Recent progress towards predicting aircraft ground handling performance

Capability implemented in simulating aircraft ground handling performance is reviewed and areas for further expansion and improvement are identified. Problems associated with providing necessary simulator input data for adequate modeling of aircraft tire/runway friction behavior are discussed and efforts to improve tire/runway friction definition, and simulator fidelity are described. Aircraft braking performance data obtained on several wet runway surfaces are compared to ground vehicle friction measurements. Research to improve methods of predicting tire friction performance are discussed

Highly Abrasion-resistant and Long-lasting Concrete

Studded tire usage in Alaska contributes to rutting damage on pavements resulting in high maintenance costs and safety issues. In this study binary, ternary, and quaternary highly-abrasion resistant concrete mix designs, using supplementary cementitious materials (SCMs), were developed. The fresh, mechanical and durability properties of these mix designs were then tested to determine an optimum highly-abrasion resistant concrete mix that could be placed in cold climates to reduce rutting damage. SCMs used included silica fume, ground granulated blast furnace slag, and type F fly ash. Tests conducted measured workability, air content, drying shrinkage, compressive strength, flexural strength, and chloride ion permeability. Resistance to freeze-thaw cycles, scaling due to deicers, and abrasion resistance were also measured. A survey and literature review on concrete pavement practices in Alaska and other cold climates was also conducted. A preliminary construction cost analysis comparing the concrete mix designs developed was also completed

Recent Progress Towards Predicting Aircraft Ground Handling Performance

The significant progress which has been achieved in development of aircraft ground handling simulation capability is reviewed and additional improvements in software modeling identified. The problem associated with providing necessary simulator input data for adequate modeling of aircraft tire/runway friction behavior is discussed and efforts to improve this complex model, and hence simulator fidelity, are described. Aircraft braking performance data obtained on several wet runway surfaces is compared to ground vehicle friction measurements and, by use of empirically derived methods, good agreement between actual and estimated aircraft braking friction from ground vehilce data is shown. The performance of a relatively new friction measuring device, the friction tester, showed great promise in providing data applicable to aircraft friction performance. Additional research efforts to improve methods of predicting tire friction performance are discussed including use of an instrumented tire test vehicle to expand the tire friction data bank and a study of surface texture measurement techniques

Stormwater-Pavement Interface in Cold Climates

This project relates to “managing stormwater runoff in cold climates” and addresses the feasibility of low-impact development at a regional demonstration site in eastern Washington. The studies relate to seven large permeable pavement systems. The findings for similar climates and soils are as follows: The draindown times for retention in Palouse or similar clay soils may handle many typical storms. On average, every square foot of a permeable pavement system installed also receives run-on from another square foot of impermeable pavement, doubling its impact on both stormwater quantity reduction and stormwater quality improvement. Most of the clogged sections on various applications were downslope of other areas. Permeable pavements installed in areas targeted for additional stormwater quantity control and quality improvement may be feasible. On average, the cleaning for installations is less frequent than annually. Power washing plus vacuuming appears to be an effective method for pervious concrete. Surface distress was usually where vehicles turned, or from placement activities. Preliminary studies on various surface treatments on pervious concrete show promise for added safety benefits under wintry conditions. Both detention-type and retention-type permeable pavement systems appear to have little negative impact on neighboring soils in the winter under the study conditions. However, further research is needed for different designs of retention-type systems to ensure that water volumes in the aggregate storage bed do not allow for sufficient water flow into neighboring soils that might result in ice lens formation or other negative impacts

Wet runways

Aircraft stopping and directional control performance on wet runways is discussed. The major elements affecting tire/ground traction developed by jet transport aircraft are identified and described in terms of atmospheric, pavement, tire, aircraft system and pilot performance factors or parameters. Research results are summarized, and means for improving or restoring tire traction/aircraft performance on wet runways are discussed

Aquaplaning - The British Ministry of Technology programme

Critical water depth required for hydroplanin

Skid Resistance of Pavements [Sept. 1972]

Standard pavement types and experimental surfaces on roads throughout Kentucky were evaluated in terms of skid resistance and effects of traffic, wear, and polishing. Friction-vs-speed gradients and the relationships between locked-wheel and incipient friction were determined. Asphaltic concrete pavements on high-speed, four-lane roads were found to be significantly more skid resistant than on two-lane highways and somewhat more skid resistant than concrete surfaces (especially those containing calcareous gravel aggregates). Sand-asphalt surfaces containing significant proportions of limestone sands showed inadequate level of friction for the traffic sustained. Several experimental sand asphalts without limestone sands exhibited greater skid resistance; Kentucky rock asphalt surfaces remain the most skid resistant of all surfaces investigated

Effects of Subsurface Drainage on Pavement Performance

This report evaluates the effects of subsurface drainage features on pavement performance through a program of inspection and testing of the subsurface drainage features present in the Long-Term Pavement Performance (LTPP) SPS-1 and SPS-2 field sections. The report will be of particular interest to engineers in the public and private sectors with responsibility for the design, construction, and rehabilitation of highway pavements

Highway Skid Resistance

The physics of friction and traction are reviewed. Hypotheses are presented. Use of a scanning electron microscope to detect and identify polishing aggregate is presented. Size reduction (crushing) produces greater concentrations of sharp edges, reducing flat and plane surfaces not otherwise contributing to traction. Surface permeability and drainage through macrotexture was evaluated by an air-percussive device. An air-efflux device was contrived for evaluating hydroplaning potential and for evaluating open-graded surface courses. In-filling has been observed where road debris is abundant. Grippers and sharpness are needed for wet traction . Drainage is needed to lower hydroplaning potentials. Sand-sizes optimize the concentration of grippers; open-graded chip-sized surfaces maximize drainage and dissipation of pressure under tires

Airport pavements evaluation

The airport pavement deteriorates during service due to traffic and climate effects therefore systematic monitoring is required in order to assess their structural and functional condition. The aim of this work is to present the methodologies used nowadays for airport pavement evaluation and to contribute to their improvement in structural analysis area The main aspects that are addressed are the application of the Ground Penetrating Radar (GPR) and the use of the Falling Weight Deflectometer (FWD) tests, for structural evaluation, and the use of the GRIP tester and the measurement of texture depth of the wearing course layer, for the functional evaluation of the runway. Also, freeware computer softwares used to design new runways (FAARFIELD and COMFAA) are presented and examples are given. Case studies are described both for structural and functional evaluation