In Service Information
Ref.: ISI 29.00.00173
Issue: July 2017
Single
Aisle Family
A318/A319/A320/A321
Hydraulic system
Maintenance practices
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
Single Aisle Family
maintenance practices
_
A318 / A319 / A320 / A321
HYDRAULIC SYSTEM
Purpose:
This booklet provides a summary of the maintenance
practices related to the hydraulic system. The purpose
of this booklet is to provide a quick reference guide
to line maintenance.
Contents:
1. Simplified schematics003
2. Reasons and solutions for system failures009
3. Installation/Removal & Repairs027
4. Necessary tools for hydraulic system061
001
002
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
A320 Family maintenance practices
_
Please note:
These instructions do not amend or supersede any
information contained in the Aircraft Maintenance Manual.
This booklet will not be updated and the AMM remains
the principle reference.
This booklet is not a repair guide.
For additional information refer to:
AMM references:
• 12-12-29 PB 301
• 12-14-29 PB 301
• 12-32-29 PB 301
• 20-21-12 PB 201
• 20-23-11 PB 201
• 20-23-14 PB 201
• 20-23-21 PB 201
• 20-23-22 PB 201
• 20-29-00 PB 201
• 29-00-00 PB 201
• 29-00-00 PB 601
• 29-10-00 PB 201
• 29-19-00 PB 001
1. Simplified schematics
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
1. Simplified schematics
_
005
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
1. Simplified schematics
_
007
2. System Maintenance
Procedures
2.1
2.2
2.3
2.4
Air in hydraulic system
Hydraulic reservoir servicing
Hydraulic fluid sampling
External leaks
010
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. System Maintenance Procedures
_
2.1 Air in Hydraulic System
AMM 29-00-00 PB 201
Background:
Air in the hydraulic system has a negative impact
on the components reliability and can generate:
• Water hammer effect
Flow/pressure quick fluctuations affecting the hydraulic
installation and components.
• Engine Driven Pump or hydraulic system low pressure
warnings pressure decreases when air arrives at pump.
• Reservoir low level warning
When arriving in the reservoir the air is separated from
the hydraulic fluid resulting in reservoir level decrease.
Low pressure indications
Low level indications
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
Root causes
Air can be introduced in the system when a leak occurs,
or during maintenance operation, or because of hydraulic
accumulator defective bladder.
Solution
In case of doubt, an easy check can allow to make sure
that the amount of air contained in the hydraulic system
is within acceptable range (chapter 2.1.1).
2.1.1. Check for air in hydraulic system
Please refer to AMM TASK 29-00-00-210-001-A
• Ensure the reservoir pressure is 50 psi by checking the
pressure gage located on the top of the hydraulic reservoir.
If necessary, pressurize the reservoir and read the gage
of the corresponding reservoir and record the fluid level.
• Depressurize the hydraulic system and wait for 5 minutes
to read the gage of the corresponding reservoir again
and record the fluid level.
• Make the difference between both levels.
Acceptable level difference values are:
- 2 L on the Green hydraulic system
- 1 L on the Blue hydraulic system
- 1.5 L on the Yellow hydraulic system.
• If more level fluctuation is noted, bleed the related hydraulic
system as per AMM 29-00-00 PB 201. Select the most
appropriate procedure (Bleeding of the related Hydraulic
System with or without the Ground Power Cart).
Note: If the source of air contamination is due to previous leak
or heavy maintenance, no further immediate action is recommended.
If not, it is likely that air is mainly introduced in the hydraulic system
by the hydraulic system accumulator (one accumulator per system).
011
012
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. System Maintenance Procedures
_
2.1 Air in Hydraulic System
2.1.2. Leak check of pressure on hydraulic power
accumulators AMM TASK 29-10-00-200-008-A
• Ensure the hydraulic systems are depressurized.
• Check if the system accumulator pressures are correct
(see table hereafter):
Check of System Accumulators pressure
T° (°C)
T° (°F)
P (psi)
P (bars)
-10
14
1 620
112
0
32
1 710
118
10
50
1 800
124
20
68
1 890
130
30
86
1 970
136
If the pressures are not correct, continue as follows:
1. If the accumulator pressure is less than 15 bar below
the correct pressure “P”, adjust the pressure as necessary
as per AMM TASK 12-14-29-614-001.
WARNING: ADJUST THE PRESSURE ONLY IF THE MPD TASK
INTERVAL (600 FH OR 6 MO) IS RESPECTED. IF YOU DO NOT ,
YOU CAN MISS AN ACCUMULATOR DAMAGE BECAUSE OF TOO
FREQUENT INSERTION OF AIR IN THE HYDRAULIC SYSTEM.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. If the accumulator pressure is more than 15 bar below
the correct pressure “P”, do the following steps:
a) Adjust the accumulator pressure to the correct nominal
value “P” (AMM TASK 12-14-29-614-001).
b) After 20 minutes, do a check of the accumulator pressure:
- If the accumulator pressure has the correct value “P”,
plus/minus 7 bar, no more steps are necessary
- If the accumulator pressure is 7 bar or more above
the correct value “P”, reduce the accumulator
pressure to the correct value “P”
- If the accumulator pressure is 7 bar or more below
the correct value “P”, do a leak check of accumulator
nitrogen charging circuit using Material N°14CCB6
on the gas manifold of the accumulator.
Example of nitrogen leak
on A320 Family Hydraulic
Accumulator
c) If leaking component is found, replace it (accumulator,
gage, charging valve or manifold).
d) If no external leak is found :
- Replace the accumulator as per
AMM TASK 29-1X-42-X00-001-A
013
014
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. System Maintenance Procedures
_
2.2 Hydraulic reservoir servicing
Background:
In many cases, in-service experience shows a need of hydraulic
reservoir adjustment due to an incorrect reservoir servicing.
