COMFAA. Acknowledgments. Demonstration and. Rapol, FAA. Ken DeBord and Mike Roginski, Boeing Commercial Airplane Co. Federal Aviation Administration

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1 COMFAA Demonstration and Hands-On Training Presented to: VII ALACPA Airport Pavement Seminar & V FAA Airport Pavement Workshop By: David R. Brill, P.E., Ph.D. Date: Acknowledgments Gordon Hayhoe, Rodney Joel and Jeff Rapol, FAA. Ken DeBord and Mike Roginski, Boeing Commercial Airplane Co. 2

2 Outline Brief review of ACN/PCN system stem and ICAO definitions. FAA guidance on PCN calculation. Draft AC 150/5335-5B and computer programs (COMFAA 3.0 and new support program). Flexible example using COMFAA 3.0. Rigid example using COMFAA 3.0 for a large hub airport. Using COMFAA 3.0 additional features. 3 The ACN/PCN System - General Aircraft Classification Number (ACN) is specified as a standard by ICAO in Annex 14 to the Convention on International Civil Aviation. Aircraft manufacturers are required to publish properly computed ACN values for all of their aircraft. Pavement Classification Number (PCN) procedures are given in the ICAO Aerodrome Design Manual, Part 3, Pavements. The PCN procedures in the manual are for guidance only and a great deal of latitude is provided. Airport operators are responsible for determining and publishing PCN values for runways. 4

3 ICAO Documents Annex 14 to the Convention on International Civil Aviation ICAO Aerodrome Design Manual Part 3 Pavements 5 ACN/PCN System - Definitions ACN A number expressing the relative effect of an aircraft on a pavement for a specified standard subgrade strength. PCN - A number expressing the bearing strength of a pavement for unrestricted operations. Therefore, if a particular aircraft at a given weight has an ACN less than, or equal to, the PCN of a particular pavement (ACN PCN), then no restrictions need to be placed on operation of that aircraft on that pavement. Special provisions for overload evaluation. 6

4 ACN Computation ACN is computed as the ratio of a computed (derived) single-wheel load to a reference single- wheel load. Flexible: Based on the US Army Corps of Engineers ESWL CBR method of design using alpha factors adopted by ICAO October Thickness is computed for 10, coverages. Rigid: PCA Westergaard interior stress method of design. Thickness is computed for 10,000 coverages. These are fixed, standard procedures. Other design procedures or traffic levels cannot be substituted. 7 Subgrade Strength for ACN Computation Flexible: The CBR of the subgrade soil. Rigid: The k-value at the top of the support, including all subbase layers. It is not the same as the k-value of the subgrade soil. 8

5 PCN Reporting Format PCN values are reported in a coded format using 5 parts separated by / Sample 39/F/B/X/T Information includes: Numerical PCN Value (39 in this example) Pavement Type (F = Flexible, R = Rigid) Subgrade Strength Category (A, B, C or D) Allowable Tire Pressure (X 1.5 MPa = 218 psi) PCN Evaluation Method (U = Using, T = Technical) 9 Proposed Change to ICAO PCN Tire Pressure Limits (Flexible Only) Tire Pressure Current ICAO Proposed ICAO Category Designations and Limits Designations and Limits W High: no pressure limit Unlimited Medium: pressure limited High: pressure limited to X to 1.50 MPa (217.6 psi) 1.75 MPa (253.8 psi) Y Z Low: pressure limited to 1.00 MPa (145.0 psi) Very low: pressure limited to 0.50 MPA (72.5 psi) Medium: pressure limited to 1.25 MPa (181.3 psi) Low: pressure limited to 0.50 MPA (72.5 psi) 10

6 PCN Using Aircraft Method Find the ACN of all of the aircraft regularly using the pavement and pick the largest ACN to be the PCN of the pavement. But see page 3-27 of the ICAO manual: Support of a particularly heavy load, but only rarely, does not necessarily establish a capability to support equivalent loads on a regular repetitive e basis. Where is the line between regular and overload operation? 11 PCN Technical Method The ICAO manual al covers in detail a very broad range of methods, including: Any rational design procedure developed d specifically for airport pavements but applied in reverse for pavement evaluation. Pavement surface deflection measured under the load from a representative aircraft. Non-destructive test results with backcalculation. Allows for design and evaluation procedures not in use when the manual was written. 12

