Aerodromes - Visual Aids, Markings and Signs — Page 405, Lesson 552

Let’s pick up with the intermediate holding position marking, because that’s the first new item in this part of the chapter. An intermediate holding position marking is used where two or more taxiways cross. So imagine you’re taxiing along one taxiway and another taxiway crosses your path ahead. Holding points are established at suitable distances from that crossing taxiway — in other words, a defined spot where you’d stop if you needed to give way. It may be that one taxiway has priority over the other, and in that case the holding point marking may be augmented by a mandatory marking — that’s a marking that tells you, by regulation, you must stop. The marking itself should be coincident with a stop bar or clearance bar, where those are provided. A stop bar is a row of lights across the taxiway, and a clearance bar is similar but used at certain intersections — the point is the painted marking lines up with them. The taxiway intersection marking itself consists of a single broken yellow line. So the key visual here: one broken yellow line across the taxiway marks where you hold at an intersection. Now let’s move to aircraft stand markings. These should be provided for designated parking positions on a paved apron — that’s the hard-standing area where aircraft park — and also on de/anti-icing facilities, the areas where aircraft get de-iced before departure. The markings should include such elements as stand identification, lead-in line, turn bar, turning line, alignment bar, stop line, and lead-out line, as required by the parking configuration and to complement other parking aids. Let me define each of those. Stand identification is the letter and/or number that identifies the stand. It should be included a short distance after the beginning of the lead-in line — the lead-in line is the painted line that guides the aircraft from the taxiway into the stand. The height of the identification should be adequate to be readable from the cockpit of the aircraft using the stand — so it has to be big enough for the pilot to read from the seat. The lead-in, turning, and lead-out lines should normally be continuous in length. The turning line is the curved part that guides the aircraft through its turn, and the lead-out line guides it back out. Now here’s an important detail: where one or more sets of stand markings are superimposed on a stand — meaning multiple aircraft types use the same stand and their markings are overlaid — the lines should be continuous for the most demanding aircraft and broken for other aircraft. The most demanding aircraft is the one that needs the most space or the tightest geometry. The curved portions of lead-in, turning, and lead-out lines should have radii appropriate to the most demanding aircraft type for which the markings are intended — so the curve is sized for the biggest, most demanding aircraft. Where it is intended that aircraft proceed in one direction only, arrows pointing in the direction to be followed should be added as part of the lead-in and lead-out lines. Now the turn bar. A turn bar should be located at right angles to the lead-in line, abeam the left pilot position at the point of initiation of any intended turn. “Abeam” means directly beside — so the bar sits perpendicular to the lead-in line, level with where the left-seat pilot sits, at the exact point where the turn begins. The distances to be maintained between the turn bar and the lead-in line may vary according to different aircraft types, taking into account the pilot’s field of view — because different aircraft have different cockpit positions and visibility. Then the alignment bar. It should be placed so as to be coincident with the extended centre line of the aircraft in the specified marking position — meaning it lines up exactly with where the aircraft’s centre line will be when parked — and it must be visible to the pilot during the final part of the parking manoeuvre, so the pilot can steer to it. Finally, the stop line. It should be located at right angles to the alignment bar, abeam the left pilot position at the intended point of stop. So again, perpendicular to the alignment bar, level with the left pilot, at the spot where the aircraft should come to rest. So the whole stand marking system works together: the lead-in line brings you in, the turn bar tells you where to start turning, the turning line guides the curve, the alignment bar lines you up straight, the stop line tells you where to stop, and the lead-out line takes you back out. The stand identification tells you which stand you’re at, and the arrows tell you the direction of travel where it’s one-way. That figure shows an example of aircraft stand markings, so you can see how the lead-in line, turn bar, turning line, alignment bar, stop line, and lead-out line all fit together on the apron.