IFR hemispheric altitudes

[Dave S.]

91.177 gives appropriate altitudes to be used at all altitudes in uncontrolled airspace.

The question is simple...why are there uncontrolled airspace altitude requirements for high altitudes where there is no uncontrolled airspace?

tex

 

[MauleSkinner]

91.177 gives appropriate altitudes to be used at all altitudes in uncontrolled airspace.

The question is simple...why are there uncontrolled airspace altitude requirements for high altitudes where there is no uncontrolled airspace?

tex

The rules were written when that uncontrolled airspace existed.

 

[Clip4]

91.177 gives minimum IFR altitudes. 91.179 is what you referenced.
Search uncontrolled airspace over high seas.

 

[Dave S.]

Your right my mistake...91.179.

But the FAA doesn’t dictate policy over non-territorial high seas...ICAO does, I believe.

Can you give an example of previous rules in the past when uncontrolled airspace existed high enough to require uncontrolled airspace hemispheric rules. I’m trying to get to the bottom of this for my class that I teach.

Any help would be appreciated.

tex

 

[Ravioli]

Perhaps a stupid question, but hey, it's just me.

When flying IFR, you are flying an assigned altitude. Why would the hemispheric rules be needed at that point?

 

[Dave S.]

I am a 36 year veteran air traffic controller as well as CFII, MEI. Any controlled airspace IFR altitude you fly is what ATC assigns you. In fact paragraph A of .179 say as much. There is no requirement to choose or file for any specific altitude based on direction. ATC has a 7110.65 requirement to choose an altitude based on direction but pilots do not. In fact paragraph B confines direction based altitude choices to uncontrolled airspace.

So why is there a rule that specifies direction based altitudes in uncontrolled airspace up to FL410 or above when there is no uncontrolled airspace that I can think of above FL180?

Maule Skinner suggested that once upon a time there may have been high altitude uncontrolled airspace to which 179 would have applied. 179 was first drafted and accepted in its current state in 1983.

Can any one explain this please?

tex

 

[luvflyin]

Your right my mistake...91.179.

But the FAA doesn’t dictate policy over non-territorial high seas...ICAO does, I believe.

Can you give an example of previous rules in the past when uncontrolled airspace existed high enough to require uncontrolled airspace hemispheric rules. I’m trying to get to the bottom of this for my class that I teach.

Any help would be appreciated.

tex

It wasn't all that many years ago that there was quite a bit of uncontrolled airspace at higher altitudes up to 18,000 where the Positive Control Area started. You saw a lot of places where Controlled Airspace was in chunks 8 miles wide, 4 either side of Airways and the space between was uncontrolled. Then along came RNAV and everyone was flying direct to everywhere. ATC would tell pilots when they were leaving Controlled Airspace and where to call again to start getting ATC service again. This was causing all kinds of controversy so the campaign was started to get rid of Uncontrolled Airspace above 1200 AGL. It took a while. There is effectively no Uncontrolled Airspace left in the lower 48 that is in chunks big enough to be usable for Enroute flight.

EDIT: 18,000 and Positive Control Area should be 14,500 and Continental Control Area. See post #11 below

 

[Dave S.]

Yeah, based on my research I have thought for awhile now that this rule is essential useless I. Present day practice. Yould be surprised how many pilots I speak to at meetings believe that 91.179b dictates their altitude choice. They are shocked and dont understand why they always file based on hemispheric altitudes.

This probably stems from the fact that controllers, who by rule must use altitudes based on direction, reinforce the West/even, east/odd culture, when, in fact, paragragh A says it all in simple terms.

tex

 

[luvflyin]

Yeah, based on my research I have thought for awhile now that this rule is essential useless I. Present day practice. Yould be surprised how many pilots I speak to at meetings believe that 91.179b dictates their altitude choice. They are shocked and dont understand why they always file based on hemispheric altitudes.

This probably stems from the fact that controllers, who by rule must use altitudes based on direction, reinforce the West/even, east/odd culture, when, in fact, paragragh A says it all in simple terms.

tex

It wouldn't be 91.179b that dictates it. But ATC has the same Hemispheric rule for assigning altitudes. So you may as well file for something you're likely to be assigned.

 

[Dave S.]

That’s what I said. “B” doesn’t dictate it but many have been under that belief. Which is reinforced by ATC’s choice of altitudes. And yes, they therefore continue to file for those altitudes based on their experience that those are the altitudes they will be assigned which is true. In other words, they are getting the right answer but for the wrong reason...many of them.

tex

 

[flyingron]

It wasn't all that many years ago that there was quite a bit of uncontrolled airspace at higher altitudes up to 18,000

Well, not 18,000, but 14,500. Remember the "Continental Control Area" makes everything over 14,500 (and over 1500 AGL) in the contiguous 48 controlled airspace. Of course, the tallest peak in the lower 48 is right at 14,500 to begin with (go figure), so if you wanted to cross Mt. Whitney by only 1500', you could do so in class G.

 

[Dave S.]

