Aerodromes - Visual Aids, Markings and Signs — Page 411, Lesson 561

We're moving into the signs part of the visual aids now. I want to walk you through the different types of signs you'll find on an aerodrome, and how they're laid out. This is where the ground markings and the signs start working together to guide you. Let's start with the runway vacated sign, which is Figure 20.16. This is the sign you see when you've just turned off the runway onto a taxiway. The inscription on it identifies the taxiway you've just entered — in the figure, that's taxiway F. So when you see that sign, it's telling you, "You are now on taxiway F." But there's a critical note attached to this sign. A runway vacated sign also indicates that the aircraft is leaving the perimeter of the ILS/MLS critical/sensitive area. Now, ILS is the Instrument Landing System, and MLS is the Microwave Landing System. These are precision approach aids. The critical and sensitive areas around them are protected zones where an aircraft or a vehicle could distort the signal and give false guidance to an aircraft on approach. So when you pass that runway vacated sign, you're not just confirming your taxiway — you're also confirming that you've cleared that protected zone, which is a big deal for the safety of aircraft coming in to land. Now let's look at the three main types of signs: destination, direction, and location. A destination sign — the inscription identifies the destination, and it has an arrow indicating the direction to proceed. So if you're cleared to a particular runway or apron, the destination sign tells you which way to go to get there. A direction sign — the inscription identifies the taxiway or taxiways, with an arrow or arrows appropriately orientated. So if you're on a taxiway and you see a direction sign pointing to the right with "C" on it, that's telling you taxiway C is off to your right. Figure 20.17 shows this: "Runway 02 straight ahead: holding point D3 to the right." So the direction sign is telling you where the taxiways are relative to your current position. A location sign — the inscription is the designation of the location — the taxiway, runway, or other pavement the aircraft is on or is entering. So this sign tells you where you are right now. If you're sitting on taxiway B, the location sign says "B." There's a note here about holding positions. Where it's necessary to identify each of a series of taxi-holding positions on the same taxiway, the location sign should consist of the taxiway designation and a number. So if you have multiple holding points along one taxiway, you'd see something like "A1," "A2," "A3" — the taxiway letter plus a number to distinguish each holding position. Now let's move to combination signs, which is section 20.42 and Figure 20.18. This is where a location sign and direction signs are used together. The rule is simple: signs related to left turns are placed on the left side of the location sign, and all direction signs related to right turns are placed on the right side of the location sign. There's an exception though. Where the junction consists of one intersecting taxiway, the location sign may be placed on the left-hand side. So if there's only one taxiway joining, you can put the location sign on the left. And one more detail — adjacent signs are delineated by a vertical black line. So when you have multiple signs grouped together, that black line separates them visually so you can read each one clearly. Figure 20.19 shows you what these combination signs look like in practice. So when you're taxiing and you see a cluster of signs, you read the location sign to know where you are, and the direction signs on either side tell you which taxiways are to the left and right. That's the core of it — destination signs tell you where you're going, direction signs tell you which way to turn, location signs tell you where you are, and when they're combined, the layout follows that left/right rule with the black line separating them.