The hemispherical rule and altitude at pilots discretion

[David Megginson]

They absolutely can and the pilot would be wise to comply.

I think we're saying the same thing different ways. De facto, because you can terminate FF in class E at any time (if you're VFR), or not request it in the first place, ATC can't mandate you to fly at a specific altitude in class E (or if they do, you can terminate it immediately simply by cancelling flight following). But it would be poor airmanship to ignore them, because they're trying to keep you away from other traffic, which is very much in your interest too.

 

[David Megginson]

Why not?
Not good airmanship and not legal.

Perhaps change that to "force you to fly at a specific altitude in class E when you're VFR". They can't, because even if you did have flight following (which is what, I think, your post is assuming), as soon as they assigned you that altitude you could say "Alfa 1 2 terminating flight following" and that would be the end of it. It would also be horrifically-bad airmanship, though, and that matters more than the letter of the law.

 

[David Megginson]

I have been assigned wafdof by atc several times....but then it's their idea and not mine (ie it's ok when they need it!) ps not all atc is familiar with the term, I found out.

Yes, absolutely normal for me too, when I'm just outside their terminal airspace. I'm not in their airspace yet, but I'm going to be in a few minutes, so it makes sense for me to enter it at an altitude that fits in with their other traffic.

I've also been requested to maintain a WAFDOF for a few minutes by ATC when I've been VFR with flight following, typically because they have IFR traffic that will be crossing my flight path just above or below me.

 

[Lindberg]

Perhaps change that to "force you to fly at a specific altitude in class E when you're VFR". They can't, because even if you did have flight following (which is what, I think, your post is assuming), as soon as they assigned you that altitude you could say "Alfa 1 2 terminating flight following" and that would be the end of it. It would also be horrifically-bad airmanship, though, and that matters more than the letter of the law.

Terminating flight following doesn't get you out of following ATC instructions.

 

[Salty]

Terminating flight following doesn't get you out of following ATC instructions.

After the words "frequency change approved", how are they going to give you instructions?

 

[EdFred]

Perhaps change that to "force you to fly at a specific altitude in class E when you're VFR". They can't, because even if you did have flight following (which is what, I think, your post is assuming), as soon as they assigned you that altitude you could say "Alfa 1 2 terminating flight following" and that would be the end of it. It would also be horrifically-bad airmanship, though, and that matters more than the letter of the law.

Yes, they can. See the legal interpretation already posted in this thread.

 

[cowman]

I know it’s a different situation but I’ve had a couple of IFR flights into FL going easterly where ATC changed me to an even altitude and left me there. Don’t know why, assume for spacing or something.

 

[Lindberg]

After the words "frequency change approved", how are they going to give you instructions?

In his scenario, they've already given you an instruction.

 

[Salty]

In his scenario, they've already given you an instruction.

Give me an example of an instruction they would give you where they would tell you "frequency change approved" before they've released you from that instruction. Not saying there isn't one, but I'd be surprised. I don't think they'd cancel FF or IFR until a restriction could be lifted.

 

[EdFred]

I know it’s a different situation but I’ve had a couple of IFR flights into FL going easterly where ATC changed me to an even altitude and left me there. Don’t know why, assume for spacing or something.

Was headed to SDF this summer. They gave me 7000 for traffic even though I was slightly west bound. After traffic was no longer a factor they asked if I wanted to stay at 7 or go to 6 or 8. So I stayed at 7 until TOD.

 

[Bill]

Was headed to SDF this summer. They gave me 7000 for traffic even though I was slightly west bound. After traffic was no longer a factor they asked if I wanted to stay at 7 or go to 6 or 8. So I stayed at 7 until TOD.

Joey Bag of Donuts Pilot actually waited a good while after traffic was no factor to contact ATC about the 5500 assignment. Had Joe not contacted ATC, he doubts they would have issued any other calls until handoff to the next facility.

 

[kath]

I know it’s a different situation but I’ve had a couple of IFR flights into FL going easterly where ATC changed me to an even altitude and left me there. Don’t know why, assume for spacing or something.

