aim-218

AIM

8/15/19

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Airport Operations

FIG 4

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Stop

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26. Operations at Uncontrolled

Airports With Automated Surface
Observing System (ASOS)/Automated
Weather Observing System (AWOS)

Many airports throughout the National

Airspace System are equipped with either ASOS or
AWOS. At most airports with an operating control
tower or human observer, the weather will be
available to you in an Aviation Routine Weather
Report (METAR) hourly or special observation
format on the Automatic Terminal Information
Service (ATIS) or directly transmitted from the
controller/observer.

At uncontrolled airports that are equipped with

ASOS/AWOS with ground

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air broadcast capabil-

ity, the one

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minute updated airport weather should be

available to you within approximately 25 NM of the
airport below 10,000 feet. The frequency for the
weather broadcast will be published on sectional
charts and in the Chart Supplement U.S. Some
part

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time towered airports may also broadcast the

automated weather on their ATIS frequency during
the hours that the tower is closed.

Controllers issue SVFR or IFR clearances

based on pilot request, known traffic and reported
weather, i.e., METAR/Nonroutine (Special) Aviation
Weather Report (SPECI) observations, when they are
available. Pilots have access to more current weather
at uncontrolled ASOS/AWOS airports than do the
controllers who may be located several miles away.
Controllers will rely on the pilot to determine the
current airport weather from the ASOS/AWOS. All
aircraft arriving or departing an ASOS/AWOS
equipped uncontrolled airport should monitor the
airport weather frequency to ascertain the status of
the airspace. Pilots in Class E airspace must be alert
for changing weather conditions which may affect the
status of the airspace from IFR/VFR. If ATC service
is required for IFR/SVFR approach/departure or
requested for VFR service, the pilot should advise the
controller that he/she has received the one

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minute

weather and state his/her intentions.

EXAMPLE

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“I have the (airport) one

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minute weather, request an ILS

Runway 14 approach.”

REFERENCE

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AIM, Paragraph 7

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12 , Weather Observing Programs