DOC AIRBUS | AMM A320FENGINE - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The APU supplies:
** ON A/C NOT FOR ALL The APU supplies:
- pneumatic power for 'Main Engine Start (MES)',
- pneumatic power for the environmental control system (ECS),
- mechanical shaft power to drive an AC generator and a fan. The fan, an integral part of the APU, cools its lubrication system and the APU compartment.
2. System Description
The power unit has three basic modules:
The power unit has three basic modules:
Auxilliary Power Unit- a power section,
- a load compressor,
- an accessory gearbox.
A. Power Section
The power section supplies shaft power to drive a load compressor, a gearbox with accessories and an electrical generator. It is a single-shaft assembly with a single-stage, machined-titanium centrifugal-compressor with a 8:1 pressure ratio. It also includes a reverse-flow annular-combustion chamber and a two-stage axial-flow turbine (Ref. AMM D/O 49-21-00-00).
The power section supplies shaft power to drive a load compressor, a gearbox with accessories and an electrical generator. It is a single-shaft assembly with a single-stage, machined-titanium centrifugal-compressor with a 8:1 pressure ratio. It also includes a reverse-flow annular-combustion chamber and a two-stage axial-flow turbine (Ref. AMM D/O 49-21-00-00).
B. Load Compressor
The load compressor is a direct-drive modular assembly, installed between the power section and the accessory gearbox. It is a single-stage centrifugal compressor. Inlet Guide Vanes (IGVs) are installed at the entrance of the compressor housing to control the compressor output to the aircraft system (Ref. AMM D/O 49-23-00-00).
The load compressor is a direct-drive modular assembly, installed between the power section and the accessory gearbox. It is a single-stage centrifugal compressor. Inlet Guide Vanes (IGVs) are installed at the entrance of the compressor housing to control the compressor output to the aircraft system (Ref. AMM D/O 49-23-00-00).
C. Accessory Gearbox
The accessory gearbox is installed on the front face of the load compressor casing and is driven by the power section.
The accessory gearbox (Ref. AMM D/O 49-26-00-00) has drive pads for:
The accessory gearbox is installed on the front face of the load compressor casing and is driven by the power section.
The accessory gearbox (Ref. AMM D/O 49-26-00-00) has drive pads for:
- an AC generator,
- a starter motor,
- two oil pumps (pressure and scavenge pump),
- a fuel pump,
- a cool air fan and PMG.
3. Operation/Control and Indicating
The MASTER SW pushbutton switch 14KD and the APU START pushbutton switch 2KA are installed on the panel 25VU in the cockpit. They both control the engine start.
When the MASTER SW 14KD is set to ON, the Electronic Control Box (ECB) 59KD is energized. This causes the ECB to transmit signals that:
At 55% rpm. the ECB de-energizes the starter motor, turns off the exciter and de-energizes the gearbox de-oiling valve. 5 sec. after speed has reached 55% rpm. the backup start contactor is de-energized. The start in progress signal is de-activated, steady state speed control is initiated and run state is entered. When the engine has reached 95% rpm. the surge control system is initiated.
2 sec. later the ECB sends an 'AVAILABLE' signal to the aircraft circuits. The AVAIL legend in the APU START pushbutton switch 2KA comes on. It indicates that the APU is ready to supply bleed air and electrical power to the aircraft systems.
When the APU BLEED pushbutton switch 5HV is set to the ON position, the bleed control valve will open. The APU will then supply bleed air to the pneumatic system. The ECB controls the bleed control valve, which supplies the pneumatic system with bleed air and protects the load compressor from surge. The EGT increases when a selection of pneumatic or electrical load, or both, is made. This is shown on the lower ECAM display unit of the Electronic Centralized Aircraft Monitoring (ECAM). During the start sequence the IGVs are fully closed.
With the engine speed at 95% rpm, +2 sec. the ECB will accept pneumatic and electrical demand signals. It computes the position of the IGVs and supplies the necessary pneumatic flow. The pneumatic and electrical loads together can cause the EGT to increase more than the set temperature limit. If this occurs, the ECB commands the IGVs to move nearer to the closed position from the set position. This reduces the pneumatic load and makes the electrical load the primary load.
