civil Aviation Organisation (ICAO) encourages airport owners to tackle this issue with a holistic approach, calling upon all stakeholders, including airports, aircraft manufacturers, airlines, and regulators. ICAO’s efforts aims to reduce the airfield pavement’s impact on the environment while improving the pavement’s safety and durability. The implementation of the new ACR-PCR approach can lead to decreased GHG emissions, minimised costs, and optimised aircraft operational weights. Therefore, the goal of the new system is to achieve sustainable and efficient airfield pavements.

This blog provides a summary of ICAO’s working paper on ‘Pavement Asset – Optimisation Of The Overall Lifecycle Of Pavement For Mastering Aircraft Operations, Cost Efficiency and GHG Footprint’. The paper discusses the transition from semi-empirical methods to the layered elastic analysis (LEA) for pavement design and analysis, along with its adoption as the new ICAO pavement rating method known as the Aircraft/Pavement Classification Rating (ACR-PCR) system.

The key points from the paper is outlined below.

1. The evolution of pavement design

Over the last two decades, layered elastic analysis (LEA) has replaced the semi-empirical California Bearing Ratio (CBR) design method. LEA offers improved pavement design and monitoring of remaining pavement life and better management of aircraft weight and frequencies at airports.

2. The move from ACN-PCN to ACR-PCR

LEA became the core principle of the ICAO ACR-PCR system, effective from July 2020 with full applicability by November 2024. ACR-PCR considers landing gear configuration and new-generation pavement materials, reducing conservatism compared to the ACN-PCN system that was based on CBR for flexible pavements.

3. ACR-PCR’s damage-based approach

ACR-PCR enables the optimised use of existing and future pavements. It employs a cumulative damage factor (CDF) to assess the impact of overload operations and improve pavement life predictability.

4. The shift from reactive to predictive maintenance

Airfield pavement maintenance based on failure is hazardous and costly. The ACR-PCR system, with its cumulative pavement damage principle, allows for monitoring and anticipating pavement failure through routine maintenance.

5. Importance of accurate PCR determination

PCR calculation is complex, relying on multiple skills related to pavement materials, geotechnics, and damage modelling.

Accurate PCR determination requires careful collection and analysis of aircraft traffic and pavement data. This begins with conducting a structural analysis of the pavement using Heavy Weight Deflectometer. Pavement Management Services uses output from the (HWD) which enables airport asset owners to:

·         Improve and understand pavement structural modelling

·         Determine the layer of failure and the optimum rehabilitation solutions.

·         Use the data for quality control on existing and new pavement construction

6. Benefits of ACR-PCR for the industry

The ACR-PCR system enhances pavement use and ensures consistency between pavement design and aircraft admissibility assessment. It contributes to GHG reduction along the pavement life cycle through predictive maintenance and usage optimisation.

7. Next-generation aircraft and optimised landing gear

LEA can be further improved with NEXT GEN aircraft through optimised main landing gear footprint. The system takes into account parameters like individual wheel load, main gear leg geometry, and tire inflation pressure, and how it impacts aircraft weight distribution on pavements.

8. Advantages of incorporating ACR-PCR into Pavement Management Systems (PMS)

ACR-PCR implementation offers a unique opportunity to establish the world's airfield-pavement heritage, improving PCR determination and publication for each airport. Integration of ACR-PCR and traffic data monitoring in PMS allows for ultimate pavement use optimisation and to better anticipate any damage due to unexpected traffic changes.

Conclusion

The International Coordinating Council of Aerospace Industries Associations (ICCAIA) encourages ICAO and all stakeholders to optimise the airfield pavement life cycle while considering economic, operational, and environmental benefits. This gradual replacement of semi-empirical methods with ACR-PCR can lead to airport cost reduction in all pavement phases and benefit from the next generation of aircraft.

Further reading

This information was extracted from ICAO’s paper on ‘Pavement Asset - Optimisation Of The Overall Lifecycle Of Pavement For Mastering Aircraft Operations, Cost Efficiency And GHG Footprint’. Obtain the full paper via https://www.icao.int/Meetings/a41/Documents/WP/wp_269_en.pdf