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TITLE:

AIRCRAFT PNEUDRAULICS, 141 pages (slides)

SLIDE TOPICS, SUBTOPICS and CONTENTS:

AIRCRAFT PNEUDRAULICS
FM 1-509
TM 1-1500-204-23-2
ELO A Identify The Fundamentals Of Pneudraulics
FUNDAMENTALS OF PNEUDRAULICS (FM 1-509 p 1-1)
FUNCTIONS OF HYDRAULICS
1. Operate landing gear
2. Wheel brakes
3. Loading ramps
4. Starting engines
5. Flight control systems
ADVANTAGES OF HYDRAULICS (FM 1-509 p 1-1)
High efficiency
High degree of dependability
Self lubricating
Low in maintenance
Flexibility of installation
Low weight
Low in space requirements
Very sensitive to operator control
QUALITIES OF HYDRAULIC FLUIDS (TM 1-1500-204-23-2, p 2-1)
Incompressibility
Expansion and contraction
Pressure transmission
The use of Air/Nitrogen in a hydraulic system.
GASES IN HYDRAULIC SYSTEMS TM 1-1500-204-23-2, p 2-4
Types of gases used:
Air- most common
Nitrogen (safe substitute for atmospheric air)
Common use:
Accumulators
Shock struts
Emergency equipment
GENERAL ADVANTAGES Air/Nitrogen TM 1-1500-204-23-2, p 2-4
Acts like a spring
Lighter than a spring
No metal fatigue
Expands indefinitely
No dependant shape
Reacts against forces
TYPES OF HYDRAULIC FLUIDS TM 1-1500-204-23-2, p 2-4
GENERALLY CLASSIFIED AS

Vegetable Base

Petroleum Base Synthetic Base
HYDRAULIC FLUIDS Vegetable Base
Vegetable base fluid: is readily distinguished by its bluish color and will deteriorate synthetic rubber seals used in systems designed for petroleum or synthetic based fluids.
HYDRAULIC FLUIDS Petroleum Base MIL-H-6083
Petroleum Base MIL-H-6083: Is used as a preservative oil for spare parts, and for testing and flushing for some components.

It should not be used in operational aircraft hydraulic systems.

HYDRAULIC FLUIDS Petroleum Base MIL-H-5606
Petroleum Base MIL-H-5606: Is being phased out for most Army aircraft, and is being replaced with synthetic MIL-H-83282. However, it is still used for cold weather operations in some geographic locations..

Also, some self contained components are still using MIL-H-5606 due to the low viscosity of the fluid (i.e. stabilizer bar dampers, M/R dampers, shock struts, etc.).

HYDRAULIC FLUIDS Synthetic Base MIL-H-83282
Synthetic Base MIL-H-83282: is replacing
MIL-H-5606 in most operations due to the higher flash point, as well as the additives which provide better resistance to corrosion and oxidation.
MIL-H-83282 is a fire retardant fluid.
HYDRAULIC FLUID PRECAUTIONS TM 1-1500-204-23-2, p 2-6
Use proper fluid - Consult tech manuals-data plate-color of fluid

Drained fluid: Contaminated

Disposition of containers: Destroyed
FLUID CONTAMINATION TM 1-1500-204-23-2, p 2-6
Contamination in a hydraulic system is the presence of any material other than the hydraulic fluid being used. This includes water, metal, dust and any other foreign matter.
Contamination sources may be internal or external.
FLUID CONTAMINATION
Internal contamination: can cause abnormal wear on the pump or other components. Moving seals and dirty filters can cause internal contamination.
External contamination: is generally caused by poor maintenance practices such as leaving hydraulic lines uncapped, and using dirty rags.
DETECTING CONTAMINATION
Kit: NSN 6630-00-150-6486
Components: check every time a unit is removed, disassembled, replaced, or repaired.
Filters: normal contamination checks are made by examining the condition of the filter elements.
FLUID CONTAMINATION TM 1-1500-204-23-2, p 2-6
Flushing: Evidence of contamination makes it necessary that the hydraulic system be flushed with the proper fluid and discarded after use.
FLUID CONTAMINATION TM 1-1500-204-23-2, p 2-4
Accidental servicing: In the event that a system or component is inadvertently serviced with incorrect type of fluid, flush the system and replace all packings and gaskets in the affected system.
CONTAMINATION PREVENTION TM 1-1500-204-23-2, p 2-6
Cap or plug open connections.
Never use dirty rags.
Clean and deburr new tubing and fittings before installing them.
Store new or overhauled parts in sealed containers.
Fill pumps prior to installation.

