Check of the NLG Shock Absorber Charge-Pressure

TASK 12-14-32-614-004-A
Check of the NLG Shock Absorber Charge-Pressure

WARNING: PUT THE SAFETY DEVICES AND THE WARNING NOTICES IN POSITION BEFORE YOU START A TASK ON OR NEAR:

THE FLIGHT CONTROLS
THE FLIGHT CONTROL SURFACES
THE LANDING GEAR AND THE RELATED DOORS
COMPONENTS THAT MOVE.

MOVEMENT OF COMPONENTS CAN KILL OR CAUSE INJURY TO PERSONS AND/OR CAN CAUSE DAMAGE TO THE EQUIPMENT.

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: DO NOT LET COMPRESSED GAS TOUCH YOUR SKIN. THE GAS CAN GO THROUGH THE SKIN AND MAKE BUBBLES IN THE BLOOD. THIS CONDITION CAN KILL YOU.

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

1. Reason for the Job

NOTE: If you do this task immediately after the new full servicing of the NLG shock absorber (Ref. AMM TASK 12-12-32-611-005-A), it is possible that the measured pressure values are out of tolerance (too high). This is because during the full servicing of the NLG shock absorber, the charging pressures given (Ref. AMM TASK 12-12-32-611-005-A) are moderately higher than the ones given in the task. This is done to compensate for nitrogen absorption into the hydraulic fluid. It can take several days for this absorption to be completed.

NOTE: This task must be completed if the fluid level in the NLG shock absorber is correct (Ref. AMM TASK 12-12-32-610-001-A) or (Ref. AMM TASK 12-12-32-611-005-A) or (Ref. AMM TASK 12-12-32-611-001-A).

NOTE: It is recommended that you do this procedure with the aircraft on jacks or with the nose of the aircraft on jacks and the MLG wheels on the ground. It can be done on the ground if the aircraft cannot be jacked. If the aircraft is on jacks, it must in the correct position (Ref. AMM TASK 07-11-00-581-001-A) or (Ref. AMM TASK 07-11-00-581-003-A).

NOTE: You must do this procedure a minimum of two hours after the last aircraft operation. This will give time for separation of the gas and oil.

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

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 3M (10 FT)
No specific	AR	CHARGING EQUIPMENT - FLUID, STANDARD
No specific	AR	GAGE 200 BAR (2900 PSI) - PRESSURE, HYDRAULIC
No specific	AR	NITROGEN COMPRESSED SOURCE - GROUND
No specific	1	RULER - STEEL
No specific	AR	SAFETY BARRIER(S)
No specific	1	STEPLADDER 1.0 M (3.3 FT)
No specific	2	THERMOMETER-SURFACE CONTACT
No specific	AR	WARNING NOTICE(S)
No specific	Torque wrench: range to between 0.8 and 0.5 m.daN (70.80 and 44.25 lbf.in )
98F32001006000	1	GEAR FILLING KIT S-ABSOR
M21930	1	FILLING ASSEMBLY

B. Consumable Materials

REFERENCE	DESIGNATION
(Material No.14CCB6)	Testing Medium-Leak Detection - Oxygen System
(Material No.14VGC1)	Individual Compound-- Nitrogen Gaseous

C. Referenced Information

REFERENCE	DESIGNATION
TASK 12-14-32-614-004-A	Check of the NLG Shock Absorber Charge-Pressure
TASK 32-00-00-481-001-A	Installation of the Safety Devices on the Landing Gears
TASK 32-00-00-481-002-A	Installation of the Safety Devices on the Landing Gear Doors
TASK 32-22-00-010-001-A	Nose Gear Doors - Ground Doors Opening
TASK 32-22-00-410-001-A	Nose Gear Doors - Ground Doors Closing
NLG Charging Valve - Detail and Location
NLG Shock Absorber - Filling System
Pressure/Temperature Table - Shock Absorber Fully Extended
NLG Shock Absorber - Dimension H ** ON A/C NOT FOR ALL
NLG Shock Absorber - Dimension H ** ON A/C NOT FOR ALL
NLG Pressure/Extension Data (Weight on Wheels) - Positive Temperatures ** ON A/C NOT FOR ALL
NLG Pressure/Extension Data (Weight on Wheels) - Positive Temperatures ** ON A/C NOT FOR ALL
NLG Pressure/Extension Data (Weight on Wheels) - Negative Temperatures ** ON A/C NOT FOR ALL
NLG Pressure/Extension Data (Weight on Wheels) - Negative Temperatures ** ON A/C NOT FOR ALL

