Vaisala CT25K, User Manual

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2. Product Overview
2.1 System Introduction
Vaisala AviMet â Low-Level Windshear Alert System (LLWAS) is a ground-based low-level
windshear alert system. It provides visual and audio alerts on calculated windshear and
microburst conditions for air traffic controllers and other airport personnel.
The system measures, processes, displays, stores, and distributes meteorological
information. It consists of sensors located along the runway, one or two central data unit
computers (CDUs), and one or several workstations.
The sensors are located along the runways at specific measurement sites and communicate
with the central data units (CDUs), which distribute the data to the workstations. The system
can be single-CDU or duplicated, that is, it can include one or two CDUs. The CDU validates
the measurement data, calculates the values based on the data, and distributes the weather
data and alarms to user workstations.
Vaisala AviMet
â Low-Level Windshear Alert System (LLWAS) consists of wind speed and
wind direction sensors located around the runway area perimeter. The CDU processes the
horizontal wind speed and direction data using the LLWAS III algorithm, developed by NCAR
for the U.S. Federal Aviation Administration (FAA). Windshear and microburst alerts are
provided when the data generated by the system exceeds the airport-specific threshold
values for possible windshear conditions.
In user workstations, users can view weather data, trends, and alerts with the WeatherView
application. Historical values can be viewed in the ASCII Log View application. The
Diagnostics application is for monitoring and handling system error situations.
Figure 1 A Typical Vaisala AviMet System
1 Sensor data
2 Central data units
3 Local area network (LAN)
4 Workstations
Chapter 2 – Product Overview
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