Aeronautical Terms beginning with I
I Say Again
The message will be repeated.
IAS
Indicated Airspeed.
ICAO
International Civil Aviation Organization.
Icing
The accumulation of airframe ice. Types of icing are: Rime Ice, Clear Ice, Mixed.
Icing Intensity
Trace, Light, Moderate, Severe.
Ident
Air Traffic Control request for a pilot to push the button on the transponder to identify return on the controller’s scope.
Idle thrust
The jet thrust obtained with the engine power control level set at the stop for the least thrust position at which it can be placed.
IFR
Instrument Flight Rules. A set of rules governing the conduct of flight under instrument meteorological conditions.
IFR Conditions
Weather conditions below the minimum for flight under visual flight rules.
IFR Military Training Routes (IR)
Routes used by the Department of Defense and associated Reserve and Air Guard units for the purpose of conducting low-altitude navigation and tactical training in both IFR and VFR weather conditions below 10,000 feet MSL at airspeeds in excess of 250 knots IAS.
IFSD
In-Flight Shutdown.
ILS
Instrument Landing System. A ground based precision approach system that provides course and vertical guidance to landing aircraft.
ILS PRM Approach
An instrument landing system (ILS) approach conducted to parallel runways whose extended centerlines are separated by less than 4,300 feet and the parallel runways have a Precision Runway Monitoring (PRM) system that permits simultaneous independent ILS approaches.
IMC
Instrument Meteorological Conditions
Immediately
Used by ATC or pilots when such action compliance is required to avoid an imminent situation.
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.
Increase Speed To (Speed)
Speed Adjustment.
Indicated Airspeed (IAS)
The direct instrument reading obtained from the airspeed indicator, uncorrected for variations in atmospheric density, installation error, or instrument error. Manufacturers use this airspeed as the basis for determining airplane performance. Takeoff, landing, and stall speeds listed in the AFM or POH are indicated airspeeds and do not normally vary with altitude or temperature.
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.
Inflight Refueling
Aerial Refueling.
Inflight Weather Advisory
Weather Advisory.
Initial Climb
This stage of the climb begins when the airplane leaves the ground, and a pitch attitude has been established to climb away from the takeoff area.
Instrument
A device using an internal mechanism to show visually or aurally the attitude, altitude, or operation of an aircraft or aircraft part. It includes electronic devices for automatically controlling an aircraft in flight.
Instrument Approach
Instrument Approach Procedure.
Instrument approach procedures (IAP)
A series of predetermined maneuvers for the orderly transfer of an aircraft under IFR from the beginning of the initial approach to a landing or to a point from which a landing may be made visually.
Instrument Departure Procedure (DP)
A preplanned instrument flight rule (IFR) departure procedure published for pilot use, in graphic or textual format, that provides obstruction clearance from the terminal area to the appropriate en route structure. There are two types of DP, Obstacle Departure Procedure (ODP), printed either textually or graphically, and, Standard Instrument Departure (SID), which is always printed graphically.
Instrument Departure Procedure (DP) Charts
Designed to expedite clearance delivery and to facilitate transition between takeoff and en route operations. Each DP is presented as a separate chart and may serve a single airport or more than one airport in a given geographical location.
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.
Instrument landing system (ILS)
An electronic system that provides both horizontal and vertical guidance to a specific runway, used to execute a precision instrument approach procedure.
Instrument meteorological conditions (IMC)
Meteorological conditions expressed in terms of visibility, distance from clouds, and ceiling less than the minimums specified for visual meteorological conditions, requiring operations to be conducted under IFR.
INT
Intersection.
Integrated flight instruction
A technique of flight instruction in which students are taught to perform flight maneuvers by reference to both the flight instruments and to outside visual references from the time the maneuver is first introduced. Handling of the controls is the same regardless of whether flight instruments or outside references are being used.
Integrity
The ability of a system to provide timely warnings to users when the system should not be used for navigation.
International Airport
Relating to international flight, it means: a. An airport of entry which has been designated by the Secretary of Treasury or Commissioner of Customs as an international airport for customs service. b. A landing rights airport at which specific permission to land must be obtained from customs authorities in advance of contemplated use. c. Airports designated under the Convention on International Civil Aviation as an airport for use by international commercial air transport and/or international general aviation.
International Civil Aviation Organization [ICAO]
A specialized agency of the United Nations whose objective is to develop the principles and techniques of international air navigation and to foster planning and development of international civil air transport. Regions include: 1. African-Indian Ocean Region 2. Caribbean Region 3. European Region 4. Middle East/Asia Region 5. North American Region 6. North Atlantic Region 7. Pacific Region 8. South American Region
International Flight Information Manual
A publication designed primarily as a pilot’s preflight planning guide for flights into foreign airspace and for flights returning to the U.S. from foreign locations.
International standard atmosphere (IAS)
A model of standard variation of pressure and temperature.
Interpolate
To determine a value in a series between two known values.
Interpolation
The estimation of an intermediate value of a quantity that falls between marked values in a series. Example: In a measurement of length, with a rule that is marked in eighths of an inch, the value falls between 3/8 inch and 1/2 inch. The estimated (interpolated) value might then be said to be 7/16 inch.
Interrogator
The ground-based surveillance radar beacon transmitter-receiver, which normally scans in synchronism with a primary radar, transmitting discrete radio signals which repetitiously request all transponders on the mode being used to reply. The replies received are mixed with the primary radar returns and displayed on the same plan position indicator (radar scope). Also, applied to the airborne element of the TACAN/DME system.
Intersecting Runways
Two or more runways which cross or meet within their lengths.
Intersection
A. A point defined by any combination of courses, radials, or bearings of two or more navigational aids.
B. Used to describe the point where two runways, a runway and a taxiway, or two taxiways cross or meet.
Intersection Departure
A departure from any runway intersection except the end of the runway.
Intersection Takeoff
Intersection Departure.
Inversion
An increase in temperature with altitude.
IR
IFR Military Training Route
ISA (International Standard Atmosphere)
Standard atmospheric conditions consisting of a temperature of 59°F (15°C), and a barometric pressure of 29.92 in. Hg. (1013.2 mb) at sea level. ISA values can be calculated for various altitudes using a standard lapse rate of approximately 2°C per 1,000 feet.
Isogonic lines
Lines drawn across aeronautical charts to connect points having the same magnetic variation.
IVSI
Instantaneous Vertical Speed Indicator.
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