Aero-Tips!

A good pilot is always learning -- how many times have you heard this old standard throughout your flying career? There is no truer statement in all of flying (well, with the possible exception of "there are no old, bold pilots.") It's part of what makes aviation so exciting for all of us... just when you think you've seen it all, along comes a scenario you've never imagined.

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Aero-Tips 02.19.06

AWOS provides potentially vital information about weather in the vicinity of airports.  What’s information is available?  What are the system’s limitations?

AWOS

The Automated Weather Observation System (AWOS) provides weather observations 24 hours a day without human involvement. AWOS reports wind, ceiling, visibility, temperature, dew point, altimeter setting, and any recorded remarks such as Notices to Aviators (NOTAMs). AWOS is a “modular” system with several upgrade options available, reporting:

• AWOS A:  Altimeter setting.
• AWOS I:  Altimeter setting plus wind speed, direction and gusts, temperature, dew point, and density altitude.
• AWOS II:  AWOS I plus visibility and precipitation.
• AWOS III:  AWOS II plus cloud height and sky condition.
• AWOS IIIP:  AWOS III plus present (prevailing) weather.
• AWOS IIIPT:  AWOS IIIP plus lightning detection.
• AWOS IIIPTZ:  AWOS IIIPT plus freezing rain detection.
• AWOS IV: AWOS IIIPTZ plus a Runway Surface Condition Sensor.

Since many AWOS units are privately or state-owned, options (and reported information) vary.  See the Airport Facilities Directory for the type used at your destination.

Advantages of AWOS:

• Objective observation to 10,000 feet AGL within 25 miles of the reporting point
• 24-hour availability
• Near-real-time updating
• Data added to the Flight Service briefing and forecasting network
• Radio and telephone access for pilots
• Permits FAR 135 approaches at non-towered airports (note: most charter and airline Ops specs require airport weather reporting to begin an instrument approach)

Disadvantages of AWOS

• Many AWOS installation options report limited information
• Averages some weather data
• Detects clouds only straight up from, and visibility in immediate vicinity of, the sensors
• Omits reporting of some transient weather, e.g., variable cloud ceilings
• Terrain or other local features may limit observations
• No human oversight of reported data (in most cases)

Aero-tip of the day: Anticipate the weather information available at your destination airport, and the limitations on AWOS reports.

FMI: Aero-Tips