Background
Research activities related to winter weather are designed to improve the nowcast and forecast of winter weather conditions that impact aviation operations (e.g., deicing of aircraft, runway clearing, sanding, and plowing, and air traffic operations) at airports. RAL R&D efforts are diverse and include: developing improved systems to produce snow in a reliable and repeatable fashion in order to test deicing fluids; developing a hotplate snowgauge; evaluating snowgauges; operating a ground-based winter test facility at the Marshall field site; and supporting an operational Weather Support for Deicing Decision Makers (WSDDM) system at Denver International Airport. Current sources of funding are from the FAA Aviation Weather Research Program (AWRP), FAA Technical Center, U.S. Weather Research Program, and the City of Denver. The RAL Winter Weather team is led by R. Rasmussen; F. Hage, S. Landolt, M. Tryhane, J. Cole, E. Brandes and K. Ikeda are members of the team.
Current Activities and Accomplishments
Weather Support to Deicing Decision Making (WSDDM) System Enhancements
Two new capabilities have been added to the WSDDM system this year:
- Freezing drizzle: In response to B737 jet engine damage at Denver and Oslo, Norway, due to the ingest of freezing drizzle of moderate or greater rate, RAL scientists have developed a new method of detecting and warning of freezing drizzle conditions. The old approach which used current METAR observations of freezing drizzle typically underestimated the drizzle rate due to the fact that drizzle intensity was determined by visibility. Since drizzle size distributions can vary widely, so can the visibility and the estimated rate. The new freezing drizzle detection system developed by Rasmussen, Hage, Landolt, Cole, Oien, and Tryhane uses a Goodrich freezing rain sensor and an NWS freezing drizzle detection algorithm developed by Allan Ramsay. The output of this system is then displayed on the WSDDM system as a graphical strip chart (Figure xx). This product was demonstrated at Denver International Airport in 2005. United Airlines was able to avert engine damage during eight drizzle events during the winter, resulting in significant cost savings.
- Checktime System: Aircraft deicing personnel have long needed a reliable way to determine in real-time how long aircraft can be "held over" once they have been deiced. A new method for calculating holdover time has been developed at RAL based on liquid equivalent snowfall rates and temperature data that are updated every minute. This "checktime" system provides a real-time estimation of when deicing fluids applied to an aircraft fail. By knowing when an aircraft was deiced, checktime can be applied to all aircraft on the field that have been deiced. If the aircraft time of deicing (wall clock time) is before the wall clock checktime, then the aircraft is within the holdover time for the specific fluid it is using. If the aircraft time of deicing is after the wall clock checktime, then the aircraft has exceeded its holdover time and needs to get “checked”. During the winter of 2005