7 FAA Guidance on PCN Calculation The FAA is responsible for certifying ing all commercial airports in the U.S. and is the organization generally responsible for complying with international agreements on aviation. Well defined procedures are therefore required for determining and publishing PCN values for runways at all commercial airports in the U.S. 13 AC 150/5335-5A (2006) Standardized di d Method of Reporting Airport Pavement Strength th PCN Complete rewrite of AC 150/ Standardized the procedures for computing and reporting PCN values for inclusion in the 5010 database. AC 150/5335-5A 5A is based in large part on the procedures described in Boeing Report D Precise Methods for Estimating Pavement Classification Number, D is, in turn, based largely on recommendations contained in the ICAO Aerodrome Design Manual. 14

8 Draft Advisory Circular 150/5335-5B AC 150/5335-5A, 5A PCN, to be replaced by AC 150/5335-5B. 5B. Draft AC was posted for comment October Comment period has ended. Copy of draft AC is included d on the CD. 15 AC 150/5335-5B STANDARDIZED METHOD OF REPORTING AIRPORT PAVEMENT STRENGTH - PCN The Pavement Classification Number (PCN) field has been added to FAA Form 5010 and data collection is underway. During each airport inspection, the airport owner will be asked to provide runway PCN information. WHY? With release of AC 150/5320-6E, the design aircraft concept has been replaced. This means the Aircraft Gross Weight fields on the 5010 will no longer be used to describe load carrying capacity of runways. 16

9 AC 150/5335-5B PCN Gross Weight data may transition. PCN data request now part of all airport inspections The Master Record is required to be updated periodically. PCN is now mandatory and Gross Weight data will possibly be phased out with time. 17 Draft AC 150/5335-5B - Changes from AC 150/5335-5A5A The procedure for selecting the critical aircraft has been substantially revised. The procedure for computing equivalent departures has been replaced by a new procedure based on cumulative damage factor (CDF). Except for obtaining the structure and aircraft properties, the procedure has been completely automated in a revised version of the computer program COMFAA (COMFAA 3.0). A spreadsheet application i has been developed d to facilitate determining the evaluation thickness. 18

10 Draft AC 150/5335-5B The design procedures recommended in the new AC are: CBR ESWL with the new alpha factors for flexible pavements. Edge stress Westergaard as implemented in AC 150/5320-6C and -6D. The PCA center stress method can also be selected in COMFAA 3.0. These were selected for backward compatibility with established methods and compatibility with the ACN computation procedure. 19 New PCN Methodology The current methodology (-5A) 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 new methodology is the same except that the ACN at maximum allowable gross weight is calculated l for all of the aircraft in the mix. The CDF procedure is used for equivalent coverages. The largest ACN value is then selected as the PCN. There is a need to eliminate occasional or overload aircraft from the mix. 20

11 ACN-PCN Technical Evaluation 7 Basic Steps to Determine Pavement Classification Number in AC 150/5335-6B: 1. Identify pavement features and properties. 2. Determine traffic mixture. 3. Convert traffic to equivalent traffic of critical aircraft. 4. Determine allowable operating weight of critical airplane. 5. Determine ACN of critical airplane at allowable weight. 6. Repeat with each airplane the critical airplane. 7. Report PCN. 21 AC 150/5335-5B Computer Programs COMFAA 3.0 Program Support Spreadsheet for COMFAA (Excel) Input Support: Flexible Layer Equivalency Worksheet Rigid Pavement k-value Worksheet Output Support: Output Data Parsing Rigid and Flexible Chart Creation FAA Form 5010 Preparation 22

