ILS Question
07-20-2010, 04:45 PM
#1
New Hire
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Joined APC: Jul 2010
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ILS Question
Under what conditions will an ILS be published without LOC minimums? This question came up based on the KPOC ILS 26L is published without LOC mins on the ILS plate; however, a separate LOC 26L plate is published...why not publish a single plate with the LOC mins on the ILS plate? Any ideas?
07-22-2010, 04:44 AM
#5
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Sort of guessing here but I think there are multiple reasons. The different MAP might be just one reason. An ILS and a LOC have different TERPS design criteria. In some (mos?) cases, the result is similar enough that they can share a chart. But in others there are differences in the procedures that make combination on one chart inadvisable.
07-22-2010, 07:39 AM
#6
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I remember asking the same thing when I was going for my II. I do not remember exactly, but I think we are all on the same track. It has something to do with TERP design specification and obstacle clearance. The exact reason why is probably specific to that airport but again, it probably has something to do with required obstacle clearance for a non precision LOC approach vs the precision ILS approach. Either on the approach end or missed approach end.
I know sometimes they will even have multiple ILSs to the same runway because a regular ILS which takes you down to 200' ABTZE would require a pretty steep climb out while the other ILS they publish may only take you down to 600' ATDZE but have a regular climb out.
I know sometimes they will even have multiple ILSs to the same runway because a regular ILS which takes you down to 200' ABTZE would require a pretty steep climb out while the other ILS they publish may only take you down to 600' ATDZE but have a regular climb out.
07-22-2010, 07:50 AM
#7
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Joined APC: Feb 2010
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Posts: 76
Yep - I think you are all right. AF sent me to TERPS school a long time ago - It might be the clearances on the approach end - but normally since the ILS brings you "lower" on the approach - you might have to have a more restrictive climbout on the MAP because you are penetrating the obstruction plane - LOC you are higher when you go missed and might not have the issue - which pushed you to a different approach panel because they can't share the MAP. By the way - passing grade out of TERPS school is 65% - Every time I look at an approach plate I'm thinking ' 35% of this could be crap. Be careful out there folks.
07-22-2010, 08:11 AM
#8
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If you look at the charts, both have the same feeder route, both cross LIZZE at 4000 and HAWNN at 3200, both have the same miss, climb to 2100 then a climbing left turn to 4000, join to POM 164 to PRADO. So ?
07-22-2010, 10:00 AM
#9
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Joined APC: Nov 2008
Posts: 826
Originally Posted by Twin Wasp
If you look at the charts, both have the same feeder route, both cross LIZZE at 4000 and HAWNN at 3200, both have the same miss, climb to 2100 then a climbing left turn to 4000, join to POM 164 to PRADO. So ?
Assuming that there aren't any substantial differences (other than the absence of the glideslope), my WAG: At one time they weren't as similar.
The ILS is the original 2008 procedure; the LOC a fairly new 2010 amendment (3rd amendment even). Maybe they were different enough in the past to justify separate charts and, having done that, they left it that way. Or something in one of the amendments to the LOC procedure led the FAA to separate them.
If someone is really curious about the answer, email the chart division - they are very responsive to questions about the charts.
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