What is CAS (controlled airspace)?

[achimha]

I see a lot of UK people use the term CAS for airspace where you need permission to enter. So airspace A-D would be CAS while E-G would not. In other parts of the world, controlled airspace means airspace where ATC services are available, i.e. A-E with only F and G being uncontrolled airspace.

Doesn't most VFR flying in the UK take place in airspace E which is CAS?

Wikipedia says the following (http://en.wikipedia.org/wiki/Airspace_classes):

Classes A–E are referred to as controlled airspace. Classes F and G are uncontrolled airspace.

Maybe I got something wrong, what's behind the term CAS?

[Flamin_Squirrel]

The Wikipedia article is still true for UK airspace; A-E is controlled, with most VFR taking place in class G. ATC is often available in class G also.

[Jan Olieslagers]

There is indeed a difference between "controlled" and "ATC service available".
"Controlled" means that there is someone available on the radio, and that this person has authority to tell pilots what to do - this person is "in control".
Uncontrolled airspace may still have radio service available, either an airfield information service or a regional FIS, but this is not a controller, for lack of authority.

But I must admit I am unclear about the practical effect of classes E and F, as they do not exist where I live. I understand that in French FIR, most airways are class E.

[achimha]

OK, now I understand, I was not aware that airspace G has a large vertical extent in the UK. That's different from most countries I've visited so far. In USA/Germany/France/Switzerland/Austria/Czech Republic/etc. most of VFR takes place in airspace E. In Germany, G will never be found above 2500ft AGL.

Germany is a bit odd because it makes use of airspace F. This is because IFR is forbidden in airspace G and in order to do an IFR departure/arrival for a small aerodrome without a control zone (which requires dedicated ATC staff), they introduced F which is like G but with IFR allowed, higher minima and only one IFR traffic at a time. One has to know that the German minima for G are quite suicidal (1.5km flight visibility, don't penetrate clouds). Apparently EASA want to take F away from Germany (it's supposed to be a temporary airspace according to ICAO) so there is a lot of discussion about that right now.

[BackPacker]

Class E is a strange go-between. It is controlled for IFR traffic (IFR ATC services and clearances are provided as usual) but it is uncontrolled (in the sense that you do not need permission to enter) for VFR traffic.

So whether Class E is controlled depends on the perspective of the user.

At the end of the day, what you need to understand is that "controlled" comes in a number of shades. Controlled doesn't automatically mean that all aircraft are on an ATC leash and can only do as ATC says, and uncontrolled doesn't automatically mean that it's free for all, do as you please with no help from ATC at all. That's why there's a distinction in seven classes (A-G), and not just a single distinction in CAS/OCAS.

[peterh337]

A-E is controlled airspace for IFR.
A-D is controlled airspace for VFR.

ATC is not capable of issuing clearances in uncontrolled airspace - end of story (except inside an ATZ ;) ). They can provide a service and indeed the basic ICAO obligation is an FIS in all airspace.

France (http://flyinfrance.free.fr/), generally, FL065-FL115 is Class E. FL120-FL195 is Class D. FL200+ is Class A. An excellent system but one which cannot be run by privatised ATC :)

The lines on the French 1:1M SIA chart which look like "airways" are mostly just preferred VOR-VOR routes, with MEAs mostly FL065 and the usable levels going up to the top of the lower airspace at FL195. You can file Eurocontrol routings in that airspace seamlessly. Above FL200 you have a largely different set of routings (e.g. you can overfly Paris) but it works the same way.

"Airways" is a really meaningless term - it's a "UK PPL flying school" term for "a place you are not ever meant to go and if you do you get an interview without tea and biscuits" :)

[stickandrudderman]

Peter, that "France" link is excellent, thanks for posting it.

[soaringhigh650]

"Airways" is a really meaningless term


Not at all. An airway (http://en.wikipedia.org/wiki/Airway_(aviation)) is an ATS route. They have been traditionally laid out based on ground-based navigational aids, but GPS is here to improve routes going forward.

[Jim59]

ATC is not capable of issuing clearances in uncontrolled airspace - end of story (except inside an ATZ http://images.ibsrv.net/ibsrv/res/src:www.pprune.org/get/images/smilies/wink2.gif ). They can provide a service and indeed the basic ICAO obligation is an FIS in all airspace.




End of story - except (splitting hairs) it is not an accurate statement.

If you are in Class G airspace and want to enter controlled airspace (or an ATZ) you will need to be given the clearance before you enter the controlled airspace - therefore ATC (or an agent acting on their behalf such as a FISO) will issue the clearance and pass it to you while you are in uncontrolled airspace.

ATC can also give clearances to fly through some types of TRA which are in class G airspace (police emergencies for example).

What they cannot do is refuse you access to uncontrolled airspace. I.e., you don't need a clearance to fly in uncontrolled airspace.

[peterh337]

Not at all. An airway (http://en.wikipedia.org/wiki/Airway_%28aviation%29) is an ATS route. They have been traditionally laid out based on ground-based navigational aidsYou are right for the USA. They have a very uniform system of VOR-VOR routes, all properly worked out with the MEAs based on the highest of MORA, MRA, etc.

