Pilot/Controller Glossary

Pilot/Controller Glossary

IFWP- Intermediate Fix Waypoint
ILS-
(See 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.
IM-
(See INNER MARKER.)
IMC-
(See INSTRUMENT METEOROLOGICAL CONDITIONS.)

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 5 NM
separation. 3 NM separation, 1  NM 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 SERVICES [FSS]" Services provided to or affecting aircraft inflight or otherwise operating on the
airport surface. This includes services to airborne aircraft, such as the delivery of ATC clearances, advisories or
requests, issuance of military flight advisory messages, NOTAM delivery, search and rescue communications
searches, flight plan handling, transcribed or live broadcasts, weather observations, PIREPs, and pilot briefings.
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.)