b.
The ILS localizer signal pattern usually specified as the front course or the back course.

c..The intended track along a straight, curved, or segmented MLS path.
(See BEARING.)
(See INSTRUMENT LANDING SYSTEM.)
(See MICROWAVE LANDING SYSTEM.)
(See RADIAL.)
CPDLC-
(See CONTROLLER PILOT DATA LINK
COMMUNICATIONS.)

CPL [ICAO]-
(See ICAO term CURRENT FLIGHT PLAN.)
CRITICAL ENGINE- The engine which, upon failure, would most adversely affect the performance or handling qualities of an aircraft.
CROSS (FIX) AT (ALTITUDE)- Used by ATC when a specific altitude restriction at a specified fix is required.
CROSS (FIX) AT OR ABOVE (ALTITUDE)- Used by ATC when an altitude restriction at a specified fix is required. It does not prohibit the aircraft from crossing the fix at a higher altitude than specified; however, the higher altitude may not be one that will violate a succeeding altitude restriction or altitude assignment.
(See ALTITUDE RESTRICTION.)
(Refer to AIM.)

CROSS (FIX) AT OR BELOW (ALTITUDE)-
Used by ATC when a maximum crossing altitude at a specific fix is required. It does not prohibit the aircraft from crossing the fix at a lower altitude; however, it must be at or above the minimum IFR altitude.
(See ALTITUDE RESTRICTION.)
(See MINIMUM IFR ALTITUDES.)
(Refer to 14 CFR Part 91.)
CROSSWIND-
a..When used concerning the traffic pattern, the word means “crosswind leg.”
(See TRAFFIC PATTERN.)
b..When used concerning wind conditions, the word means a wind not parallel to the runway or the path of an aircraft.