Final answer:
An Army aviator would participate in a TRSA by contacting radar approach control to request TRSA services, which are provided at their discretion and are not mandatory.
Step-by-step explanation:
An Army aviator would participate in a Terminal Radar Service Area (TRSA) by contacting the radar approach control to avail themselves of the TRSA services. TRSAs are areas where pilots can receive additional radar services, which are provided on a voluntary basis. An Army aviator, like any other pilot, would need to establish communication with the local radar approach or air traffic control facility to request these services. It is not necessary to file a separate flight plan with the local airport authority specifically for the TRSA, nor is it required to inform the local weather station about their flight details. Visual signaling devices are not a method for participating in a TRSA.