- Pavement Classification Number
The Pavement Classification Number (PCN) is an
International Civil Aviation Organizationstandard used in combination with the Aircraft Classification Number(ACN) to indicate the strength of a runway, taxiwayor airport ramp(or apron). This helps to ensure that the airport ramp is not subjected to excessive wear and tear and thus lengthen its life.
Although important for the runway the major use of this number is for the apron. On
landingthe aircraftis light on fuel and usually less than 50% of the weight of the aircraft touches the runway in one go. On takeoffthe aircraft is heavy but as the aircraft accelerates the weight gradually moves from the wheels to the wings. It is while the aircraft is being loaded and taxiingprior to departure, that the apron experiences significant loads from aircraft weight.
Typically this is only used for
asphaltor concreterunways and would not be used for grassor gravel.
How it Works
The PCN is actually expressed as a five part code, separated by forward-slashes, describing the piece of pavement concerned.
The first part is a numeric value expressing the actual assessed strength of the pavement. The second part is a letter: either an R or an F, depending on whether the pavement itself is of a rigid or a flexible design.
The third part is another letter from A to D expressing the strength of what is underneath the pavement, known as the
subgrade. So a subgrade of A would be very strong, most likely a reinforced concretesubbase. A subgrade of D would be very weak, most likely uncompacted soil.
The fourth part is either a letter, or a number with units expressing the maximum
tire pressurethat the pavement can support. In terms of letters, W is the highest, indicating that the pavement can support tires of any pressure, the others are as follows:
The fifth and final part just describes how the first value was worked out, a T indicates technical evaluation, and a U indicates usage -- a physical testing regime.
So a PCN of 80/R/B/W/T means that the underlying (probably asphalt) has a bearing strength of 80, is rigid, it's on a medium subgrade, it can withstand a tire pressure of 217 psi or higher, and this has been calculated through technical evaluation.
* [http://www.tc.gc.ca/CivilAviation/International/Technical/Pavement/management/operations.htm Transport Canada - Pavement Operations]
* [http://www.tc.gc.ca/CivilAviation/International/Technical/Images/ALR_Table.jpgTypical Aircraft Load Ratings]
* [http://www.tc.gc.ca/CivilAviation/International/Technical/Images/plr_chart.jpgPavement Load Rating example]
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