This chapter discusses the radio systems installed on the aircraft. The information is designed to
provide you with a basic understanding of these systems to aid in understanding operating
procedures and limitations.
1101. ENABLING OBJECTIVE
Recall the basic description, related systems, and procedures for operating the communications
and navigation systems.
1102. ENABLING STEPS
List the components of the communications system.
State the function and location of the COM SQ key.
State the function of the GND COMM PUSH switch.
Discuss communications tuning using the RTU.
Discuss communications tuning using the CDU.
1103. COMMUNICATIONS SYSTEM
The comm system consists of UHF and Very High Frequency (VHF) systems. The UHF
portion of RTUs 1/2 or the CDU controls the UHF and VHF transceivers. Both VHF and UHF
transceivers may be operated simultaneously without degradation of intelligible comm.
The RTU comm controls are the frequency control knobs, the 1/2 function key, and line select
keys. The CDU comm controls are the comm function key and line select keys. A ground
comm push-to-engage switch allows UHF or VHF comm during ground operations using battery
1104. COMMUNICATION SQUELCH FUNCTION KEY
The comm squelch function key placarded COM SQ, allows the crew to momentarily disable the
comm transceivers squelch circuit. This allows the crew to receive weak/distant radio signals.