My understanding is that Florida has its own different standard IFR altitudes, based on North vs. South, instead of East vs. West.
Because it's such a Northy-Southy shaped state.

 

[Salty]

My understanding is that Florida has its own different standard IFR altitudes, based on North vs. South, instead of East vs. West.
Because it's such a Northy-Southy shaped state.

I've never heard any official thing like this, but I was once on FF and someone coming the other way complained about the altitude I was at (I was at the correct altitude, but he was going with 10 degrees of 180 and I was going within 10 degrees of 360 so we were still pretty much head on. Anyway, the controller told him "in Florida the hemispherical rule doesn't really work, and we don't worry that much about it"

 

[Ed Haywood]

If altitude were at your discretion, why would you use that discretion to select an altitude that makes a head-on conflict more likely?

 

[cowman]

If altitude were at your discretion, why would you use that discretion to select an altitude that makes a head-on conflict more likely?

You're flying easterly so you're supposed to be at odd altitudes. There are clouds preventing you from climbing up to 5,500. Down at 3,500 it's bumpy and you're within 3,000 AGL so traffic could be coming from any direction anyway.... or you need a little more altitude to clear a restricted area/some hazard. There are many reasons why this may come up.

 

[John Collins]

Agree, and in this case ATC asked Joe to climb to 5500 to resolve a potential traffic conflict. Joe told me he was flying a heading of 330, the conflicting traffic was at 4500 flying heading of 200.

Based on your prior comment regarding the terrain elevation, the hemispheric rule would kick in at 5800 feet to 6200 feet, so 5500 feet is a VFR altitude that is not relevant to the hemispheric rule as the lowest hemispheric rule direction of VFR flight doesn't begin until 6500 feet or higher. So you can proceed at either 5500 or 6500 and in either case, keep your eyes out.

 

[John Collins]

My understanding is that Florida has its own different standard IFR altitudes, based on North vs. South, instead of East vs. West.
Because it's such a Northy-Southy shaped state.

There are no hemispheric rules in the regulations for IFR in controlled airspace although they are most often the altitudes assigned by ATC. One can always request a so called wrong way altitude and as you indicate, IFR in Florida uses their own IFR direction of flight default altitudes.

 

[Lindberg]

Give me an example of an instruction they would give you where they would tell you "frequency change approved" before they've released you from that instruction. Not saying there isn't one, but I'd be surprised. I don't think they'd cancel FF or IFR until a restriction could be lifted.

You can make up whatever hypothetical you want. But I responded to this incorrect statement:

De facto, because you can terminate FF in class E at any time (if you're VFR), or not request it in the first place, ATC can't mandate you to fly at a specific altitude in class E (or if they do, you can terminate it immediately simply by cancelling flight following).

Both parts of the bolded clause are false.

 

[Half Fast]

You can make up whatever hypothetical you want. But I responded to this incorrect statement:

Both parts of the bolded sentence are false.

You confuse me, sir.

Are you saying a pilot can not terminate FF at will?

Or if he does, that he must then adhere to ATC’s last instruction forever?

 

[EdFred]

You confuse me, sir.

Are you saying a pilot can not terminate FF at will?

Or if he does, that he must then adhere to ATC’s last instruction forever?

If a pilot is issued an instruction under FF, and he cancels saying "I'm cancelling radar services" and doesn't wait for a response confirming it because he flies a 210, then yeah, he's bound by that last instruction until he runs out of fuel.


Before ATC terminates radar services, they will release you from the last instruction.

Basically if you're issued an instruction, there is not an end around because you didn't want to deviate 20 degrees due to conflicting traffic.

 

[Salty]

You confuse me, sir.

Are you saying a pilot can not terminate FF at will?

Or if he does, that he must then adhere to ATC’s last instruction forever?

I don't know what Lindberg is saying, but I think you can't just stop talking to them, you have to wait for them to say "frequency change approved" and until then, you're obligated to follow their instructions. My guess is that's what Lindberg means.

