Aerodromes - Visual Aids, Markings and Signs — Page 411, Lesson 558

We're starting a fresh topic now: visual aids, markings, and signs at aerodromes. We've covered the physical layout of runways and taxiways; now we're getting into the language of the pavement — the signs that tell a pilot exactly where they are and what they must do. Let's begin with mandatory instruction signs. These are the signs you must obey — they mark a point where you cannot proceed without clearance. Their characteristics are very specific: they consist of white letters or numbers on a red background. That red background is your immediate cue that this is a command, not a suggestion. The inscription on these signs depends on what they're marking. A runway designation sign simply shows the runway designator — for example, "27" for Runway 27. Now, for instrument approach holding positions, the sign gets more detailed. If it's a Category I, II, or III, or a joint II/III instrument approach holding position sign, the inscription is the runway designator followed by the category — so you'd see "27 CAT I," "27 CAT II," "27 CAT III," or "27 CAT II/III" as appropriate. This tells you which category of instrument approach you're holding short of. Then there's the taxi-holding position sign. Its inscription consists of the taxiway designation and number — for example, "B2." This marks where you hold before entering a runway from a taxiway. Now, let me walk you through the variations shown in the figure. There's a visual holding point with a single digit alternative — that's the "010 – 090" you see, used when the holding point is for visual operations only. Then there's the CAT I instrument holding point, marked "CAT I," and the CAT I/II/III instrument holding point, marked "CAT I II III." There's also an intermediate taxi-holding point — that's a holding position on a taxiway, not at a runway. And you'll see a "No Entry" sign — that's self-explanatory, a mandatory prohibition. Look at the example "09-27" — that's a runway designation sign for a runway oriented 09/27. And "15-APCH" — that's a taxi-holding point where approach to Runway 15 passes over the taxiway. The "ILS" sign may be used at a holding point instead of the CAT I II III signs — it indicates the ILS critical area. And "9" with "9-27" shows the single-digit alternative. Now, let's move to information signs, covered in paragraph 20.40. These are provided where there's an operational need to identify a specific location or routing — direction or destination. They include direction signs, location signs, destination signs, runway exit signs, and runway vacated signs. Where are they placed? Wherever practicable, they're located on the left-hand side of the taxiway. At a taxiway intersection, information signs are placed before the intersection and in line with the taxiway intersection marking. Runway exit signs are located on the same side of the runway as the exit — so if the exit is on the left, the sign is on the left. Now, a runway vacated sign is located on at least one side of the taxiway to indicate when the aircraft is clear of the sensitive area — that's the ILS critical area. There's a specific stacking rule: where a runway vacated sign and a taxiway location sign are sited together, the taxiway location sign is outboard of the runway vacated sign — meaning further from the runway. Similarly, a taxiway location sign installed with a runway designation sign is positioned outboard of the runway designation sign. And importantly, an information sign other than a location sign shall not be collocated with a mandatory instruction sign — you don't mix a command with an informational sign at the same spot. Now the characteristics, paragraph 20.41. The colour scheme is critical. Information signs, except location signs, consist of an inscription in black on a yellow background. But location signs are the reverse: an inscription in yellow on a black background, and if it's a stand-alone sign, it has a yellow border. The inscription on a runway exit sign consists of the designator of the exit taxiway and an arrow indicating the direction to follow. And the inscription on a runway vacated sign depicts the pattern of the 'A' taxi-holding position marking — that's the pattern you see painted on the pavement. So to summarise the key contrasts: red background means mandatory — you must stop. Yellow background with black letters means information — direction, destination, exit. Black background with yellow letters means location — where you are. And the runway vacated sign uses the 'A' holding position marking pattern to tell you you're clear of the sensitive area. That's the core of mandatory and information signs. Let's look at the figures to see these in practice.