NOTAM explanation

[wpbarnar]

What does LPV and LNAV/VNAV LINES OF MINIMA NA mean? 

This was contained in a NOTAM for the RNAV 32 and 24 at KAAF.

I don’t know what “lines of minima” are.

Bill

[midlifeflyer]

16 minutes ago, wpbarnar said:

What does LPV and LNAV/VNAV LINES OF MINIMA NA mean? 

This was contained in a NOTAM for the RNAV 32 and 24 at KAAF.

I don’t know what “lines of minima” are.

Bill

You are not authorized to use the LPV and LNAV/VNAV minimums for the approach and must use the LNAV minimums.

"Lines of minima" refers to the bottom "line" of the chart which shows, well, "minima" (approach minimums).

Edited May 29, 2021 by midlifeflyer

[wpbarnar]

The approach list a DA for the LPV and LNAV/VNAV of 359’ and 378’ respectively.  It also includes a MDA for the LNAV/VNAV of 500’

So can I go down to the MDA?

[EricJ]

John King has opined in the past regarding how cryptic everything from METARs to NOTAMs are and that it is counter productive to disseminating information safely.   I'm in full agreement and stuff like this just reinforces the case, I think.

I wouldn't have known what "lines of minima" are, either.

[midlifeflyer]

5 hours ago, wpbarnar said:

The approach list a DA for the LPV and LNAV/VNAV of 359’ and 378’ respectively.  It also includes a MDA for the LNAV/VNAV of 500’

So can I go down to the MDA?

it shows an "LNAV MDA", not an LNAV/VNAV MDA. That's what you use. The LNAV MDA.  Because the LPV and LNAV/VNAV minima are NA.

Edited May 29, 2021 by midlifeflyer

[midlifeflyer]

7 hours ago, EricJ said:

I wouldn't have known what "lines of minima" are, either.

There are plenty of problems with the NOTAM system. Even the NTSB says so. I don't agree that the phrase "lines of minima" is one of them. What else other than the lines of the approach chart describing approach minima could it possibly mean?

Webster's Dictionary.

minimum

 noun

min·i·mum |  \ ˈmi-nə-məm   \

plural minima\ ˈmi-nə-mə   \ or minimums

[EricJ]

5 minutes ago, midlifeflyer said:

There are plenty of problems with the NOTAM system. Even the NTSB says so. I don't agree that the phrase "lines of minima" is one of them. What else other than the lines of the approach chart describing approach minima could it possibly mean?

Webster's Dictionary.

minimum

 noun

min·i·mum |  \ ˈmi-nə-məm   \

plural minima\ ˈmi-nə-mə   \ or minimums

The first thing I think of with a term like "lines of minima" are contours on a terrain plot or something like that.   Maybe I spent too many years as an engineer, but lines connect points and minima are points on a data set, so lines connecting the lowest points on the graph of a data set would be my first thought.   Then I'd be trying to figure out how that applied to the approach maps.

It's a sensible term in hindsight if you already know what it is referring to, but it's not good if it is seldom used or likely to be important to people who have never seen it before.

For safety-critical items, which NOTAMs typically are, spelling things out a bit more seems very sensible.   Many decades ago the bandwidth for transmitting the data and the paper and space for printing them were limited enough that abbreviations and terseness were needed in order to make the information available.   Those constraints are no longer relevant, so as far as I can tell tradition is the only thing preventing clear presentation of the information, which does not seem like an adequate reason to me.

 

[DMM]

I agree with Eric J.    The lines of minima are not authorized?????  Why not just say the LPV and LNAV/VNAV approaches are not authorized.  That's the end result - right?  Obviously written by the people who design approaches.

Edited May 29, 2021 by DMM

[midlifeflyer]

1 hour ago, DMM said:

I agree with Eric J.    The lines of minima are not authorized?????  Why not just say the LPV and LNAV/VNAV approaches are not authorized.  That's the end result - right?  Obviously written by the people who design approaches.

That"s not really the end result. Perhaps it could be worded differently,  but your solution doesn't work. We are in a world with its own jargon, so the semantic technicalities count. We might think of them as different, but there  is no such thing as "LPV and LNAV/VNAV approaches." These are "RNAV (GPS)" approaches. Just like a traditional VOR approach with a non-required DME stepdown, (a VOR approach, not a VOR/DME approach) there are  different minimums based on your equipment.

