# Why runway 13L/31R of JFK Airport does not mention any Threshold Crossing Glide Path Height for its reciprocal end?

I am studying FAA's airports legacy file and its corresponding layout data. I noticed that runway 13L/31R of JFK Airport lacks a Threshold Crossing Glide Path Height, as one can also confirm from this site. Is there any "standard" value that one can apply here? Neither the official aforementioned legacy file nor any relevant website mention a Visual Glide Path Angle either. In comparison, runway's base end mentions both a Threshold Crossing Glide Path Height (74' AGL) and a Visual Glide Path Angle (3.00 degrees).

I would be grateful if someone could point me in the right direction.

• Do you have information on the TDZ (touchdown zone) for the runway and glide path angle? You should be able to calculate the threshold crossing height with those two data points. – Ron Beyer Jun 17 '18 at 21:45
• It provides the Elevation at Touchdown Zone, but no Visual Glide Path or any other relevant values. – Vector Zita Jun 17 '18 at 23:09
• I’m curious as to what you’re calling the “base end” – TomMcW Jun 18 '18 at 21:08
• According to the layout of the airports' legacy file, the base end is the "13L" point of the runway, in other words the first point of the runway's segment when it is set to "13L" configuration. From legacy file: "BASE END IDENTIFIER: THE RUNWAY END DESCRIBED BY THE FOLLOWING INFORMATION. RELATES TO THE FIRST PART OF THE RUNWAY IDENTIFICATION (EX. FOR RUNWAY 18/36 THE BASE END IS 18)". – Vector Zita Jun 19 '18 at 12:59
• @VectorZita You can't calculate it with those two points, you need the TDZ (how many feet from the threshold) and the glide path angle. Using some simple trig, you can then calculate the height above the threshold where the glide path crosses. You can't do it with the "TDZ height" because that is the elevation of the TDZ, it has no relation to the distance from the threshold. – Ron Beyer Jun 19 '18 at 18:47