Mode 5 provides two levels of alerting for when the aircraft
descends below glideslope, resulting in activation of EGPWS
caution lights and aural messages.
The first level alert occurs when below 1000 feet Radio
Altitude and the aircraft is 1.3 dots or greater below the beam.
This turns on the caution lights and is called a "soft" alert
because the audio message "GLIDESLOPE" is enunciated at
half volume. 20% increases in the below glideslope deviation
cause additional "GLIDESLOPE" messages enunciated at a
progressively faster rate.
The second level alert occurs when below 300 feet Radio
Altitude with 2 dots or greater glideslope deviation. This is
called a "hard" alert because a louder "GLIDESLOPE,
GLIDESLOPE" message is enunciated every 3 seconds
continuing until the "hard" envelope is exited. The caution
lights remain on until a glideslope deviation less than 1.3 dots
To avoid unwanted Below Glideslope alerts when capturing
the localizer between 500 and 1000 feet AGL, alerting is
varied in the following ways:
• Below Glideslope alerts are enabled only if the localizer is
within 2 dots, landing gear and flaps are selected,
Glideslope Cancel is not active, and a front course
approach is determined.
Mark V and Mark VII EGPWS Pilot's Guide
Rev H, August 2011