Honeywell SPZ-8000 Pilot's Manual page 208

When these three conditions are met, the altitude preselect mode is
dropped and the system automatically transitions to the altitude hold
mode.
The altitude hold mode is dropped if the pitch wheel is moved. Altitude
preselect is automatically armed if the aircraft is 250 feet away from the
altitude preselect setting and has a vertical speed component in the
direction of the selected altitude.
The altitude preselect mode profile is shown in Figure 8--37 and
described in Table 8--7.
Step
1 Set the selected altitude on the EADI. (i.e., 15,000 feet in
Figure 8--38.)
2 Engage the FLC mode to descend toward the selected
altitude.
Altitude Preselect Mode Procedure
A28--1146--055
REV 2
SPZ--8000 Digital Integrated Flight Control System
Altitude Preselect Mode Profile
Figure 8--37
Procedure
Table 8--7
Modes of Operation
8-47