Presentation on theme: "Airfield Pavement Roughness -Gaps in the Industry-"— Presentation transcript:
1 Airfield Pavement Roughness -Gaps in the Industry- ASTM E17 Seminar on AirportPavement Roughness IssuesDecember 5, 2006Tony GerardiAPR Consultants, Inc.
2 The Primary Reason We Strive to Build and Maintain Smooth Pavements is toMinimize Aircraft Dynamic Responseand Maximize Aircraft Performance
3 Presentation Overview Why Smoothness is ImportantAcceptance of New Pavements (FAA AC 150/5370 – “16-Foot Straightedge”)Rejection Criteria (Existing Pavements)Case HistoriesGaps 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 LoadingShort wavelength roughness that the tires and suspension system is capable of reacting to. (Increases O&S costs, passenger complaints)Whole Aircraft LoadingLonger 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 FeetSpeeds up to 150 KnotsAircraft will Respond to Bumps 300 Feet Long or LongerMultiple Bumps in Succession; Non-Linear EffectStruts are Primarily Designed for Landing ImpactRunway roughness is unique. Gear spacing can be up to 100 feet. Vehicle speeds can be as fast as 150 knots. These two factors can combine to where a 300-foot long event can cause significant aircraft response.Some situations such as multiple event roughness complicate the aircraft response process.And finally, the aircraft’s landing gear are not designed to dampen out the aircraft response to runway roughness. They are principally designed to absorb landing impact.
6 Why Be Concerned About Runway Roughness? AbortedTakeoffPoor BrakingPerformanceIncreased Operational &Support Costs & Aircraft Fatigue DamageReduces Pavement’s Useful Life andCould Result in Costly Unscheduled RepairsPilot 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 TimeConservative from Aircraft Response PerspectiveCan be a Source for Disputes Regarding Pavement AcceptanceUnnecessary GrindingLed 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 PI of 5-7 Inches/Mile is Conservative Evolution of Airport Pavement Smoothness Assessment California ProfilographPI of 5-7 Inches/Mile is Conservative
10 Walking Profilers Sufficient Accuracy for Airfield Evaluation These three devices are typical of the walking profilers available on the market. Generally, they are suitable accurate for evaluating ride quality. Typically, they emulate the California Profilograph and produce a Profile Index to quantify the roughness. They also generally relay the data in terms of IRI. Only the AR&L unit on the uses aircraft simulation to predict the ride quality of the measure profile.These units range from $20K to $40K in cost. And the inertial profilers can be painfully slow.Sufficient Accuracy for Airfield EvaluationRelatively InexpensiveCan Track All Event WavelengthsSome Units Can be Painfully Slow
11 Inertial Profilers (Measure Relative Profile) The inertial profilers are much quicker. The van and truck type profiler can operate at highway speeds. They typically report the smoothness of the pavement in IRI. They get extremely detailed measurements (sub millimeter), but in our opinion not needed to adequately identify airfield pavement roughness. What is needed is to track the longer wavelength events, something that these devices can have some problems with. The middle device is called a “lightweight” device and is made to operate on fresh pavements.These device can get expensive. The lightweight units begin at $50K and the vans can cost up to $300K.Van, Truck or ATV MountedFaster than Walking TypeSub Millimeter AccuracyTexture can Adversely Affect Ride ReadingsMust Have Room to Accelerate/DecelerateNot as Repeatable As Walking ProfilersMore ExpensiveDifficulty Tracking Longer Wavelength Events
12 Other ProfilersRolling InclinometerWet or Dry Profiler
13 Considerations for Building New Airport Pavements Evaluate the Design for Aircraft ResponseMeasure Profile for Smoothness at Each Stage of ConstructionMaintain String Line TensionMeasure Profile for Smoothness soon after Placement (Feedback to Paving Crew)Final MSL Measurement Serves as Baseline for Tracking Change for That Pavement (Deliverable)When building a new runway, it should be build with smoothness in mind from the ground up. In the initial work for this design guide handbook, many phases of the design and construction components impact the initial smoothness of the pavement. The smoother the initial smoothness of a a pavement is, the longer that pavement will maintain its smoothness.Things to consider:- Evaluate the design data to ensure the vertical curves or any pavement intersection doesn’t create a ride quality problem.- Measure the profile of the subbase material to identify and remove any long wavelength events- Measure the profile of the completed pavement to ensure that it meets design and that there are no unwanted wavelengths. This survey will also serve as the historic baseline for that runway.
14 IPRF Research Recommended Target Smoothness Values Rolling Straightedge Length FeetThreshold of Acceptability InchesPavement Section Length FeetAllowable SSI per Section 5%Must Repair Value for Keel Section .5-InchMust Repair Value for Outer Lanes InchNote 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 Criteria For Existing Pavements Unofficial Methods Being UsedThe Boeing CurveIRI / PI / RNPilot Reported RoughnessAircraft SimulationThere is no official rejection criteria for existing airfield pavements. The industry has developed several methods to try to quantify the rideability of the pavement.- The Boeing Curve- International Roughness Index (IRI)- Pilot Reported Roughness- Aircraft Simulation
16 Case HistoriesUnnecessary DisputesEvaluating the DesignEstablish a Baseline Profile
17 Case Histories: Disputes 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 PositionNote: Grade Control is Not Vehicle Response Control
18 Known Rough Runway (Caused Many Pilot Complaints) Runway in Western USKnown Rough Runway (Caused Many Pilot Complaints)Case HistoryVery 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 ResponseMidwest Runway, (built to design: unacceptable)Middle East and Orange County CA : Correction made to the design.Intersecting Runways at Manitoba, in Texas, and in NYOptimize Drainage and RoughnessMinimize the Impact on the Primary Runway
20 Case History: Settlement Measure Mean Sea Level (MSL) Profile Before Pavement Opens to TrafficUse Data for Final Pavement Smoothness AcceptanceUse Data to Establish BaselineTrack Settlement Periodically by Comparing MSL Profiles
21 Comparing to the Baseline Pavement Profile 2002 Data1998 Baseline DataAcceptance of an Airport Pavement Should Require an MSLProfile Measurement to Establish a Baseline for Future MeasurementsReferring to our case study again, this profile shows the baseline profile (bottom) compared to the most recent profile (top). Several areas of change can be identified as the pavement continues it settlement process.Baseline comparison of true profiles allows one to look at the structural integrity of the pavement and the pavement’s subgrade. In the case of HKIA, engineers knew that the pavement would settle, and how much it should settle. They use this technology to ensure all was going according to plan.
22 Quantifying Changes: Settlement (Feet)Chart LegendBaseline Data (1998)2001 Data2002 Data
23 Roughness and Stopping Distance It Takes More Runway to Stop on a Rough RunwayVaries the Normal LoadTricks the Anti-skidDifficult to Maintain Steady Brake PressureWheel HopCan Make the Difference Whether or not the Runway is OverrunWhen Landing LongStopping on a Contaminated Runwayor 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 PerformanceQuantify the Effect of Roughness on Dynamic Loads in a High Speed Aborted TakeoffUpdate 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 ComparisonsEstablish 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:Or Contact Us By:Tel: (937)Fax: (937)