An aerodrome speaks to pilots in three visual languages: the indicators and ground signals of the pre-radio age that still work when everything else fails, the painted markings that organise the pavement, and the lights that carry the whole system into night and low visibility. This lesson teaches all three, from the windsock to the inner 300 metres of a CAT III approach lighting system, because the exam expects a pilot to read every one of them at a glance.
Indicators and signalling devices
An aerodrome shall be equipped with at least one wind direction indicator, located so that it is visible from aircraft in flight or on the movement area, and free from the effects of air disturbance caused by nearby objects. It is a truncated cone of fabric, at least 3.6 m long and at least 0.9 m in diameter at the larger end, giving the wind's direction and a general indication of its speed. A single colour is preferred; where two are needed for conspicuity, preferably orange and white, red and white, or black and white, in five alternate bands with the darker colour first and last. At an aerodrome used at night the indicator is illuminated, and the location of at least one should be marked by a circular band 15 m in diameter and 1.2 m wide, preferably white, centred on the support.
The landing direction indicator, where provided, sits in a conspicuous place and has the form of a 'T', coloured white or orange against its background, illuminated or outlined in white lights when used at night. Landings are made parallel to the shaft of the T, toward the cross-arm. And a controlled aerodrome's tower holds a signalling lamp: capable of producing red, green and white signals, of being aimed manually at any target, of giving a signal in one colour followed by either of the other two, and of transmitting messages in any of the three colours in Morse code, at up to at least four words per minute, the radio-failure channel every licence holder once memorised light signals for.
For aerodromes communicating with aircraft by ground signals (typically where there is no tower or AFIS, or for aircraft without radio), a signal area is provided: an even horizontal surface at least 9 m square, visible from all directions above 10 degrees when viewed from 300 m, surrounded by a white border and coloured to contrast with the signals displayed in it. The signals themselves are the pre-radio vocabulary of the rules of the air, and interpreting them is a learning objective:
A red square panel with yellow diagonals — landings are prohibited, and the prohibition is liable to be prolonged.
A red square panel with ONE yellow diagonal — special precautions must be observed in approaching or landing, owing to the bad state of the manoeuvring area or other cause.
A white dumb-bell — aircraft are required to land, take off and taxi on runways and taxiways ONLY.
A white dumb-bell with black bars across each circular portion — land and take off on runways only, but other movements need not be confined to runways and taxiways.
A horizontal white or orange landing T — land or take off parallel to the shaft of the T, toward the cross-arm.
A two-digit number displayed at the tower — the take-off direction, in tens of degrees magnetic, rounded to the nearest ten.
A right-hand arrow of conspicuous colour — turns are to be made to the right before landing and after take-off: a right-hand circuit.
A black letter C on a yellow background — the place where a visiting pilot reports to the ATS, or aerodrome, reporting office.
A white double cross — glider flying is in operation.
Markings: the painted vocabulary
The colour code comes first, because it sorts every marking at a glance: runway markings are WHITE; taxiway markings, runway turn pad markings and aircraft stand markings are YELLOW; and apron safety lines are of a conspicuous colour contrasting with the stand markings, commonly red. On light-coloured pavement, markings may be outlined in black for contrast.
The runway designation marking is provided at the thresholds of a paved runway (and as practicable on unpaved ones): a two-digit number, the whole number nearest one-tenth of the magnetic North azimuth of the runway centre line, viewed in the direction of approach. The layouts follow the number of parallels: a single runway carries the number alone; two parallels add L and R; three add L, C and R; more than three parallels are split across adjacent tens (25L/25R alongside 26L/26R) so no letter beyond L, C and R is ever needed.
The applications and general characteristics of the working markings, in the order the syllabus lists them:
Runway centre line marking — a line of uniformly spaced white dashes along the centre line of every paved runway.
