Removal of the Hydraulic Control Unit Pressure Switch [CFMB]

TASK 78-31-16-000-041-A
Removal of the Hydraulic Control Unit Pressure Switch

FIN: 4102KS ** 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	ACCESS PLATFORM 1M(3 FT)
No specific	AR	CAP - BLANKING
No specific	AR	SCRAPER - PLASTIC
No specific	AR	WARNING NOTICE(S)

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.CP1039)	acetone
(Material No.CP1041)	isopropyl alcohol
(Material No.CP2011)	stoddard solvent
(Material No.CP2559)	ardrox 552
(Material No.CP2560)	turco ind 79
(Material No.CP2566)	mag-chem teksol
(Material No.CP2584)	degreasol 99 R
(Material No.CP2656)	mag-chem skysol
(Material No.14SBA1)	Textile-Lint free Cotton -

C. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
FOR [1000EM1] (ENGINE-1)
437AL, 438AR
FOR [1000EM2] (ENGINE-2)
447AL, 448AR

D. Referenced Information

REFERENCE	DESIGNATION
TASK 29-14-00-614-001-A	Depressurization of the Hydraulic Reservoirs
TASK 71-13-00-010-040-B	Opening of the Fan Cowl Doors
TASK 78-30-00-481-041-B	Make the Thrust Reverser Unserviceable for Maintenance
Pressure Switch

3. Job Set-up
Subtask 78-31-16-941-050-A ** ON A/C NOT FOR ALL

A. Safety Precautions
(1) On the center pedestal, on the ENG panel 115VU:
(a) Put a WARNING NOTICE(S) to tell persons not to start the engine.
(2) Make sure that the engine 1(2) shutdown occurred not less than 5 minutes before you do this procedure.
(3) On the overhead maintenance panel 50VU:
(a) Make sure that the ON legend of the ENG/FADEC GND PWR/1(2) pushbutton switch is off.
(b) Put a WARNING NOTICE(S) to tell persons not to energize the FADEC 1(2).

Subtask 78-31-16-010-050-A ** ON A/C NOT FOR ALL

B. Get Access
(1) Open the fan cowl doors: (Ref. AMM TASK 71-13-00-010-040)
(a) FOR [1000EM1] (ENGINE-1)
437AL 438AR
(b) FOR [1000EM2] (ENGINE-2)
447AL 448AR
(2) Put the ACCESS PLATFORM 1M(3 FT) in position.

Subtask 78-31-16-040-050-A ** ON A/C NOT FOR ALL

C. Make the thrust reverser unserviceable (Ref. AMM TASK 78-30-00-481-041).

Subtask 78-31-16-614-050-A ** ON A/C NOT FOR ALL

D. Depressurization of the Hydraulic Reservoirs.

WARNING: FAILURE TO SHUT OFF AIRCRAFT HYDRAULIC SUPPLY TO THRUST REVERSER CAN RESULT IN SERIOUS INJURY TO PERSONNEL.

(1) For engine 1 depressurize the Green hydraulic reservoir (Ref. AMM TASK 29-14-00-614-001).
(2) For engine 2 depressurize the Yellow hydraulic reservoir (Ref. AMM TASK 29-14-00-614-001).

4. Procedure
Subtask 78-31-16-020-050-A ** ON A/C NOT FOR ALL

A. Removal of the Pressure Switch
(1) Disconnect the pylon electrical harness from the pressure switch.
(2) Install CAP - BLANKING on the electrical connectors.
(3) Remove the sealant from the HCU and the pressure switch with a SCRAPER - PLASTIC.
(4) Clean and dry the surfaces :

WARNING: BE CAREFUL WHEN YOU USE CONSUMABLE MATERIALS. OBEY THE MATERIAL MANUFACTURER'S INSTRUCTIONS AND YOUR LOCAL REGULATIONS.

(a) Clean any remaining sealant from the surfaces of the HCU and the pressure switch with acetone (Material No.CP1039) or stoddard solvent (Material No.CP2011) or ardrox 552 (Material No.CP2559) or turco ind 79 (Material No.CP2560) or mag-chem teksol (Material No.CP2566) or degreasol 99 R (Material No.CP2584) or mag-chem skysol (Material No.CP2656) or isopropyl alcohol (Material No.CP1041) .
(b) Dry the surfaces with a Textile-Lint free Cotton - (Material No.14SBA1) .
(5) Remove and discard the safety wire.
(6) Remove the three bolts which attach the pressure switch to the HCU.
(7) Remove the pressure switch.
(8) remove and discard the preformed packing (10) and the backup ring (20).

[Rev.10 from 2021] 2026.04.01 13:11:40 UTC