Reading ICAO Instrument Approach Charts

An instrument approach chart (IAC) is the graphic form of an instrument approach procedure as a State publishes it in its AIP. A chart normally presents one procedure: where to fly, how low to descend at each point, the minima for each category of aircraft, and what to do if the approach has to be abandoned.

The format follows ICAO Annex 4, and each State lists its differences from the Annex in GEN 1.7 of its AIP. The examples below come from approach charts in AIP France of 2024 to 2026, which show the ICAO conventions and a few national ones; they are not for navigation. The US layout is described in reading FAA instrument approach charts, and the design behind both in instrument approach procedures.

ICAO Annex 4 approach charts

ICAO Annex 4, Aeronautical Charts, sets the standards for the instrument approach chart, and the AIP places the charts of each aerodrome in its AD 2 section. In France, GEN 1.7 notes where the charts depart from Annex 4: ILS and localizer procedures may share one chart, procedures ending in a visual maneuver with prescribed track (VPT) have charts of their own, and the coordinates of the final approach fix and other essential points are listed in a separate table rather than on the chart.

Symbols are explained in the chart legend, GEN 2.3 in AIP France, and abbreviations in GEN 2.2. Some are national: API stands for missed approach and MVL for circling (visual maneuvering without prescribed track), while VPT is visual maneuvering with prescribed track. Charts are kept current by AIP amendment, with NOTAM covering changes in between, so the chart's date and the NOTAM are checked together.

The title names the final approach guidance and the runway, as in ILS Y / LOC Y RWY 14L at Toulouse Blagnac. Letters such as Y and Z tell apart procedures of the same type to the same runway, such as the RNP Y and RNP Z RWY 04L at Nice. The header also lists the aircraft categories for which the procedure is protected, for example CAT A B C D.

Header and communication data

The header gathers what is needed to set up the approach: the frequencies, at Toulouse Blagnac the ATIS on 123.130 MHz and the tower on 118.105 MHz, and a navaid box. On the ILS Y / LOC Y RWY 14L the navaid box reads ILS - DME, TG 108.9, so the ILS and its paired DME are identified TG on 108.9 MHz, and it also gives RDH 50, the ILS reference datum height of 50 ft. An RNP chart states the navigation specification and its requirements instead, such as RNP APCH with an RNAV holding function at Bordeaux, and for an LPV line the SBAS channel and the reference path identifier: EGNOS Ch 65065 E03A at Nantes. AIP France also gives the elevations of the aerodrome and of the threshold, rounded to the nearest foot, with the hectopascal equivalent of the chart's reference level, which converts QNH into QFE.

A boxed warning area carries the restrictions and cautions specific to the procedure. Typical entries are a prohibition, such as "Absence ATS: procedure prohibited" at Chambéry; a caution, such as spurious glide path signals before the final approach point at Toulouse; a box flagging a steep final, such as a non-precision final steeper than 6.5 percent for Categories A and B or 6.1 percent for C and D, which calls for appropriate aircraft and crew qualifications; and Baro-VNAV temperature limits on RNP charts.

Plan view and the MSA diagram

The plan view shows the procedure from above: the arrival tracks, the initial approach fix (IAF), the intermediate fix (IF) and the final approach fix (FAF), with magnetic tracks, distances and altitudes. Navaids used by the procedure are drawn in bold, and relief is shown from a contour at least 300 m above the aerodrome. Altitude constraints follow the legend: a figure underlined is a minimum ("at or above"), one with a bar above is a maximum ("at or below"), one with bars above and below is mandatory, and one with no bar is a recommended altitude.

Holding patterns are described in boxes. The course is the inbound track, the turns are to the right unless the box says left, and the outbound leg is limited by time or by DME. The RNAV hold at FUZAP, Toulouse, reads MAX IAS 220 kt, 213° Left, between 5000 ft and FL 070; the VOR-DME hold at NERAS, on the Nice VOR B RWY 22L/22R, reads 296° Right, 30 - 35 NM AZR, so the outbound leg ends at 35 NM. A figure in a shaded box is a minimum obstacle clearance altitude (MOCA), and an asterisk attaches a condition: at NERAS the underlined 4000* is the normal minimum holding altitude, and the asterisk leads to API 3000, so after a missed approach the hold may be flown at 3,000 ft. DME arcs end on a published radial, often with a speed limit for the turn that follows.

The minimum sector altitude (MSA) diagram gives the lowest altitudes for emergency use within 25 NM of a reference point, usually a navaid. AIP France calculates them with an obstacle clearance margin of 300 m, increased by up to 300 m over high terrain, and draws the sector boundaries as QDMs, magnetic tracks toward the reference point. Some diagrams add rings: at Toulouse 2,500 ft applies within 10 NM of TOU and 3,000 ft from 10 to 25 NM. Where sectors depend on DME, a diagram may also print a single figure for use without distance information, such as ALT MNM 25 NM: 6600 at Strasbourg. The MSA guarantees no navigation, radio or radar coverage (see minimum safe altitudes). RNAV procedures built in a T or Y layout may show terminal arrival altitudes (TAA) instead.

Profile view and the final approach segment

The profile view, below the plan view, shows the descent from the side, with the runway drawn as a bold line at the chart's reference level. Altitudes are followed by heights in brackets: 4000 (3511) is 4,000 ft on QNH and 3,511 ft above the reference. AIP France uses the threshold as reference for precision approaches and approaches with vertical guidance, and the aerodrome elevation for non-precision approaches unless the threshold lies more than 2 m (7 ft) below it. The transition altitude of the TMA is printed here too, 5000 ft at Toulouse; a descending aircraft changes to QNH at the latest when passing the transition level.