Root causes
The hydraulic reservoir level can be influenced by:
• Air in the Hydraulic System
• Temperature
• Consumer position
2.2.1. Check of the hydraulic reservoir fluid level
AMM 12-12-29 PB 301
• Ensure the aircraft is in the correct
configuration:
- Speed Brakes and Spoilers retracted
- Thrust Reversers stowed
- LG extended with doors closed
- Reservoir pressurised
- Cargo doors closed
- Brake Accumulator filled
For further information, please refer
to ISI 29.00.00021.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2.2.2. Fill the hydraulic reservoir
• Monitor the increase of the fluid level of the related
system on the quantity indicator and do these steps:
1. Stop the flow of the hydraulic fluid when the pointer
is almost to the fill level (refer to picture above).
2. Slowly continue to fill again, until the pointer shows almost
to the fill level (refer to picture above).
CAUTION: MAKE SURE THAT YOU DO NOT PUT TOO MUCH
FLUID IN THE RESERVOIR. IF THE RESERVOIR IS TOO FULL,
YOU CANNOT PRESSURIZE IT SUFFICIENTLY. LOW AIR PRESSURE
CAN CAUSE THE MESSAGE “RSVR LO AIR PR” TO SHOW IN FLIGHT
ON THE UPPER AND LOWER ECAM DISPLAY UNITS
Please take into account :
Fill level ≠ Total reservoir volume
≠ Maximum gaugeable level
Total volume: 10L
Max gaugeable: 8L
Fill level (at 20°C): 6L
Low level warning: 2L ± 0.3L
Total volume: 23L
Max gaugeable: 18L
Fill level (at 20°C): 14L
Low level warning: 3L ± 0.4L
Total volume: 20L
Max gaugeable: 18L
Fill level (at 20°C): 12L
Low level warning: 3L ± 0.4L
Note: The hydraulic fluid volume in the reservoirs can change with
the temperature. For each 10 DEG.C scale Celsius change in outside
air temperature:
•T
he volume in the Green or Yellow hydraulic system reservoir can
change by 0.5 L
• The volume in the Blue hydraulic system reservoir can change by 0.25 L
015
016
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. System Maintenance Procedures
_
2.3 Hydraulic Fluid Sampling
Background:
Hydraulic fluid contamination has a negative impact on hydraulic
line and component reliability. Hydraulic fluid condition has to be
monitored in accordance with MPD TASK 29-1000-15-1 interval.
In case of contamination, AMM 12-32-29 PB 301 requires
immediate corrective actions that can lead to additional
grounding time.
In-service experience shows that most of contamination
issues are particle related often due to incorrect
sampling (refer to OIT 999.0048/14). It is therefore
necessary to strictly follow AMM 12-32-29 PB 301
recommendations when collecting fluid samples.
Possible root causes of fluid contamination
A. Particle contamination
• Contaminated fluid from ground cart
Cart fluid condition has to be monitored
on a periodical basis.
• Component internal wear
Internal leak test as per AMM 29-19-00 PB 001 will allow
identification and replacement of faulty component.
• Maintenance operation on the hydraulic circuit
• Incorrect fluid sampling
AMM 12-32-29 PB 301 recommendations to be strictly
followed (chapter 2.3.1).
Refer to AMM 12-32-29 PB 301 flowchart for correctives
actions.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
B. Chemical contamination
As for particle, chemical contamination can be introduced by:
• Contaminated fluid used for reservoir servicing or
from the ground cart maintenance incorrect sampling
In service experience show that most of chemical
contamination issues are water or acid related.
Water can also be introduced from hydraulic reservoir
pressurization circuit. The acid accretion is the result
of combination of hydraulic fluid and water in high
temperature environment.
Possible corrective actions in case of chemical
contamination (refer to AMM 12-36-29 PB 301):
• Complete fluid replacement
• Replacement of fluid in the reservoir for acid only
• Use of PALL Purifier for water and chlorine.
Note:
PALL Purifier is also particle filter.
017
018
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. System Maintenance Procedures
_
2.3 Hydraulic Fluid Sampling
2.3.1. Hydraulic fluid sampling procedure
AMM 12-32-29 PB 301
CAUTION: DO NOT FORGET TO PRESSURIZE THE APPLICABLE
HYDRAULIC SYSTEM BEFORE PERFORMING THE HYDRAULIC
FLUID SAMPLING.
• Carefully clean the hydraulic sampling valve
with Methyl-Ethyl-Ketone (Material 08BBF1).
• Use a container of 1L to flush 0.2 L of the fluid sampling
valve (AMM Subtask 12-32-29-680-050-A) and discard it.
• Put the clean poly-ethylene bottle and collect 0.2 L
(0.052 USGAL) for analysis.
CAUTION: DO NOT USE A CONTAINER/BOTTLE MADE OF PVC.
THIS MATERIAL WILL EFFECT THE RESULTS FOR THE HYDRAULIC
FLUID SAMPLE.
Please refer to AMM TASK 12-32-29-281-001-A
for the complete procedure
Particles can be accumulated in the lower
part of the manifold.
0.2 L Fluid need to be discarded
to have representative sample.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2.4 External leaks
Background: several leaks, leakages or stain have been
experienced in service.
2.4.1.Check of hydraulic components external leaks
AMM TASK 29-00-00-790-001-A
If the inspection reveals a total failure of hydraulic system
and an EDP continuous running for more than 10 min,
please:
• Pressurize the failed hydraulic system
• Perform the leak test.
1. Operate the component for the time or number
of cycles necessary.
2. Stop the operation of the component and compare
the amount of leakage with the maximum permitted
values given in the following table.
Note:
The table that follows is applicable only for Green, Yellow and Blue
Hydraulic Systems. It is not applicable for Alternate-Braking
Low-Pressure System.
