AIM 4-3-27

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-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. Some part-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-minute weather and state his/her intentions. EXAMPLE-

“I have the (airport) one-minute weather, request an ILS Runway 14 approach.”

REFERENCE-

AIM, Para 7-1-10 , Weather Observing Programs.

Previous | Top | Next AIM |

ATPUBS |

FAA |

Send your comments regarding this website.

Chapter 4. Air Traffic Control AIM

AIM by Chapter Number Chapter 0. General Information Chapter 1. Air Navigation Chapter 2. Aeronautical Lighting and Other Airport Visual Aids Chapter 3. Airspace Chapter 4. Air Traffic Control Chapter 5. Air Traffic Procedures Chapter 6. Emergency Procedures Chapter 7. Safety of Flight Chapter 8. Medical Facts for Pilots Chapter 9. Aeronautical Charts and Related Publications Chapter 10. Helicopter Operations Chapter 11. Unmanned Aircraft Systems (UAS) Appendix 1 Appendix 2 Appendix 3 Appendix 4 Appendix 5

ATPUBS

AIM by Topic

General Information Explanation of Changes

Air Navigation Navigation Aids

Performance-Based Navigation (PBN) and Area Navigation (RNAV)

Aeronautical Lighting and Other Airport Visual Aids Airport Lighting Aids

Air Navigation and Obstruction Lighting

Airport Marking Aids and Signs

Airspace General

Controlled Airspace

Class G Airspace

Special Use Airspace

Other Airspace Areas

Air Traffic Control Services Available to Pilots

Radio Communications Phraseology and Techniques

Airport Operations

ATC Clearances and Aircraft Separation

Surveillance Systems

Operational Policy/Procedures for Reduced Vertical Separation Minimum (RVSM) in the Domestic U.S., Alaska, Offshore Airspace and the San Juan FIR

Operational Policy/Procedures for the Gulf of America 50 NM Lateral Separation Initiative

Air Traffic Procedures Preflight

Departure Procedures

En Route Procedures

Arrival Procedures

Pilot/Controller Roles and Responsibilities

National Security and Interception Procedures

Emergency Procedures General

Emergency Services Available to Pilots

Distress and Urgency Procedures

Two‐way Radio Communications Failure

Aircraft Rescue and Fire Fighting Communications

Safety of Flight Meteorology

Barometric Altimeter Errors and Setting Procedures

Cold Temperature Barometric Altimeter Errors, Setting Procedures and Cold Temperature Airports (CTA)

Wake Turbulence

Bird Hazards and Flight Over National Refuges, Parks, and Forests

Potential Flight Hazards

Safety, Accident, and Hazard Reports

Medical Facts for Pilots Fitness for Flight

Aeronautical Charts and Related Publications Types of Charts Available

Helicopter Operations Helicopter IFR Operations

Special Operations

Unmanned Aircraft Systems (UAS) General

Small Unmanned Aircraft System (sUAS)

Large UAS (MGOW 55 Pounds or More)

Airspace Access for UAS

UAS Pilot Testing, Certification and Responsibilities

Advanced Air Mobility

UAS Operations on Airports

Other Information and Best Practices

Appendix 1

Appendix 2

Appendix 3

Appendix 4

Appendix 5

Air Traffic Control

ATC Clearances and Aircraft Separation

Chapter 4. Air Traffic Control

Section 4. ATC Clearances and Aircraft Separation