You can fly all over the USA with just VOR and ILS receivers. That's how I did my IR there :ok:

Europe works differently. The ATS route MEAs don't seem to be based on anything particular (base of CAS perhaps) and the routes themselves seem to be based on even less :) Usually they are routed around airspace which the military grabbed first (but rarely use) :)

[bookworm]

Maybe I got something wrong, what's behind the term CAS?

Controlled airspace used to be defined as airspace in which an air traffic control service is provided to (and mandatory for) all IFR flights. Since the alphabetical classification, it is now, by definition, classes A to E (which are the classes that meet the former definition).

To refer to class E airspace as "uncontrolled" is technically incorrect, and may cause confusion in states like the US or Germany where there's a lot of class E at lower levels. The UK has very little class E, hence we've grown quite lax in our terminology.

[englishal]

Class E airspace is great if you ask me, because it means that all IFR traffic is known about. This is good because it stops people just launching off into infinity and beyond with their iPod on and radio off. Some will disagree with me on here, but I am not too keen on this sort of IFR (in IMC) type of flying.

In parts of the UK you can find Class G up to FL195 so if you want to you can fly VFR up there.

If I were given a map and a pen and was told to redesign the UK airspace I'd stop all Class A (which I'd rename as Class B ;) ) at 10,000 AGL and then have class D above that up to say FL285. This would then mean that VFR traffic could fly up there with the appropriate clearance....

[bookworm]

Class E airspace is great if you ask me, because it means that all IFR traffic is known about.

Class E is a waste of resource. Traffic that needs separation from other aircraft needs it more in VMC than in IMC, because the risk of collision is greater in VMC (where there is some possibility of avoiding a collision visually, but much higher traffic density -- the latter factor wins). Mandating participation in an air traffic control service in IMC (but not in VMC) sounds very comforting, but the comfort is illusory.

[Hodja]

You are right for the USA. They have a very uniform system of VOR-VOR routes

For Europe, how does filing DIRECT work? (ie. between waypoints not directly connected via any airway) Is this a a big no-no with Eurocontrol?

Or do you tend to get a lot of DIRECTs anyway when finally airborne? (prompted or unprompted)

[Hodja]

A-D is controlled airspace for VFR.


B-D :)
.............

[achimha]

For Europe, how does filing DIRECT work? (ie. between waypoints not directly connected via any airway) Is this a a big no-no with Eurocontrol?

Each FIR has a maximum DIRECT leg distance, this can range from a rather large value (150NM) to a rather small one (0NM for Switzerland). Once you meet that FIR criterion, Eurocontrol will accept your flightplan. However, they will not check the MSA for you. In reality, it is hardly possible to create an IFR flightplan in Europe without computer assistance. None of the tools I know try to optimize the route using DIRECTs though so that's always a good exercise.

Or do you tend to get a lot of DIRECTs anyway when finally airborne? (prompted or unprompted)

Yes, depending on the country. The other day I flew from Berlin to Stuttgart and once airborne I got a direct to the VOR that was the IAF. Difficult to tune with your VOR receiver at 300NM though :) In some countries, you almost always fly airways, in others you almost never fly airways as low level traffic (e.g. Germany). The IFR low level network is pretty empty in Europe. The whole Eurocontrol nonsense is mostly a departure/arrival coordination thing.

[peterh337]

Once you meet that FIR criterion, Eurocontrol will accept your flightplan.

You need to meet a lot more criteria however.

However, they will not check the MSA for you. In reality, it is hardly possible to create an IFR flightplan in Europe without computer assistance. None of the tools I know try to optimize the route using DIRECTs though so that's always a good exercise.

FlightPlanPro should offer DCTs, where they are not prohibited for that airspace.

[Hodja]

Ok, interesting.


In reality, it is hardly possible to create an IFR flightplan in Europe without computer assistance.

Now, why exactly is that? Peter mentions this too on his excellent website.

Are there simply too many obscure restrictions on the individual airways (and not necessarily printed on the charts), or is the volume of navaids & airways just too big & complex to easily pick out the optimal route in terms of distance?

Won't most of the "naive" routings get accepted as long at it fulfills MEA, or does it have to mimic a "preferred route" structure similar to the (optional) ones in the US?

[achimha]

Won't most of the "naive" routings get accepted as long at it fulfills MEA, or does it have to mimic a "preferred route" structure similar to the (optional) ones in the US?

There are thousands of restrictions and they change on a daily basis, impossible to depict on a chart. It's all part a database called EAD which is several thousand pages long.

However, that is not a real issue because a computer can easily handle that complexity. Eurocontrol offer a service where you submit a routing and it will tell you whether it's acceptable or not. The programs then usually perform a few dozen iterations to come up with the shortest routing possible. This routing is rarely flown! It only serves in case of lost COM and for fuel planning purposes. In my experience, enroute ATC don't even know about your filed routing.

The Eurocontrol system is weird and nonsense for GA but it's hardly an issue with today's IT and wireless internet. Applications like FlightPlanPro and RocketRoute.com make it rather easy.

