AMM A320F | Functional Check of MLG Shock Absorber Charge Pressure

REFERENCE	QTY	DESIGNATION
No specific	AR	ACCESS PLATFORM 3M (10 FT)
No specific	AR	CHARGING EQUIPMENT - GAS, STANDARD
No specific	AR	GAGE 150 BAR (2175 PSI) - PRESSURE, HYDRAULIC
No specific	AR	SAFETY BARRIER(S)
No specific	1	THERMOMETER -45 TO 70 DEG.C (-49 TO 158 DEG.F)
No specific	AR	WARNING NOTICE(S)
No specific	Torque wrench: range to between 0.11 and 0.06 m.daN (10 and 5 lbf.in )
No specific	Torque wrench: range to between 0.79 and 0.57 m.daN (69.91 and 50.44 lbf.in )
98F32001006000	1	GEAR FILLING KIT S-ABSOR

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

ZONE/ACCESS	ZONE DESCRIPTION
731	L.H MAIN GEAR
741	R.H MAIN GEAR

REFERENCE	DESIGNATION
TASK 07-11-00-581-001-A	Lifting for Aircraft Maintenance Operations
TASK 07-11-00-586-002-A	Lowering of the Aircraft for Maintenance Operations
TASK 12-12-32-611-004-A	Functional Check of MLG Shock Absorber Fluid Level
TASK 12-12-32-611-008-A	Hydraulic Replenishment of the MLG Two-Stage Shock Absorber
TASK 12-14-32-614-003-A	Functional Check of MLG Shock Absorber Charge Pressure
TASK 32-00-00-481-001-A	Installation of the Safety Devices on the Landing Gears
TASK 32-11-13-000-001-A	Removal of the MLG Shock Absorber
TASK 32-11-13-000-003-A	Removal of the MLG Shock-Absorber Gland-Seals
TASK 32-11-13-400-001-A	Installation of the MLG Shock Absorber
TASK 32-11-13-400-003-A	Installation of the MLG Shock-Absorber Gland-Seals
TASK 32-11-13-860-001-A	To Close the Spare-Seal Activating-Valve
MLG Two-Stage Shock-Absorber Charging Valves - Detail and Location ** ON A/C NOT FOR ALL
MLG Two-Stage Shock Absorber - Pressure/Extension Graph (Metric Units) ** ON A/C NOT FOR ALL
MLG Two-Stage Shock Absorber - Pressure/Extension Graph (Metric Units) ** ON A/C NOT FOR ALL
Possible Points of Leakage from the Gland Seals ** ON A/C NOT FOR ALL
Possible Points of Leakage from the Gland Seals ** ON A/C NOT FOR ALL
Details of the Spare-Seal Activating-Valve ** ON A/C NOT FOR ALL
MLG Two Stage Shock Absorber - Typical Filling System
MLG Two-Stage Shock Absorber - Pressure Extension Graph (Imp. Units) ** ON A/C NOT FOR ALL
MLG Two-Stage Shock Absorber - Pressure Extension Graph (Imp. Units) ** ON A/C NOT FOR ALL
Charging Pressures - Weight off Wheels ** ON A/C NOT FOR ALL
Charging Pressures - Weight off Wheels ** ON A/C NOT FOR ALL
MLG Two-Stage Shock-Absorber Charging Valves - Detail and Location ** ON A/C NOT FOR ALL
Possible Points of Leakage from the Gland Seals ** ON A/C NOT FOR ALL
Details of the Spare-Seal Activating-Valve ** ON A/C NOT FOR ALL
MLG Two-Stage Shock-Absorber Charging Valves - Location and Detail ** ON A/C NOT FOR ALL
Possible Points of Leakage from the Gland Seals ** ON A/C NOT FOR ALL

A. Safety Precautions
(1) Make sure that the ground safety locks are installed on the landing gear (Ref. AMM TASK 32-00-00-481-001).
(2) As necessary, use the applicable SAFETY BARRIERS, specified by the operator's instructions and your local regulations.
(3) On panel 400VU, make sure that the landing gear control-lever (6GA) is in the DOWN position.
(4) Put the WARNING NOTICE(S) in position to tell persons not to operate:

The landing gear controls
The landing gear doors.

