airsys Flashcards
uses a fluid under pressure to drive machinery or move mechanical components.
hydraulic system
what consists of the hydraulic system
hydraulic fluid and three major mechanical components
what are the three major mechanical components
pressure generator or hydraulic pump, hydraulically powered “motor”, system “plumbing”
powers the component concerned
hydraulically powered “motor”
which contains and channels the fluid throughout the aircraft as required
system “plumbing”
Hydraulic systems were utilized for what on early aircraft.
brake systems
Depending upon the aircraft concerned, a single hydraulic system, or two or more hydraulic systems working together, might be used to power any or all of the following components:
- wheel brakes
- nose wheel steering
- landing gear retraction/extension
- flaps and slats
- thrust reversers
- spoilers/speed brakes
- flight control surfaces
- cargo doors/loading ramps
- windshield wipers
- propeller pitch control
what creates the hydraulic power
hydraulic fluid is pumped from the reservoir into the rest of the system. The pressurised fluid then passes through valves and flows to the actuator where hydraulic power is converted to mechanical energy to achieve the desired function.
reservoir holds the fluid, which is usually hydraulic oil. It also protects the fluid from getting contaminated, which is critical to ensure the hydraulic system functions optimally.
reservoir or tank
the hollow structures that carry the hydraulic fluid from one location to another within the system.
piping
force the hydraulic fluid from the reservoir to the rest of the circuit
hydraulic pump
process of hydraulic pump
creates a vacuum at the pump inlet which forces the fluid from the reservoir into the pump. Next, the pump pushes the fluid to the pump outlet and then forces it into the rest of the hydraulic system.
These pumps have an unchangeable flow rate, so every stroke moves the same amount of fluid. They are good for jobs with a single action that are repeated for long periods. Examples include gear gerotor and screw pumps.
fixed displacement pumps
These pumps can change the flow rate of the fluid and outlet pressure. They can power a variety of complex equipment, but they are more expensive and require more attention than fixed displacement pumps. Examples include piston pumps and vane pumps.
variable displacement pumps
These pumps are operated manually by the hand and foot.
hand or manual hydraulic pumps
An electric motor or other power source is required to make the mechanical elements of the pump work.
power source
component which changes the hydraulic power in the fluid into mechanical power to achieve the desired acti
hydraulic actuator
two types of actuator
hydraulic cylinder and hydraulic motor
creates linear movement (movement in a straight line)
hydraulic cylinder
creates torque (a twisting force) and rotation.
Hydraulic motor
control the pressure, flow rate and direction of the fluid moving through the circuit. There are many types of valves with specific functions. We will outline the most common below.
valves
limit the pressure within the system to protect all the components from damage. It is normally closed, but opens when system pressure exceeds a maximum value.
pressure control valves
, flow control valves influence the rate at which the fluid flows throughout the system. This is achieved by decreasing or increasing the diameter of the opening the hydraulic fluid flows through.
flow control valves
it can stop, start and change the direction of the flow of hydraulic fluid. The simplest of these valves is called a check valve and it allows the hydraulic fluid to flow in one direction, while blocking fluid flow in the other direction.
direction control valves
prevent the hydraulic system from being contaminated. This is essential to ensure the system works effectively and safely.
filters
without a filter, what happens?
a hydraulic system’s components may wear down quickly and pipes may get blocked.
stops any contaminants in the reservoir fluid getting into the rest of the hydraulic system. It is located at the input side of the hydraulic pump
suction line filter
is the medium via which a hydraulic system transmits its energy and, theoretically, practically any fluid could be utilized.
fluid
properties of fluid
high flash point, adequate viscosity, lubricant properties, thermal capacity/conductivity
In the event of a hydraulic leak, fluid ignition should not occur at the normal operating temperatures of the surrounding components
high flash point
Aircraft hydraulic systems must work efficiently over a broad temperature spectrum. The fluid used must flow easily at very low temperatures but must also maintain adequate viscosity at high temperatures.
adequate viscosity
The ideal hydraulic fluid
have a very low freezing point and a very high boiling point.
The hydraulic fluid acts as a lubricant for the pumps, actuators and motors within the system. The fluid should have anti-corrosion properties and be thermally stable
lubricant properties
Hydraulic fluid acts as a system coolant. The fluid must be able to readily absorb and release heat.
Thermal Capacity/Conductivity
leading cause of component and system failure
Lack of maintenance of hydraulic systems
key to the success of any maintenance program whether in hydraulics or any equipment which we need reliability.
preventive maintenance
which in many cases can cause additional hydraulic component failure when it is not performed to standard.
corrective maintenance
two areas of concern on proper maintenance on a hydraulic system
preventive maintenance and corrective maintenance
is any system that uses pressurized air to move something
pneumatic system
pneumatic systems are used for
brakes, opening and closing doors, driving hydraulic pumps, alternators, starters, water injection pumps, etc., operating emergency devices
With pneumatics, air is usually pumped into a what and using what
receiver using compressor
pneumatic device that transfers power (from an electric motor, diesel or gasoline engine, etc.) into potential energy stored in compressed air.
air compressor
are used in pneumatic systems to prevent damage. They act as pressure limiting units and prevent excessive pressures from bursting lines and blowing out seals.
valves
also a necessary part of a typical pneumatic system, it controls the release of fluid into the port. The control valve consists of a three-port housing, two poppet valves, and a control lever with two lobes
control valves
are extremely simple devices yet they serve an important purpose in many pneumatic circuits. Generally used in systems where back flow is not permitted, check valves are two-port valves that allow free flow in one direction and block flow in the opposite direction.
chec valves
is an air filtration device that eliminates pollutants from compressed air. Pneumatic systems are protected against dirt by means of various types of filters.
pneumatic filter
consists of a housing with two ports, a replaceable cartridge, and a relief valve.
micronic filter
Its purpose is to remove any moisture caused by the compressor. always located downstream of the compressor.
moisture separator / desiccant
A complete moisture separator consists of
reservoir, a pressure switch, a dump valve, and a check valve. It may also include a regulator and a relief valve.
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 driers
Nitrogen used for emergency landing gear extension is stored in two bottles, one bottle located on each side of the nose wheel well.
nitrogen bottles
released by actuation of an outlet valve.
nitrogen from the bottles
usually does not include an air bottle. Instead, it generally draws air from the compressor section of a turbine engine.
A medium-pressure pneumatic system (50–150 psi)
Many aircraft equipped with reciprocating engines obtain a supply of low- pressure air from vane-type pumps. These pumps are driven by electric motors or by the aircraft engine.
low pressure pneumatic system
Maintenance of the pneumatic power system consists of
servicing, troubleshooting, removal, and installation of components, and operational testing.
