MD-11 Flight Crew Operations Manual
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Instrumentation and Navigation -
Description and Operation
Inst.10.6
G/x (x is other position updating systems, e.g. I, R, DD) is displayed on both ND
(navigation mode field) and FMC POS REF page 1/3 (line 1, label field) when
GNS is being used as an FMC position update source. GNS position updating to
the FMC can be manually inhibited by selecting the GNS NAV INHIBIT* prompt
displayed on the POS REF page 1/3. Selecting GNS NAV INHIBIT* inhibits all
FMC position updates based upon GPS. Re-enabling GNS position updating to
the FMC is accomplished by selecting the GNS NAV ENABLE* prompt. GNS
time and date is utilized by the FMS regardless of GNS inhibit state. Manually
inhibiting GNS position updating to the FMC does not affect the GNS output to
using systems. No other controls are provided.
NAV Radio Tuning
Navigation radio stations are stored in the Nav Data Base (NDB). VOR/DME and
ILS radios are normally tuned and updated automatically by the on-side FMC.
On-side means that the Captain's radios are tuned by FMC-1, and the First
Officer's radios are tuned by FMC-2. Any radio can be manually tuned from either
MCDU.
ADF stations are tuned in the following order of priority:
1. Pilot manually tunes a station.
2. FMC tunes a station required for current leg.
3. FMC tunes a station required for an upcoming F-PLN waypoint.
4. FMC tunes a station required for a preceding F-PLN waypoint.
ADF stations are never used for radio position computations.
Radio Altimeter System
The radio altimeter system provides terrain clearance (altitude) data during
approach, landing, or climb out. The altitude range of the system is from 2,500 feet
to touchdown.
The altitude indications are displayed on the PFDs. The decision height minimum
can be set by turning the inner knob of the MINIMUMS control knob on the ECPs.
The radio altimeter uses an FM radio wave to measure the distance between the
aircraft and the terrain. The radio altimeter uses two microprocessors, one for
altitude calculation and one for monitoring.
Three radio altimeter transceivers are located in the center accessory
compartment. The transmitter and receiver antennas are installed on the bottom of
the fuselage.
October 02, 2006
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