Instrument Flight
Glossary
Circling Approach: A maneuver initiated by the pilot to visually align the aircraft with a runway for landing.
This maneuver may be made only with ATC authorization and if the pilot has established the required visual
reference to the airport.
Class D Airspace: That airspace which surrounds tower controlled airfields and extends 4.4 nm in radius
from the center and to 2,500 ft above the airport. Radio communication with the tower is required within
this airspace. (Depicted as a segmented blue line on low altitude enroute charts)
Clearance Limit: The fix to which an aircraft is cleared when issued an ATC clearance.
Compulsory Reporting Point: A point the passage of which must be reported to ATC, unless in radar
contact.
Contact Approach: A pilot-requested approach wherein an aircraft on an IFR flight plan, operating clear
of the clouds with at least 1 sm visibility and having ATC authorization, may deviate from the prescribed
instrument approach procedure and proceed to the airport of destination by visual reference to the
surface.
Controlled Airspace: Airspace designated as Class A through Class E within which some or all aircraft
may be subject to air traffic control.
Course: A magnetic direction to fly in relation to a radio navigational facility. Note that a course is not
simply a heading. For flight inbound on a radial, the course is the reciprocal of the radial. For flight
outbound, the course and the radial are the same.
D
Decision Height (DH): The altitude during a precision approach at which a pilot must decide whether to
execute a missed approach or to continue the approach (weather and safety permitting).
DH: See Decision Height.
DME: Distance measuring equipment. (See TACAN.)
DME Fix: A geographical position determined by reference to a navigational aid and defined by a
specified distance in nautical miles and radial in degrees from said aid. For example: a DME fix located
10 nm west of the NSE VORTAC on the 270-degree radial would be written as NSE 270 010.
Dogleg: A vector to the final approach course (usually within 30 degrees of runway heading).
E
EFC: See Expected Further Clearance Time.
Emergency Fuel: An emergency situation in which the pilot cannot accept any delays and requires the
most direct and expeditious routing for landing.
Emergency Safe Altitude: An altitude expressed in 100-ft increments providing 1,000 ft (2,000 ft in
designated mountainous areas) of clearance over all obstructions/terrain within a 100-nautical mile radius.
Expected Further Clearance Time (EFC): The time at which it is expected that additional clearance will
be issued to an aircraft.
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