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Pilot/Controller Glossary

3/29/18

PCG I−3

IMMEDIATELY− Used by ATC or pilots when such

action compliance is required to avoid an imminent

situation.
INCERFA (Uncertainty Phase) [ICAO]− 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)−

(See SPEED ADJUSTMENT.)

INERTIAL NAVIGATION SYSTEM (INS)− An

RNAV system which is a form of self-contained

navigation.

(See Area Navigation/RNAV.)

INFLIGHT REFUELING−

(See AERIAL REFUELING.)

INFLIGHT WEATHER ADVISORY−

(See WEATHER ADVISORY.)

INFORMATION REQUEST (INREQ)− A request

originated by an FSS for information concerning an

overdue VFR aircraft.
INITIAL APPROACH FIX (IAF)− 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−

(See SEGMENTS OF AN INSTRUMENT

APPROACH PROCEDURE.)

INITIAL APPROACH SEGMENT [ICAO]− 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− A navigation

aid on a North American Route at which the common

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

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

INNER MARKER BEACON−

(See INNER MARKER.)

INREQ−

(See INFORMATION REQUEST.)

INS−

(See INERTIAL NAVIGATION SYSTEM.)

INSTRUMENT APPROACH−

(See INSTRUMENT APPROACH

PROCEDURE.)

INSTRUMENT APPROACH OPERATIONS

[ICAO]− 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−dimensional (2D) instrument approach

operation, using lateral navigation guidance only;

and

b. A three−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−based radio navigation aid; or

b) computer−generated navigation data from

ground−based, space−based, self−contained

navigation aids or a combination of these.

(See ICAO term INSTRUMENT APPROACH

PROCEDURE.)

INSTRUMENT APPROACH PROCEDURE− 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