Rules of the Air — Page 111, Lesson 173

Let’s pick this up right where the rules start to get practical: the lights an aircraft must show, and when. I’m going to walk you through Rule 6.23 first. This is the master rule for lights displayed by aircraft. The lights I’m about to name must be illuminated from sunset to sunrise — and I want you to hold that phrase, because it’s a defined term in the regulations, so we’ll treat it as a technical trigger — or during any other period specified by the appropriate authority. So the authority can extend the lighting requirement beyond darkness if it decides to. Two categories of lights are required. First, anti-collision lights. Their purpose is exactly what the name says: they’re intended to attract attention to the aircraft. Second, navigation lights. These are intended to indicate the relative path of the aircraft to an observer. That means they let someone looking at the aircraft — another pilot, a ground controller, anyone — see which way the aircraft is heading relative to them. And here’s a hard restriction: no other lights shall be displayed if they are likely to be mistaken for these lights. So you can’t put up any extra light that could be confused with the navigation lights. Now Rule 6.24. This one is about the movement area of an aerodrome, and it applies during the same period — sunset to sunrise, or any other period required by the appropriate authority. Two requirements here. First, all aircraft moving on the movement area shall display navigation lights — again, intended to indicate the relative path of the aircraft to an observer. And again, no other lights shall be displayed if they are likely to be mistaken for these lights. Second, all aircraft on the movement area — not just moving ones — are to display lights that indicate the extremities of their structure. That means lights marking the wingtips, the tail, the nose — the outer edges of the airframe — unless the aircraft is stationary and otherwise adequately illuminated. Now, there’s a useful clarification here about parked aircraft. An aircraft parked on the Apron — and Apron is another defined term — will be adequately illuminated, because an Apron is required to be lit if it is to be used at night. So if it’s parked on a lit apron, you don’t need the extremity lights. But it is usual to use what are called ‘glim’ lamps to mark the extremities of aeroplanes parked off the Apron. So glim lamps are the standard way to show the outer edges when the aircraft is parked somewhere that isn’t lit. Rule 6.25 is about engines running. All aircraft on the movement area of an aerodrome are to display lights intended to attract attention to the aircraft. And specifically, aeroplanes with engines running are to display lights to indicate that fact. Red anti-collision lights will suffice for this purpose. So the red anti-collision light is the accepted way to show that an engine is running. There’s a note here that’s worth remembering: it is usual to indicate that an aeroplane is manned by operating the anti-collision light. This serves to warn all personnel that the engines may be started. So when you see the red anti-collision light flashing on a parked aeroplane, that’s the signal that someone is on board and the engines could be started at any moment — a real safety warning for ground personnel. And Rule 6.26 starts the next topic: anti-collision lights. It begins with all aircraft in flight which are fitted with — and that’s where the excerpt cuts off. So we’ll take that up next: what’s required of anti-collision lights on aircraft that are actually in flight. Before we go on, let me make sure the key points are locked in. Sunset to sunrise is the default lighting window, extendable by the appropriate authority. Anti-collision lights attract attention; navigation lights indicate relative path. No other lights may be shown if they could be mistaken for navigation lights. On the movement area, moving aircraft show navigation lights; all aircraft show extremity lights unless stationary and adequately illuminated — with glim lamps used off the apron. And red anti-collision lights indicate engines running, warning that engines may be started.