Installation of the Ground Auxiliary Power Control Unit (GAPCU)

TASK 24-41-34-400-001-B
Installation of the Ground Auxiliary Power Control Unit (GAPCU)

CAUTION: MAKE SURE THAT NO AC OR DC POWER IS CONNECTED TO THE AIRCRAFT ELECTRICAL CIRCUITS. THERE IS A RISK OF DAMAGE TO EQUIPMENT DURING ITS REMOVAL/ INSTALLATION IF THE AC OR DC POWER STAYS CONNECTED.

ZONE: 122
FIN: 24XG ** 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	ACCESS PLATFORM 1M (3 FT)-ADJUSTABLE
No specific	1	ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE
No specific	AR	WARNING NOTICE(S)

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
122	AVIONICS COMPARTMENT
121AL, 811

C. Referenced Information

REFERENCE	DESIGNATION
TASK 24-41-00-740-002-B	Operational Check of the GAPCU via the CFDS
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)
Ground Auxiliary Power Control Unit (GAPCU) ** ON A/C NOT FOR ALL
Ground Auxiliary Power Control Unit (GAPCU) ** ON A/C NOT FOR ALL

3. Job Set-up
Subtask 24-41-34-860-051-A ** ON A/C NOT FOR ALL

A. Aircraft Maintenance Configuration
(1) Make sure that the ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE is in position at the access door 811.
(2) Make sure that the access door 811 is open.
(3) Make sure that the ACCESS PLATFORM 1M (3 FT)-ADJUSTABLE is in position at the access door 121AL.
(4) Make sure that the access door 121AL is open.
(5) Make sure that the external power connector is not connected to the aircraft external power receptacle.
(6) Make sure that a WARNING NOTICE(S) is in position on the access door 121AL to tell persons not to use the external power receptacle.
(7) In the cockpit, on the overhead ELEC panel 35VU, make sure that these pushbutton switches are released:

BAT 1, BAT 2,
APU GEN,
GEN 1, GEN 2,
EXT PWR.

(8) In the cockpit, make sure that WARNING NOTICE(S) is (are) in position to tell persons not to operate the pushbutton switches on these overhead panels:

21VU (EMER ELEC PWR),
35VU (ELEC).

(9) In the cockpit, on the APU section of the overhead panel 25VU, make sure that a WARNING NOTICE(S) is in position to tell persons not to start the APU.

Subtask 24-41-34-865-060-A ** ON A/C NOT FOR ALL

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
122VU	ELEC/GAPCU	17XG	W24
122VU	ELEC/EXT PWR/CTL	11XG	X29
123VU	GND/PWR/PROT	2XG	AB07

4. Procedure
Subtask 24-41-34-420-051-A ** ON A/C NOT FOR ALL

A. Installation of the GAPCU
(1) Clean the component interfaces and the adjacent area.
(2) Do an inspection of the component interfaces and the adjacent area.
(3) Remove the CAP-BLANKING from each electrical connector and receptacle.
(4) Make sure that all the electrical connections are clean and in the correct condition.
(5) Install the GAPCU on its rack (6).
(6) Push the GAPCU on its rack (6) to connect the electrical connector (5).
(7) Engage the nuts (1) on the lugs (2) and tighten.

Subtask 24-41-34-865-061-A ** ON A/C NOT FOR ALL

B. 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
122VU	ELEC/GAPCU	17XG	W24
122VU	ELEC/EXT PWR/CTL	11XG	X29
123VU	GND/PWR/PROT	2XG	AB07

Subtask 24-41-34-710-051-A ** ON A/C NOT FOR ALL

C. Operational Test of the Ground Auxiliary Power Control Unit (GAPCU)
(1) Do an operational test of the GAPCU with the CFDS (Ref. AMM TASK 24-41-00-740-002).

NOTE: As an alternative procedure for the operational test without the CFDS, you can do this procedure (Ref. AMM TASK 24-41-00-861-002).
Make sure that the aircraft electrical circuits are correctly energized with the external power supply.

5. Close-up
Subtask 24-41-34-410-051-A ** 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) Remove the WARNING NOTICE(S).
(3) Close the access door 811.
(4) Close the access door 121AL.
(5) Remove the access platform(s).

[Rev.10 from 2021] 2026.03.31 23:24:21 UTC