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 point-to-point guidance information or position data to aircraft in flight. 

(See AIR NAVIGATION FACILITY.) 

(See NAVIGATION SPECIFICATION [ICAO].) 

## NBCAP AIRSPACE- 

(See NATIONAL BEACON CODE ALLOCATION PLAN AIRSPACE.) 

## NDB- 

(See NONDIRECTIONAL BEACON.) 

NEGATIVE- “No,” or “permission not granted,” or “that is not correct.” 

NEGATIVE CONTACT- Used by pilots to inform ATC that: 

a. Previously issued traffic is not in sight. It may be followed by the pilot's request for the controller to provide assistance in avoiding the traffic. 

b. They were unable to contact ATC on a particular frequency. 

## NFDC- 

(See NATIONAL FLIGHT DATA CENTER.) 

## NFDD- 

(See NATIONAL FLIGHT DATA DIGEST.) 

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

(See ICAO term NIGHT.) 

NIGHT [ICAO]- The hours between the end of evening civil twilight and the beginning of morning civil twilight or such other period between sunset and sunrise as may be specified by the appropriate authority. 

Note: Civil twilight ends in the evening when the center of the sun's disk is 6 degrees below the horizon and begins in the morning when the center of the sun's disk is 6 degrees below the horizon. 

## $_{ }$ 

NO GYRO APPROACH- A radar approach/vector provided in case of a malfunctioning gyro-compass or directional gyro. Instead of providing the pilot with headings to be flown, the controller observes the radar track and issues control instructions “turn right/left” or “stop turn” as appropriate. 

(Refer to AIM.) 

## NO GYRO VECTOR- 

(See NO GYRO APPROACH.) 

NO TRANSGRESSION ZONE (NTZ)- The NTZ is a 2,000 foot wide zone, located equidistant between parallel runway or SOIA final approach courses, in which flight is normally not allowed. 

NONAPPROACH CONTROL TOWER- Author- izes aircraft to land or takeoff at the airport controlled by the tower or to transit the Class D airspace. The primary function of a nonapproach control tower is the sequencing of aircraft in the traffic pattern and on the landing area. Nonapproach control towers also separate aircraft operating under instrument flight rules clearances from approach controls and centers. They provide ground control services to aircraft, vehicles, personnel, and equipment on the airport movement area. 

NONCOMMON ROUTE/PORTION- That segment of a North American Route between the inland navigation facility and a designated North American terminal. 

NON-COOPERATIVE SURVEILLANCE- Any surveillance system, such as primary radar, that is not dependent upon the presence of any equipment on the aircraft or vehicle to be tracked. 

(See COOPERATIVE SURVEILLANCE.) 

(See RADAR.) 

NONDIRECTIONAL BEACON- An L/MF or UHF radio beacon transmitting nondirectional 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. 

(See AUTOMATIC DIRECTION FINDER.) 

(See COMPASS LOCATOR.) 

NONMOVEMENT AREAS- Taxiways and apron (ramp) areas not under the control of air traffic. 