So, you can request termination of FF at will, but it's not necessarily going to be terminated immediately.

 

[midlifeflyer]

You confuse me, sir.

Are you saying a pilot can not terminate FF at will?

Or if he does, that he must then adhere to ATC’s last instruction forever?

You can ask and they can let you go. They can also say, "stay with me." But the real error is
"ATC can't mandate you to fly at a specific altitude in class E"

Class E is controlled airspace, aka "an area in which air traffic control is exercised" and 91.123 says:

"Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised."

The 2013 Karas letter from the Chief Counsel is pretty clear what that means.

 

[Lindberg]

So, you can request termination of FF at will, but it's not necessarily going to be terminated immediately.

It doesn't matter if you terminate flight following because 91.123[(b)] doesn't say anything about being on flight following. Whether you're on flight following or not, if you are in controlled airspace, you must follow ATC instructions.

 

[David Megginson]

Terminating flight following doesn't get you out of following ATC instructions.

How so, for a VFR flight not in class A,B,C,D or an ADIZ, etc?

But I also feel like I'm backing myself into a silly devil's advocate position here, because I still think that any decent pilot should follow the ATC requests regardless, and if they don't, they could still be called to account for bad airmanship if they caused an incident.

I'll also note that I'm Canadian, so while our air regs are almost all the same as yours, there could be some wording in yours (perhaps not even intentional) that people who like that kind of debate can jump on.

I do see a note in your AIM that a participating VFR flight getting "Radar traffic information service" (flight following) specifically in a TSRA has to follow ATC altitude instructions, but a) there aren't many TSRAs left in the US (many/most replaced with class B or C), so that would rarely apply; and b) they could still choose to stop participating even if they were in a TSRA (though it would be a bad idea to do that).

 

[David Megginson]

In his scenario, they've already given you an instruction.

As I mentioned before, it's a bit silly to quibble over this, since we both agree that it's a good idea to follow ATC altitude requests anyway, but let's see where this leads:

• I'm flying VFR into an old-style TSRA, the only place this rule seems to apply according to the U.S. AIM (and TSRAs are getting increasingly rare).
• I choose to participate in the TSRA's Radar Traffic Information Service (flight following)
  
• ATC instructs me to maintain 3,000 ft.
• I comply with the instruction (for the sake of argument), and then stop participating in the TSRA's Radar Traffic Information Service.
• 5 minutes later, I'm approaching my destination airport, under the TSRA but not inside class C or D.
• According to the claims a couple of people are making in this thread, I can't descend and land, because the last ATC instruction I received before I stopped participating was to maintain 3,000 ft, so I just circle until I run out of fuel. (???)

 

[David Megginson]

It doesn't matter if you terminate flight following because 91.123(c) doesn't say anything about being on flight following. Whether you're on flight following or not, if you are in controlled airspace, you must follow ATC instructions.

Remember that we're talking about VFR in class E airspace, not IFR. Class E is still controlled airspace, but except in a few special exceptions, ATC cannot give instructions to VFR aircraft in class E, only issue requests. You'd have to be a pretty dim pilot to ignore those requests, though.

 

[EdFred]

Remember that we're talking about VFR in class E airspace, not IFR. Class E is still controlled airspace, but except in a few special exceptions, ATC cannot give instructions to VFR aircraft in class E, only issue requests. You'd have to be a pretty dim pilot to ignore those requests, though.

Read the damn interpretation letter.

 

[Half Fast]

Remember that we're talking about VFR in class E airspace, not IFR. Class E is still controlled airspace, but except in a few special exceptions, ATC cannot give instructions to VFR aircraft in class E, only issue requests. You'd have to be a pretty dim pilot to ignore those requests, though.

Agreed, and keep in mind you’re not even required to be listening to ATC’s frequency (or have a radio, for that matter), so how can you be required to obey ATC in class E?

