1.16 HYDRAULIC SYSTEM Continued.
1.16.7 Static Mode, Internal Power, Cool Mode, Rib Fan On, Full NBC.
When the hydraulic circuit is in cool mode (figure 1-13) and air beam pressure is reduced to 1.5 psi for any
reason, the rib fan motor, M4, is automatically turned on. This is accomplished by applying +24 Vdc to the
coils of solenoid valves SV2, SV5, SV7, SV8, and SV9. SV2, SV5 and SV8 are opened and SV7 and SV9 are
closed. This diverts the hydraulic fluid flow away from the compressor motor M1A and condenser fan, M1C,
and through the rib fan motor, M4. The increased pressure sensed at LS3 is diverted to PD1 and closes it
preventing the hydraulic fluid flow to the condenser motor, M1C. SV4 remains open but the hydraulic fluid
flow seeks the path of less resistance through the rib fan motor, M4. The speed of the rib fan is controlled by
flow control FP5 which diverts hydraulic fluid flow around the rib fan motor to limit its speed and pressure
for safety. When air beam pressure is increased to 2.9 psi, the system is returned to the previous condition.
Figure 1-15. Static Mode, Internal Power, Cool Mode, Rib Fan On, Full NBC