Aviation Topic of the Week
By Michael Oxner, April 4, 2004

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This week's topic:
Understanding NOTAMs, Part 1

NOTAMs are important for pilots and are also important for ATC. Understanding how to read them is paramount, since just getting the NOTAMs is not enough. This week, we'll look at some background information on what NOTAMs are, and next week, we'll take a look at NOTAM coding.

When NOTAMs are Issued
NOTAM Summaries
Dissemination of NOTAMs


A NOTAM is a NOTice to AirMen. Not meant to sound sexist or anything, it's just another one of those terms. They are issued to cover a number of items, such as changes to normal operating procedures at a facility, changes in conditions at an airport that are significant, alterations to published approaches (including revoking approach procedures and such), known hazards that are not charted and so on.

They are issued by teletype to any facility connected to the AFTN, or Aeronautical Fixed Telecommunication Network, and also by Voice Advisory. See below for more on obtaining NOTAMs.

When NOTAMs are Issued

The AIP MAP 5.4 is the best reference for this section. It contains details on when NOTAMs are issued and for what reasons. Here is a summary of reasons why NOTAMs may be issued, but it isn't limited to items in this list. This list is taken directly from the quoted section of the AIP and placed in a table to give some examples.

Reason for Issuance
The establishment or withdrawal of electronic and other aids to air navigation and aerodromes
New VOR added to charts, NDB removed, Fix name changed, added or removed, etc.
Changes in frequency, identification, orientation and location of electronic aids to navigation
There have been many NDB changes recently. Across the country, single-letter NDBs serving as approach aids were recently renamed to provide clarity for FMS systems, since many airports across the country were served by the NDBs with the same single-letter name. All of these sorts of changes could result in NOTAMs when not coincident with publication dates.
Interruptions in service or reliability, and the return-to-normal operation of en route and terminal aids to navigation
When NAVAIDs fail, are removed from service for maintenance, or just the self-monitoring abilities of the device fail, NOTAMs are issued both about the failure, and when they are returned to normal service.
The establishment or withdrawal of, or significant changes to, designated airspace or air traffic procedures and services
Such things as the establishment of fire hazard areas, temporary procedures and restrictions (for example, in the wake of September 11) and other such items fall into this category.
Significant changes in operations of runways and serviceability of associated approach or runway lighting systems that could prohibit or limit aircraft activities
Airfield lighting failures can halt night-time operation, or limit the ability for aircraft to see the runway in IFR conditions. Also, construction activities frequently require personnel to work on or near the runways, so instead of closing the runway, the airport authority may close only a portion of it, making the shorter length available.
The presence or removal of hazards that could endanger air navigation or aircraft operations
Temporary obstructions like a crane on a construction site near an airport would be reported. Often, new approach minima for the runways concerned will be published in this manner.
Military exercises or manoeuvres and airspace reservations
The military often uses certain pieces of airspace that are charted. On the charts, the designated areas are often noted as "Mon-Fri, O/T by NOTAM". If this is one of those other times, then a NOTAM will be issued regarding the area.
The establishment or discontinuance of, or change in, the status of Advisory or Restricted Areas
New restricted areas are published by NOTAM to get people's attention so they know about activities which may be dangerous to flight. At the time of writing, the Moncton Flight College is rumored to have applied to get an official status for their training areas. If established, a NOTAM may be issued regarding these areas.
Communication failures where no satisfactory alternate frequency is available
Failure of an FSS's RCO (remote communications outlet) or an ACC's PAL (Peripheral) frequency, for example.
Inaccuracies or omissions in publications that might endanger aircraft operations
Sometimes chart data is issued in error. NOTAMs are issued to correct information on approach or en route charts. The next cycle of publications will normally include information contained in these NOTAMs.
Failure of measuring and/or indicating systems needed to supply current information on altimeter setting, surface wind, RVR and cloud height for the pilot about to land or take-off
Ceilometers (ceiling height), anemometers (wind speed), transimissometers (runway visual range) and barometers (barometric pressure, AKA altimeter setting) are available at many fields, but each of these items are subject to their own failures. Ice storms frequently cover up wind instruments and cause them to fail, for example, which may lead personnel to underestimate winds, causing concern or danger.
Any other information of direct operational significance as recommended in Annex 15 to the Convention on International Civil Aviation
This is the standard catch-all, attempting to cover anything not specifically stated above.

