The hemispherical rule and altitude at pilots discretion

[Palmpilot]

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

The hemispheric rule originated before GPS was common in aviation. As a result, I suspect that a much higher percentage of en route flying was along airways, thus making the problem you describe much more rare.

 

[Palmpilot]

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.

You have to comply with instructions, but unless the controller tells you not to, what rule prohibits a pilot flying VFR in class E from changing frequencies (or even turning off the radio) without getting permission?

(And again, I'm not saying this is a good idea.)

 

[midlifeflyer]

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

Good point. Kind of like not closing a VFR (or for that matter, IFR) flight plan.

 

[Lindberg]

You have to comply with instructions, but unless the controller tells you not to, what rule prohibits a pilot flying VFR in class E from changing frequencies (or even turning off the radio) without getting permission?

(And again, I'm not saying this is a good idea.)

I guess nothing. But if you switch right after ATC says, "Fly heading 160," you'll never hear him say, "Resume own navigation."

 

[Palmpilot]

I guess nothing. But if you switch right after ATC says, "Fly heading 160," you'll never hear him say, "Resume own navigation."

Yes, I think waiting for that would at least resolve the gray area about how long you would need to continue following the last instruction received.

 

[Kritchlow]

I have not flown VFR in many years, but I recall only being issued headings while in class C/B airspace. While in E, I always was given “suggest heading xxx”. A suggestion, not directive.

 

[Velocity173]

Yes, I think waiting for that would at least resolve the gray area about how long you would need to continue following the last instruction received.

I received a vector from ATL Center once and immediately canceled FF right after. All I got was a radar services terminated, frequency change approved. Should I have followed a radar vector when I’m no longer receiving radar services?

 

[Velocity173]

I have not flown VFR in many years, but I recall only being issued headings while in class C/B airspace. While in E, I always was given “suggest heading xxx”. A suggestion, not directive.

And that’s how it should be. I’ve seen FF become more heavy handed over the years and overriding basic radar services requirements. Under VFR, I’m all about ATC giving the pilot a picture of what’s around them and letting the PIC decide a CoA. I don’t agree with the CC letter but it is what it is.

 

[Palmpilot]

I received a vector from ATL Center once and immediately canceled FF right after. All I got was a radar services terminated, frequency change approved. Should I have followed a radar vector when I’m no longer receiving radar services?

Personally, I would interpret "frequency change approved" as permission to resume my own navigation unless explicitly instructed otherwise. (However I'm guessing that there's no provision in the ATC manual to say "frequency change approved, but stay on your present heading for five miles," for example.)

 

[midlifeflyer]

I have not flown VFR in many years, but I recall only being issued headings while in class C/B airspace. While in E, I always was given “suggest heading xxx”. A suggestion, not directive.

I've gotten instructions in Class E. Not all the time but enough tot think of them as not too unusual. Typically its from a TRACON controller trying to keep approach/departure corridors (which are not in a B, C, or D) clear. Sometimes a heading, sometimes an altitude. sometimes an instruction to remain e/w/n/s of something like a landmark or highway. I recall getting them fairly regularly (not all the time) when I was in the Denver area and just got one about three weeks ago outside of the Greensboro NC Class C.

 

[NealRomeoGolf]

I get headings and altitude restrictions all the time under the Bravo in Chicago, which should be class E. They don't like me messing with the Southwest iron.

 

[Radar Contact]

And that’s how it should be. I’ve seen FF become more heavy handed over the years and overriding basic radar services requirements. Under VFR, I’m all about ATC giving the pilot a picture of what’s around them and letting the PIC decide a CoA. I don’t agree with the CC letter but it is what it is.

I usually only do it under 2 circumstances.
1) if I don’t have time to keep watching and issuing continuous traffic updates.
i.e. you’re going north along the lake shore with conflicting traffic south at similar altitude while I’m vectoring a busy final at MDW. I may give you 20 right to ensure y’all don’t touch and quickly delete it while vectoring the final.
2) to avoid to impending TCAS alert an equipped aircraft is going to get because of you.
i.e. the RNAV Y/Z 22L at MDW with VFR traffic along the shore. They can both be at the same spot. We have to report these and there’s usually no point in alarming a flight crew with an automated alert they have to comply with while they are trying to land.

In these cases I’ve never had the pilot under FF seem upset. I too have terminated FF while flying because of seemingly over burdensome vectors/altitudes. It’s rare.

 

[Lindberg]

I've gotten instructions in Class E. Not all the time but enough tot think of them as not too unusual. Typically its from a TRACON controller trying to keep approach/departure corridors (which are not in a B, C, or D) clear. Sometimes a heading, sometimes an altitude. sometimes an instruction to remain e/w/n/s of something like a landmark or highway. I recall getting them fairly regularly (not all the time) when I was in the Denver area and just got one about three weeks ago outside of the Greensboro NC Class C.

Same. Flying under or around the DFW class B, I'll often get headings to stay away from approaches and departures.

 

[Velocity173]

I usually only do it under 2 circumstances.
1) if I don’t have time to keep watching and issuing continuous traffic updates.
i.e. you’re going north along the lake shore with conflicting traffic south at similar altitude while I’m vectoring a busy final at MDW. I may give you 20 right to ensure y’all don’t touch and quickly delete it while vectoring the final.
2) to avoid to impending TCAS alert an equipped aircraft is going to get because of you.
i.e. the RNAV Y/Z 22L at MDW with VFR traffic along the shore. They can both be at the same spot. We have to report these and there’s usually no point in alarming a flight crew with an automated alert they have to comply with while they are trying to land.

In these cases I’ve never had the pilot under FF seem upset. I too have terminated FF while flying because of seemingly over burdensome vectors/altitudes. It’s rare.

Yeah I can understand with those scenarios. I used to just give them an option in similar situations. I’ve had a few VFRs that would hang around the initial for the overhead. I told them that they’re in direct conflict with inbound traffic to the air station and they either needed to adjust altitude or maneuver in another area or I’ll have to terminate. They'll move.

Now enroute VFRs? Show them the traffic. They don’t see the traffic and it looks like converging, suggest a heading. If they still don’t want it, issue a safety alert. 99 % of the time they’ll take the suggested heading though.

 

[Dana]

The hemispheric rule originated before GPS was common in aviation. As a result, I suspect that a much higher percentage of en route flying was along airways, thus making the problem you describe much more rare.

Good point. I was, of course, being sarcastic. Actually I think I got that crack from Richard Bach. But having never owned a plane with a VOR receiver, I don't think about airways much except where not to do aerobatics, and I rarely fly above 3000' AGL so the hemispherical cruising rule doesn't apply.

 

[Palmpilot]

Good point. I was, of course, being sarcastic. Actually I think I got that crack from Richard Bach. But having never owned a plane with a VOR receiver, I don't think about airways much except where not to do aerobatics, and I rarely fly above 3000' AGL so the hemispherical cruising rule doesn't apply.

Sarcastic or not, it was a good point in today's world of ubiquitous GPS and random routing, and one that I've thought about as well.