Aerodrome Charts and Airport Diagrams

An aerodrome chart is a plan of one aerodrome drawn for the pilot on the ground: its runways, taxiways, aprons, holding positions and buildings, with the data needed to get an aircraft from the stand to the runway and back. In ICAO States it is published in the aerodrome (AD) part of the AIP. In the United States the equivalent is the airport diagram, part of the FAA's Terminal Procedures Publication.

At a large aerodrome the chart is a safety tool: taxi clearances name a string of taxiways, holding points and runway crossings that must be found in the dark or in fog, and the places with a history or risk of runway incursions are marked on it as hot spots. The general families of charts are described in aeronautical charts; this article explains how to read the aerodrome charts themselves, with examples from AIP France and FAA diagrams that are not for navigation.

Aerodrome charts in the AIP

ICAO Annex 4, Aeronautical Charts, defines three charts for the aerodrome surface, each named with the suffix "ICAO":

• the Aerodrome Chart (ADC), titled Aerodrome/Heliport Chart in the current Annex, the basic chart of runways, taxiways, aprons and aerodrome data;
• the Aerodrome Ground Movement Chart (GMC), a separate plan for taxiing, with the taxi routes and the ground movement details that the aerodrome chart refers to;
• the Aircraft Parking/Docking Chart (APDC), a plan of the aprons and their stands.

Not every aerodrome needs all three: Chambéry publishes an aerodrome chart and a parking chart but no ground movement chart. AIP France GEN 3.2 lists the aerodrome chart at 1:10 000 and the other two at various scales. They belong to item AD 2.24, charts related to the aerodrome; in the PDF edition of AIP France they follow item AD 2.25. Toulouse Blagnac has one aerodrome chart, three parking charts and four ground movement charts. Visual arrivals use the separate visual approach charts. Commercial chart providers redraw the same State data in their own format, but the AIP remains the reference.

Each State lists its departures from Annex 4 in GEN 1.7. France, for example, does not print the annual change of magnetic variation on its aerodrome charts and draws no magnetic north arrow; true north is the top of the sheet, parallel to its left edge, unless an arrow shows otherwise. The Lyon Saint-Exupéry chart carries such an arrow, because it is drawn with north pointing to the left. Charts are kept current by AIP amendment and, in between, by NOTAM, so a closed taxiway or a moved holding point may exist only in the NOTAM.

Aerodrome data: ARP, elevation and variation

The header of the aerodrome chart repeats the main entries of AIP section AD 2.2, with the ground frequencies. On the Toulouse Blagnac chart it reads:

The aerodrome reference point (ARP) is the designated geographical location of the aerodrome, normally near its geometric center. It is a horizontal position: AD 2.2 gives its coordinates and its direction and distance from the city served (3.6 NM WNW of Toulouse), and charts use it as the origin of bearings and distances, as on the Megève visual chart, where reporting point N lies "320° 1.6 NM ARP".

The aerodrome elevation is a separate figure: the elevation of the highest point of the landing area. Threshold elevations are printed beside each runway end, and AD 2.2 adds the aerodrome reference temperature (27 °C at Toulouse), the exact variation (1.6594° E) and its annual change. The geoid undulation matters to satellite navigation, which measures height above the WGS-84 ellipsoid rather than above mean sea level (see GNSS).

Runway and taxiway depiction

Runways are drawn to scale with their designators, dimensions (4000 x 45 m and 2670 x 45 m at Lyon), thresholds, displaced thresholds, stopways and clearways; in the French legend a clearway is a dashed outline beyond the runway end and a stopway a solid one. Navaid sites are marked with their frequencies, such as the localizer, glide path and DME of each ILS, and the PAPIs with their angle and minimum eye height over the threshold (MEHT).

Below the plan, a French aerodrome chart carries a runway table, one line per runway direction:

• threshold coordinates, to a hundredth of a second of arc;
• approach and runway lighting;
• the declared distances TORA, TODA, ASDA and LDA;
• surface and strength, such as PCN 101 F/A/W/T for Lyon's longer runway;
• minimum takeoff RVR for each aircraft category.

The declared distances show the layout at a glance. At Lyon all four distances for runway 17R are 4000 m, so it has no clearway, no stopway and no displaced threshold. The takeoff minima are read across by category: 550 m for every category on runways 17R and 17L, but 125 m on 35L and 35R, the runways a note clears for low-visibility takeoffs below 125 m. Notes change the figures, as at Chambéry, where a footnote raises the runway 36 minimum from 400 m to 800 m when air traffic services are not provided. How the distances are defined is covered in declared distances.

Taxiways are drawn with their designators, often a letter and a number, such as M2, P20 or T40 at Toulouse. AD 2.8 gives their widths and strengths (25 m for many of the Toulouse taxiways), and the chart shows closed areas and temporary taxiways.

Holding points, stop bars and hot spots

The chart symbols for the runway entrances matter most. The French legend in GEN 2.3 and the key printed on each chart distinguish:

• runway-holding points, with separate symbols for CAT I and CAT II/III positions;
• intermediate holding points (PAI), at taxiway intersections rather than runway entrances;
• stop bars, rows of red lights across the taxiway, marked P (permanent) or C (controlled) on the Lyon and Toulouse charts, the controlled ones being remote controlled, as the Lyon AD 2.9 puts it;
• no-entry bars, drawn in red and marked I, as across the Lyon exit taxiways V4 and V6.

