From ACN-PCN to ACR-PCR
For decades, the load-bearing capacity of paved airfield surfaces has been described using the ACN-PCN system.
In this context, ACN stands for Aircraft Classification Number and PCN stands for Pavement Classification Number. Simply put, so far: if the ACN value of an aircraft does not exceed the published PCN value of the respective surface, regular operation is generally possible, provided that no further restrictions exist.
ICAO is now replacing this procedure with Aircraft Classification Rating and Pavement Classification Rating, or ACR and PCR, respectively.
The basic principle remains similar: the ACR describes the load-bearing capacity of an aircraft, while the PCR describes the carrying capacity of the respective airfield surface.
If the ACR is equal to or less than the published PCR, the aircraft can basically be operated on this area – subject to additional restrictions, for example regarding mass or tire pressure.
New values are not comparable to old PCN numbers
One point is particularly important and is explicitly pointed out by Austro Control:
There is no direct mathematical conversion between the current ACN-PCN system and ACR-PCR.
An old PCR value of, for example, 70 cannot therefore be meaningfully compared with a new PCR value of 700.
The fact that the new figures appear to be several times higher does not mean that a slope has suddenly become significantly more sustainable. It simply involves a different calculation method and a new scaling.
Therefore, old experience gained after the motto „my aircraft has ACN 18 and the runway PCN 25“ cannot be transferred to the new system.
Why ICAO changed the procedure
The main advantage of ACR PCR lies in a more accurate calculation of the actual load.
The previous system was conceived in a time when computer calculations were significantly less powerful. The new method can more accurately account for chassis configurations, wheel loads, tire pressure, and the various characteristics of the ground.
This should allow airport operators to better utilize their paved areas.
A too conservative classification can lead to certain aircraft being unnecessarily excluded. On the other hand, an overly optimistic classification can cause long-term damage to the pavement structure.
ACR-PCR is intended to more accurately determine this balance.
ICAO has already switched to 2024
Since November 28, 2024, ACR PCR has been considered the new ICAO procedure internationally.
However, the binding implementation in the EASA member states was deliberately postponed. The reason is that airports, authorities and air traffic information services should switch to the new system as soon as possible.
Otherwise, different countries within Europe could publish different classifications in parallel, which would create unnecessary uncertainty for international operators.
Also in autumn 2026, Austro Control has not yet announced a specific launch date for Austria. This will be published separately.
Austria has already largely prepared the calculations
Although the formal transition is still pending, extensive PCR values have already been calculated for the major Austrian air traffic hubs.
These include:
Graz-Thalerhof, Innsbruck, Klagenfurt, Linz, Salzburg and Vienna-Schwechat.
Not only the slopes have their own values; the trails and individual areas of the ski area are also evaluated separately.
This makes sense, because the runway is by no means the weakest area of an airport.
For example, an aircraft can easily land on the main runway, but then be too heavy for a specific landing path or a smaller GA parking area.
Vienna shows the differences particularly clearly
At Vienna Airport, the differences between individual flight operations areas become very clear.
All four slopes 11, 29, 16 and 34 have a PCR value of 900 F/A/W/T.
Parts of the field and various running paths, however, have values of 1,100, while others have only 700 or 800.
This shows that for larger aircraft, it is not enough to solely consider the load-bearing capacity of the runway; the entire planned route and the landing area must be suitable.
For classic light GA aircraft, this hardly plays a role. However, for heavy business jets, it can become relevant.
What does „900 F/A/W/T“ mean, for example?
As with the previous PCN system, the new system also consists of several components.
The number is the actual PCR value.
Next comes the type of pavement structure. „F“ stands for flexible surfaces, typically asphalt. „R“ stands for rigid pavement, that is, rigid structures such as concrete.
The next letter describes the load-bearing capacity of the underground structure.
Next comes the permissible tire pressure category.
The last letter describes the method by which the PCR value was determined.
This means that a value such as „900 F/A/W/T“ contains significantly more information than just the number 900.
Significant differences in GA areas
The values at specific GA thresholds are particularly interesting for general aviation.
In Salzburg, for example, the General Aviation Center receives a PCR of 225 F/A/W/T, while the main runway is rated at 900 F/A/W/T.
In Graz, the GAC field is at 530 F/A/W/T, while another hangar field only reaches 95 F/A/W/T.
In Innsbruck, a direct mass limit of 2,000 kilograms is still being specified for the Nord front.
This also means that in the new system, careful examination of the actual used areas remains important.
For small SEP systems, this is usually not a practical problem.
For typical aircraft such as the Cessna 172, the Piper PA-28, the Diamond DA40 or comparable SEP models, the load-bearing capacity of fixed-wing airfields usually does not constitute an operational limitation.
These aircraft are very light in relation to the dimensions of the wings.
It may be different for larger turboprops and business jets.
A King Air, PC-12, or a heavy business jet generates significantly higher load capacities. Additionally, the suspension geometry and tire pressure can be at least as important as the pure MTOM.
It is precisely here that ACR PCR should enable a more realistic assessment.
Pilots and operators must look to the ACR in the future
For a planned operation, the ACR value of the specific aircraft type or the respective operating mass must be compared with the published PCR of the airport area in the future.
The corresponding ACR values are provided by the aircraft manufacturers or through appropriate calculation methods.
The mass is also important: a plane with a lower weight can have a lower ACR than one with the maximum takeoff mass.
In certain cases, reduced operating weights can also play a role.
Overload operation remains basically possible
As before, a higher ACR than PCR does not necessarily mean that an aircraft may never operate on the surface.
Airfield operators can assess and allow overcapacity operations under certain conditions.
Among other things, the frequency of movements, the extent of the overshoot, the condition of the area and the expected structural effects are taken into account.
Therefore, an individual release may be possible for a single business jet flight, even though the regular ACR is above the published PCR.
However, this is a decision made by the airport operator and not a decision that a pilot can make independently.
Why the change is also economically interesting
The new method is not just a technical detail.
Pavements are among the most expensive infrastructure components of an airport. Frequent or unnecessary renovations cause significant costs, while congested areas can quickly develop damage.
A more precise assessment allows the actual lifespan to be better utilized and maintenance measures to be planned more purposefully.
ICAO and EASA therefore expect lower life-cycle costs and indirectly also lower emissions through more efficient use and maintenance of the infrastructure.
Conclusion
With ACR PCR, Austria is also facing a fundamental change in the assessment of the load-bearing capacity of airport land.
For pilots, the principle remains largely unchanged: the aircraft's load-carrying capacity must, in normal operation, in principle not exceed the published load-carrying capacity of the area.
What is new, however, are the calculation and numerical values. ACN and ACR, respectively PCN and PCR, cannot be directly compared or converted with each other.
Austrian air traffic control has already largely determined its new values. Austro Control will announce separately when it will officially replace the current ACN-PCN system.
For most light GA aircraft, the change remains a background issue. Operators of heavier turboprops and business jets should familiarize themselves with ACR PCR, especially if smaller runways, taxiways, or GA areas are to be used.
Source references:
Austro Control