When the MASTER SW 14KD is set to the OFF position, a normal APU shutdown starts. The ECB causes the IGVs to move to the closed position and the bleed control valve to the discharge position. The ECB then removes the 'AVAIL' signal to the aircraft circuits. With the pneumatic loads removed and the bleed air supply no longer required, the APU goes into a cool-down cycle for 120 sec. The AVAIL legend in the APU START pushbutton switch 2KA and AVAIL indications on the upper and lower ECAM displays are then turned off.
A decrease in the EGT shows on the APU page of the ECAM. After the cool-down cycle ends, APU speed drops below 95%. The ECB then takes a condition monitoring snapshot and starts the shutdown. The ECB then turns off the fuel valve and fuel servo and turns on the gearbox de-oiling valve.
During the run-down cycle, when the engine speed is below 7% rpm, the ECB closes the air intake flap. Before it de-energizes itself, the ECB updates the nonvolatile memory and signals the aircraft circuits to:
** ON A/C NOT FOR ALL The MASTER SW pushbutton switch 14KD and the APU START pushbutton switch 2KA are installed on the panel 25VU in the cockpit. They both control the engine start.
When the MASTER SW 14KD is set to ON, the Electronic Control Box (ECB) 59KD is energized. This causes the ECB to transmit signals that:
- open the APU air-intake flap,
- open the FUEL LP VALVE 3QF,
- energize the APU fuel-feed pump 4QC.
At 55% rpm. the ECB de-energizes the starter motor, turns off the exciter and de-energizes the gearbox de-oiling valve. 5 sec. after speed has reached 55% rpm. the backup start contactor is de-energized. The start in progress signal is de-activated, steady state speed control is initiated and run state is entered. When the engine has reached 95% rpm. the surge control system is initiated.
2 sec. later the ECB sends an 'AVAILABLE' signal to the aircraft circuits. The AVAIL legend in the APU START pushbutton switch 2KA comes on. It indicates that the APU is ready to supply bleed air and electrical power to the aircraft systems.
When the APU BLEED pushbutton switch 5HV is set to the ON position, the bleed control valve will open. The APU will then supply bleed air to the pneumatic system. The ECB controls the bleed control valve, which supplies the pneumatic system with bleed air and protects the load compressor from surge. The EGT increases when a selection of pneumatic or electrical load, or both, is made. This is shown on the lower ECAM display unit of the Electronic Centralized Aircraft Monitoring (ECAM). During the start sequence the IGVs are fully closed.
With the engine speed at 95% rpm, +2 sec. the ECB will accept pneumatic and electrical demand signals. It computes the position of the IGVs and supplies the necessary pneumatic flow. The pneumatic and electrical loads together can cause the EGT to increase more than the set temperature limit. If this occurs, the ECB commands the IGVs to move nearer to the closed position from the set position. This reduces the pneumatic load and makes the electrical load the primary load.
When the MASTER SW 14KD is set to the OFF position, a normal APU shutdown starts. The ECB causes the IGVs to move to the closed position and the bleed control valve to the discharge position. The ECB then removes the 'AVAIL' signal to the aircraft circuits. With the pneumatic loads removed and the bleed air supply no longer required, the APU goes into a cool-down cycle for 120 sec. The AVAIL legend in the APU START pushbutton switch 2KA and AVAIL indications on the upper and lower ECAM displays are then turned off.
A decrease in the EGT shows on the APU page of the ECAM. After the cool-down cycle ends, APU speed drops below 95%. The ECB then takes a condition monitoring snapshot and starts the shutdown. The ECB then turns off the fuel valve and fuel servo and turns on the gearbox de-oiling valve.
During the run-down cycle, when the engine speed is below 7% rpm, the ECB closes the air intake flap. Before it de-energizes itself, the ECB updates the nonvolatile memory and signals the aircraft circuits to:
- stop the fuel feed pump 4QC,
- close the FUEL LP VALVE 3QF.
