BOMBARDIER BD-100-1A10, Operating Manual

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HYDRAULICS
May 06/2005 Flight Crew Operating Manual Volume 2
REV 2 CSP 100-6
13-01-07
AUXILIARY HYDRAULIC SYSTEM
DESCRIPTION
The purpose of the auxiliary hydraulic system is to provide hydraulic pressure to the lower rudder PCU as a result of the
right hydraulic system failure. The auxiliary hydraulic system includes a DCMP, a reservoir, and an accumulator, all located
aft of the engine rotor burst zone. The right hydraulic system normally powers the lower rudder PCU. During a loss of right
system pressure, a hydraulic switching valve allows the auxiliary system to provide pressure to the lower rudder PCU. The
left or right hydraulic system may be activated without the system already being pressurized. However, the auxiliary system
has an intensifier pressurized by the right hydraulic system. During the preflight check, select R PUMP ON before selecting
AUX PUMP to AUTO to prevent cavitation.
The auxiliary hydraulic system pressure is generated by a constant displacement DCMP. The pump is controlled by a two
position AUX PUMP switch. The OFF position disables the pump. In the AUTO position, a pressure switch allows the
pump to activate as needed.
COMPONENTS AND OPERATION
AUXILIARY DC MOTOR-DRIVEN PUMP
The auxiliary DCMP function is to maintain fluid pressure on the auxiliary system accumulator. When the system pressure
decreases to 2500 psi, an external pressure switch turns on the pump until pressure has reached 3350 psi. At that time, the
pressure switch deactivates, commanding the pump off.
AUXILIARY HYDRAULIC SYSTEM ACCUMULATORS AND RESERVOIR
The auxiliary system accumulator has a nominal gas volume for 50 cubic inches of dry nitrogen, to satisfy the instantaneous
demands of the hydraulic pressure and dampen out pressure surges with in the system. The pre-charge pressure versus tem-
perature is set so that when the accumulator is discharged, the accumulator will still have sufficient oil for a smooth con-
tinuous operation of the lower rudder as the pump comes on line at approximately 2500 psi.
The auxiliary system uses an intensifier to augment the inlet pressure to the auxiliary DCMP to prevent pump cavitation.
The intensifier is a simple spring-loaded piston that transmits pressure from the RH system to the pressure side of the aux-
iliary system reservoir. The DC pumps will come on prior to the engines starting and supply the intensifier with pressure.
The AUX DCMP will come on if the AUX DCMP is selected to AUTO, there is power to the aircraft, and the aux system
accumulator pressure is low. Once the AUX DCMP pressurizes, it is self-priming and its operation is independent of the
RH system.
AUXILIARY SYSTEM SWITCHING VALVE
The function of the auxiliary system switching valve is to transmit right hand system pressure to the lower rudder PCU
under normal operating conditions. With loss of RH hydraulic system pressure, the switching valve shuttles and applies
Auxiliary System pressure to the lower rudder PCU. The valve shuttles strictly in accordance with the RH System pressure
and does not rely on any software or electrical interface to function.
AUXILIARY SYSTEM PRESSURE FILTER
The aux system contains a pressure filter. This assembly filters the supply pressure fluid coming in from the DCMP. It is
made up of a filter element and a bowl, a differential pressure indicator, and an automatic shutoff device. The filter is a non-
bypassing design. The flow through the assembly is blocked when the bowl is removed. A filter element is provided which
removes 100% of all contaminants larger than 15 microns and is a non-cleanable type. The auxiliary system pressure filter
and the case drain filter element used on the filter manifolds of the left and right systems are identical, and interchangeable.