Airfield Pavement Roughness -Gaps in the Industry-

1. Airfield Pavement Roughness-Gaps in the Industry- ASTM E17 Seminar on Airport Pavement Roughness Issues December 5, 2006 Tony Gerardi APR Consultants, Inc. www.aprconsultants.com

2. The Primary Reason We Strive to Build and Maintain Smooth Pavements is to Minimize Aircraft Dynamic Response and Maximize Aircraft Performance

3. Presentation Overview • Why Smoothness is Important • Acceptance of New Pavements (FAA AC 150/5370 – “16-Foot Straightedge”) • Rejection Criteria (Existing Pavements) • Case Histories • Gaps in the Industry

4. Roughness Defined • Shock Loading • Short wavelength roughness that is too fast for the tires and suspension system to react. (rattles instruments, jars avionics) • Single Axle Loading • Short wavelength roughness that the tires and suspension system is capable of reacting to. (Increases O&S costs, passenger complaints) • Whole Aircraft Loading • Longer wavelength roughness that excites the whole aircraft (Aircraft fatigue damage, reduces braking ability, reduces pavement life)

5. Runway Roughness Evaluation:A Unique Problem • Landing Gear Spacing of nearly 100 Feet • Speeds up to 150 Knots • Aircraft will Respond to Bumps 300 Feet Long or Longer • Multiple Bumps in Succession; Non-Linear Effect • Struts are Primarily Designed for Landing Impact

6. Why Be Concerned About Runway Roughness? Aborted Takeoff Poor Braking Performance Increased Operational & Support Costs & Aircraft Fatigue Damage Reduces Pavement’s Useful Life and Could Result in Costly Unscheduled Repairs Pilot and Passenger Complaints

7. FAA AC 150/5370 (the “P-501 Spec”)New Pavement Acceptance • Criteria • .25 Inch in 16 Feet or PI of 5-7 (in/mile) • .5 Inch Max Deviation from Design Grade* • Difficult to Meet 100% of the Time • Conservative from Aircraft Response Perspective • Can be a Source for Disputes Regarding Pavement Acceptance • Unnecessary Grinding • Led to IPRF/FAA Research Project *Note: Grade Control in the Same as Vehicle Response Control

8. Evolution of Airport Pavement Smoothness 16-Foot Straightedge “Max Deviation Anywhere Along the Length”

9. Evolution of Airport Pavement Smoothness AssessmentCalifornia Profilograph PI of 5-7 Inches/Mile is Conservative

10. Sufficient Accuracy for Airfield Evaluation Relatively Inexpensive Can Track All Event Wavelengths Some Units Can be Painfully Slow Walking Profilers

11. Van, Truck or ATV Mounted Faster than Walking Type Sub Millimeter Accuracy Texture can AdverselyAffect Ride Readings Inertial Profilers (Measure Relative Profile) • Must Have Room to Accelerate/Decelerate • Not as Repeatable As Walking Profilers • More Expensive • Difficulty Tracking Longer Wavelength Events

12. Other Profilers Rolling Inclinometer Wet or Dry Profiler

13. Considerations for Building New Airport Pavements • Evaluate the Design for Aircraft Response • Measure Profile for Smoothness at Each Stage of Construction • Maintain String Line Tension • Measure Profile for Smoothness soon after Placement (Feedback to Paving Crew) • Final MSL Measurement Serves as Baselinefor Tracking Change for That Pavement (Deliverable)

14. IPRF Research Recommended Target Smoothness Values • Rolling Straightedge Length 25 Feet • Threshold of Acceptability .35 Inches • Pavement Section Length 500 Feet • Allowable SSI per Section 5% • Must Repair Value for Keel Section .5-Inch • Must Repair Value for Outer Lanes .75-Inch Note 1: Repeated bumps (3 or more) in the keel section .25 inches or greater will require repair. Note 2: Any longitudinal step bump greater than .25-inch in the keel section will require repair. Note 3: Exceptions apply for intersecting runways, drains on taxiways and ramps.

15. No Official Rejection CriteriaFor Existing Pavements • Unofficial Methods Being Used • The Boeing Curve • IRI / PI / RN • Pilot Reported Roughness • Aircraft Simulation

16. Case Histories • Unnecessary Disputes • Evaluating the Design • Establish a Baseline Profile

17. Case Histories: Disputes • Case Histories • Military Parking Apron in Eastern US (Relax Grade Control Requirements at Very Low Speeds) • Taxiway in Midwest (Straightedge Deviation) • Runway in Southern US (Unnecessary Grinding) • Runway in Western US (Grade Control Issue) • Current P-501 Puts All Stakeholders in an Awkward Position Note: Grade Control is Not Vehicle Response Control

18. Runway in Western US Known Rough Runway (Caused Many Pilot Complaints) Case History Very Smooth New PCC Runway (No Pilot Complaints) Comparison of Runway in Western US to Known Smooth and Known Rough Runway

19. Case History: Evaluate the Design Using Aircraft Simulation • Design Constraints can cause the Design to Produced Unacceptable Aircraft Response • Midwest Runway, (built to design: unacceptable) • Middle East and Orange County CA : Correction made to the design. • Intersecting Runways at Manitoba, in Texas, and in NY • Optimize Drainage and Roughness • Minimize the Impact on the Primary Runway

20. Case History: Settlement • Measure Mean Sea Level (MSL) Profile Before Pavement Opens to Traffic • Use Data for Final Pavement Smoothness Acceptance • Use Data to Establish Baseline • Track Settlement Periodically by Comparing MSL Profiles

21. 2002 Data 1998 Baseline Data Comparing to the Baseline Pavement Profile Acceptance of an Airport Pavement Should Require an MSL Profile Measurement to Establish a Baseline for Future Measurements

22. 2002 Data 2001 Data Baseline Data (1998) Chart Legend (Feet) Quantifying Changes: Settlement

23. Roughness and Stopping Distance • It Takes More Runway to Stop on a Rough Runway • Varies the Normal Load • Tricks the Anti-skid • Difficult to Maintain Steady Brake Pressure • Wheel Hop • Can Make the Difference Whether or not the Runway is Overrun • When Landing Long • Stopping on a Contaminated Runway • or in a High Speed Abort

24. The High Speed Aborted Takeoff • Aircraft is Heavy, Speed is High, Little Runway Remaining……… • Hot Brakes (Blown Tire Fuse Plugs and Fire Hazard) • High Nose gear Loads (Blown Fuse Plugs or Failed Drag Brace) • Risk Overrunning the Runway

25. Conclusions(Gaps in the Industry) • Define the Effect of Roughness on Aircraft Braking Performance • Quantify the Effect of Roughness on Dynamic Loads in a High Speed Aborted Takeoff • Update New Pavement Acceptance Criteria that’s Agreeable to All Stakeholders

26. Conclusions(Gaps in the Industry) • Require a Baseline MSL Profile as a Deliverable for Future Comparisons • Establish Official Rejection Criteria That Defines When an Airport Pavement has Become Too Rough. • Establish a Standard for Evaluating Pavement Roughness

27. Contact Information… APR’s Website: www.aprconsultants.com Or Contact Us By: email: info@aprconsultants.com Tel: (937) 849-6795 Fax: (937) 849-6048