The final segment begins at the final approach fix or, for an ILS, at the final approach point (FAP), where the intermediate altitude meets the glide path. It is labeled with its angle and gradient, normally 3° or about 5.2 percent; the ILS or LOC RWY 05 at Strasbourg is steeper, at 3.5° and 6.1 percent. Distances are given on scales to the threshold and to a DME, and a stepdown fix allows a lower altitude once an obstacle is passed.

On a non-precision approach the missed approach point (MAPt), MAPT on French charts, is the point by which the missed approach must be started to keep the minimum obstacle clearance. It may be a DME distance, a waypoint or a navaid. The LOC Y MAPt at Toulouse lies at 1 NM DME TG, 0.8 NM before the threshold; the RNP RWY 03 at Nantes uses the waypoint RW03 and prohibits timing; the VOR Z RWY 07L at Toussus-le-Noble uses the TSU VOR overhead.

Tables near the minima box help fly the final: altitude and height at each DME distance, the time from FAF to MAPt at several groundspeeds, and the rate of descent, such as 710 ft/min at 130 kt on the 3.1° final of the RNP Y RWY 21 at Nantes.

Minima table: OCA/OCH and categories

The minima box sets out, for each type of approach (ILS, LOC, LPV, LNAV/VNAV, LNAV or circling), the minima of each aircraft category. The category is fixed by VAT, the threshold speed at maximum certificated landing mass:

An entry such as DA(H) 690 (200), RVR 550 m, the LPV line of the RNP RWY 14L at Toulouse, gives a decision altitude of 690 ft, its height of 200 ft and the minimum RVR in meters. Lines with vertical guidance (ILS, LPV, LNAV/VNAV) end at a DA(H); lines without it (LOC, LNAV, VOR, NDB and circling) end at an MDA(H).

French charts also print the obstacle clearance height (OCH), the lowest height at which the obstacle clearance criteria of the design are met; the OCA is the same limit as an altitude. The OCH varies with category, and the operating minimum may be higher but never lower. On the ILS or LOC RWY 35L at Lyon Saint-Exupéry, Category C has an OCH of 162 ft for CAT I and 75 ft for CAT II, yet the CAT I line reads DA(H) 1020 (200) with RVR 550 m, because a CAT I decision height may not be below 200 ft; the localizer line reads MDA(H) 1250 (430) with RVR 1300 m, against an OCH of 429 ft. Heights in the box are above the chart's reference level, and a box marked REF HGT: ALT AD gives them above the aerodrome.

Columns headed API 2.5%, API 3% and so on give minima for different missed approach climb gradients. AIP France checks the missed approach with 2.5 percent and always publishes those minima; lines for steeper gradients are lower. At Nice the ILS Y RWY 04L gives Category C 390 (380) with RVR 1700 m at 2.5 percent and 310 (300) with RVR 1400 m at 3 percent, and a remark requires public transport operations to account for an engine failure in the missed approach.

Circling, MVL on French charts, has its own columns with an MDA(H) and a visibility. Its restrictions appear as remarks rather than on the plan view, such as daytime only (HJ) and prohibited east of the runway at Ajaccio. Where no air traffic service is provided, an instrument approach is allowed only if a QNH is available from an automatic station or a station named on the chart, and it must end in circling, sometimes to higher minima: the VOR Z RWY 25R at Toussus-le-Noble gives Category C 1240 ft and 2400 m with ATS but 1410 ft and 3000 m without.

Missed approach and notes

The missed approach is described in words beside the profile and drawn in the plan view. On the ILS or LOC RWY 29 at Bordeaux it reads: climb straight ahead; at 700 (540), turn right 040° (MAX IAS 190 kt); do not turn before MAPT. Some charts add an altitude to reach before accelerating in level flight, 1400 ft on the VOR Z RWY 07L at Toussus-le-Noble, or a separate route to fly after a radio failure, as at Lyon.

AIP France protects the missed approach for a 2.5 percent climb up to the minimum acceleration height. Air traffic reasons can add a higher gradient: the Lyon ILS or LOC RWY 35L requires 5.4 percent up to 2,900 ft, and a crew unable to achieve it advises ATC. Separation from other tracks and airspace is checked with 3.3 percent, and a gradient is published only when it exceeds that figure, so in France a missed approach must achieve at least 3.3 percent unless the chart requires more (see go-around and missed approach).

Chart notes elsewhere complete the picture: "T° MNM -20°C" on the RNP RWY 14L at Toulouse, below which Baro-VNAV without temperature compensation may not be used (see cold-weather altimetry); "RNAV holding function required, entry on inbound leg only" at Chambéry; "VPT prohibited for turbofans if PAPI U/S" at Brest. Each can take away a line of minima or the whole procedure.

Differences from Jeppesen and FAA charts

FAA charts carry the same information in another layout: a briefing strip at the top, then the plan view, the profile, the minimums and an airport sketch. The conventions that differ most are:

Altitude bars are read the same way on both. Jeppesen and other commercial providers redraw each State's procedures in one uniform style, so a crew sees the same layout everywhere, but they are secondary sources: the AIP is authoritative, and a doubt about a commercial chart is settled against the State's chart and the current NOTAM.

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.