KLM MD-11 - Weather Radar System; Inertial Reference System (IRS)

MD-11 Flight Crew Operations Manual
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Instrumentation and Navigation -
Description and Operation
Inst.10.7
Weather Radar System
The dual weather radar system with consists of a receiver/ transmitter, control
panel, and antennas.
The radar detects and displays areas of severe weather and ground mapping on the
ND. Different levels of precipitation are displayed with appropriate colors as
green, yellow, red, and magenta.
Both the Captain and First Officer may choose their own range for displaying
weather information.
Inertial Reference System (IRS)
The IRS continuously computes:
• Latitude and longitude.
• Track.
• Attitude.
• Heading (magnetic and true).
• Vertical speed.
• Ground speed.
The IRS interfaces with several aircraft systems including the FMS and the
Automatic Flight System (AFS).
The IRS is powered by 115-volt ac power. About 15 minutes of backup DC power
is available from a dedicated battery.
EAD alerts provide the flight crew with IRS status information. IRS faults are
stored in the Centralized Fault Display System (CFDS) for review by maintenance
personnel.
The IRS control panel provides mode selecting and annunciation for the three
IRUs. Each IRU (1, 2, and AUX) has a mode selector and a NAV OFF light. When
the selector is set to NAV, the respective IRU powers-up and enters the align
mode for about 10 minutes. During this time NO TAXI will appear on the PFD
airspeed tape. The pilot can enter position into the MCDU during this time.
After 10 minutes in the align mode, the IRU automatically enters the nav mode.
During nav mode, navigation and steering are done by the FMC. No pilot inputs
to the IRUs are accepted during operation in the nav mode. In-flight realignment
of the IRS is not possible.
The Inertial Aural Warning Logic Unit provides an aural warning horn if the
aircraft is on the ground with the mode selector set to NAV, and cooling air is not
being supplied to the IRU’s, electrical power is removed from the aircraft, or the
battery switch on the electrical control panel has been left on.
November 16, 2009