TMA border is where exactly?

[LimaRomeo]

Maybe a foolish question but still, here we go: let's say I fly somewhere on FL085. I pass a big airport's TMA zone that goes from 2500 AMSL to FL085. Does that specific altitude of FL85 (8500 feet) belongs to the TMA controller and do I have to contact him, or does the TMA goes up to 8499 feet and is 8500 ft (FL085) not part of the TMA?
Thanks!

[Shunter]

Surely if you're flying in Europe in the flight levels you'd be flying the semicircular rule, being either FL080 or FL090 depending on your track, so it's somewhat of a moot point?

[Jim59]

I thought the quadrangle rule applied in the UK so any multiple of 500' is possible at the FLs we are talking about.

Personally I would allow a couple of hundred feet vertically between me and the controlled airspace - I cannot fly to within one foot!

[Keygrip]

It's quadrantal - and applies outside controlled airspace.

[dublinpilot]

Surely if you're flying in Europe in the flight levels you'd be flying the semicircular rule, being either FL080 or FL090 depending on your track, so it's somewhat of a moot point?

I don't see the relevance of your post to the question asked. :confused:

If controlled airspace is defined as sfc to FL080, and you're flying at FL080, then the poster is asking if you're inside or outside controlled airspace.
__________________

I seem to remember something somewhere from ICAO saying that where two different classes of airspace were defined at the same level, then the lower class applied, but I could be mistaken.

But as Jim says, it's really irrelevant. You're not going to fly at FL080 in such a case without talking to ATC. Even if it is class G, can you be sure that you'll never drop down to 7999ft?.....or you won't poke your wheels inside ;)

To do this would be asking for trouble, so if you wanted to go so close, you'd be talking to ATC.

So the question can really only be a theoretical one, not a practical one.

dp

[bookworm]

Under ICAO rules, the shared horizontal boundary between two different airspace classes is considered to be the less restrictive class. e.g. if the TMA is B and the airspace above is E, then the FL85 boundary is considered E. The UK apparently disagrees, and has non-compliant rules regarding airway bases.

[Shunter]

For the benefit of the unobservant, the OP is not in the UK. The quadrantal rule isn't universal you know.

[LimaRomeo]

Guys guys,
You reallu have to look into the books again I thinks ...

Let's say I fly VFR in the north France in uncontrolled airspace (G) at a magnetic heading of 185 degrees. In this case, the semicircular rule says: even+500': So FL85 because you are above transition altitude. This is right, trust me.

So there I am, cruisng at exactly FL85. Then this controlled airspace pops up in front of me, from SFC to FL85. Then again my question: is this specific level (8500 ft pressure alt) In our OUTSIDE the controled area?

LR

[BackPacker]

Guys guys,
You reallu have to look into the books again I thinks ...

LR, you are really not forcing us to look into our books for a question that you posed, do you? Why not look into the books yourself? You're not making any friends this way. Or are you an instructor believing we need extra training in looking up answers in books?

Furthermore, I think your question has been answered already:

Under ICAO rules, the shared horizontal boundary between two different airspace classes is considered to be the less restrictive class.

So if you're cruising at (exactly) FL85 and FL85 is defined as the boundary between two airspaces, you are technically in the airspace with the lowest restrictions. Ie. outside controlled airspace. But if you're at FL85 minus one hairs width, you're in controlled airspace without a clearance. Not good.

Personally (unless it's class A where you have no business flying VFR) I would make radio contact and for all practical purposes assume I was in the TMA and ask for clearance.

I do wonder where this situation is likely to occur though. I don't know any place in Europe where a bit of uncontrolled (class F/G) airspace sits *on top* of a (controlled) TMA.

[LimaRomeo]

Don't be offended by what I have written. This was not my intention. As you say, we're all here to make friends and learn things. I was a bit surprised by the fact that a lot of you think that FL85 isn't a legal VFR level. The quadrangle rule really is only a UK thing. The rest of the world is using semicircular rule.

