hydraulics finals

Utilizes a 37-degree flare on the tube end.

Flared Fittings

Designed for high pressure systems where thick-walled tubing is difficult to flare. It uses a three-piece setup: a body, a sleeve (ferrule), and a nut. Tightening the nut forces the sleeve to cut/bite into the outer wall of a tube (a process called presetting).

Flareless Fittings (MS)

Joined mechanically using special hydraulic tooling to permanently crimp or deform the fitting onto the tube, eliminating threaded joints to save weight & reduce leak paths.

Swaged/Permanent Fittings

Some aircraft manufacturers have equipped their aircraft with a high-pressure pneumatic system (3,000 psi) in the past. The last aircraft to utilize this type of system was the ______.

Fokker F27

Air is usually stored in metal bottles at pressures ranging from _____–____psi, depending on the particular system.

1000
3000

have been added to recharge air bottles whenever pressure is needed for operating.

Air Compressor

are used in pneumatic systems to prevent damage. They act at pressure limiting valves and operate at certain pressures from bursting tank and blowing out seals.

Relief Valves

are also a necessary part of a typical pneumatic system. consists of a three-port housing, two poppet valves, and a control lever with two lobes. A spring holds the left poppet closed so that compressed air entering the pressure port can't flow to the brakes.

control valve

are used in both hydraulic & pneumatic systems. Air enters the left port, compresses a light spring, forcing it to open and allowing air to flow out the right port.

Check Valves

are a type of control valve used in pneumatic systems. The small outlet port reduces the rate of airflow and the speed of operating gear.

Restrictors

another type of speed-regulating unit. It contains an adjustable needle valve which has a thread around the top and a point on the lower end.

Variable Restrictor

Pneumatic systems are protected against dirt by means of various types of ____.

Filters

consists of a housing with two ports, a replaceable cartridge, and a relief valve.

micronic filter

is similar to the micron filter but contains a permanent wire screen instead of a replaceable cartridge.

screen-type filter

is always located downstream of the compressor. Its purpose is to remove any moisture caused by the compressor.

Desiccant/Moisture Separator

are incorporated at various locations in a pneumatic system. Their purpose is to absorb any moisture that may collect in the lines and other parts of the system.

Chemical Drier

many aircraft use a high-pressure pneumatic backup source of power to extend the landing gear or actuate the brakes, if the main hydraulic braking system fails.

Emergency Backup System

Usually does not include an air bottle. Instead, it generally draws air from the compressor section of a turbine engine. This process is often called bleed air and is used to provide pneumatic power for engine starts, engine deicing, wing deicing, and in some cases, it provides hydraulic power to the aircraft system.

Medium-Pressure Systems (50–150 psi)

Many aircraft equipped with reciprocating engines obtain a supply of low-pressure air from vane-type pumps.

Low-Pressure Systems (1–10 psi)

Used in stationary installations and where long, relatively straight runs are possible.

Rigid Fluid Lines

Used where lines must connect stationary parts to moving components, or in areas subject to high operational vibration.

Flexible Fluid Lines

TYPES OF FLUID LINES (2):

1. rigid fluid lines

2. flexible fluid lines

For low pressure/instruments, for medium-pressure fuel, oil, and hydraulic lines up to 1,500 psi.

Aluminum Alloys

Used in high-pressure systems (3,000 psi or more) like landing gear, brakes, and fire zones due to high tensile strength and abrasion resistance.

Corrosion-Resistant Steel

Used in high-performance transport aircraft for high pressure, oxygen systems. Safety note: must never be used in oxygen systems due to spontaneous combustion risks.

Titanium

Historically used, but obsolete because vibration makes it brittle and prone to cracking.

Copper

rigid fluid lines materials (4):

1. aluminum alloys

2. corrosion resistant steel

3. titanium

4. copper

Metal tubing is sized by _______, which is measured fractionally in ______ of an inch.

outside diameter
sixteenths

Before making repairs to any aircraft tubing, it is important to make accurate ______ of tubing materials.

identification

Printed code markings show a _____ , not more than 4’’ in width, painted at the two ends and approximately midway between the ends of some tubing.

color code

It is important to produce a _____ end, free of ____.

square
burrs

A new piece of tubing should be cut approximately _____ percent longer than the tube to be replaced to provide for minor variations in bending

10

If tube cutter is not available, or if tubing of hard material is to be cut, use a fine-tooth hacksaw, preferably one having ____ teeth per inch.

32

To obtain a smooth bend without flattening the tube, it is usually done with either a ______ bender or a _____ bender.

hand tube
mechanically operated

Consists of a handle, a radius block, a clip, and a slide bar used as levers to provide mechanical advantage necessary to bend the tubing.

Hand Tube Bender

Considered the most practical and most accurate method of bending copper tube.

