DOC AIRBUS | AMM A320FSTARTING - DESCRIPTION AND OPERATION
** ON A/C NOT FOR ALL
** ON A/C NOT FOR ALL
1. General
The starter motor rotates and accelerates the rotor of the APU to 50 % (above 20,000 ft at 58%) of the APU's normal speed. You operate the starting system from the APU panel in the cockpit. The Electronic Control Box (ECB) 59KD controls the start sequence of the APU. Three consecutive start attempts are permitted without cooldown. After the third start attempt the starter motor must cool down for at least 60 minutes.
** ON A/C NOT FOR ALL The starter motor rotates and accelerates the rotor of the APU to 50 % (above 20,000 ft at 58%) of the APU's normal speed. You operate the starting system from the APU panel in the cockpit. The Electronic Control Box (ECB) 59KD controls the start sequence of the APU. Three consecutive start attempts are permitted without cooldown. After the third start attempt the starter motor must cool down for at least 60 minutes.
2. Component Location
** ON A/C NOT FOR ALL 
Starting System - Component Location| FIN | FUNCTIONAL DESIGNATION | PANEL | ZONE | ACCESS DOOR | ATA REF |
|---|---|---|---|---|---|
| ** ON A/C NOT FOR ALL | |||||
| 2KA | P/BSW-APU/START | 25VU | 210 | 49-42-00 | |
| 5KA | CONTACTOR-MAIN START | 120VU | 212 | 49-42-55 | |
| 6KA | FUSE-APU START | 120VU | 212 | 49-42-00 | |
| 8KA | MOTOR-STARTER | 315 | 49-42-51 | ||
| 10KA | CONTACTOR-BACK-UP START | 120VU | 212 | 49-42-55 | |
3. System Description
The primary parts of the starting system are:
The starter motor turns the APU main shaft through the starter clutch module and the gearbox. At 50% APU speed (above 20,000 ft at 58%) the ECB disengages the starter motor. The starter clutch module disengages mechanically when the self sustained APU speed is more than the starter motor speed. The timed acceleration logic of the ECB controls the APU acceleration during the APU start.
The starter motor has a brush wear indicator to show if the brushes inside the motor are serviceable.
** ON A/C NOT FOR ALL The primary parts of the starting system are:
- the starter motor,
- the starter clutch module,
- the start contactor,
- the back-up start contactor,
- the ECB.
The starter motor turns the APU main shaft through the starter clutch module and the gearbox. At 50% APU speed (above 20,000 ft at 58%) the ECB disengages the starter motor. The starter clutch module disengages mechanically when the self sustained APU speed is more than the starter motor speed. The timed acceleration logic of the ECB controls the APU acceleration during the APU start.
The starter motor has a brush wear indicator to show if the brushes inside the motor are serviceable.
4. Power Supply
The starting system gets the electrical power from the DC system of the aircraft. It supplies 28VDC from the BAT BUS 3PP through a fuse (6KA) and the start contactors to the starter motor (8KA).
** ON A/C NOT FOR ALL The starting system gets the electrical power from the DC system of the aircraft. It supplies 28VDC from the BAT BUS 3PP through a fuse (6KA) and the start contactors to the starter motor (8KA).
5. Interface
The starting system has an interface with:
** ON A/C NOT FOR ALL The starting system has an interface with:
- the DC Generation System (Ref. AMM D/O 24-30-00-00),
- the Control and Monitoring System (Ref. AMM D/O 49-61-00-00).
A. Starter Motor FIN: 8-KA
The starter motor is a series-wound DC motor. A V-clamp attaches the starter motor to the accessory drive gearbox. The motor drive spline-shaft engages with the splined shaft of the starter clutch module. The motor is totally enclosed and has overspeed protection. The electrical terminals of the motor are insulated.
The motor includes a brush wear indicator which you can see in a clear plastic cover. When the indicator is shown, the brushes are serviceable. When the indicator pin is not seen you have to replace the starter motor.
To manually turn the APU, a square end is installed on the shaft of the starter motor. A cap is fitted to protect the drive shaft.
The starter motor is a series-wound DC motor. A V-clamp attaches the starter motor to the accessory drive gearbox. The motor drive spline-shaft engages with the splined shaft of the starter clutch module. The motor is totally enclosed and has overspeed protection. The electrical terminals of the motor are insulated.
