Class D / Class C precedence

Roy Smith wrote:

"Andrew Sarangan" wrote:

This is described in AIM chapter 3. The rules for the more restrictive
airspace will apply when there is an overlap.


That's an odd way to say it. Consider VFR minimums in overlapping Class D
& B airspace (a pretty common occurance for satellite towered airports
under the shelf of a Class B). The Class D rules say "1000 feet above, 500
feet below, 2000 feet laterally" for cloud clearance. The Class B rules
say "clear of clouds". The D rule is more restrictive, but the B rule is
what's in effect.

You can only be in one airspace at a time. At TTD notice the class D
circle isn't a full cirlce. It gets cut off where the class C goes to
the ground. You can really see this at the airport just northwest of
PDX. In the areas depicted that airspace is class D up to the altitude
given, not a mix of class C and D. You don't get to pick a set of cloud
clearance rules to suit your needs.

"a. When overlapping airspace designations apply to the same airspace,
the operating rules associated with the more restrictive airspace
designation apply. "

This is not the same as "the most restrictive rules apply". But you did
state it correctly to start out with.

Jose
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Andrew Sarangan writes:

An obvious example of this is restricted airspaces. The majority of
R-airspaces overlap with G or E airspaces, but in those instances we
don't question which rules apply.

They aren't airspace classes though. Class B and Class C are both
airspace classes; logically they cannot occupy the same space at the
same time.

Restricted and other special airspace is an additional qualifier that
supplements the existing airspace class, so they can coexist.

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Roy Smith writes:

That's an odd way to say it. Consider VFR minimums in overlapping Class D
& B airspace (a pretty common occurance for satellite towered airports
under the shelf of a Class B). The Class D rules say "1000 feet above, 500
feet below, 2000 feet laterally" for cloud clearance. The Class B rules
say "clear of clouds". The D rule is more restrictive, but the B rule is
what's in effect.

Zero clouds is less restrictive than clouds a few thousand feet away?

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Andrew Sarangan writes:

"There are two categories of airspace or airspace areas:

1. Regulatory (Class A, B, C, D and E airspace areas, restricted and
prohibited areas); and

2. Nonregulatory (military operations areas (MOAs), warning areas,
alert areas, and controlled firing areas)."

The two categories can occupy the same space at the same time, but
different classes in the same category cannot.

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Newps writes:

You can only be in one airspace at a time. At TTD notice the class D
circle isn't a full cirlce. It gets cut off where the class C goes to
the ground.

Yeah, but look at the altitudes. The top of the Class D appears to be
_above_ the floor of the Class C that it overlaps.

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Mxsmanic wrote:
Roy Smith writes:

That's an odd way to say it. Consider VFR minimums in overlapping Class D
& B airspace (a pretty common occurance for satellite towered airports
under the shelf of a Class B). The Class D rules say "1000 feet above, 500
feet below, 2000 feet laterally" for cloud clearance. The Class B rules
say "clear of clouds". The D rule is more restrictive, but the B rule is
what's in effect.

Zero clouds is less restrictive than clouds a few thousand feet away?

Not "zero clouds", but "clear of clouds". Having to stay away from a
cloud by only an inch is much less restrictive than having to stay
hundreds of feet away.

Kev

Kev writes:

Not "zero clouds", but "clear of clouds". Having to stay away from a
cloud by only an inch is much less restrictive than having to stay
hundreds of feet away.

Ah ... I thought "clear of clouds" meant "[sky] clear of clouds,"
rather than "[aircraft] clear of clouds."

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Mxsmanic wrote:

Newps writes:


You can only be in one airspace at a time. At TTD notice the class D
circle isn't a full cirlce. It gets cut off where the class C goes to
the ground.


Yeah, but look at the altitudes. The top of the Class D appears to be
_above_ the floor of the Class C that it overlaps.

The class C does not exist where the class D does.