(5) Put the ACCESS PLATFORM 3M (10 FT) in position below the applicable shock absorber.
(6) If the aircraft is on the ground, make sure that the wheel chocks are in position at the MLG wheels. Do not put a chock at the nose wheels.

A. Visual Inspection of the MLG Two-Stage Shock Absorber for Leakage of Hydraulic Fluid
(1) Before you do the check and/or charge the nitrogen:
(a) Examine the gland housing/sliding tube of the shock absorber for damage or leakage of the hydraulic fluid.
(2) If there is a leak from the gland housing and the sliding tube interface or from the gland housing and the main fitting interface:
(a) Examine the sliding tube for damage:
1 If there is damage, replace the shock absorber (Ref. AMM TASK 32-11-13-000-001) and (Ref. AMM TASK 32-11-13-400-001).
2 If there is no damage, do one of the steps that follows:

Replace the shock absorber gland-seals (Ref. AMM TASK 32-11-13-000-003) and (Ref. AMM TASK 32-11-13-400-003)
Replace the shock absorber (Ref. AMM TASK 32-11-13-000-001) and (Ref. AMM TASK 32-11-13-400-001)
Close the spare seal activating-valve (Ref. AMM TASK 32-11-13-860-001).

WARNING: MAKE SURE THAT THE AREA AROUND THE AIRCRAFT IS CLEAR OF PERSONS AND EQUIPMENT. WHEN YOU PRESSURIZE/DEPRESSURIZE THE SHOCK ABSORBER, WITH THE AIRCRAFT WEIGHT ON THE GROUND, THE AIRCRAFT WILL MOVE.

CAUTION: MAKE SURE THAT THE STANDARD CHARGING EQUIPMENT IS SAFE TO USE ABOVE 140 BAR (2030.5278 PSI). DO NOT USE EQUIPMENT WITH A SIGHT GLASS. THIS WILL PREVENT INJURY AND DAMAGE.

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.

CAUTION: MAKE SURE THAT YOU USE A GAGE WITH THE SPECIFIED PRESSURE RANGE. THIS IS NECESSARY TO GET AN ACCURATE PRESSURE MEASUREMENT.

B. Functional Check of the MLG Shock Absorber Charge-Pressure and Fill with Nitrogen (Aircraft on Ground)

MLG Two-Stage Shock-Absorber Charging Valves - Detail and Location ** ON A/C NOT FOR ALL

MLG Two-Stage Shock Absorber - Pressure/Extension Graph (Metric Units) ** ON A/C NOT FOR ALL

Possible Points of Leakage from the Gland Seals ** ON A/C NOT FOR ALL

Details of the Spare-Seal Activating-Valve ** ON A/C NOT FOR ALL

MLG Two Stage Shock Absorber - Typical Filling System ** ON A/C NOT FOR ALL

MLG Two-Stage Shock Absorber - Pressure Extension Graph (Imp. Units) ** ON A/C NOT FOR ALL

Charging Pressures - Weight off Wheels ** ON A/C NOT FOR ALL

NOTE: To do this procedure, it is necessary to use the CHARGING EQUIPMENT - GAS, STANDARD and the GAGE 150 BAR (2175 PSI) - PRESSURE, HYDRAULIC. The equipment must be safe to use at more than 140 bar (2031 psi).

NOTE: This procedure must be done a minimum of two hours after the last aircraft operation. This will make sure that the recorded shock absorber values are accurate.

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

(1) Measure and record dimension H.
(2) Install the first CHARGING EQUIPMENT - GAS, STANDARD on the top charging valve (1):

NOTE: If the equipment manufacturers assembly/operation instructions are different from the data given, use the equipment manufacturers instructions.

