TM 1-1520-238-10
Change 9
2-48.1
LVDT (17.5% or approximately 1.75 INCHES, except in
longitudinal aft where the mistrack must be 22.5% or
approximately 2.25 INCHES). The BUCS flight control
logic will wash in full authority over a period of approxi-
mately one (1) second allowing the pilot to transition to
BUCS controlled flight. The BUCS ON and ASE (ASE not
applicable for collective) caution/warning lights will illumi-
nate. SAS will be OFF in the engaged axis. Force trim will
be available in all axes. Attitude/Hover hold will be avail-
able in the axes that SAS is available.
(b) Severance between crewstations. If a
severance occurs between the crewstations the pilot will
retain full mechanical control. The pilot should keep flying
on the mechanical flight controls. The BUCS FAIL warn-
ing light and ASE (ASE not applicable for collective) cau-
tion/warning light will illuminate when a mistrack is de-
tected between the pilot control LVDT and the CPG
control LVDT. The CPG control will not follow control in-
puts in the axis that is severed. SAS will be OFF in the en-
gaged axis. Force trim feel will not be available to the CPG
in the engaged axis. Attitude/Hover hold will be available
in the axes that SAS is available.
d. Control System Engagement Logic (Copilot
crewstation CPG flying the aircraft).
(1) Jams. The CPG will have to decouple the
SPAD. BUCS will automatically engage in the affected
axis. Breakout values will be approximately 15% higher
than the pilots values. The CPG can expect the control to
displace to full travel when the SPAD releases. The DA-
SEC will wash in full authority over a period of approxi-
mately three (3) seconds allowing the CPG to center the
controls and transition to BUCS controlled flight. The
BUCS ON and ASE (ASE not applicable for collective)
caution/warning lights will illuminate. SAS and force trim
will be OFF in the engaged axis. Attitude/Hover hold will
be available in the axes that SAS is available.
(2) Severances.
(a) Severance aft of the pilots control. A
severance can occur due to malfunction or battle damage
between the pilots controls and the actuator. Because the
two crewstations are still mechanically linked together,
this type of severance will operate the same as in the pilot
station. BUCS will automatically engage when both the pi-
lot and CPG LVDTs achieve the proper mistrack with re-
spect to the RAM LVDT. The DASEC will wash in full au-
thority over a period of approximately one (1) second
allowing either crewmember to transition to BUCS con-
trolled flight. The BUCS ON and ASE (ASE not applicable
for collective) caution/warning lights will illuminate. SAS
will be OFF in the engaged axis. Force trim will be avail-
able in all axes. Attitude/Hover hold will be available in the
axes that SAS is available.
CAUTION
The effect of the CPG assuming control
with the BUCS trigger select is to trans-
fer control of the aircraft from a flight
control that still retains some integrity to
that of a nonredundant electronic
means of flight control. This shall only
be activated if the pilot is incapable of
flying the aircraft.
NOTE
The CPG must create sufficient mistrack. If
the CPG repositions the flight control (af-
fected axis) to a position that is is less than
the appropriate mistrack value and engages
the BUCS trigger, engagement will not oc-
cur. The CPG may engage the trigger and
hold it prior to achieving the mistrack. BUCS
engagement will occur when the proper mis-
track is reached.
(b) Severance between crewstations. If suf-
ficient mistrack is detected between the pilot control posi-
tion and the CPG control position the BUCS FAIL and
ASE (ASE not applicable for collective) caution/warning
lights will illuminate. In this instance the pilot still has full
mechanical control. The CPG should transfer control of
the aircraft to the pilot. If it is necessary for the CPG to fly
the aircraft, the BUCS trigger should be engaged and
BUCS control will be established after sufficient mistrack
between the CPG control position and the RAM position is
reached. The DASEC will wash in full authority over a pe-
riod of approximately one (1) second allowing the CPG to
transition to BUCS controlled flight. SAS will be OFF in the
engaged axis. Force trim feel will not be available to the
CPG in the engaged axis.
e. BUCSFlight Transfer of Controls. Transfer of
controls should only be accomplished if the flying crew-
member is incapacitated or in the case of the CPG flying
the aircraft and a severance occurs between the crewsta-
tions. Table 23 lists the procedures for transfer of control
between the crewmember in BUCS and the opposite
crewmember.