Even if you want to think of them as different, there is nothing in the NOTAM to say you can't use the LPV or LNAV/VNAV glidepath.  Like the DME stepdown,  the only thing affected is how low you can go. So any solution, no matter how worded, would still only say you are not authorized to go as far down as the LPV andLNAV/VNAV minimums.

How about just getting rid of the word "lines" if that bothers you? "LPV and LNAV/VNAV minima NA." That's exactly what it means. No more and no less.

I have literally been scratching my head wondering why this is so confusing.

[EricJ]

Just now, midlifeflyer said:

How about just getting rid of the word "lines" if that bothers you? "LPV and LNAV/VNAV minima NA." That's exactly what it means. No more and no less.

Because that doesn't say what to replace them with.

Just now, midlifeflyer said:

I have literally been scratching my head wondering why this is so confusing.

Perhaps a better statement would have been:  "LNAV MDA must be used for LPV and LNAV/VNAV minimums.   LPV and LNAV/VNAV minimums Not Available"  (I think "NA" should could even be spelled out for clarity.)    It should be more about conveying the information clearly than making it as short as possible, imho.   If people are forced to guess, they may guess wrong, or just decide a useful option is not available to them because they weren't certain they understood the NOTAM properly.

 

[wpbarnar]

27 minutes ago, midlifeflyer said:

I have literally been scratching my head wondering why this is so confusing

It may be obvious to you but it is clear as mud to me.

[DMM]

1 hour ago, midlifeflyer said:

That"s not really the end result. Perhaps it could be worded differently,  but your solution doesn't work. We are in a world with its own jargon, so the semantic technicalities count. We might think of them as different, but there  is no such thing as "LPV and LNAV/VNAV approaches." These are "RNAV (GPS)" approaches. Just like a traditional VOR approach with a non-required DME stepdown, (a VOR approach, not a VOR/DME approach) there are  different minimums based on your equipment.

Got it.  I learned something today.  I was assuming the LPV and LNAV/VNAV vertical guidance couldn't be used for some reason.  

[midlifeflyer]

5 hours ago, DMM said:

Got it.  I learned something today.  I was assuming the LPV and LNAV/VNAV vertical guidance couldn't be used for some reason.  

Dunno. I can read and understand what a NOTAM says but I'm not fluent.  I don't know why the restriction and I guess it's possible there is some kind problem making both types of vertical guidance unusable, but I would expect the NOTAM to include something to say that. I know there is some standard phrasing to say when for example,  certain types of navigation components are not or may not be "AVBL" or are "unusable."
So, I  would be prepared for the possibility my GPS would only annunciate  "LNAV" (always prepared for that anyway) but if it annunciated LPV, I would fly the glidepath down to LNAV (or circling) minimums because the only thing the NOTAM says is that the others are not authorized.

[carusoam]

Expect that a wording issue is causing the challenge here...

 

What LINES are they talking about?  Lines on the approach plate?

Are words lines?  (I wrote a few lines here)

 

Expect nothing to be used... because it makes sense...

The aviation world is too complex for that...

Everything on an approach plate has been designed and used for best delivery of information in a critical phase of flight...

 

The words used are probably approved language that get used exactly this way when this challenge occurs...

 

It helps to be...

• a CFII, who knows approaches well
• a lawyer, who knows laws well
• an English speaking pilot, who knows all the definitions of all the words well
• Somebody who puts this stuff together all the time, in IMC...

 

Or...

Read lots of charts to learn their language...

WAAS based approaches have a new language of their own... compared to the older VOR/ILS systems...

The FAA has a handbook that probably covers the latest language of approach charts...

 

Expect one thing... change is constant...   sort of... 

Best regards,

-a-

 

[PT20J]

Too many words: I'd have just written, "LPV and LNAV/VNAV approaches NA."

A quick search of the AIM shows no entries for "Lines of Minima" but several entries for Minima Lines."

So, I guess the pedantically correct phasing should have been, "LPV and LNAV/VNAV minima lines NA." Which does seem clearer to me.

Skip

[cliffy]

Just remember- in every graduating class of Doctors SOMEONE graduated at the very bottom of the class!

Things need to be written for the lowest common denominator not BY the lowest common denominator  :-) :-)