I’m still hoping for an explanation of why there is a need for those high altitude rules for uncontrolled airspace. Where is it possible to be in uncontrolled airspace that the FAA has jurisdiction over and where 91.179 applies at, say, FL300? Now or anytime in the past.

Give me an example of where I must apply 91.179b above,say, FL300

tex

 

[midlifeflyer]

Perhaps a stupid question, but hey, it's just me.

When flying IFR, you are flying an assigned altitude. Why would the hemispheric rules be needed at that point?

@MauleSkinner answered your question. There was a time when large areas of uncontrolled airspace existed in the US. Technically, IFR was legal in that airspace with no filed flight plan, no ATC clearance, and altitudes chosen by the pilot based on 91.179.

Funny how these things come up, timing wise. I just finished an article on the subject slated for an upcoming IFR Magazine issue.

 

[luvflyin]

I’m still hoping for an explanation of why there is a need for those high altitude rules for uncontrolled airspace. Where is it possible to be in uncontrolled airspace that the FAA has jurisdiction over and where 91.179 applies at, say, FL300? Now or anytime in the past.

Give me an example of where I must apply 91.179b above,say, FL300

tex

In the past there was some. The Positive Control Area, know known as Class A Airspace, hasn't been around forever. I don't know the date it was invented. The Continental Control Area @flyingron mentions above in post #11 only went as far West as Longitude 160 degrees West, so there was a lot in Alaska. The CCA still exists, it just got renamed when Alphabet Soup Airspace designation happened back in the 90's. See AIM 3-2-6 d. 1. That's the definition of the old CCA.

 

[MauleSkinner]

I’m still hoping for an explanation of why there is a need for those high altitude rules for uncontrolled airspace. Where is it possible to be in uncontrolled airspace that the FAA has jurisdiction over and where 91.179 applies at, say, FL300? Now or anytime in the past.

Give me an example of where I must apply 91.179b above,say, FL300

tex

Currently there are no examples.

The rule is there simply because the FAA hasn’t changed it, and probably won’t feel the need to do so in our lifetimes.

 

[luvflyin]

Currently there are no examples below FL600.

The rule is there simply because the FAA hasn’t changed it, and probably won’t feel the need to do so in our lifetimes.

I was thinking about FL600 to because Class A ends there, but it's E above that. AIM 3-2-1 d. 2.

 

[iamtheari]

The FAR/AIM app on my phone shows that 91.179 was adopted in 1989 (though I suspect it was carried over from a different codification that year, not written from scratch) with amendments in 2003 and 2007. 91.179(b)(4) applies to uncontrolled RVSM airspace. Has there ever been uncontrolled RVSM airspace?

 

[MauleSkinner]

I was thinking about FL600 to because Class A ends there, but it's E above that. AIM 3-2-1 d. 2.

You are correct...thanks. I’m correcting my post.

 

[MauleSkinner]

The FAR/AIM app on my phone shows that 91.179 was adopted in 1989 (though I suspect it was carried over from a different codification that year, not written from scratch) with amendments in 2003 and 2007. 91.179(b)(4) applies to uncontrolled RVSM airspace. Has there ever been uncontrolled RVSM airspace?

No...RVSM didn’t previously exist in the US.

 

[timwinters]

I think @EdFred needs to create a flow chart

 

[luvflyin]

Well, not 18,000, but 14,500. Remember the "Continental Control Area" makes everything over 14,500 (and over 1500 AGL) in the contiguous 48 controlled airspace. Of course, the tallest peak in the lower 48 is right at 14,500 to begin with (go figure), so if you wanted to cross Mt. Whitney by only 1500', you could do so in class G.

Yup. My post edited

 

[dtuuri]

The diagram in my 1961 CAR book shows the IFR altitudes within controlled airspace are for flight planning purposes only.

It shows the IFR altitudes below FL290 apply to within the continental limits of the US, Alaska, Territories and Possessions. It shows FL examples "FL240, FL260 and FL280" with a note that all airspace above FL240 within the Continental US is controlled airspace.

Above FL290, the altitudes are separated by 4000 feet as FL310, FL350, etc. and applies to Alaska, Territories and Possessions.

IIRC, the Continental Control Area used to be FL240 before it was lowered to 14,500 MSL.

 

[apr911]

Perhaps a stupid question, but hey, it's just me.

When flying IFR, you are flying an assigned altitude. Why would the hemispheric rules be needed at that point?

The hemispheric rules matter because ATC follows the rules. As @luvflyin put it:

It wouldn't be 91.179b that dictates it. But ATC has the same Hemispheric rule for assigning altitudes. So you may as well file for something you're likely to be assigned.

In addition to filing for something you're likely to be assigned just to make it easier and not gum up the works, hemispheric rules still matter because the PIC is still responsible and the final authority for the safe conduct of the flight and the pilot of an aircraft on an Instrument Flight Plan is still technically responsible for "see and avoid" when not in IMC.