3. Job Set-up
Subtask 12-14-32-941-057-A

A. Safety Precautions
(1) As necessary, use the applicable SAFETY BARRIERS, specified by the operator's instructions and your local regulations.
(2) On the panel 400VU, make sure that the landing gear control-lever (6GA) is in the DOWN position.
(3) Put the WARNING NOTICE(S) in position to tell persons not to operate:

The NLG controls
The MLG controls.

(4) Make sure that the ground safety locks are installed on the landing gears and doors (Ref. AMM TASK 32-00-00-481-001) (Ref. AMM TASK 32-00-00-481-002).

Subtask 12-14-32-010-051-A

B. Get Access

WARNING: MAKE SURE THAT THE TRAVEL RANGES OF THE LANDING GEAR ARE CLEAR.

(1) Open the NLG doors (Ref. AMM TASK 32-22-00-010-001).
(2) If the aircraft is on jacks, put the ACCESS PLATFORM 3M (10 FT) in position.
(3) If the aircraft is on wheels, put the STEPLADDER 1.0 M (3.3 FT) in position.

4. Procedure
Subtask 12-14-32-614-059-A

A. NLG Shock Absorber Nitrogen Filling - Aircraft on Jacks

NOTE: You must not do the check immediately after the aircraft is lifted. The shock absorber charge-pressure must not be measured until the aircraft is on jacks for fifteen minutes. This will let the shock absorber charge-pressure become stable and make sure that the value recorded is accurate.

NOTE: When you fill the NLG shock absorber, you must use Individual Compound-- Nitrogen Gaseous (Material No.14VGC1) . This will make sure that the oxygen level stays low.

(1) Make sure that the shock absorber is extended fully and dimension H is between 447 mm (17.5984 in.) and 451 mm (17.7559 in.).

NLG Shock Absorber - Dimension H ** ON A/C NOT FOR ALL

(a) Use an applicable RULER - STEEL to measure dimension H.
(2) Install the 98F32001006000 GEAR FILLING KIT S-ABSOR on the M21930 FILLING ASSEMBLY as follows:

NLG Charging Valve - Detail and Location

NLG Shock Absorber - Filling System

(a) Connect the nitrogen supply hose (16) to the NITROGEN COMPRESSED SOURCE - GROUND.
(b) Connect the nitrogen supply hose (16) to the three-way valve (13).
(c) Connect the filling hose (12) to the three-way valve (13).
(d) Remove the blanking cap (9) and the plug (3) from the M21930 FILLING ASSEMBLY.
(e) Connect the filling hose (12) to the end fitting (8) of the M21930 FILLING ASSEMBLY.
(f) Slowly open the control valves (14) and (15) on the three-way valve (13) and the control valve on the nitrogen source. Blow nitrogen through the 98F32001006000 GEAR FILLING KIT S-ABSOR to bleed the system.
(g) Close the control valve on the nitrogen source.
(h) Close the control valves (14) and (15) on the three-way valve (13).
(3) Install the M21930 FILLING ASSEMBLY on the charging valve (2) as follows:

NLG Charging Valve - Detail and Location

NOTE: This will install the seal (5) on the charging valve (2).

(4) Do a check of the 98F32001006000 GEAR FILLING KIT S-ABSOR for leaks as follows:
(a) Make sure that the charging valve (2) and the control valve (14) on the three-way valve (13) are closed.
(b) Slowly open the control valve (15) on the three-way valve (13).
(c) Slowly open the control valve of the nitrogen source. Add nitrogen until the pressure read on the pressure gage is 19 bar (276 psi)
(d) Close the control valve of the nitrogen source.
(e) After the pressure has been adjusted, wait for a minimum of five minutes to make sure that the pressure is stable.

NOTE: This will make sure that there are no leaks in the 98F32001006000 GEAR FILLING KIT S-ABSOR.