The ECB continually monitors the APU operation and protection functions. If necessary, it shuts down the APU or gives a visual indication to the operator. When a malfunction occurs that could cause damage to the engine, the ECB automatically unloads the engine and starts a shutdown. The FAULT legend in the MASTER SW 14KD comes on. It will stay on until the MASTER SW 14KD is released to OFF.
4. Operational Characteristics
A. Operating Limits
(1) Rated combination load at sea level 38 DEG.C (100.4 DEG.F) condition:
| Bleed Load: Bleed flow = 1.07 Kg/s (142 lbs/min), |
| Bleed pressure = 3.33 bar 48.95 psi), |
| Shaft load: 83KW (111.3 shp). |
(2) Maximum EGT limits (which result in a shutdown):
- max. EGT at 100% speed ...............=> 682 DEG.C (1259.6 DEG.F);
- max. EGT during start (below 25000ft) => 900 DEG.C (1652 DEG.F);
- max. EGT during start (above 25000ft) => 982 DEG.C (1799.6 DEG.F).
(3) Generator output shaft speed: - 24034 rpm.
B. Fuel and Fuel Control System
NOTE: This is for general reference only. All fuel types approved in your Flight Crew Operation Manual (FCOM) can be used in the APU.
(1) The fuel inlet minimum pressure is 0.7 bar (10 psi) maximum is 3.8 bar (55.0 psi). 5 psi above true vapour pressure is limited to less than 30 sec.
(2) Fuel inlet temperature from -40 DEG.C (-40 DEG.F) to 54 DEG.C (129.2 DEG.F).
| ------------------------------------------ |
| FUEL SPECIFICATIONS |
| ------------------------------------------ |
| JET A /JET A1 ASTM D 1655 |
| JP 4 MIL T 5624 |
| JET B ASTM D 1655 |
| JP 5 MIL T 5624 |
| JP 8 MIL T 5624 |
| RT GOST 10227 |
| TS-1 GOST 10227 |
(3) Oil and Fuel Leakage limits
| ------------------------------------------------------------------------------- |
| Item Fluid Limits Remarks |
| ------------------------------------------------------------------------------- |
| Forward Drain: l Fuel l Not permitted l Fuel leakage is |
| Combustor and l l during APU l permitted during the |
| Exhaust l l operation. l shutdown of the APU. |
| l l l After a No Light ASD, |
| l l l fuel present in the |
| l l l combustor that did not |
| l l l light off will be |
| l l l drained inducing |
| l l l important over |
| l l l boarding. |
| ------------------------------------------------------------------------------- |
| Centre Drain: l Oil l Some oil mist l |
| Front Bearing l l permitted. l |
| Seal l l No continual l |
| l l drops are l |
| l l permitted l |
| ------------------------------------------------------------------------------ |
| Rear Drain: l Oil l 0.1 cc/mm l Leakage origin on rear |
| FCU Seal l l l drain case can only be |
| l l l seen with APU door open |
| l l l |
| BCV and/or IGV l Fuel l Small wetting l |
| Seals l l of case drain l |
| l l permitted. l |
| l l No drops l |
| l l permitted l |
| ------------------------------------------------------------------------------- |
| Oil Consumption l Oil l 6.5 cc/hr l This oil consumption |
| l l l is only applicable for a |
| l l l new or freshly refurbished |
| l l l engine. It refers to the |
| l l l oil lost inherently during |
| l l l engine operation. |
| ------------------------------------------------------------------------------- |
C. Engine Starter Motor-Duty Cycle
Three consecutive start attempts are permitted without cool-down. After the third start attempt the starter must cool down for at least 60 minutes.
Three consecutive start attempts are permitted without cool-down. After the third start attempt the starter must cool down for at least 60 minutes.
D. Lubrication System
(1) Oil specification - approved lubricants of vendor.
(2) Oil reservoir capacity 6.3 l (1.66 USgal) approximately.
(3) Oil consumption - monitor in accordance with the guideline for the oil consumption in service.
E. Electrical System:
(1) Power supply (aircraft bus) or,
(2) Battery 28.6 +/- 2 V DC.
F. Bleed-Air Control System
(1) Inlet Guide-Vane Actuator - Nonoperating - Closed.
(2) Bleed Control Valve - Nonoperating - Exhaust position.