Advisory Circulars (ACs)
An advisory circular is just as it sounds. It is some material that is delivered to the aviation community, which is advisory in nature. ACs are issued by the FAA for a number of reasons. They may provide clarification on how regulation is meant to be complied with, resolve some misunderstanding concerning regulation, or expand on standards needed to promote aviation safety, for example.
An AC is identified by a three part number, according to a defined AC numbering system. The first part of the number relates to the part of regulation addressed. The most relevant are:
The second part of the AC number is sequential within each subject area, and the third part of the AC's number shows the revision status of this particular AC. So, "AC 25-42C" relates to aircraft and this is the third revision of this particular AC.
Advisory circulars may be ordered from the Superintendent of Documents, U.S. Government Printing Office, and are also available at the FAA's website at:
http://www.faa.gov/regulations_policies/advisory_circulars/
Notices to Airmen (NOTAMs)
When aeronautical information is temporary or not included on charts and publications because of the recency of its occurrence, a notice to airmen, or NOTAM is issued. NOTAMs are considered essential to flight safety, and are divided into two categories: Distant and Flight Data Center.
Notam D's are disseminated for all navigational facilities that are part of the national airspace system, all public use airports, seaplane bases, and heliports listed in the Airport/Facilities Directory. Information such as taxiway and runway closures, navigation aid outages, airport lighting status, etc., are disseminated as Notam D's. Notam D's are obtained during a preflight weather briefing, but are also available from air traffic control.
FDC Notams contain items such as amendments to charts and procedures that were not developed in time for inclusion on the appropriate publication. FDC Notams are also issued for large scale public events that may generate air congestion which justifies the use of a temporary flight restriction. FDC Notams are available in printed form from the FAA or are available online at the following web address:
https://pilotweb.nas.faa.gov/PilotWeb/
FDC Notams are not given by default during a standard preflight weather briefing from the flight service station. They are available upon request, however, by asking the FSS specialist to read you any applicable FDC Notams.
Temporary Flight Restrictions (TFRs)
Temporary flight restrictions are sometimes used to limit or prohibit flight operations in a defined area for a certain period of time. These restrictions are put in place to protect persons in the air or ground from some hazard, provide a safe environment for the operation of disaster relief aircraft, prevent unsafe congestion of sightseeing aircraft above some incident or event of public interest, or protect VIP movement (president or other public figures). The down range areas for space vehicle launches are protected with the use of temporary flight restrictions, as well.
The use of temporary flight restrictions has increased, due to the terrorist activities of 2001. In recent times, the number of pilot certificate suspensions due to TFR incursions has increased, as well. Prior to your flight, visit the FAA's web site to verify your flight will not be affected by a TFR. TFR information is available on the FAA website at the following address: