Installation of the Emergency Power Supply Unit (EPSU)

TASK 33-51-38-400-001-A
Installation of the Emergency Power Supply Unit (EPSU)

FIN: 10WL
FIN: 11WL
FIN: 12WL
FIN: 13WL
FIN: 14WL ** ON A/C NOT FOR ALL
FIN: 15WL ** ON A/C NOT FOR ALL
FIN: 16WL ** ON A/C NOT FOR ALL
FIN: 17WL ** ON A/C NOT FOR ALL

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	STEPLADDER 1.0 M (3.3 FT)
No specific	1	STEPLADDER 1.5 M (5 FT)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
FOR [10WL] (POWER-EMERGENCY SUPPLY)
221BC
FOR [11WL] (EPSU)
251KC
241KW
FOR [12WL] (EPSU)
251KC
242KW
FOR [13WL] (EPSU)
261CC
FOR [14WL] (EPSU)
231JC
FOR [15WL] (EPSU)
231JC
FOR [16WL] (EPSU)
242KW
FOR [17WL] (EPSU)
241KW

C. Referenced Information

REFERENCE	DESIGNATION
TASK 20-28-00-869-002-A	Table of the Maximum Permitted Resistance-Values
TASK 20-28-00-912-802-A	Electrical Bonding - General Maintenance Procedure
TASK 24-41-00-861-002-A	Energize the Aircraft Electrical Circuits from the External Power
TASK 24-41-00-861-002-A-01	Energize the Aircraft Electrical Circuits from the APU
TASK 24-41-00-861-002-A-02	Energize the Aircraft Electrical Circuits from Engine 1(2)
TASK 24-41-00-862-002-A	De-energize the Aircraft Electrical Circuits Supplied from the External Power
TASK 24-41-00-862-002-A-01	De-energize the Aircraft Electrical Circuits Supplied from the APU
TASK 24-41-00-862-002-A-02	De-energize the Aircraft Electrical Circuits Supplied from the Engine 1(2)
TASK 33-51-00-710-001-A	Operational Check of Emergency Power Supply Units by BITE-Check
TASK 33-51-38-000-002-A	Removal of the Battery of the Emergency Power Supply Unit (EPSU)
TASK 33-51-38-400-002-A	Installation of the Battery of the Emergency Power Supply Unit (EPSU)
Emergency Power Supply Unit (EPSU) ** ON A/C NOT FOR ALL
Emergency Power Supply Unit (EPSU) ** ON A/C NOT FOR ALL
Emergency Power Supply Unit (EPSU) ** ON A/C NOT FOR ALL
FOR [10WL] (POWER-EMERGENCY SUPPLY)
TASK 25-23-42-400-001-A	Installation of the Ceiling Panels - Forward Utility Area
FOR [11WL] (EPSU)
TASK 25-23-41-400-001-A	Installation of the Ceiling Panels
TASK 25-23-44-400-001-A	Installation of the Lower Sidewall Panels (Dado Panels)
FOR [12WL] (EPSU)
TASK 25-23-41-400-001-A	Installation of the Ceiling Panels
TASK 25-23-44-400-001-A	Installation of the Lower Sidewall Panels (Dado Panels)
FOR [13WL] (EPSU)
TASK 25-23-42-400-002-A	Installation of the Ceiling Panels - Aft Utility Area
TASK 35-21-41-400-001-A	Installation of the Emergency Oxygen Containers
FOR [14WL] (EPSU)
TASK 25-23-41-400-001-A	Installation of the Ceiling Panels
FOR [15WL] (EPSU)
TASK 25-23-41-400-001-A	Installation of the Ceiling Panels
FOR [16WL] (EPSU)
TASK 25-23-44-400-001-A	Installation of the Lower Sidewall Panels (Dado Panels)
FOR [17WL] (EPSU)
TASK 25-23-44-400-001-A	Installation of the Lower Sidewall Panels (Dado Panels)

3. Job Set-up
Subtask 33-51-38-860-058-A ** ON A/C NOT FOR ALL

A. Aircraft Maintenance Configuration
(1) Make sure that the aircraft electrical circuits are energized.
(Ref. AMM TASK 24-41-00-861-002).
(2) Make sure that the stepladder is in position.
(3) On overhead panel 25VU, make sure that EMER EXIT LT switch 4WL is in the OFF position.
(4) On overhead panel 25VU, make sure that NO SMOKING switch 190RH is in the OFF position.
(5) On Forward Attendant Panel (FAP) 120RH, make sure that the LIGHT EMER pushbutton switch and its integral light are off.

