Replacement of the NLG Shock Absorber Dynamic Seals

TASK 32-21-13-960-001-A
Replacement of the NLG Shock Absorber Dynamic Seals

WARNING: MAKE SURE THAT THE GROUND SAFETY-LOCKS ARE IN POSITION ON THE LANDING GEAR. THIS WILL PREVENT UNWANTED MOVEMENT OF THE LANDING GEAR, AND THUS POSSIBLE INJURY TO PERSONS AND DAMAGE TO THE AIRCRAFT AND/OR EQUIPMENT.

WARNING: MAKE SURE THAT THE TRAVEL RANGES OF THE FLIGHT CONTROLS SURFACES ARE CLEAR. MOVEMENT OF FLIGHT CONTROLS CAN CAUSE INJURY TO PERSONS AND/OR DAMAGE TO EQUIPMENT.

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

1. Reason for the Job
This procedure tells you how to replace the dynamic seals on the NLG shock absorber when there is leakage at the upper cam (between the sliding rod and the cylinder).

NOTE: To replace the dynamic seals, it is necessary to open the shock absorber. Because of the risk of contamination, you must do this task in a very clean environment. Thus, the manufacturer recommends that you do this procedure in a shop.
If it is not possible to do the procedure in a shop, use all the necessary precautions to prevent pollution.

NOTE: If a leakage from the NLG shock absorber occurred, one return flight is permitted for repair to be completed, if:

The leak rate from the turning tube drain-hole is less than 10 drops/min, weight on wheels
The NLG shock-absorber oil-replenishment and nitrogen-filling (aircraft on wheels) (Ref. AMM TASK 12-12-32-611-001) is done, less than one hour before a flight.

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	AR	CHARGING EQUIPMENT - FLUID, STANDARD
No specific	AR	GAGE - PRESSURE, TIRE
No specific	AR	NITROGEN COMPRESSED SOURCE - GROUND
No specific	AR	ROD
No specific	AR	SAFETY BARRIER(S)
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER
No specific	AR	SPATULA - NON METALLIC
No specific	AR	WARNING NOTICE(S)
89901	1	SPATULA
D46795	1	JAWS-FALSE
M21930	1	FILLING ASSEMBLY
M46200	1	JAWS-FALSE
M46201	1	WRENCH-PIN

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.02BBB9)	Mineral Hydraulic Fluid-Damper - -
(Material No.02CBB1)	Mineral Hydraulic Fluid & Additives-Damper Shock Struts -
(Material No.02CCC1)	Mineral Hydraulic Fluid & Additives-Damper Landing Gear -
(Material No.06LDG2)	Non Hardening Jointing Putty-High Temp. Area - Structure
(Material No.08BAA9)	Non Aqueous Cleaner-General - -
(Material No.08BBB1)	Non Aqueous Cleaner-- Petroleum Based -

C. Expendable Parts

FIG.ITEM	DESIGNATION	IPC-CSN
12	SEAL	AIPC 32-21-13-11-030
13	SCRAPER	AIPC 32-21-13-11-040
11	SEAL	AIPC 32-21-13-11-050
10	BACK-UP RINGS	AIPC 32-21-13-11-060
12	SEAL	AIPC 32-21-13-21-030
13	SCRAPER	AIPC 32-21-13-21-040
11	SEAL	AIPC 32-21-13-21-050
10	BACK-UP RINGS	AIPC 32-21-13-21-060

D. Referenced Information

REFERENCE	DESIGNATION
TASK 12-12-32-611-001-A	NLG Shock Absorber Oil Replenishment and Nitrogen Filling (Aircraft on Wheels)
TASK 32-21-13-000-001-A	Removal of the NLG Shock Absorber Assy
TASK 32-21-13-000-001-A-01	Removal of the NLG Shock Absorber Assy (with nose jacking only)
TASK 32-21-13-400-001-A	Installation of the NLG Shock Absorber Assy
TASK 32-21-13-400-001-A-01	Installation of the NLG Shock Absorber Assy (with nose jacking only)
NLG Shock Absorber- Dynamic Seals ** ON A/C NOT FOR ALL
NLG Shock Absorber - Dynamic Seals ** ON A/C NOT FOR ALL
NLG Shock Absorber - Reference Axes
NLG Shock Absorber - Pressurization

3. Job Set-up
Subtask 32-21-13-941-054-A

A. Safety Precautions
(1) In the cockpit, on the panel 400VU put WARNING NOTICE(S) in position to tell persons not to operate the landing gear control lever.
(2) On the steering handwheels (CAPT and F/O) and on the brake pedals, put WARNING NOTICE(S) in position to tell persons not to operate them.
(3) Put the SAFETY BARRIER(S) in position.