And your point is taken: it was rather a theoretical question since you one is never flying exactely and constantly on 8500 ft. I share your opinion to contact ATC anyway to avoid troubles.

I thank you for your time and patience.
Now friends again ;-) ?

LR

[IO540]

I am wondering if there is some really basic confusion here.........

A "TMA" has no real meaning to actually flying in Europe - other than perhaps with regard to mandatory carriage of specified equipment e.g. a Mode S transponder may be mandatory within some TMA.

Controlled airspace (CAS) is controlled airspace! You have to keep out of CAS unless you have a clearance, and once in CAS then you are (generally) under a Radar Control Service and you fly as directed by ATC. The quad/semi etc etc etc rules do not apply. If ATC tell you to fly heading 340 at 14000ft on QNH of 1029 with your trousers down, that's what you do.

The above para applies regardless of VFR or IFR.

If flying "proper IFR" i.e. on a Eurocontrol flight plan, then you have an implicit whole-route clearance and the class of CAS (if any) becomes irrelevant once you are in the system. It's a seamless flight through all different airspace and you don't need to know anything about the airspace class. You fly as directed by ATC. The only time CAS is relevant is if you are joining CAS from an airfield which is outside CAS (in which case you must remain OCAS until cleared to enter it) or if, at the end, you cancel IFR and leave CAS (in which case you are on your own, have to get the VFR charts out, and cannot re-enter CAS unless you get another clearance to do so.

Then this controlled airspace pops up in front of me, from SFC to FL85

The above is what concerns me. In UK and probably all of Europe, the airspace above this "TMA" is going to be solid CAS (Class D or C, or Class A in the UK) and you can't go in there at all.

This isn't like in the USA, where you might have a piece of "upside down wedding cake" which is Class D or whatever (I have never really toured in the USA; only did my IR there) and above it is Class E which you can just zoom through under VFR... so long as you keep at/below 17999ft.

Europe has only a few cases where you can fly above some airport related CAS. Nearly always this piece of CAS joins onto a solid huge area of CAS covering the whole country, or something like that. In the UK, the only exception which comes to mind is Brize (EGVN) whose Class D tops out at 3500ft and above it is Class G, to quite a high level (FL100 or something like that, from memory). So legally (not wisely) you could fly above Brize at 3600ft, non-radio, VFR or IFR.

[BackPacker]

the fact that a lot of you think that FL85 isn't a legal VFR level.

Reading back the thread, I think the only one that might be confused a bit (or might be confusing the issue a bit) is Shunter, who suggested that you would either fly at FL80 or FL90. Which is true for IFR. For VFR, it would be FL85 or FL95, depending on magnetic track.

The rest of us either accepted that FL85 is a valid VFR level, or concentrated on the meat of the discussion.

In general, be careful with generalizations.:ok:

[LimaRomeo]

IO540: yes, I see what you mean.

But this was about a situation where you fly VFR at FL85 in uncontrolled airspace and you are NOT talking to any ATC of Info Frequency. And then that TMA zone comes up (SFC-FL85). This TMA is class D, the airspace above is G. You see the picture ...?

[chrisN]

Another question, reference UK, though it may be applicable elsewhere too.

If I fly in class G, not talking to anybody, below controlled airspace, whose base is at 3500 feet amsl, I think I can fly up to 3500’ - or at least 3499’. (Responses above suggest that even at exactly 3500 feet, I can use the lower class as the designation outside the UK but perhaps not within it.)

If, however, I am talking to air traffic control, they always say “not above 3400 feet”. I do comply with this, but why do they take the extra 99 feet away from me? Do they have to?

Chris N.

[IO540]

LR - I have edited and expanded my post ... do you see what I am getting at? There isn't normally Class G above the TMA.

