LeSving wrote:
Is this correct? You need clearance, but IMO only IFR flights must be able to follow ATC instructions.
Read ICAO Annex 2 para 3.6. 
Ok, think of it this way. If you must provide separation between VFR and IFR, both aircraft must comply with ATC instructions. For sure, the VFR may be give a “No further east of ******” but he has to comply to ensure separation against the IFR. Throw in another VFR flight and, under the Class C rules, how does ATC ensure that a VFR/VFR self-initiated avoidance doesn’t break the mandated minimum separation ‘bubble’ around the IFR?
It is practically done via a few methods. Some places have VFR routes/waypoints with enhanced separation bubbles (may as well make the VFR routes Class G), some tell the VFR to get out of the CAS (a favourite in non-radar Class C environments and not exactly efficient), whilst others manage the VFR traffic as if it is IFR. Whichever way you look at it, ATC instructions in Class C and above are mandatory. UK Class C below FL195 is rare and shaped like airways, hence the treat-everything-as-IFR criteria. Personally, I don’t get how a Class C CTR works; Class D is far more appropriate. 
PS. There was a push about 15-20 years ago to scrap ICAO airspace classifications, replacing with “Known”, “Intended” and “Unknown” traffic categories and associated airspaces. Quite some foresight considering where electronic conspicuity is going.
I don’t know whether FlightRadar 24 has an API from which you can pull flight route/altitude data, but a site like FlightAware or FR24 will have the data.
I am no apologist for UK airspace design but the CAS shapes are intended to accommodate stuff like missed approaches, for the lowest performance aircraft (e.g. an old A340) and not just straight-in approaches, which you would rightly guess don’t need that much CAS. A quick look at FR24 shows pretty steep descents from e.g. the DVR area into Gatwick.
The problem is that once you publish 2543 sids and stars for a given airport, you need to provide the CAS for them even if they are almost never flown as published…
Another factor is that ATC is extremely expensive. A senior NATS ATCO is on c. 100k, a fully costed radar desk is c. 1M/year, and the more CAS you have the more desks you need. So there is no incentive for NATS or anyone else to have more CAS than necessary, because then bits of it would be empty a lot, and would get used for transits by GA and then you need more ATC desks to provide the services to GA. And the UK has zero interest in providing a service to GA, beyond the ICAO-mandated FIS (called Basic Service in the UK) done by London Info.
In some ways, GA is its own worst enemy, by large sections of it demanding the right to be invisible, so understandably ATC services (which exist mainly for the airlines) are happy to govern the smallest amount of CAS even if it is weirdly shaped, because everything that goes on outside it is not for them to worry about, and if somebody busts it, well they have some software which alerts them, and the “perpetrator” gets pursued… Today I flew Cambridge-Shoreham, west of London, via this complete airspace mess, and you have to be on the ball looking at the GPS airspace map, while on the ball watching for the dickheads who are flying non-TXP (and thus invisible on my TCAS) and one of them was doing aerobatics at 2300ft (LTMA base 2500ft). I would have got a photo of him if I had a decent camera.
The key point here is that any controlled flight must adhere to the flight plan. Obviously for VFR, this means flight in VMC. Class C means that ATC offer a service to both IFR and VFR flights. If that’s not the case, then it’s not class C, but class A. End of story. When filing a VFR flight plan, you enter flight rules: VFR and cruising level: Alt or “VFR”.
If entering “VFR” as the cruising level, this means (as I remember) that the flight is an uncontrolled VFR flight (in class G typically). If you enter alt or flight level, then it is a controlled flight per def. So, you want a controlled flight and enter a level or alt. During flight, if weather prevents you from maintaining that alt, you can request another alt. This is the default scenario and what ICAO prescribes:
3.6.2.4 Weather deterioration below the VMC. When it becomes evident that flight in VMC in accordance with its current flight plan will not be practicable, a VFR flight operated as a controlled flight shall:
a) request an amended clearance enabling the aircraft to continue in VMC to destination or to an alternative aerodrome, or to leave the airspace within which an ATC clearance is required; or
b) if no clearance in accordance with a) can be obtained, continue to operate in VMC and notify the appropriate ATC unit of the action being taken either to leave the airspace concerned or to land at the nearest suitable aerodrome; or
c) if operated within a control zone, request authorization to operate as a special VFR flight; or
d) request clearance to operate in accordance with the instrument flight rules.
This is the service provided by the ATC in class C to VFR flight. The typical scenario is you have to go lower than your original flight plan. If weather continues to deteriorate, you will eventually end up in class G where ATC can no longer offer a controlled flight. Another typical scenario is weather improves, and you would like to go higher, up into class C. You certainly would like to do that when operating over water. You then request clearance (shortened flight plan) and get a clearance to fly at a particular alt through the TMA typically. If you no longer can adhere to that clearance (due to weather or whatever) then it’s back to point a) again.
Class C is a service to both IFR and VFR flights, and ICAO describes it straight forward IMO, and in exactly the same way I am used to.
The key point here is that any controlled flight must adhere to the flight plan.
Close but not quite. Any controlled flight must adhere to the clearance. If you can’t comply with the clearance then you must negotiate a new clearance.
Generally, I appreciate the lobbying done by FASVIG. They try to gently push the mountain (the CAA) in the good direction. One cannot hope for more.
Despite all this stuff about Class C considered-as-A-but-not-really, did anyone ever got cleared through this Holyhead Class C, on a simple VFR FPL UK-to-Ireland ?
I’m interested for a future trip.
Thanks
Dave_Phillips wrote:
Personally, I don’t get how a Class C CTR works
Visit Sweden. Every CTR has class C. It works beautifully. Honestly, I don’t see what the problem is.
LeSving wrote:
You need clearance, but IMO only IFR flights must be able to follow ATC instructions. This is more of an equipment issue. A VFR flight isn’t necessarily equipped to follow ATC instructions, but an IFR flight has to be for separation to work.With all respect, you’re opinion isn’t relevant. A VFR flight has to follow “ATC instruction” — that is, a clearance — but can demand a different clearance if the one offered is impossible or unsafe to follow. In the worst case if ATC can’t offer an alternate clearace, the pilot can exercise emergency authority.
(The term “Follow ATC instructions” is really a US thing where in class C and D airspace VFR don’t need clearances but have to “follow ATC instructions”. Actually, any “ATC instruction” which tells you where or how to fly is a clearance. There are other “ATC instructions” such as transponder settings, report request etc.)
LeSving wrote:
How class B is supposed to work is a mystery to me.
Class B works exactly like class C, except that clearances given to VFR flights will also serve to separate them from other VFR flights.
There is an important distinction between class C and D that matters to ATC and commercial IFR traffic. In class D, IFR traffic below FL100 is speed limited to 250 knots. That restriction can’t be lifted by ATC. In class C there is no such restriction. (Class C TMAs frequently have speed limits as part of local rules, but such speed limits can be lifted by ATC.)
Maybe you have to re-think the format an ATC clearance can have, especially in airspace C (and presumably B, never been in or even seen one).
Here in Germany, upon entering class C you will get a direction or heading basically the same an IFR flight would get e.g. inbound a specified navaid.
But to accommodate your need to stay VMC, you would get a “level band clearance” like “Cleared to enter Class C inbound XYZ VOR, between FL 105 and FL135”. With this clearance, you are free to climb and descend in your block as needed to stay clear of clouds without having to ask each time.
Further negotiation and a new clearance would only be needed if the assigned level band is not sufficient or you need turns to avoid.
From my experience, this works well both in general class C at FL100+, and in lowered class C around larger airports.
