Airspace Classifications

[BroomstickPilot]

Ladies and Gentlemen,

Please forgive me for intruding on your forum. I am a PPL currently doing groundschool studies in preparation for CPL examinations.

I have never understood why there are as many as seven different classes of airspace. All the textbooks tell us what the classifications of airspace are, but none explain exactly why each of these classifications came into existance or what particular purpose it serves. For example, if the requirements of 'Class B' airspace are so little short of those of 'Class A', why not make it all 'Class A'?

(As a PPL you concern yourself only with those classifications that concern you, but as a CPL you need to have a very much better understanding).

Are there any ATCO's textbooks or NATS publications that would be useful sources of reference in this matter, bearing in mind that what I want to know is not so much the 'what' but rather the 'why' of this subject?

Very Best Regards,

BroomstickPilot

[1261]

You can find the "what" at ENR 1-4-1 in the UK Air Pilot (online version at www.ais.org.uk).

As for the "why", if you find an answer, let us all know!

Most terminal airspace in the UK is Class A; in the Netherlands it's Class B; in Ireland Class C. Even in the UK there are anomalies - the Scottish TMA is Class D (with areas of Class E). Much of this will be historical, but often there's no apparent reason for a particular classification - I could only suggest that you speak to DAP.

It's important (at least I think it is) to understand that in the UK traffic is often "overcontrolled"; that's to say [for example] we treat VFR traffic in exactly the same way as the Irish do - we're in Class D, they're in Class C! The style of control you receive and service you get are often not exactly what you might expect.

[Whipping Boy's SATCO]

Don't worry, I am led to believe that in 2010 we will reduce to 3 classifications (N, K & U) and in 2015 two (N & U). I have lifted the below from a Eurocontrol Briefing note:


Current proposals envisage moving to just three categories:
N – where the position and intentions of all
traffic is known to ATC

K – where at least the position of all traffic is
known to ATC, who may also know the
traffic’s intentions

U – where not all traffic is known to ATC
In some areas class N and K airspace would extend to lower levels to accommodate terminal
operations.

In the meantime, the AIP (as already suggested) is a good start.

PS. Please don't shoot the messenger:confused: :confused:

[GroundBound]

Well, you'll probably find the reason is historical and possibly a political compromise at ICAO. Primarily it should be linked to density of traffic, and hence to safety.

As a PPL you concern yourself only with those classifications that concern you, but as a CPL you need to have a very much better understanding

On the contrary, I would think that the classification is more important to a PPL holder , than to a CPL holder, since with a CPL/IR you will eventually have the qualifications to fly anywhere, however for those who don't (PPLs, currently like yourself) the airspace classification is vital, as it defines where they can/can't fly.

"A" airspace is for the big boys - professionals in suitably equipped aeroplanes who can fly to high standards in any weather, and under positive ATC to stop them bumping into one another - for safety (of the crews and the paying public)! This of course means that VFR flights are kept out (on safety grounds). It corresponds to what used to be called "rule 22" airspace in the UK. However, many people don't like this, especially the USA GA community.

So we have "B" which is equivalent to "A" but allows VFR flights. It might be considered potentially less safe since the VFR pilot does not fly to the same exacting standards as CPL/ATPL, and the aircraft may be less well equipped. Nevertheless, positive ATC should hopefully ensure this does not happen :). It does make it more demanding on ATC though, as they can't tell whether a clearance would force a VFR pilot to become IMC.

As traffic density gets less, then we have "C" where only IFR flights are positively separated from everyone, and VFR flights are warned of other VFR, but have to keep themselves apart. Giving greater flexibility to the VFR and GA community.

And so on down to "D" where IFR flights are positively separated only from each other and warned of VFR flights, and the VFR have to keep themselves apart from everyone else.

"E" is less restrictive on ATC and equipment carriage, "F" is the old advisory route idea once used in the UK, and "G" is Indian territory.

The definitions remain constant but different countries have decided to attribute their airspace in different ways. The decision should be based (logically) on density and safety . Since somebody mentioned Ireland, I notice that Sligo has a class C zone around it for a PPR airfield - it doesn't have scheduled traffic and I doubt it has more than a handful of movements per day (apologies if I am wrong). Does this seem logical? I doubt it, but it was the Irish Aviation Authority's decision. One man's density is another man's day off! :)

Here in Belgium, most of the TMAs are "B" from 1500/2000/2500' upwards. However, I doubt I would get an ATC clearance across the Brussels TMA at low level for a VFR flight! So they are more or less "A" in practice.

