MD-11 Flight Crew Operations Manual
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Communications -
Description and Operation
Comm.10.2
The frequency selection for the HF communications system is controlled from the
CRP. HF radios must not be operated during airplane refueling operations due to
the possibility of arcing.
Communication Radio Panel
Three Communication Radio Panels (CRP) are installed on the aft pedestal to
provide tuning of the communications systems.
The interface between CRPs allows tuning of the communications radios from any
panel. Pushing one of the five radio select switches on the panel (VHF1, VHF2,
VHF3, HF1 or HF2), illuminates the selected switch, and the associated ACTIVE
and STBY frequencies are displayed. New frequencies are placed in the STBY
memory and transferred to the ACTIVE mode by use of the transfer button.
The three CRPs can be used simultaneously, provided radio selection (VHF1,
VHF2, VHF3, HF1, HF2) differs from another CRP. Only one radio may be
selected on an individual CRP.
Audio Control Panel
Two Audio Control Panels (ACP) are installed on the aft pedestal and one is
installed at the observer station.
The ACPs provide the following functions:
• Communication radio transmit and volume control.
• Navigation radio ident and volume control.
• Flight/service interphone transmit and volume control.
• PA transmit and volume control.
Transmitting can be done using a handheld, boom, or oxygen mask microphone.
The handheld microphone cannot be used for the PA system.
Flight Interphone System
The flight interphone is controlled by three ACPs.
Jacks for the boom and handheld microphone are installed at the Captain's, First
Officer's, and right Observer's stations. A flight interphone jack is installed at the
ground power receptacle, the nose landing gear, and in the avionics compartment.
In addition, the oxygen masks in the cockpit each include a microphone which
automatically switches from the boom microphone to the mask microphone when
the oxygen mask PRESS TO TEST AND RESET lever is pushed, or when the
oxygen mask stowage box doors are opened.
Automatic transfer from mask microphone back to boom microphone is initiated
by closing the left mask stowage box door and pushing the PRESS TO TEST
AND RESET lever.
October 02, 2006
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