Honeywell SPZ-8000 Maintenance Manual page 587

The FLCH mode is annunciated on the PFD by a green IAS or MACH.
The VFLCH
mode is annunciated on the PFD by a green VIAS or
VMACH .
In FLCH and VFLCH, all armed pitch flight director
modes are allowed, but the capture of any armed pitch mode will
override the mode.
The FLCH and VFLCH mode is set up to change level from present
altitude to the preselected altitude. It will try to maintain
the speed reference over the long term and allow vertical
speed
to change, as a function
of power setting. For example,
throttle retard in a climb will cause the system to track the
speed reference while bleeding off vertical speed.
However, vertical speed will not be allowed to go below zero.
If throttle retard in a climb was enough to cause vertical
speed to go to zero, vertical speed would be held to zero and
the aircraft would decelerate. At this time, the flight
director command cue on the PFD would be out of center,
indicating that power should be applied to track the FLCH or
VFLCH speed reference.
In
the FLCH or VFLCH mode, the AFCS should fly to the new
preselect altitude at the target speed from the FMS or as
manually selected on the GP-820, when aircraft thrust is set
appropriately for climb or descent. When the power is not set
appropriately, then the AFCS should maintain zero vertical
speed in order to not fly away from the preselected altitude.
If the target speed is changed from IAS to MACH (or vice
versa), the FLCH or VFLCH mode should remain engaged and fly to
the appropriate new speed target.
The DAFCS pitch guidance will @ generate commands to exceed
v
or M~Q when in FLCH or VFLCH mode. This speed limiting
f~~ction Includes anticipation to account for flight envelope
v
and/or MH
?
discontinuities. The vertical guidance will not
c&mand more han tO.2 g in FLCH and VFLCH modes.
Once in the FLCH mode the target speed can be changed via the
GP-820 SPEED knob if using manual speed.
NOTE : Depressing the GP-820 FLCH button will automatically
select either IAS or MACH modes as function of aircraft
pressure altitude. At altitudes greater than 27,850
feet, Mach will automatically be selected. If FLCH is
selected at or below 27,850 feet pressure altitude, the
IAS mode will automatically be selected. The pilot can
change this automatic selection at any time by pushing
the GP-820 IAS/MACH button.
22-14-00
Page 298.112
Apr 15/93
Use or disclosure of information on this page is subject to the restrictions onthe title page of this document.