[peterh337]

Now, why exactly is that?Eurocontrol would say they are only implementing each country's routing requirements. So this is where the trouble starts. Most N European countries, in their endless quest for gold plating and job creation / job protection issue a totally bizzare set of routing restrictions for their airspace.

These are in turn the result of haggling between mostly the military who like to hang onto various chunks of airspace, knowing that if they let go of it they will lose it for good, and the national CAA.

Eurocontrol's software boffins (to whom "usability" is a totally alien concept) then implement that in their validation software.

However it is obvious that Eurocontrol could have easily provided a route generation facility on their website. They have always had this in-house, and announced plans as early as 2005 to open this up.

What happened then is not public but my info from the inside of Eurocontrol is that the expensive bizjet flight support services (Jeppesen, etc) made a massive fuss. Their business hangs on the "black art" of IFR route development and flight plan filing, and the rest of the stuff they do for their money (overflight permits, etc) can be done quite easily by others. What you do get is an integrated service but take out the IFR route planning and the black art bit is now gone.

So Eurocontrol backtracked on their plans. At a 2008 conference (which I was at) this was put to a Mr Hendrix (a senior ex-ATCO working in there, who was heading the event) and he gave a pompous and totally daft answer that it would require too much computer power :)

Later, in 2008, a chap called Christof Edel developed a program called Autoplan which would do a maze routing through the airway database, present it to the Eurocontrol validation website, and iteratively modify it until the error messages all went away. It worked brilliantly. Eurocontrol tried to block it by changing their validation portal, changing it to HTTPS and a few days later changing it to a Flash movie site, and Christof who also had other priorities then gave up the chase.

But the incestuous relationship between Eurocontrol and whoever stopped them offering routing was blown for good. Around 2009, other software sprung up which used a "more approved" (i.e. paid for) validation facility. Flightplanpro is the main one, whose functionality is also available via the Rocketroute website. Eurocontrol also then started offering a "route suggest" facility; initially this was crap, with overheads of 100% in some cases, but they kept improving it and today it is pretty good and works most of the time. This feature is accessible via EuroFPL, via Rocketroute, via Flightplanpro, and I guess via other services. I haven't used Homebriefing.com for a long time but I guess they now offer it too.

So, today you can get a valid route which is pretty efficient (5-15% overhead over GC is normal in Europe in the lower airspace system) about 95% of the time. The other 5% you have to manually hack it with some DCTs, but this is getting rarer all the time. I use Flightplanpro for everything and it is at least a year since it has not been able to do a workable route.

All in all, things are much better than they were say 5 years ago. IFR flight planning is now a piece of cake, usually.

The funniest thing is that ATC do not actually operate most of the routing rules which their own country has concocted. They treat controlled airspace as their tactical playground and once you are airborne they couldn't care less about standard routes, semicircular levels, etc. In reality you sit there, FL150 or whatever, on autopilot, and just keep asking for DCT shortcuts the whole way :) The original standard route massive job creation scheme is almost totally wasted.

Some countries are better. France for example seems to have very few rules, and you can file routes all over France, in their FL065-FL195 Class E/D airspace, and most of the routes are the same in both directions. This is the closest to the US model.

[Rod1]

“If I were given a map and a pen and was told to redesign the UK airspace I'd stop all Class A (which I'd rename as Class B ) at 10,000 AGL and then have class D above that up to say FL285. This would then mean that VFR traffic could fly up there with the appropriate clearance....”

That would make you very unpopular with the BGA!

Rod1

[Hodja]

Ok, so I gather there's been some friction between Eurocontrol and the european IFR GA crowd. ;)

I guess Eurocontrol was primarily designed to manage the massive flow of airliners operating in, out & across the central european airport cluster of London, Paris, Amsterdam, Frankfurt, Brussels etc. Everyone else just got stuck with arcane bureaucracy.


What happened then is not public but my info from the inside of Eurocontrol is that the expensive bizjet flight support services (Jeppesen, etc) made a massive fuss

Well, fortunately the Internet and the progressive culture of independent 3rd party solutions happened. The Jeppesen monopoly seems to be steadily eroding.

Both US, Europe & AU/NZ have an abundance of quality tools coming online. Also places like the US & AU always had 1st rate charts from the national providers (FAA NACO, Airservices Australia)

Jeppesen still has a stronghold in the remaining territories like Asia, Africa, South America (I think) & oceanic sectors, as well as worldwide operators who needs consistency & comprehensive coverage.

So, today you can get a valid route which is pretty efficient (5-15% overhead over GC is normal in Europe in the lower airspace system) about 95% of the time.

5-15% actually sounds perfectly acceptable.

In reality you sit there, FL150 or whatever, on autopilot, and just keep asking for DCT shortcuts the whole way

Sounds exactly the same as US & the gentler parts of Asia...:)

[soaringhigh650]

That would make you very unpopular with the BGA!

How so? Moving from A to B will permit VFR flight?

I think the best airspace layout is what we have over here (http://www.dicksmithflyer.com.au/artman/uploads/airspace6_003.jpg).

The UK just looks a mess to me (http://www.pprune.org/atc-issues/454180-olympic-airspace-validation-3.html), second to Italy.