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NACELLE - A streamlined enclosure or housing to protect something such as the crew, engine or landing gear.

NASA - National Aeronautics and Space Agency (USA).

NATIONAL AIRSPACE SYSTEM (NAS) - The common network of US airspace; air navigation facilities, equipment and services, airports or landing areas; aeronautical charts, information and services; rules, regulations and procedures, technical information, and human resources and material. Included are system components shared jointly with the military.

NAUTICAL MILE - Measurement of distance. Equals 1.15 statute miles.

NAV - Navigation Receivers.

NAV/COM - Navigation and communication radios combined in a single unit.

NAVAID - Navigation Aid (Ground Radio Station for Navigation).

NAVIGABLE AIRSPACE - airspace at and above the minimum flight altitudes prescribed by or under this chapter, including airspace needed for safe takeoff and landing.

NAVIGATION - A system, usually software, in which the primary purpose is to generate position relative to a coordinate frame, usually fixed earth frame, such as latitude and longitude or UTM.

NAVIGATION AID - A device or process to help with navigation, such as a VOR station or a position update.

NAVIGATION REFERENCE POINT - A point, usually fixed in earth coordinates but possibly moving.

NDB - Non-Directional Beacon. An LF, MF or UHF radio beacon transmitting non-directional signals so that a pilot of an aircraft equipped with direction finding equipment can determine his/her bearing to or from the radio beacon and "home" on or track to or from the station. When the radio beacon is installed in conjunction with the Instrument Landing System marker, it is normally called a Compass Locator.

NIGHT - the time between the end of evening civil twilight and the beginning of morning civil twilight, as published in the American Air Almanac, converted to local time.

NON-DIRECTIONAL BEACON - An L/MF or UHF radio beacon transmitting non directional signals whereby the pilot of an aircraft equipped with direction finding equipment can determine his/her bearing to or from the radio beacon and "home" on or track to or from the station. When the radio beacon is installed in conjunction with the Instrument Landing System marker, it is normally called a Compass Locator. It is an older type of electronic navigation aid, basically a low-power AM radio station.

NON-SCHEDULED SERVICE - Revenue flights, such as charter flights, that are not operated in regular scheduled service and all non revenue flights incident to such flights.

NONPRECISION APPROACH PROCEDURE - a standard instrument approach procedure in which no electronic glide slope is provided.

NOPT - no procedure turn required.

NOSE - The front portion of a aircraft`s fuselage.

NOSE GEAR - The strut and wheel that`s under the nose of some aircraft.

NOTAM - Notice to Airmen.

NTSB - National Transportation Safety Board. Investigates airplane accidents.

NPRM - Notice of Proposed Rule-Making (USA).