More than 90 turn and no course reversal/PT/HILPT

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Eibwen

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Eibwen
I’ve generally understood that an intercept will usually be charted for less than 90 intercept. So it catches me off guard when I see one charted with a particularly aggressive turn in to the final approach course. ILS Z for 26L at KLAS charts a 102 degree turn when flying the full procedure from the BLD VOR. I assume this is because of terrain or traffic flow constraints but it makes me curious if I am missing something. Something obvious … and I should hang my head in shame?

And since the lead radial of 084 off the LAS VOR shows initiating a turn before the ILS needle has probably come off the right limit aren’t you effectively turning inbound prior to achieving lateral guidance?

Am I missing something? Thanks!
 
The turn limit is 90 deg for RNAV approaches. For ILS/VOR approaches, it's up to 120 deg, depending on the length of the intermediate segment.

Why the difference? The criteria was developed at different times.
 
Ding ding!️ Thank you. I, of course, believe you but do you know a specific reference for that? Dug around in the AIM and came up blank.
 
Eibwen said:
Ding ding!️ Thank you. I, of course, believe you but do you know a specific reference for that? Dug around in the AIM and came up blank.
Click to expand...
I wouldn't expect the AIM to go into detail about that. RNAV used to be 120 degrees also a number of years ago. My guess is the reason they changed it to 90 was so they could reduce the amount of airspace to be protected. Or with 120 intercepts maybe Navigators were sensing you had passed the Fix before getting to it. If you want to go way down the rabbitt hole and learn all about Approach Construction go here.

 
Perfect reading for a Sunday.:D Thanks.
 
A couple of additional comments:

1. The depicted lead radial (LR-084) off of the LAS VORTAC helps with this sharp turn,.

2. I wonder if anyone actually flies the approach using BLD as IAF. I first suspected it'll be either radar vectors to final, or PRINO as IAF (coming from the RKSTR FOUR arrival). But then I noticed a bunch of STARs for KLAS end at BLD, so now I am curious how often aircraft are expected to make this sharp turn onto the localizer on their own in real life.

Regards,
Martin
 
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