019
020
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. System Maintenance Procedures
_
2.4 External leaks
2.4.2.Hydraulic leakage - Maximum permitted values
Refer to AMM TASK 29-00-00-790-001-A
Equipment
Location
Normal
Operation
Limit
Dispatch limit
to avoid delay
(See Note 6)
HYD PUMPS
(EDP, EMP,
RAT)
Static Seals
(at unions and
connections)
None
2 drops in 10 min
Static Casing
(Housing)
1 drop in 10 min
1 drop/min
Shaft Seal
(System
pressurized)
2 drops/min
8 drops/min
EDP: 5 drops/min
EDP: 60 drops/min
EMP: 5 drops/min
EMP: 30 drops/min
RAT: 1 drop/min
RAT: 1 drop/min
PTU: 5 drops/min
PTU: 30 drops/min
Shaft Seal
(In operation)
(See Note 6)
SERVO
CONTROL
Elevator,
Aileron,
Rudder,
Spoiler &
Yaw Damper
(See Note 4)
Static Seals
(System
pressurized)
None
2 drops in 10 min
Elevator:
6 drops in 10 min
(See Note 1)
Dynamic Seal
(System
pressurized)
1 drop in 10 min
Aileron:
6 drops in 10 min
(See Note 1)
Rudder:
30 drops/min
Spoiler:
30 drops/min
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
Equipment
SERVO
CONTROL
Elevator,
Aileron,
Rudder,
Spoiler &
Yaw Damper
(See Note 4)
ACTUATORS
LG Actuator,
LG Door
Actuator &
Cargo Door
Actuator
(Note 7)
Location
Normal
Operation
Limit
Dispatch limit
to avoid delay
Elevator:
3 drops in 10 cycles
(See Note 1)
Dynamic Seal
(In operation)
1 drop in 10 cycles
Aileron:
3 drops in 10 cycles
(See Note 1)
Rudder:
15 drops/cycle
Spoiler:
15 drops/cycle
(See Note 6)
Static Seals
None
2 drops in 10 min
Rod Seal
(System
pressurized)
1 drop/min
30 drops/min
Rod Seal
(In operation)
1 drop/cycle
2 drops/cycle
(See Note 6)
CONNECTIONS
Removable
Pipe to Pipe
None
2 drops in 10 min
(See Note 2)
Permanent
Pipe to Pipe
None
None
Swivel fitting
None
30 drops/min
Manifold
Fitting
None
2 drops in 10 min
(See Note 2)
Bobbins
None
2 drops in 10 min
(See Note 2)
Removable
Pipe to Pipe
None
2 drops in 10 min
(See Note 2)
Sliding unions
Slight leakage
1 drop in 10 min
(See Note 2)
021
022
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. System Maintenance Procedures
_
2.4 External leaks
Equipment
Normal
Operation
Limit
Location
Dispatch limit
to avoid delay
(See Note 6)
OTHER
(Distributor,
Unlocking
Jack)
Static Seals
None
2 drops
in 10 min
Dynamic Seal
(System pressurized)
None
1 drop/min
Hyd Motor Shaft Seal:
Slats, Flaps, THS
(pressurized and
in operation)
5 drops/min
30 drops/min
Constant Speed
Motor/Generator
1 drop/min
6 drops/min
Alternate Brake System
(See Note 3)
(See Note 3)
Brake Unit (at rest)
None
None
Brake Unit
(pressure applied)
1 drop/min
2 drops/min
(See Note 5)
Ground Leakage Measurement Manifold (at rest)
2 drops/day
4 drops/day
Ground Leakage
Measurement Manifold
(system pressurized)
1 drop
in 5 cycles
2 drops
in 5 cycles
Ground Leakage Measurement Manifold (after pressurization and operation)
1 drop
in 15 min
2 drops
in 15 min
Hand Pumps (Cargo
Doors, RSVR Filling)
5 drops/min
30 drops/min
Priority Valves
None
2 drops
in 10 min
Manual Selector Valve
2 drops per
100 operations
2 drops/10 min
Hydraulic Accumulator
nitrogen charging-circuits
None
None
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
Note1:
For the elevator and the aileron servo-controls, two leaks of more
than the normal operation limit are not permitted on the same flight
surface.
Note2:
It is mandatory that the connection is tight and the correct torque
value is applied.
Note3:
It is mandatory that no component or connection in the alternate
brake system (such as the safety valves, manifold, etc.) have leaks
which are more than 10 drops per minute.
Note4:
Obey the leakage limits for the Yaw Damper Servo-Actuators:
• If the leakage rate is less than 4 drops per minute , no more steps
are necessary
• If the leakage rate is between 4 and 14 drops per minute, replace
the yaw damper
servo-actuator(s) before the subsequent 750 flight hours
• If the leakage rate is between 15 and 30 drops per minute, replace
the yaw damper
servo-actuator(s) before the subsequent 100 flight hours
• If the leakage rate is more than 30 drops per minute, replace
the yaw damper servo-actuator(s) immediately
• Do the visual inspection of the yaw damper servo actuators
with the part number SC4700-3
Note5:
A leak rate of 10 drops per minute is permitted, if the temperature
is less than -40 deg.C (-40.00 deg.F).
023
024
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2. System Maintenance Procedures
_
2.4 External leaks
Note6:
If one or more components have an external leak rate that is more
than the normal operation limit, the aircraft can be dispatched if:
• The leak rate of the component(s) is less than the dispatch limit
• Only one hydraulic system has component(s) with a leak rate that
is more than the normal operation limit
• For a given hydraulic system, the leakage is less than the dispatch
limit
• The fluid level in the hydraulic reservoirs is correct. It is necessary
to do the above checks again before each flight.
Note7:
The limit of 2 drops in 10 min is for the time of the pressurization
and operation of the Cargo Door.