MECHANICAL TUBE BENDERS

Bends may be made up to 180* without buckling or kinking the tubing.

mechanical tube benders

2 kinds of flares

1. single flare

2. double flare

are frequently subjected to extremely high pressures

flares

is the result of tubing not being cut squarely

crooked flare

types of beading (3):

1. hand beading tool

2. machine beading rolls

3. grip dies

2 Basic Types of Hose (Military Aircraft & Related Equipment)

1. Synthetic rubber

2. Polytetrafluoroethylene

Rubber Hose consists of a minimum of ____ layers

3

designed to withstand the attack of the fluid that passes through it.

inner tube

Hoses are provided in three pressure ranges:

1. low

2. medium

3. high

Flexible hose must not be _____ during installation

twisted

A flexible hose must never be ______ tightly between two fittings.
About ___ to ____percent of the total length must be allowed as slack to provide freedom of movement under pressure.

stretched

5
8

are considered the "invisible muscle of flight"

Hydraulic systems

is based off the Greek word for water, Originally meant the study of the physical behavior of water at rest and in motion.

Hydraulics

Pressure applied to a confined fluid is transmitted undiminished in all directions throughout the fluid.

Pascal's Law

As the speed of a moving fluid increases, the internal pressure within that fluid decreases.

Bernoulli’s Principle

The pressure and volume of a confined gas are inversely proportional when the temperature and amount of gas remain constant.

Boyle's Law

An object at rest stays at rest unless acted upon by an external force.

Newton's First Law (Law of Inertia)

For every action there is an equal and opposite reaction.

Newton's Third Law (Action and Reaction)

Basic Aircraft Hydraulic System Components (6):

1. hydraulic pump

2. hydraulic fluid

3. hydraulic valves

4. hydraulic reservoirs

5. accumulator

6. filters

is a mechanical source of power that converts mechanical power into hydraulic energy.

Hydraulic Pump

Types of Hydraulic Pumps (6):

1. external gear pump

2. internal gear pump

3. rotary vane pump

4. swash plate piston pump

5. radial pump

6. hand pump

is the medium through which power is transferred in hydraulic machinery.

Hydraulic Fluid

Types of Hydraulic Fluids (3)

1. mineral

2. synthetic carbon (poly-alpha-olefin)

3. phosphate ester

mineral hydraulic fluids (2):

1. MIL-H-5606

2. MIL-H-6083

synthetic hydrocarbon fluids (2)

1. MIL-H- 83282

2. MIL-H- 46170

Phosphate Ester-Based

1. Skydrol (Types IV & V)

2. Hyjet

most used fluids in airlines

1. Skydrol (Types IV & V)

2. Hyjet

internal resistance to flow

Viscosity

A liquids ability to resist oxidation for long periods.

Chemical Stability

The temperature at which a liquid gives off vapor in sufficient quantity to ignite momentarily or flash when a flame is applied.

Flash Point

The temperature at which a substance gives off enough vapor to continue burning after ignition.

Fire Point

Hydraulic Fluid Properties (4):

1. viscosity

2. chemical stability

3. flash point

4. fire point

Properly directs the flow of a liquid medium, usually oil, through your hydraulic system.

Hydraulic Valve

Types of Hydraulic Valve (3):

1. Hydraulic Flow Control Valve

2. Hydraulic Pressure Control Valve

3. Hydraulic Directional Control Valve

Used to regulate the flow of volume of passing liquid in the hydraulic system ex. ball, butterfly, diaphragm, needle, plug.

Hydraulic Flow Control Valve

Regulates the fluid pressure passing through hydraulic arrangements to keep the pressure at a desired amount as restricted by the operator.

Hydraulic Pressure Control Valves

Used to track fluid in a system to several devices as demanded.

Hydraulic Directional Control Valves

Store the fluid necessary for the operation of hydraulic systems. It acts as the lungs and kidneys of the hydraulic system.

Hydraulic Reservoirs

Used on aircraft operating at lower altitudes

Non-pressurized (Vented) Reservoirs

Pressurized using regulated engine bleed air or nitrogen gas bottles.

Air Pressurized Reservoirs

Uses high pressure fluid from the system supply line

Fluid Pressurized (Bootstrap) Reservoirs

Relies on an internal mechanical compression spring.

Spring-Loaded Reservoir

Types of Aircraft Hydraulic Reservoir (4)

1. Non-pressurized (Vented) Reservoirs

2. Air Pressurized Reservoirs

3. Fluid Pressurized (Bootstrap) Reservoirs

4. Spring-Loaded Reservoir

Is a steel sphere or cylinder divided into 2 chambers. Dampen pressure surges in the hydraulic systems caused by the actuation of a unit and the effort of the pump to maintain pressure at a preset level.

Accumulator

Is constructed into two halves that are fastened and threaded, or welded together. The top part accept fittings.

Spherical

Consist of a cylinder and piston assembly.

Cylindrical

Types of Accumulator (2)

1. Spherical

2. Cylindrical

Transforms energy in the form of fluid pressure into mechanical force, or action, to perform work. Used to impart powered linear motion to some movable object.

Actuator

Types of Actuator (2)

1. Linear Actuator

2. Rotary Actuators

Types of Linear Actuator (2):

1. Single Action

2. Double Action

Is a component designed to remove contaminants from hydraulic fluid.

Filters / Hydraulic Filters

Inside or just outside the reservoir before the pump.

Suction Filter / Strainer

Down stream of the pump before sensitive control valves.

Pressure Filter

on the fluid return line

Return line Filter

Separate Independent Circuit.

Offline Filter

Types of Hydraulic Filters (4):

1. Suction Filter / Strainer

2. Pressure Filter

3. Return line Filter

4. Offline Filter