DOC AIRBUS | AMM A320FLOAD COMPRESSOR - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The single-stage load compressor is driven directly from the power section.
It supplies compressed air (bleed air) to the aircraft pneumatic system.
** ON A/C NOT FOR ALL The single-stage load compressor is driven directly from the power section.
It supplies compressed air (bleed air) to the aircraft pneumatic system.
2. Component Location
** ON A/C NOT FOR ALL 
APU Load Compressor| ------------------------------------------------------------------------------- |
| FIN | FUNCTIONAL DESIGNATION | PANEL|ZONE|ACCESS | ATA |
| | | | | DOOR | REF. |
| ------------------------------------------------------------------------------- |
| 8014KM ACTUATOR - INLET GUIDE VANE 316 316AR 49-23-51 |
3. System Description
The machined titanium single-stage centrifugal impeller is attached to the single main shaft of the engine. A curvic coupling transmits the drive torque from the engine to the centrifugal impeller. The load compressor bearing cavities are kept dry to prevent oil churning and prevent seal leakage. The load compressor bearing cavities drain into the gearbox. Two air bufferred main shaft seals are used to seal the load compressor bearing cavities. The bellows carbon face seal is used to provide the lowest air leakage to minimise oil consumption. This face seal is air buffered with air from the secondary flow system. This maintains a positive differential across the seal under all operating conditions.
The bellows carbon face seal along with the buffer air system has high reliability in preventing oil in the bleed system even with a worn seal. An oil leak witness drain is located aft of the seal to collect any oil leakage. This prevents oil in the bleed system and indicates a degraded seal performance. To aid in long seal life and prevent coking the seal rotor is cooled with oil from the hydraulic mount discharge.
** ON A/C NOT FOR ALL The machined titanium single-stage centrifugal impeller is attached to the single main shaft of the engine. A curvic coupling transmits the drive torque from the engine to the centrifugal impeller. The load compressor bearing cavities are kept dry to prevent oil churning and prevent seal leakage. The load compressor bearing cavities drain into the gearbox. Two air bufferred main shaft seals are used to seal the load compressor bearing cavities. The bellows carbon face seal is used to provide the lowest air leakage to minimise oil consumption. This face seal is air buffered with air from the secondary flow system. This maintains a positive differential across the seal under all operating conditions.
The bellows carbon face seal along with the buffer air system has high reliability in preventing oil in the bleed system even with a worn seal. An oil leak witness drain is located aft of the seal to collect any oil leakage. This prevents oil in the bleed system and indicates a degraded seal performance. To aid in long seal life and prevent coking the seal rotor is cooled with oil from the hydraulic mount discharge.
A. Variable Inlet Guide-Vane (IGV)
The IGV assembly has 16 IGVs. They are installed radially at the load compressor inlet.
The IGV assembly has 16 IGVs. They are installed radially at the load compressor inlet.
B. The IGV Actuator
The IGV actuator is the hydromechanical servo mechanism which controls the opening angle of the IGVs.
The IGVA consists of:-
The power piston has a 25.4 mm (1 inch) stroke and develops up to 107 daN (240.5455 lbf) force to move the IGVs rapidly to control the APU. This is essential in case of sudden mechanical overload and the APU must unlaod quickly.
The LVDT is a 5 wire device excited by signals from the ECB. it has primary and secondary windings and a movable ferous core. Shaft movement changes induction between the windings and therefore allows metered fuel to move the spool valve. This movement will cause the IGVA power piston to move and change the angle of the IGVs through the gear ring.
The ECB monitors the IGV actuator operation.
The IGV actuator is the hydromechanical servo mechanism which controls the opening angle of the IGVs.
The IGVA consists of:-
- a two stage hydraulic servo control valve,
- a power piston,
- a linear variable differential transformer.
The power piston has a 25.4 mm (1 inch) stroke and develops up to 107 daN (240.5455 lbf) force to move the IGVs rapidly to control the APU. This is essential in case of sudden mechanical overload and the APU must unlaod quickly.
The LVDT is a 5 wire device excited by signals from the ECB. it has primary and secondary windings and a movable ferous core. Shaft movement changes induction between the windings and therefore allows metered fuel to move the spool valve. This movement will cause the IGVA power piston to move and change the angle of the IGVs through the gear ring.
The ECB monitors the IGV actuator operation.
5. Operation/Control and Indicating
The adjustable IGVs control the load compressor airflow (output) for the necessary input to the aircraft system (Ref. AMM D/O 49-51-00-00). The aircraft system transmits a demand signal to the Electronic Control Box (ECB) 59KD to give the necessary IGV control.
During the start sequence, fuel pressure is used to keep the hydraulic (fuel) servo actuator at the fully extended position and the IGVs closed (15 degrees). This makes sure that:
The adjustable IGVs control the load compressor airflow (output) for the necessary input to the aircraft system (Ref. AMM D/O 49-51-00-00). The aircraft system transmits a demand signal to the Electronic Control Box (ECB) 59KD to give the necessary IGV control.
During the start sequence, fuel pressure is used to keep the hydraulic (fuel) servo actuator at the fully extended position and the IGVs closed (15 degrees). This makes sure that:
- there is minimum airflow through the compressor,
- during acceleration, the shaft load on the APU engine is kept to a minimum.