Subtask 33-51-38-860-058-D ** ON A/C NOT FOR ALL

A. Aircraft Maintenance Configuration
(1) Make sure that the aircraft electrical circuits are energized.
(Ref. AMM TASK 24-41-00-861-002).
(2) Make sure that the stepladder is in position.
(3) On overhead panel 25VU, make sure that EMER EXIT LT switch 4WL is in the OFF position.
(4) On overhead panel 25VU, make sure that NO SMOKING switch 190RH is in the OFF position.
(5) On Flight Attendant Panel (FAP) 120RH, make sure that the EMER pushbutton and its internal light are off.

Subtask 33-51-38-860-058-E ** ON A/C NOT FOR ALL

A. Aircraft Maintenance Configuration
(1) Make sure that the aircraft electrical circuits are energized.
(Ref. AMM TASK 24-41-00-861-002).
(2) Make sure that the STEPLADDER 1.0 M (3.3 FT) is in position.
(3) On the overhead panel 25VU, make sure that the EMER EXIT LT switch 4WL is in the OFF position.
(4) On the overhead panel 25VU, make sure that the EXIT switch 190RH is in the OFF position.
(5) On the Flight Attendant Panel (FAP) 120RH, make sure that the EMER button and its light are off.

Subtask 33-51-38-860-058-F ** ON A/C NOT FOR ALL

A. Aircraft Maintenance Configuration
(1) Make sure that the aircraft electrical circuits are energized.
(Ref. AMM TASK 24-41-00-861-002).
(2) Make sure that the STEPLADDER 1.5 M (5 FT) is in position.
(3) On overhead panel 25VU, make sure that EMER EXIT LT switch 4WL is in the OFF position.
(4) On overhead panel 25VU, make sure that No PED switch 190RH is in the OFF position.
(5) On Flight Attendant Panel (FAP) 120RH, make sure that the EMER button and its light are off.

Subtask 33-51-38-865-051-A

B. Make sure that this(these) circuit breaker(s) is(are) open, safetied and tagged:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
49VU	LIGHTING/EMER LT/CABIN	2WL	H06
49VU	LIGHTING/EMER LT/CABIN	1WL	H05
** ON A/C NOT FOR ALL
49VU	LIGHTING/EMER LT/CABIN	2WL	H04
49VU	LIGHTING/EMER LT/CABIN	1WL	H03
** ON A/C ALL
122VU	LIGHTING/CABIN/EMER/LT	3WL	V07

4. Procedure

CAUTION: BEFORE YOU INSTALL THE BATTERY, MAKE SURE THAT THE SPACER PLATE IS REMOVED. IF YOU INSTALL THE BATTERY WITH THE SPACER PLATE, THE EMERGENCY LIGHT WILL NOT OPERATE IN EMERGENCY CONDITIONS.

Subtask 33-51-38-910-052-A

A. Preparation for Installation
(1) Clean the component interfaces and the adjacent area.
(2) Do an inspection of the component interfaces and the adjacent area.
(3) Make sure that the parts retained from the removed component are clean and in the correct condition.
(4) Make sure that the ground bonding point of the EPSU housing is clean and free from corrosion.
(5) If necessary, remove the battery (5) from the EPSU (1) (Ref. AMM TASK 33-51-38-000-002).

Subtask 33-51-38-420-050-A

B. Installation of the Emergency Power Supply Unit (EPSU)
(1) If removed, install the battery (5) on the EPSU (1) (Ref. AMM TASK 33-51-38-400-002).
(2) Put the EPSU (1) in the position.
(3) Install the screws (3) and the washers (4) from the EPSU (1).
(4) Prepare for the bonding check on the applicable screws (3) (Ref. AMM TASK 20-28-00-912-802).
(5) Do a check of the maximum bonding value on the applicable screws (3) (Ref. AMM TASK 20-28-00-869-002).
(6) Remove the CAP-BLANKING from each electrical connector and receptacle.