(f) Close the control valve (15) on the three-way valve (13).
(5) Do a check of the NLG shock-absorber charge pressure as follows:
(a) Use a THERMOMETER-SURFACE CONTACT to measure and record the temperature of the NLG shock absorber adjacent to the charging valve (2). Make sure that the THERMOMETER-SURFACE CONTACT touches the shock absorber outer-cylinder.

(b) If possible, measure the temperature at the top of the cylinder (through the vent hole) at the aft part of the main fitting.

NLG Charging Valve - Detail and Location

(c) Slowly open the charging valve (2) with the M21930 FILLING ASSEMBLY.
(d) Slowly open the control valve (15) on the three-way valve (13). Read and record the pressure shown on the pressure gage (11).
(e) Close the control valve (15) on the three-way valve (13) and the charging valve (2) with the M21930 FILLING ASSEMBLY.
(f) Refer to the table and use the recorded temperature value to identify the correct charge pressure.

Pressure/Temperature Table - Shock Absorber Fully Extended

(g) If the recorded pressure value compares to the correct pressure +/- 0.5 bar (7 psi), no more action is necessary, go to step (7).
(h) If the pressure is incorrect, do step (6).
(6) Inflate the NLG shock absorber as follows:

CAUTION: ALWAYS ADD NITROGEN SLOWLY WHEN YOU PRESSURIZE THE SHOCK ABSORBER. IF YOU ADD THE NITROGEN TOO QUICKLY, THE TEMPERATURE WILL INCREASE AND HAVE AN EFFECT ON THE SHOCK ABSORBER PRESSURE.

(a) Slowly open the control valve (15) on the three-way valve (13).
(b) Slowly open the charging valve (2) with the M21930 FILLING ASSEMBLY.
(c) Slowly open the control valve of the nitrogen source. Adjust the charge pressure in the shock absorber to the correct value as recorded in step (5)(e).
(d) Close the control valve (15) on the three-way valve (13).
(e) Close the charging valve (2) with the M21930 FILLING ASSEMBLY.
(f) After the pressure has been adjusted, wait for a minimum of 15 minutes to let the pressure become stable.
(g) Slowly open the control valve (15) on the three-way valve (13) and the charging valve (2) with the M21930 FILLING ASSEMBLY. Do a check that the pressure read on the pressure gage (11) compares with the correct pressure +/- 0.5 bar (7 psi) as recorded in step (5)(e).
(h) If necessary, adjust the pressure to give the correct value.
(7) Remove the 98F32001006000 GEAR FILLING KIT S-ABSOR and M21930 FILLING ASSEMBLY as follows:
(a) Close the control valve (15) on the three-way valve (13).
(b) Close the charging valve (2) with the M21930 FILLING ASSEMBLY.
(c) Close the control valve of the nitrogen source.
(d) Slowly open the control valve (14) to release the pressure and remove the nitrogen source from the three-way valve (13).
(e) Remove the M21930 FILLING ASSEMBLY and the 98F32001006000 GEAR FILLING KIT S-ABSOR from the charging valve (2).
(8) TORQUE the charging valve nut (2) to between 0.8 and 0.5 m.daN (70.80 and 44.25 lbf.in )

.
(9) Use Testing Medium-Leak Detection - Oxygen System (Material No.14CCB6) to do a leak check of the charging valve (2).
(10) Install the blanking cap (1) on the charging valve (2).
(11) If the NLG shock absorber is fully deflated and inflated again:

Do a check of the NLG shock-absorber charging pressure between four and seven days after the first subsequent flight (Ref. AMM TASK 12-14-32-614-004).

NOTE: You must do the check of the NLG shock-absorber charging pressure because the nitrogen can be absorbed into the oil and the charge pressure can change.

Subtask 12-14-32-614-055-A

CAUTION: BE CAREFUL NOT TO DEFLATE THE SHOCK ABSORBER MORE THAN SPECIFIED IN THE PROCEDURE. IF YOU DEFLATE THE SHOCK ABSORBER TOO MUCH, HYDRAULIC FLUID CAN COME OUT OF THE SHOCK ABSORBER.

B. NLG Shock Absorber Nitrogen Filling - Aircraft on Wheels

NOTE: When the nitrogen fill is done with the aircraft weight-on-wheels, the aircraft must be stable. No persons must move in the aircraft during the fill task.

