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12/2/21 

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 Canada and Mexico, including 
adjacent territorial waters outward to about bound­
aries 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, No­
tices 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. 

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: 

a. 

RNP specification. A navigation specification 

based on area navigation that includes the 
requirement for performance monitoring and 
alerting, designated by the prefix RNP; e.g., RNP 4, 
RNP APCH. 

b. 

RNAV specification. A navigation specifica­

tion based on area navigation that does not include the 
requirement for performance monitoring and alert­
ing, designated by the prefix RNAV; e.g., RNAV 5, 
RNAV 1. 

Note: The Performance

based Navigation Manual 

(Doc 9613), Volume II contains detailed guidance 
on navigation specifications. 

NAVIGATIONAL AID

 Any visual or electronic 

device airborne or on the surface which provides 
point­to­point guidance information or position data 
to aircraft in flight. 

(See AIR NAVIGATION FACILITY.) 

NAVSPEC­

(See NAVIGATION SPECIFICATION [ICAO].) 

PCG N