Note8:
The following fittings; PERMASWAGE, HARRISON elastomerically
swaged, HARRISON internal roller-swaged, EATON, RYNGLOCK,
CRYOFIT couplings and H-fittings are swaged permanent connections.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
2.4.3. How dispatch with hydraulic leak?
Leakage
Report to Airbus
Refer to AMM
29-00-00 PB 601
Leak
within limits?
A/C
dispatch
under MEL?
Leaking
component
replacement possibility?
Repair
possibility?
Replacement
Repair
AMM 20-23-11
Contact AIRTAC
DISPATCH
025
026
Single Aisle Family Hydraulic system - Ref.: SEE34/951.1497/99 - Feb 2016
3. Installation/Removal
& Repairs
3.1 Hydraulic tubing repairs
3.2 Permitted damage and defects
3.2 Repair of hydraulic tubing
3.3 Tightening practices for hydraulic
connections
3.4 Removal/installation of the bobbins
and of O-rings on plug-in unions
(or manifold plugs)
028
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
Please refer to manufacturer instructions for:
• Engine tubes
• Landing gear tubes.
3.1 Hydraulic tubing repairs
AMM 20-23-11 PB 201
Note:
These hydraulic repairs are applicable only to tubes located
in airframe area:
• Titanium alloy (Ti 3Al 2.5V) tubes (ABS5004) ; sizes -04 to -16
• CRES (21-6-9) tubes (ASNA3288) ; ALL sizes
• Aluminium alloy (6061-T6) tubes (ASNA3410 or DAN40) ;
sizes -04 to -16 and -24.
Usually, tube repair is carried out with a tube made of the same
material, but if this is not available, the tube can be repaired
as follows:
• Aluminum alloy (6061-T6) tubes, ref. ABS5144 or
ASNA3410 or DAN40:
with Corrosion-Resistant Steel (CRES) (21.6.9) tubes,
ref. ASNA3288 or titanium alloy (Ti A3L 2.5V) tubes,
ref. ABS5004
• CRES (21.6.9) tubes, ref. ASNA3288:
with titanium alloy (Ti A3L 2.5V) tubes, ref. ABS5004
(but not in the pylon)
• Titanium alloy (Ti A3L 2.5V) tubes, ref. ABS5004:
with CRES (21.6.9) tubes, ref. ASNA3288.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
Method Name
Tube
Material
Parts part number
AMM task
Harrison 2 grooves
6061-T6
21-6-9
Union NSA855010 or ABS1369
Sleeve NSA855034
Nut MS21921 or ASNA3769
AMM TASK 20-23-11-300-002-A
Harrison 3 grooves
Ti 3Al 2.5V
Union ASNA3760
Sleeve ASNA3759
Nut MS21921 or ASNA3769
AMM TASK 20-23-11-300-003-A
H-fitting
6061-T6
21.6.9
Ti 3Al 2.5V
36011VXX
AMM TASK 20-23-11-300-004-A
Cryofit
6061-T6
21-6-9
Ti 3Al 2.5V
3PHS111-XX
AMM TASK 20-23-11-300-006-A
MS21922 Sleeve
6061-T6
21-6-9
MS21922
AMM TASK 20-23-11-300-005-A
T.I.G
welding procedure
21-6-9
Ti 3Al 2.5V
Filler metal:
Z2 CND 20-10-3
T40 or AMS4951
AMM TASK 20-23-11-300-008-A
029
030
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.1 Hydraulic tubing repairs
* Permaswage fittings
AMM TASK 20-23-11-300-001-A
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
031
032
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.1 Hydraulic tubing repairs
* Rynglock fittings
AMM TASK 20-23-11-300-007-A
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3.1.1. Temporary/Permanent repair
A. Titanium Tubes
P: Permanent, T: Temporary, - : Not Applicable.
Material
HP or LP lines
Titanium Alloy Ti-3Al-2.5V (ABS5004)
In situ
HP lines
-4
Size
Thickness (inch)
-6
-8
-10
-12
-16
0,016 0,019 0,026 0,032 0,039 0,051
Permaswage Unions
AMM 20-23-11-300-001
Y
P
P
P
P
P
P
Harrison elastomer
AMM 20-23-11-300-002
N
-
-
-
-
-
-
Harrison Roller
AMM 20-23-11-300-005
N
P
P
P
P
P
P
Rynglok R8
AMM 20-23-11-300-007
Y
P
P
P
P
P
P
Cryofit
AMM 20-23-11-300-006
Y
P
P
P
P
P
P
H-fitting
AMM 20-23-11-300-003
Y
P
P
P
P
P
P
MS21922 sleeve
AMM 20-23-11-300-004
Y
-
-
-
-
-
-
Welding
AMM 20-23-11-300-008
N
T
T
T
T
T
T
Hoses
AMM 20-23-11-300-009
Y
T
T
T
T
T
T
033
034
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.1 Hydraulic tubing repairs
3.1.1. Temporary/Permanent repair
B. CRES Tubes
P: Permanent, T: Temporary, - : Not Applicable.
Material
HP or LP lines
Stainless Steel 21-6-9 (ASNA 3288)
In
situ
Size
Thickness (inch)
HP lines
-4
LP lines
-6
-8
-10
-12
-16
-20
-24
0,016 0,02 0,026 0,033 0,039 0,051 0,024 0,024
Permaswage Unions
AMM 20-23-11-300-001
Y
P
P
P
P
P
P
P
P
Harrison elastomer
AMM 20-23-11-300-002
N
P
P
P
P
P
P
P
P
Harrison Roller
AMM 20-23-11-300-005
N
-
-
-
-
-
-
-
-
Rynglok R8
AMM 20-23-11-300-007
Y
P
P
P
P
P
P
P
P
Cryofit
AMM 20-23-11-300-006
Y
P
P
P
P
P
P
P
P
H-fitting
AMM 20-23-11-300-003
Y
P
P
P
P
P
P
-
-
MS21922 sleeve
AMM 20-23-11-300-004
Y
T
T
T
T
T
T
T
T
Welding
AMM 20-23-11-300-008
N
T
T
T
T
T
T
-
T
Hoses
AMM 20-23-11-300-009
Y
T
T
T
T
T
T
T
T
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
C. Aluminium Alloy Tubes
P: Permanent, T: Temporary, - : Not Applicable.
