Aerodrome Markings and Signs

Aerodrome markings are painted on the pavement; aerodrome signs stand beside it. Together they are the pilot's road signs on the ground: they identify the runway ahead, show where the landing distance begins, lead the aircraft along the taxiways and, above all, mark the places where it must stop and wait for a clearance. Misreading them is a classic first step towards a runway incursion (see taxiing and runway incursion prevention).

The system rests on a few colour rules, set in ICAO Annex 14 and followed, with some differences, by the FAA. Runway markings are white. Taxiway and aircraft stand markings are yellow, and either may be outlined in black on a light-coloured surface to stand out. Among the signs, red is reserved for mandatory instructions, always with a white inscription, while information signs are yellow and black. Numbers alone always mean a runway: taxiways are designated by letters, or letters followed by numbers, and the letters I, O and X are avoided so that they cannot be confused with 1, 0 and the closed marking.

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Runway designation and centre line

The runway designation marking is a two-digit number: the whole number nearest to one-tenth of the runway's magnetic direction, seen from the approach. A runway on 094° magnetic is runway 09; one on 268° is runway 27, and its other end, on 088°, is runway 09. Some States omit the leading zero.

Parallel runways carry a letter: L and R for two, L, C and R for three, left to right as seen from the approach. With four parallel runways, one pair takes the next number: 09L, 09R, 10L and 10R. The FAA follows the same scheme.

The runway centre line marking is a line of uniformly spaced white stripes and gaps between the designation markings at each end. A stripe and a gap together measure not less than 50 m and not more than 75 m, and each stripe is at least as long as the gap, or 30 m, whichever is greater.

Threshold and displaced threshold

The threshold marking, the familiar "piano keys", is a row of longitudinal white stripes that begins 6 m from the threshold. The stripes are at least 30 m long, and their number depends on the runway width:

When a threshold is permanently displaced, a transverse white bar is painted across the runway at the new threshold, and white arrows on the part of the runway before it point towards the threshold. That part is still runway: it may be used for taxiing, for the take-off run and for the landing roll of aircraft landing from the opposite direction, but an aircraft landing towards the bar must not touch down before it. French national rules mark a displaced threshold with one to three V-shaped marks instead.

Paved ground before a threshold that is not fit for normal use by aircraft is marked differently. Where such a pre-threshold area is more than 60 m long, it is marked along its whole length with yellow chevrons pointing towards the runway. The FAA uses the same yellow chevrons on a blast pad or stopway, and no taxiing, take-off or landing is allowed on it.

Aiming point, touchdown zone and distance markings

The aiming point marking, two broad white rectangles either side of the centre line, gives the pilot a visual aiming point for landing. Annex 14 requires it at each approach end of a paved instrument runway of code 2, 3 or 4, and places it further from the threshold on longer runways:

Touchdown zone markings are pairs of rectangular white marks either side of the centre line, spaced 150 m apart starting from the threshold, on paved precision approach runways of code 2, 3 and 4. On a runway with 2,400 m or more of landing distance there are six pairs; a pair that would fall within 50 m of the aiming point is left out. In the United States the aiming point marking is about 1,000 ft from the threshold, and the touchdown zone markings are groups of one, two or three stripes every 500 ft.

Fixed distance markers, found mainly at military aerodromes, are white numbers on a black background at 1,000 ft intervals along the runway, counting down the distance remaining. The FAA's runway distance remaining signs work the same way: a white 3 on a black background means about 3,000 ft of runway remain.

Closed runways and taxiways

A closed marking is placed at least at each end of a closed runway or taxiway, or of the closed portion, and on a runway no more than 300 m apart. It is white on a runway and yellow on a taxiway. When a runway or taxiway is closed permanently, all its normal markings are obliterated and its lights are not operated except for maintenance. The FAA marks a closed runway with yellow X symbols at each end.

Runway-holding positions

A runway-holding position protects the runway: it keeps a holding aircraft far enough from the runway not to endanger aircraft using it and, where needed, clear of the ILS critical and sensitive areas. Its distance from the runway centre line depends on the runway type and code number:

For code F aeroplanes the distance on a precision approach runway rises to 107.5 m. In low visibility, holding positions for Category II and III operations are further out still, because an aircraft close to the localiser or glide path antennas can reflect or block their signals and bend the beams (see instrument landing system).

