Pilot/Controller Glossary 

10/5/23 

INITIAL APPROACH SEGMENT

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(See SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE.) 

INITIAL APPROACH SEGMENT [ICAO]

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 That segment of an instrument approach procedure between the 

initial approach fix and the intermediate approach fix or, where applicable, the final approach fix or point. 
INLAND NAVIGATION FACILITY

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 A navigation aid on a North American Route at which the common route 

and/or the noncommon route begins or ends. 
INNER MARKER

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 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. 

(See INSTRUMENT LANDING SYSTEM.) 
(Refer to AIM.) 

INNER MARKER BEACON

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(See INNER MARKER.) 

INREQ

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(See INFORMATION REQUEST.) 

INS

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(See INERTIAL NAVIGATION SYSTEM.) 

INSTRUMENT APPROACH

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(See INSTRUMENT APPROACH PROCEDURE.) 

INSTRUMENT APPROACH OPERATIONS [ICAO]

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An approach and landing using instruments for 

navigation guidance based on an instrument approach procedure. There are two methods for executing 

instrument approach operations: 

a. 

A two

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dimensional (2D) instrument approach operation, using lateral navigation guidance only; and 

b. 

A three

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dimensional (3D) instrument approach operation, using both lateral and vertical navigation 

guidance. 

Note: Lateral and vertical navigation guidance refers to the guidance provided either by: 

a) a ground

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based radio navigation aid; or 

b) computer

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generated navigation data from ground

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based, space

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based, self

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contained navigation aids 

or a combination of these. 

(See ICAO term INSTRUMENT APPROACH PROCEDURE.) 

INSTRUMENT APPROACH PROCEDURE

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 A series of predetermined maneuvers for the orderly transfer of 

an aircraft under instrument flight conditions from the beginning of the initial approach to a landing or to a point 

from which a landing may be made visually. It is prescribed and approved for a specific airport by competent 

authority. 

(See SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE.) 
(Refer to 14 CFR Part 91.) 
(Refer to AIM.) 

a. 

U.S. civil standard instrument approach procedures are approved by the FAA as prescribed under 14 CFR 

Part 97 and are available for public use. 

b. 

U.S. military standard instrument approach procedures are approved and published by the Department of 

Defense. 

c. 

Special instrument approach procedures are approved by the FAA for individual operators but are not 

published in 14 CFR Part 97 for public use. 

(See ICAO term INSTRUMENT APPROACH PROCEDURE.) 

PCG I

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