The markings and lights themselves are described in aerodrome markings and signs and aerodrome lighting and visual aids.

A hot spot is a place on the movement area where surface incidents such as runway incursions have happened or are likely. The FAA Chart Users' Guide adds that it is typically a complex or confusing junction of two taxiways or of a taxiway and a runway, where a misunderstanding between controller and pilot can compromise separation. Charts circle it and label it HS 1, HS 2 and so on; the reason is given in a note on the French charts and on the hot spot page of the FAA's Terminal Procedures Publication. The Toulouse aerodrome chart only marks them and refers to the ground movement chart, whose caution box explains each one: at HS 1 an aircraft leaving the E, F or K parking areas via taxiway T40 risks entering the runway if the pilot misses taxiways P20 or P40; at HS 2 and HS 4 a taxiway leaving runway 14R leads straight onto runway 14L after a short taxi.

Ground movement charts and taxi routes

Where a ground movement chart exists, it is the chart to brief from. It strips out the runway data and shows the standard taxi routes. At Toulouse, GMC 01 covers the runway 14 configuration outside low visibility procedures (LVP) and GMC 02 the runway 32 configuration, with the arrival routes dashed in magenta and the departure routes in blue; GMC 03 gives the routes for runway 14R in LVP, and GMC 04 classifies the taxiways by aircraft code, from code C (36 m wingspan) to code F (80 m). Lyon publishes its routes for the Antonov An-124, Airbus A380 and Boeing 747-8 on separate charts.

A clearance that matches a standard route is easy to follow; one that departs from it is a cue to stop and check the chart before moving. The taxiing and runway incursion prevention article covers the briefing and the readback of hold-short instructions.

Aprons, stands and parking charts

The aircraft parking/docking chart shows each apron with its stands, their numbers and limits. At Toulouse it marks the stand positions, intermediate holding points on the apron, stands managed by the operator and a temporary taxiway opened by the aerodrome operator, and it limits stands by wingspan: 16 m on stands G20 to G26, 21 m on G30 to G32 and 30 m on G40.

Supporting data are in the AD 2 text. AD 2.8 lists the INS checkpoints, the stand coordinates to a hundredth of a second, against which an inertial position set at the stand can be checked, and the altimeter check location: at Toulouse the passenger and freight aprons, at a mean elevation of 488 ft. AD 2.9 describes the stand guidance; Toulouse has no visual docking guidance system, so a marshaler is mandatory on every stand. Apron and aerodrome design rules, such as the clearances around a stand, are in aerodrome physical characteristics.

FAA airport diagrams

The FAA airport diagram is designed to help ground movement at airports with complex runway and taxiway layouts. According to the FAA Chart Users' Guide it is not intended for approach, landing or departure, and helping pilots identify their position reduces requests for progressive taxi instructions. The diagrams are in the Terminal Procedures Publication, and the Chart Supplement also carries diagrams for selected towered airports (see FAA Chart Supplement).

The Chart Users' Guide lists what a diagram shows, including:

• runways with their magnetic headings, the magnetic variation and its epoch year, dimensions, displaced thresholds, runway end elevations and surface;
• weight-bearing capacity by landing gear configuration or a pavement classification, and arresting gear including EMAS beds;
• land and hold short lines, ILS hold lines and localizer and glide slope critical areas;
• taxiways with identifiers, hot spots, parking areas, run-up pads and non-movement areas, where the pilot is not under air traffic control;
• the control tower, airport beacon, navaids and frequencies, a star marking part-time ones.

The legend adds details often examined. Runway length is the physical length end to end, including displaced thresholds but excluding stopways. Runway slope is shown when it rounds to 0.3% or more, with an arrow toward the higher end. A white D in a black box means declared distances exist and are listed in the Chart Supplement. Field elevation is the highest point of the usable runways, leadered to that spot. Positions are accurate to within 600 ft unless the chart says otherwise, and scale and orientation vary from diagram to diagram.

The Boeing Field (BFI) diagram in Seattle shows these in practice: runway 14R-32L is 10,007 x 200 ft and 14L-32R 3,709 x 100 ft, both on 135° and 315° magnetic; the field elevation is 22 ft; the variation is 15° E as of January 2020, changing by 0.1° W a year; HS 1 to HS 3 are circled in brown; and the tower frequency depends on the runway, 118.3 MHz for 14L-32R and 120.6 MHz for 14R-32L and all IFR traffic. Notes in the margin warn "Be alert to runway crossing clearances" and require readback of all runway holding instructions, and a general note asks for transponders in altitude reporting mode and ADS-B on all airport surfaces, as AIM 4-1-20 recommends.

The differences from the ICAO charts are mostly of style. FAA diagrams give runway dimensions in feet and leave declared distances and takeoff minima to other publications; French aerodrome charts give dimensions in meters, carry declared distances and takeoff minima in the runway table, and put the taxi routes on ground movement charts. Both mark hot spots.

Using the charts on the ground

Whatever the format, the chart is used before the aircraft moves. The FAA's Pilot's Handbook of Aeronautical Knowledge advises carrying a current airport diagram and tracing the taxi route to the departure runway before leaving the ramp. The crew briefs the route, its runway crossings and hot spots, and checks the clearance against the chart and the NOTAM. When in doubt, the pilot stops and asks, or requests progressive taxi instructions.

Library articles are written for study and exam preparation. They do not replace your aircraft's approved documentation, your operator's procedures or the regulations themselves.