The runway-holding position marking comes in two patterns. Pattern A, two solid and two dashed yellow lines across the taxiway, marks the holding position closest to the runway. Where there are several holding positions on the same taxiway, those further out use pattern B. The solid lines of pattern A face the taxiway: an aircraft told to hold short stops before them, and no part of it may pass them without a clearance. The dashed lines face the runway: an aircraft leaving the runway has vacated it only when all of it is beyond the marking, which is why "runway vacated" is reported only then.

Other holding markings are:

• the intermediate holding position marking, a single broken yellow line where two taxiways meet;
• the mandatory instruction marking, a painted equivalent of a mandatory sign, white on a red background, used where a sign would be impracticable; it is not passed without a clearance;
• in the United States, the ILS critical area holding position, a ladder-shaped yellow marking with a red sign reading ILS, where aircraft stop only when ATC instructs them to hold short of the ILS critical area.

Places on the aerodrome where incursions have happened, or are likely, are shown as hot spots on aerodrome charts: on the Nantes Atlantique visual approach chart, for example, hot spot HS 2 warns of the risk of confusing taxiways RC and C and makes a complete readback mandatory. FAA airport diagrams mark them with a circled HS.

Taxiway markings and markers

The taxiway centre line marking is a continuous yellow line. It gives continuous guidance from the runway centre line to the point where the aircraft stand markings begin, and is required on paved taxiways where the code number is 3 or 4. Enhanced taxiway centre line markings, which warn of an approaching runway-holding position, are used in some States; the EU rules do not make them mandatory. In the United States, taxiway edges are marked by double yellow lines, both solid or both dashed, and the edge of the non-movement area, where ATC does not control taxiing, by one solid and one dashed yellow line, the dashed line on the movement side.

Where lights are not provided, markers do the same job:

• taxiway centre line markers are reflective green and are built to be run over by aircraft wheels;
• taxiway edge markers are reflective blue and frangible;
• boundary markers, in orange or red, or two contrasting colours, outline a landing area that has no runway, at intervals of not more than 200 m.

Apron and stand markings

On the apron, aircraft stand markings are yellow: the stand identification, lead-in line, turn bar, alignment bar, stop line and lead-out line. Apron safety lines, which show where ground equipment and vehicles may stand clear of aircraft, are in a colour that contrasts with the stand markings; if all equipment is parked behind them, a pilot or marshaller can concentrate on the stand markings alone. Many stands also have a visual docking guidance system that steers the pilot onto the stop position.

Mandatory instruction signs

A mandatory instruction sign has a white inscription on a red background. It marks a place that must not be passed without a clearance:

• the runway designation sign and runway-holding position sign, giving the runway designation, with each designator on the side of its own threshold as seen from the sign, as in 12-30;
• the Category I, II or III holding position sign, at the holding position for that category of operation;
• the road-holding position sign, where a vehicle road meets a runway, telling drivers to stop and obtain a clearance;
• the NO ENTRY sign, a white circle crossed by a horizontal bar on red in the FAA version, which forbids entry to an area.

At a towered aerodrome the pilot holds at a runway-holding position sign until cleared to enter or cross. At a non-towered US airport the pilot holds until satisfied that the runway and its final approach are clear.

Information signs

Information signs use yellow and black:

Direction signs are grouped around the location sign, with left turns on its left and right turns on its right. A common memory aid for the colour code is "black square, you're there; yellow array, points the way". An intersection take-off sign reading 2340M with an arrow gives 2,340 m of take-off run available from that point, a figure the crew must check against the performance requirements before accepting the intersection. French intersection take-off signs omit the letter m.

All signs are rectangular with the longer side horizontal, frangible, and mounted low enough to clear propellers and engine pods. They are illuminated when intended for use in runway visual range below 800 m, at night with instrument runways, or at night with non-instrument runways of code 3 or 4, and are otherwise reflective. The lights that complement them at night and in low visibility, from taxiway centre line lights to stop bars, are described in aerodrome lighting and visual aids.

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.