Threshold marking — the longitudinal "piano key" stripes beginning at the threshold; the number of stripes grows with runway width, and a displaced threshold gains arrows leading to it along the portion before it: closed to landings, though the pavement itself may remain usable.
Touchdown zone marking — pairs of white rectangular blocks arranged symmetrically about the centre line of instrument runways, their count set by the landing distance available, marking where the wheels belong.
Runway side stripe marking — continuous white lines along the runway edges where the runway does not contrast well with its surroundings.
Taxiway centre line marking — a continuous yellow line, from the runway to the stands, including the curved lead-off and lead-on paths.
Runway-holding position marking — across the taxiway at every runway-holding position: pattern A, two solid and two dashed yellow lines, the solid pair on the side from which the runway is approached; pattern B, the yellow "ladder": where two or three holding positions protect a precision approach runway, the position closest to the runway wears pattern A and the farther position(s) pattern B.
Intermediate holding position marking — a single dashed yellow line across the taxiway.
Aircraft stand markings — the yellow lead-in, turn and stop lines that steer an aircraft onto its stand.
Apron safety lines — the conspicuous contrasting lines (wing-tip clearance lines, service road boundaries) that fence the ground equipment world away from the aircraft.
Road-holding position marking — the hold line across a road where it meets a runway, in accordance with the local road traffic rules.
Mandatory instruction marking — white inscription on a red background painted on the pavement, carrying a mandatory sign's message where installing the sign is impracticable, or reinforcing it.
Information marking — an inscription matching the sign it stands in for: yellow on black where it replaces a location sign, black on yellow where it replaces a direction or destination sign; painted where the sign would normally stand but cannot, or where it needs reinforcing.
Lights: safety by design, and the beacon
Before any beam matters, the fittings themselves must not be the hazard: elevated approach lights and their supports, and elevated runway, stopway and taxiway lights, shall be frangible (breaking away when struck), and the runway, stopway and taxiway fittings low enough to preserve clearance for propellers and for the engine pods of jet aircraft. An aeroplane that clips a light fitting should lose the fitting, not the wing.
An aerodrome beacon is provided at an aerodrome intended for use at night where one or more of three conditions holds: aircraft navigate predominantly visually; reduced visibilities are frequent; or the aerodrome is difficult to locate from the air against surrounding lights or terrain. It stands on or adjacent to the aerodrome in an area of low background lighting, and shows coloured flashes alternating with white flashes, or white flashes only, at 20 to 30 flashes per minute, the coloured flashes green at a land aerodrome (yellow at a water aerodrome).
Approach lighting: from simple to CAT III
A simple approach lighting system serves non-instrument runways of code 3 or 4, and non-precision approach runways, where physically practicable: a row of lights on the extended centre line extending at least 420 m from the threshold, with a crossbar 18 m or 30 m long at 300 m from the threshold, enough to give a visual line-up cue and a distance reference, no more.
A precision approach category I lighting system extends the ladder: a centre line of lights running 900 m from the threshold, with a crossbar at 300 m. In the distance-coded versions, the centre line's appearance changes with distance so the crew can read how far from the threshold they are. For category II and III systems the outer 600 m is essentially the CAT I picture, and everything that matters concentrates in the inner 300 m: the centre line becomes barrettes of white lights, flanked by two rows of red side barrettes, with crossbars at 150 m and 300 m from the threshold, a dense, redundant pattern built for the last seconds of an approach flown to minimal or no decision height, where a single failed lamp must never matter.
The visual glide path belongs to the precision approach path indicator (PAPI): a wing bar of four sharp-transition units on the left side of the runway (unless that is physically impracticable; a second bar on the other side only where visual roll guidance is needed), read by counting colours: on slope, two red and two white; slightly high, three white; well high, four white; slightly low, three red; well low, four red. Red means dead, white means high, and two-and-two means the glide path. The abbreviated PAPI (APAPI) is the two-unit version for smaller runways: on slope, one red and one white; high, two white; low, two red.