Page 17-20
Section III Sub-section 17
AVIONICS
P/N 140-590032-0007
Revision A4: Sep, 2010
Pilot’s Operating Manual
MODE 5
Alert To
Descent Below
Glideslope
This mode is active when the following conditions are present:
• A valid glideslope signal is present.
• The EGPWS is in the approach mode or the flaps are in the landing
configuration.
• GS INHIB button has not been used to cancel glideslope.
• The landing gear is in the DOWN position.
• Radio altimeter indicates more than 30 ft AGL.
• Mode 5 is not inhibited by back course select or other inhibit signal.
Pushing the illuminated GS INHIB switch momentarily cancels the
glideslope alerts until the cancel logic is reset. Pushing the illuminated
GS INHIB switch resets the cancel logic. The cancel logic resets auto-
matically when the radio altimeter indicates more than 1500 ft AGL or
less than 30 ft AGL or a non-ILS frequency is selected.
The Mode 5 alert envelope is enabled by glideslope deviations over
1.3 dots and radio altitudes between 300 and 1000 ft AGL (typical). The
Mode 5 warning envelope is enabled by glideslope deviations over 2
dots and radio altitudes below 300 ft AGL.
If the airplane flight profile goes into the alert envelope, the soft
"GLIDESLOPE" warning sounds and the GLIDESLOPE annunciator
illuminates.
If the airplane flight profile goes into the warning envelope, the loud
"GLIDESLOPE" warning sounds and the GLIDESLOPE annunciator
illuminates.
Upon going out of the Mode 5 alert or warning envelope, the voice
messages stop and the GLIDESLOPE annunciator extinguishes.
NOTE: To permit maneuvering on final approach with an unreliable
glideslope, the GLIDESLOPE message can be inhibited by
pushing the GS INHIB switchlight when the airplane is below
2000 ft AGL. The GLIDESLOPE messages are automatically
inhibited during Back Course approaches.
Mode
Operational Envelope
