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What is the point of an ATZ inside a Class D CTR?

Silvaire wrote:

Classes A through F is clear, adequate, and simple.
Well, obviously they are not adequate even in the US if you have to have a special rule for when special VFR is possible.

ESKC (Uppsala/Sundbro), Sweden

Based on what I understand I can’t see how Special VFR is much related to this discussion on airspace definitions. I could request Special VFR in Class D airspace, since in the US it is always associated with an airport and always extends to the ground. Also in the inner portions of Class C and B where they extend to the ground close to the associated airport, and are thereby analogous to Class D at a smaller airport. That doesn’t appear to be rocket science, but thanks for prompting me to relearn the Special VFR requirements. Maybe some day I’ll need to know them in the air.

Last Edited by Silvaire at 22 May 16:09

Silvaire wrote:

I can’t see how Special VFR is much related to this discussion on airspace definitions.

It is an example of where the airspace classification is not enough. You need additional means to define the airspace where Special VFR is possible.

ESKC (Uppsala/Sundbro), Sweden

Silvaire wrote:

in Class D airspace, since in the US it is always associated with an airport and always extends to the ground.

I appreciate that the US ‘does’ aviation better and with a lesser burden on the system to us over this side of the pond, but I don’t really see the issue with the CTR CTA etc thing. Any European pilot I have ever known knows the difference between these things and why its useful – it’s also ICAO. SO since we mostly all have ICAO licences we know that a CTR reaches the ground, however I wouldn’t have known that in the US the additional rule is that Class D always touches the ground and is associated with an airport. This isn’t the case in Europe which is why its useful to differentiate it.

Going to the original question, speaking only about the UK (since that is what I know more than any other country), all licenced airfields have an ATZ, they just aren’t shown on charts whenever the airfield also has its own CTR. As to the purpose of them, it has been mentioned already.

United Kingdom

Pirho wrote:

SO since we mostly all have ICAO licences we know that a CTR reaches the ground, however I wouldn’t have known that in the US the additional rule is that Class D always touches the ground and is associated with an airport.

Its not a rule, it’s a reality. You don’t need to know it, you look at the chart and see it. In relation to Special VFR in the US all you need to know is that controlled airspace is defined as Class E and up. Then in any controlled airspace associated with an airport that extends to the ground, you can request Special VFR. Very simple and logical, doesn’t require an additional non-lettered type of airspace.

What in Europe would actually require or encourage implementation of a parallel set of airspace definitions specific to airspace around airports? I thought maybe it might have something to do with an ICAO ATC staff qualification requirement, and avoiding paying controllers at quasi-controlled airports within Class G airspace, but I’m not sure that’s actually an issue – ATC controlled airports in Classes E and up don’t require radar or radar qualified ATC. Maybe I’m missing something in relation to limited ATC resources or uncontrolled airports. Regardless I’m happy not to have to deal with the parallel system in the US, just like transition altitudes for light aircraft, QFE and similar other complexities.

There is one common example of a similar extra airspace classification in the US – the ‘Mode C Veil’ around Class B airspace that I believe in the parallel system would be called a TMZ.

Last Edited by Silvaire at 23 May 00:03

There is a big difference between an ATZ and Class D / E airspace.

Class D and E guarantee IFR/IFR separation, and reasonable see-and-avoid for IFR traffic popping out of cloud, and hence have higher VMC weather minima than Class G. Special VFR clearances require ATC to treat the VFR the same as an IFR flight for separation purposes, and are more restrictive than Class G.

Biggin Hill

@Silvaire, I am sorry, but I really don’t see the big difference between having special rules for “airspace associated with an airport that extends to the ground” and having it for “control zones”. The only difference is that in the control zone case you introduce a name for that kind of airspace and chart that name. In both cases there is a rule (Special VFR is possible) which is orthogonal to the airspace classification.

ESKC (Uppsala/Sundbro), Sweden

Pirho explained the CTR/CTA quite well…they are nothing more than the names given to pieces of controlled airspace according to whether they extend to the ground or not….this is not just a European thing….Apart from FAA Instrument and Private writtens, I have passed Air Law exams in 6 other countries from Australia, SEA (Singapore & Malaysia), Middle East (UAE & Qatar) and UK and they all have that terminology…. In all cases the CTR or CTA has an alphabet class (A, B, C or D)…. not confusing and not difficult.

ATZs are an ICAO designation very loosely defined as a piece of airspace surrounding an airfield for the protection of the airfield traffic pattern…. The OP implied that an ATZ inside Class A, B, C or D airspace is redundant, and I think that is true…(except perhaps where the airspace reverts to Class G after hours)….it no longer appears on UK charts but it remains in the AIP for such airfields. As pointed out above, an ATZ is most useful at Licenced airfields in Class G. It allows for rules to require conformance with airfield defined traffic patterns….without the encumbrance of controlled airspace….

Another UK pragmatism….perhaps such cavalier pragmatism can be challenged in an EU court to bring those pesky Brits back into line Jan

Last Edited by AnthonyQ at 23 May 10:09
YPJT, United Arab Emirates

All that extra terminology continues to sound unnecessary and redundant to me, as does the need for ‘protection’ of an airport in uncontrolled airspace. Standard procedures and a single system of airspace definition are better to me.

I’m arriving in Germany now, so will sign off for a while. Interesting discussion to occupy one overnight at 35,000 ft.

Last Edited by Silvaire at 23 May 10:50

Silvaire wrote:

Standard procedures and a single system of airspace definition are better to me.

So you suggest that Special VFR should either be possible in all controlled airspace or not at all? Because otherwise you don’t have a single system of airspace definition whether you use the term “control zone” or not.

ESKC (Uppsala/Sundbro), Sweden
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