Pilot/Controller Glossary

8/15/19

PCG I

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3

conduct these approaches. ATC utilizes an enhanced
display with alerting and, with certain runway
spacing, a high update rate PRM surveillance sensor.
Use of a secondary monitor frequency, pilot PRM
training, and publication of an Attention All Users
Page are also required for all PRM approaches.

(Refer to AIM)

IM

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(See INNER MARKER.

)

IMC

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(See INSTRUMENT METEOROLOGICAL

CONDITIONS.)

IMMEDIATELY

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Used by ATC or pilots when such

action compliance is required to avoid an imminent
situation.

INCERFA (Uncertainty Phase) [ICAO]

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 A situation

wherein uncertainty exists as to the safety of an
aircraft and its occupants.

INCREASED SEPARATION REQUIRED (ISR)–
Indicates the confidence level of the track requires
5NM separation. 3NM separation, 1 1/2NM
separation, and target resolution cannot be used.

INCREASE SPEED TO (SPEED)

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(See SPEED ADJUSTMENT.)

INERTIAL NAVIGATION SYSTEM (INS)

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 An

RNAV system which is a form of self-contained
navigation.

(See Area Navigation/RNAV.)

INFLIGHT REFUELING

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(See AERIAL REFUELING.)

INFLIGHT WEATHER ADVISORY

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(See WEATHER ADVISORY.)

INFORMATION REQUEST (INREQ)

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 A request

originated by an FSS for information concerning an
overdue VFR aircraft.

INITIAL APPROACH FIX (IAF)

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 The fixes

depicted on instrument approach procedure charts
that identify the beginning of the initial approach
segment(s).

(See FIX.)
(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

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

−

(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