Material
HP or LP lines
Aluminium Alloy 6061-T6 (ASNA3410/DAN40)
In
situ
Size
Thickness (inch)
LP lines
-4
-6
-8
-10
-12
-16
-24
0,035 0,035 0,035 0,035 0,035 0,048 0,035
Permaswage Unions
AMM 20-23-11-300-001
Y
P
P
P
P
P
P
P
Harrison elastomer
AMM 20-23-11-300-002
N
P
P
P
P
P
P
P
Harrison Roller
AMM 20-23-11-300-005
N
-
-
-
-
-
-
-
Rynglok R8
AMM 20-23-11-300-007
Y
P
P
P
P
P
P
P
Cryofit
AMM 20-23-11-300-006
Y
P
P
P
P
P
P
P
H-fitting
AMM 20-23-11-300-003
Y
P
P
P
P
P
P
-
MS21922 sleeve
AMM 20-23-11-300-004
Y
T
T
T
T
T
T
T
Welding
AMM 20-23-11-300-008
N
-
-
-
-
-
-
-
Hoses
AMM 20-23-11-300-009
Y
T
T
T
T
T
T
T
035
036
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.1 Hydraulic tubing repairs
3.1.2. Protection Against Vibration
and Chafing of Hydraulic Pipes
Please refer to AMM TASK 20-23-14-910-001-A
A. Minimum Distances Necessary to Prevent
Chafing of Hydraulic Pipes
• Measure the distance in the condition where the movement
decreases the distance to its smallest value to know
the minimum distance between a pipe/hose and a part
that can move and compare with the figure below.
Distances mini between
pipes/hoses and Structure
Minimum distance:
6 mm (023 in.) for rigid pipe
12 mm (0.47 in. for flexible hose
Distances mini between pipes/hoses
and parts that
Minimum distance:
can move
6 mm (023 in.) for rigid pipe
12 mm (0.47 in. for flexible hose
Movement
Movement
Distances mini between
individual pipes
A Mini
ITEM
For pipes in the same routing
For pipes in the different routings
Between two hoses
Between a hose and a pipe
A Mini
mm in.
2.5 (0.1)
6 (0.23)
12 (0.47)
12 (0.47)
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
B. P
rotection from Vibration and Chafing
for Hydraulic pipes
When the clearance is less than the minimum distance,
lacing tapes, bumpers, spacers and clamps can be used:
• To get the minimum distance
• To prevent chafing.
Note:
Hydraulic pipes shall not be attached to pipes of other systems
or electrical harnesses.
1. Installation of lacing tape on pipe runs.
Minimum distance
• 2.5 mm (0.0984 in.) min. for pipes in the same routing
• 6 mm (0.2362 in.) min. for pipes in different routings.
Identification mark
Minimum distance
037
038
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.1 Hydraulic tubing repairs
2. Installation of bumpers and spacers between pipes.
Install bumpers or spacers to prevent vibration and chafing:
• When the distance between fixed clamps is too long
• To maintain a minimum distance between two pipes.
Identification
mark
Adhesive
sealant
Cable tie
NSA935401
Identification
mark
Adhesive
sealant
Cable tie
NSA935401
Bumper NSA5586
Spacer NSA5527
3. Installation of spiral strip
If a pipe is too close to a fixed part (distance less than
5 mm (0.1969 in.), you can install a spiral strip attached
with a cable tie at each end on the tube to prevent damage.
This method is not applicable for parts that can move.
Cable tie
NSA935401
Spiral tie
NSA849000
If distance
< 5mm (0.19 in.)
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
4. Installation of grommets ABS0648
Outer part
Structure
Grommet
ABS0648
Nose
Inner
part
CORRECT
INCORRECT
After correct installation, the pipe can move approximately
15 Deg. in each direction.
5. Installation of clamps or lacing tape
to prevent chafing of pipes
Clamp NSA5516
Identification
mark
Clamp
NSA5516
Clamp installation
Adhesive sealant
Lacing tape
Adhesive sealant
on the tightened knot
and the ends of the
lacing tape
Identification mark
Lacing tape installation
Spacer
NSA5527
Examples of
clamp positions
039
040
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.2 Permitted Damage and Defects
3.2.1. Permitted Damage and Defects
on Hydraulic Tubes
Please refer to AMM TASK 20-23-11-200-001-A
for the complete procedure.
A. Typical damages
TYPE A
D
TYPE B
Outside Diameter
D
Tube wall thickness
DAMAGE TYPE A
(with a maximum tube deformation
without material removal)
DAMAGE TYPE B
(with a maximum material removal
on the tube surface)
Without time limit
With time limit
Without time limit
With time limit
• D < OD x 1%
• For ABS5004 Size
-16: D < OD x 1.4%
• D <1.5 x OD
• Damage must be
in the straight pipe
area, not in bend
• D < 5% of
the Tube wall
thickness
• D< 20% of the
tube wall thickness
• Damage must be
in the straight pipe
area, not in bend
Outside Diameter Dash Outside Diameter (OD)
mm
in.
-4
6.35
1/4
-6
9.53
3/8
-8
12.7
1/2
-10
15.88
5/8
Outside Diameter Dash Outside Diameter (OD)
mm
in.
