Aeronautical Terms beginning with I
IAF
Initial Approach Fix.
IAP
Instrument Approach Procedures.
IAS
Indicated Airspeed.
IAWP
Initial Approach Waypoint
ICA
Initial Climb Area
ICAO
International Civil Aviation Organization.
Ident
Air Traffic Control request for a pilot to push the button on the transponder to identify return on the controllers scope.
IF
Intermediate Fix
If No Transmission Received For (Time)
Used by ATC in radar approaches to prefix procedures which should be followed by the pilot in event of lost communications.
IFR
Instrument Flight Rules.
IFR (Instrument Flight Rules)
Rules that govern the procedure for conducting flight in weather conditions below VFR weather minimums. The term “IFR” also is used to define weather conditions and the type of flight plan under which an aircraft is operating.
IFR Aircraft
An aircraft conducting flight in accordance with instrument flight rules.
IFR conditions
Weather conditions below the minimum for flight under visual flight rules.
IFR Departure Procedure
IFR Takeoff Minimums And Departure Procedures.
IFR Flight
IFR Aircraft.
IFR Landing Minimums
Landing Minimums.
IFR over-the-top
With respect to the operation of aircraft, the operation of an aircraft over-the-top on an IFR flight plan when cleared by air traffic control to maintain “VFR conditions” or “VFR conditions on top”.
IFR Takeoff Minimums And Departure Procedures
Title 14 Code of Federal Regulations Part 91, prescribes standard takeoff rules for certain civil users. At some airports, obstructions or other factors require the establishment of nonstandard takeoff minimums, departure procedures, or both to assist pilots in avoiding obstacles during climb to the minimum en route altitude. Those airports are listed in FAA/DOD Instrument Approach Procedures (IAPs) Charts under a section entitled “IFR Takeoff Minimums and Departure Procedures.” The FAA/DOD IAP chart legend illustrates the symbol used to alert the pilot to nonstandard takeoff minimums and departure procedures. When departing IFR from such airports or from any airports where there are no departure procedures, DPs, or ATC facilities available, pilots should advise ATC of any departure limitations. Controllers may query a pilot to determine acceptable departure directions, turns, or headings after takeoff. Pilots should be familiar with the departure procedures and must assure that their aircraft can meet or exceed any specified climb gradients.
ILS
Instrument Landing System.
ILS Categories
1. Category I. An ILS approach procedure which provides for approach to a height above touchdown of not less than 200 feet and with runway visual range of not less than 1,800 feet. 2. Special Authorization Category I. An ILS approach procedure which provides for approach to a height above touchdown of not less than 150 feet and with runway visual range of not less than 1,400 feet, HUD to DH. 3. Category II. An ILS approach procedure which provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet (with autoland or HUD to touchdown and noted on authorization, RVR 1,000 feet). 4. Special Authorization Category II with Reduced Lighting. An ILS approach procedure which provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet with autoland or HUD to touchdown and noted on authorization (no touchdown zone and centerline lighting are required). 5. Category III: a. IIIA.-An ILS approach procedure which provides for approach without a decision height minimum and with runway visual range of not less than 700 feet. b. IIIB.-An ILS approach procedure which provides for approach without a decision height minimum and with runway visual range of not less than 150 feet. c. IIIC.-An ILS approach procedure which provides for approach without a decision height minimum and without runway visual range minimum.
ILS Category I
Provides for approach to a height above touchdown of not less than 200 feet, and with runway visual range of not less than 1,800 feet.
ILS Category II
Provides for approach to a height above touchdown of not less than 100 feet and with runway visual range of not less than 1,200 feet.
ILS Category IIIA
Provides for approach without a decision height minimum and with runway visual range of not less than 700 feet.
ILS Category IIIB
Provides for approach without a decision height minimum and with runway visual range of not less than 150 feet.
ILS Category IIIC
Provides for approach without a decision height minimum and without runway visual range minimum.
ILS/PRM
Instrument Landing System/Precision Runway Monitor
IM
ILS Inner Marker.
IMC
Instrument Meteorological Conditions.
Indicated airspeed (IAS)
Shown on the dial of the instrument airspeed indicator on an aircraft. Directly related to calibrated airspeed (CAS), IAS includes instrument errors and position error.
Indirect indication
A reflection of aircraft pitch-and-bank attitude by the 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.
Inertial navigation system (INS)
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.
Initial Approach
The segment between the initial approach fix and the intermediate fix or the point where the aircraft is established on the intermediate course or final approach course.
Initial approach fix (IAF)
The fix depicted on IAP charts where the instrument approach procedure (IAP) begins unless otherwise authorized by ATC.
