DOC AIRBUS | AMM A320FVARIABLE STATOR VANE (VSV) SYSTEM - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
1. Component Location
** ON A/C NOT FOR ALL 
Air System (LPC Stator Vane Actuator)- The HPC Stator Vane Actuator (SVA) primary unit is mounted on the HPC case on the right side of the engine at approximately the 2 o'clock engine position.
- The HPC SVA secondary unit is attached to the HPC and mounted on the HPC case located at the 7 o'clock engine position.
- The LPC SVA is located at approximately the 9 o'clock position.
| FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C NOT FOR ALL | |||||
| 4052KS | PRIMARY ACTUATOR-HPC STATOR VANE | 400 | 73-21-68 | ||
| 4053KS | ACTUATOR - HPC STATOR VANE, SECONDARY | 400 | 73-11-00 | ||
| 4054KS | ACTUATOR - LPC STATOR VANE | 400 | 73-11-00 | ||
2. System Description
A. VSV System
(1) The VSV system is used to adjust the position of the HPC and LPC variable stator vanes during engine operation to optimize engine performance.
(2) The system consists of an HPC primary (master) SVA unit, an HPC secondary (slave) SVA unit and an LPC SVA unit which are controlled by the Electronic Engine Control (EEC).
(3) The function of the HPC master and slave SVAs is to position the HPC Variable Inlet Guide Vanes (VIGVs), 1st, 2nd and 3rd stage vanes for the HPC.
(a) The HPC master and slave SVAs are fuel-actuated and control the position of the HPC variable stator vanes.
(b) The EEC controls the master SVA piston position through a dual channel torque motor which directs pressurized fuel to the actuator piston.
(c) The position of the HPC master SVA piston rod is sensed by a temperature-compensated single channel Linear Voltage Differential Transducer (LVDT). The LVDT is used to send the piston position to channel A of the EEC.
(d) The position of the HPC slave SVA piston rod is sensed by a temperature-compensated single channel LVDT. The LVDT is used to send the piston position to channel B of the EEC.
(e) The EEC can use the piston position of the HPC master SVA piston rod or the HPC slave SVA piston rod to control the system.
(f) If there is a power failure to the master SVA, the actuator puts the vanes in the open position for maximum airflow through the HPC.
(g) Vanes are scheduled based on the N2 (Core) correct speed.
(h) The HPC variable stator vanes are usually closed during engine start-up and at engine idle, and open during aircraft takeoff.
(i) The HPC SVA piston changes the position of the variable stator vanes through a bell crank and linkages.
(4) The function of the LPC SVA is to position the LPC stator vanes through the LPC VIGV linkage.
(a) The LPC SVA is fuel-actuated.
(b) The VIGVs, which are the first stator stage of the LPC (the LPC has three stages), are variable and are put in position by the SVA.
(c) The position of the LPC SVA piston rod is sensed by a temperature-compensated dual coil LVDT. The LVDT is used to send the piston position to the EEC. If there is a power failure to the SVA, the actuator puts the vanes in the open position for maximum airflow through the LPC.
(d) The LPC SVA piston changes the position of the variable stator vanes through a bell crank and linkages.
(e) Vanes are scheduled based on the N1 (LPC) correct speed.
(f) Usually, the LPC variable inlet guide vanes are open during aircraft takeoff and closed during engine start-up and at engine idle.