MD-11 Flight Crew Operations Manual
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Instrumentation and Navigation -
Description and Operation
Inst.10.4
Distance Measuring Equipment (DME)
The DME radio system functions as an aircraft navigation aid in the frequency
range of 960 to 1,215 MHz. Two DME interrogators are installed.
The DME transmits coded interrogation signals (pulsed pairs) to the ground
station. The ground station receives the interrogation signal and returns a coded
reply signal (pulse pair) for each interrogation. One antenna is used for both
transmission and reception.
The DME measures the slant range distance between the aircraft and ground
stations. The DME can provide multiple station distance data to the FMS for high
accuracy position fixing.
The DME can use up to five ground stations at once. The DME provides for 200
channels. Distance is sent to the NDs.
The DME is tuned automatically by the FMS. In case of FMC failure, the MCDUs
may be used to provide backup inertial navigation, flight planning, coupled lateral
guidance, and MAP display capability. To support these functions, each MCDU
can generate its own limited page displays.
Automatic Direction Finding (ADF)
The ADF radio functions as an aircraft navigation aid in the frequency range of
190 to 1,750 KHz.
The ADF receiver provides relative bearing information for display on the NDs.
Relative bearing is sensed and computed electronically. The single pointer
represents ADF1 and the double pointer represents ADF2.
The ADF selects signals from a sense antenna (omnidirectional) and two
directional loop antennas. Audio volume and tone filter controls are on the audio
control panels.
Instrument Landing System (ILS)
The ILS components consist of:
• Two ILS receivers installed in the main avionics rack.
• Two glide slope (G/S) antennas installed in the radome.
• Two G/S antennas installed in the nose landing gear (NLG).
• Two VOR/LOC antennas installed on the tail.
The ILS receiver provides localizer and G/S course information to the AFS and
GPWS.
ILS frequencies are from 108.10 to 111.95 MHz.
The localizer and G/S deviation data are shown on the PFDs and NDs.
October 02, 2006
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