A CAS question

[jack-oh]

This is a bit of a beard scratcher but hopefully someone will be able to help.
When controlled airspace is being designed (this apllies to CTAs mainly) does the base level of the CTA have a direct link to the minimum vectoring altitude permisable. For instance in order to ensure that separation exists between ac flying outside of CAS and those within, is 1000ft subtracted from the minimum vectoring altitude. ie. MVA 2500ft, base of the CTA 1500ft. I appreciate that the CTA and CTZ will eventualy look like an upside down weding, cake as the ac decsends towards the runway, but at range is this process taken into acount. I note with intrest that the new Prestwick CTA has a base level of 1500ft in places but the MVA is 1600ft as you make an approach to the Easterly runway. This could concievably only provide 101ft of separation between aircraft. Again I understand the concept of Im in, your out, and never the twain shall meet. But it seems a bit dodgy to me.

Regards

Jack-oh

[M609]

In Norway and Sweden 500ft from MVA to CTA bottom is normal. MVA 2000, CTA from 1500 and up.
(if terrain is mointainous/high, 1000, 1500 and 2000ft is often used, to allow visual approach to be conducted in CAS at all times)

[5milesbaby]

In UK area control all bases end in a 5 (FL##5) and we can use the next available level above, therefore providing 500ft at least from a/c outside CAS. However if an a/c is flying the base level, it should be crossing at 90degs thus taking the shortest route at the base level. How this works with MVA's though I'm unsure, need an Approach reply.

[Evil J]

Jack-oh,

As far as I'm aware the minimum radar vectoring altitude is based on terrain clearance rather than related to airspace. many airports with class D the RVA extends beyond CAS. Most controllers will only descend a/c to 500 ft above the base of CAS to provide some separation from anyone transiting underneath or at the base level. But technically, and I;m scratching back to my days at ATC college and aircraft inside CAS is deemed separated from one outside even if the actual separation is minimal. ie base of CAS is 1500 ft, and aircraft flying at 1400 ft is technically separated from one at 1501 ft. I think tyou clutching at straws if your resorting to that sort of sep. but thats what I believe the book says. Alwys remember ofcourse that VFR traffic (which most if not all transits at such low levels will be, do need separating from IFR (or other VFR) traffic.

I'll stop rambling now and wait to be corrected...

[Chilli Monster]

And here comes the correction ;) Always remember ofcourse that VFR traffic (which most if not all transits at such low levels will be, do need separating from IFR (or other VFR) traffic.
MATS 1, Sect 1, Chapter 2 - Classification of Airspace

Class D Airspace - Minimum services by ATC unit

a) Separate IFR flight from other IFR flights

b) Pass traffic information to IFR flights on VFR flights and give traffic avoidance advice if requested

c) Pass traffic information to VFR flights on IFR flights and other VFR flights

Says nothing about separating VFR from VFR

[Evil J]

Quite right, unfortunate typo...omitted the word "not" after "does"-Doh!!

I must proof read better
I must proof read better
I must proof read better
I must proof read better
I must proof read better
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