CREW
AWARENESS
AIRPLANE
OPERATIONS
MANUAL
2-04-30
Page
14
Code
01
REVISION 38
AOM-145/1114
MODE 4 - INSUFFICIENT TERRAIN CLEARANCE
Mode 4 provides alerts for insufficient terrain clearance with respect to
phase of flight and speed. Mode 4 exists in three forms, 4A, 4B and
4C.
MODE 4A
Mode 4A is active during cruise and approach with the landing gear
UP.
Minimum Terrain Clearance (MTC) for “TOO LOW GEAR” message
triggering:
− Minimum: 30 ft.
− Maximum: 500 ft for an airspeed equal or less than 190 KIAS.
Minimum Terrain Clearance (MTC) for “TOO LOW TERRAIN”
message triggering:
− Minimum: 30 ft.
− Maximum: 1000 ft for an airspeed equal or higher than 250 KIAS.
If during cruise the ground is slowly getting closer and the airplane is
not in the landing configuration or during approach with an
unintentional gear up landing, the aural message "TOO LOW
TERRAIN" will be sounded. Once the message has been issued, an
additional 20% altitude loss is required for the issuing of a new
message.
The "GPWS" warning message is displayed on EICAS for airplanes
equipped with GPWS and the amber "GND PROX" indication on the
PFD for airplanes equipped with EGPWS.
If the airplane penetrates below the 500 ft AGL boundary with the
landing gear still up, the aural message will be "TOO LOW GEAR".
Once a message is issued, an additional 20% altitude loss is required
for the issuing of a new message.
The visual and aural messages cease when the mode 4A is exited.
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