EFFECTIVITY
BEJ ALL
Normal Operation
The signal to operate the ADP assembly comes from the HYDIM cards when the selector is in the AUTO position or from the ADP selector when the selector is in the ON position. These signals go to the LSCU.
The LSCU energizes either the auto run or continuous run coil in the MSOV. This permits air to go to the MSOV pneumatic actuator.
The actuator opens the butterfly valve and air goes through the open VIGVs to turn the turbine.
Speed Control
The ADP assembly has primary and secondary speed control circuits.
The LSCU contains the primary speed control. A monopole speed sensor on the gearbox sends ADP speed signals to the LSCU. The primary speed control circuits control the pneumatic actuator for the VIGVs. The actuator moves the VIGVs through the unison ring. This keeps the turbine within 2.5 percent of the normal operating speed. Normal turbine speed is approximately 32,000 RPM. Normal pump speed is 4315 RPM.
An LVDT supplies actuator position feedback to the LSCU.
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MAIN HYDRAULIC SYSTEMS -ADP ASSEMBLY -FUNCTIONAL DESCRIPTION
The secondary speed control controls the position of the MSOV butterfly valve. The pneumatic speed sensor on the TGA sends a pulsed pneumatic signal in proportion to turbine speed. This signal goes to the secondary speed control fluidic circuit. This pneumatic circuit controls the MSOV pneumatic actuator.
The secondary speed control tries to keep the pump speed approximately 700 RPM higher than the primary speed control. When the system operates on the primary speed control, the secondary speed control gets an underspeed input and keeps the MSOV fully open.
If the primary speed control fails and the speed starts to increase, the MSOV starts to close to keep the pump speed at approximately 5000 RPM.
Reserve Mode
A reserve mode lets the turbine turn at a higher speed to operate the pump at 5160 RPM. This increases pump output for autoslat operation when only one ADP can operate. The HYDIM card commands reserve mode operation for 8 seconds.
For reserve mode operation, the LSCU resets the primary speed control circuit to operate the turbine at the higher RPM. The primary speed control uses the monopole speed sensor input to control the VIGVs. To operate at this higher speed, the secondary speed control must be stopped. The LSCU sends a signal to energize the solenoid in the primary reserve solenoid valve. The valve closes and blocks the pulsed pneumatic signal from the pneumatic speed sensor. Without a speed input, the secondary speed control fluidic circuit does not operate and the butterfly valve in the MSOV fully opens.
Overspeed Protection
Overspeed protection keeps the ADP assembly from turning too fast.
A second monopole speed sensor on the gearbox supplies a speed signal to the LSCU. If the pump speed is more than 6590 RPM, the LSCU opens the control circuits through the overspeed latch. This removes the power from the solenoid in the MSOV and closes the butterfly valve.
Training Information Point
A containment ring protects the airplane from a turbine failure.
The overspeed shutdown system has a latching function that keeps the ADP off until it is reset by a MAT test.
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MAIN HYDRAULIC SYSTEMS -ADP ASSEMBLY -FUNCTIONAL DESCRIPTION
EFFECTIVITY BEJ ALL 29-10-00
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D633W101-BEJ Sep 05/2002
MAIN HYDRAULIC SYSTEMS -ADU HEATERS
Purpose
The air drive unit (ADU) heaters keep the speed control components of the ADU warm to prevent icing. This increases the ADP reliability after being cold-soaked. The ADU is made of the turbine gearbox assembly (TGA) and the modulating shutoff valve (MSOV).
Physical Description
Each ADU has an electric heater assembly. Each heater assembly has four heater elements. The heater elements warm these parts of the ADU:
*
MSOV pneumatic actuator
*
VIGV electro-pneumatic servo valve
*
Secondary speed control assembly
*
MSOV solenoid.
The four heater elements are wired in series.
Location
You get access to the ADUs through the ADP access door. The ADU heaters are on the aft part of the ADP assemblies.
Indications
There is no indication that the ADU heaters are on.
The AIMS shows the status message HYD PUMP DEM C1 or HYD PUMP DEM C2 if there is a failure in an ADU heater element.
Training Information Point
Each ADU heater assembly is an LRU.
You can do a test of the two ADU heaters with the HEATERS operational test. You can also do a test of each of the heaters with the ADP C1 or ADP C2 operational tests.
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