TM 1-1520-238-T-7
11–57
11–7.
SYSTEM DESCRIPTION (cont)
11–7
(f) The pilot ASE panel (fig. 11–29) controls DASE functions and tests the BUCS system. The operation
of the PITCH, ROLL, YAW, and ATTD/HOVER HOLD switches are identical. Therefore, only the YAW switch shall
be discussed. (Refer to stabilator system for discussion of the NOE/APRCH switch operation.) When the yaw
engage switch is placed to the YAW position, contacts close and apply 28 VDC to the DASEC. The DASEC
performs a BIT and if the yaw passes BIT, a yaw valid signal is enabled. The yaw valid signal energizes a
solenoid that holds the spring-loaded OFF yaw engage switch in the YAW position. Solenoid ground is provided
through the ASE release switch on both cyclic sticks. If either crew member depresses the ASE release switch,
ground for all switches are removed, returning the spring-loaded switches to the OFF position. When the BUCS
TST switch is set to the PLT or CPG position, the rotor brake (RTR BK) on the pilot power quadrant is in the
BRAKE position, both power levers on the pilot power lever quadrant are set to IDLE, and 28 VDC is supplied to
the SPADs selected position for testing.
(g) During SAS operation (fig. 11–30), the DASEC monitors the HARS and the ADSS. When a deviation
from attitude occurs, HARS and ADSS provide signals to the DASEC that correspond to direction and rate of
deviation. The DASEC computes a command signal(s) and applies the signal(s) to the EHV on the
servocylinder(s) and a mathematical model inside the DASEC. Movement of the servocylinder(s) cause the main
and/or tail rotor to correct pitch for deviation. As the servocylinder moves in response to the command signal,
position feedback from the servocylinder LVDT is applied to the DASEC (fig. 11–31). The feedback signal is used
to null out the command signal, preventing oscillations due to overcorrection by the SAS, and is then compared to
the DASEC mathematical model to verify servocylinder command responses. If the mathematical model
command and servocylinder position varies bY 40%, the DASEC commands disengagement of that axis. This
action lights the ASE indicators on the pilot and CPG caution/warning panels.
(h) During CAS operation (fig. 11–30), the DASEC monitors flight controls for movement. When flight
controls are moved by either crew member, mechanical control linkage to the servocylinders cause helicopter
response. At the same time, LVDTs in both crew stations develop a signal that is proportional to the direction and
amount of flight control movement. During CAS, the squat switch disables the yaw channel when the helicopter is
on the ground. LVDT signals are sent to the DASEC. The DASEC then computes a command signal(s)
proportional to flight control movements and applies the signal(s) to the EHV on the servocylinder(s) and a level
detector inside the DASEC. Movement of the servocylinder(s) in response to the command signal(s) cause
position feedback from the servocylinder(s) LVDT to the DASEC. The feedback signal is used to null out the
command signal.
