Manufacturer s Perspective- Airport Pavement Needs and Maintenance Issues Michael Roginski, PE Principal Engineer Boeing Airport Technology VII ALACPA Airport Pavement Seminar Miami, FL December 6-9, 21 Outline Trends in current aircraft design- effect on pavement design Aircraft compatibility with airports- concerns of the manufacturer and airline customers Pavement maintenance issues- effect on aircraft and airlines Manufacturer s involvement with industry and regulators to address pavement issues and establish standards
Trends in Current Aircraft Design ACN-Aircraft Aircraft Timeline (Gross Wt) 1,4, Airplane Gross Weig ght (lb) 1,2, 1,, 8, 6, 4, Commercial fleet when ACN/PCN, method adopted ICAO Adopted ACN/PCN method B747 747-4 A34-6 MD-11 B777 A38 B747-8 B777-3ER B787-8 DC-8 Convair 88 2, B77 Commercial fleet since the COMET 4 B727 ACN/PCN, method Constellation DC-3 B-17 Viscount YS-11 adopted Heron 193 194 195 196 197 198 199 2 21 22
ACN-Aircraft Aircraft Timeline (Wheel load) Airpla ane Wheel Load (lb) 7 6 5 4 3 2 1 DC-3 Commercial fleet when ACN/PCN, method adopted COMET 4 DC-8 B727 ICAO Adopted ACN/PCN method B747 B-17 VISCOUNT CONSTELLATION YS-11 B77 CONVAIR 88 HERON A34-6 MD-11 747-4 B777 B777-3ER A38 B747-8 B787-8 Commercial fleet since the ACN/PCN, method adopted 193 194 195 196 197 198 199 2 21 22 Year Aircraft Introduced Tire Pressure Trend 17. 16.5 16. 16.1 15.7 16.1 Tire Pre essure (bar r) 15. 14. 13. 12.4 12.5 14.1 14.4 15.2 15. 15.2 15.2 12. 11.7 11.7 11.9 11. 727-2 (19,3) 737-3 (13,7) 767-3ER (21,6) ) A3-C4 (19,3) 777-2 (19,3) 737-7 (16,1) A32-2 (18,) 777-3ER (27,2) ) A34-6 (27,4) Aircraft (SWL-kg) 747-4ER (24,2) ) A38-8 (26,7) A38-8F (28,1) 787-8 (25,2) 747-8 (26,2) A35-9 (3,8) 8 s 9 s CURRENT FUTURE
Trends in Pavement Loading ACN FB* 9 ACN 8 787-9 747-8 LR 777 CONCORDE 7 767-4ER A34-6 A38 787-8 DC-1/MD11 747-44 747-4ER 6 A33 DC8-63 777-3 L1-11 A34 5 767-3 A3 77 A31 New Aircraft 747-1 4 777 (A MARKET) 767-2 3 77 FLEXIBLE PAVEMENT ACN'S ARE BASED ON ALPHA FACTORS APPROVED BY ICAO IN OCTOBER 27 2 195 196 197 198 199 2 21 22 *FB Flexible (asphalt pavement) on a medium-strength subgrade Year in Service How does the Aircraft Manufacturer Design for Pavement Loading Develop an initial ACN requirement based on the trend line and similar aircraft Preliminary size the landing gear geometry to be compatible with subgrade code B and C airports- ~ 7% of all airports If the ACN falls below trend line- consider future derivative growth and higher weights and assess competitive aircraft Target airports determined from marketing must be assessed- goal of 2/3 compatibility Resizing of gear geometry must take into account aircraft performance Problem airports can be worked as they arise based on airline input
Wingspan Increase Over Time ICAO Design Standards Wing Span (M) 8 Code F < 8 m 7 6 5 Code E < 65 m 747-1 DC-1-3 Code D < 52 m 747-4 777-3ER 777-2/3 MD-11 767-4 747-8 787-9 787-8 787-3 EIS TBD 767 Winglets 4 DC-1-1 767-2 767-3 757-2 757-3 757 Winglets 3 Code C < 36 m 737 NG 737 Winglets 737-1 737-3 After-Market Winglet 2 1965 197 1975 198 1985 199 1995 2 25 21 215 March 29 Entry into Service (Year) Takeoff Field Length ft 12, m 4, Concorde DC-8-63 767-4 777-3 A34-3 A34-6 3, 737-7 737-3 727-2 A319 77-12 77-32 DC-8-55 DC-1-1 A34-2 DC-1-3 777-3ER MD11 747-1 A33-2 A3-3 747-4 A38-8 A38-8F 8, 737-1 DC-9-32 A321 A31-3 A3-6 777-2 747SP Takeoff field length 2, DC-9-15 717-2 767-2 A32-2 757 A318 DC-3 4, 1, kg 1 2 3 4 5 6 lb 2 4 6 8 1 12 Gross weight x 1E5
Aircraft Compatibility with Pavement Aircraft Compatibility with Pavement What are the manufacturers concerns?: Improved design procedures and software to handle today s heavier aircraft with more complex gear geometries Standardized pavement rating system (PCN) - Many old rating systems still in place - Airlines need accurate PCN ratings in order to assess feasability of operations. Lack of updates to country Aeronautical Information Publication (AIP) does not reflect runway improvements and true bearing strength of pavements.
