737 MAX Flight Crew Operations Manual
Communications -
System Description
MN-FLT-OH-201
5.20.3
1B401, 1B402, 1B801 - 1J594
The ACP transmitter selectors are not functional. Any transmission from that
station must be from the radio shown on the chart below. The transmitter selector
for the usable radio illuminates when a station is operating in the degraded mode.
The receiver switches are not functional, and only the usable radio is heard at a
preset volume, through the headset. The speaker and speaker switch are not
functional at that station. In addition, the flight interphone and service interphone
cannot be used. The control wheel PTT switch INT position and the ACP PTT
switch INT position are not functional since the flight interphone is not functional.
1B401, 1B402, 1B801 - 1J594
The mask and boom microphones can be used for transmission on the usable
radio. The mask and boom microphones can be keyed with the control wheel PTT
switch in the MIC position or the ACP PTT switch in the RADIO position. The
hand microphone is not usable in the degraded mode of operation.
Audio warnings for altitude alert, GPWS, and windshear are not heard on an audio
system operating in the degraded mode.
An audio system operating in the degraded mode cannot access the passenger
address system through the audio control panel. The crewmember can still use the
service interphone handset and PA microphone if they are installed on the control
stand.
Flight Interphone System
The flight interphone system is an independent communication network. Its
primary purpose is to provide private communication between flight deck
crewmembers without intrusion from the service interphone system. The ground
crew may also use the flight interphone through a jack at the external power
receptacle.
The pilots can transmit directly over the flight interphone by using the control
wheel or glareshield PTT switches. Alternately, any crewmember with an ACP
can transmit/receive over the flight interphone by using their related ACP and
normal PTT switches. Any standard microphone may be used with the flight
interphone system.
CREW STATION AUDIO SYSTEM IN
DEGRADED MODE
RADIO AVAILABLE FOR
TRANSMISSION AND RECEPTION
AT DEGRADED STATION
CAPTAIN
VHF–1
FIRST OFFICER
VHF–2
OBSERVER
VHF–1
March 1, 2021
