Instrument Flight
Glossary
I
IAF: See Initial Approach Fix.
IFR Aircraft: Aircraft conducting flights in accordance with instrument flight rules.
ILS: Instrument Landing System.
IMC: See Instrument Meteorological Conditions.
Initial Approach: That part of an instrument approach procedure consisting of the first approach to the
first navigational facility associated with the procedure or to a predetermined fix.
Initial Approach Fix (IAF): The fix depicted on an instrument approach plate that identifies the beginning
of the initial approach segment.
Instrument Meteorological Conditions (IMC): Weather conditions (visibility, ceiling, and cloud
clearance) below the minimums for flight under visual flight rules (VFR).
Intersection: An intersection is a point along an airway at which two or more radials from two or more
stations cross. An intersection may also be defined as a radial/DME fix. Intersections are used to
indicate fixed positions along the airways.
J
Jet Routes: A high altitude route system at or above 18,000 ft MSL up to FL450, predicated on a network
of designated VOR, TACAN, and/or VORTAC facilities.
Joint Use Restricted Area: An area wherein an aircraft may operate if prior permission has been
granted by either the restricted area “using agency” or ATC.
L
Localizer Approach: A non-precision instrument approach which utilizes only the course guidance
component of an ILS system (due to ground facility equipment or aircraft ILS glideslope failure). The
missed approach point (MAP) is determined by timing, DME or by radar.
M
Mandatory Altitude (Instrument Approach): The MSL altitude above a geographical location which an
aircraft must maintain during a portion of an instrument approach. A mandatory altitude is depicted by a
number with a line above and below it.
MAP: See Missed Approach Point.
Maximum Altitude (Instrument Approach): The MSL altitude above a geographical location which an
aircraft may not exceed during a portion of an instrument approach. The requirement for a maximum
altitude may be created by airspace separation criteria. On an approach plate, a maximum altitude is
depicted by a number with a line above it.
MDA: See Minimum Descent Altitude.
MEA: See Minimum Enroute Altitude.
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