Aviation Speak

Airspeed

Airspeed may seem a straightforward term, but there are several types, and pilots often fail to distinguish which type they mean. The simplest definition is the speed of an aircraft relative to its surrounding air mass. If a pilot or air traffic controller refers to airspeed but does not say what type of airspeed, the assumption is that he or she is referring to indicated airspeed. This is simply the figure shown on the aircraft's airspeed indicator.

Another important type of airspeed is true airspeed, sometimes written as TAS. True airspeed refers to the airspeed of an aircraft relative to undisturbed air. Being able to calculate true airspeed is critical in flight planning for figuring out how much fuel will be needed to make a trip. When pilots or air traffic controllers are speaking about true airspeed, they need to refer to just that and should not shorten the term to the more generic airspeed.

Calibrated airspeed is a third type of airspeed, but one that you probably won't use often. It is indicated airspeed corrected for position, instrument error, and temperature. At standard atmospheric conditions at sea level, calibrated airspeed equals true airspeed.

EFAS/Flight Watch

EFAS stands for en route flight advisory service. EFAS is a service specially designed to provide pilots with timely weather information pertinent to the type of flight, aircraft, intended route, and altitude.

Not every flight service station provides this information, and the pilot must specifically request it. Pilots typically use the term flight watch when making radio calls to request EFAS. For instance, a pilot trying to reach the Oakland flight service station would radio on 122.0 MHz with the words, "Oakland flight watch." After receiving a response, the pilot could state his request. It's important to remember that this service is only available between 6 a.m. and 10 p.m.

Notam-Notice to Airmen

This familiar acronym stands for notice to airmen. Notams are announcements containing information that is essential to flight operations and is either temporary or not known far enough in advance to be published in other forms. Notams may cover regulations or systems; changes in airspace, facilities, services, or procedures; or hazards to flight.

You can generally get notams that apply to your flight from flight service when you call for a weather briefing. Local notams, such as those announcing a runway closure or the unavailability of a navigational aid, are sometimes also included in ATIS (automated terminal information service) broadcasts.

Notams are divided into several classifications based on how widely they are distributed and what means are used to distribute the information. The categories include notam (D), notam (L), and FDC notam. A notam (D) is a notice that, in addition to local dissemination, is disseminated at a distance beyond the local flight service station's area of responsibility. Notams of this type are stored and are available to pilots until they are cancelled.

A notam (L) is disseminated only locally, typically by voice or telephone. The distribution method is determined by the needs of the local community.

An FDC notam is issued by the National Flight Data Center in Washington, D.C., and is regulatory in nature. These notams include changes to instrument approach procedures and temporary flight restrictions. Flight service stations maintain files of current FDC notams that apply within 400 miles of their location. Many flight service stations have access to all FDC notams, but you must request them.