The motor includes a brush wear indicator which you can see in a clear plastic cover. When the indicator is shown, the brushes are serviceable. When the indicator pin is not seen you have to replace the starter motor.
To manually turn the APU, a square end is installed on the shaft of the starter motor. A cap is fitted to protect the drive shaft.
B. Starter Clutch Module
Between the starter motor and the accessory drive gearbox there is a starter clutch which makes the mechanical connection. Bolts attach the starter clutch module to the accessory drive gearbox. The clutch module has an inner splined shaft and an outer starter gear, which has a hollow shaft. Between the two shafts are the spring loaded sprags.
Between the starter motor and the accessory drive gearbox there is a starter clutch which makes the mechanical connection. Bolts attach the starter clutch module to the accessory drive gearbox. The clutch module has an inner splined shaft and an outer starter gear, which has a hollow shaft. Between the two shafts are the spring loaded sprags.
(1) When the starter motor begins to turn, the friction locks the sprags between the races of the splined shaft and the starter gear shaft. The starter motor drives the starter gear through the clutch module.
(2) During the start, the sprags engage between the splined shaft and the starter gear. When the starter motor is de-energized the motor speed decreases. The starter gear shaft (now driven from the gearbox) turns with a higher speed than the splined shaft of the clutch module. The sprags then disengage.
C. Start Switch
The START switch 2KA is a non latching ON/OFF pushbutton switch. A blue colored ON legend comes on when the APU is started. A green colored AVAIL legend comes on when the APU is ready to supply electrical power or pneumatic power to the aircraft systems.
The START switch 2KA is a non latching ON/OFF pushbutton switch. A blue colored ON legend comes on when the APU is started. A green colored AVAIL legend comes on when the APU is ready to supply electrical power or pneumatic power to the aircraft systems.
D. Start Contactor and Backup Start Contactor
The start contactor 5KA and the backup start contactor 10KA are installed on rack 120VU, rear of the cockpit. These two switches are heavy duty contactors that switch electrical current to the starter motor 8KA.
The start contactor 5KA and the backup start contactor 10KA are installed on rack 120VU, rear of the cockpit. These two switches are heavy duty contactors that switch electrical current to the starter motor 8KA.
7. Operation/Control and Indicating
When you put the MASTER SW pushbutton switch in the ON position:
When you put the MASTER SW pushbutton switch in the ON position:
- the main relay 4KD is energized,
- the ECB starts the power-up test,
- the APU fuel pump system is energized,
- the APU air inlet door opens,
- the ON legend in the START pushbutton switch comes on,
- the ECB energizes the back-up start contactor 10KA and (1.5 seconds later) the start contactor 5KA, when these conditions are met:
.the air intake is open,
.the Power-Up Test (PUT) is complete,
.the speed is less then 7 %,
.an automatic shutdown is not detected,
.a commanded shutdown (MASTER SW to off) is not selected.
.the data exchange between the Data Memory Module (DMM) and the ECB has been accomplished (approx. 15 seconds). - the contactors energize the starter motor 8KA with 28 V DC and the APU starter motor starts to turn. The starter clutch engages and turns the APU main shaft,
- together with the back-up start contactor the igniter is energized,
- the de-oil valve opens (if oil temp is below 20 deg F, 6.6 deg C or fuel temp below 10 deg F, -12.2 deg C or altitude above 20,000 ft ).
- the APU operation data is shown on the lower ECAM display unit.
NOTE: During Ram Air Turbine (RAT) extension, APU starting is inhibited by the Battery Charge Limiters (BCL 1 and BCL 2), which prevent operation of the main start contactor 5 KA for 45s.
At 7% speed, the ECB: - opens the fuel shutoff solenoid valve in the fuel control unit,
- controls the fuel flow to the APU with the start acceleration control logic.
- the IGVs close.
- de-energizes the start contactor 5KA (above 20,000 ft at 58%) which switches off the starter motor 8KA and the ECB accelerates the APU automatically,
- de-energizes the back-up start contactor 10KA, after 5 seconds.
- de-energizes the ignition unit,
- de-energizes the de-oil solenoid (if opened).
- the ECB controls and monitors the APU automatically,
- the green AVAIL legend in the START pushbutton switch comes on,
- the blue ON legend in the START pushbutton switch goes off.
- the APU bleed valve is ready for operation,
- the APU generator is ready for operation.