CAA NZ ATPL Instruments & Navaids flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

ISA sea-level pressure

Standard atmosphere sea-level pressure is 1013.25 hPa (29.92 inHg) with temperature +15 °C; used as the reference for pressure altitude and flight levels.

QNH versus QFE

QNH is the altimeter setting that makes the altimeter read elevation above mean sea level on the ground; QFE makes it read height above a specified datum such as aerodrome.

Cold temperature altimeter error

In air colder than ISA, the altimeter over-reads and true altitude is lower than indicated, so terrain clearance is reduced; apply cold temperature corrections to approach minima.

Static port blockage effects

With static blocked, the altimeter freezes at the blockage altitude, the VSI reads zero after a transient, and the ASI behaves like an altimeter, over-reading in a climb.

Rigidity and precession

A spinning gyro maintains its axis in space (rigidity); an applied force causes precession at 90° in the direction of rotation, exploited in rate and turn instruments.

Attitude indicator erection error

Pendulous vanes erect the vertical gyro to apparent vertical; during sustained acceleration or turns the apparent vertical tilts, causing false climb or turn indications.

Standard rate turn

A standard rate turn is 3° per second, completing 360° in two minutes; approximate bank angle equals TAS in knots divided by ten plus half that value.

Inertial system drift

INS/IRS position is obtained by integrating acceleration twice, so small errors accumulate with time; accuracy degrades without GNSS or radio aiding.

Magnetic variation

Variation is the angle between true north and magnetic north at a location; easterly variation is subtracted when converting true to magnetic and added in reverse.

Compass deviation

Deviation is the angle between magnetic north and compass north caused by the aircraft's own magnetic fields; it is determined by compass swinging and recorded on a card.

ANDS and UNOS

In the northern hemisphere the magnetic compass shows an apparent turn to the north when accelerating and south when decelerating; it undershoots north and overshoots south in turns.

Magnetic dip

Dip is the inclination of magnetic flux lines to the horizontal; it is zero at the magnetic equator and 90° at the magnetic poles, causing turning and acceleration errors.

CAS, EAS and TAS

Calibrated airspeed corrects indicated airspeed for position error; equivalent airspeed corrects CAS for compressibility; true airspeed corrects EAS for air density.

Mach number relation

Mach number equals true airspeed divided by the local speed of sound, which depends only on temperature; about 661 knots at ISA sea level and lower when colder.

RVSM altimetry requirement

Reduced vertical separation minima require two independent altitude systems, an altitude alert, and one automatic altitude control, with altimetry accurate to within 200 feet.

VOR reverse sensing

Reverse sensing occurs when the selected OBS course is more than 90° from the aircraft's track; the needle deflects opposite to the required turn, so turn toward the needle.

DME slant range correction

DME measures slant range; ground distance equals the square root of slant range squared minus aircraft altitude squared, so error is significant only close to the station.

Relative bearing to QDM

Magnetic bearing to an NDB (QDM) equals relative bearing shown by the ADF plus magnetic heading; the QDR is the reciprocal, the bearing from the station.

ILS localizer and glidepath

Localizer gives lateral guidance on 108.10–111.95 MHz with 90 Hz left and 150 Hz right; glidepath is UHF 329.15–335 MHz, usually a 3° descent.

RNAV 5 specification

RNAV 5 permits navigation on any path within VOR/DME or self-contained coverage, with total system error not exceeding 5 nautical miles for 95% of flight time.

Fly-by versus fly-over

A fly-by waypoint allows turn anticipation to roll out on the next leg; a fly-over waypoint requires overflying the point before turning, often used for obstacles.

RNP versus RNAV

RNP is RNAV with on-board performance monitoring and alerting, so the crew is warned if the required navigation accuracy is not met; RNAV alone lacks this alerting.

GNSS position solution

A GNSS receiver measures signal travel time from satellites to compute pseudoranges; four satellites are needed to solve latitude, longitude, altitude and clock error.

SBAS and ABAS

Satellite-based augmentation uses ground networks and geostationary satellites to broadcast corrections and integrity; aircraft-based augmentation uses receiver autonomous integrity monitoring.

LPV approach

Localizer performance with vertical guidance uses SBAS to provide lateral and vertical guidance to a decision height as low as 200 feet without ground-based glidepath equipment.

Baro-VNAV temperature limit

Baro-VNAV computes vertical path from barometric altitude, so cold temperatures cause the aircraft to fly below the intended path; published temperature limits must be observed.

TCAS resolution advisory

TCAS II issues resolution advisories directing vertical manoeuvres; pilots must respond immediately, even against an ATC clearance, and notify ATC of the deviation.

GPWS Mode 2

Mode 2 warns of excessive terrain closure rate with the ground; it has an enroute mode and a terminal mode with different thresholds, and is inhibited at high altitude in some designs.

Weather radar attenuation

Heavy precipitation absorbs radar energy, so distant echoes beyond a storm may be weakened or missing; the shadow behind a strong cell can hide hazardous weather.

Autopilot mode annunciation

The flight mode annunciator shows engaged modes in green and armed modes in white; changes are highlighted so the crew can confirm autopilot and autothrottle status.

FMS position updating

The flight management system blends IRS, GNSS, DME/DME and VOR/DME data; radio or GNSS updating corrects inertial drift, and accuracy is monitored against RNP.

Mercator projection

The Mercator projection is conformal with straight rhumb lines, but scale increases with latitude, so great circles plot as curved lines except along the equator.

Wind triangle solution

Heading and true airspeed combined with the wind vector give track and groundspeed; the wind correction angle depends on wind speed, TAS and the angle between track and wind.