Aerodromes, Ground Operations and Local Procedures
Aerodrome layout and signals
ICAO Annex 14 and the State AIP define runway markings, taxiway markings, signs and signals. Runway holding position markings protect the runway strip. A runway incursion is any unauthorised presence on a runway. Mandatory instruction signs are red with white inscription; information signs are yellow with black inscription. The windsock gives surface wind; a fully extended sock indicates roughly 15 kt or more.
Light signals
If radio fails, the tower may use light signals. Steady green to an aircraft on the ground means cleared for take-off; flashing green means cleared to taxi. Steady red means stop; flashing red means taxi clear of the runway or aerodrome unsafe; alternating red and green means danger and requires action. The pilot must acknowledge signals as required and must not assume a green light is a taxi clearance when it is steady.
Worked example
After radio failure, an aircraft on a taxiway receives a steady green light from the tower. The pilot must not continue taxiing: steady green on the ground means cleared for take-off. If the tower intended to allow taxiing, it should give a flashing green. The pilot stops, confirms position, and proceeds only when the signal is unambiguous.
Traps
Do not confuse steady and flashing green. A red light is not 'give way and continue'; it is stop. A marshaller's signal is not an ATC clearance. Do not enter a runway at a holding point without clearance even if the runway appears clear. Local procedures and hot spots are published in the AIP and aerodrome charts.