Two airspace classes for one airspace? (KOQU)

"John R" wrote in message ...
[...]
So according to the chart, the Class D airspace extends to 2500
feet. However, Quonset tower was sternly warning pilots the
other day that their Class D only went to 1300 feet and not to
exceed that without the blessing of Providence. So why does the
chart say 2500 feet for the Class D inside the Class C ring?

Because that's what they write at all the Class D airports, as near as I can
tell. They just look at the airport elevation, add 500', and put that on
the chart.

We have several Class D airports in our region that underlie the SeaTac
Class B airspace. All have letters of agreement with the SEA approach
facility reducing their Class D ceiling. In one case, the Class D ceiling
is the Class B floor (BFI), and in the other cases, the reduced ceiling of
the Class D either creates or expands a charted Class E area between the
Class D and Class B airspace. The situation around BFI sounds most similar
to yours, where the charted Class D overlaps with the Class C airspace.

Frankly, I find the whole thing very confusing. In the case of BFI, it's
(almost) clear, because the floor of the Class B is clearly marked as being
below the marked ceiling of the Class D. You know (that is, you can assume)
you're either in Class D or Class B, and it's very clear where the Class B
ends. But in the other cases, it's not clear at all if what's really going
on is that the airspace ceded to the SEA approach facility winds up being
Class E, or if it's Class D or Class B (and controlled by SEA App/Dep either
way).

I have always treated the ceded airspace as Class E and no one has ever
taken me to task, even when I was on a tower frequency. So I presume that's
fine to do. But the whole situation highlights the incredibly poor degree
to which these letters of agreement and related arrangements are
communicated to the pilots that they affect.

Pete