CAUTION: MAKE SURE THAT THE ELECTRICAL CONNECTORS ARE CLEAN BEFORE YOU DISCONNECT OR CONNECT THEM. CONTAMINATION ON THE ELECTRICAL CONNECTORS CAN CAUSE DAMAGE TO EQUIPMENT.

(7) Connect the electrical connector (2) to the EPSU (1).

NOTE: The cable connected to the EPSU (1) has a drip loop in front of the electrical connector.

Subtask 33-51-38-865-054-A

C. Remove the safety clip(s) and the tag(s) and close this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
49VU	LIGHTING/EMER LT/CABIN	2WL	H06
49VU	LIGHTING/EMER LT/CABIN	1WL	H05
** ON A/C NOT FOR ALL
49VU	LIGHTING/EMER LT/CABIN	2WL	H04
49VU	LIGHTING/EMER LT/CABIN	1WL	H03
** ON A/C ALL
122VU	LIGHTING/CABIN/EMER/LT	3WL	V07

Subtask 33-51-38-860-059-A ** ON A/C NOT FOR ALL

D. Preparation for the Test
(1) Make sure that the aircraft electrical circuits are energized.
(Ref. AMM TASK 24-41-00-861-002).
(2) If the EPSU supplies overwing emergency lights, make sure that these overwing emergency lights operate:
(a) Pull down and remove the cover flap from one of the related hatches.

NOTE: The SLIDE ARMED light on the cabin lining at the emergency exits comes on.

(b) Push the latch pin against the spring and turn it a quarter turn counterclockwise to retract it to the DISARMED position.

NOTE: The SLIDE ARMED light goes off.

(c) Make sure that the overwing emergency lights come on.
(d) Push the latch pin against the spring and turn it a quarter turn clockwise to extend it to the ARMED position.

NOTE: The SLIDE ARMED light comes on.

(e) Make sure that the overwing emergency lights go off.
(f) Install and close the removed cover flap on the related hatch.

NOTE: The SLIDE ARMED light goes off.

(3) On overhead panel 25VU, set EMER EXIT LT switch 4WL to the ON position.
(4) Make sure that all the other lights and signs of the emergency lighting system connected to this EPSU are operate correctly.
(5) On overhead panel 25VU, set EMER EXIT LT switch 4WL to the OFF position.

CAUTION: DO NOT USE THE TEACH-IN PROCEDURE TO CLEAR EPSU FAILURE MESSAGES. THE TEACH-IN PROCEDURE IS NOT A SYSTEM RESET. IT CAN CHANGE THE EMERGENCY LIGHT CONFIGURATION AND CAUSE HIDDEN FAILURES.

(6) If it was removed before, carefully put the battery (5) in the EPSU (1) (Ref. AMM TASK 33-51-38-400-002).

NOTE: To measure and keep the load values, the load programming (TEACH IN) of the EPSU starts automatically when:

AC and DC electrical power are available.
On FAP 120RH, LIGHT EMER pushbutton switch and its light are off.
On overhead panel 25VU, EMER EXIT LT switch 4WL is in the OFF position.
On overhead panel 25VU, NO SMOKING switch 190RH is in the OFF position.
The overwing emergency lights are off.
The EPSU (1) is installed on the A/C for the first time.
The battery was removed for more than five seconds and then it is installed again.

The load values are used as reference values during the EPSU SYSTEM TEST. It is necessary to examine that all connected emergency lights of the related EPSU operate.

NOTE: The teach-in procedure of the EPSUs measures and keeps the load values that are related to each EPSU. The EPSU controller refers to these load values when the BITE test of the emergency lighting system operates. Thus, it is necessary that the emergency lights of the related EPSUs operate correctly during the teach-in procedure.

