Aerodrome Lighting — Page 417, Lesson 570

Let’s start with the big picture, because this chapter is really about one idea: every light on an aerodrome exists for a reason, and most of those reasons come down to aircraft safety. The chapter opens by admitting something honest — with so many lights on an aerodrome, it can be confusing and even disorientating. But the point is that each light or lighting system has a purpose. So we’re going to go through the various systems and explain what they do. Now, two important scope notes before we dive in. The learning objectives require you to know the lighting systems themselves, but the spacing of lights or groups of lights — excluding approach lighting systems — is outside the scope of this course. And the design of lighting systems is also beyond this course. So we’re not going to be measuring distances between lights, and we’re not going to be designing them. We need to know what they are and what they’re for. Here’s a frustrating reality you should know as a professional: there is no standard system of lighting in use worldwide. ICAO has laid down standards and recommended practices in Annex 14, but the actual systems you’ll encounter will vary. So you learn the principles, not a single universal layout. Let’s move to safety. There’s a rule about non-aeronautical lights — that is, lights near an aerodrome that are not part of the aviation lighting system. If such a light might endanger the safety of an aircraft, it must be extinguished, screened, or otherwise modified so as to eliminate the source of danger. So a bright advertising sign or a floodlight near the approach path that could dazzle a pilot — that has to be dealt with. Next, elevated lights. These are the lights that stand above the ground — runway lights, stopway lights, and taxiway lights. The rule is that they shall be frangible. Frangible means they’re designed to break away easily on impact, so that if an aircraft hits one, it does minimal damage to the aircraft. Their height must be sufficiently low to preserve clearance for propellers and for the engine pods of jet aircraft. So they can’t be so tall that a propeller or a jet engine pod would strike them. And where they’re not sufficiently conspicuous — where they don’t stand out enough — they are to be suitably marked. Now, light intensity. This is a key operational point. In poor visibility conditions by day, lights can actually be more effective than markings. Think about that — during the day, in fog or heavy rain, painted markings on the runway may be hard to see, but a bright light can still cut through. For lights to be effective in those conditions, or in poor visibility by night, they must be of adequate intensity. Here’s the engineering trade-off: to obtain that required intensity, it will usually be necessary to make the light directional. A directional light concentrates its beam in a particular direction rather than spreading it everywhere. But that creates a new requirement — the arcs over which the light shows will have to be adequate, and they must be orientated to meet the operational requirements. In other words, if you focus the light, you have to make sure it’s aimed where the pilot actually needs to see it. And finally, a crucial point about the system as a whole: the runway lighting system has to be considered as a whole, to ensure that the relative intensities of the lights are balanced. The excerpt cuts off right there, but the idea is that you can’t have one light blindingly bright and another barely visible — the whole system has to work together. Let me show you what some of these look like. Here’s a figure of boundary markers, which are part of the aerodrome marking and lighting picture. And here’s another figure showing fixed distance and parking stand markers, along with visual docking guidance systems — these are the systems that guide an aircraft into its parking position on the stand. So to tie it together: we have the principle that every light has a purpose tied to safety. Non-aeronautical lights that endanger aircraft must be eliminated. Elevated lights must be frangible and low enough to clear propellers and engine pods. And lights must be intense enough to work in poor visibility — which usually means making them directional, with the beam arcs properly orientated, and the whole runway system balanced as one unit. That’s the foundation we’ll build on as we go through the specific lighting systems.