Airport Pavement Classification: Understanding PCN and ACN
Every published runway and taxiway carries a rating that answers one operational question: can this aircraft use this pavement? The answer rides on a simple comparison — the aircraft’s demand against the pavement’s capacity — expressed historically as ACN versus PCN, and now transitioning internationally to ACR versus PCR. This article explains what each number means, how to read a PCN code, and where the FAA guidance sits.
The basic idea: demand vs. capacity
Pavement strength is not a single number you can read off a tape measure — it depends on the load, how it is distributed across the gear, tire pressure, the pavement type, and the subgrade beneath it. To make airport-to-airport and aircraft-to-aircraft comparison possible, ICAO created a paired index:
- ACN — Aircraft Classification Number. A number expressing the relative effect of an aircraft on a pavement, at a stated weight, for a given pavement type and subgrade category. Higher gross weight, fewer wheels, or higher tire pressure all push the ACN up. The manufacturer publishes ACN tables for each aircraft.
- PCN — Pavement Classification Number. A number expressing the load-carrying capacity of a pavement for unrestricted operations, reported by the airport.
The operating rule is deliberately simple: if ACN ≤ PCN, the aircraft may operate on that pavement without weight restriction. When the ACN exceeds the PCN, operations are not automatically prohibited — they fall into the airport’s overload-evaluation and pavement-management judgment, which considers frequency, pavement condition, and remaining life.
How to read a PCN code
A PCN is never just a number — it is a five-part code, and each part tells you something about how the rating was derived. A typical report looks like 80 / R / B / W / T:
| Position | Meaning | Values |
|---|---|---|
| 1 — Numerical PCN | Load capacity for unrestricted use | e.g. 80 |
| 2 — Pavement type | Rigid or flexible | R (rigid) · F (flexible) |
| 3 — Subgrade category | Strength of the supporting soil | A (high) · B · C · D (ultra low) |
| 4 — Tire pressure category | Max allowable tire pressure | W (high/no limit) · X · Y · Z (low) |
| 5 — Evaluation method | How the PCN was determined | T (technical study) · U (using-aircraft experience) |
So 80 / R / B / W / T reads: a rigid pavement with a numerical capacity of 80, on a medium-strength (B) subgrade, with no practical tire-pressure limit (W), determined by a technical evaluation (T). Because the comparison only holds when the aircraft ACN and the pavement PCN are computed for the same pavement type and subgrade category, those middle letters matter as much as the number.
Where the numbers come from
The PCN is the output of a pavement evaluation, not an input. An engineer evaluates the existing pavement — its layers, materials, condition, and subgrade — against the traffic it must carry, and reports the PCN that the structure supports for unrestricted operations. The FAA’s pavement design and evaluation methodology, including the layered-elastic and software tools used to model this, lives in the airport pavement design advisory circular.
On the aircraft side, the ACN (or ACR) is fixed by the airframe and gear and published by the manufacturer at reference weights. As a planner you generally do not calculate ACN by hand — you read it from the manufacturer’s tables for the relevant pavement type and subgrade, at the operating weight that matters for your study (often the maximum gross weight of the critical aircraft).
The ACR/PCR transition
ICAO has replaced the ACN-PCN method with the ACR-PCR method (Aircraft Classification Rating / Pavement Classification Rating), applicable internationally from late 2024. ACR-PCR keeps the same demand-vs-capacity logic and the same ACR ≤ PCR operating rule, but rebuilds the underlying computation on a consistent layered-elastic basis and a standardized reference subgrade, which improves consistency across pavement types. The reported PCR code is structured similarly to PCN. Expect published values, manufacturer tables, and FAA guidance to migrate from ACN/PCN to ACR/PCR over the coming reporting cycles — during the transition you may encounter either, so confirm which method a published value uses before comparing it.
What this means for a planning study
For most planning work, you are doing one of three things with these numbers:
- Confirming an aircraft can operate. Compare the aircraft’s ACN/ACR at its operating weight against the published PCN/PCR for the matching pavement type and subgrade.
- Documenting the pavement in an ALP or master plan. Carry the published PCN/PCR and the date/method of evaluation into the airport data, and flag pavement that does not support the forecast fleet.
- Scoping a strengthening or reconstruction need. When the forecast critical aircraft demands more than the pavement provides, the gap drives a pavement project — which is then designed under the pavement design AC.
The strength rating is one of several facts that follow from the design aircraft. AvPlot’s Aircraft Classification Library gives you the weights, gear, and design-code attributes of the aircraft you are evaluating, so you start the ACN/ACR comparison from defensible, cited aircraft data rather than memory.
This article is a reference summary for planning use, not a substitute for the governing text. Citations refer to ICAO Annex 14 and Doc 9157 Part 3 (ACN-PCN and the ACR-PCR method), FAA AC 150/5335-5 (Standardized Method of Reporting Airport Pavement Strength — PCN), and AC 150/5320-6 (Airport Pavement Design and Evaluation). Pavement evaluation and design are engineering work — always rely on a current evaluation and the governing documents, and confirm whether a published value uses the ACN/PCN or ACR/PCR method before comparing. See the full airport planning glossary or the AvPlot toolkit.