AIM 5-5-8 - See and Avoid, Pilot Responsibilities - When meteorological conditions permit, regardless of type of flight plan or whether or not under control of a radar facility, the pilot is responsible to see and avoid other traffic, terrain, or obstacles.

Though less relevant to the "hemispheric altitudes" question as you start reaching lower altitudes where a hemispheric altitude isnt flown and would normally be climbing/descending from the airport, Class C, D and TRSA airports provide differing levels of separation services, particularly in separating IFR/VFR traffic.

 

[Larry in TN]

why are there uncontrolled airspace altitude requirements for high altitudes where there is no uncontrolled airspace?

Aviation exists outside the confines of the 48 contiguous states.

In 2010/11 I was flying DC8s IFR to an airport where the airspace was uncontrolled below FL245. FJDG.

 

[luvflyin]

The hemispheric rules matter because ATC follows the rules. As @luvflyin put it:


In addition to filing for something you're likely to be assigned just to make it easier and not gum up the works, hemispheric rules still matter because the PIC is still responsible and the final authority for the safe conduct of the flight and the pilot of an aircraft on an Instrument Flight Plan is still technically responsible for "see and avoid" when not in IMC.

AIM 5-5-8 - See and Avoid, Pilot Responsibilities - When meteorological conditions permit, regardless of type of flight plan or whether or not under control of a radar facility, the pilot is responsible to see and avoid other traffic, terrain, or obstacles.

Though less relevant to the "hemispheric altitudes" question as you start reaching lower altitudes where a hemispheric altitude isnt flown and would normally be climbing/descending from the airport, Class C, D and TRSA airports provide differing levels of separation services, particularly in separating IFR/VFR traffic.

Yeah. When you get down in the Terminal Areas, the hemispheric thing is pretty much out the window. It's intent is about enroute flight. There are lots of areas where ATC doesn't comply with it literally when assigning altitudes. They keep it generally avoid opposite direction flows at the same altitude. When you get into the Northerly/Southerly flows of traffic there are a lot of cases of courses in say the 190 degree area that are flowing with courses in the 170 degree area. They will be on same odd/even plan. In the non panhandle part of Florida I'd bet the East/West thing is probably pretty much ignored and they have a de facto North/South hemispheric plan.

 

[flyingron]

In Florida, they actually turn it 90 degrees, mostly Northbound gets the odds and mostly southbound gets the even (or perhaps it's the other way around).
But basically:

1. File what you want.
2. Fly what you get.
3. Log what you need.

 

[Dave S.]

To address a couple of points...
Lara 4-5-2 tells controllers to assign altitudes based on the hemispheric rule which we do. Controllers can assign any altitude above MVA or MIA within his airspace and even into adjacent airspace even at wrong altitudes with coordination.

Dtuuri said he has a CAR book with a chart. I would love to see that. I know there is no example today or in the recent past. I wonder if anyone can give more specific examples in the more distant past.

tex

 

[apr911]

Aviation exists outside the confines of the 48 contiguous states.

In 2010/11 I was flying DC8s IFR to an airport where the airspace was uncontrolled below FL245. FJDG.

I was going to say “yeah but outside the US doesnt follow the FAR they follow ICAO and other local policies so why is the section of 91.179 we’re discussing required”

Glad you had an example! I forgot about US territories, protectorates and other locales that use US ATC resources and FAA rules for administering aviation in the area.

This applies to many of the remote pacific islands. Traffic is sparse and facilities lacking capability that the airspace is largely uncontrolled.

Good find!

 

[luvflyin]

To address a couple of points...
Lara 4-5-2 tells controllers to assign altitudes based on the hemispheric rule which we do. Controllers can assign any altitude above MVA or MIA within his airspace and even into adjacent airspace even at wrong altitudes with coordination.

Dtuuri said he has a CAR book with a chart. I would love to see that. I know there is no example today or in the recent past. I wonder if anyone can give more specific examples in the more distant past.

tex

Yup. And it is often done without coordination because it is in Letters of Agreement and SOP's.

What's a CAR book ?

 

[iamtheari]

No...RVSM didn’t previously exist in the US.

I’m utterly baffled why they revised this rule to explicitly apply to uncontrolled RVSM airspace. Methinks someone in the FAR codification department got confused and that confusion has infected the rest of us.

 

[iamtheari]

What's a CAR book ?

The Old Testament of the FARs.

 

[MauleSkinner]

What's a CAR book ?

Back when Aeronautics Regulations were Civil.

 

[dtuuri]

Dtuuri said he has a CAR book with a chart. I would love to see that. I know there is no example today or in the recent past. I wonder if anyone can give more specific examples in the more distant past.

Unless somebody else can provide it first, you'll have to wait until I get my scanner working.

 

[dtuuri]

Dtuuri said he has a CAR book with a chart. I would love to see that.

Sorry it took so long, but I'm not set up for scanning now or in the near future. This is the best I could do. (As an added bonus, it has the old Lost Comm rules CFIs and the Chief Counsel still teach today as though Amendment 91-189 never happened ):

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