-12
19.5
3/4
-16
25.4
1”
-20
31.75
1” 1/4
-24
38.1
1” 1/2
• For thickness tubes values, refer to
AMM Figure 20-23-00 PB 001 or chapter 3.1.1 Table.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
B. S
pecial Cases
1. For Special Case of ASNA3760 Union and ASNA3759
Sleeve, please refer to AMM Subtask 20-23-11-210-061-A
2. For Special Damage Criteria of Fire-Protection Sleeves,
on Pipes in the Pylon Area, please refer to AMM Subtask
20-23-11-210-064-B
3.2.2. Permitted Damage and Defects
on Hydraulic Hoses
Please refer to AMM TASK 20-23-11-200-003-A
Note:
When the damage or defects on the flexible hoses are more than
the permitted limits given below, flexible hoses have to be replaced.
A. Permitted limits for signs of impact and surface defects
Note:
Surface defects are discontinuities such as:
• Scratches
• Bends
• Cracks and forging laps • Corrosion pits
• Scores
• Nicks
a) Replace the flexible hose if you find:
• Surface defect with signs of dents, kinks or deformation
• Two or more wires in one plait or a number of wires
are broken in one small area.
• The metal braid hose has wear or chafing on the metal braid
that is more than the maximum permitted wear damage
(see *formula next page).
041
042
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.2 Permitted Damage and Defects
• The hose has a fire sleeve protection (brown neoprene
overlay-protection) and there is wear or chafing
on the fire sleeve protection.
• The hose has a chafe guard protection (blue colour)
and the wear or chafing on the metal braid is more
than the maximum permitted wear damage (see *formula).
b) If there is wear after chafing (on the metal braid):
• Find and remove the root cause of chafing before
the next flight.
• Replace the flexible hose if the wear width
is more than 10% of the hose circumference:
Measure the width of the wear (W) and the external diameter
of the hose (D) (see figures below).
*Fomula: Maximum permitted wear damage:
If W x 100 / D x 3.14 > 10, replace the flexible hose
Chafing area
D
W
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3.3 Tightening practices for hydraulic connections
3.3.1. Lubrication
Please refer to AMM Subtask 20-23-11-917-001-A
A. L
ightly lubricate with Material N 02ABA1 or 03LDA1:
• Only on the male thread
• The shoulder of the sleeve (when possible).
Note:
Do not apply lubricant on the contact surfaces between the sleeve
and the sealing surface of the fitting. Lubricant can cause the pipe
to turn when torquing the sleeve nut.
B. Remove unwanted lubricant with a clean, dry lintfree cloth.
Fitting
Nut
Sleeve
Tube
Lubricate the male
Thread
Do not lubricate this area
(contact surface between
the sleeve and the sealing
surface of fitting)
Lubricate
the sleeve shoulder
(when possible)
043
044
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.3 Tightening practices for hydraulic connections
3.3.2. Tightening torque application
• Find the correct torque value.
Note:
It is important to know the material and the parts dimensions
of the assembly. If the connection has different materials,
torque value has to be used for the weakest material.
• Get the applicable torque wrench and the wrench
adapter for the nut and an applicable second wrench
to apply the countertorque to the fitting (for our tool
set recommendations, refer to chapter 4 - Tool Set).
Use calibrated torque wrench & counter wrench
• Set the torque wrench to the applicable value. When using
a wrench adapter, value has to be adjusted (chapter 3.3.6).
• Put the torque wrench in position on the sleeve nut
and the countertorque wrench on the fitting
(refer to figures on following pages).
• Apply a slow and continuous force on the torque wrench
until you reach the set torque value.
Note:
The double tightening torque is not applicable for the installation
of plug-in fittings installed on manifold or equipment.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
• Apply a double tightening on the union
(refer to AMM Subtask 20-23-11-917-060-A).
• Torque the clamp blocks to 0.2 m.daN (17.70 lbf.in).
AMM 20-21-12 PB 201
Hold
Typical Harrison connection
Sleeve nut
Sleeve
Hold the union with
a second wrench and
tighten the sleeve nut
to the applicable torque
value (chapter 3.3.3.).
Tube
Tube
Tighten
Red
paint
Sleeve nut
Union
Nut
Typical Permaswage connection
Sleeve
Hold the union with a second
wrench and tighten the sleeve
nut to the applicable torque
value. (chapter 3.3.3.).
Hold
Tighten
045
046
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.3 Tightening practices for hydraulic connections
3.3.2. Tightening torque application
In-line Check Valve Connection
Removal union or
in-line check valve
Sleeve nut
Tighten
Sleeve nut
Hold
Tighten
Hold the union with a second wrench and tighten the sleeve
nut to the applicable torque value (chapter 3.3.3.).
Flexible Hose Connection
Fitting
Hose
sleeve nut
Hold
Tighten
Hose hexagonal Fitting (fixed)
Hold the hose hexagonal fitting with a second wrench and
tighten the hose sleeve nut to the applicable torque value
(chapter 3.3.3.).
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
Plug-in union Connection
Plug-in union
Equipment
Tighten
First tighten the plug-in union to the applicable
torque value (chapter 3.3.4.).
Hold
Sleeve nut
Equipment
Plug-in union
Tighten
Then hold the plug-in union with a second wrench
and tighten the sleeve nut to the applicable
torque value (chapter 3.3.3.).
047
048
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.3 Tightening practices for hydraulic connections
3.3.2. Tightening torque application
Straight Bulkhead Connection
Hold
Hold
Locknut
Locknut
Special Bulkhead
fitting swaged
on the tube
Union
Tighten
Tighten
First, hold the union with a second wrench and tighten
the locknut to the applicable torque value (chapter 3.3.5.).
Tighten
Hold
Tighten
Hold
Sleeve nut
Sleeve nut
Special Bulkhead
fitting swaged
on the tube
Sleeve
nut
Tighten
Then hold the union with a second wrench and tighten
the sleeve nut to the applicable torque value (chapter 3.3.3.).
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
90° Angle Bulkhead Connection
Tighten
Hold
Elbow union
Hold
Sleeve nut
Locknut
(not tightened)
Tighten
First, hold the swivel union with a second wrench and tighten
the sleeve nuts to the applicable torque value (chapter 3.3.3.).