Improved Design Procedures and Software Pavement Ratings- Confusion between various rating methods Pavement Rating Types: ESWL:Equivalent Single Wheel Load Obsolete LCN: Load Classification Number Obsolete AUW: All Up Weight Obsolete FAA: All Up Weight by Gear type-no rating for tridem gears FAA now requiring PCN ratings for US airports ACN/PCN: ICAO Standard since 1981
Airport Source Data- Jeppesen Example How does an airline determine route feasibility for a 777? FAA Gear Rating System 2D landing gears Constant gross load of 2, lbs Same gear type but with different wheel spacing Increasin ng Thickn ness Required Thickness of Flexible Pa avement. 4 38 36 34 32 3 28 26 24 22 Constant Weight (2, lbs) - Increasing Departures Changing Wheel Spacing 2D-2-45 2D-2-45 2D-21-46 2D-26-51 2D-3-55 Which 2k, 2D gear was used to generate an allowable gear load? B-767gear 45-56 A33-3gear 55-78 With CBR=5, New Alpha Factors 2 1 1 1 1 1 1 Annual Departures (Log Scale) Increasing Frequency
LCN Rating System LCN rating typically does not note pavement thickness, no way to assess pavement loading PCN Rating System- Preferred Method What is ACN/PCN? ACN (Aircraft Classification Number): Describes the relative load intensity of an airplane s main landing gear. PCN (Pavement Classification Number): Describes the relative load-carrying capacity of an airport runway, taxiway or ramp. PCN ACN 72RBWT Rating Number 2 types of Pavement 2 types of basis for evaluation 4 strengths of soil support 4 tire pressure ranges ACN PCN means Unrestricted MTOW
Industry Need for Standardization Overlay Effects on Pavement PCN- AIP Updates are an Ongoing Process 777 Flexible Pavement Life ACN PCN 8 8 7 6 5 777-3ER Code B Subgrade ACN Program 7 6 5 t=3 PCN 66FB PCN 59 FB Example Pavement CBR 1 Subgrade 2-year Pavement Life S-77-1 Design t-=32 4 3 2 3 4 5 6 7 8 Gross Weight, 1, lb 4 3 5, 2 1 1, 1, 1, 1,, Annual Departures Sh th ff t f 2 i h Shows the effect of a 2-inch overlay on pavement life
Pavement Maintenance Issues Boeing Bump Criteria-Runway Roughness 2 Bu ump heig ght, cm 15 1 5 Unacceptable USAF airplane design criteria MIL-A-8862A paved airfields ICAO tolerable limits (annex 14) Runway vertical curve (ICAO annex 14) Excessive Acceptable FAA smoothness criteria 1 2 3 4 5 Bump length, m ICAO standard of construction 6
Long Wave Depression Bump Definition Rod Length Bump Length 5.1 Centerline Bump height 3C Elevation, m 5. North 3N 4.9 South 3S 4.82 6+22 6+25 6+28 Runway Station, m 6+34 Airplane Load Factor Exceedances- Fatigue Life Concern 1 Takeoff Roll Exceeda ances per flight 1 Landing Rollout 1. Typical Rough Runway- Takeoff Roll.1.2.4.6.8 1. Incremental vertical acceleration at CG (g units)
Airports Surveyed by Boeing Example of Results From Worldwide Roughness Testing 2 16 Unacceptable Excessive Bump Height, cm 12 Alaska Greece 8 Chile Canada Tanzania 4 South Pacific Acceptable Columbia CIS 1 2 3 4 5 6 Bump Length, m
757-2 MLG Truck Beam Fracture- Short Wave Roughness Issue Airline: TransAero (TRX) Date: June 2 th, 1996 Place: Yekaterinburg, Russia Runway Profile Analysis-Short Wave Roughness 3D Relative Power Spectral Density Rough Accepta able Run nway Dis stance (m m) 15m Relative e Runwa ay Height PSD (d B) 2 7 Bump Wavelength (m)
Runway Profile Issue- Contaminated Condition Runway Transverse Cross Sections Station +66 4 35 3 Elevation cm 25 2 15 1 5-5 5 1 15 2 25 3 35 4 45 Runway Width m Station +63 Elevation cm 4 35 3 25 2 15 1 5-5 5 1 15 2 25 3 35 4 45 Runway Width m
