VFR on top

"Peter" wrote in message
...

wrote

Ah, but the main advantage (AIUI) is that the IFR clearance "VFR on top"
gives
you the flexibility of chosing your own routing while still staying in the
system. In
congested airspace, it's often unlikely they'll give you a routing at IFR
altitudes
due to conflicting traffic. With VFR on top they're more likely to let
you through
without a big diversion.

Why would this be?

Forgive me for looking at this from the Euro POV, but it is true that
if outside CAS one can fly anywhere one likes if VFR, whereas if IFR
one is supposed to fly on ATS routes (published airways).

However, there are countries (e.g. Greece) where *all* traffic (incl.
VFR) is supposed to be on airway routes, and one can also get DCT
clearances when IFR.

Moreover, I can be flying VFR in CAS (say Class C) and be talking to
some IFR (approach or departure) ATC unit, and they will be watching
me (with a Mode C squawk) and in effect separating me and other
traffic, occassionally giving me vectors. This is VFR, but it makes
perfect sense.

So I can't see why ATC would allow more routing leeway if VFR than if
IFR. Does the minimum separation change?

Yes, you are looking at it from a euro-POV and I think that's the
disconnect.

In US Class D & E VFR are not separated from IFR.

In the US virtually all airspace is some class of controlled airspace; not
just airways and terminal areas. There is some Class G (just enough to
prompt some gotcha test questions or usenet replies) but for most
discussions it's N/A.

Within all that controlled airspace only one controller provides ATC Service
within any one particular chunk of airspace.

Since there is (virtually) no uncontrolled airspace and only one controller
is responsible for the controlled airspace (and thus should have his Big
Picture) there are no provisions (or really any need) for the ATSORA (RIS
and FIS but especially RAS) that you find in the UK.

When an aircraft in probably 90% of US airspace is VFR or in this discussion
VFR-On-Top, ATC is not responsible for separation.

The two main reasons for IFR re-routes or request denials are separation and
traffic flow/sequencing into the terminal area. Since VFR-On-Top
eliminates separation as a reason and sequencing only matters in the
terminal area the result is more flexibility when it comes to routing.

KP wrote:

In the US virtually all airspace is some class of controlled airspace; not
just airways and terminal areas. There is some Class G (just enough to
prompt some gotcha test questions or usenet replies) but for most
discussions it's N/A.

You must be east of the Mississippi. Look west. We have a lot of
uncontrolled airspace out here.

"Newps" wrote in message
...


KP wrote:

In the US virtually all airspace is some class of controlled airspace;
not just airways and terminal areas. There is some Class G (just enough
to prompt some gotcha test questions or usenet replies) but for most
discussions it's N/A.

You must be east of the Mississippi. Look west. We have a lot of
uncontrolled airspace out here.

I am west.

Everything is relative and should be taken in context.

Compared to europe, and the UK in particular, where controlled airspace
consists of airways, fairly small, congested control zones, and that's about
it, the percentage of Class G in the Western US is insignificant.
Especially when compared to the amount of traffic (IFR and VFR) each
contain.

The civil controllers over there are pretty much hog-tied by a lack of
airspace to put IFR airplanes (which must remain in controlled airspace).
When I left in '92 timed approaches from holding patterns were SOP at
Heathrow. Just about everybody's on an airway; no off-airways directs and
not much in the way of re-routes available (they're all full).

If that's your context the idea that being VFR-On-Top could have any effect
on an aircraft's routing probably wouldn't register. There's no place else
to go regardless of whether you're at a hard altitude or OTP.

Outside of controlled airspace everybody's technically uncontrolled under
see-and-avoid. Whether they're in clear-and-severe or completely Popeye.
There are various types of air traffic services available from military
radar facilities. It's pretty much a free-for-all with multiple facilities
working aircraft in the same airspace. A coordination nightmare where you
must separate aircraft on your freq by 5NM or 5000 Mode C from any
unidentified or uncoordinated radar target.

If you haven't endured it it's a real head shaker :-/

"KP" nospam@please wrote in message
. ..
"Newps" wrote in message
...


KP wrote:

In the US virtually all airspace is some class of controlled airspace;
not just airways and terminal areas. There is some Class G (just enough
to prompt some gotcha test questions or usenet replies) but for most
discussions it's N/A.

You must be east of the Mississippi. Look west. We have a lot of
uncontrolled airspace out here.

I am west.

Everything is relative and should be taken in context.

Compared to europe, and the UK in particular, where controlled airspace
consists of airways, fairly small, congested control zones, and that's
about it, the percentage of Class G in the Western US is insignificant.
Especially when compared to the amount of traffic (IFR and VFR) each
contain.

The civil controllers over there are pretty much hog-tied by a lack of
airspace to put IFR airplanes (which must remain in controlled airspace).
When I left in '92 timed approaches from holding patterns were SOP at
Heathrow. Just about everybody's on an airway; no off-airways directs and
not much in the way of re-routes available (they're all full).

If that's your context the idea that being VFR-On-Top could have any
effect on an aircraft's routing probably wouldn't register. There's no
place else to go regardless of whether you're at a hard altitude or OTP.

Outside of controlled airspace everybody's technically uncontrolled under
see-and-avoid. Whether they're in clear-and-severe or completely Popeye.
There are various types of air traffic services available from military
radar facilities. It's pretty much a free-for-all with multiple
facilities working aircraft in the same airspace. A coordination
nightmare where you must separate aircraft on your freq by 5NM or 5000
Mode C from any unidentified or uncoordinated radar target.

If you haven't endured it it's a real head shaker :-/

I would agree its a real belter flying IFR in uncontrolled airspace taking
Radar Advisory Service when a nearby aircraft might be getting a service
from someone else. It become a real relief when you can move into Controlled
airspace usually Class A and have the benefit of London Control looking
after you. But getting into CAS is not easy either even with an IFR flight
plan.