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An Evaluation of Winter Operational Runway Friction Measurement Equipment, Procedures, and Research An Evaluation of Winter Operational Runway Friction Measurement
Equipment, Procedures, and Research
submitted by the
WINTER RUNWAY FRICTION MEASUREMENT AND REPORTING
WORKING GROUP
January 25, 1995 EXECUTIVE SUMMARY
For many years, the aviation community has struggled with runway friction reporting practices.
Airport operations personnel, in taking on the responsibility for conducting friction measurements
during winter storms, work diligently to keep up with rapid changes in the weather. Airport
operators should know how to provide pilots with acceptable runway condition reports that
represent the current status of runway surfaces covered with ice and/or snow, and how these
reports aid in predicting aircraft performance under these conditions. Air traffic control (ATC)
should provide standard reports to pilots and must have an agreement with the airport operator on
what standard information the reports are to contain, and how the reports are to be disseminated.
Airlines need to provide instruction and standardized guidelines to their pilots on the use of the
runway surface reports. Pilots interpret what the reports and friction numbers mean to their
aircraft performance for these conditions.
To have both current and reliable information during such circumstances, the aviation community
needs well-established acceptable guidelines. Airport personnel should maintain a high level of
awareness to rapidly changing conditions and recognize these changes in order to provide pilots
with the most reliable information concerning runway surface conditions during inclement weather
conditions.
Therefore, Federal Aviation Administration (FAA) documents must be coordinated so that they
give consistent guidelines for airport operators, pilots, ATC, and the airline industry. This
document produced by the FAA/Industry Winter Runway Friction Measurement and Reporting
Working Group, is designed to provide an overview of current information on the present
guidance, practices, and procedures for reporting runway pavement surface conditions during
winter operations at airports. It contains recommendations on the desirability of providing the best
procedural consistency and standardization and discusses the available means to implement the
guidance that will result in improved aviation safety at airports during hazardous winter
conditions.
Participants of the working group include representatives from the FAA, National Aeronautics
and Space Administration (NASA), Transport Canada, Airports Council International (ACI),
American Association of Airport Executives (AAAE), Air Transport Association (ATA),
Regional Airline Association (RAA), Air Line Pilots Association (ALPA), aircraft manufacturers,
and a technical advisor. Research and development credits for this paper go to: Mr. Francis
Anderson, Transport Canada; Mr. Rick Marinelli, FAA; Mr. Tom Morrow, technical advisor; Mr.
Glenn Morse, ATA; Mr. Wes Te Winkle, FAA; Mr. Jerry Wright ALPA; and Mr. Thomas Yager,
NASA. i
TABLE OF CONTENTS
1.0 Background
1.1 Safety Considerations
1.2 History of U.S. Research on Runway Friction Measurements
1.3 Development of Friction-Measuring Equipment for Winter Operations
2.0 Experience
2.1 History of Winter Condition Reporting
2.1.1 In the United States
2.1.2 In Canada
2.1.3 In Other Countries
2.1.4 International Civil Aviation Organization (ICAO)
2.2.1 Flight Operations
2.2.2 Airport Operators
3.0 Current North American Winter Friction Measurement Criteria
3.1 Pavement Covered with Frozen Contaminants
3.2 Other Contaminants with Combination(s) of above Pavement Conditions
3.3 Correlation between Various CFMEs and DECs
3.4 Friction-Measuring Equipment Performance Standards
3.4.1 Authority
3.4.2 Procedures
3.5 Limitations on the Use of Friction-Measuring Equipment
3.5.1 Limits on Accuracy of Contaminant Recognition and Estimation ii
3.5.2 Influence of Operational Conditions on Measurement Procedures
3.5.3 Calibration of Friction-Measuring Equipment
3.6 Training of Equipment Operators
4.0 Legal Aspects
4.1 Regulatory Requirement or Advisory Guidelines
4.1.1 Regulatory Approach
4.1.2 Advisory Circular Approach
4.2 Compliance Monitoring
4.3 Retention of Reports
4.4 Financial Impact
5.0 Conclusions
6.0 Recommendations
References
Appendices
A
Description of Various Friction Measuring Equipment Used in Winter Operations
B
Transport Canada Airports Winter Surface Maintenance Manual
C
Legal Considerations 1
1.0 Background
Snow, ice, drifting snow, and reduced visibility at airports in areas subject to below freezing
temperatures severely affect wintertime operational safety. The presence of snow, ice, or
slush on airport movement surfaces potentially can cause hazardous conditions that could
contribute to aircraft accidents, incidents, and reduced traffic volumes, resulting in delays,
diversions, and flight cancellations. With the introduction of faster, heavier turbojet aircraft
in the 1960s, braking and cornering performance on snow- and/or ice-covered runways
became more critical. Qualitative pilot braking action reports were found to vary
significantly, and other measurement techniques were needed.
In the late sixties, several European trials were conducted using the Tapley meter described in
Appendix A (Description of Various Friction-Measuring Equipment Used in Winter
Operations) for compacted snow and ice conditions. In addition, some mu-meter side-force
friction trailer correlation tests were performed with the Tapley meter vehicles at Stuttgart,
Munich, and Frankfurt Airports during the winter of 1968-1969. In the late 60s and early
1970s, joint FAA/National Aeronautics and Space Administration (NASA)/United States Air
Force (USAF) research programs involving instrumented aircraft and ground friction-
measuring equipment were performed on compacted snow and ice conditions. Similar tests
were conducted in Sweden and Canada in the early 1970s, and these winter runway friction
measurement tests have continued to the present time. (A partial list of appropriate reference
documents concerning these major investigations is given in References 1-29.)
Tests results have shown that comparisons between measurements made by friction devices
and the effective braking friction developed by aircraft under similar contaminated runway
surface conditions do not correlate directly but can be related indirectly. By conducting many
tests at several speeds on pavements that had various types of microtextural/macrotextural
surfaces, testers also found that friction-measuring devices did provide the airport operator
with the capability to distinguish between runway surfaces which have good or poor surface
friction characteristics. It has, therefore, been concluded that, instead of reporting on an
operational basis the friction characteristics of a wet runway, the runway friction should be
periodically measured to ensure that its friction characteristics are of an acceptable standard.
The periodic measurement serves two purposes. First, it identifies the substandard runways.
Second, it provides qualitative information to airport operators on the condition of runway
surfaces, thus permitting the development of more objective maintenance programs and
justification for development of budgets.
Results of friction tests conducted in the United States, Canada, United Kingdom, and
Sweden confirm that it is desirable to measure the friction/speed characteristics of a new or
resurfaced runway, in order to verify whether the design objective has been achieved. The 2
measurements should be made with a friction-measuring device using self-watering features
at two or more different speeds. An average value at each test speed for the entire runway is
obtained when the runway is wet but clean. To this end, friction-measuring devices that
provide continuous measurements of runway friction characteristics are preferable to those
that provide only spot measurements. This information is considered of operational value, as
it gives an overall indication of the available surface friction along the central portion of the
runway.
In recent years, several new friction-measuring devices such as the Norsemeter, the Tatra,
and the GripTester have been developed and proven reliable. Airport operators have also
utilized in the 1990s larger, faster, and more efficient snow removal equipment, more
accurate weather forecasts, and improved anti/deicing chemicals fo