SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE (JCS, NATO) -

(1)
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.

(2)
INTERMEDIATE APPROACH - That part of an instrument approach procedure from the first arrival at the navigation facility or predetermined fix, to the beginning of the final approach.

(3)
FINAL APPROACH - That part of an instrument approach procedure from the time the aircraft has:

(a)
Completed the last procedure turn or base turn where one is specified, or

(b) crossed a specified fix, or

(c)
intercepted the last track specified for the procedures; until it has crossed a point in the vicinity of an aerodrome from which:

(1)
 A landing can be made; or

(2)
 A missed approach procedure is initiated.

(4)
MISSED APPROACH PROCEDURE - The procedure to be followed if, after an instrument approach, a landing is not effected and occurring normally:

(a)
When the aircraft has descended to the Decision Height/altitude and has not established visual contact, or

(b)
when directed by Air Traffic Control to pull up or to go around again.

SEGMENTS OF AN INSTRUMENT APPROACH PROCEDURE (ICAO) -

(1)
INITIAL APPROACH SEGMENT - That segment of an instrument approach procedure between the Initial Approach Fix and the intermediate approach fix or, where applicable, the Final Approach Fix or point.

(2)
INTERMEDIATE APPROACH SEGMENT - That segment of an instrument approach procedure between either the intermediate approach fix and the Final Approach Fix or point, or between the end of a reversal, race track or dead reckoning track procedure and the Final Approach Fix or point, as appropriate.

(3)
FINAL APPROACH SEGMENT - That segment of an instrument approach procedure in which alignment and descent for landing are accomplished.

(4)
MISSED APPROACH PROCEDURE - The procedure to be followed if the approach cannot be continued.

SELECTIVE CALLING SYSTEM/SELCAL (ICAO) - A system which permits selective calling of individual aircraft over radio telephone channels linking a ground station with the aircraft.
SEPARATION (P/CG) - In Air Traffic Control, the spacing of aircraft to achieve their safe and orderly movement in flight and while landing and take-off. (See Separation Minima)
SEPARATION (ICAO) - Spacing between aircraft, levels or tracks.
SEPARATION MINIMA - The minimum longitudinal, lateral, or vertical distances by which aircraft are spaced through the application of Air Traffic Control procedures. (See Separation)
SEVERE WEATHER AVOIDANCE PLAN/SWAP - An approved plan to minimize the affect of severe weather on traffic flows in impacted terminal and/or Air Route Traffic Center areas. SWAP is normally implemented to provide the least disruption to the Air Traffic Control system when flight through portions of airspace is difficult or impossible due to severe weather.