What conditions govern the necessity of two-way radio communications in Class D airspace?

In Class D airspace, two-way radio communications are required when entering and exiting the airspace to ensure the safe and organized flow of air traffic. This communication helps pilots coordinate their movements with air traffic control (ATC) and other aircraft within that airspace, enhancing safety as aircraft share the airspace. The requirement is not based solely on altitude, type of aircraft, or flight duration, but specifically relates to the need for communication when transitioning into and out of this controlled environment. By establishing this communication, pilots can receive crucial information about traffic, weather, or any changes in ATC instructions while operating within Class D airspace.