Glossary of Aviation Terminology

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IAS: Indicated airspeed

IBC: Ils Back Course

IBIT: Initiated built-in-test

IDS: Infrared Detecting Set

ILS: Instrument Landing System

ILS approach: To approach a runway using ILS

ILS Back Course (IBC): Operation of ILS in which the runway is approached in reverse direction, giving only lateral guidance; Compare: ILS Front Course;

ILS Front Course: Operation of ILS in which the runway is approached in forward direction, giving lateral, longitudinal, and vertical guidance; sometimes called ILS Compare: ILS Back Course;

Indicated airspeed (IAS): Airspeed as instruments would indicate, not corrected for instrumentation errors or air density; See Also: airspeed; Symbols: V sub 'IAS'; Typical Units: kt,ft/s; Dimensions: Length / Time;

Inertial: Based on inertia, such as with an INS or an AHRS

Inertial Navigation System (INS): An Inertial Navigation System (INS) is a self-contained navigation system. It consists of gyroscopes and accelerometers to provide attitude, heading, position, attitude, body/inertial velocity, and acceleration information. A primary navigation data source. INS loses accuracy with time due to drift of gyroscopes. INS-DNS is moderately accurate over land, not good over water. See Also: Inertial Navigation Unit;

Inertial Navigation Unit (INU): A self-contained Inertial Navigation System;

Infrared Detecting Set (IDS): Forward-Looking Infrared;

Initialization: A basic control to a data source from controls and displays for initializing a device. Initiated by power-on, operator, driver, or MC; During initialization, the device is usually not available; Also, a procedure to reset physical devices to a known state; Values: initialization in progress, not initialized, unreliable, normal, redundant, degraded, failed. See Also: alignment, boresighting, calibration;

Initiated built-in-test (IBIT): Selftests running internal to a device initiated external to the device, usually an operator, causing the device to temporarily cease normal operation; Compare: periodic built-in-test;

Inner marker: Innermost marker beacon on an ILS

INS: Inertial Navigation System

Instrument Landing System (ILS): Equipment determining glideslope, localizer (bearing), and distance (marker beacon) to a runway; ILS provides precision aiding for landing; ILS is usually part of a VOR station. A basic guidance mode, providing lateral guidance, longitudinal guidance, and vertical guidance to approach a runway for landing; in ILS back course, vertical guidance is not provided

Instrumentation: Hardware to measure and to monitor a system

Integrate: To combine multiple systems; Also, to compute to integral of;

Integrator: A function that integrates; Many types of integrators exist; in fact, they constitute entire books. Avionics software usually relies on rectangular, single integrators, but occassional uses trapezoidal or double integrators.

International: A standard model for computing earth data

Interpolate: Function to determine intermediate values from two or values in a table; usually linear but can be higher order; endpoints are either extrapolated or limited;

Interrogation: A request of data

INTLIM: Path integral limit

INTMAGLIM: Altitude integral limit

INTVAL: Path integral value

INU: Inertial Navigation Unit

Invalid: An indication that data from a device is bad and cannot be trusted

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