(a) Remove the blanking cap (2) from the top charging valve (1).
(b) Make sure that the control valves (23) and (25) are closed.
(c) Connect the filling hose (21) to the three-way valve (22).
(d) Connect the filling hose (21) to the top charging valve (1).
(e) Install the first pressure gage 140 bar (2031 psi) (20) on the three-way valve (22).
(3) Slowly open the top charging valve (1).
(4) At the top charging valve (1), read and record the pressure shown on the pressure gage.
(5) Close the top charging valve (1).
(6) Use the THERMOMETER -45 TO 70 DEG.C (-49 TO 158 DEG.F) to measure the temperature of the MLG adjacent to the top charging valve (1).
(7) Use diagram 1 to find dimension H for the pressure at the top charging valve (1) for the measured temperature.
(8) If measured dimension H is between +/- 15 mm (0.59 in.) of dimension H shown in diagram 1, do the steps that follow:

NOTE: Measured dimension H can be as low as 33 mm (1.30 in.) at very low ambient temperatures. This is usual for a shock absorber in good condition and no maintenance steps are necessary (if measured dimension H is between +/- 15 mm (0.59 in.) of the correct value).

(a) Make sure that the control valve (25) is closed.
(b) Open the control valve (23) to release all pressure from the filling hose (21).
(c) Close the control valve (23).
(d) Remove the pressure gage (20) from the three-way valve (22).
(e) Disconnect the filling hose (21) from the top charging valve (1) and the three-way valve (22).
(f) TORQUE the nut of the top charging valve (1) to between 0.79 and 0.57 m.daN (69.91 and 50.44 lbf.in )

.
(g) Use Testing Medium-Leak Detection - Oxygen System (Material No.14CCB6) to do a leak check of the top charging valve (1).
(h) Install the blanking cap (2) on the top charging valve (1).
(i) TORQUE the blanking cap (2) to between 0.11 and 0.06 m.daN (10 and 5 lbf.in )

.
(j) Do step (40).
(9) If measured dimension H is not between +/- 15 mm (0.59 in.) of dimension H shown in diagram 1 and is more than 33 mm (1.30 in.):

Do steps (11) thru (39).

(10) If measured dimension H is not between +/- 15 mm (0.59 in.) of dimension H shown in diagram 1 and is less than or equal to 33 mm (1.30 in.):
(a) Stop the procedure.
(b) Do the nitrogen filling procedure with the aircraft on jacks, refer to Para. 4.C.
(11) Install the second CHARGING EQUIPMENT - GAS, STANDARD on the bottom charging valve (3):

NOTE: If the equipment manufacturers assembly/operating instructions are different to the data given, use the equipment manufacturers instructions.

(a) Remove the blanking cap (4) from the bottom charging valve (3).
(b) Make sure that the control valves (23) and (25) are closed.
(c) Connect the filling hose (21) to the three-way valve (22).
(d) Connect the filling hose (21) to the bottom charging valve (3).
(e) Install the second pressure gage 140 bar (2031 psi) (20) on the three-way valve (22).
(12) Slowly open the top charging valve (1).
(13) At the top charging valve (1), read and record the pressure shown on the pressure gage (20).
(14) Close the top charging valve (1).
(15) Slowly open the bottom charging valve (3).
(16) At the bottom charging valve (3), read and record the pressure shown on the pressure gage (20).
(17) Close the bottom charging valve (3).
(18) Make sure that the pressure at the bottom charging valve (3) is 18 bar (261 psi) more than the pressure at the top charging valve (1). If not, do the steps that follow:

NOTE: This makes sure that the floating piston is at the top of the second stage cylinder before you do the nitrogen filling.

NOTE: It is possible that a small quantity of hydraulic fluid gets released from the bottom charging valve (3) when nitrogen is discharged.

