This is a compiled write-up by Seeshas Ro, about the basics of Aircraft Approach Classification and Aerodrome Reference Code You need to Know as a Fight Student.
For approach, aircraft are classified in categories: A, B, C, D, and E. The criteria are taken into consideration for the classification of airplanes by categories is the indicated airspeed at threshold (VAT) in landing configuration at the maximum certified landing weight.
These categories are as follows: (Speed)
Category A: Speed less than 91 knots
Category B: Speed 91 knots or more but less than 121 knots
Category C: Speed 121 knots or more but less than 141 knots
Category D: Speed 141 knots or more but less than 166 knots
Category E: Speed 166 knots or more
There are some who would argue that maximum certificated weight only applies to 1.3VSO based on the placement of a comma in the regulation. The debate raged on for decades but the FAA finally provided some clarity in 2013.
ICAO distinguishes approaches operations based on DH between ‘Type A’ (DH >= 250 ft) and ‘Type B’ (DH < 250 ft), which are further divided into subcategories. From the Annex 6 — Operation of Aircraft Part I:
- a) Type A: a minimum descent height or decision height at or above 75 m (250 ft); and
- b) Type B: a decision height below 75 m (250 ft). Type B instrument approach operations are categorized as:
Category I (CAT I): a decision height not lower than 60 m (200 ft) and with either a visibility not less than 800 m or a runway visual range not less than 550 m.
Category II (CAT II): a decision height lower than 60 m (200 ft) but not lower than 30 m (100 ft) and a runway visual range not less than 300 m.
Category IIIA (CAT IIIA): a decision height lower than 30 m (100 ft) or no decision height and a runway visual range not less than 175 m.
Category IIIB (CAT IIIB): a decision height lower than 15 m (50 ft) or no decision height and a runway visual range of fewer than 175 m but not less than 50 m.
Category IIIC (CAT IIIC): no decision height and no runway visual range limitations.
Instrument approach procedures are further classified as follows:
1) Non-precision approach (NPA) procedure. An instrument approach procedure designed for 2D instrument approach operations Type-A.
2) Approach procedure with vertical guidance (APV). Performance-based Navigation (PBN) instrument approach procedure designed for 3D instrument approach operations Type-A.
3) Precision approach (PA) procedure. An instrument approach procedure based on navigation systems (ILS, MLS, GLS, and SBAS CAT I) designed for 3D instrument approach operations Type A or B.
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Aerodrome Reference Code (Basic)
The ICAO Aerodrome Reference Code is a two-part categorization of aircraft types which simplifies the process of establishing whether a particular aircraft is able to use a particular aerodrome.
It is included in ICAO Annex 14. It has two ‘elements’, the first is a numeric code based on the Reference Field Length for which there are four categories and the second is letter code based on a combination of aircraft wingspan and outer main gear wheel span.
According to ICAO Annex 14 Volume 1 – or national implementation thereof, as well as EASA regulations for Airports in Europe – each Aerodrome is assigned an “Aerodrome Reference Code”. As per the 8th edition of Annex 14, such a reference code is based on critical aircraft’s “Reference Field Length” (first code number) and aircraft wingspan (second code letter). For instance, an Aerodrome with a reference code 4E can accommodate aircraft with a “Reference Field Length” of 1800m and above and a wingspan up to 65m.