Aerodrome reference code (Annex 14 §1.6)
Why is one aerodrome allowed to handle an A380 while another may only accept light singles? The answer lies in the aerodrome reference code, the classification system of ICAO Annex 14 Vol I that links the physical characteristics of an aerodrome to the aeroplanes intended to use it. For the PPL exam you need to know how the two code elements are derived and be able to assign a code to a given aircraft.
The two code elements
The reference code matches aerodrome facilities to the most demanding aeroplane the aerodrome is intended to serve. It consists of:
- Code number (element 1) — derived from the aeroplane's required field length.
- Code letter (element 2) — derived from the aeroplane's wingspan.
Code number: aeroplane reference field length (ARFL)
The aeroplane reference field length (ARFL) is the minimum field length required for take-off at maximum certificated take-off mass, sea level, ISA standard atmosphere (15 °C), zero wind and zero runway slope. It is a property of the aeroplane, taken from its flight manual, and it determines the code number:
| Code number | ARFL |
|---|---|
| 1 | < 800 m |
| 2 | 800 m to < 1 200 m |
| 3 | 1 200 m to < 1 800 m |
| 4 | ≥ 1 800 m |
Code letter: wingspan
The code letter is determined by wingspan alone:
| Code letter | Wingspan |
|---|---|
| A | < 15 m |
| B | 15 m to < 24 m |
| C | 24 m to < 36 m |
| D | 36 m to < 52 m |
| E | 52 m to < 65 m |
| F | 65 m to < 80 m |
Note: older editions of Annex 14 also used the outer main gear wheel span (OMGWS) — the distance between the outside edges of the main gear wheels — to determine the code letter (the "higher of the two values" rule). Since the 2019/2020 amendment of ICAO Annex 14 Vol I (mirrored in CS-ADR-DSN) this is no longer the case: the code letter is based on wingspan only, and OMGWS is a separate classification parameter used for the design of the ground-manoeuvring area, for example runway and taxiway widths.
Worked examples
| Aircraft | Wingspan | ARFL | Reference code |
|---|---|---|---|
| Cessna 172 | ~11 m | ~400 m | 1A |
| Airbus A320 | ~36 m | ~2 100 m | 4C |
| Boeing 747 | ~64 m | ~3 000 m | 4E |
| Airbus A380 | ~80 m | ~3 000 m | 4F |
A typical small VFR aerodrome designed for light aircraft is therefore code 1A or 2B — which is exactly why you cannot expect wide taxiways, large runway strips or heavy-jet clearances there.
What the code is used for
The reference code drives the minimum design dimensions of the aerodrome: runway width and strip dimensions, taxiway separation, obstacle limitation surfaces, lighting standards and more (Annex 14, Chapters 3 and 5). It is a design and planning tool — it does not by itself prohibit a particular aircraft from landing, but an aerodrome is only guaranteed to meet the safety margins for aircraft up to its code.
Europe and Germany
In the EU the reference code is applied through Regulation (EU) No 139/2014 (Part-ADR) and CS-ADR-DSN Book 1, Subpart B (Aerodrome Reference Code), which mirror ICAO Annex 14. The AIP Germany, AD section publishes the code for each certified aerodrome — for example Frankfurt 4E and Munich 4F, while small VFR aerodromes are typically 1A or 2B.
Exam essentials
- The aerodrome reference code consists of a code number (1–4) and a code letter (A–F).
- The code number is based on the aeroplane reference field length (ARFL): 1 < 800 m, 2 = 800–< 1 200 m, 3 = 1 200–< 1 800 m, 4 ≥ 1 800 m.
- ARFL is the minimum take-off field length at MTOM, sea level, ISA, zero wind and zero slope.
- The code letter is based on wingspan alone: A < 15 m, B < 24 m, C < 36 m, D < 52 m, E < 65 m, F < 80 m.
- OMGWS (outer main gear wheel span) no longer determines the code letter; it is a separate parameter used for ground-manoeuvring area design.
- Typical examples: Cessna 172 = 1A, A320 = 4C, B747 = 4E, A380 = 4F.