RNAV TAA sector altitudes. Minimum or mandatory altitudes

[AIREMATT]

I’m trying to find the one correct reference to the sector altitudes on an RNAV approach approach with Terminal Arrival Altitudes published for each sector. 
Here are the references from the Instrument Procedures Handbook that I have found:

One says we may descend to the altitudes for each sector we are entering and the other says we should descend to the altitude shown in the sector.

Does anyone have a tiebreaker reference anywhere as to whether the sector altitudes are minimum or mandatory altitudes. I’ve seen many opinions on which it is, but no sources to confirm it.

Thanks,

Dan

 

[PT20J]

[AIREMATT]

40 minutes ago, PT20J said:

Unfortunately, that reference and AIM Fig. 5-4-10 explanation say the same contradicting thing word for word as my 2 examples from the IPH.

MAY descend to the minimum, and SHOULD descend to the published altitude.

[carusoam]

This is where we invite the the legal team… for proper word usage….

You know when the FAA uses words like May and Should… this is done on purpose, with specific meanings…

Inviting @midlifeflyer for the FAA rules and words discussion…

Go MS!

Best regards,

-a-

[PT20J]

Within a TAA, and cleared for the approach, you may descend to the 91.177 minimum IFR altitude which is the published minimum altitude for that sector. The should part comes in only in that you need to plan your descent so as not to end up too high at the FAF using a normal descent rate.

Maybe this will help…

[Pinecone]

The should instance is when you are on a published feeder route.   

[midlifeflyer]

6 hours ago, carusoam said:

This is where we invite the the legal team… for proper word usage….

You know when the FAA uses words like May and Should… this is done on purpose, with specific meanings…

Inviting @midlifeflyer for the FAA rules and words discussion…

Go MS!

Best regards,

-a-

@PT20J provided the AIM reference. For those with an IFR Mag subscription (sorry, paywall on this one), my Gettin' Down article discusses it. 

Edited November 30, 2022 by midlifeflyer

[midlifeflyer]

4 hours ago, Pinecone said:

The should instance is when you are on a published feeder route.   

Curious. Which "should" instance.

[PeteMc]

2 hours ago, midlifeflyer said:

Curious. Which "should" instance.

Original post, the lower red box on the left side (pp 4-63).  But start at the beginning of the paragraph above the red box with the "should" in it to get the full context.

 

EDIT: I said "right side" in my original post, meant LEFT side/column.

 

 

Edited November 30, 2022 by PeteMc

[EricJ]

12 hours ago, carusoam said:

This is where we invite the the legal team… for proper word usage….

You know when the FAA uses words like May and Should… this is done on purpose, with specific meanings…

Inviting @midlifeflyer for the FAA rules and words discussion…

Go MS!

Best regards,

-a-

I found two ATC docs that both indicate "should" means a procedure is recommended.   In most docs these days the way to show a requirement is with "must", as "shall" is now often considered ambiguous.

https://www.faa.gov/air_traffic/publications/atpubs/atc_html/chap1_section_2.html

https://www.faa.gov/air_traffic/publications/atpubs/fs_html/chap1_section_2.html

What the FAA tells their writers about may vs should:

https://www.faa.gov/about/initiatives/plain_language/articles/authority/

[jaylw314]

25 minutes ago, EricJ said:

I found two ATC docs that both indicate "should" means a procedure is recommended.   In most docs these days the way to show a requirement is with "must", as "shall" is now often considered ambiguous.

https://www.faa.gov/air_traffic/publications/atpubs/atc_html/chap1_section_2.html

https://www.faa.gov/air_traffic/publications/atpubs/fs_html/chap1_section_2.html

What the FAA tells their writers about may vs should:

https://www.faa.gov/about/initiatives/plain_language/articles/authority/

While there may be a lot of controversy about interpreting the Ten Commandments, I don't think any controversy centers around the word "shall."  

To me, "may" and "should" are not contradictory nor mutually exclusive.

[midlifeflyer]

2 hours ago, PeteMc said:

Original post, the lower red box on the right side (pp 4-63).  But start at the beginning of the paragraph above the red box with the "should" in it to get the full context.

 

 

I think both red box "shoulds" are are the same. Just the normal "here's your minimum altitude when cleared for the approach. You can descend to it and we recommend you  get down to an altitude where you will be  on target for  the approach when you get to the IAF or IF."

Edited November 30, 2022 by midlifeflyer

[EricJ]

41 minutes ago, jaylw314 said:

While there may be a lot of controversy about interpreting the Ten Commandments, I don't think any controversy centers around the word "shall."  

