Maintenance Manual________________________________________________________________
28 __________________________________________________________________ M210886EN-G
Sensors
The AviMet LLWAS system is based on wind sensor sites located around
the approach and departure corridors of an airport. Each sensor site
includes a wind speed and a wind direction sensor. The standard
configuration for phase III algorithm requires an array of 12 sensors, but
the number of sensors included in the array may be anything from 10 to 52.
The data from the sensors is usually collected with a data collector and
transmitted to the CDU via a serial line. Data is retrieved from the sensor
sites either via a direct cable connection or a radio link. There are three
methods of operating the sensors: normal, cascade, or forward polling
method:
- In the normal polling method a separate poll request is sent to each
sensor site and the sensor sites answer immediately.
- In the cascade polling method only one poll request is sent and the
sensor sites answer with given time intervals.
- In the forward polling method a poll request and the response can be
relayed by another sensor site if a sensor site is behind an obstruction
that blocks radio transmission.
Data Collector
In small airports, AviMet sensor sites can be directly connected to the
CDU. In large airports, the use of one or more intermediate data collectors
provides a convenient way to connect a large number of sensors to the
CDU. The data collector can be, for example, an automated weather
station, such as MILOS 520.
Central Data Unit (CDU)
The central data unit (CDU) gathers data from sensors, calculates and
checks weather parameters, rounds some of the values, and converts them
to appropriate measurement units. After that, the CDU transmits the data
to the user workstations.
CDU Hardware Components
The CDU computer includes a set of hardware components including a
high-performance processor and enough memory and disk space. The
exact size and amount depend on the requirements of the specific system
delivered.
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