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# Runway Point of Intercept

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# Runway Point of Intercept

4th Jun 2019, 14:28

Join Date: Jun 2011
Location: On Contract at 14° 35' N, 121º 00 E'
Posts: 35
Runway Point of Intercept

Can someone show the RPI graphics for following a 3 degree glide slope and where the a/c would touchdown ?

Thank you
TMIS
4th Jun 2019, 17:04

Join Date: Feb 2019
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Posts: 431
Depends, ILS or PAPI?
4th Jun 2019, 17:09

Join Date: Jun 2011
Location: On Contract at 14° 35' N, 121º 00 E'
Posts: 35
Both scenarios would be good to see. Thanks.
5th Jun 2019, 04:35
Moderator

Join Date: Apr 2001
Location: various places .....
Posts: 6,517
3 degrees is near enough to 5 % or 1:20, for small distances so, from wherever you want to start the calculations, the horizontal distance to run to intercept is 20 times the height loss required.
5th Jun 2019, 05:40

Join Date: Feb 2000
Location: 500 miles from Chaikhosi, Yogistan
Posts: 3,522
Depending on your assumptions and project, you may also have to account for the issue of the MEHT. You might be seeing 2 reds/2 whites from the FD but the gear on a 737 will have a very different threshold crossing height to a 747.
5th Jun 2019, 10:53

Join Date: Jun 2011
Location: On Contract at 14° 35' N, 121º 00 E'
Posts: 35
Thanks all.
5th Jun 2019, 14:53

Join Date: Feb 2019
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Posts: 431
From a design perspective:

ILS: GPA through the TCH to the ASBL. The RDH needs to be calculated to that the wheel glidepath does not go lower than 6m screen height at the threshold. The standard from ILS GP to wheel GP is 5.8m (denoted as 'H' or in this example 'W'). If the aircraft using the runway have a greater H than 5.8m, the GPA must be adjusted. Quite a few aircraft, especially the longer versions have upwards of 8m H. Depending on SOP, there may be an add for flair.

example of H and H1 values

PAPI: GPA through the TCH to the ASBL. The difference here is that the PAPI is set with the aiming point, given eye height MEHT The AIM point is set using the GPA, TCH and eye height H1. The same minimum screen height WTH applies at the threshold of 6m

5th Jun 2019, 17:27

Join Date: Jun 2011
Location: On Contract at 14° 35' N, 121º 00 E'
Posts: 35
Thank you so much. This is great for my project.
6th Jun 2019, 07:11

Join Date: Feb 2000
Location: 500 miles from Chaikhosi, Yogistan
Posts: 3,522
Originally Posted by Smythe
From a design perspective:

... Depending on SOP, there may be an add for flair.
What - 50m for a handlebar moustache?
6th Jun 2019, 12:02

Join Date: Mar 2002
Location: Seat 0A
Posts: 7,769
Good one Smythe: GPA, TCH, ASBL, RDH, H/W, MEHT, H1, WTH, EWH.

What's ASBL?
6th Jun 2019, 12:49

Join Date: Feb 2019
Location: shiny side up
Posts: 431
Approach Surface Baseline, ASBL is the baseline using the elevation at the threshold. It assumes the world is flat at that elevation. (at least for design purposes)

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