alexpc,
http://www.bartleby.com/116/213.html
'Shall' is neither conditional nor contingent. The regulation is very clear on the
duty to receive information before operating in an ATZ. A mere acknowledgement of radio contact is insufficient for this purpose. Furthermore where an officer (or a/g radio operator) fails to reply owing to high workloads it is evident additional ATZ operations cannot be carried out safely.
Airmanship (imo) generally dictates that an aircraft
should not over-fly in close proximity the aerodrome traffic zone of an aerodrome unless the commander of the aircraft has [contacted] the air traffic control unit [etc] at the aerodrome to enable the flight to be conducted with safety.