Class E or Class G - another one of those that makes you go 'hmmmmm'

"JT" wrote in message
...

We all know (or should) that when a Class D airport tower closes, the
airspace reverts to Class E or Class G and is specified in the A/FD.
Question is what determines which airspace it reverts to???

CFI Test Prep question 6930 answer states, "When that tower ceases to
operate, it reverts to Class E Airspace. Without weather reporting
capability, Class E airspace reverts to Class G airspace. (AIM 3-2-5)".

AIM 3 - 2 - 5 states "At those airports where the control tower does not
operate
24 hours a day, the operating hours of the tower will be listed on the
appropriate charts and in the A/FD. During the hours the tower is not in
operation, the Class E surface area rules or a combination of Class E
rules to 700 feet above ground level and Class G rules to the surface will
become applicable. Check the A/FD for specifics."

The AIM doesn't help here but the test prep implies that without weather
reported capability, the airport reverts to the less restrictive Class G.
So, we look at our favorite sectional (in this case, Seattle), and we see
that, in most cases, part-time towered Class D airports under the Class B
veil go to Class G while those outside go to Class E (weather reporting
capability doesn't seem to be a factor). Then when you look at Pasco
(KPSC), we see it is not under the Class B airspace but reverts to Class G
AND has weather reporting (ATIS and ASOS).

So, can anyone enlighten me as to the rule behind this? Does it have to do
with sunspots and the phase of the moon?


A surface area requires:

1.) Communications. Communications capability with aircraft which normally
operate within the surface area must exist down to the runway surface of the
primary airport. This communications may be either direct from the ATC
facility having jurisdiction over the surface area or by rapid relay through
other communications facilities which are acceptable to that ATC facility.

2.) Weather Observations. Weather observations shall be taken at the
surface area's primary airport during the times the surface area is
designated. The weather observation can be taken by a Federally
certificated weather observer and/or by a Federally commissioned weather
observing system.

If the tower is responsible for taking weather observations, then when the
tower closes the airspace must become Class G. If the tower serves as the
rapid communications relay for the ATC facility having jurisdiction over the
surface area, then the airspace must again become Class G when the tower
closes, even if weather observations are still taken by another entity, such
as an AWOS or ASOS.

If communications still exist and weather observations are still taken after
the tower closes, then the airspace can become Class E or Class G. It will
become Class E if necessary to accommodate instrument procedures if such
action is justified and/or in the public interest. The following factors
are among those that are considered:

1. Type of procedure including decision height or minimum descent
altitude.

2. The actual use to be made of the procedure, including whether it is
used by a certificated air carrier or an air taxi/commuter operator
providing service to the general public.

3. The operational and economic advantage offered by the procedure,
including the importance and interest to the commerce and welfare of the
community derived by the procedure.

4. Any other factors considered appropriate.