Runway Cross Sections Station 2+25 Elevatio on cm 35 3 25 2 15 1 5-5 5 1 15 2 25 3 35 4 45 Runway Width m Station 2+58 levation cm E 35 3 25 2 15 1 5 5 1 15 2 25 3 35 4 45 Runway Width m Boeing Runway Roughness Criteria
Effect on the Customer Airline Rough runways can affect aircraft landing gear- high vertical acceleration loads caused by long wave roughness cannot exceed limit loads used for design. Often the source of pilot complaints (i.e. shaking instruments, sudden jolt in pilot seat) Short wave roughness can lead to excessive heating of truck beam pivot joint leading to potential for failure and requiring increased inspection and lubrication intervals for airlines (i.e. more cost to airline). Water impingement due to contaminated runways not meeting proper profile gradient has led to issues for some airlines- replacement spares. Runway Friction- Slippery Runway Effects on Aircraft Landings Reference landing distances in flight operations manual based on reported braking action, i.e. good, medium or poor
Correlation of Aircraft Braking With Runway Friction Measurement 5.5 2% 15% 15% 4.4 2% Braking Coefficient.3.2.1 Falcom 2 Uniform surfaces Falcom 2 Other surfaces Boeing aircraft Turboprop aircraft Linear fit.2.4.6.8.1 Canadian Runway Friction Index Braking coefficients for all aircraft for all aircraft versus Canadian Runway Friction Index Manufacturer Involvement with Industry and Regulators to address Pavement Issues Airport Authority of India Airport Authority of India
Revised Alpha Factor Curves From the FAA NAPTP 1.4 1.2 1. Loading.8 Repetition Factor,.6 Alpha.4 2.2 12-Wheel Failure 12-Wheel Nonfailure 5-kip Single Wheel Failure 3-kip Single Wheel Failure 3-kip Single Wheel Nonfailure Dual-Tandem Failure NAPTF 4-Wheel NAPTF 6-Wheel Alpha =.23 log C +.15 Single Wheel Twin Tandem 6 Wheels 1.E+ 1.E+1 1.E+2 1.E+3 1.E+4 Aircraft Traffic Volume Factor, Coverages 1.E+5 High Tire Pressure Effects on Flexible Pavements-Testing at the NAPTF
ICAO Roughness Curve Approved for Annex 14, Vol. 1, 5 th Edition Bump height, cm 2 15 Unacceptable Excessive 1 Temporarily acceptable 5 Acceptable 1 2 3 4 5 Bump length, m 6 ICAO Activity-ICAO AOSWG Pavement Sub-Group Future Topics Tire Pressure Classification-categories in ICAO PCN rating system need to be more representative of current aircraft. New tire pressure categories, validated by test, have been accepted pending formal approval by ICAO member states. PCN rating system- lack of guidance in ICAO ADM Part 3. More complex landing gears and newer construction ti materials since early 8 s Pavement Overload- current ADM Part 3 has general guidance on permitted overload, more precise method may be possible using cumulative damage factor (CDF) approach. Pavement management and inspection procedures should be improved Improved ACN/PCN methodology-layered elastic method
Conclusions Manufacturer s Roles and Responsibilities: Provide ACN s to airlines for all their commercial products. Airport planning manuals for airports- aid in master planning Support airlines on pavement loading issues. Provide site-specific support to airlines and airports, as requested. PCN analyses and testing as needed Responsibility that new aircraft do not exceed limits of current pavement technology- verification by full scale testing Keep worldwide pavement community abreast of future aircraft technology- airports need to plan for future infrastructure upgrades Thank You!