Let’s pick this up right where the signal-light story left off — Page 434, Lesson 586

Let’s pick this up right where the signal-light story left off. We’ve just covered the red stop and green go signals, plus the flashing red light. Now I want to walk you through a completely different piece of airfield lighting: the Runway Guard Lights, which are covered in paragraph 21.38. First, the purpose. Runway Guard Lights are used to warn pilots and drivers of vehicles that they are about to enter an active runway. So they are a safety barrier, a visual warning that says, “Stop — you are at the threshold of a runway that is in use.” They are not for guiding you along a taxiway; they are for guarding the point where a taxiway meets a runway. Now, where are they installed? They are placed at the entrance to runways that are used in RVR conditions less than 550 metres, where a stop bar is not fitted. RVR, remember, is Runway Visual Range — the distance a pilot can see along the runway. So in very poor visibility, below 550 metres, and where there is no stop bar to hold you, these guard lights take over that warning job. They are also installed in RVR conditions of 550 to 1200 metres where traffic density is high. So the second case is slightly better visibility, but busy traffic — again, the guard lights warn you before you roll onto the active runway. There are two configurations of runway guard lights, and they are known simply as Configuration A and Configuration B. Let me describe each one precisely. Configuration A consists of unidirectional flashing yellow lights spaced at intervals of 3 metres. So you have a row of yellow lights, each one flashing, all facing in one direction — unidirectional — and they are spaced 3 metres apart. That spacing is a specific value you should hold onto: 3 metres. Configuration B is a pair of unidirectional, flashing yellow lights. So instead of a row, you get just two lights, side by side, again unidirectional and flashing yellow. In both configurations, the lights are flashing yellow and they show in the direction of taxiing aircraft. That is the key operating detail — they are unidirectional, meaning they only show their warning to traffic coming from one direction, and that direction is the direction of taxiing aircraft. So the light is aimed at the pilot or driver who is approaching the runway. Let me also tie this back to the figure I have for you. Figure 21.11 shows the two configurations side by side — Configuration A with its row of unidirectional flashing yellow lights spaced at 3-metre intervals, and Configuration B with its pair of unidirectional flashing yellow lights. Take a look at that figure to fix the visual difference in your mind. One thing I want to make sure you keep straight: these are flashing yellow lights. That is different from the red stop and green go signals we just covered, and different from the flashing red light. Yellow here is a warning colour — it is telling you to be alert, to check, because you are about to enter an active runway. The flashing action draws your attention, and the unidirectional aim means it is specifically for you, the approaching pilot or vehicle driver. So to summarise the whole picture: Runway Guard Lights warn pilots and vehicle drivers that they are about to enter an active runway. They sit at the entrance to runways used in RVR below 550 metres where no stop bar is fitted, and in RVR of 550 to 1200 metres where traffic density is high. There are two configurations — A, a row of unidirectional flashing yellow lights spaced 3 metres apart, and B, a pair of unidirectional flashing yellow lights. Both flash yellow and point in the direction of taxiing aircraft. That is the complete story of the runway guard lights.