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I'm interested in knowing what aiming points on runways are used for:

  • Why do some runways have aim points and some do not?
  • We say that pilots must use the maximum length of the runway. Therefore, why don't we touch down on or near the threshold lines as our aiming point?
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    $\begingroup$ Hi @adil. Have a look at this question. $\endgroup$
    – aeroalias
    Jan 17, 2016 at 14:28
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    $\begingroup$ This answer seems to adress most of it: aviation.stackexchange.com/questions/16714/… Duplicate? $\endgroup$
    – curious_cat
    Jan 17, 2016 at 18:45
  • $\begingroup$ @curious_cat I agree that question is related, but this one differs at least in that it asks why some runways do not have aiming point markings $\endgroup$
    – J W
    Jan 17, 2016 at 20:13
  • $\begingroup$ @curious_cat, I don't see that addressing the second point and that points seems the more important one here. $\endgroup$
    – Jan Hudec
    Jan 17, 2016 at 22:18
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    $\begingroup$ "We say that pilots must use the maximum length of the runway." Not sure where you've heard that, my goal in conducting landings is to use the least amount of runway possible without being hard on the brakes/tires. Usually this involves touching down as soon as possible, on the glideslope/airspeed. Maybe its just not worded the best? Often when doing short-field approaches you want to touch down as close to the threshold as possible, otherwise the touchdown point is just fine. $\endgroup$
    – Ron Beyer
    Jan 17, 2016 at 22:34

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I'll try to answer just the first portion. The aiming point marking basically serves as a visual aiming point for a landing aircraft.

Aiming point

Image from code7700.com

They are not found in all runways because the requirement is based on the aerodrome code number and they are not required in all cases. Aerodrome Reference Code from ICAO Annex 14 Volume I:

Aerodrome Code

Table from ICAO Annex 14 Vol I

From the Same reference:

5.2.5.1 An aiming point marking shall be provided at each approach end of a paved instrument runway where the code number is 2, 3 or 4.

5.2.5.2 Recommendation.— An aiming point marking should be provided at each approach end of:

a) a paved non-instrument runway where the code number is 3 or 4;

b) a paved instrument runway where the code number is 1; when additional conspicuity of the aiming point is desirable.

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    $\begingroup$ Something's up with that diagram... it shows two 500-foot distances adding up to less than a 1000-foot distance starting from the same point. $\endgroup$
    – 2012rcampion
    Apr 16, 2016 at 13:14
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  • We say that pilots must use the maximum length of the runway. Therefore, why don't we touch down on or near the threshold lines as our aiming point?

No. Using maximum length of the runway just follows from more general rule to have as much margin of error as possible. But errors can happen in both directions. Landing long is more common, so it makes sense to leave the largest margin at the end of the runway, but landing short also happens, so some margin should be left at the start too. The 1000 ft is considered reasonable margin.

Note that for small aircraft, some advocate using the middle part of the runway and leaving about as much margin at both ends. However the PAPI and ILS can't be adjusted for each aircraft, so they are installed at the standard 1,000 ft past threshold mark.

Besides, pilots don't have to use full length of the runway. There is also LAHSO.

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The markings on the runway are primarily required by the types of instrument approaches and the length of the runway. The aiming point marks at 1000 feet are required for precision approaches, they may be shifted a small distance to accommodate another crossing runway or for abnormal obstacle clearance on the glide slope.

Many precision approaches can have the plane pop out of the clouds at 200feet above ground so they don't have much time to adjust. If a bit misaligned they still need to be on a reasonable path to the actual runway and not the fence and field before the runway.

Remember that the same marks must be suited to many types of airplanes. 1000feet is not a long distance at 130knots in a jet but more than enough for a stop and go in a bush plane. Also to consider is that most airplanes require a longer takeoff distance than landing distance.

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