A388
Topic Author
Posts: 7453
Joined: Mon May 21, 2001 3:48 am

ACN-PCN Relation And Calculation

Hello,

I read that an aircraft can land on a runway with a higher ACN value compared to the runway PCN. How can this be determined? I thought that the PCN could never be exceeded by the ACN. If an aircraft lands on a runway with a higher ACN on a frequent basis, how can it be calculated how often such aircraft are allowed to land on the runway?

What do the different letters mean, such as F, B, X, U, A, W, T? I assume these letters can be used in all combinations depending on the calculation and/or condition of a runway?

Best regards,

A388

flymatt2bermud
Posts: 551
Joined: Tue Jan 31, 2006 11:58 am

RE: ACN-PCN Relation And Calculation

If the ACN for an airplane is lower than or equal to the reported PCN for an airport pavement, the airplane can operate without weight restriction on that pavement. For example, if you have a PCN of 81/F/B/W/T and you have an ACN of 53 for a 388,000 lb 767-300ER on a flexible pavement with a B subgrade, that airplane can operate at that airport at 388,000 lbs for an unlimited number of annual operations. On the other hand, if the PCN happened to be 51, the 767-300ER could not operate at that airport at 388,000 lb for unlimited operations. It may, however, be able to operate at a lower weight or be able to operate on a limited number of operations at the higher weight. This would have to be coordinated with the airport authority.

 Quoting A388 (Thread starter):What do the different letters mean, such as F, B, X, U, A, W, T?

The number in the PCN string relates to the allowable weight of the aircraft. The first letter refers to (F)lexible or (R)igid pavement. The second letter relates to the bearing strength of the subgrade soil beneath the pavement. The third letter gives a range of allowable tire pressures, and the fourth letter is the evaluation method. If the fourth letter is a "T" , that means that a technical evaluation of the pavement was conducted. "U" indicates that the "Using Aircraft" method of evaluation was used. That is to say that the equivalent ACN of the highest gross weight of the largest airplane currently using the airport is reported as the pavement strength for the pavement.

Pavement Classification Numbers (PCN), are reported as a 5-part code. For example: PCN 65/F/A/W/T:
Part 1 - 65, the PCN the highest permitted ACN at the appropriate subgrade category.

Part 2 - F, the type of pavement: F = flexible, R = rigid.

Part 3 - A, pavement subgrade category:
....................................PAVEMENT........PAVEMENT
Code......Category.............CBR*................K, PCI*......
...A.......... HIGH ..............OVER 13 ..........OVER 400
...B........ MEDIUM............. 8 - 13 ..............201 - 400
...C........... LOW.................4 - 8 .............100 - 200
...D...... ULTRA LOW...........0 - 4 .............UNDER - 100
*K, PCI = Kilograms per cubic inch.
*CBR= Bearing capacity of a soil
Part 4 - W, maximum tire pressure: the maximum authorized for the pavement. W = high, no limit. X = medium, limited to (217 psi). Y = low, limited to (145 psi). Z = very low, limited to (73 psi).

Part 5 - T, pavement design/evaluation method: T = technical design or evaluation, U = by historical data of aircraft using the pavement.

Now, someone tell me where I put the aspirin?ÃÂ

[Edited 2010-02-10 09:49:01]
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci

flymatt2bermud
Posts: 551
Joined: Tue Jan 31, 2006 11:58 am

RE: ACN-PCN Relation And Calculation

Had to refer back to this for my own recollection!
"When once you have tasted flight, you will forever walk the earth with your eyes turned skyward" Leonardo Da Vinci

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