CONTAMINATION PREVENTION
Taking care of test stands and GSE.
Careful handling of flexible hoses.
Hydraulic fluid drained for any reason shall not be reused.
Hydraulic fluid containers shall be destroyed when emptied.
Do not use previously opened cans of hydraulic fluid.
Flash Point / Fire Point
CONVERSION OF HYDRAULIC FLUIDS TM 1-1500-204-23-2 p 4 - 167

MIL-H-5606:

Temperature limits: -65 degrees F to 275 degrees F.
Flash point: 200 degrees F.
Accident or combat incurred fires.

CONVERSION OF HYDRAULIC FLUIDS TM 1-1500-204-23-2, p 4-167
MIL-H-83282 / Fire Retardant
Operational temperature limits:
400F.
Flash point: 400 degrees F.

Compatible with systems using
MIL-H- 5606.
CONVERSION OF HYDRAULIC FLUIDS
Note: Presence of MIL- H-5606 in amounts exceeding 3% by volume will compromise the fire resistance performance of MIL-H-83282.
CONVERSION OF HYDRAULIC FLUIDS
MIL-H-5606 to MIL-H-83282: Purge to 380 degrees F. Check applicable aircraft maintenance manual.

MIL-H-83282 to MIL-H-5606: Drain and fill system.


OPERATING TEMPERATURE LIMITS
MIL-H-83282 works well under normal temperature; as temperate decreases, viscosity increases.
The minimum ambient operating temperatures are shown in Table 4-45 of TM1-1500-204-23-2. Pg.4-169.
OPERATING TEMPERATURE LIMITS
Caution: cold weather operation of the hydraulic systems should be operated very slowly until the operating temperature of the fluid has warmed up. This will help prevent abnormal wear on the seals within the system.
RESISTANCE FM 1-509, p 1-3
Resistance to liquid flow occurs due to the viscosity of the fluid and from the flow of the fluid through the tubing.

Aircraft hydraulic systems have been designed to consider this loss of energy by reducing the resistance as much as possible
COMPUTING FORCE, AREA AND PRESSURE
FORCE AREA AND PRESSURE TM 1-1500-204-23-2, p 2-1
F = FORCE (push or pull exerted against the total area of a surface, and is expressed in pounds).
A = AREA (expressed in square inches)
P = PRESSURE (amount of push or pull on a square inch, expressed in psi).
FORCE AREA AND PRESSURE


F = P X A P =
FORCE-AREA-PRESSURE
Force: 6000 lbs.

Area: 2 sq. inches

Pressure: 3000 psi
Example:
3000 psi x 2 sq. in.= 6000 lbs.
P x A = F
COMPUTATION OF VOLUME, AREA, AND LENGTH OF STROKE TM 1-1500-204-23-2, p 2-2
Volume: measurement of quantity expressed in cubic inches
Area: surface measurement expressed in square inches
Length of stroke: measurement of distance expressed in inches
COMPUTATION OF VOLUME, AREA, AND LENGTH OF STROKE