Subtask 32-21-13-010-051-A

B. Get Access
(1) Remove the NLG shock absorber (Ref. AMM TASK 32-21-13-000-001).
(2) Use the D46795 JAWS-FALSE and the M46200 JAWS-FALSE to hold the shock absorber.

Subtask 32-21-13-865-054-A

C. Open, safety and tag this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
121VU	HYDRAULIC/BRAKING AND STEERING/SYS2/SPLY	4GG	M36
121VU	HYDRAULIC/BRAKING AND STEERING/SYS2/CTL	3GG	M35
121VU	HYDRAULIC/BRAKING AND STEERING/SYS1/CTL	1GG	M34
121VU	HYDRAULIC/BRAKING AND STEERING/SYS1/IND AND/SPLY	2GG	M33

4. Procedure
Subtask 32-21-13-020-053-A

A. Preparation for Removal

WARNING: BEFORE YOU REMOVE PARTS FROM THE SHOCK ABSORBER, MAKE SURE THAT YOU MAKE MATCHMARKS WITH A FELT-TIP MARKER. THIS IS VERY IMPORTANT. IT WILL LET YOU INSTALL THE PARTS IN THE CORRECT POSITION WHEN YOU ASSEMBLE THE SHOCK ABSORBER AGAIN. INCORRECT ASSEMBLY OF THE SHOCK ABSORBER IS DANGEROUS FOR AIRCRAFT SAFETY.

(1) Before you remove the cylinder (3), make a mark with a felt tip marker to show the position of the sliding tube (9), upper cam (7), cylinder (3).
(2) Carefully remove the sealants with a SPATULA - NON METALLIC.
(3) Make sure that the shock absorber is fully depressurized and fully compressed

WARNING: BEFORE, DISASSEMBLY MAKE SURE THAT YOU RELEASE ALL THE NITROGEN PRESSURE FROM THE SHOCK ABSORBER. REMAINING PRESSURE CAN CAUSE DAMAGE TO THE SHOCK ABSORBER AND INJURY TO PERSONS.

(a) If not, remove the cap (1) and slowly open the valve (2) by one and a half turn maximum.
(b) Fully compress the shock absorber.
(4) Drain the fluid of the shock absorber.

Subtask 32-21-13-020-054-A

B. Disassembly of the Shock Absorber
(1) Remove the retaining ring (4) with the M46201 WRENCH-PIN.
(a) Turn the retaining bush (5) to align its open groove with the 1.6 mm (0.0629 in.) dia. hole at the end of the upper cam (7).
(b) Put a ROD in the 1.6 mm (0.0629 in.) dia. hole.
(c) Turn the retaining bush (5) with the M46201 WRENCH-PIN.

NOTE: This causes the retaining ring (4) to move so that you can hold it without damage to the upper cam (7).

(d) Remove the retaining ring (4).
(2) Remove the retaining bush (5) and the eight dowels (6).
(3) Carefully remove the cylinder (3) and the upper cam (7) together.
(4) Remove the upper cam (7).

Subtask 32-21-13-020-055-B

C. Removal of the Dynamic Seals from the Upper Cam (7)
(1) Remove the seal (11) and the back-up rings (10) with the 89901 SPATULA and discard them.
(2) Remove the seal (12) with the 89901 SPATULA and discard it.
(3) If necessary, remove the scraper (13) and discard it.

Subtask 32-21-13-210-051-A

D. Cleaning of the Retained Part :

CAUTION: DO NOT USE SOLVENTS THAT CONTAIN CHLORINE TO CLEAN PARTS WITH A RILSAN COATING.

(1) Clean the parts that have grease with Non Aqueous Cleaner-General - - (Material No.08BAA9) .
(2) Clean all the parts with Non Aqueous Cleaner-- Petroleum Based - (Material No.08BBB1) and dry them with filtered compressed air.
(3) Fully clean the seal grooves on the upper cam (7).
(4) Make sure that the parts retained from the removed component are clean and in the correct condition.
(5) Do an inspection of the component interfaces and the adjacent area.

Subtask 32-21-13-420-053-A ** ON A/C NOT FOR ALL

CAUTION: MAKE SURE THAT THE CHEVRON END OF THE ELASTOMER SEAL POINTS DOWN WHEN YOU INSTALL THE SEAL IN THE GROOVE OF THE UPPER CAM.

