AWOS-C and SWS
Lesson 2
1

Introduction & NAS Facilities

Lesson Introduction

NAS Facilities

The National Airspace (NAS) is an aviation system consisting of the:

  • Actual airspace above us
  • Network of navigation facilities and airports across the United States, each with its own rules and regulations
  • Facilities within the NAS which use various sensors and equipment to keep aircraft flying safely

The NAS uses several weather-observation systems such as Automated Weather Observing System (AWOS-C) and SWS (Surface Weather System) to gather the most accurate possible data.

Weather stations can be located at manned or unmanned locations.

2

AWOS-C Overview

AWOS-C (Automated Weather Observing System)

The AWOS-C (Automated Weather Observing System):

  • is a stand-alone, 24 hour, weather detecting device
  • contains sub-sensors that measure meteorological elements to produce weather products for:
    • local airports
    • Air Route Traffic Control Centers (ARTCCs)
    • Terminal Radar Approach Controls (TRACONs)
    • other FAA and select non-FAA customers (National Weather Service, airlines, etc.).

The AWOS-C is able to produce different report types:

  • Meteorological Aviation Routine Weather Report (METAR)
  • SPECIAL Weather Statement (SPECI)
  • Monthly Summary Message (MSM), Daily Summary Message (DSM)
  • and One Minute Observations (OMOs) sent and disseminated throughout the network of various users.

These reports are delivered to customers, who include:

  • FAA’s Air Traffic Control Tower (ATCT)
  • National Enterprise Management Centers (NEMCs)
  • ARTCCs
  • TRACONs
  • National Weather Service (NWS)
  • Commercial and private airlines.

3 Major Components of the AWOS-C

The Data Collection Platform (DCP) collects airfield sensor information and sends 5-second raw data to the CDP. It is composed of:

The Airfield Sensors generate the data for the DCP. They will be covered in greater detail in the next section.

The purpose of the Central Data Platform (CDP) is to provide weather information to users of the AWOS-C system. DCP collects airfield sensor information and sends 5-second raw data to the CDP. The CDP then applies Government Furnished Algorithms (GFA) to the data and sends the calculated values to be broadcast via VHF radio or the ADAS digital data-link as weather observations. This will be covered in further detail later in the lesson.

3

Airfield Sensors

Airfield Sensor Group

The Ultrasonic Wind Sensor is polled by the DCP.

The Temperature and Relative Humidity Probes are components within the MARS sensor.

The Barometric Pressure Sensor (BP) is located inside the DCP. It has three transducers inside and interfaces directly with the DCP processor.

The Rain Gauge measures precipitation amounts and includes a thermostat that regulates the rate of snow melt.

The Visibility/Present Weather sensor will report types of visibility restrictions (haze, fog, smoke, etc.), and precipitation types (hail, sleet, snow, rain, mist, etc.).

The Ceilometer is the cloud height indicator which reports up to 3 layers of cloud coverage.

The Freezing Rain Sensor is an optional device that detects ice accumulation by monitoring the resonant frequency of a vibrating magnetostrictive metal tube.

Uninterruptible Power Supply (UPS) is an optional device to be co-located with the DCP and Airfield Sensors Group.

The Airfield Sensor Group consists of the following:

  1. Ultrasonic Wind Sensor
  2. Temperature and Relative Humidity Probes
  3. Barometric Pressor Sensor
  4. Rain Gauge
  5. Visibility/Present Weather Sensor
  6. Ceilometer
  7. Freezing Rain sensor
  8. UPS

Click the components in the graphic to learn more about them. Once you have read the required information, scroll down to proceed.

4

AWOS-C Inputs and Products

Inputs and Products

Weather Elements Gathered
Measurable weather elements may not be sent out as the same product.

Example: Atmospheric pressure is measured by a barometer, but our finalized product is the altimeter setting. Both are an expression of pressure and use inHg as the unit of measurement. Other sensors may gather data, but the finalized product is different.

The table below provides a list of sensors to which data criteria shown before the Government Furnished Algorithms (GFA) are applied.

Weather Products Produced by AWOS-C
The weather products gathered by the AWOS-C are collected at the DCP before being sent to the CDP where GFAs are applied to produce the advertised services.

Note: Wind direction reports as TRUE North over ADAS Data-Link, while local audio broadcast reports as MAGNETIC North.

5

NAS Infrastructure Layout

Diagram

The diagram on the right depicts the NAS infrastructure and shows key components that affect data dissemination of the AWOS-C’s various types of reports.

The black text in blue boxes show the report types, while the green text shows lightning data. The dashed green line shows important lightning data that is processed to AWOS-C, while the un-dashed green lines demonstrate data that is unimportant to (and not processed by) AWOS-C.

Knowledge Check

1

Which component(s) are responsible for collecting data for the AWOS-C?

Select all answers that apply. Then, click Submit.

A
Central Data Platform
B
Data Collection Platform
C
Airfield Sensor Group
D
Government Furnished Algorithms
2

The Data Collection Platform (DCP) collects airfield sensor information and sends ______ to the CDP.

Select the answer below. Then, click Submit.

A
GFA data
B
5-second raw data
C
2-second raw data
D
Raw data
6

SWS Overview

Surface Weather System Overview

SWS (Surface Weather System) is a stand-alone, 24-hour, weather-detecting device. The system’s sensors measure meteorological elements to produce weather products for the FAA including:

  • Air Route Traffic Control Centers (ARTCCs)
  • Terminal Radar Approach Controls (TRACONs)
  • Air Traffic Control Towers (ATCTs)

The SWS works in conjunction with other weather-observation systems currently used by NAS and provides basic weather data in the NAS ARTCCs, TRACONs, and ATCTs.

The SWS feeds data to:

  • Multiple TRACON displays
  • Ribbon Display Terminal (RDT)
  • Digital Display Panel (DDP)
  • SWS sites with single or multiple wind sensor sites

The SWS is composed of airfield sensors that send data to the DCP.

The DCP sends a combined stream of sensor data to the CDP, where the information can be monitored, processed into a final product, and given to the user.

7

End of Lesson Review

Knowledge Check

3

Which airfield sensors are polled by the DCP in the SWS?

Select all answers that apply below. Then, click Submit.

A
Barometric Pressure Sensor
B
MARS
C
Present Weather Sensor
D
Ultrasonic Wind Sensor

Course Summary and Closing Audio