TM 1-1520-238-T-5
8–21
8–7.
SYSTEM DESCRIPTION (cont)
8–7
(h) The SDC (fig. 8–13) receives 28 VDC during normal operation and 24 VDC during refueling. The
input voltage is reduced for operation of the instrument system. Power is routed through an internal fuse panel to
two power supplies. The power supplies lower the 28 VDC to signal processing voltages. Operating power is also
routed to the FSC and engine torque sensors. The fuse panel protects all instruments from overload. Forward and
aft fuel cells send low fuel warning signals. The SDC outputs the signals to light the pilot and CPG
caution/warning panel FUEL LOW FWD and FUEL LOW AFT indicators. Engine temperature inputs are
converted by the SDC and sent to the pilot and CPG indicators.
M68-121
TGT 2
SENSOR
DIM /
TEST
PANEL
AIRCRAFT
POWER
BUSES
BATTERY
TGT 1
SENSOR
FORWARD
FUEL
CELL SENSOR
AFT FUEL
CELL
SENSOR
PILOT / CPG
INSTRUMENTS
28 VDC BUS 1
28 VDC BUS 2
MANUAL DIM / BRIGHT
AUTOMATIC DIM / BRIGHT
AUX PWR LAMP TEST
LOW FUEL WARNING
LOW FUEL WARNING
TGT 1 SENSOR DATA
TGT 2 SENSOR DATA
EMERGENCY 24 VDC
SDC
FSC
Figure 8–13.
SDC Functional Block Diagram