NOTE: When you fill the NLG shock absorber, you must use Individual Compound-- Nitrogen Gaseous (Material No.14VGC1) . This will make sure that the oxygen level stays low.

(1) Install the CHARGING EQUIPMENT - FLUID, STANDARD on the M21930 FILLING ASSEMBLY as follows:

NLG Charging Valve - Detail and Location

NLG Shock Absorber - Filling System

(a) Connect the nitrogen supply hose (16) to the nitrogen source.
(b) Connect the nitrogen supply hose (16) to the three-way valve (13).
(c) Connect the filling hose (12) to the three-way valve (13).

NOTE: The filling hose (12) length must not be more than 3 m (9.84 ft.).

(d) Remove the blanking cap (9) and the plug (3) from the M21930 FILLING ASSEMBLY.
(e) Connect the filling hose (12) to the end fitting (8) of the M21930 FILLING ASSEMBLY.
(f) Slowly open the control valves (14) and (15) on the three-way valve (13) and the control valve on the nitrogen source. Blow nitrogen through the charging equipment to bleed the system.
(g) Close the control valve on the nitrogen source.
(h) Close the control valves (14) and (15) on the three-way valve (13).

CAUTION: MAKE SURE THAT YOU USE A GAGE WITH THE SPECIFIED PRESSURE RANGE (0 BAR TO 200 BAR AND ACCURATE TO +/- 0.5 BAR). THIS IS NECESSARY TO GET AN ACCURATE PRESSURE MEASUREMENT.

(i) Install the applicable GAGE 200 BAR (2900 PSI) - PRESSURE, HYDRAULIC (11) on the three-way valve (13).
(2) Install the M21930 FILLING ASSEMBLY on the charging valve (2) as follows:

NLG Charging Valve - Detail and Location

(a) Remove the blanking cap (1) from the charging valve (2).
(b) Move the wrench (6) up to the knurled shoulder (7) and install the M21930 FILLING ASSEMBLY on the charging valve (2).
(c) Turn the core (4) of the M21930 FILLING ASSEMBLY clockwise with the knurled shoulder (7). This will install the seal (5) on the charging valve (2).
(3) Do a check of the charging equipment for leaks as follows:
(a) Make sure that the charging valve (2) and the control valve (14) on the three-way valve (13) are closed.
(b) Slowly open control valve (15) on the three-way valve (13).
(c) Use a THERMOMETER-SURFACE CONTACT to measure and record the temperature of the NLG shock absorber adjacent to the charging valve (2). Make sure that the thermometer surface contact touches the shock absorber outer-cylinder.

NOTE: If possible, measure the temperature at the top of the cylinder (through the vent hole) at the aft part of the main fitting.

NLG Charging Valve - Detail and Location

(d) Measure and record the shock absorber extension, dimension H.

NLG Shock Absorber - Dimension H ** ON A/C NOT FOR ALL

(e) Use the recorded dimension H and temperature values to identify the correct pressure for the shock absorber extension.

NLG Pressure/Extension Data (Weight on Wheels) - Positive Temperatures ** ON A/C NOT FOR ALL

NLG Pressure/Extension Data (Weight on Wheels) - Negative Temperatures ** ON A/C NOT FOR ALL

(f) Slowly open the control valve of the nitrogen source. Add nitrogen until the pressure read on the pressure gage is the same as the necessary charge pressure +/- 0.5 bar (7.3 psi).
(g) Close the control valve of the nitrogen source.
(h) After the pressure has been adjusted, wait for a minimum of five minutes to make sure that the pressure is stable. This will make sure that there are no leaks in the charging equipment.
(i) Close the control valve (15) on the three-way valve (13).
(4) Do a check of the NLG shock absorber charge pressure as follows:
(a) Use a THERMOMETER-SURFACE CONTACT to measure and record the temperature of the NLG shock absorber adjacent to the charging valve (2). Make sure that the thermometer surface contact touches the shock absorber outer-cylinder.

NOTE: If possible, measure the temperature at the top of the cylinder (through the vent hole) at the aft part of the main fitting.

NLG Charging Valve - Detail and Location

(b) Slowly open the charging valve (2) with the M21930 FILLING ASSEMBLY.
(c) Slowly open the control valve (15) on the three-way valve (13). Read and record the pressure shown on the pressure gage (11).
(d) Measure and record the shock absorber extension, dimension H.