[IO540]

If I fly in class G, not talking to anybody, below controlled airspace, whose base is at 3500 feet amsl, I think I can fly up to 3500’ - or at least 3499’. (Responses above suggest that even at exactly 3500 feet, I can use the lower class as the designation outside the UK but perhaps not within it.)

If, however, I am talking to air traffic control, they always say “not above 3400 feet”. I do comply with this, but why do they take the extra 99 feet away from me? Do they have to?

This kind of thing is highly debatable.

ICAO specifies that where there is a boundary between two airspace classes, the airspace class of the boundary itself is the less restrictive of the two classes.

This means that in the above example, 3500ft is Class G.

I don't believe that the UK has filed a difference to ICAO on this one.

But UK ATC (and CAA leaflets and general "advice") frequently differ from this, making all kinds of a meal of it.

In practice, you do as ATC says and fly at say 3400ft. It's sensible to do that anyway because 3501ft means you are busting CAS.

[BackPacker]

Responses above suggest that even at exactly 3500 feet, I can use the lower class as the designation outside the UK but perhaps not within it.

Looks like this even applies to the UK, *except* for the base of an airway.

If, however, I am talking to air traffic control, they always say “not above 3400 feet”. I do comply with this, but why do they take the extra 99 feet away from me? Do they have to?

Probably to save some R/T time. "99" is a rather long word to pronounce. But there's another issue too which is wake turbulence. If the base of CAS is at 3500 feet they'll typically vector the aircraft within it at 4000 feet or higher. Wake turbulence can extend up to 700 feet or so downwards so a little bit of extra margin can make a huge difference.

Related question: if you are directed to fly at a specific level, say 3000 feet, what is the accuracy that ATC expects you to fly that level at? +/-100, +/- 50?

[bookworm]

So if you're cruising at (exactly) FL85 and FL85 is defined as the boundary between two airspaces, you are technically in the airspace with the lowest restrictions. Ie. outside controlled airspace. But if you're at FL85 minus one hairs width, you're in controlled airspace without a clearance. Not good.

In circumstances where cruising levels are not mandated, the question is moot. Your level is a continuous variable, and you're either above or below the base. At the base has no real meaning.

However, where the law requires you to fly at, e.g. FL 45, 65, 85, or 105 etc., the question legitimately arises as to whether a flight at FL85 is considered to be inside or outside controlled airspace.

[dublinpilot]

LR - I have edited and expanded my post ... do you see what I am getting at? There isn't normally Class G above the TMA.

While this is quite true for TMA's, there are plenty of CTR's in France with class G above it, unless my memory is playing tricks on me!

If I fly in class G, not talking to anybody, below controlled airspace, whose base is at 3500 feet amsl, I think I can fly up to 3500’ - or at least 3499’. (Responses above suggest that even at exactly 3500 feet, I can use the lower class as the designation outside the UK but perhaps not within it.)

In doing that, remember that your altimeter reads the altitude at your wheels. (It should read ground level when your wheels are on the ground). So if you fly with it pointing at 3500ft, then all of your aircraft if above 3500ft, and inside controlled airspace ;)

Again...only theory....not much point in trying to do something like that!

dp

[LimaRomeo]

@ IO540: You say:

This isn't like in the USA, where you might have a piece of "upside down wedding cake" which is Class D or whatever and above it is Class E which you can just zoom through under VFR... so long as you keep at/below 17999ft.

Europe has only a few cases where you can fly above some airport related CAS. Nearly always this piece of CAS joins onto a solid huge area of CAS covering the whole country, or something like that.

-----

You are right: in my country (Belgium) this is the case and everything above 4500 ft is class C and controlled. But correct me if I'm wrong: in France there are a lot of places where the TMA of an airport goes up to FL85 and than it's class E again (or class G sometimes), but the LTA (legally class D) only starts at FL115. So you can fly over that specific airport's TMA at - say - FL95 without talking to anybody ...

LR

[bookworm]

Plenty of examples like that in Germany too.