DOC AIRBUS | AMM A320FVARIABLE STATOR VANE (VSV) SYSTEM - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The Variable-Stator-Vane (VSV) actuation system consists of 2 VSV hydraulic actuators with dual independent Linear Variable Differential Transducers (LVDT) for position feedback, and 2 actuation mechanisms and linkages. Fuel pressure from the Hydromechanical Unit (HMU) is the hydraulic medium used to operate the VSV actuators.
** ON A/C NOT FOR ALL The Variable-Stator-Vane (VSV) actuation system consists of 2 VSV hydraulic actuators with dual independent Linear Variable Differential Transducers (LVDT) for position feedback, and 2 actuation mechanisms and linkages. Fuel pressure from the Hydromechanical Unit (HMU) is the hydraulic medium used to operate the VSV actuators.
2. Component Location
** ON A/C NOT FOR ALL 
VSV Actuator and Sensor Location (Right Side Shown)| ------------------------------------------------------------------------------- |
| FIN ! FUNCTIONAL DESIGNATION ! PANEL!ZONE!ACCESS ! ATA |
| ! ! ! ! DOOR ! REF. |
| ------------------------------------------------------------------------------- |
| - ACTUATOR AND SENSOR, VSV 75-32-10 |
3. Description
The VSV system positions the compressor variable vanes (IGV through stage 3) to the angles necessary to provide optimum compressor efficiency at steady state and provide adequate stall margin for transient engine operation.
Stator vane angle is a function of core engine speed (N2) and compressor inlet temperature (T25).
The Electronic Control Unit (ECU) schedules the VSV's by controlling the VSV actuation-valve torque motor in the HMU. The HMU ports high pressure fuel to the rod end or head end of the VSV actuators and vents the other end to bypass pressure. The LVDT transmits a feedback signal of the actual vane position to the ECU for comparison with the scheduled position.
Each VSV actuator is connected through a clevis link and the stage 3 bellcrank to a master rod. Linkages connect the variable vane actuation rings to bellcranks that are connected to the master rod.
Connections between the actuator, clevis links, and master rod are made with bolts and bushings for stability. All other linkages are connected with bolts and uniballs to eliminate misalignment or binding.
The actuation rings, which are connected at the horizontal split-line of the compressor casing, rotate circumferentially about the horizontal axis of the compressor. Movement of the rings is transmitted to the individual vanes through vane actuating levers.
** ON A/C NOT FOR ALL The VSV system positions the compressor variable vanes (IGV through stage 3) to the angles necessary to provide optimum compressor efficiency at steady state and provide adequate stall margin for transient engine operation.
Stator vane angle is a function of core engine speed (N2) and compressor inlet temperature (T25).
The Electronic Control Unit (ECU) schedules the VSV's by controlling the VSV actuation-valve torque motor in the HMU. The HMU ports high pressure fuel to the rod end or head end of the VSV actuators and vents the other end to bypass pressure. The LVDT transmits a feedback signal of the actual vane position to the ECU for comparison with the scheduled position.
Each VSV actuator is connected through a clevis link and the stage 3 bellcrank to a master rod. Linkages connect the variable vane actuation rings to bellcranks that are connected to the master rod.
Connections between the actuator, clevis links, and master rod are made with bolts and bushings for stability. All other linkages are connected with bolts and uniballs to eliminate misalignment or binding.
The actuation rings, which are connected at the horizontal split-line of the compressor casing, rotate circumferentially about the horizontal axis of the compressor. Movement of the rings is transmitted to the individual vanes through vane actuating levers.
4. Variable Stator Vane Actuator
A. General
The Variable-Stator-Vane (VSV) actuator provides an output force and motion to the variable stator system in response to fuel pressures from the hydromechanical unit. The VSV actuators are mounted on the high-pressure compressor-stator case at the 2 and 8 o'clock positions.
The Variable-Stator-Vane (VSV) actuator provides an output force and motion to the variable stator system in response to fuel pressures from the hydromechanical unit. The VSV actuators are mounted on the high-pressure compressor-stator case at the 2 and 8 o'clock positions.
B. Description
The VSV actuator is a single ended, uncushioned hydraulic cylinder capable capable of applying force in both extend and retract directions using high pressure fuel. The fuel to air rod seal is a dual-stage seal with a drain port to carry away fuel which passes the first stage of the seal. Piston stroke is controlled by internal stops. The piston incorporates a capped, preformed packing to prevent cross piston leakage. A wiper is provided to ensure that the piston rod is dirt free as it moves through the dual-stage seal.
Each actuator contains one independent Linear Variable Differential Transformer (LVDT) for position indication.
Each LVDT consists of three windings: one excitation and two secondary. The movable winding translates with the actuator rod and the resulting voltage is a function of actuator stroke/VSV position. Excitation is provided by the electronic control unit.
The VSV actuator is a single ended, uncushioned hydraulic cylinder capable capable of applying force in both extend and retract directions using high pressure fuel. The fuel to air rod seal is a dual-stage seal with a drain port to carry away fuel which passes the first stage of the seal. Piston stroke is controlled by internal stops. The piston incorporates a capped, preformed packing to prevent cross piston leakage. A wiper is provided to ensure that the piston rod is dirt free as it moves through the dual-stage seal.
Each actuator contains one independent Linear Variable Differential Transformer (LVDT) for position indication.
Each LVDT consists of three windings: one excitation and two secondary. The movable winding translates with the actuator rod and the resulting voltage is a function of actuator stroke/VSV position. Excitation is provided by the electronic control unit.
C. Operation
The VSV actuator drives the VSV linkage assembly to the stator angle calculated by the ECU, through the HMU. The HMU torque motor ports fuel through the rod or head parts respectively to close or open the vanes or hold their position by pressure balancing the actuator piston.
The VSV actuator drives the VSV linkage assembly to the stator angle calculated by the ECU, through the HMU. The HMU torque motor ports fuel through the rod or head parts respectively to close or open the vanes or hold their position by pressure balancing the actuator piston.
5. VSV Position Feedback Transducer
A. General
The VSV position sensor is a Linear Variable Differential Transducer (LVDT). It is contained in the actuator. It is electrically supplied with 7.07 volts, RMS, 3000 hertz by the ECU. The ECU compares the feedback signal to the scheduled value and modulates the control signal sent to HMU torque motor to maintain the VSV actuator position in agreement with the schedule.
The VSV position sensor is a Linear Variable Differential Transducer (LVDT). It is contained in the actuator. It is electrically supplied with 7.07 volts, RMS, 3000 hertz by the ECU. The ECU compares the feedback signal to the scheduled value and modulates the control signal sent to HMU torque motor to maintain the VSV actuator position in agreement with the schedule.
B. Description
Each LVDT consists of two windings. A movable actuator rod within the LVDT creates a voltage corresponding to the actuator stroke/VSV position.
Excitation is provided by the electronic control unit.
Each LVDT consists of two windings. A movable actuator rod within the LVDT creates a voltage corresponding to the actuator stroke/VSV position.
Excitation is provided by the electronic control unit.