Rules of the Air — Page 126, Lesson 207

Let's pick up with the visual signalling rules — the part of the Rules of the Air that covers how aircraft and the ground talk to each other when radio isn't available or isn't being used. First, acknowledgement by aircraft. When a ground signal is given to you, the rules say you must acknowledge receipt of it. The method depends on whether you're in flight or on the ground, and on the time of day. If you're in flight during daylight, you acknowledge by rocking the aircraft's wings. During the hours of darkness, you flash your landing lights on and off twice — and if your aircraft isn't equipped with landing lights, you switch your navigation lights on and off twice instead. If you're on the ground during daylight, you acknowledge by moving the rudder or ailerons. During darkness, it's the same as in flight: flash the landing lights on and off twice, or if not so equipped, switch the navigation lights on and off twice. So the pattern is: daylight = movement of control surfaces or wings; darkness = light flashing, twice. Now, visual ground signals. These are signals displayed on an aerodrome, either in the signal square or at other locations on the apron or movement area. The signal square is usually located in front of the control tower — on the aerodrome side — and it must be visible from the air anywhere in the vicinity of the aerodrome. Its purpose is to convey essential information to pilots who cannot communicate by radio. There are also other signals for non-radio traffic on the ground, displayed from a signals mast — also in front of the control tower — or by means of indicator boards, which are information signs located on or adjacent to the control tower. Here's an important operational point: the absence of a signal square indicates that the aerodrome is not to be used by non-radio traffic. The excerpt gives Oxford as an example — there, due to high traffic density and trainee pilots in the circuit, non-radio traffic is considered hazardous, so no signal square is provided. And one final rule to note: the use of any signal by any person shall only have the meaning assigned to it under the rule. In other words, a signal means exactly what the rulebook says it means — nothing more, nothing less. Let me show you the relevant figures. shows the IFR and VFR flight levels up to and including FL, and shows them above FL. covers reduced vertical separation minima and Special VFR. These are the flight level charts that sit alongside the signalling rules in this section. So to summarise what we've covered: acknowledgement methods for in-flight and on-ground, day and night; the signal square, its location and purpose; the signals mast and indicator boards for non-radio ground traffic; the significance of a missing signal square; and the rule that signals mean only what the rules assign to them.