Page 131 - Planning and Design of Airports

100 Airp o r t Pl anning

Flight Service Stations
While not providing specific control, flight service stations (FSS) are the
element of the air traffic management system that provides information
and other noncontrol communications to aircraft operating in the sys-
tem. Their principal functions are to accept and close flight plans, brief
pilots about their routes of flight, and to provide important information,
in the form of notices to airmen (NOTAMs) before flight and in flight,
on such items as severe weather, the status of navigational aids, airport
runway closures, and changes in published approach and departure
procedures. A secondary function is to relay traffic control messages
between aircraft and the appropriate control facility on the ground.
Flight service has gone through a number of changes since the
early 1990s. In the 1990s the FAA consolidated more than 180 flight
service stations into approximately 60 automated flight service sta-
tions (AFSS) which allow many functions, particularly with respect to
disseminating weather and other NOTAMs and the filing of flight
plans to be performed electronically by voicemail or computer.
In 2005, the FAA awarded a contract to operate the AFSS system
to the Lockheed Martin Corporation, representing another step in the
privatization of major components of the nation’s air traffic control
system. While the privatization of the AFSS system has caused some
controversy within the aviation industry, there has been relatively
little impact of this or any other FAA privatization efforts on airport
planning and design.

Air Traffic Management Rules
Air traffic rules are traditionally applied based on prevailing meteo-
rological conditions. Visual meteorological conditions (VMC) are
applied when there is sufficient visibility for pilots of aircraft to be
able to navigate by referencing locations on the ground, as well as to
be able to see and avoid other aircraft in the area. Around airports,
VMC is defined as at least 3 statute miles visibility and cloud “ceil-
5
ings” (defined as at least / of the sky covered by clouds) of at least
8
1000 ft above the ground (AGL). Conversely, instrument meteoro-
logical conditions (IMC) exist when visibilities are less than 3 statute
miles and cloud ceilings are less than 1000 ft above the ground.
At its most basic level, aircraft operating in VMC tend to fly under
visual flight rules (VFR). VFR flight rules depend on aircraft opera-
tors to visually maintain adequate separation from terrain, clouds,
and other aircraft. Under VFR, aircraft navigation is based on visual
reference to locations on the ground, including visual identification
and approaches to airports.
While flying under VFR conditions, pilots may request from air
traffic control to be under “flight following.” Under flight following,
air traffic control operators provide assistance to pilots by supervising