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Why are offset lead-in arcs used?

enter image description here

Image source: Google Earth, showing offset lead-in arcs.

There is little literature on the subject matter. I did research it a while back but I lost the PDF's, and videos. Research was inconclusive.

But I did learn that they guide only one aircraft type—selected radius can only accommodate a single wheelbase, radii vary. Initially I thought long airliners (A346, B773, and so on). But watching videos from observation decks in airports, even a 777-300 doesn't follow it. Whether taxiing in or pushing out, it wasn't even close to the line.

So if only one wheelbase can benefit, and it is not long airliners, why use it?

enter image description here

Image source: Google Earth, showing non-offset lead-in arcs.

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Image source: Google Earth, showing straight lead-in lines.

All images from KJFK.

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    $\begingroup$ If you're talking about the curved portion of the lead-in lines, remember that if the pilot turns so as to keep himself on the curved portion of the lines, the main gear of a long aircraft will not be over the curve, but rather more or less straight-in to the straight portion. $\endgroup$ – Terry Aug 22 '16 at 21:12
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    $\begingroup$ They may be used more for ground-crew during push-back to guide the nose wheel tires and get the aircraft into the proper position. $\endgroup$ – Ron Beyer Aug 22 '16 at 21:19
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    $\begingroup$ If Google wasn't so awesome at removing numbers you would be able to see the aircraft type painted in the yellow box where it branches off the straight line, and yes it is meant for a single aircraft type. The terminal was probably designed specifically for a certain aircraft and expanded later for other types. $\endgroup$ – Ron Beyer Aug 23 '16 at 1:56
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    $\begingroup$ The NLG path for B777-300 is to the left of this number. You may want to compare with this Boeing document, page 69 (extract). This is only for one aircraft type, I believe you can mentally determine other paths relative to this one with experience. There is also a second NLG path, not identified. Here a 3D view. The wear marks show the guidance is used. $\endgroup$ – mins Aug 23 '16 at 8:22
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enter image description here

Not clear in the image in the question is the aircraft type the offset arc was laid down for. Example above is for the B777-300.

Some gates may have been designed for a certain type.

Based on that, a pilot of a shorter/longer [wheelbase] type can use the offset arc as a guide in turning in before/after it.


Thanks to Ron Beyer and mins for the comments that led to this answer.

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