One can see by the length of the list above, and the nature of some of the items mentioned that checking NOTAMs prior to a flight is a very important, even for a local flight.

NOTAM Summaries

NOTAM Summaries are distributed in one of four types in Canada, although it could be said there are technically only two. There is a GENERAL summary, which contains information of general interest to all users, and an FIR Summary, which contains an alphabetical listing of all valid NOTAMs with that FIR. These are available in French and English, and that gives the four different summary types.

These summaries are generated at pre-determined times each day. FIR NOTAM summaries include an alphabetical listing of all NOTAMs applicable to airports and facilities in the FIR. Often there are items that are not associated with a particular aerodrome, but rather are more pertinent to a larger area. These items may be published in the general section of the FIR NOTAM summary. If the item affects a specific aerodrome, it may also be mentioned in the section for the aerodrome later in the summary.

The production times for the summaries are as follows, and are taken from the AIP, MAP 5.5.1:


The General summary is divided into two subsections depending on the originator of the NOTAM:


NOTAM files are four-letter names used for dissemination, storage and retrieval. These files are divided into three categories, as alluded to in a past topic.
  1. National NOTAMs, for items of general interest to anyone in the air. The identifier for these is CYHQ, for Headquarters in Ottawa.
  2. FIR NOTAMs, which are more specific than the National group. These contain more focused items that are applicable to a particular FIR, and include things like Class F airspace, military aircraft movements that are not published in the CFS, airspace restrictions of a temporary nature, ATC or FIC frequency outages, volcanic ash (other weather related items are contained in SIGMETs, a future topic) and so forth. ATC equipment outages may also be listed here, as are enroute navigational facility outages. The codes for these files are the same as the FIR four-letter identifiers for the ACCs in them. CZVR for Vancouver, CZEG for Edmonton, CZWG for Winnipeg, CZYZ for Toronto, CZUL for Montreal, CZQM for Moncton and CZQX for Gander.
  3. Aerodrome NOTAMs. These use the four-letter designators for the aerodromes which they relate to, and these are specific to the aerodrome and related facilities, too. Items affecting the airport and aircraft operations therein would be listed, such as temporary runway changes (like displaced thresholds), lighting unserviceabilities, restrictions on associated approaches due to equipment problems or temporary obstructions, known hazards of a temporary nature, and so forth. For each airport listed in the Canada Flight Supplement and the Water Aerodrome Supplement (the water-based compliment to the CFS) there is an entry in the aerodrome's FLT PLN section to note where the aerodrome's NOTAMs will be found.
Dissemination of NOTAMs

NOTAMs are available in printed form at Flight Service Stations across Canada, and other facilities with teletypes. Fixed Base Operators (FBOs where general aviation parking and services are often found) at airfields will normally have some level of access to such information. They can be obtained by phone calls to local FSS or Flight Information Centers (FICs). In the air, pilot can check with FSS/FIC while enroute by checking in on any frequency designated for provision of Flight information Service Enroute (FISE). For IFR flights, workload permitting, ATC will be able to provide such information as well. Also, Community Aerodrome Radio Stations (CARS) will provide pilots with limited NOTAM information, and this is typically limited to those items directly related to the airport and its facilities.

Some NOTAMs are put out on a Voice Advisory only. A short notice, temporary failure of a NAVAID, for example, might have a voice advisory issued, rather than sending in a NOTAM to put on file. By the time it propagates through the system, such a failure might be over with. The voice advisory is something that would be issued to pilots, normally over the radio, when the information ATC/FSS has about the flight leads them to believe they may be affected. For example, an aircraft flying an airway in which one leg is based on a facility that has temporarily failed would be issued the voice advisory and may be rerouted, if required, at the same time.

Well, there's a start to Understanding NOTAMs. Next week, we'll look at some example NOTAMs and their format and coding. For now, if you have any questions, please e-mail me at moxner@nbnet.nb.ca. Thanks again for taking the time to read!