Honeywell SPZ-8000 Pilot's Manual page 195

SPZ--8000 Digital Integrated Flight Control System
When the aircraft approaches the glideslope beam, the vertical beam
sensor monitors TAS, vertical speed, and glideslope deviation to
determine the correct capture point. When glideslope capture occurs,
the computer drops all other active vertical modes, and automatically
generates a pitch command to track the glideslope beam, as shown in
Figure 8--28.
At this time, the EADI annunciates the following, as shown in Figure 8--29:
LOC
D
GS (flashes for 5 seconds, then steady, to indicate capture mode).
D
Gain programming is performed on the glideslope signal to compensate
for the aircraft closing on the glideslope transmitter, and beam
convergence caused by the directional properties of the glideslope
antenna. Glideslope programming is normally computed as a function
of radio altitude and vertical speed.
If the radio altimeter is not valid, then glideslope gain programming is
computed as a function of preset height above runway estimates and
run down as a function of true airspeed and time.
Modes of Operation
8-34
Approach Mode Track
Figure 8--28
A28--1146--055
REV 2