View Full Version : Fir, Uir; Cta, Uta

17th Oct 2003, 15:55
Most of my work is in US domestic airspace. The other day I'm in ICAO airspace. Long time to read the charts. I'm doing all the right things with waypoint ETAs, ATAs, etc on my Master Flight Doc and so forth.

FIR = Flight Information Region
UIR = Upper? [flight] Information Region?
CTA = Control [T----?] Area?
UTA = Upper [control?] Area?

And-- looking at this as a Pilot in Command -- what changes as to my obligations re air traffic control as I leave and enter FIRs, UIRs, CTAs and UTAs?

I'm aware that a US center (e.g. "Los Angeles Center" is also an FIR. But what part of it, if any, is a UIR?

All rather mysterious. (Obviously I read my (*$& flight plan and fly it within M01 and 5% KTAS, speak up if I'm to miss a waypoint by more than 3 minutes, etc.

But what the dev#l are those letters for? And does anything change when you fly from one to another?

Slightly embarrassed not to know.

Genghis the Engineer
17th Oct 2003, 16:36
I'm afraid that I don't recognise all of them either, but I can help on two.

FIR = Flight Information Region. Here in the British Isles, we have three FIR, London, Shannon and Scottish, within the FIR you have a common frequency you can talk to (London Information for example) for a Flight Information Service (no direct equivalent to this I think in FAA-speak, it's like "Traffic Information" but without radar reports).

I don't think that we would term LA Centre as an FIR, we'd term it a LARS service provider (Lower Airspace Regional Service), just as I would "London Information", which is the frequency on which I get my FIS within London FIR.

CTA = ConTrol Area. This is class D airspace controlled usually by a major airport. For example just south of where I'm sitting at the moment is "Solent CTA" which is jointly controlled by Southampton and Bournemouth International Airports and runs from a defined altitude to a defined flight-level, surrounding the class-D that is over each airport and runs down to the surface (and is called a CTR, or "ConTRol Zone" - not an obvious abbreviation).

(Incidentally in the UK we also refer to a TMA, or "Terminal Manoeuvering Area" which is basically a bigger CTA and class A, not D. For example if you fly into LHR, you'll pass through LTMA - London Terminal Manoeuvering Area)

Not the foggiest on the other two, but I look forward to hopefully learning something from somebody who has.


17th Oct 2003, 16:51
I think that in the UK the UIR is FL245 and up.

For more try the ATC forum.

17th Oct 2003, 22:51
I agree with xyz - the ATC forum is probably where you'll get the best answers.

FIR: can't think of much to add to Genghis' reply. Except that I thought LARS was a Lower Airspace Radar Service, and refers only to a Radar Information Service or Radar Advisory Service. I wouldn't refer to London Information as a LARS provider. But I may be wrong on this, and it's all very UK-specific anyway.

The UIR in the UK is FL245 and above, as xyz says. Don't know that you'd notice any difference, except maybe being handed to another controller, but since I've never flown anything that goes that high I don't really know!

CTA is a ConTrol Area. Every controlled airport in controlled airspace (which basically means most reasonable sized airports) will have a CTR, which stands for Control Zone. A CTR always goes from the surface up to a specified altitude or level. Above a CTR may be a CTA, which typically is larger, laterally, than the CTR, and extends from one altitude or level to another. It basically corresponds to all except for the lowest tier of the "inverted wedding cake" type of airspace which is common in the USA.

Never heard of a UTA. Anyone else?


17th Oct 2003, 23:10
Isn't it an Upper Terminal Area such as the Hebrides UTA (HUTA) into which the transatlantic traffic on the northerly tracks pass as they enter/leave domestic airspace - a bit like the Shannon Oceanic Transition Area (SOTA)? I'm a short haul merchant now, but I seem to remember this from a previous existence some time ago.


Genghis the Engineer
17th Oct 2003, 23:32
I stand corrected, Lower Airspace Radar Service it is. Except of-course, that many of us usually get from our LARS controller a "Flight Information Service" which is non-radar!

I've just found UTA in my (slightly out of date) RAF North Atlantic en-route supplement. It defines it as "Upper ConTrol Area". The book is not all that clear, but seems to define three UTA, which are...

Hebrides UTA
Scottish MRSA (Mandatory Radar Service Area)
London Mil MRSA

It seems to start at FL245 and keep going up except for a few high level pieces of otherwise controlled airspace.


18th Oct 2003, 02:05
Minor point: A Control Area has nothing to do with an aerodrome. A CTA can be established anywhere where a need is determined.

I've never understood why, if Controlled Airspace is 'CTA', a Control Zone isn't 'CTZ'. A hang over from 40 years ago when it might have been a Control Region?

Meanwhile: UIR: Upper airspace Information Region, as opposed to a Flight Information Region for the levels below it. Just a means of subdividing the workload/assigning responsibility etc

In it can be areas of CTA of varying types & OCTA.

18th Oct 2003, 21:17
FIRs and UIRs are, in effect, administrative boundaries. Smaller states will have only one FIR, larger states break their airspace up into several.

FIRs do not necessarily correspond to the extent of airspace controlled by an ATCC (center). The US chooses to break its airspace up by center for IFR purposes, but it's not quite the same as an FIR.

What changes as you move from one to another? For an IFR flight in controlled airspace, not much. You might anticipate a frequency change, particularly at an international boundary, but there are plenty of frequency changes between sectors within an FIR anyway.

UIRs are just FIRs at a higher level, and the tracts of airspace are often bigger, with one UIR overlying several FIRs.

A CTA is a control area, as already stated. The continental US is one big CTA from 1200 agl up to FL180, with local exceptions of course. It used to be called the "continental control area" I think, before alphabet soup days. Being a CTA doesn't make it a particular class of airspace, except that you know that it must be class A to E and that IFR flights will receive a control service.

19th Oct 2003, 02:58
From the UK Mats Part 1 (Cap493):

Division of Airspace
The United Kingdom airspace is divided into two flight information regions. Within each region the airspace below flight level 245 is known as a lower flight information region (FIR) and that at and above as an upper flight information region (UIR).

---basically in the UK, the airspace above FL245 is Class B, therefore everyone has to have a clearance to enter and thus is known traffic. In many parts of Europe the division is FL195. Inside FIR's, Airways and Advisory routes are established, and in the UIR's these are then Upper Air Routes. An Airway is 10nm wide, extending 5nm either side of the centreline, often (but getting rarer) outside these limits you are outside CAS. In UIR's you are always inside CAS, and if you get over 5nm from the centreline of an Upper Air Route, are only considered to be 'off route' whereby co-ordination with the Military is normally necessary. In the UK there are set times where all a/c will be given on-route status even if off route, normally during the night and at weekends. Not every Airway has an associated Upper Air Route and vice versa.

Classification of Airspace
The classification of the airspace within a flight information region determines the flight rules which apply and the minimum services which are to be provided.

---the classes are A-G, A-D being controlled classes, E/F are advisory areas, and G is totally uncontrolled.

CTA-Control Area
CTR-Control Zone

---CTRs are control zones within defined limits of an aerodrome, and these can be surrounded by CTAs (Control Areas) to link to the Airway network and give added protection if necessary.

In the abbrieviation list there is no mention of UTA.

Hope this helps - 5mb. :ok: