"Flaps_50!" wrote

How do you know where he was? My point is that its the _lateral_
limits of airspace that can be a no-no for aerobatics. In places,
practice areas may be below other airspace...

You demonstrate that you don't fully understand the pertinent FAR
which I post below. The operable phrase is "of the SURFACE AREA",
not the entire airspace.

"SURFACE AREA"s are normally a 5 mile radius around the airport
for which the airspace is designated. In reading the regulation, I
find no prohibition against conducting aerobatics underneith the outer
rings of a Class B,C,airspace, although, since the outer ring of Class
C airspace can be as low as 1200'AGL, considering 91.303(e), aerobatics
might not be allowed.

Bob Moore
Flying since 1958
CFIing since 1970


Section 91.303: Aerobatic flight.
No person may operate an aircraft in aerobatic flight—

(a) Over any congested area of a city, town, or settlement;

(b) Over an open air assembly of persons;

(c) Within the lateral boundaries of the surface areas of Class B, Class C,
Class D, or Class E airspace designated for an airport;

(d) Within 4 nautical miles of the center line of any Federal airway;

(e) Below an altitude of 1,500 feet above the surface; or

(f) When flight visibility is less than 3 statute miles.

For the purposes of this section, aerobatic flight means an intentional
maneuver involving an abrupt change in an aircraft's attitude, an abnormal
attitude, or abnormal acceleration, not necessary for normal flight.