1. COMFAA 3.0 Update Airport Pavement Working Group
Gordon Hayhoe, ANG-E262
Sheraton Atlantic City Convention Center
April 25, 2012

2. COMFAA 3.0 Outline Brief PCN background. Current AC and COMFAA.
Changed radius of relative stiffness multiplier for rigid ACN.
Other possible changes to the AC and COMFAA.

3. The aircraft mfg. provides the ACN.
In the US, the airport determines the PCN using FAA advisory circular guidance.

4. Technical Method for PCN
Find the Maximum Allowable Gross Weight of the Critical Aircraft for it to be able to operate at the Existing Traffic Level on the Existing Pavement.
The ACN of the Critical Aircraft at the Maximum Allowable Gross Weight is then the PCN of the pavement.

5. PCN Calculation for Large-Hub Airports with AC 150/5335-5A
Airports with a large number of narrow-body aircraft (737, A320, etc.) and a relatively small number of wide-body aircraft (777, A360, 787, etc.) can:
Have one of the narrow bodies as the critical aircraft, which will give a fairly low PCN.
Have one or more of the wide-bodies with ACN values at operating weights much higher than the PCN determined by the narrow body critical aircraft.
This will mean that wide body aircraft in the original design mix might not be eligible for operation under the ACN-PCN system.

6. The AC 150/5335-5B PCN Methodology
The AC 150/5335-5A methodology finds the critical aircraft and then finds the ACN of that aircraft at the maximum allowable gross weight. That ACN is then the PCN.
The -5B methodology is the same except that the ACN at maximum allowable gross weight is calculated for all of the aircraft in the mix.
The largest ACN value is then selected as the PCN.
There is a need for a way to eliminate “occasional or overload” aircraft from the mix.

7. AC 150/5335-5B

8. AC 150/5335-5B, Applicability

9. AC 150/5335-5B, Downloads

10. AC 150/5335-5B, Downloads

11. Current COMFAA 3.0

12. Current COMFAA – Aircraft Window

13. Current COMFAA – Details Window

14. Changes To Be Made to COMFAA
The cutoff radius for rigid pavement ACN computation will be changed from 3.0 to 5.0 times the radius of relative stiffness.
Values for only the applicable support strength will be included in Table 2. PCN Values in the Details Window.
Total CDF will be added to Table 2. PCN Values in the Details Window.
Output text files optional by user selection.
Updated Airbus aircraft library.

15. Rigid Cutoff = 3.0, C-17A

16. Rigid Cutoff = 5.0, C-17A

17. Updated COMFAA – Details Window

18. Updated Airbus Library

19. Possible Modification to AC 150/5335-5
Expanded and more precise guidance on when low-traffic aircraft should be considered overload rather than part of the traffic mix.
Contact Jeffrey Rapol for more information at