A. Description of the System. The VBV actuation system provides an angular output through fuel gear motor assembly, master ballscrew actuator assembly and 11 ballscrew actuator assemblies. The system is interconnected by 11 flexible shaft assemblies. Eleven ferrules are installed in the engine struts to provide support for the flexible shaft assemblies. The system is designed to open, close, or modulate the 12 VBV doors to an
R intermediate position in response to an input command signal. The VBVs
R remain fully synchronized throughout their complete stroke by the continuous mechanical flexible shaft arrangement. High pressure fuel hydraulically activates the VBV actuation system. The VBV position sensor provides VBV position bias to the ECU. The master ballscrew actuator assembly is connected by a push-pull feedback rod to the VBV position sensor.
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Variable Bleed Valve System
Figure 001
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Air Circulation
Figure 002
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Functional Diagram of the Variable Bleed Valve System
Figure 003
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B. Operation of the System
The system performs 4 primary functions :
(1) Positions the bleed valves in response to a differential fuel pressure through the motor of the fuel gear motor assembly.
(2) Mechanically synchronizes the 12 bleed valves throughout the stroke.
(3) Limits the bleed valve position at the end of each stroke.
(4) Provides the feedback of the VBV position sensor (RDVT) to the ECU.
C. Modulating Operation The motor, actuated by the HMU, drives the system to the commanded position with the required power. The pressure across the motor is reduced as the system approaches the commanded position. The electrical position feedback to the ECU directs the fuel control valve to its null position or minimum opening needed to neutralize the bleed valve loads.
D. End-of-Stroke Operation
(1) Bleed valves closing. The feedback electrical mechanism relays the bleed valve position to the ECU as the system approaches the commanded closed ECU position. The fuel control valve is moved towards the null position as the bleed valve approaches the end of its stroke. This reduces motor
R speed and allows the motor to engage the end-of-stroke stops at a low
R impact force. The closed bleed valve position is within 0.3 percent of the stroke of the ballscrew actuator assembly utilizing the mechanical stops.
(2) Bleed valves opening The feedback electrical mechanism relays the bleed valve position to the ECU as the system approaches the commanded open position. The fuel control valve is positioned to decelerate the motor.
R The same type of mechanical stops is used at the opening end of the R stroke. The open bleed valve position is within one percent of the R stroke of the ballscrew actuator assembly utilizing the mechanical R stops. All 12 bleed valves are mechanically synchronized.
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3. Component Description
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A. Main Flexible Shaft Assembly
(Ref. Fig. 004)
(1) Description. The main flexible shaft assembly is an unshielded power core which has a hexagon fitting on one end and a splined end fitting on the other.
B. Flexible Shaft Assemblies.
(Ref. Fig. 004)
(1) Description The flexible shaft assembly is an unshielded power core which has a hexagon fitting on one end and an 8-point fitting on the other. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：A320飞机维护手册 AMM AIR 空气(36)
