Signals from the primary pump switches for the center system ACMPs go directly to the ELMS. The HYDIM cards do not control primary pump operation.
Demand Pump Operation
Signals from the demand pump selectors for the left and right system ACMPs go to the HYDIM cards and to the ELMS. When a selector is in the ON position, the signal goes directly to the ELMS. When a selector is in the AUTO position, HYDIM cards control the pump operation signal to the ELMS.
When the left demand pump selector is in AUTO, the left HYDIM card operates the left ACMP for any of these conditions:
*
Left engine not running
*
Touchdown -CAS is more than 60 kts and altitude is less than 30 feet (to prepare for auto speedbrake operation)
*
Left EDP pressure less than 2400 psi (pump turns off 15 seconds after EDP pressure is more than 2800 psi).
When the right demand pump selector is in AUTO, the right HYDIM card operates the right ACMP for any of these conditions:
*
Right engine not running
*
Altitude is less than 30 feet (prepares for wheel brake and auto speedbrake operation)
*
Right EDP pressure less than 2400 psi (pump turns off 15 seconds after EDP pressure is more than 2800 psi).
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MAIN HYDRAULIC SYSTEMS -FUNCTIONAL DESCRIPTION -ALTERNATING CURRENT MOTOR PUMP
ELMS Operation
The ELMS electronics unit (EEU) in the power management panel gets the pump control signal from the pump switches or HYDIM cards. The electronics unit then sends a signal to the electrical load control unit (ELCU) in the power panel. If the switch or selector is in the OFF position, the ELCU does not get the signal. If the selector is in AUTO or ON or if the switch is in ON, the ELCU gets the signal and energizes a relay to supply electrical power to the ACMP.
The ELMS uses time delays of 1.125 seconds between ACMP starts to protect the electrical system from overload.
ELMS Load Shed
The ELMS sheds one or two of the ACMPs during some conditions.
On a single 90 kVA ground power source, the ELMS may shed ACMP C2. For this condition, the ELMS also may shed the left ACMP during engine start.
On a single 120 kVA airplane power source, the ELMS may shed ACMP C2 during fuel jettison when all ACMPs are ON.
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MAIN HYDRAULIC SYSTEMS -LEFT AND RIGHT SYSTEMS -FUNCTIONAL DESCRIPTION
General
The left and right hydraulic systems are functionally the same.
The left hydraulic system supplies pressurized hydraulic fluid to operate the left thrust reverser and the PFCS. The right hydraulic system supplies pressurized hydraulic fluid to operate the right thrust reverser, the PFCS, and the normal brake system.
Fluid Supply
The hydraulic system reservoirs contain the hydraulic fluid supply for the hydraulic pumps.
A reservoir pressurization module supplies pressurized air from the pneumatic system to pressurize the reservoir.
The reservoir supplies fluid to the EDP through a standpipe. The ACMP gets fluid from the bottom of the reservoir.
Pressurization
The EDPs are the primary pumps for the left and right hydraulic systems. The EDPs get reservoir fluid through the EDP supply shutoff valves.
The EDPs operates whenever the engines operate. A solenoid valve in each EDP controls the pressurization and depressurization of the pump.
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The ACMPs are the demand pumps for the left and right hydraulic systems. The ACMPs normally operate only when there is high hydraulic system demand.
Filtration
Pressure and case drain filter modules clean the pressure flows and the case drain flows of the hydraulic pumps.
A return filter module cleans the return flow of hydraulic fluid from the user systems. The module can be bypassed if the filter clogs.
The heat exchanger cools the hydraulic fluid from ACMP and EDP case drain lines before the fluid goes back to the reservoir.
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