UK Class C Airspace - 'freedom' to manoeuvre?
 

Hello,

I'm currently training to be a military pilot. We are coming up to the stage where controlled airspace is looming so I thought I'd better read up...


The following is confusing me:
The RAF Flight Information Handbook gives the following advice (Referencing UK AIP 1.4) (see attached screenshot)

Which says that IFR flights will be separated by ATC, but VFR flights will only be given a Traffic Service regarding other VFR flights.

In my head, if everyone was under control of ATC (e.g. you are to maintain this heading & FL) then there would be no need to offer anyone in CAS a traffic service, since ATC would be in control of everyone's movements anyway!


Does this mean that for VFR flights in CAS, they are given freedom to manoeuvre in some respects? (e.g. only bound by FL band / something similar)? I was under the impression it would be strictly 'maintain this track/FL until told otherwise'

Thanks for any advice that clears this up in my head!

There's very little class C in the UK anyhow, class D however you'll meet loads of, and so far as I know they're basically treated the same in this regard (I'm cautious with this statement because I really can't remember when I last flew in class C in the UK).

IFR clearances are on a route and an altitude or flight level. VFR clearances *may* be on a route, or may be "own navigation remain at least 2 miles clear of X" or variations thereon. VFR clearances are never at a specific altitude. They are either "not above" or "not below".

So, for example it could be along the lines of "clear transit controlled airspace through the XXXX overhead not above 4,000ft", or "clear transit controlled airspace, remaining south of town YYYYY, not below 2,000ft".

The assumption - which is a pretty sensible one when you analyse it is that you need to be able to modify your altitude in order to maintain VMC, and thus VFR, in British weather most days. Also so long as they know you're not going to get in the way of any IFR traffic, ATC have got enough to do without agreeing every small change you make with you. If you have any reason to go outside of the cleared limits (for example, because you want to climb over or descend under some cloud that's in your way and conflicts with your altitude range clearance) that's when you ask for a new clearance.

If your licences permit you to choose between IFR and VFR, there's a black art in deciding whether to ask for an IFR or VFR clearance through CAS. If it's a big lump of quiet airspace, I'd tend to ask for a VFR clearance that gives me flexibility and keeps everybody's workload down. If it's a busy confined bit of airspace, I'd tend to ask for IFR as it's much easier for the controller if they have that much greater control over my height and route.

I don't think you'll find it in CAP 413, but it's sometimes helpful to give ATC the choice, viz "request crossing clearance VFR, but can accept IFR if this is helpful to you". I use variations on that wording quite often, where it looks like I can make the controller's life easier, and the bandwidth is quiet enough that the lengthy transmission doesn't cause problems in itself.

Hope that helps.

I've always thought you were making a controllers life easier by being VFR, as with IFR there are greater spacing requirements between IFR and other traffic, and they would have to work harder to pass traffic information and provide spacing, whereas VFR there aren't the same required minimum lateral/altitude requirements??

If the controller has other traffic which is IFR - then they need to provide IFR separation for that aircraft from all other traffic, not just other IFR traffic. Therefore if the other traffic is VFR and thus able to vary altitude to maintain VMC - more, not less airspace is needed to do that. So, their job is easier in crowded airspace that includes IFR traffic if *everything* is IFR. That might for example include the CTA around a busy airport with arriving instrument traffic, even if conditions are perfect VMC.

If on the other hand everybody else is VFR and the airspace is fairly busy, then a single aircraft going IFR is a royal pain in the backside. Thus it's wise to do your best to understand the situation and try and do your best to make everybody else's life easy if you can.