12 COMFAA Support Spreadsheet Flexible Layer Equivalency The equivalent pavement has three layers: 5i in. P401 P-401, 8 in. P-209, P-154. The spreadsheet determines the maximum thickness for the equivalent pavement based on the userdefined layer equivalency factors. 23 COMFAA Support Spreadsheet Flexible Pavement Input ENTER (or confirm) layer equivalency factors. Refer to Table A2-1. Reference Guidance AC 150/5335-5B Appendix A-2 Fig. A2-2 Figs. A2-1, A2-2 Flexible Pavement Convert Convert Structure Items to P-209 to P P-401 and/or P Existing Flexible Pavement Layers ENTER P-401 and/or P-403 Existing Layer Thickness 6.0 in P ENTER P in P ENTER P in. ENTER all existing pavement layers P starting at the surface ENTER P in. 1.4 ENTER P-208 P-208 and/or P and/or P-211 of the pavement in. 1.1 P-301 n/a ENTER P in. ENTER the subgrade P-154 n/a 1.0 ENTER P in. ENTER Subgrade CBR CBR value. Equivalent Thickness, in

13 COMFAA Support Spreadsheet Flexible Pavement Output t 0 Existing Pavement Equivalent Pavement COMFAA Evaluation Criteria P-401 Evaluation thickness t = 33.8 in. Evaluation CBR = 9.0 Recommended PCN Codes: F/B/W or Recommended PCN Codes: F/B/X PAVEMENT TO BE EVALUATED IN COMFAA in. th from Surface, i Dept P-401 P-209 P-154 Subgrade CBR 9.0 P-209 P-154 Subgrade CBR 9.0 The spreadsheet determines and consolidates COMFAA software input values and recommends three of five necessary PCN codes. The spreadsheet updates the graphical representation of the existing and equivalent pavement. 25 Using the COMFAA 3.0 Program 26

14 COMFAA Input 27 Aircraft Window COMFAA Input 28

15 Main Window - COMFAA Input Click PCN Flexible Batch Click CBR Enter Enter the evaluation 9.0 in the dialog box. thickness = 33.8 in. 29 COMFAA Output Click Details to view the detailed output. Message Flexible Computation Finished 30

16 COMFAA Detailed Output Screen Summary Aircraft Table with -6D Thickness Requirements 31 COMFAA Output Details (I) () COMFAA generates an aircraft ACN table. CBR 9 indicates B subgrade designation. PCN based on using aircraft ACN can be reported as

17 COMFAA Output Details (II) COMFAA generates a table based on the CDF method. For each aircraft, allowable gross weight and corresponding PCN are identified. CBR 9 indicates B subgrade designation. 33 COMFAA Output Details (III) CDF method identifies (3) aircraft that contribute substantial ti structural t damage based on pavement structure: , , and A300-B4. PCN based on technical CDF method can be reported as the highest PCN of these aircraft =

18 COMFAA Detailed Output Screen Copy and paste data into COMFAA support spreadsheet. 35 COMFAA Support Spreadsheet Data Parse Copy/Paste output data into Cell B5 Click Create Flexible Pavement Charts Airplanes are ordered by PCN number, with the aircraft at top giving the highest PCN when treated as critical. 36

19 COMFAA Support Spreadsheet Flexible Charts AC 150/5335-5B Example Rigid Pavemen nt Thickness 35 in. 30 in. 25 in. 20 in. 15 in. 10 in. 5 in. 1. 6D thickness at traffic mix GW 2. CDF thickness at max. GW 3. Evaluation thickness from equivalent pavement Most Demanding Aircraft in Traffic Mix 0 in. ``` DC A300-B ER Max.Allowable Aircraft 378, , , , , ,830 GW from CDF 5. Aircraft GW from traffic mix 370, , , , , ,000 1,200 1, Airp plane Gross Weig ght, lbs. (thousan nds) Thickness Comparison Compare thickness and gross weights. When CDF thickness (yellow) is less than evaluation thickness (red), excess PCN is available. 37 COMFAA Support Spreadsheet Flexible Charts AC 150/5335-5B Example Subgrade cod de= B at CBR= 9.0, t= 33.8 PCN= 90 PCN= 80 PCN= 70 PCN= 60 PCN= 50 PCN= 40 PCN= 30 PCN= 20 PCN= Aircraft ACN at traffic mix GW 2. Calculated PCN at CDF max. GW 3. Annual Departures from traffic mix Most Demanding Aircraft in Traffic Mix PCN= DC A300-B ER , ,500 3, ,500 3,000 2,500 2,000 1,500 1, Annual Departure es PCN Comparison PCN needed for using traffic is 54. PCN based on CDF analysis can be reported as high as

