- Количество слайдов: 22
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 (Vaisala (HSS) PWD-22) Liquid Water Equivalent System Components WXT temperature, humidity, and wind sensor (Vaisala) Hotplate (Yankee) Weighing Snowgauge (GEONOR) Freezing Rain sensor (Campbell)
Chicago Instrumentation Location LWE site ASOS site X
LWE Display Demo
Wind Enhancement of LWE due to 10 degree angle of a wing Marshall Field Site testing FY 08 List the dates that obtained data for including the number of hours: Date Thank you Hours of data Nov. 11, 2007 6 Dec. 20 2007 5 Total hours: 144 Based on paper in Journal of Aircraft: “Common Snowfall Conditions Associated with Aircraft Takeoff Accidents”, Rasmussen et al. (2000)
Wind Enhancement of LWE due to 10 degree angle of wing: 10º pan compared to 0º pan using error rejection criteria Marshall Field Site testing FY 08 List the dates that obtained data for including the number of hours: Factor of 1. 8 larger snow catch on a 10 Date Thank you Hours of data degree surface Nov. 11, 2007 6 Insert image of snow pa for a wind Dec. 20 2007 5 speed of 6 m/s Total hours: 144 Based on paper in Journal of Aircraft: “Common Snowfall Conditions Associated with Aircraft Takeoff Accidents”, Rasmussen et al. (2000)
Snow rate Wind enhanced rate Raw precipitation rate
Online Cleveland LWE display URL http: //www. rap. ucar. edu/projects/winter/CLE
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
Radio Message § At 1630 local, temperature -3 C, 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 (2008 -2009) - Ice pellets (2009 -2010) 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 – http: //www. rap. ucar. edu/projects/winter/ORD