(a) If the volume of fluid that flows from the bottom charging valve (3) is more than 0.6 l (0.16 USgal), do the steps that follow:
1 Do the hydraulic replenishment of the MLG two-stage shock absorber (Ref. AMM TASK 12-12-32-611-008).
2 Contact Airbus.
(b) Make sure that the control valves (23) and (25) are closed.
(c) Connect the nitrogen supply hose (24) to the three-way valve (22) which is connected to the bottom charging valve (3).
(d) Open the supply valve on the nitrogen source.
(e) Slowly open the control valve (25) to increase the nitrogen pressure at the bottom charging valve (3).
(f) Open the bottom charging valve (3).
(g) Make sure that the pressure at the bottom charging valve (3) is between 18 bar (261 psi) and 21 bar (305 psi) more than the pressure at the top charging valve (1).
(h) Close the control valve (25).
(i) After ten minutes (to let the pressure and temperature become stable), do a check if the condition at step (g) is the same.
(j) If it is not the same, do steps (e) thru (i) again.
(k) Close the bottom charging valve (3).
(l) Close the supply valve on the nitrogen source and remove the nitrogen supply hose (24) from the three-way valve (22).
(m) Slowly open the top charging valve (1).
(n) At the top charging valve (1), read and record the pressure shown on the pressure gage (20).
(o) Close the top charging valve (1).
(p) If the difference in pressure at the top charging valve (1) and the bottom charging valve (3) is less than 11 bar (160 psi), do steps (b) thru (o) again.
(19) Use the THERMOMETER -45 TO 70 DEG.C (-49 TO 158 DEG.F) to measure the temperature of the MLG adjacent to the top charging valve (1).
(20) Use diagram 2 to find dimension H for the pressure at the top charging valve (1) at the measured temperature.
(21) If measured dimension H is more than you found in diagram 2, do these steps:
(a) Open the top charging valve (1).
(b) Slowly open the control valve (23) to release some nitrogen.
(c) Immediately after the shock absorber starts to move, close the control valve (23).

NOTE: The pressure at the top charging valve (1) will decrease because nitrogen was removed without sufficient shock absorber movement.

(d) After five minutes, measure the pressure and use the THERMOMETER -45 TO 70 DEG.C (-49 TO 158 DEG.F) to measure the temperature at the top charging valve (1).
(e) Use diagram 2 to find dimension H necessary for the conditions found in step (d).
(f) Slowly open the control valve (23) to release some nitrogen.
(g) When dimension H is the same as you found in step (e) (+/- 2.0 mm (0.08 in.)), close the control valve (23).
(h) Close the top charging valve (1).
(22) If measured dimension H is less than the value you found in diagram 2, do these steps:
(a) Connect the nitrogen supply hose (24) to the three-way valve (22) which is connected to the top charging valve (1).
(b) Open the supply valve on the nitrogen source.
(c) Open the top charging valve (1).
(d) Slowly open the control valve (25) to add nitrogen.
(e) Immediately after the shock absorber starts to move, close the control valve (25).

NOTE: The pressure at the top charging valve (1) will increase because nitrogen was added without sufficient shock absorber movement.

(f) After five minutes, measure the pressure and use the THERMOMETER -45 TO 70 DEG.C (-49 TO 158 DEG.F) to measure the temperature at the top charging valve (1).
(g) Use diagram 2 to find dimension H necessary for the conditions found in step (f).
(h) Slowly open the control valve (25) to increase the nitrogen pressure.
(i) When dimension H is the same as you found in step (g) (+/- 2.0 mm (0.08 in.)), close the control valve (25).
(j) Close the top charging valve (1).
(23) After five minutes, open the top charging valve (1) and the bottom charging valve (3).
(24) Read and record:

The pressures at the top charging valve (1) and the bottom charging valve (3)
The temperature at the top charging valve (1) with the use of the THERMOMETER -45 TO 70 DEG.C (-49 TO 158 DEG.F)
Dimension H.