20 Technical Method Example Case 1 International hub airport. Rigid pavement. Large number of narrow-body, dual-wheelgear aircraft. Example courtesy of Rodney Joel. 39 CASE 1 AIRCRAFT ACN gear Operating Weight, lb Gear Load. lbs. Wheel Load, lbs. Avg Annual Departures Total Coverages 20 yrs DC-9-30/40 D B D A std D Traffic Data A std D , A D , MD-80/83/88 D MD-90 D B basic D B D , B D , DC-8-60/70 2D A300-b4 std 2D B D , DC-10 2D B D A std 2D A std 2D MD-11 2D B D A380 (2D) 2D B base 3D ,

21 CASE 1 Existing Pavement Data 17 PCC, R = 775 psi 8 CTB k-value = 160 psi/in Effective k at top of base = 323 psi/in The original design based on procedures in AC 150/5320-6D called for 16.3 inches of PCC. This value was rounded to 17.0 inches. 41 CASE 1 Pavement thickness requirements based on actual annual departures: FAA AC 150/5320-6D PCA method B appears to be the design airplane based on A procedures. B is comprised of several D gear airplanes. AIRCRAFT ACN gear Operating Weight (lb) Annual Departures -6D Edge Load Thickness (in) PCA Design Thickness (in) DC-9-30/40 D B D A std D A std D , A D , MD-80/83/88 D MD-90 D B basic D B D , B D , DC-8-60/70 2D A300-b4 std 2D B D , DC-10 2D B D A std 2D A std 2D MD-11 2D B D A380 (2D) 2D B base 3D ,095 Federal 8.85 Aviation

22 CASE 1 Current Procedure Following A procedures the B would become the Critical Aircraft due to its individual pavement thickness requirement. This is true for either the D procedure or the PCA center slab procedure. It was speculated that the B737 was artificially elevated as the design airplane due to high departure levels caused by lumping several D-gear airplanes into one. 43 CASE 1 AIRPLANE ACN gear Allowable Operating Weight Equiv. Annual Departures A PCN/R/B DC-9-30/40 D A std D B D A std D A D B D MD-80/83/88 D PCN values calculated A std D by following the procedures in AC 150/5335-5A 5A and MD-90 D assuming that each B basic D airplane is the design B D A300-b4 std 2D airplane. DC-8-60/70 2D In this mix, the B737- B D is comprised of A std 2D A std 2D several D gear A380 (2D) 2D airplanes, some with B D lower operating DC-10 2D weights. B D MD-11 2D B base 3D

23 CASE 1 ACN values for each airplane (from COMFAA) Assuming the B as the design airplane per the procedures in A Calculated PCN 59.8/R/B PCN = (60/R/B) AIRPLANE Gear type for ACN Operating Weight Airplane ACN/R/B A std D DC-9-30/40 D B D A std D B D A D B baseline 3D MD-80/83/88 D B basic D MD-90 D B D DC-10 2D A300-b4 std 2D B D DC-8-60/70 2D A std 2D A std 2D B D A380 (2D) 2D B D MD-11 2D operate ion nes can o ut restricti Airplan withou ht tions Weig Restrict 45 Case 1 New CDF PCN Procedure The procedure for finding equivalent coverages in AC 150/5335-5A is based on gear equivalency factors and the ratio of wheel loads. An alternative procedure based on cumulative damage factors (CDF) gave more consistent, and rational, results. The new procedure for finding equivalent coverages has been incorporated in the new AC 150/5335-5B. 46

24 COMFAA 3.0 Case 1 47 COMFAA Support Spreadsheet Rigid Pavement k-value Each subbase layer contributes to an improved subgrade support k-value. ENTER all existing pavement layers. ENTER the flexural strength of the concrete and the subgrade support k-value. The spreadsheet updates the graphical representation of the existing and equivalent pavement. 48

25 COMFAA 3.0 Aircraft Window 49 COMFAA 3.0 Case 1 Results Subgrade Category B 50

26 COMFAA 3.0 Case 1 Results Copy and Paste Data into Support Spreadsheet 51 COMFAA Support Spreadsheet Case 1 Data Parse Copy/Paste output data into Cell B5 Click Create Rigid Pavement Charts Airplanes are ordered by PCN number, with the aircraft at top pgiving g the highest PCN when treated as critical. Next, click Rigid Chart tab. 52

