FAA Airport Pavement Roughness R&D

1. FAA Airport Pavement Roughness R&D • Gordon Hayhoe, AAR-410, FAA William J. Hughes Technical Center, Atlantic City, New Jersey, U.S.A. www.airporttech.tc.faa.gov • Continue development and maintenance of ProFAA (in process). • Develop a standard for CA Profilograph simulation (in process). • Compare measured and simulated aircraft response (data analysis in process). • Conduct a pilot subjective rating study using the FAA 737 full-motion simulator (planning). 1

2. ProFAA Computer Program • Intended to provide analysis of airport pavement roughness by computing indexes and simulating aircraft response. • An inertial profiling system was developed for measuring runway and taxiway longitudinal elevation profiles from threshold to threshold. • Constant profile measurement speed not necessary. • Profiles are not absolute – somewhere between absolute and normal high-pass filtered. • Suitable for high-speed aircraft simulation. 2

3. Profile Measurement FAA Methodology Standard High-Pass Filter Methodology Measurement speed – profile measured from zero speed to zero speed 3

4. ProFAA Computer ProgramBasic Index Display 4

5. Airport Pavement Profile Data Measured At • Sixteen Airports • U.S.A. and Foreign • 4 Large Hub, 3 Medium Hub, 5 Feeder 4 Foreign large international • Flexible and Rigid Pavements • Runways and Taxiways 5

6. Straightedge versus Profilograph 6

7. Straightedge versus Boeing Bump 7

8. FAA TC Boeing 727-100QC Instrumented Aircraft, N40 • The FAA WJHTC operated a fully instrumented Boeing 727-100 until it was damaged about five years ago during an arrestor bed test. • Measurements were made with N40 in 1997 on a runway and taxiway at a medium size regional airport. • At the same time longitudinal profile measurements were made with the FAA profiler. • The data from these test is now being analyzed to compare measured airplane responses with simulated responses. 8

9. Why Wait Until Now to Analyze the Data. • Development of pavement thickness design procedures and associated full-scale traffic testing consumed most available R&D resources. • The AAR-410 budget has recently been increased and a significant portion of the increase is assigned to roughness work over at least the next three years. 9

10. N40 on Jacks in the Hangar 10

11. Installation of Axle Strain Gages 11

12. Installation of Axle Strain Gages 12

13. Installation of Axle Strain Gages 13

14. Main Gear Force Calibration 14

15. Interior and Instrumentation Racks 15

16. Speed Sensor on Nose Gear 16

17. N40 on Jacks in the Hangar 17

18. Variables Measured on N40. • Vertical and side forces and torque at each wheel on main and nose gears. • Speed at nose gear. • Three-axis accelerations at aircraft cg and floor of cockpit. • Inertial guidance system outputs. • Displacement of control surfaces, throttle, etc. 18

19. Tests Run November 3 and 4, 1997 19

20. Tests Run December 12, 1997 20

21. Tests Run December 12, 1997 21

22. Tests Run December 12, 1997 22

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27. These are Preliminary Steps • Continuing work will include variation of simulation parameters such as: • Flexible body modes. • Pitch moment of inertia for cockpit comparisons. • Strut model parameters – primarily Coulomb and hydraulic friction. • Modify simulation program to accept varying speed. 27

28. ProFAA Computer ProgramStrut Model • Includes damping forces due to: • Velocity squared hydraulic damping. • Strut seal Coulomb friction. • Strut bearing Coulomb friction due to strut inclination. • Two-to-one breakaway-to-sliding friction. • All wheels lumped into one equivalent wheel. • Unsprung mass is ignored. • Gas compression spring. • Linear tire spring with linear damping. 28

29. Subjective Pilot Rating Study Using Full-Motion Simulator - Objectives • Develop a rating scale for pilot subjective response to vertical cockpit vibrations excited by longitudinal pavement surface elevation disturbances. • The scale to range from very smooth to exceedingly rough. • Identify on the rating scale limits for cockpit vibration resulting in uncomfortable conditions and unacceptable conditions. • A similar project has been proposed to ACRP but using field data. 29

30. Why Use a Simulator and Not Operational Airplanes • For • Test repeatability. • Rapid change in profile characteristics. • Cost. • Safety. • Against • Concerns about simulator fidelity. • Difficult to change cockpit characteristics. 30

31. FAA Full-Motion 727 Simulator, Now replaced with a 737 Simulator.Located at Oklahoma City 31

32. Previous Experience • AAR-410 has run projects on the FAA 727 simulator for about 15 years. • High-speed exit geometry and lighting configurations. • High-speed ground handling. • Airplane landing into and arrestor bed. • General lighting and visual guidance studies. • The person responsible for simulator operation has a Ph.D. in human factors as well as being a National Resource Specialist in Simulators. • E1927 “Conducting Subjective Ride Quality Pavement Ratings. 32

33. Subjective Pilot Ratings - Schedule • FY06 (funding obligated) • Develop scope and test plan. • Establish procedures for setting roughness profiles in the simulator computer program. • Develop preliminary rating scale and questionnaire. • FY07 • Continue test plan, etc. • Preliminary simulator study with a small number of pilots to test the scales and other procedures. • Finalize procedures. • FY08 • Run the full experiment with the necessary number of subjects and profiles. • Analysis and report 33