Initial Approach Segment
Segments Of An Instrument Approach Procedure.
Initial Climb Area (ICA)
An area beginning at the departure end of runway (DER) to provide unrestricted climb to at least 400 feet above DER elevation.
Inner Marker
A marker beacon used with an ILS (CAT II) precision approach located between the middle marker and the end of the ILS runway, transmitting a radiation pattern keyed at six dots per second and indicating to the pilot, both aurally and visually, that he/she is at the designated decision height (DH), normally 100 feet above the touchdown zone elevation, on the ILS CAT II approach. It also marks progress during a CAT III approach.
Inner Marker Beacon
Inner Marker.
Inner-Approach OFZ
The inner-approach OFZ (Obstacle Free Zone)is a defined volume of airspace centered on the approach area. The inner-approach OFZ applies only to runways with an approach lighting system. The inner-approach OFZ begins 200 feet from the runway threshold at the same elevation as the runway threshold and extends 200 feet beyond the last light unit in the approach lighting system. The width of the inner-approach OFZ is the same as the runway OFZ and rises at a slope of 50 (horizontal) to 1 (vertical) from the beginning.
Inner-Transitional OFZ
The inner transitional surface OFZ (Obstacle Free Zone) is a defined volume of airspace along the sides of the runway and inner-approach OFZ and applies only to precision instrument runways. The inner-transitional surface OFZ slopes 3 (horizontal) to 1 (vertical) out from the edges of the runway OFZ and inner-approach OFZ to a height of 150 feet above the established airport elevation.
Inoperative components
Higher minimums are prescribed when the specified visual aids are not functioning; this information is listed in the Inoperative Components Table found in the United States Terminal Procedures Publications.
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 approach procedure (IAP)
A series of predetermined maneuvers by reference to flight instruments with specified protection from obstacles and assurance of navigation signal reception capability. It begins from the initial approach fix, or where applicable, from the beginning of a defined arrival route to a point:
(1) From which a landing can be completed; or
(2) If a landing is not completed, to a position at which holding or en route obstacle clearance criteria apply.
Instrument Approach Procedures (IAP) Charts
Portray the aeronautical data which is required to execute an instrument approach to an airport. These charts depict the procedures, including all related data, and the airport diagram. Each procedure is designated for use with a specific type of electronic navigation system including NDB, TACAN, VOR, ILS/MLS, and RNAV. These charts are identified by the type of navigational aid(s) which provide final approach guidance.
Instrument Approach Waypoint
Fixes used in defining RNAV IAPs, including the feeder waypoint (FWP), the initial approach waypoint (IAWP), the intermediate waypoint (IWP), the final approach waypoint (FAWP), the RWY WP, and the APT WP, when required.
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)
A precision instrument approach system that normally consists of the following electronic components and visual aids; localizer, glide slope, outer marker, middle marker, and approach lights.
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.
Instrument Procedure with Vertical Guidance (IPV)
Satellite or Flight Management System (FMS) lateral navigation (LNAV) with computed positive vertical guidance based on barometric or satellite elevation. This term has been renamed APV.
Instrument proficiency check
An evaluation ride based on the instrument rating practical test standard which is required to regain instrument flying privileges when the privileges have expired due to lack of currency.
Instrument Runway
A runway equipped with electronic and visual navigation aids for which a precision or nonprecision approach procedure having straight-in landing minimums has been approved.
Instrument takeoff
Using the instruments rather than outside visual cues to maintain runway heading and execute a safe takeoff.
Interference drag
Drag generated by the collision of airstreams creating eddy currents, turbulence, or restrictions to smooth flow.
Intermediate Approach
The segment between the intermediate fix or point and the final approach fix.
Intermediate Approach Segment
Segments Of An Instrument Approach Procedure.
Intermediate Fix
The fix that identifies the beginning of the intermediate approach segment of an instrument approach procedure. The fix is not normally identified on the instrument approach chart as an intermediate fix (IF).
International Civil Aviation Organization (ICAO)
ICAO is a specialized agency of the United Nations whose objective is to develop standard principles and techniques of international air navigation and to promote development of civil aviation.
International standard atmosphere (IAS)
A model of standard variation of pressure and temperature.
Into A.C
Current of the proper voltage and frequency to operate A.C. gyro instruments.
Inversion illusion
The feeling that the aircraft is tumbling backwards, caused by an abrupt change from climb to straight- and-level flight while in situations lacking visual reference.
IPV
Instrument Procedure With Vertical Guidance (This term has been renamed APV)
Isogonic lines
Lines drawn across aeronautical charts to connect points having the same magnetic variation.
IVSI
Instantaneous Vertical Speed Indicator.
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