Elbow union
Hold
Locknut
Tighten
Then hold the swivel union with a second wrench and tighten
the locknut to the applicable torque value (chapter 3.3.5.).
049
050
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.3 Tightening practices for hydraulic connections
3.3.3. Tightening Torques for HARRISON and
PERMASWAGE In-line Couplings, Check Valves,
Hoses and Caps/Plugs, the two Parts made
of CRES or Titanium
AMM 20-21-12 PB 201
Tightening Torques
Item
code
3
Outer DIA
Cres and Titanium Tubes
in.
mm
m.daN
Ibf in.
m.daN
Ibf in.
3/16
4.76
1.1
97
1.2
106
Mini
Maxi
4
1/4
6.35
1.5
133
1.7
150
5
5/16
7.93
2.0
177
2.3
204
6
3/8
9.52
2.9
257
3.2
283
8
1/2
12.70
5.4
478
5.9
522
10
5/8
15.87
7.5
664
8.3
735
12
3/4
19.05
8.5
752
9.5
840
16
1”
25.40
8.5
752
9.5
840
20
1” 1/4
31.75
8.5
752
9.5
840
24
1” 1/2
38.10
8.5
752
9.5
840
Note:
If one of the constituents is made of aluminum,
(union, sleeve or nut), apply the aluminum alloy values.
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3.3.3. Tightening Torques for HARRISON and
PERMASWAGE In-line Couplings, Check Valves,
Hoses and Caps/Plugs, one
of the Parts made of Aluminium-Alloy
AMM 20-21-12 PB 201
Tightening Torques
Item
code
3
Outer DIA
Aluminium alloy
in.
mm
m.daN
Ibf in.
m.daN
Ibf in.
3/16
4.76
-
-
-
-
Mini
Maxi
4
1/4
6.35
1.2
106
1.3
115
5
5/16
7.93
1.5
133
1.7
150
6
3/8
9.52
1.8
159
2.0
177
8
1/2
12.70
3.0
266
3.3
292
10
5/8
15.87
3.9
345
4.3
381
12
3/4
19.05
4.8
425
5.3
469
16
1”
25.40
8.1
717
8.9
788
20
1” 1/4
31.75
9.7
859
10.7
947
24
1” 1/2
38.10
9.7
859
10.7
947
Note:
If one of the constituents is made of aluminum,
(union, sleeve or nut), apply the aluminum alloy values.
051
052
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.3 Tightening practices for hydraulic connections
3.3.4. Tightening Torques for Plug-in Unions, MS Unions
and Plug-in Check Valves (the two Parts made
of Steel)
Tightening Torques
Item
code
3
Outer DIA
Cres
in.
mm
m.daN
Ibf in.
m.daN
Ibf in.
3/16
4.76
2.20
195
2.31
204
Mini
Maxi
4
1/4
6.35
3.34
296
3.44
304
5
5/16
7.93
3.34
296
3.44
304
6
3/8
9.52
4.47
396
4.57
404
8
1/2
12.70
7.85
695
7.95
704
10
5/8
15.87
11.24
995
11.35
1 005
12
3/4
19.05
14.00
1 239
14.24
1 260
16
1”
25.40
18.53
1 640
18.75
1 660
20
1” 1/4
31.75
20.22
1 790
20.45
1 810
24
1” 1/2
38.10
20.80
1 841
21.00
1 859
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3.3.4. Tightening Torques for Plug-in Union and Plugin
Check Valves, One of the Parts made
of Aluminum-Alloy
Tightening Torques
Item
code
3
Outer DIA
Aluminium alloy
in.
mm
m.daN
Ibf in.
m.daN
Ibf in.
3/16
4.76
0.83
73
0.94
83
Mini
Maxi
4
1/4
6.35
1.21
107
1.32
117
5
5/16
7.93
1.21
107
1.32
117
6
3/8
9.52
1.63
144
1.75
155
8
1/2
12.70
3.47
307
3.58
317
10
5/8
15.87
5.03
445
5.14
455
12
3/4
19.05
7.29
645
7.40
655
16
1”
25.40
11.64
1 030
11.86
1 050
20
1” 1/4
31.75
13.44
1 190
13.67
1 210
24
1” 1/2
38.10
14.10
1 248
14.30
1 266
053
054
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.3 Tightening practices for hydraulic connections
3.3.5. Tightening Torque Values for Bulkhead Lock Nuts
on all CRES Components
AMM 20-21-12 PB 201
Item
code
Bulkhead
Connection
Tube Outer
DIA ref.
in.
mm
3
3/16
4.76
4
1/4
5
5/16
6
Tightening Torques
Lock
Nut
Thread
CRES
Mini
Maxi
m.daN
Ibf in.
m.daN
Ibf in.
0.3750-24
2.20
195
2.31
204
6.35
0.4375-20
3.34
296
3.44
304
7.93
0.5000-20
3.34
296
3.44
304
3/8
9.52
0.5625-18
4.47
396
4.57
404
8
1/2
12.70
0.7500-16
7.85
695
7.95
704
10
5/8
15.87
0.8750-14
11.24 995
11.35 1 005
12
3/4
19.05
1.0625-12
14.00 1 239
14.24 1 260
16
1”
25.40
1.3125-12
18.53 1 640
18.75 1 660
20
1” 1/4 31.75
1.6250-12
20.22 1 790
20.45 1 810
24
1” 1/2 38.10
1.8750-12
20.80 1 841
21.00 1 859
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3.3.5. Tightening Torque Values for Bulkhead Lock Nuts,
one of Part Made of Aluminium-Alloy
AMM 20-21-12 PB 201
Item
code
Bulkhead
Connection
Tube Outer
DIA ref.
in.
mm
3
3/16
4.76
4
1/4
5
5/16
6
Tightening Torques
Lock
Nut
Thread
Aluminium alloy
Mini
Maxi
m.daN
Ibf in.
m.daN
Ibf in.