NLG Shock Absorber - Dimension H ** ON A/C NOT FOR ALL

(e) Use the recorded pressure and temperature values to identify the correct dimension H for the shock absorber extension. Compare this value with dimension H you recorded in step (4)(d).

NLG Pressure/Extension Data (Weight on Wheels) - Positive Temperatures ** ON A/C NOT FOR ALL

NLG Pressure/Extension Data (Weight on Wheels) - Negative Temperatures ** ON A/C NOT FOR ALL

(f) If the recorded dimension H value compares to the correct dimension H +/- 10 mm (0.3937 in.), no more action is necessary, go to step (6).
(g) If dimension H is incorrect, do step (5).
(5) Inflate the NLG shock absorber as follows:

CAUTION: ALWAYS ADD NITROGEN SLOWLY WHEN YOU PRESSURIZE THE SHOCK ABSORBER. IF YOU ADD THE NITROGEN TOO QUICKLY, THE TEMPERATURE WILL INCREASE AND HAVE AN EFFECT ON THE SHOCK ABSORBER PRESSURE.

(a) Slowly open the control valve of the nitrogen source. Inflate the shock absorber with nitrogen until dimension H is correct as recorded in step (4)(e).
(b) Continue to inflate the shock absorber until the shock absorber extends by 30 mm (1.1811 in.) more.
(c) When the pressure has become stable, record the pressure shown on the pressure gage (11).
(d) Slowly open the control valve (14) on the three-way valve (13). Deflate the shock absorber until dimension H is correct as recorded in step (4)(e).

NOTE: Steps (b) thru (d) are to decrease the effect of the friction in the shock absorber on the measured value of dimension H.

(e) Close the control valve (15) on the three-way valve (13).
(f) Wait for a minimum of 10 minutes to let the pressure become stable in the shock absorber.
(g) Open the control valve (15) and measure and record the pressure on the pressure gage (11).
(h) Do a check that dimension H compares with the correct dimension H +/- 10 mm (0.3937 in.) as recorded in step (4)(e).
(i) If necessary, do steps (a) thru (h) again to adjust dimension H.
(6) Remove the CHARGING EQUIPMENT - FLUID, STANDARD and M21930 FILLING ASSEMBLY as follows:
(a) Close the control valve (15) on the three-way valve (13).
(b) Close the charging valve (2) with the M21930 FILLING ASSEMBLY.
(c) Close the control valve of the nitrogen source.
(d) Slowly open the control valve (14) to release the pressure and remove the nitrogen source from the three-way valve (13).
(e) Remove the pressure gage (11).
(f) Remove the M21930 FILLING ASSEMBLY and the CHARGING EQUIPMENT - FLUID, STANDARD from the charging valve (2).
(7) TORQUE the charging valve nut (2) to between 0.8 and 0.5 m.daN (70.80 and 44.25 lbf.in )

.
(8) Use Testing Medium-Leak Detection - Oxygen System (Material No.14CCB6) to do a leak check of the charging valve (2).
(9) Install the blanking cap (1) on the charging valve (2).
(10) If the NLG shock absorber is fully deflated and inflated again:

Do a check of the NLG shock-absorber charge pressure between four and seven days after the first subsequent flight (Ref. AMM TASK 12-14-32-614-004).

NOTE: You must do the check of the NLG shock-absorber charging pressure because the nitrogen is absorbed into the oil and the charge pressure can change.

5. Close-up
Subtask 12-14-32-410-051-A

A. Close Access

WARNING: MAKE SURE THAT THE TRAVEL RANGES OF THE LANDING GEAR ARE CLEAR.

(1) Make sure that the work area is clean and clear of tools and other items.
(2) Close the NLG doors (Ref. AMM TASK 32-22-00-410-001).

Subtask 12-14-32-942-056-A

B. Removal of Equipment
(1) Remove the SAFETY BARRIER(S).
(2) Remove the WARNING NOTICE(S).
(3) Remove the ACCESS PLATFORM 3M (10 FT) or the STEPLADDER 1.0 M (3.3 FT).
(4) Remove the ground support and maintenance equipment, the special and standard tools and all other items.

[Rev.10 from 2021] 2026.04.01 03:56:25 UTC