Friction on contaminated runways

Operational friction means assessment of runway surface friction characteristics during poor meteorological conditions, when runway is covered with water, snow or ice. The assessment of operational friction characteristics and the nature of information to be transmitted are not supervised by rules or standards but by ICAO recommendations.

This statement led STAC to carry out an extensive information-gathering study to establish state-of the-art-practices. Relevant ICAO documents have been reviewed and two specific surveys have been sent to airport manager and air traffic control services from both French and foreign airports. Personal contacts with professionals from aeronautical industry (aircraft manufacturers, airlines, airport managers, air traffic services) have been established to flesh out the study and to refine analysis.

The survey has had a high response rate from French airport operators and French air traffic controller, showing their interest for this thematic. The survey has highlighted the following points:

• Vocabulary dedicated to runway surface description varies between the different documents and recommendations. It does not always correspond to aircraft manuals. Discrepancies between the different texts have also been found out.
• Aircraft performances, at take-off or landing, on contaminated runways are determined from three inputs: nature of contaminant, depth of contaminant, friction coefficient.
• A complete layout of these data, especially the manual contaminant depth measurements, requires a lot of time and hampers operational use of the runway.
• The great number of friction measurement devices and insufficient match between friction measurement and aircraft performances is a source of concerns for airport managers and pilots. Use conditions of these devices should be clarified.