PASCAL’S LAW TM 1-1500-204-23-2, p 2-2
When force is applied to a confined liquid, pressure is transmitted equally and undiminished in all directions throughout the liquid.
Pascal’s law applies to all confined liquids regardless of the shape of the container in which confined.
PASCAL’S LAW
Practical application of hydraulic principles are based on Pascal’s law which may be stated in simple terms.
MECHANICAL ADVANTAGE
Mechanical advantage is defined as the use of small force over a great distance to obtain a great force over a short distance.
Mechanical Advantage
TRANSMISSION OF PRESSURE BY LIQUIDS
10 lbs. force
ELO B Identify the plumbing, tubing and hoses, fittings, repairs, seals and gaskets in hydraulics.
HYDRAULIC PLUMBING TM 1-1500-204-23-2, p 4-1
Tubing used in aircraft hydraulic systems carries pressure to distant points in the aircraft to provide control of various critical components. Failure of the tubing will result in pressure loss and subsequent loss of control.
TYPES OF TUBING
Corrosion Resistant Steel: MIL-T-8504 and MIL-T-6845 is used in high pressure hydraulic systems (3000 psi) such as landing gear, wing flaps, brakes and nose wheel power-steering to prevent damage from flying gravel, stones, heat or ground handling accidents.
TYPES OF TUBING
Aluminum alloy tubing: WW-T-700/1 is used for general purpose lines and conduits of low pressure used in other fluid pressure instruments.

5052-0 or WW-T-700/4 is used for reduced pressure up to (1500 psi max) and return lines.

6061 and 6062 MIL-T-7081 may be used for high pressure (3000 psi).

WW-T-700/1 and WW-T-700/6 shall not be used in hydraulic systems.
TUBING SIZES (FM 1-509), p 2-1
Outside diameter in 1/16ths of an inch, the dash number on the tubing indicates the size.
Example: -8=8/16ths or 1/2in.

Wall thickness is specified in thousandths of an inch.
Example: .040 wall thickness.
IDENTIFICATION OF TUBING
Preferred method: printed symbolized tape system 204-23-1, para 6-3 & 204-23-2, p 4-1.

Alternate method: the solid color band method (paint). Not used on army aircraft.
COLOR CODED TAPE Pg. 6-4 TM 204-1
TUBING DAMAGE TM 1-1500-204-23-2, p 4-1
Dents: dents less than 20% of the diameter is not objectionable unless in the heel of a short bend radius.

Nicks: no deeper than 15% of the wall thickness.

Heel of bends: tubing which is nicked in the heel of a bend should be replaced if carrying over 100 psi pressure.
TUBE CUTTING TM 1-1500-204-23-2, p 4-2
Tube cutter preferred.

Hack saw blade with 32 teeth per inch.

All tubing shall be deburred before it is flared.
Chipless Cutter
Tubing Cutter
TUBE BENDING TM 1-1500-204-23-2, p 4-2
Bending tool with radius blocks.

Fusible alloy federal specification QQ-F-
838.
Tubing Bender
Use of the Tubing Bender
TUBE FLARING TM 1-1500-204-23-2, p 4-6
Single flaring: single flaring is used for tubing joints on all sizes of steel tubing

6061 aluminum alloy and 5052 aluminum alloy above 1/2 inch outside diameter.

Double flaring: used on 5052 aluminum alloy 1/2 inch diameter or less.
FLARING TOOLS
Aviation flares are made at a 74 degree included angle. Automotive flaring tools are designed to be made at 90 degree included angles, and are not to be used on aviation tubing at any time.
Tube Flaring Tool
TUBE CLEANING AND TESTING
After tubing is bent and ends flared, the tube will be thoroughly cleaned prior to installation in the aircraft.
All tubing will be tested prior to installation on the aircraft.
FITTINGS AN/MS TM 1-1500-204-23-2, p 4-14
Hydraulic Fittings: used throughout the hydraulic system to provide simple connections between hydraulic components and tubing.
Standard MS (flareless) and AN (flared) fittings are used in army aircraft. Both types are made in many different shapes, sizes, and designs.
AN / FLARED TYPE FITTING
In the manufacture of tube assemblies, an AN 18-8 nut and MS20819 sleeve are used with the flared end of the tube. Size is given as a dash number which equals the tubing outside diameter in sixteenths of an inch.