E. Installation of the Dynamic Seals on the Upper Cam

NOTE: The dynamic seal (12) has two parts, an elastomer seal and a back-up ring.

(1) Do not expand the seals (11) and (12) more than necessary when you install them.
(2) Lubricate the new AIPC 32-21-13-11-030 SEAL (12) or AIPC 32-21-13-21-030 SEAL (12) with Mineral Hydraulic Fluid-Damper - - (Material No.02BBB9) .
(3) Use the 89901 SPATULA to install the elastomer seal of the new seal (12) in the correct direction in the groove of the upper cam (7).

NLG Shock Absorber- Dynamic Seals ** ON A/C NOT FOR ALL

(4) Install the back-up ring of the new seal (12) in the groove of the upper cam (7).
(5) If the scraper (13) is removed, install the new AIPC 32-21-13-11-040 SCRAPER (13) or AIPC 32-21-13-21-040 SCRAPER (13) on the upper cam (7).
(6) Lubricate the new AIPC 32-21-13-11-050 SEAL (11) or AIPC 32-21-13-21-050 SEAL (11) with Mineral Hydraulic Fluid-Damper - - (Material No.02BBB9) .
(7) Use the 89901 SPATULA to install the new seal (11) and the new AIPC 32-21-13-11-060 BACK-UP RINGS (10) or AIPC 32-21-13-21-060 BACK-UP RINGS (10) on the upper cam (7).

Subtask 32-21-13-420-053-B ** ON A/C NOT FOR ALL

CAUTION: MAKE SURE THAT THE CHEVRON END OF THE ELASTOMER SEAL POINTS DOWN WHEN YOU INSTALL THE SEAL IN THE GROOVE OF THE UPPER CAM.

E. Installation of the Dynamic Seals on the Upper Cam (7)

NOTE: You must install the seals dry.
Do not stretch the seals more than necessary when you install them.

NOTE: The dynamic seal (12) has two parts, an elastomer seal and a back-up ring.

(1) Install the elastomer seal of the new AIPC 32-21-13-11-030 DYNAMIC SEAL (12) in the correct direction in the groove of the upper cam (7) with the 89901 SPATULA.

NLG Shock Absorber- Dynamic Seals ** ON A/C NOT FOR ALL

(2) Install the back-up ring of the new AIPC 32-21-13-11-030 DYNAMIC SEAL (12) in the groove of the upper cam (7).
(3) If necessary, install the new AIPC 32-21-13-11-040 SCRAPER (13) on the upper cam (7).
(4) Install the new AIPC 32-21-13-11-050 SEAL (11) and the new AIPC 32-21-13-11-060 BACK-UP RINGS (10) with the 89901 SPATULA on the upper cam (7).

Subtask 32-21-13-420-053-G ** ON A/C NOT FOR ALL

CAUTION: MAKE SURE THAT THE CHEVRON END OF THE ELASTOMER SEAL POINTS DOWN WHEN YOU INSTALL THE SEAL IN THE GROOVE OF THE UPPER CAM.

E. Installation of the Dynamic Seals on the Upper Cam

NLG Shock Absorber - Dynamic Seals ** ON A/C NOT FOR ALL

NOTE: The dynamic seal (12) has three parts, an O-ring, an elastomer seal and a back-up ring.

(1) Do not expand the seals (11) and (12) more than necessary when you install them.
(2) Lubricate the new AIPC 32-21-13-21-030 SEAL (12) with Mineral Hydraulic Fluid-Damper - - (Material No.02BBB9) .
(3) Use the 89901 SPATULA to install the elastomer seal and the O-ring of the new seal (12) in the groove of the upper cam (7).
(4) Install the back-up ring of the new seal (12) in the groove of the upper cam (7).
(5) If the scraper (13) is removed, install the new AIPC 32-21-13-21-040 SCRAPER (13) on the upper cam (7).
(6) Lubricate the new AIPC 32-21-13-21-050 SEAL (11) with Mineral Hydraulic Fluid-Damper - - (Material No.02BBB9) .
(7) Use the 89901 SPATULA to install the new seal (11) and the new AIPC 32-21-13-21-060 BACK-UP RINGS (10) on the upper cam (7).

Subtask 32-21-13-420-054-A

F. Assembly of the Shock Absorber

CAUTION: ALWAYS INSTALL THE SAME LOWER CAM WITH THE SAME UPPER CAME THEY ARE A MATCHED ASSEMBLY AND MUST STAY TOGETHER.