(25) Use the pressure and the temperature you measured at the top charging valve (1) to find correct dimension H in diagram 2. Make sure that dimension H in diagram 2 and dimension H found in step (24) are the same +/- 2.0 mm (0.08 in.).
(26) Do a check of the pressure you measured at the top charging valve (1) and at the bottom charging valve (3). Make sure that the difference between these pressures is more than 11 bar (160 psi).
(27) If the conditions at step (25) or step (26) are incorrect, do the procedure again from step (17).
(28) Close the top charging valve (1) and the bottom charging valve (3).
(29) To get the correct charge pressure at the bottom charging valve (3), do the applicable step (30) or (31).
(30) Refer to diagram 3. If the pressure at the top charging valve (1) is on or below the graph line (for the measured temperature), do these steps:
(a) Open the bottom charging valve (3).
(b) Slowly open the control valve (25) (to increase the nitrogen pressure), or slowly open the control valve (23) (to remove nitrogen).
(c) Make sure that the pressure at the bottom charging valve (3) is the same as the pressure shown on the graph line (for the measured temperature) +/- 1 bar (15 psi).
(d) Close these valves:

The bottom charging valve (3)
The control valve (25)
The control valve (23)
The supply valve on the nitrogen source.

(e) After five minutes, open the bottom charging valve (3). Make sure that the pressure at the bottom charging valve (3) is the same as the pressure shown on the graph line (for the measured temperature) +/- 1 bar (15 psi).
(31) Refer to diagram 3. If the pressure at the top charging valve (1) is above the graph line (for the measured temperature), do these steps:
(a) Close the supply valve on the nitrogen source.
(b) Open the bottom charging valve (3).
(c) Slowly open the control valve (23) to release some nitrogen.
(d) Immediately after the shock absorber starts to move, close the control valve (23).

NOTE: The pressure at the bottom charging valve (3) will decrease because nitrogen was removed without sufficient shock absorber movement.

(e) After five minutes, open the top charging valve (1).
(f) At the top charging valve (1), measure the pressure and use the THERMOMETER -45 TO 70 DEG.C (-49 TO 158 DEG.F) to measure the temperature.
(g) Close the top charging valve (1).
(h) Use diagram 1 to find dimension H necessary for the conditions at step (f).
(i) Slowly open the control valve (23) (to release nitrogen) until dimension H is the same as dimension H found in diagram 1, +/- 2.0 mm (0.08 in.).
(j) Close the bottom charging valve (3) and the control valve (23).
(k) After five minutes, open the top charging valve (1) and read and record the pressure.
(l) Close the top charging valve (1).
(m) Open the bottom charging valve (3) and read and record the pressure.
(n) Close the bottom charging valve (3).
(o) Make sure that the pressures at the top charging valve (1) and the bottom charging valve (3) are the same +/- 1.5 bar (22 psi). If the pressures are not in this limit, do the procedure from step (17) again.
(32) Remove the nitrogen supply hose (24) from the three-way valve (22).
(33) Remove the filling hoses (21) from the charging valves (1) and (3).
(34) TORQUE the nuts of the charging valves (1) and (3) to between 0.79 and 0.57 m.daN (69.91 and 50.44 lbf.in )

.
(35) Use Testing Medium-Leak Detection - Oxygen System (Material No.14CCB6) to do a leak check of the top charging valve (1) and the bottom charging valve (3).
(36) Install the blanking cap (2) on the top charging valve (1).
(37) Install the blanking cap (4) on the bottom charging valve (3).
(38) TORQUE the blanking caps (2) and (4) to between 0.11 and 0.06 m.daN (10 and 5 lbf.in )

.
(39) Remove the pressure gages (20) and the filling hoses (21) from the three-way valves (22).
(40) Do this procedure again for the other shock absorber.

NOTE: Frequent nitrogen filling of the MLG shock absorber can be an indication of low oil level. Record all nitrogen servicing work in the aircraft log. This will let you monitor if the fluid level check procedure is necessary (Ref. AMM TASK 12-12-32-611-004).

(41) If the MLG shock absorber is fully deflated and inflated again:

Do a check of the MLG shock-absorber charging pressure between four and seven days after the first subsequent flight (Ref. AMM TASK 12-14-32-614-003).

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