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AIM

10/12/17

4

−3−32

Airport Operations

4

−3−26. Operations at Uncontrolled

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

a.

Many airports throughout the National

Airspace System are equipped with either ASOS,
AWSS, 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.

b.

At uncontrolled airports that are equipped with

ASOS/AWSS/AWOS with ground

−to−air broadcast

capability, the one

−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

−time towered airports may also broadcast

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

c.

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/AWSS/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/AWSS/
AWOS. All aircraft arriving or departing an
ASOS/AWSS/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

−minute weather and state

his/her intentions.

EXAMPLE

“I have the (airport) one

−minute weather, request an ILS

Runway 14 approach.”

REFERENCE

AIM, Paragraph 7

−1−12 , Weather Observing Programs

3/15/07

7110.65R CHG 2

AIM

3/29/18