As an answer to your question, its not the classification that's wrong but, as 1261 says, the attribution of airspace according to different criteria, and the inconsistent application of rules within the designated airspace.

Confused even more? :) :)

[LostThePicture]

The ATC bible, CAP493, has the definitive answer from an Air Traffic point of view.

http://www.caa.co.uk/publications/publicationdetails.asp?id=222

and then click on the link. You can find airspace classifications in Section 1, Chapter 2. :uhoh: Be warned it's pretty dry reading though. :bored:

There's currently no class C airspace in the UK, and class B covers more-or-less all airspace above FL245 (not many PPL's in there then :D )

If you're in class A or B airspace, then with any luck a controller somewhere knows that you are there and who you are. These are "known traffic environments", and hopefully the controller will separate you from other known traffic. With any luck.

Class D airspace is also a know traffic environment, but the controller will provide no separation against VFR aircraft. However, to prevent nasty surprises s/he should provide traffic information if a confliction looks likely.

Class E airspace only requires IFR traffic to obtain a clearance before entry. VFR can do what they like. As 1261 says, parts of the Scottish TMA have this classification. Sounds a bit dicey to me though, surely it only takes one unknown VFR aircraft to ruin your day as a controller? :{

Class F and G - basically bandit country. Keep a good look out.

[callyoushortly]

LostThePicture

It most certainly does only take one aircraft not quite where you'd like it in class E airspace to liven one's day up!
It's quite amazing therefore, how many pilots working in/out of the Scottish TMA don't realise the fact that there can be unknown traffic in the area.... and quite legitmately there too.

It does make me wonder though......
Why pilots want to fly faster than '250kts below FL100' in a potentially unknown traffic environment??
How is it that Scottish can offer inbound aircraft 'no speed restriction' or worse... 'keep 310kts up please' when it's not their responsibility to then control the aircraft not adhering to the above rule??

[bluskis]

Rules of entry of the different air spaces have not been mentioned but also exist.

VFR is allowed in some A space, although it is called SVFR and requires a clearance.

In D space as far as I am aware VFR traffic can not just bumble into it, but must get clearance to do so.

Even Brussels will give VFR traffic clearance to enter if you are going to land there, but you need a bag full of money for the landing fee.

The above is not extensive.

[Scott Voigt]

I wouldn't say that class A is for the big boys only. In the US all it means is that you have to be IFR. We have a LOT of folks who don't come close to the big boy catagory who are up there. Then again, our VFR only folks can fly just about anywhere up to 17,500 with no problem at all <G>....

regards

Scott

[Spitoon]

bluskis, I think you may be oversimplifying the situation to say that you can fly VFR in Class A but it's just got another name.

[GroundBound]

I agree class A is not just for the big boys ..... but you need an IR and an aero(air)plane suitablly equipped with the all the right gear. Not so prevalent amongst PPL holders, as it takes a bucket of money to get it and a nice constant flow of more money (and time) to keep it (at least over here, it does :) ).

But that's why we have class B isn't it? ;)

[BroomstickPilot]

May I please express my appreciation for the promptness and the detail with which you have all responded to my post. Clearly, quite a lot of time and thought has gone into preparing replies to assist me. My thanks to one and all.

I had been really worried in case there was some arcane, underlying logic to the classification of airspace that I, in my ignorance and simplicity had failed to perceive.

Now, however, I realise that in the classification of airspace there is no logic, or rather that a species of retro-logic is involved probably of the kind that must have inspired such great minds as Salvador Dali or Hironimus Bosch.

For all we know, somewhere in a basement in perhaps Brussels or Strasberg an unsung genius languishes in a padded cell.

Best wishes, Guys.

[bookworm]

Just before you write off airspace classification as an aberration, consider the situation before the airspace classification scheme was introduced.

I used to fly VFR from the UK to Germany, passing through the airspace of 5 different states. Each had different rules for their version for controlled airspace, special rules airspace, instrument/visual airspace or whatever. It was a nightmare.

Now, although the structure is still different in different states, you do at least know what separation service is being provided to you and what clearance you might require from the alphabetical classification. I know that I cannot get a VFR clearance in class A, or that if I'm IFR in class E there might be uncontrolled VFR around.

So classes A to G may provide some puzzles for student pilots, but it certainly makes international operational flying easier.