Oh, it's surprising...

https://www.plainlanguage.gov/guidelines/conversational/shall-and-must

[PeteMc]

52 minutes ago, EricJ said:

Oh, it's surprising...

Yes, but I didn't see any clear date on that page.  I did see the older sources listed, but still not clear when the article was written.

So my take away was "...The legal community is moving to..."  Which is all fine and good, but a LOT of the FARs, Legal Interpretations and other aviation documents were all written back when all the lawyers did think it meant “...has a duty to...” and used it as such.  So I'd don't think you'd get far arguing that Shall meant the new definition for a doc written decades ago.  Oh, but I can see lots of billable hours fighting new and old definitions.  Have to tell my (lawyer) nephew to watch out for those cases!

 

[kortopates]

It’s really as simple as the symbology used. It charted as a minimum altitude. If it was intended as a mandatory altitude, which it’s clearly not, it would have been charted as such with a line above and below the altitude.
See the Chart symbology users guide for the meaning.


Sent from my iPhone using Tapatalk

[AIREMATT]

7 hours ago, kortopates said:

It’s really as simple as the symbology used. It charted as a minimum altitude. If it was intended as a mandatory altitude, which it’s clearly not, it would have been charted as such with a line above and below the altitude.
See the Chart symbology users guide for the meaning.


Sent from my iPhone using Tapatalk

Thanks Paul,

That’s the reference I was missing. Included below:

[Ibra]

I recall TAA in US is designed as operationally usable altitude and once you are cleared to IAF via feeder Area or Airway you can descend to TAA altitude: no one else will be under you going to that IAF and you won't hit terrain or get lost on radio/radar 

One can easily check in US plates that TAA altitude for GPS is never lower than Airway MEA or Radar MVA and way higher than conventional MSA (on exiting ILS or VOR fixes)

This is not the case in many other countries (don't ask me how I know ) where TAA altitude are sometimes treated as MSA sector and GPS procedure are designed in standalone fashion and are not joined to feeder radar/airway routes: hence, you can't use it unless it's emergency and usually it's way under Airway MEA or Radar MVA, so that is the gotcha, also I recall FAA TERPS refer to TAArea while ICAO PANS-OPS use TAAltitude, this highlights how airport terminal GPS procedures are joined to the rest of the airspace structure and how conventional radar/airway routes mix with GPS routes (RNAV or RNP), it's a fiasco when you look how each country treat a descent to TAA or has implemented GPS procedures in exiting structures, many countries are allergic to direct IAF along the magenta with descent to TAA altitude, as it takes you off the ATC grid !

Maybe a bit of off topic and it's not YES/NO answer to the question but gives some color why you can do it in FAA land and why ATC expects you to do so, you always "remain in the ATC system"

 

 

 

 

Edited December 1, 2022 by Ibra

[jlunseth]

Well, the better question is when can you descend to the minimum sector altitude in light of ATC’s instructions. My experience is that they always assign an altitude until you receive something like “Maintain 4,000 until established on a published segment of the approach, cleared the RNAV x.” But is a sector a published segment of the approach? I don’t think so, the way I understand it, published segments means getting on one of the course lines, the TAA is just an area. So in practice the TAA minimum altitudes mean very little, I really don’t ever remember having been allowed by ATC to fly the TAA minimum, I have always been assigned an altitude until on a published segment.

As far as “shall” and “may” are concerned, one factor not to forget is the nature of the document in which the word appears. If in a regulation or statute, it is binding. But the AIM is not supposed to be a binding document. What it is in that regard is a little murky. An AC or an SB are advisory. Yes you would be in big trouble if you did not follow it and an accident resulted because the document would be pulled out as evidence of due care. But they are not binding in the way a regulation is. And as far as regulations are concerned, we have an unfortunate legal doctrine called Chevron deference that basically says that a regulation means what the regulatory body says it means. So a reg can use “may,” but if the FAA says it means “shall” then it means “shall.”

[GeeBee]

You are flying an airplane, not an Otis elevator and the regulations reflect that.

 

[AIREMATT]

3 hours ago, jlunseth said:

But is a sector a published segment of the approach? I don’t think so, the way I understand it, published segments means getting on one of the course lines, the TAA is just an area. So in practice the TAA minimum altitudes mean very little, I really don’t ever remember having been allowed by ATC to fly the TAA minimum, I have always been assigned an altitude until on a published segment.

