Pilot/Controller Glossary

APPROPRIATE OBSTACLE CLEARANCE MINIMUM ALTITUDE- Any of the following:
(See MINIMUM EN ROUTE IFR ALTITUDE.)
(See MINIMUM IFR ALTITUDE.)
(See MINIMUM OBSTRUCTION CLEARANCE ALTITUDE.)
(See MINIMUM VECTORING ALTITUDE.)

APPROPRIATE TERRAIN CLEARANCE MINIMUM ALTITUDE- Any of the following:
(See MINIMUM EN ROUTE IFR ALTITUDE.)
(See MINIMUM IFR ALTITUDE.)
(See MINIMUM OBSTRUCTION CLEARANCE ALTITUDE.)
(See MINIMUM VECTORING ALTITUDE.)

APRON- A defined area on an airport or heliport intended to accommodate aircraft for purposes of loading or
unloading passengers or cargo, refueling, parking, or maintenance. With regard to seaplanes, a ramp is used for
access to the apron from the water.
(See ICAO term APRON.)

APRON [ICAO]- A defined area, on a land aerodrome, intended to accommodate aircraft for purposes of loading
or unloading passengers, mail or cargo, refueling, parking or maintenance.
ARC- The track over the ground of an aircraft flying at a constant distance from a navigational aid by reference
to distance measuring equipment (DME).
AREA CONTROL CENTER [ICAO]- An air traffic control facility primarily responsible for ATC services
being provided IFR aircraft during the en route phase of flight. The U.S. equivalent facility is an air route traffic
control center (ARTCC).
AREA NAVIGATION (RNAV)- A method of navigation which permits aircraft operation on any desired flight
path within the coverage of ground- or space-based navigation aids or within the limits of the capability of
self-contained aids, or a combination of these.
Note: Area navigation includes performance-based navigation as well as other operations that do not meet
the definition of performance-based navigation.

AREA NAVIGATION (RNAV) APPROACH CONFIGURATION:
a. STANDARD T- An RNAV approach whose design allows direct flight to any one of three initial approach
fixes (IAF) and eliminates the need for procedure turns. The standard design is to align the procedure on the
extended centerline with the missed approach point (MAP) at the runway threshold, the final approach fix (FAF),
and the initial approach/intermediate fix (IAF/IF). The other two IAFs will be established perpendicular to the
IF.
b. MODIFIED T- An RNAV approach design for single or multiple runways where terrain or operational
constraints do not allow for the standard T. The "T" may be modified by increasing or decreasing the angle from
the corner IAF(s) to the IF or by eliminating one or both corner IAFs.
c. STANDARD I- An RNAV approach design for a single runway with both corner IAFs eliminated. Course
reversal or radar vectoring may be required at busy terminals with multiple runways.
d. TERMINAL ARRIVAL AREA (TAA)- The TAA is controlled airspace established in conjunction with
the Standard or Modified T and I RNAV approach configurations. In the standard TAA, there are three areas:
straight-in, left base, and right base. The arc boundaries of the three areas of the TAA are published portions of
the approach and allow aircraft to transition from the en route structure direct to the nearest IAF. TAAs will also
eliminate or reduce feeder routes, departure extensions, and procedure turns or course reversal.
1. STRAIGHT-IN AREA- A 30 NM arc centered on the IF bounded by a straight line extending through
the IF perpendicular to the intermediate course.
2. LEFT BASE AREA- A 30 NM arc centered on the right corner IAF. The area shares a boundary with
the straight-in area except that it extends out for 30 NM from the IAF and is bounded on the other side by a line
extending from the IF through the FAF to the arc.