52.75 Airspace

52.75.2 State the rules pertaining to operating IFR in the various classes of airspace. CAR 91 & AIP ENR

91.245 Operations in controlled airspace 

(A) Except as provided in paragraphs (e) and (f), a pilot-in-command of an aircraft must not enter a control area or control zone designated under Part 71 unless the pilot-in-command obtains an ATC clearance to enter the control area or control zone.

(B) A pilot-in-command of an aircraft operating in Class A airspace must—

(1) operate the aircraft under IFR; and

(2) unless otherwise authorised by the ATC unit responsible for the class A airspace, maintain two-way communications with that ATC unit on the appropriate frequency.

(C) A pilot-in-command of an aircraft that operates in the following classes of airspace must maintain two-way radio communications with the ATC unit responsible for the airspace concerned on the appropriate frequency unless otherwise authorised by the ATC unit:

(1) Class B, C, or D airspace:

(2) Class E airspace under IFR.

52.75.4 Describe the vertical limits and purpose of control zones (CTR). CAR 71

71.55 Control zones 

(A) The Director may designate as a control zone that portion of airspace around an aerodrome if—