Removal of the Emergency Power Supply Unit (EPSU)

TASK 33-51-38-000-001-A
Removal 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	AR	CAP - BLANKING
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER
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 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 33-51-38-000-002-A	Removal 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 25-23-42-000-001-A	Removal of the Ceiling Panels - Forward Utility Area
FOR [11WL] (EPSU)
TASK 25-23-41-000-001-A	Removal of the Ceiling Panels
TASK 25-23-44-000-001-A	Removal of the Lower Sidewall Panels (Dado Panels)
FOR [12WL] (EPSU)
TASK 25-23-41-000-001-A	Removal of the Ceiling Panels
TASK 25-23-44-000-001-A	Removal of the Lower Sidewall Panels (Dado Panels)
FOR [13WL] (EPSU)
TASK 25-23-42-000-002-A	Removal of the Ceiling Panels - Aft Utility Area
TASK 35-21-41-000-001-A	Removal of the Emergency Oxygen Containers
FOR [14WL] (EPSU)
TASK 25-23-41-000-001-A	Removal of the Ceiling Panels
FOR [15WL] (EPSU)
TASK 25-23-41-000-001-A	Removal of the Ceiling Panels
FOR [16WL] (EPSU)
TASK 25-23-44-000-001-A	Removal of the Lower Sidewall Panels (Dado Panels)
FOR [17WL] (EPSU)
TASK 25-23-44-000-001-A	Removal of the Lower Sidewall Panels (Dado Panels)

3. Job Set-up
Subtask 33-51-38-860-057-A ** ON A/C NOT FOR ALL

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

Subtask 33-51-38-860-057-D ** ON A/C NOT FOR ALL

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

Subtask 33-51-38-860-057-E ** ON A/C NOT FOR ALL

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

Subtask 33-51-38-860-057-F ** ON A/C NOT FOR ALL

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

Subtask 33-51-38-710-054-A

B. Operational Test
(1) To make sure that all related emergency lights operate correctly before you remove the EPSU, do this procedure:

Set EMER EXIT LT switch 4WL to the ON position.
Make sure that the related emergency lights come on.
Set EMER EXIT LT switch 4WL to the OFF position.

Subtask 33-51-38-865-050-A

C. Open, safety and tag 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 33-51-38-010-050-B ** ON A/C NOT FOR ALL

D. Get Access
(1) Put the STEPLADDER 1.5 M (5 FT) in position:
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
at the left forward passenger/crew door
(b) FOR [11WL] (EPSU)
between the rear emergency exit doors
(c) FOR [12WL] (EPSU)
between the rear emergency exit doors
(d) FOR [13WL] (EPSU)
between the aft passenger/crew doors
(e) FOR [14WL] (EPSU)
between the forward emergency exit doors
(f) FOR [15WL] (EPSU)
between the forward emergency exit doors.
(2) Remove the ceiling panel to get access to the emergency power supply unit:
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
remove 221BC at the left forward passenger/crew door (Ref. AMM TASK 25-23-42-000-001).
(b) FOR [11WL] (EPSU)
remove 251KC between the rear emergency exit doors (Ref. AMM TASK 25-23-41-000-001).
(c) FOR [12WL] (EPSU)
remove 251KC between the rear emergency exit doors (Ref. AMM TASK 25-23-41-000-001).
(d) FOR [14WL] (EPSU)
remove 231JC between the forward emergency exit doors (Ref. AMM TASK 25-23-41-000-001).
(e) FOR [15WL] (EPSU)
remove 231JC between the forward emergency exit doors (Ref. AMM TASK 25-23-41-000-001).
(3) Lower one side of the emergency oxygen container and remove the ceiling panel to get access to the emergency power supply unit:
(a) FOR [13WL] (EPSU)

Disengage and lower one side of emergency oxygen container 33WR between the aft passenger/crew doors (Ref. AMM TASK 35-21-41-000-001).
Do not disconnect the electrical connector of the emergency oxygen container.
Remove ceiling panel 261CC at the left aft passenger/crew door (Ref. AMM TASK 25-23-42-000-002).

Subtask 33-51-38-010-050-C ** ON A/C NOT FOR ALL

D. Get Access
(1) Put the STEPLADDER 1.5 M (5 FT) in position:
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
at the left forward passenger/crew door
(b) FOR [13WL] (EPSU)
between the aft passenger/crew doors.
(2) Remove the ceiling panel to get access to the emergency power supply unit:
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
remove 221BC at the left forward passenger/crew door (Ref. AMM TASK 25-23-42-000-001).
(3) Remove the lower sidewall panel to get access to the emergency power supply unit:
(a) FOR [11WL] (EPSU)
remove 241KW at the left emergency exit(s) (Ref. AMM TASK 25-23-44-000-001).
(b) FOR [12WL] (EPSU)
remove 242KW at the right emergency exit(s) (Ref. AMM TASK 25-23-44-000-001).
(c) FOR [13WL] (EPSU)
open the ceiling filler-panel door adjacent to ceiling panel 261CC at the left aft passenger/crew door.

Subtask 33-51-38-010-050-D ** ON A/C NOT FOR ALL

D. Get Access
(1) Put the STEPLADDER 1.5 M (5 FT) in position:
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
at the left forward passenger/crew door
(b) FOR [11WL] (EPSU)
between the aft emergency exit doors
(c) FOR [12WL] (EPSU)
between the aft emergency exit doors
(d) FOR [13WL] (EPSU)
between the aft passenger/crew doors.
(2) Remove the ceiling panel(s) to get access to the emergency power supply unit:
(a) FOR [10WL] (POWER-EMERGENCY SUPPLY)
remove 221BC at the left forward passenger/crew door (Ref. AMM TASK 25-23-42-000-001).
(b) FOR [11WL] (EPSU)
remove 251KC between the aft emergency exit doors (Ref. AMM TASK 25-23-41-000-001).
(c) FOR [12WL] (EPSU)
remove 251KC between the aft emergency exit doors (Ref. AMM TASK 25-23-41-000-001).
(3) Remove the lower sidewall panel(s) to get access to the emergency power supply unit:
(a) FOR [16WL] (EPSU)
remove 242KW at the emergency exit(s) (Ref. AMM TASK 25-23-44-000-001).
(b) FOR [17WL] (EPSU)
remove 241KW at the emergency exit(s) (Ref. AMM TASK 25-23-44-000-001).
(4) Remove the ceiling panel to get access to the emergency power supply unit:
(a) FOR [13WL] (EPSU)
remove ceiling panel 261CC between the aft passenger/crew doors (Ref. AMM TASK 25-23-42-000-002).

4. Procedure
Subtask 33-51-38-020-051-B

A. Removal of the Emergency Power Supply Unit (EPSU)

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.

(1) Disconnect the electrical connector (2) from the EPSU (1).
(2) Put the CAP-BLANKING on each disconnected electrical connector and receptacle.
(3) Remove the screws (3) and the washers (4) from the EPSU (1).
(4) Remove the EPSU (1).

NOTE: With a fully charged EPSU battery, a new start of the power supply of the emergency lights will be faster.

NOTE: If the EPSU was removed because it was defective and no battery fault was present, it is recommended to use its battery immediately in the replacement unit. The battery must not be removed for more than 24 hours.

(5) If necessary, remove the battery (5) from the EPSU (1) (Ref. AMM TASK 33-51-38-000-002).

[Rev.10 from 2021] 2026.04.01 00:57:44 UTC