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A precision approach is an instrument approach and landing using precision lateral and vertical guidance with minima as determined by the category of operation.
Note. Lateral and vertical guidance refers to the guidance provided either by:
a) a ground-based navigation aid; or
b) computer generated navigation data displayed to the pilot of an aircraft.
c) a controller interpreting the display on a radar screen (Precision Approach Radar (PAR)).
Categories of precision approach and landing (including Instrument Landing System (ILS) and Autoland) operations are defined according to the applicable Decision Altitude/Height and Runway Visual Range (RVR) or visibility as shown in the following table.
|Category of Operation||Decision Height (DH) (2)||RVR||Visibility not less than|
|CAT I||not lower than 60 m (200 ft)||not less than 550 m||800m|
|CAT II||lower than 60 m (200 ft), but not lower than 30 m (100 ft)||not less than 350 m (1)|
|CAT IIIA||lower than 30 m (100 ft) or no DH||not less than 200 m|
|CAT IIIB||lower than 15 m (50 ft) or no DH||less than 200 m but not less than 50 m|
|CAT IIIC||no DH||no RVR limitation|
(1) Appendix 1 to JAR-OPS 1.430, Table 6, permits the use of an RVR of 300m for Category D aircraft conducting an autoland.
(2) Vertical minima:
- CAT I Because the aircraft is unlikely to be flying over level ground at the same elevation as the touch-down zone when passing the Missed Approach Point, the vertical minima used in a CAT I approach is measured by reference to a barometric altimeter. In practice, this means that when flying a CAT I approach either a Decision Altitude/Height or Decision Altitude/Height may be used.
- CAT II/III Because greater precision is required when flying a CAT II or CAT III approach, special attention is given to the terrain in the runway undershoot to enable a radio altimeter to be used. CAT II and CAT III approaches are therefore always flown to a DH with reference to a radio altimeter.
CAT II and CAT III instrument approach and landing operations are not permitted unless RVR information is provided.
- ^ ICAO Annex 6
- JAR-OPS 1 Subpart E (All Weather Operations).