AIM
4/3/14
4−3−28
Airport Operations
FIG 4
−3−22
Stop
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 Air-
space 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 Airport/Facility Directory.
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 effect 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
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AIM, Weather Observing Programs, Paragraph 7