Example: AN18-8 equals 8 over 16 or 1/2 inch inside diameter of the nut. MS 20819-4 equals 4 over 16 or 1/4 inch.
MS / FLARELESS FITTING TM 1-1500-204-23-2, p 4-15
MS fittings are used to connect tubing which doesn’t require flaring.
MS fittings have a counterbore in which the tube end is installed. The counterbore has a 24 degree bevel which causes the tube connector sleeve to seal the connection as the tube B-nut is tightened.
MS fittings are sized by the dash number, the same as with AN fittings.
INSTALLATION OF AN / FLARED TUBING
Tube assembly shall be cleaned.
Sleeve and nut shall be screwed to mating fitting by hand and tightened with the proper wrench.
Tubing is not to be pulled into place by the nut.
Over-tightening nuts may severely damage or completely cut off the tubing flare.
INSTALLATION OF AN / FLARED TUBING
Under-tightening nuts may also be serious, as this may allow tubing to blowout or leak at the fitting.
Use a torque wrench.
Maximum torques are shown in table 4-2 of TM 1-1500-204-23-2
INSTALLATION OF MS / FLARELESS FITTINGS
MS fittings must be inspected before installation. All lines should be flushed with the proper hydraulic fluid and be bench tested before installation.
Lubricate the threads and the sleeve before installation.
Hand-tighten the nuts without excessive strain on the line.
INSTALLATION OF MS/FLARELESS FITTINGS
Tighten one flat past initial resistance of B-nut. Pressurize the system and inspect for leaks.
If leaks are noted, release system pressure and completely loosen the B-nut. If possible rotate the sleeve to a new position and then retorque the B-nut to its original position plus one flat.
INSTALLATION OF MS/ FLARELESS FITTINGS
If leaks are still present replace the assembly.
Do not tighten more than two flats.
REPAIR OF TUBING TM 1-1500-204-23-2, p 4-30
Repair: the damaged portion is cut out, a new piece of tubing and unions are installed to accomplish the repair.

Replacement: remove damaged tubing to use as a template for the manufacture of a new assembly. Duplication of bends, lengths and angles will be as close as possible.
SWAGED TUBING REPAIRS TM 1-1500-204-23-2, p 4-87
Permaswage: fittings mechanically swaged onto the tube by a hydraulically operated tool. Fittings are available in many configurations to include unions, elbows, tees, and crosses. These fittings can be flared of flareless depending on the need.
This repair method is not to be used on heat treated steel or 5052 aluminum.
SWAGED TUBING REPAIRS
Hydraulically operated tool normally located within the AVIM.
Repairs can be either on or off the aircraft depending on your need.
Repairs are permanent.
PERMASWAGE
SHOW MOVIE
FLEXIBLE HOSE TM 1-1500-204-23-2, p 4-32
Flexible Hose: is used in aircraft plumbing to connect moving parts with stationary parts in locations subject to vibration or where a great amount of flexibility is needed.
It can also serve as a connector in metal tubing systems.
Flexible hose is measured in sixteenths of an inch inside diameter (i.d.).
TYPES OF FLEXIBLE HOSES
Rubber hose:

1. Medium pressure up to 1500 psi.

2. High pressure up to 3000 psi.

3. Bulk identification is stenciled along the full
length of hose with manufacture code, date,
size, and specification of the hose.
TYPES OF FLEXIBLE HOSE TM 1-1500-204-23-2, p 4-55
Teflon Hose:

Teflon hose has a flexible, leak proof inner tube reinforced with one or more layers of stainless steel braid depending on the intended operating pressure.

It offers an unlimited shelf life in contrast to that of rubber hose. Teflon hose should never be bent so as to kink the hose which causes permanent damage.
QUICK DISCONNECT COUPLINGS FM 1-509, p 3-16
These couplings are installed at locations where frequent uncoupling of lines is required for inspection and maintenance.

QUICK DISCONNECT COUPLINGS
Consists of two halves held together by a union nut.
Self sealing
Spring used to close valves
Prevents loss of fluid
Prevents the entrance of air
PACKINGS AND O-RINGS TM 1-1500-204-23-2, p 4-79
Used throughout the system to prevent internal and external leakage of hydraulic fluid.
Seals used between non-moving parts are called gaskets.
Seals inside a sliding or moving part are called packings.
SEALS AND PACKINGS*
1. “O”- RING
2. BACK-UP RING 3. “V” - RING 4. “U” - RING 5. CUP SEALS 6. OIL SEALS (GARLOCK)
7. WIPERS/ SCRAPERS
PG 3-1
PAC KINGS AND O-RINGS IDENTIFICATION
O-RINGS: O-rings are manufactured according to technical information on the individual package they come in.

