LWE and Checktime Demo Scott Landolt & Steve Cristanelli - NCAR October 27, 2009

What is LWE, Checktime and WSDDM? LWE – Liquid Water Equivalent Checktime – Automated Holdover Time (HOT) Algorithm WSDDM – Weather System for De-icing Decision Making

Why use LWE?

Precipitation Type sensor (HSS) WXT temperature, humidity, and wind sensor (Vaisala) Hotplate (Yankee) Weighing Snowgauge (GEONOR) Liquid Water Equivalent System Components Precipitation Type sensor (Vaisala PWD-22) Freezing Rain sensor (Campbell)

Chicago Instrumentation Location X ASOS site LWE site

LWE Display Demo

Marshall Field Site testing FY08 List the dates that obtained data for including the number of hours: DateHours of data Nov. 11, Dec Total hours: 144 Thank you Wind Enhancement of LWE due to 10 degree angle of a wing Based on paper in Journal of Aircraft: “Common Snowfall Conditions Associated with Aircraft Takeoff Accidents”,Rasmussen et al. (2000)

Marshall Field Site testing FY08 List the dates that obtained data for including the number of hours: DateHours of data Nov. 11, Dec Total hours: 144 Insert image of snow pans Thank you Wind Enhancement of LWE due to 10 degree angle of wing: 10º pan compared to 0º pan using error rejection criteria Based on paper in Journal of Aircraft: “Common Snowfall Conditions Associated with Aircraft Takeoff Accidents”,Rasmussen et al. (2000) Factor of 1.8 larger snow catch on a 10 degree surface for a wind speed of 6 m/s

Snow rate Wind enhanced rate Raw precipitation rate

Online Cleveland LWE display URL

How does LWE relate to Checktime?

Inputs to Check Time: 1. Precipitation rate (every minute) enhanced by wind (10 degree effect) 2. Wind speed (every minute) 3. Temperature (every minute) 4. Precipitation type (every minute) 5. Fluid type and concentration 6. Regression equations that relate holdover time to precipitation rate and ambient temperature (from APS report) Output: Fluid Expiration time every minute (wall clock time, or Check Time) for given fluid type and concentration

Checktime Display

Radio Message  At 1630 local, temperature -3C, Light Snow, Checktime for Type IV Kilfrost ABC-S Plus is 16:50

Impact of Time Variation of Precipitation Rate, Temperature, and Wind Speed on Holdover Time  Data from Denver, Chicago and Pittsburgh all showed that time variation of precipitation has a significant effect on Holdover Time – On average, 50% of the Instantaneous HOTs longer than Check Time HOTs. – 15% of the Instantaneous HOTs a factor of 1.25 longer than Check Time HOTs (a potential safety issue). – 5% of the Instantaneous HOTs a factor of 1.5 long than Check Time HOTs

2008/2009 User Feedback  Denver –LWE rates found to accurately reflect operational experience:  Example: LWE system reporting of heavy snow during the April 17 th event confirmed due to the repeated deicing of 757 aircraft (4 times), and return for deicing a fifth time. –Found the precipitation type reporting on LWE to be useful. –Tend to use Check Time over LWE system due to the direct reporting of current Holdover time (expiration time) and more accurate HOT (than instantaneous). – Used the Check Time system to determine when to transition from Type I only to two step Type I and Type IV operation

Current Status User feedback positive with regard to the useability and usefulness of the snow LWE. More feedback desired, however. Users asking to use the systems operationally. Before can, however, need the FAA to approve. Remaining Issues: 1. Communication to the pilot - Majority of users prefer message via radio frequency. - Radio frequencies hard to get at airports. - Display on the web. - Product on a Blackberry 2. Approval of LWE snow system for operational use. FAA working on. 3. Expansion to include other precipitation types - Freezing rain and drizzle ( ) - Ice pellets ( ) 4. Approval of Check Time system for operational use.

Survey  ATIS – Current time is _____ –Visibility __________ –Temperature ______  Current System HOT –Snow Intensity Chart ________ –HOT _________

Survey  LWE (Radio Frequency) –Temperature _______ –Intensity __________ –HOT (Volume 1 holdover chart) ______  Checktime (Radio Frequency) –Start time of Type IV ________ –Checktime _________ –As close to runway as possible, new checktime ______, Current time ______

Survey  Did you have to return for De-icing? –If yes, answer these questions  Did the time expire? _____  Was the fluid contaminated? _____  Preemptive? _____  Additional training and/or feedback can be found at Additional training and/or feedback can be found at Additional training and/or feedback can be found at –

WSDDM