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Aircraft performance
Published in Paul Clark, Buying the Big Jets, 2017
PCN is categorised according to pavement type (rigid or flexible), sub-grade strength (high, medium, low, or ultra-low), tyre pressure, and whether the evaluation method is based upon a dedicated technical appraisal or experience with the aircraft. The ACN is a function of the geometry of the landing gear (such as the distance between the wheels and the number of wheels), the weight of the aircraft, the tyre pressure, the centre of gravity, and the sub-grade category of the pavement. There are trade-off methodologies that enable movements to take place where an aircraft ACN exceeds the runway PCN. These ‘overload operations’ depend upon the percentage of overload movements of the total.
Stochastic strength rating of flexible airport pavements using construction data
Published in International Journal of Pavement Engineering, 2020
The assignment of the numerical strength rating element within the PCN is a critical part of owning and managing an airport. Usually, when a pavement is designed, the PCN is determined based primarily on the aircraft in the traffic spectrum adopted for pavement strength/thickness design. Because the PCN is an advertisement to aircraft operators regarding which aircraft may operate without special permission, it is logical to set the PCN equal to the highest ACN of all the aircraft in the traffic spectrum. That way, all the aircraft in the design traffic spectrum can operate without restriction, while more damaging aircraft (with a higher ACN) must seek a Pavement Concession to operate. Many airports adopt this approach. However, a complication arises when an aircraft with a high ACN is included in the design traffic at a low number of repetitions compared to other aircraft. For example, a pavement designed using APSDS for subgrade CBR 6% to accommodate the aircraft in Table 4 would be assigned a PCN of 90, based on the 1000 passes of the B777-300ER. However, the 100,000 passes of the A350-900 consumes over 50% of the pavement life, and it may be more appropriate to set the PCN to 79, reflecting the ACN of the A350-900. This would avoid more frequent B777-300ER loadings prematurely failing the pavement. However, trigger Pavement Concessions would be triggered for all B777-300ER operations, which might, for example, be managed by a blanket concession up to 500 operations per year, to minimise the administrative burden.
Modification of the airport pavement strength rating system for improved protection of asphalt surfaces
Published in International Journal of Pavement Engineering, 2019
Under the first active element of the rating system, aircraft loads are expressed by a mathematically exact Aircraft Classification Number (ACN). For a specific aircraft at given operating mass and tyre pressure, there is only one ACN per pavement subgrade category. Pavements are assigned a Pavement Classification Number (PCN) at the discretion of the airport owner. Many owners simply use the highest ACN of all the aircraft in the design traffic fleet, despite analytical processes for PCN selection being available (FAA 2014). Where the ACN-PCN ratio is less than or equal to 1.0, aircraft may operate without seeking special dispensation from the airport owner. Where the ACN-PCN ratio exceeds 1.0, a Pavement Concession is required and may incur a financial penalty at the option of the airport owner. Most airport owners will grant Pavement Concessions based on a balance of the ACN-PCN ratio, the condition of the pavement, previous overload history and the revenue to be generated by permitting the aircraft to operate.
Correction for the asphalt overlay thickness of flexible pavements considering pavement conditions
Published in International Journal of Pavement Engineering, 2018
Alessandra Bianchini, Carlos R. Gonzalez, Haley P. Bell
The major objective of structural evaluations is to determine the pavement load-carrying capacity, which is a function of the strength of the pavement, the gross weight of the aircraft and the number of load applications. The method for reporting the pavement load-carrying capacity is the ACN–PCN system as adopted by the International Civil Aviation Organisation (ICAO) and Department of the Army regulation AR 95-2 (Headquarters, Department of the Army 2007). The ACN (Aircraft Classification Number) indicates the relative structural effect of an aircraft on both flexible and rigid pavements for specific standard subgrade strengths in terms of a standard single-wheel load. The PCN (pavement classification number) expresses the relative load-carrying capacity of a pavement for a given pavement life in terms of a standard single-wheel load. The need of increasing the pavement thickness is concluded from the evaluation of the ACN/PCN ratio. As a general rule, for specified mission traffic, ACN/PCN ratios equal to or less than 1.1 have minimal impact on pavement life. If the ACN/PCN ratio greater than 1.1 and less than or equal to 1.4, aircraft operations should be limited to 10 passes and the pavement inspected after each operation. Aircraft operations resulting in an ACN/PCN ratio greater than 1.4 should not be allowed except for emergencies. Thus, if ACN/PCN ratios are greater than 1, the pavement cannot support the specific mission traffic, requires improvement and therefore an increase in thickness.