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In terms of aircraft equipment, approach minimums, procedural differences, and anything else relevant, how do the 3 types of a Cat III ILS differ from one another?

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    $\begingroup$ You may narrow your question as a simple search on wikipedia gives lots of information and great references to answer a significant part of your question. $\endgroup$ – Manu H Jul 10 '15 at 14:06
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ICAO and FAA CAT III definitions

A CAT III operation is a precision approach at lower than CAT II minima. Sub-categories are listed below.

  • A category III A approach is a precision instrument approach and landing with no decision height or a decision height lower than 100ft (30m) and a runway visual range not less than 700ft (200m).

  • A category III B approach is a precision approach and landing with no decision height or a decision height lower than 50ft (15m) and a runway visual range less than 700ft (200m), but not less than 150ft (50m).

  • A category III C approach is a precision approach and landing with no decision height and no runway visual range limitation.

*I've omitted the JAA definitions.

Source Airbus Flight Operations Support documentation.


FAA Reference Material

The below links are to comprehensive FAA publications covering the areas as titled.

FAA AC120-29 for CAT I/II.

FAA AC120-28 for CAT III.

Thanks @Sports Racer for the comment with links to these documents.

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From: AC 120-118 https://www.faa.gov/documentLibrary/media/Advisory_Circular/AC_120-118.pdf

CAT I (FAA) An instrument approach operation with a minimum descent altitude (MDA), decision altitude (DA), or decision height (DH) not lower than 200 feet (60 m) and with either a visibility not less than ½ SM, or a Runway Visual Range (RVR) not less than 1800 feet (550 m).
CAT I (ICAO) Any precision approach and landing operation with a DA/H of 60 m (200 feet) or higher and with a minimum visibility of 550 m RVR or greater will be termed a Standard CAT I operation.

CAT II (FAA)
A precision instrument approach operation with a DH lower than 150 feet but not lower than 100 feet and a RVR not less than 1000 feet.
CAT II (ICAO)
Standard CAT II operations are made to a DA/H below 60 m (200 feet), but not lower than 30 m (100 feet), with associated RVRs ranging from 550m (1800 feet) to 300 m (1000 feet).

CAT III (FAA)
A precision instrument approach and landing operation with a DH lower than 100 feet (30 m) or no DH, or a RVR less than 1000 feet (300 m).
CAT IIIa (ICAO)
A precision instrument approach and landing operation with a DH lower than 30 m (100 feet) or no DH and an RVR not less than 175 m (600 feet).
CAT IIIb (ICAO)
A precision instrument approach and landing operation with a DH lower than 15m (50 feet) or no DH and an RVR lower than 175m (600 feet) but not less than 50m (200 feet).
CAT IIIc (ICAO)
A precision instrument approach and landing with no RVR limitations.

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  • Cat III A 600 feet (180 meters) Runway Visible Range (RVR)
  • CAT III B 150 feet (46 meters) RVR
  • CAT III C zero visibility

No decision height in any CAT III approach (CAT II is 100' and CAT I is 200')

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  • $\begingroup$ A Cat IIIA approach can have a 50' DH for operators that need one. Not sure how wide or narrow that set of operators is, though. $\endgroup$ – Ralph J May 9 '15 at 17:15
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    $\begingroup$ Also please note that specifications differ here between FAA and ICAO. These figures are FAA-figures (which may very will be what the OP wanted) $\endgroup$ – Waked May 11 '15 at 8:18
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    $\begingroup$ Quite. So I don't appreciate the negative vote! $\endgroup$ – nimbusgb May 12 '15 at 8:23
  • $\begingroup$ You may consider editing the answer to a more readable format. $\endgroup$ – kevin Jul 23 '15 at 6:29
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    $\begingroup$ There's also the Alert Height, Read more in FAA AC120-28. faa.gov/documentLibrary/media/Advisory_Circular/120.28C.pdf $\endgroup$ – Sports Racer Sep 29 '15 at 21:08

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