0.3750-24
0.83
73
0.94
83
6.35
0.4375-20
1.21
107
1.32
117
7.93
0.5000-20
1.21
107
1.32
117
3/8
9.52
0.5625-18
1.63
144
1.75
155
8
1/2
12.70
0.7500-16
3.47
307
3.58
317
10
5/8
15.87
0.8750-14
5.03
445
5.14
455
12
3/4
19.05
1.0625-12
7.29
645
7.40
655
16
1”
25.40
1.3125-12
11.64 1 030
11.86 1 050
20
1” 1/4 31.75
1.6250-12
13.44 1 190
13.67 1 210
24
1” 1/2 38.10
1.8750-12
14.10 1 248
14.30 1 266
055
056
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.3 Tightening practices for hydraulic connections
3.3.6. Torque wrench adapter
B
Crow-foot
wrench adapter
Torque wrench
B
Open end
wrench
adapter
A
B
When using a wrench adapter, adjust the torque value
in accordance with the bellow formula:
T’ = T x A
A+B
T’= new torque value (adjusted)
to be set on the torque wrench
T = specified torque value
(applied on the connection)
Example:
• Specified Torque (T) = 2 m.daN (177 lb.in)
• Length of torque wrench
(A) without adapter = 300 mm (11.8 in.)
• Length of adapter (B) = 100 mm (3.9 in.)
• Torque value to read off T’:
T’ = (2 m.daN x 300 mm)/(300 + 100 mm) = 1.5 m.daN
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3.3.7. Unions Red Marking in Hydraulic Systems
AMM 20-23-22 PB 201
After hydraulic connection torque, identification
has to be carried out with a red painted line:
• To identify a tightened union.
• To show possible loosening of the union.
Procedure (AMM TASK 20-23-22-910-001-A)
CAUTION: BEFORE YOU DO THIS PROCEDURE, MAKE SURE
THAT YOU HAVE TIGHTENED THE RELATED UNION TO THE
RELATED UNION TO THE APPLICABLE TORQUE VALUE
AND DONE THE APPLICABLE LEAKAGE TEST.
1. Use Material 15SBA1 and Material 08BAA9 made moist
with Non Aqueous Cleaner-General to clean the surfaces
where make marks will be present.
Note: If a new installation has to be performed, it is necessary
to remove the remaining red line before a new red line application.
2. Paint one line with a width of 2 mm (0.0787 in.)
to 4 mm (0.1575 in.) on the union and the nut
with a Material 04SAB2 (red color). Let it dry.
Note: The union marking is not applicable in the fuel tanks.
3. Apply Material No. 12ACB1 on
the cadmium-plated steel union.
Red marking
057
058
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.4 Removal/installation of the bobbins and
of O-rings on plug-in unions (or manifold plugs)
Note:
Plug-in unions and bobbins are equipped with elastomeric seals
(O-Rings or Square seals) which must be replaced.
3.4.1. Overall precautions
• Do not use pointed, sharp or metal tools to remove
the O-ring. Use spoon-type removal tool or wedge
type removal tool with a hook.
CORRECT
Pull
Push
INCORRECT
Spoon type
Wedge type
• Before installation, lubricate O-ring,
square seal for at least 15 minutes with material
N° 02ABA1 (Phosphate Ester Hydraulic Fluid)
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3.4.2. Removal/installation on O-rings installed for
plug-in unions, check valves or manifold plug
Please refer to AMM TASK 20-29-00-911-002-A
Use tool PN 98A29103000XXX to install O-rings.
O-RING (NAS 1602 or NAS 1612)
or O-RING (EN 6075 or EN 6076)
1
PUSH
2
3.4.3. Removal/ installation of hydraulic bobbins
Please refer to AMM TASK 20-23-21-911-001-A
Note:
Instead of O-ring and square seal removal/installations, please note
that bobbin assembly NSA8687 can be installed.
Leakage can occur if insufficient care is taken during
Installation/Removal of the bobbins.
• Use tool PN 97A29102090XXX for:
- Removal/Installation of the bobbin
- Installation of the O-ring and square seals on the bobbins.
• Before the installation, make sure that the references
of the parts you install on the bobbin are:
- Manifold side (bobbin identification groove side)
* O-ring: NAS1611-xx or NAS1601-xx
* Back up ring: NSA8671-xx
- Component side:
* Square seal: NSA8213-xx
* Back up ring: NSA8674-xx
(see figure here after).
059
060
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
3. Installation/Removal & Repairs
_
3.4 Removal/installation of the bobbins and
of O-rings on plug-in unions (or manifold plugs)
3.4.3. Removal/ installation of hydraulic bobbins
Back-up ring
NSA 8674
Component side
Manifold side
Component
O-Ring
Groove
Bobbin
Manifold
Square
seal
Back-up ring
NSA 8671
• Install the back-up rings in the grooves
before you install the seals.
4. Necessary tools
for hydraulic system
Tool set
062
Single Aisle Family In Service Information - Ref.: ISI 29.00.00173
4. Tool set
_
Tool name
PN Tool
In situ
Repair swaging
tool kit
DLT series or D12000
series tools
In situ
Rynglock tooling
RTSTx or RTSTxR Tool
Inst/Rem Bobbin
Tool set
97A29102090000
Torque Tool Set
98F29003000000
Fluid material
02ABA1
Red Marking
04-SAB2
Seal Tool Set
98A29103000000
Tool Picture
AIRBUS S.A.S. 31707 Blagnac Cedex, France
© AIRBUS S.A.S. 2016 - All rights reserved, Airbus, its
logo and the product names are registered trademarks.
Concept design by Airbus Multi Media Support 20171311.
Photos by Airbus: P. Masclet.
Printed in France by Airbus Print Centre.