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A Notice to Airmen (NOTAM or NoTAM) is a notice filed with an aviation authority to alert aircraft pilots of potential hazards along a flight route or at a location that could affect the safety of the flight. NOTAMs are created and transmitted by government agencies and airport operators under guidelines specified by Annex 15: Aeronautical Information Services of the Convention on International Civil Aviation (CICA). The term NOTAM came into common use rather than the more formal Notice to Airmen following the ratification of the CICA, which came into effect on 4 April 1947. Notices to Airmen were normally published in a regular publication by each country's air authorities (e.g., in Flight Magazine in the UK). A number of developments and amendments to the CICA have resulted in the more automated system available today.
A NOTAM is filed with an aviation authority to alert aircraft pilots of any hazards en route or at a specific location. The authority in turn provides a means of disseminating relevant NOTAMs to pilots.
NOTAMs are issued (and reported) for a number of reasons, such as:
- hazards such as air-shows, parachute jumps, kite flying, rocket launches, etc.
- flights by important people such as heads of state (sometimes referred to as temporary flight restrictions, TFRs)
- closed runways
- inoperable radio navigational aids
- military exercises with resulting airspace restrictions
- inoperable lights on tall obstructions
- temporary erection of obstacles near airfields (e.g., cranes)
- passage of flocks of birds through airspace (a NOTAM in this category is known as a BIRDTAM)
- notifications of runway/taxiway/apron status with respect to snow, ice, and standing water (a SNOWTAM)
- notification of an operationally significant change in volcanic ash or other dust contamination (an ASHTAM)
- software code risk announcements with associated patches to reduce specific vulnerabilities
Aviation authorities typically exchange NOTAMs over AFTN circuits.
Software is available to allow pilots to identify NOTAMs near their intended route or at the intended destination.
In the U.S. Air Force information technology enterprise, C4 NOTAMs (Command, Control, Communications, and Computer Notices to Airmen) are notices of new or updated Air Force Network Operating Instructions (AFNOIs). Often, these notices serve to direct Air Force computer administrators to install security updates or change the configuration of computer systems.
In joint task forcesNOTAMs is the common term for "Notice to All Members".
The following describes ICAO NOTAMs. NOTAMs are published using all upper case letters which are claimed by some to make NOTAMs difficult to read. Note that some countries such as the United States may diverge from the following ICAO standards.
- The first line contains NOTAM identification (series, sequence number, and year of issue), the type of operation (NEW, REPLACE, or CANCEL), as well as a reference to a previously-issued NOTAM (for NOTAMR and NOTAMC only).
- The "Q" line holds (basic-remove) information about who the NOTAM affects along with a basic NOTAM description. This line can be encoded/decoded from tables defined by ICAO. This allows NOTAMs to be displayed electronically
- The "A" line is the ICAO code of the affected aerodrome or FIR for the NOTAM. The area of influence of the NOTAM can be several hundreds of kilometres away from the originating aerodrome.
- The "B" line contains the start time and date, the "C" line the finish time and date of the NOTAM. The date is in the format YY/MM/DD and the times are given in Universal Co-ordinated Time; also known as GMT or Zulu time.
- Sometimes a "D" line may be present. This gives a miscellaneous diurnal time for the NOTAM if the hours of effect are less than 24 hours a day, e.g., parachute dropping exercises tend to occur for short periods of a few hours during the day, but may be repeated over many days.
- The "E" line is the full NOTAM description. It is in English but heavily abbreviated. These abbreviations can be encoded/decoded by tables defined by ICAO.
- When present, "F" and "G" lines detail the height restrictions of the NOTAM. Typically SFC means surface height or ground level and UNL is unlimited height. Other heights are given in feet or flight level or a combination of the two.
This is a typical NOTAM for London Heathrow airport:
- A1234/06 NOTAMR A1212/06
- E)DUE WIP TWY B SOUTH CLSD BTN 'F' AND 'R'. TWY 'R' CLSD BTN 'A' AND 'B' AND DIVERTED VIA NEW GREEN CL AND BLUE EDGE LGT. CTN ADZ
This decodes into the following:
- SERIES and NUMBER : A1234 issued in 2006
- NATURE OF THE NOTAM : Replacing NOTAM 1212 issued in 2006
- FIR: EGTT (LONDON FIR)
- SUBJECT: Taxiway (MX)
- CONDITION: Closed (LC)
- TRAFFIC: NOTAM issued for IFR (I) flights and VFR flights (V)
- PURPOSE: NOTAM selected for immediate attention of flight crew members (N)
- PURPOSE: NOTAM selected for PIB entry (B)
- PURPOSE: NOTAM concerning flight operations (O)
- SCOPE: Aerodrome
- GEOGRAPHICAL LOCATION : 51°29' N 000° 28' W
- OPERATIONAL RADIUS OF THE NOTAM : 5 NM
- AERODROME : London Heathrow (EGLL)
- FROM: 05:00 UTC 5 September 2006
- UNTIL:05:00 UTC 30 April 2007
- CATEGORY: Aerodromes, Air Routes, and Ground Aids
- DESCRIPTION: Due to work in progress, taxiway "B South" is closed between "F" and "R". Taxiway "R" is closed between "A" and "B" and is diverted via a new green centre line and blue edge lighting. Caution advised.
U.S. domestic NOTAMs 
In United States, NOTAMs are classified by the FAA into five categories:
- NOTAM (D) or distant NOTAMs
- A NOTAM (D) information is disseminated for all navigational facilities that are part of the National Airspace System (NAS), all public use airports, seaplane bases, and heliports listed in the Airport/Facility Directory (A/FD) (e.g., such information as whether or not an airport or a certain facility is usable). NOTAM (D) information includes, among other topics, such data as taxiway closures, personnel and equipment near or crossing runways, and airport lighting aids that do not affect instrument approach criteria, such as VASI.
- Flight Data Center (FDC) NOTAMs
- The National Flight Data Center will issue these NOTAMs when it becomes necessary to disseminate information that is regulatory in nature, and they contain such things as amendments to published IAPs and other current aeronautical charts. They are also used to advertise temporary flight restrictions caused by such things as natural disasters or large-scale public events that may generate congestion of air traffic over a site.
- Pointer NOTAMs
- NOTAMs issued by a flight service station to highlight or point out another NOTAM, such as an FDC or NOTAM (D) NOTAM. This type of NOTAM will assist users in cross-referencing important information that may not be found under an airport or NAVAID identifier.
- Special use airspace (SUA) NOTAMs
- SUA NOTAMs are issued when SUA will be active outside the published schedule times and when required by the published schedule.
- Military NOTAMs
- NOTAMs pertaining to U.S. Air Force, Army, Marine, and Navy navigational aids/airports that are part of the NAS.
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