Granted if you were on FF you have to advise them you are terminating and they have to approve the frequency change, but these absolute statements that a VFR pilot has to obey ATC in class E seem silly.

 

[Half Fast]

Read the damn interpretation letter.

From the letter:

A pilot flying VFR in Class E airspace, which is controlled airspace, is not required to communicate with ATC; however, if a pilot is communicating with ATC and ATC issues an instruction, the pilot must comply with that instruction.

Compliance with ATC hinges on that “if” statement.

 

[EdFred]

Yeah if they give you an instruction you have to follow it. Why is that so hard to understand?

 

[midlifeflyer]

From the letter:

A pilot flying VFR in Class E airspace, which is controlled airspace, is not required to communicate with ATC; however, if a pilot is communicating with ATC and ATC issues an instruction, the pilot must comply with that instruction.

Compliance with ATC hinges on that “if” statement.

Yep. If you are not already talking with them it's hard for them to give you an instruction.

 

[RyanB]

It doesn't matter if you terminate flight following because 91.123(c) doesn't say anything about being on flight following.

That assumes the pilot deviates from a clearance or instruction, which the OP did not do. He complied with their request.

 

[Palmpilot]

...Granted if you were on FF you have to advise them you are terminating and they have to approve the frequency change...

Not in class E (although it would be rude not to do so). 91.183 says that "Unless otherwise authorized by ATC, the pilot in command of each aircraft operated under IFR in controlled airspace must ensure that a continuous watch is maintained on the appropriate frequency...," but there's no corresponding rule for VFR aircraft in class E airspace.

 

[Palmpilot]

Remember that we're talking about VFR in class E airspace, not IFR. Class E is still controlled airspace, but except in a few special exceptions, ATC cannot give instructions to VFR aircraft in class E, only issue requests. ...

I'll take your word for that when flying in Canadian airspace, but in U.S. airspace, 14 CFR 91.123(b) says you have to comply.

 

[midlifeflyer]

Not in class E (although it would be rude not to do so). 91.183 says that "Unless otherwise authorized by ATC, the pilot in command of each aircraft operated under IFR in controlled airspace must ensure that a continuous watch is maintained on the appropriate frequency...," but there's no corresponding rule for VFR aircraft in class E airspace.

Not sure how that means you can just turn off the radio once you have initiated ATC communications.

 

[Dana]

Earlier this year I was going into a private field within a class D. While I was still outside the class D the tower steered me all over the place to avoid departing traffic while telling me to stay at or below 1000' (I was over the water). But they must have been uncertain where I was because they kept asking me for my position, I have no transponder.

Really, the hemispherical rule just insures that all midair collisions will happen at an angle of 179° or less...

 

[Half Fast]

Really, the hemispherical rule just insures that all midair collisions will happen at an angle of 179° or less...

Or, 181 degrees or more....

 

[sarangan]

Not in class E (although it would be rude not to do so). 91.183 says that "Unless otherwise authorized by ATC, the pilot in command of each aircraft operated under IFR in controlled airspace must ensure that a continuous watch is maintained on the appropriate frequency...," but there's no corresponding rule for VFR aircraft in class E airspace.

91.123b: Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised.

Class E is controlled airspace. Although radio communication is not required for VFR, once you have received ATC instruction you have to comply with it.

 

[Velocity173]

91.123b: Except in an emergency, no person may operate an aircraft contrary to an ATC instruction in an area in which air traffic control is exercised.

Class E is controlled airspace. Although radio communication is not required for VFR, once you have received ATC instruction you have to comply with it.

But that instruction only applies during basic radar services. That’s an optional service in airspace that doesn’t require two way comms. It’s not something a controller is allowed to force upon a pilot. It would be like a pilot who elects to cancel IFR because they want to save time but the controller won’t let them because they feel it’s in their best interest to stay IFR. Completely improper.

 

[Palmpilot]

Not sure how that means you can just turn off the radio once you have initiated ATC communications.

I'm not saying it's a good idea, but what reg says you can't?