Pilot/Controller Glossary

NAS-
(See NATIONAL AIRSPACE SYSTEM.)

NAT HLA"
(See NORTH ATLANTIC HIGH LEVEL AIRSPACE.)

NATIONAL AIRSPACE SYSTEM- The common network of U.S. airspace; air navigation facilities, equipment
and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and
procedures, technical information, and manpower and material. Included are system components shared jointly
with the military.
NATIONAL BEACON CODE ALLOCATION PLAN AIRSPACE (NBCAP)- Airspace over United States
territory located within the North American continent between Canadnd Mexico, including adjacent territorial
waters outward to about boundaries of oceanic control areas (CTA)/Flight Information Regions (FIR).
(See FLIGHT INFORMATION REGION.)

NATIONAL FLIGHT DATA DIGEST (NFDD)- A daily (except weekends and Federal holidays) publication
of flight information appropriate to aeronautical charts, aeronautical publications, Notices to Air Missions, or
other media serving the purpose of providing operational flight data essential to safe and efficient aircraft
operations.
NATIONAL SEARCH AND RESCUE PLAN- An interagency agreement which provides for the effective
utilization of all available facilities in all types of search and rescue missions.
NATIONAL SECURITY AREA (NSA)"
(See SPECIAL USE AIRSPACE.)

NAVAID-
(See NAVIGATIONAL AID.)

NAVAID CLASSES- VOR, VORTAC, and TACAN aids are classed according to their operational use. The
three classes of NAVAIDs are:
a. T- Terminal.
b. L- Low altitude.
c. H- High altitude.
Note: The normal service range for T, L, and H class aids is found in the AIM. Certain operational requirements
make it necessary to use some of these aids at greater service ranges than specified. Extended range is made
possible through flight inspection determinations. Some aids also have lesser service range due to location,
terrain, frequency protection, etc. Restrictions to service range are listed in Chart Supplement U.S.

NAVIGABLE AIRSPACE- Airspace at and above the minimum flight altitudes prescribed in the CFRs
including airspace needed for safe takeoff and landing.
(Refer to 14 CFR Part 91.)

NAVIGATION REFERENCE SYSTEM (NRS)- The NRS is a system of waypoints developed for use within
the United States for flight planning and navigation without reference to ground based navigational aids. The
NRS waypoints are located in a grid pattern along defined latitude and longitude lines. The initial use of the NRS
will be in the high altitude environment. The NRS waypoints are intended for use by aircraft capable of
point-to-point navigation.
NAVIGATION SPECIFICATION [ICAO]- A set of aircraft and flight crew requirements needed to support
performance-based navigation operations within a defined airspace. There are two kinds of navigation
specifications: