Aerodromes - Visual Aids, Markings and Signs — Page 400, Lesson 544

Let’s pick this up right where the runway markings leave off — the threshold markings and the aiming point marking. First, the runway threshold markings. These are the stripes painted across the start of the landing portion of the runway. The number of stripes you paint is dictated by the runway width. Look at the table: an 18-metre-wide runway gets 4 stripes; 23 metres gets 6; 30 metres gets 8; 45 metres gets 12; and 60 metres or more gets 16 stripes. So the wider the runway, the more stripes — that’s the standard. Now, 20.16 — the Transverse Stripe. This is a single stripe added to the threshold marking in two situations. First, when the threshold is displaced from the extremity of the runway — meaning the landing threshold is set back from the physical end of the concrete. Second, when the end of the runway is not at right angles to the runway centre line — so the runway end is skewed. In either case, a transverse stripe should be added to the threshold marking. And here’s the key rule: when a runway threshold is permanently displaced, arrows shall be provided on the portion of the runway before the displaced threshold — that is, on the part of the runway you fly over before you reach the actual landing threshold. Those arrows point toward the displaced threshold. The reasons why a threshold may be displaced were discussed in Chapter 19 — I’ll just flag that for now. Next, 20.17 — the Aiming Point Marking. This is the marking that indicates the position of the origin of the visual glide slope — that’s the PAPI — and also the ILS glide path transmitter, the GP transmitter. So it tells you where the glide slope actually begins. The aiming point marking is to be provided at each approach end of code 2, 3, or 4 paved instrument runways. It is recommended on code 1 paved instrument runways, and on code 3 or 4 paved non-instrument runways when additional conspicuity of the aiming point is desirable. An ICAO specification aiming point marking consists of two conspicuous stripes. Now 20.18 — Location. The aiming point marking shall commence no closer to the threshold than the distance indicated in Figure 20.5 — except that on a runway equipped with a visual approach slope indicator system, either PAPI or VASI, the beginning of the marking shall be coincident with the visual approach slope origin. So if you have PAPI or VASI, the aiming point starts exactly where the glide slope originates. Then there are the specific distances. For a code 4 runway less than 2400 metres long, the aiming point is positioned 300 metres from the threshold. For a normal 3° glide path — that’s 300 feet per nautical mile — the aircraft on glide path will cross the threshold at a height of 50 feet. Bigger aircraft require a longer landing distance available, the LDA. So for runways 2400 metres or more in length, the aiming point is 400 metres from the threshold, and the aircraft crosses the threshold at 67 feet — that gives additional gear-to-concrete clearance. So the longer runway pushes the aiming point further out, raising the crossing height to protect the landing gear. Let me tie that together. The threshold markings tell you where the landing surface begins. The transverse stripe handles the special cases — displaced or skewed thresholds. And the aiming point marking tells you where the glide slope originates, with the distance from the threshold set by runway length and the glide slope equipment installed.