Subtask 33-51-38-860-059-B ** ON A/C NOT FOR ALL

D. Preparation for the Test
(1) Make sure that the aircraft electrical circuits are energized.
(Ref. AMM TASK 24-41-00-861-002).
(2) If the emergency power supply unit supplies overwing emergency lights, make sure that these overwing emergency lights operate:
(a) Pull down and remove the cover flap from one of the related hatches.
(b) Turn the latch pin a quarter turn counterclockwise to retract the latch pin.
(c) Make sure that the overwing emergency lights come on.
(d) Push the retracted latch pin and turn the latch pin a quarter turn clockwise to extend the latch pin.
(e) Make sure that the overwing emergency lights go off.
(f) Install and close the removed cover flap on the related hatch.
(3) On overhead panel 25VU, set EMER EXIT LT switch 4WL to the ON position.
(4) Make sure also that all the other lights and signs of the emergency lighting system connected to this emergency power supply unit are operate correctly.
(5) On overhead panel 25VU, set EMER EXIT LT switch 4WL to the OFF position.

CAUTION: DO NOT USE THE TEACH-IN PROCEDURE TO CLEAR EPSU FAILURE MESSAGES. THE TEACH-IN PROCEDURE IS NOT A SYSTEM RESET. IT CAN CHANGE THE EMERGENCY LIGHT CONFIGURATION AND CAUSE HIDDEN FAILURES.

(6) If it was removed before, carefully put the battery (5) in the EPSU (1) (Ref. AMM TASK 33-51-38-400-002).

NOTE: To measure and keep the load values, the load programming (TEACH IN) of the EPSU starts automatically when:

The AC and the DC power are available
On the FAP 120RH, LIGHT EMER pushbutton switch and its integral light are off
On overhead panel 25VU, EMER EXIT LT switch 4WL is in the OFF position
On the overhead panel 25VU, EXIT switch 190RH is in the OFF position
The overwing emergency lights are off
The emergency power supply unit is installed on the A/C for the first time, or
The battery was removed for more than 5 s and then it is installed again.

The load values are used as reference values during the EPSU SYSTEM TEST. It is necessary to examine that all connected emergency lights of the related EPSU operate.

Subtask 33-51-38-860-059-C ** ON A/C NOT FOR ALL

CAUTION: DO NOT USE THE TEACH-IN PROCEDURE TO CLEAR EPSU FAILURE MESSAGES. THE TEACH-IN PROCEDURE IS NOT A SYSTEM RESET. IT CAN CHANGE THE EMERGENCY LIGHT CONFIGURATION AND CAUSE HIDDEN FAILURES.

(6) If it was removed before, carefully put the battery (5) in the EPSU (1) (Ref. AMM TASK 33-51-38-400-002).

NOTE: To measure and keep the load values, the load programming (TEACH IN) of the EPSU starts automatically when:

The AC and the DC power are available
On FAP 120RH, LIGHT EMER pushbutton switch and its integral light are off
On overhead panel 25VU, EMER EXIT LT switch 4WL is in the OFF position
On overhead panel 25VU, No PED switch 190RH is in the OFF position
The overwing emergency lights are off
The emergency power supply unit is installed on the A/C for the first time, or
The battery was removed for more than 5 s and then it is installed again.

The load values are used as reference values during the EPSU SYSTEM TEST. It is necessary to examine that all connected emergency lights of the related EPSU operate.

Subtask 33-51-38-860-059-F ** ON A/C NOT FOR ALL

D. Preparation for the Test
(1) Make sure that the aircraft electrical circuits are energized.
(Ref. AMM TASK 24-41-00-861-002).
(2) Do this test:

ACTION	RESULT
1.In the cockpit, on the SIGNS panel 25VU:	In the cabin:
Set the EMER EXIT LT SWITCH 4WL to the ON position or Push the pushbutton EMER on FAP 120RH.	Make sure that all emergency lights come on. NOTE: If the EPSU supplies power to overwing emergency lights, make sure that these overwing emergency lights come on.
Set the EMER EXIT LT SWITCH 4WL to the OFF position or Push the pushbutton EMER on FAP 120RH again.	Make sure that all emergency lights go off.

CAUTION: DO NOT USE THE TEACH-IN PROCEDURE TO CLEAR EPSU FAILURE MESSAGES. THE TEACH-IN PROCEDURE IS NOT A SYSTEM RESET. IT CAN CHANGE THE EMERGENCY LIGHT CONFIGURATION AND CAUSE HIDDEN FAILURES.

(3) If the battery (5) was removed before, carefully put the battery (5) in the EPSU (1) (Ref. AMM TASK 33-51-38-400-002).