27 COMFAA Support Spreadsheet Rigid id Charts Case 1 AC 150/5335-5B Example hickness Rigid Pavement Th 18 in. 16 in. 14 in. 12 in. 10 in. 8 in. 6 in. 4i in. 2 in. 0 in. 1. 6D thickness at traffic mix GW B A std Most Demanding Aircraft in Traffic Mix `` A std B787-8 A380-Wing (Preliminar y) MD CDF thickness at max. GW Evaluation thickness from equivalent pavement 4. Max.Allowable Aircraft GW from CDF ,076, , ,764 1,558, , , Aircraft GW from traffic mix 877, , ,000 1,235, , ,000 1,800 1,600 1,400 1,200 1, bs. (thousands) e Gross Weight, lb Airplane Thickness Comparison Compare thickness and gross weights. When CDF thickness (yellow) is less than evaluation thickness (red), excess PCN is available. 53 COMFAA Support Spreadsheet Rigid id Charts Case 1 AC 150/5335-5B Example.0, t= 17.0 Subgra ade code= B323 PCN= 110 PCN= 100 PCN= 90 PCN= 80 PCN= 70 PCN= 60 PCN= 50 PCN= 40 PCN= 30 PCN= 20 PCN= 10 PCN= 0 1. Aircraft ACN at traffic mix GW Most Demanding Aircraft in Traffic Mix B A A A380- std std Wing Calculated PCN at CDF max. GW 3. Annual Departures from traffic mix PCN Comparison most demanding 400 aircraft in mix. 300 PCN needed for using traffic is PCN based on CDF analysis can 0 B787-8 be reported as MD11 high as 96. Next, click on Form 5010 tab. (Prelimina ry) Annual Departu ures 54

28 COMFAA Support Spreadsheet Rigid id Charts Case 1 Project info FLEXIBLE PAVEMENT MAXIMUM TIRE PRESSURE METHOD USED TO DETERMINE PCN A Subgrade Category (CBR 15) B Subgrade Category (CBR 10) C Subgrade Category (CBR 6) D Subgrade Category (CBR 3) RIGID PAVEMENT A Subgrade Category (k 552 pci) B Subgrade Category (k 295 pci) C Subgrade Category (k 147 pci) D Subgrade Category (k 74 pci) W Unlimited Using Aircraft X 218 psi Technical Form 5010 Enter PCN Number. PCN can be reported as: Y 145 psi Z 73 psi p AIRCRAFT GEAR TYPE IN TRAFFIC MIX S (single wheel gear) D (dual wheel gear) 2D OR 3D (dual tandem OR triple tandem wheel gear) W/B (tandem gear under wing AND tandem gear under body) 96/R/B/W/T Enter PCN 96 FAA Form 5010 Data Element Gross Weight and PCN #35 S 100 #36 D 280 #37 DT 793 #38 DDT #39 PCN 96 / R / B / W / T 55 Case 1 PCN Comparison PCN calculated l assuming each airplane is treated t as the design airplane D Gears 2D Gears 80 PCN or ACN B757 B777 B747 A A 5A PCN/R/B B PCN/R/B Airplane ACN/R/B , , , ,000 1,000,000 1,200,000 1,400,000 Reported Operating Weight, lbs. (not the weight used for PCN calculation) 56

29 COMFAA 3.0 Options Batch Runs all airplanes in succession. Automatically invoked by PCN Flex and Rigid Batch function. Metric PCA Thick Equivalent coverages computed with the PCA interior stress design method. PCA GW Maximum gross weight computed with the PCA interior stress design method. 57 COMFAA 3.0 Computational Modes ACN Computes ACN at indicated gross weight & strength. PCN Computes PCN using CDF-based procedure. Thickness Computes by AC 150/5320-6D procedure. MGW Computes maximum gross weight for airplane. Life Computes coverages to failure for indicated thickness. Interior Stress Edge Stress 58

30 COMFAA 2.0 Will Continue to be Supported Simpler and Old Alphas 59 More Information Contact Dr. Gordon Hayhoe FAA Airport Technology R&D Group Click on Downloads then Pavements 60

31 Questions? 61