Operations of Flight
The challenge of slippery runways
Landing on Contaminated Runways involves increased level of risk related to deceleration and direction control, same is valid for a rejected takeoff. The term “contaminated” refers conditions whenever standing water, ice, snow, slush, frost in any form, heavy rubber, or other substances are present.
Contaminated runways are therefore not confined to winter conditions, but equally relevant for geograhical regions experiencing periods of heavy rainfall.
Information provided to pilots on runway condition today is not directly a level of the stopping performance of an aircraft. One of the main challenges for pilots is to translate the information provided to them on runway surface conditions, assess how this practically affect, and whether the surface conditions ensure a safe landing.
Properly assessing and reporting runway conditions have been a challenge for the aviation community for decades and still a recurring issue in runway overrun aircraft accident investigation reports.
How is It Reported
Today there are two primary ways of reporting runway surface conditions,
they are pilot reports ( ) and descriptive assesment of the type of contaminants and to what extent they cover the runway.
Both of these methods have inherit weaknesses. Pilot reports are rather subjective, same objective conditions may be perceived differently from one pilot to another. Qualitative assessement of the runway surface conditions are difficult and subjected to inaccuracies. Furthermore, timeliness of the information is also a factor.
Friction measurement equiment is no longer in use for operational reporting due to the fact that they do not correlate to the dynamics of an aircraft braking.
The aviation community has for a long time sought to find ways and methods to improve the accuaracy and reliability of runway condition reporting.
The Need for Improved Methods
US National Tranportation Safety Board issued in 2007 their aircraft accident report on a Southwest Airlines Boeing B737 runway overrun and collision at Chicago Midway International Airport.
Image from NTSB AAR-07/06 PB2007-910407
In this accident the airplane rolled
through a blast fence, an airport perimeter fence, and onto an adjacent roadway, where it struck an automobile before coming to a stop. A child in the automobile was killed, one automobile occupant received serious injuries, and three other automobile occupants
received minor injuries.
Although slippery runways and the inability to properly report conditions have been a recurring issue in runway excursion accident reports, this report has very much served as a catalyst and increased focus on improving the quality of information. The report also states dircetions to look.
The excerpts below are from respectively the analysis and recommendation part of the accident report.