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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


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.


“I have the (airport) one−minute weather, request an ILS

Runway 14 approach.”


AIM, Paragraph 7−1−12 , Weather Observing Programs


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