(1) Apply Mineral Hydraulic Fluid-Damper - - (Material No.02BBB9) or Mineral Hydraulic Fluid & Additives-Damper Shock Struts - (Material No.02CBB1) or Mineral Hydraulic Fluid & Additives-Damper Landing Gear - (Material No.02CCC1) to the surface of parts that touch the seals (10) and (12).
(2) Install the upper cam (7) on the cylinder (3).

NOTE: You must align the reference line on the upper cam (7) with the reference line on the lower cam (8).

NLG Shock Absorber - Reference Axes

(3) Apply Non Hardening Jointing Putty-High Temp. Area - Structure (Material No.06LDG2) only to the longer bearing surface of the upper cam (7).

WARNING: DURING INSTALLATION OF THE CYLINDER, MAKE SURE THAT YOU KEEP THE AXIS XX' PARALLEL TO THE AXIS YY' AND THE AXIS ZZ' PERPENDICULAR TO THE AXIS YY'. IF YOU DO NOT DO THIS, THE ASSEMBLY WILL NOT BE CORRECT. THIS IS DANGEROUS FOR AIRCRAFT SAFETY.

(4) Carefully engage the cylinder (3) with the upper cam (7) in the sliding tube (9) until it touches the bottom of the bore.

NLG Shock Absorber - Reference Axes

(5) Put the upper cam (7) in the position that agrees with the mark you made at removal.
(6) Apply Non Hardening Jointing Putty-High Temp. Area - Structure (Material No.06LDG2) on the eight dowels (6), the retaining bush (5) and the retaining ring (4).
(7) Install the eight dowels (6) and the retaining bush (5).
(8) Install the retaining ring (4) with the M46201 WRENCH-PIN.
Put the bent end of the retaining ring (4) in the open groove of the retaining bush (5).
(9) Make sure that the positions of the upper cam (7) and the lower cam (8) are correct.
(10) With the shock absorber in the fully extended position, measure the dimension "A" which must be approximately 377.5 mm (14.86 in.).

Subtask 32-21-13-710-051-A

G. Test of the Shock Absorber
(1) Pressurize the shock absorber with dry nitrogen to 19 bars (275 PSI) for one hour.

NOTE: If this operation is performed at an ambient temperature of 15°C +/- 5°C, this time can be decreased to 15 minutes minimum.

NLG Shock Absorber - Pressurization

(a) Install the M21930 FILLING ASSEMBLY on the charging valve (2).
(b) Install the CHARGING EQUIPMENT - FLUID, STANDARD on the M21930 FILLING ASSEMBLY, as follows :
1 Connect the filling hose (22) to the M21930 FILLING ASSEMBLY.
2 Install the GAGE - PRESSURE, TIRE (21) on the 3-way valve (23).
3 Connect to the 3-way valve (23) to the filling hose (22).
4 Make sure that the control valves (24) and (25) are closed.
5 Connect the NITROGEN COMPRESSED SOURCE - GROUND to the 3-way valve (23) with the supply hose (26).
(c) Open the control valve (25) to inflate the shock absorber to 19 bars (275 PSI).
Close the control valve (25) to stop the nitrogen supply.
(2) After one hour, measure the pressure of the shock absorber : the pressure must not decrease.
(3) Open the control valve (24) to depressurize the shock absorber.
(4) Remove the CHARGING EQUIPMENT - FLUID, STANDARD and the M21930 FILLING ASSEMBLY.
(5) Fully compress the shock absorber.

Subtask 32-21-13-420-055-A

H. Installation of the NLG Shock Absorber.

NOTE: The shock absorber is empty, you must do a full servicing of the shock absorber during the installation procedure.

(1) Install the NLG Shock Absorber (Ref. AMM TASK 32-21-13-400-001).

5. Close-up
Subtask 32-21-13-865-055-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
121VU	HYDRAULIC/BRAKING AND STEERING/SYS2/SPLY	4GG	M36
121VU	HYDRAULIC/BRAKING AND STEERING/SYS2/CTL	3GG	M35
121VU	HYDRAULIC/BRAKING AND STEERING/SYS1/CTL	1GG	M34
121VU	HYDRAULIC/BRAKING AND STEERING/SYS1/IND AND/SPLY	2GG	M33

Subtask 32-21-13-860-054-A

B. Put the aircraft back to its initial configuration.
(1) Remove the safety barriers.
(2) Remove the WARNING NOTICE(S).
(3) Make sure that the work area is clean and clear of tools and other items.

[Rev.10 from 2021] 2026.04.01 00:42:07 UTC