Right, let's pick this up with taxiways — Page 385, Lesson 523

Right, let's pick this up with taxiways. We've just dealt with runways and the stopping distances, and now we're looking at the taxiway system itself. First, the fundamental purpose. In basic terms, according to Annex 14, taxiways should be provided to permit the safe and expeditious surface movement of aircraft. So the whole design intent is to get aircraft moving on the ground safely and without delay. Now, the layout. Taxiways may include turns, and these are especially common close to runways. They may cross, join, and intersect, which is why they require signs and markings to enable pilots to reach their destination on the aerodrome. That's a critical point — the taxiway network is a route system, and the signage is what lets a pilot navigate it. A key safety consideration: taxiways, especially those parallel to runways, must not be confused with runways. And here's a striking real-world example — at some aerodromes, Gatwick for example, the parallel taxiway is also the secondary runway. So the same strip of pavement serves both functions, which really sharpens the need for correct identification. Now, there are specific points on taxiways where aeroplanes are held prior to entering the runway for take-off. These holding points need careful thought. Also, portions of taxiways close to the runway are a concern because the presence of a large aeroplane — described in the text as a large lump of electromagnetically friendly metal — may interfere with ILS or MLS transmissions. ILS is the Instrument Landing System, MLS is the Microwave Landing System. Or, more fundamentally, the aircraft itself is an obstacle to operations. So a big aircraft sitting on a taxiway near the runway can either block the guidance signals or physically obstruct the operation. Let's move to the general layout, section 19.47. Sufficient entrance and exit taxiways for a runway are to be provided to expedite movement of aeroplanes to and from the runway. This includes the provision of rapid exit taxiways — also called fast turn-off lanes — where traffic volumes are high. These are angled exits that let an aircraft leave the runway at speed without stopping, keeping the runway clear for the next arrival. Where the end of a runway is not served by a taxiway, it may be necessary to provide additional pavement at the end of the runway for turning aeroplanes. That's a turning area or turning bay. Such areas may be usefully situated along the runway to reduce taxi times — so you don't have to taxi all the way to the far end just to turn around. Finally, section 19.48, taxiing of aeroplanes. Taxiways are required to have a painted centre line, which may be lit if the aerodrome is to be used at night. When taxiing an aeroplane, it is vitally important that the nose wheel of the aeroplane is kept on the centre line, especially during turns. Pilots usually gain this skill by experience, but special procedures may be used in extreme cases. The example given is Concorde, where the nose wheel was so far aft of the nose of the aeroplane that pilots used marks on the windscreens to 'fix' the taxiway edge, thus keeping the nose wheel in position on the centre line. So the nose of the aircraft was so far ahead of the nose wheel that you couldn't see the wheel's position directly — they had to use windscreen reference marks aligned with the taxiway edge to keep the wheel tracking the centre line. That's the taxiway system for you — the layout, the holding points, the interference concerns, and the technique of keeping that nose wheel on the centre line.