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Runway Markings Question

Old 26th Oct 2012, 02:46
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Runway Markings Question

Just looking at the AIP Runway Markings. Why do we have the aiming point further down the runway than the touch down markings. Is it because we aim for the solid white lines which is the aiming point, however the wheels will impact on the touch down marking which is closer to the threshold.

Thanks

brown eyes
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Old 26th Oct 2012, 03:37
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Not much point having the aiming point at the beginning of the touchdown zone and coming in too low thus touching down early and outside the touchdown zone.

That's probably the simplest explanation.
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Old 26th Oct 2012, 03:43
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I think the "touchdown zone" extends from the first TDZ marking to the last one, with the aimpoint in the middle.

Depending on the length of your machine, the deck angle on approach and the amount of flare, you could well touchdown short of your aimpoint.
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Old 26th Oct 2012, 03:51
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Aim point markings used by some widebodies e.g 747 . These vary throughout the world but for ICAO runways are not closer than 400m. The beginning of the Aim Point is aligned with the the PAPI. The smaller markings are called Fixed Distance Markings, generally every 150m (ICAO).

On most runways, the glideslope corresponds more closely with the second fixed distance markings (300m), which is where the aircraft will touchdown if it follows the glideslope to the runway. Narrow body aircraft with lower eye heights from the cockpit (e.g. A320) should aim for these markers, not the bigger third set.

If in doubt, follow the glideslope if the runway has an ILS.
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Old 26th Oct 2012, 14:48
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If in doubt, follow the glideslope if the runway has an ILS.
KK,

Only if the the ILS/GS threshold crossing height is adequate for your type. If you are going to do this, also make certain you know what you are doing when the reverse applies, there is an abnormally high GS threshold crossing height ---- who remembers the old ILS on YSSY, it was 77 ft, a Lufthansa DC-10 that did an autoland skated right off the other end.

Know your facilities and your aeroplane.
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Old 26th Oct 2012, 20:48
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Good point!

Interestingly, the A380 Aim Point is half way between two sets of markers - the second and the third.
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Old 26th Oct 2012, 22:48
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Originally Posted by Ledslead
Only if the the ILS/GS threshold crossing height is adequate for your type.
What type of aeroplane should not use an ILS glideslope (assuming standard 3/50ft TCH)??

Originally Posted by Sled again
there is an abnormally high GS threshold crossing height ---- who remembers the old ILS on YSSY, it was 77 ft, a Lufthansa DC-10 that did an autoland skated right off the other end.
An extra 157m aimpoint caused an aircraft to run off the end? When was this?
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Old 27th Oct 2012, 09:11
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What type of aeroplane should not use an ILS glideslope (assuming standard 3/50ft TCH)??
Most light singles on a visual approach...
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