Glossary

This glossary contains information on terms, phrases and abbreviations used by the Aviation industry. While this list does not include all aviation terminology, it is the purpose of this glossary to aid the general viewer in better understanding aviation terms as it pertains to content on this website. A full list of aviation terminology can be found here.
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

I

IAS

See indicated airspeed

ICAO

See International Civil Aviation Organization.

Ident

Air Traffic Control request for a pilot to push the button on the transponder to identify return on the controller’s scope.

IFR

See instrument flight rules.

IMC

See instrument meteorological conditions.

Inclinometer

An instrument consisting of a curved glass tube, housing a glass ball, and damped with a fluid similar to kerosene. It may be used to indicate inclination, as a level, or, as used in the turn indicators, to show the relationship between gravity and centrifugal force in a turn.

Indicated airspeed (IAS)

Shown on the dial of the instrument airspeed indicator on an aircraft. Indicated airspeed (IAS) is the airspeed indicator reading uncorrected for instrument, position, and other errors. Indicated airspeed means the speed of an aircraft as shown on its pitot static airspeed indicator calibrated to reflect standard atmosphere adiabatic compressible flow at sea level uncorrected for airspeed system errors. Calibrated airspeed (CAS) is IAS corrected for instrument errors, position error (due to incorrect pressure at the static port) and installation errors.

Indicated altitude

The altitude read directly from the altimeter (uncorrected) when it is set to the current altimeter setting.

Indirect indication

A reflection of aircraft pitch-and-bank attitude by instruments other than the attitude indicator.

Induced drag

Drag caused by the same factors that produce lift; its amount varies inversely with airspeed. As airspeed decreases, the angle of attack must increase, in turn increasing induced drag.

Induction icing

A type of ice in the induction system that reduces the amount of air available for combustion. The most commonly found induction icing is carburetor icing.

A computer-based navigation system that tracks the movement of an aircraft via signals produced by onboard accelerometers. The initial location of the aircraft is entered into the computer, and all subsequent movement of the aircraft is sensed and used to keep the position updated. An INS does not require any inputs from outside signals.

INS

See inertial navigation system.

Instantaneous vertical speed indicator (IVSI)

Assists in interpretation by instantaneously indicating the rate of climb or descent at a given moment with little or no lag as displayed in a vertical speed indicator (VSI).

Instrument flight rules (IFR)

Rules and regulations established by the Federal Aviation Administration to govern flight under conditions in which flight by outside visual reference is not safe. IFR flight depends upon flying by reference to instruments in the flight deck, and navigation is accomplished by reference to electronic signals.