STORAGE: O-rings are kept in individual packages unopened, away from direct light and away from heat. They should be used on a rotational basis.
PACKINGS AND O-RINGS IDENTIFICATION
KZ5330-833-7491 PACKING PREFORMED SYNTHETIC RUBBER
1 EACH(MS28778-5) DISC-38329
A-5/80
SR 810-B-90
MFD DATE 4-80; CURE DATE 2Q84
STILLMAN RUBBER CO. (MFGR/CONTR) MIL-G-5510A
*IMPORTANT: KEEP O-RINGS IN ORIGINAL PACKAGE*
PACKINGS AND O-RINGS WARNING
O-ring splicing and O-ring assortment kits do not meet the specific requirements for o-ring usage on aviation equipment and are not authorized for use on army aircraft.

Use of unauthorized o-rings may compromise the integrity and safety of equipment and personnel.
PACKINGS AND O-RINGS INSTALLATION
Installation: Immerse rings in hydraulic fluid prior to installation.
Install carefully to prevent nicking or cutting of the seal.
Use protective measures when installing seal over threaded areas.
INSPECTION OF LINES AND HOSES
CRACKS
LEAKS
KINKS
CHAFING
SCRATCHES
LOOSE ANCHORS
ELO C Identify hydraulic components, functions, and types.

RESERVOIRS TM 1-1500-204-23-2, p 4-102
RESERVOIR TYPES
RESERVOIR OPERATION In-Line
Reservoir with Baffles, Fins, and Finger Strainer
F divided by A = P
HYDRAULIC CHECK VALVES
Check Valves p 4-127
HAND PUMPS
POWER PUMPS
Mechanically Driven
Engine
Transmission
Electric Motors
Pistons used for high pressure and long life.
Types - Variable Delivery -Constant Delivery or both.

CONSTANT VOLUME
VICKERS STROKE REDUCTION NO FLOW
VICKERS STROKE REDUCTION FULL FLOW
KELLOGG STROKE REDUCTION
Drive Coupling Shear Shaft
Fluid Filter Assembly FM 1-509, p 5-1 & TM 1-1500-204-23-2 p 4-106
TYPES OF FILTER ELEMENTS
Bypass Indicator LRB
HYDRAULIC MODULES AND MANIFOLDS
Relief Valve/Safety Valves
System Pressure Relief Valve
Thermal Relief Valve
Hydraulic Pressure Switch
Used to close the circuit of a warning light that shows low or high pressure in a system.

In a Dual Hyd System a pressure switch is used to affect the circuit’s solenoid valves in aircraft that have dual hydraulic boost control systems.

EXAMPLE: A pressure switch insures that operating pressure to one boost system cannot shut off unless the other system is provided with enough pressure to fly the aircraft.
Pressure Switch
Sequence Valve/Timer Check Valve
Sequence Valve/Timer Check Valve
Control Valves
Rotary Selector Valve (closed centered)
Solenoid Actuated Valve Closed TM 1-1500-204-23-2, p 4-130
Solenoid Actuated Valve Open
Cam Operated Valve
Hydraulic Motor
Actuating Cylinder (Actuators)
Single Action Actuating Cylinder/Single Rod

Hydraulic Servo Pg. 8-25
Flight Cylinder and Selector Valve
Hydraulic Servo and Sloppy Link
Irreversible Valve
Pressure Reducing Valve
ACCUMULATORS
Composed of two chambers.
Stores hydraulic fluid under pressure.
Supplements power pump at peak loads.
Dampens pressure surges.
Absorbs thermal expansion.
Emergency fluid for selected components.
Accumulator/Piston
Accumulator/Spherical
Piston Damper
Hydraulic Damper
Piston Damper M/R Damper
`Vane Damper
Shock Strut
Shock Strut Simple
Servicing Shock Strut
Air Valve
Aircraft Brake System
Parking Brake Valve
Maintenance of Brake System
Shuttle Valve
Pressure-Actuated Shuttle Valve
Hydraulic Fuse
ANY QUESTIONS?