Confused on approach plate special minimums

DesertNomad

DesertNomad

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DesertNomad
KRNO ILS-X 16R

http://155.178.201.160/d-tpp/1703/00346IXLX16R.PDF

At the bottom it lists S-ILS 16R # 5138 - 1 7/8

But at the top left it says: # For inop MALSR increase visibility to 2 1/2

So what is the purpose of the S-ILS 16R # minimums - when would you use 1 7/8 ? Would that be only if you can't make the 390ft/mn and the MALSR is working? It seems like 390ft/nm isn't very much (550fpm for me), but I guess it could be hard for a C150 or 172 on a warm day... but then there would not be any clouds. :)
 
DesertNomad said:
KRNO ILS-X 16R

http://155.178.201.160/d-tpp/1703/00346IXLX16R.PDF

At the bottom it lists S-ILS 16R # 5138 - 1 7/8

But at the top left it says: # For inop MALSR increase visibility to 2 1/2

So what is the purpose of the S-ILS 16R # minimums - when would you use 1 7/8 ? Would that be only if you can't make the 390ft/mn and the MALSR is working? It seems like 390ft/nm isn't very much (550fpm for me), but I guess it could be hard for a C150 or 172 on a warm day... but then there would not be any clouds. :)
Click to expand...

Yes, if you can't make the climb rate, you have to use the other minimum.

A Warrior would have trouble with that.

IMC doesn't have to be from fog or clouds. It can be caused by smoke or blowing dust, as well. It just means visibility. And you may need a larger climb rate with a strong tailwind (though a straight-in landing would be rather inadvisible, except in certain cases of wind shear).

I've had to get a popup approach due to an upwind wildfire before. It's a weird experience.

For an alternative presentation to the minimum climb rate issue, see the two Napa (KAPC) RNAV approaches to 36L. Ever seen an LPV minimum above pattern altitude before?
 
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So why is the LPV minimum so high there? It's even higher than the LNAV/VNAV. Isn't that a bit odd?
 
DesertNomad said:
So why is the LPV minimum so high there? It's even higher than the LNAV/VNAV. Isn't that a bit odd?
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RNAV X 16R? The LPV DA is much lower than the LNAV MDA. The visibility is greater, especially for Category A because with a DA the visibility must be based on the slant range from the DA point to the runway threshold, less any credit for approach lights. OTOH the LNAV Category A minimums are much lower because they are subject only to a table in TERPS on height above touchdown of the MDA; note that increases with approach category.
RNO RNAV X 16R.jpg
 
DesertNomad said:
So why is the LPV minimum so high there? It's even higher than the LNAV/VNAV. Isn't that a bit odd?
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AIM 5-4-5 g. explains why LPV DA's can be higher than MDA's and gives a picture of it. Which approaches at RNO did you see that?
 
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The better question is why the RNAV Y LPV minimum is 500 feet higher than the ILS CIRCLING minimum.

It's a pretty standard ILS, not very hard to fly. Well, except that ATC likes to drop you on it pretty high for VTF, as it's rather close to SFO.
 
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MAKG1 said:
The better question is why the RNAV Y LPV minimum is 500 feet higher than the ILS CIRCLING minimum.

It's a pretty standard ILS, not very hard to fly. Well, except that ATC likes to drop you on it pretty high for VTF, as it's rather close to SFO.
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Which RNAV Y?
 
aterpster said:
The LPV Y DA on my chart is slightly lower than the circling MDA. 1,249 vice 1300.
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The ILS circling MDA is 500 feet lower. It also is for the RNAV Z, which even follows the same missed approach.

I don't understand why the ILS missed approach can't be used for the two RNAV approaches for the same runway. Seems like it would solve a lot of problems and make the RNAV Y unnecessary. The ILS does a nice job of avoiding the mountains. The RNAV just blasts right over them.
 
MAKG1 said:
The ILS circling MDA is 500 feet lower. It also is for the RNAV Z, which even follows the same missed approach.

I don't understand why the ILS missed approach can't be used for the two RNAV approaches for the same runway. Seems like it would solve a lot of problems and make the RNAV Y unnecessary. The ILS does a nice job of avoiding the mountains. The RNAV just blasts right over them.
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The circling MDA cannot be lower than the straight-in DA. Thus, the much higher CTL MDA on the RNAV Y than the ILS.
 
MAKG1 said:
The ILS circling MDA is 500 feet lower. It also is for the RNAV Z, which even follows the same missed approach.

I don't understand why the ILS missed approach can't be used for the two RNAV approaches for the same runway. Seems like it would solve a lot of problems and make the RNAV Y unnecessary. The ILS does a nice job of avoiding the mountains. The RNAV just blasts right over them.
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Yeah. It wouldn't surprise me if ATC had a lot of input into the construction of these approaches. The course reversal on the ILS missed allows lower minimums. Maybe they just didn't want course reversals at all on the RNAVs. Do you know how low the Radar coverage is there, and if they run Timed Approahes?
 
luvflyin said:
Yeah. It wouldn't surprise me if ATC had a lot of input into the construction of these approaches. The course reversal on the ILS missed allows lower minimums. Maybe they just didn't want course reversals at all on the RNAVs. Do you know how low the Radar coverage is there, and if they run Timed Approahes?
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I don't know exactly, but I've been practicing CAP photo missions over Mare Island at 1500, with radar advisories from Oakland Center. So, I think the radar coverage is pretty low. Mare Island is not far south of the Napa Class D (west of Vallejo).
 
MAKG1 said:
I don't understand why the ILS missed approach can't be used for the two RNAV approaches for the same runway. Seems like it would solve a lot of problems and make the RNAV Y unnecessary. The ILS does a nice job of avoiding the mountains. The RNAV just blasts right over them.
Click to expand...

Educated guess: When these RNAV IAPs were designed LPV had to have a missed approach track straight-ahead for some distance. When they someday receive a full amendment, under current RNAV criteria they could turn just like the ILS.
 
MAKG1 said:
I don't know exactly, but I've been practicing CAP photo missions over Mare Island at 1500, with radar advisories from Oakland Center. So, I think the radar coverage is pretty low. Mare Island is not far south of the Napa Class D (west of Vallejo).
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The closest Oakland ARSR can see Napa quite well. Mt Tamalpais radomes.

ZOA ARSR near Napa.jpg
 
aterpster said:
Educated guess: When these RNAV IAPs were designed LPV had to have a missed approach track straight-ahead for some distance. When they someday receive a full amendment, under current RNAV criteria they could turn just like the ILS.
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What's the typical cycle on Approaches being reviewed and getting full amendents?
 
luvflyin said:
What's the typical cycle on Approaches being reviewed and getting full amendents?
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Attached are the last full amendments to RNAV Y and Z. June 30, 2011. And, on the FAA IFPs Gateway no amendments are planned at the present time.

There is a minor amendment scheduled for one of them this coming August.

If full amendments came before the Western Area Regional Flight Procedures Team for the AWP Region, say next month, and they were approved for routine reasons (no safety of flight issues) they would publish in late 2019 at the very soonest. Probably more like 3 years from now.
 

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