NOTE: To measure and keep the load values, the load programming (TEACH IN) of the EPSU starts automatically when:

The AC and the DC powers are available
On FAP 120RH, EMER pushbutton switch and its integral lights go off
On overhead panel 25VU, EMER EXIT LT switch 4WL is in the OFF position
On overhead panel 25VU, NO SMOKING switch 190RH is in the OFF position
The overwing emergency lights go off
The EPSU is installed on the A/C for the first time, or the battery was removed for more than 5 sec and it is installed again.

The load values are used as reference during the EPSU system test. It is necessary to examine that all connected emergency lights of the related EPSU operate.

Subtask 33-51-38-740-052-A

E. BITE Test
(1) Do the operational check of the EPSU thru BITE check (Ref. AMM TASK 33-51-00-710-001).

5. Close-up
Subtask 33-51-38-410-052-B ** ON A/C NOT FOR ALL

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Install the ceiling panel:
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
install 221BC at the left forward passenger/crew door (Ref. AMM TASK 25-23-42-400-001).
(b) FOR [11WL] (EPSU)
install 251KC between the rear emergency exit doors (Ref. AMM TASK 25-23-41-400-001).
(c) FOR [12WL] (EPSU)
install 251KC between the rear emergency exit doors (Ref. AMM TASK 25-23-41-400-001).
(d) FOR [14WL] (EPSU)
install 231JC between the forward emergency exit doors (Ref. AMM TASK 25-23-41-400-001).
(e) FOR [15WL] (EPSU)
install 231JC between the forward emergency exit doors (Ref. AMM TASK 25-23-41-400-001).
(3) Engage the emergency oxygen container and install the ceiling panel:
(a) FOR [13WL] (EPSU)

Lift and engage emergency oxygen container 33WR between the AFT passenger/crew doors (Ref. AMM TASK 35-21-41-400-001).
Install ceiling panel 261CC at the left aft passenger/crew door (Ref. AMM TASK 25-23-42-400-002).

(4) Remove the stepladder(s).

Subtask 33-51-38-410-052-C ** ON A/C NOT FOR ALL

A. Close Access
(1) Install the ceiling panel:
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
install 221BC at the left forward passenger/crew door (Ref. AMM TASK 25-23-42-400-001).
(2) Install the lower sidewall panel:
(a) FOR [11WL] (EPSU)
install 241KW at the left emergency exit(s) (Ref. AMM TASK 25-23-44-400-001).
(b) FOR [12WL] (EPSU)
install 242KW at the right emergency exit(s) (Ref. AMM TASK 25-23-44-400-001).
(c) FOR [13WL] (EPSU)
close the ceiling filler-panel adjacent to ceiling panel 261CC at the left AFT passenger/crew door.
(3) Remove the stepladder(s).

Subtask 33-51-38-410-052-D ** ON A/C NOT FOR ALL

A. Close Access
(1) Make sure that the work area is clean and clear of tools and other items.
(2) Install the ceiling panel(s):
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
install 221BC at the left forward passenger/crew door (Ref. AMM TASK 25-23-42-400-001).
(b) FOR [11WL] (EPSU)
install 251KC between the aft emergency exit doors (Ref. AMM TASK 25-23-41-400-001).
(c) FOR [12WL] (EPSU)
install 251KC between the aft emergency exit doors (Ref. AMM TASK 25-23-41-400-001).
(3) Install the lower sidewall panel(s):
(a) FOR [16WL] (EPSU)
install 242KW at the emergency exits (Ref. AMM TASK 25-23-44-400-001).
(b) FOR [17WL] (EPSU)
install 241KW at the emergency exits (Ref. AMM TASK 25-23-44-400-001).
(4) Install the ceiling panel:
(a) FOR [13WL] (EPSU)
install the ceiling panel 261CC between the aft passenger/crew doors (Ref. AMM TASK 25-23-42-400-002).
(5) Remove the stepladder(s).

Subtask 33-51-38-862-051-A

B. De-energize the aircraft electrical circuits (Ref. AMM TASK 24-41-00-862-002).

[Rev.10 from 2021] 2026.04.01 00:57:46 UTC