I think that is a published segment of the approach-albeit an area rather than a line, but a useable minimum altitude that as long as I’m cleared for the approach, I can stay above up to my last assigned altitude to stay on top of clouds in smooth air, or out of icing conditions, or because I choose to for any other operational reason. If I need to be lower to make the approach a normal comfortable profile I can opt to start down to the TAA altitude when I am in the sector and cleared for the approach.

I have just seen some writings in other sites and Mooney Flyer saying we are expected to  or must descend to the TAA when in the sector rather than it being pilots discretion after being cleared for the approach.

 

[rbp]

2 hours ago, AIREMATT said:

I think that is a published segment of the approach-albeit an area rather than a line,

I agree with this. Note that approach segments are not "lines", but "tubes" and "cones" formed by "line."

A TAA area is just a much wider "shape", with better accuracy. see attached

[PT20J]

6 hours ago, jlunseth said:

Well, the better question is when can you descend to the minimum sector altitude in light of ATC’s instructions. My experience is that they always assign an altitude until you receive something like “Maintain 4,000 until established on a published segment of the approach, cleared the RNAV x.” But is a sector a published segment of the approach? I don’t think so, the way I understand it, published segments means getting on one of the course lines, the TAA is just an area. So in practice the TAA minimum altitudes mean very little, I really don’t ever remember having been allowed by ATC to fly the TAA minimum, I have always been assigned an altitude until on a published segment.

Look at the excerpt I posted above from 7110.65. The note that begins at the bottom of page 4-8-5 states: "Aircraft that are within the lateral boundary of a TAA, and at or above the TAA minimum altitude, are established on the approach and may be issued an approach clearance without an altitude restriction."

[midlifeflyer]

3 hours ago, AIREMATT said:

I think that is a published segment of the approach-albeit an area rather than a line, but a useable minimum altitude that as long as I’m cleared for the approach, I can stay above up to my last assigned altitude to stay on top of clouds in smooth air, or out of icing conditions, or because I choose to for any other operational reason. If I need to be lower to make the approach a normal comfortable profile I can opt to start down to the TAA altitude when I am in the sector and cleared for the approach.

 

 

Exactly.

[jlunseth]

3 hours ago, PT20J said:

Look at the excerpt I posted above from 7110.65. The note that begins at the bottom of page 4-8-5 states: "Aircraft that are within the lateral boundary of a TAA, and at or above the TAA minimum altitude, are established on the approach and may be issued an approach clearance without an altitude restriction."

Well, ok, I looked at it, but it does not say that when ATC assigns you an altitude you can freely deviate downward from it so long as you are within a TAA. It allows the controller to issue a clearance without an altitude restriction, it does not authorize a pilot to break one, and in my example they did issue an altitude restriction. They said “maintain 4,000.” So am I allowed to go down to 3,000 assuming that is the TAA minimum? If they simply issued the instruction “cleared the RNAV x approach” I would understand it, I am within the TAA, cleared for the approach and can follow the chart. But that is not the instruction they give, they invariably assign an altitude. TAAs are pretty big, that would mean that 30 miles out from the FAF I can descend to 3,000 if want, notwithstanding the “maintain 4,000.” Also, virtually every time I have received that instruction in connection with an RNAV I am already inside the 30 mile TAA or whatever the distance restriction happens to be.

I appreciate the reference though, it is helpful. 

[PT20J]

4 minutes ago, jlunseth said:

Well, ok, I looked at it, but it does not say that when ATC assigns you an altitude you can freely deviate downward from it so long as you are within a TAA. It allows the controller to issue a clearance without an altitude restriction, it does not authorize a pilot to break one, and in my example they did issue an altitude restriction. They said “maintain 4,000.” So am I allowed to go down to 3,000 assuming that is the TAA minimum? If they simply issued the instruction “cleared the RNAV x approach” I would understand it, I am within the TAA, cleared for the approach and can follow the chart. But that is not the instruction they give, they invariably assign an altitude. TAAs are pretty big, that would mean that 30 miles out from the FAF I can descend to 3,000 if want, notwithstanding the “maintain 4,000.” Also, virtually every time I have received that instruction in connection with an RNAV I am already inside the 30 mile TAA or whatever the distance restriction happens to be.

I appreciate the reference though, it is helpful. 

I think you are overthinking this  

A published segment of an IAP will have a published minimum altitude.

If you are on a published segment and cleared for the approach you may descend to the published altitude.

If you are within the TAA you are on a published segment and may descend to the published altitude when cleared.

Only if you are NOT on a published segment when cleared for the approach must the controller issue an altitude to maintain until established on a published segment.