Basic Hydraulic Systems Theory and Components
What is a return line?
A connection from the selector valves to the reservoir.
Name the two types of accumulators.
Cylindrical/piston and spherical/diaphragm.
What are the seven additional components of a hydraulic system?
Filters, accumulators, check valves, relief valves, pressure gage, restrictors, and pressure reducing valves.
What is the formula for finding pressure?
P=F/A
Where are the two check valves of a hydraulic jack located?
The supply and pressure lines.
What is the purpose of an actuating cylinder?
To convert hydraulic pressure into linear mechanical motion.
What is the purpose of an actuating unit?
To convert hydraulic pressure into mechanical motion.
What is the purpose of a hydraulic motor?
To convert hydraulic pressure into rotary mechanical motion.
What is the purpose of a pump?
To create a flow of fluid.
What is the purpose of a selector valve?
To direct the fluid to the actuating unit.
What is the purpose of a reservoir?
To hold the supply of fluid for the system.
What is the transmission of force?
When the end of a solid bar is struck, the main force of the blow is carried straight through the bar to the other end.
What is a working line?
A connection from selector valves to the actuating cylinder.
What is a pressure line?
A connection from the pump to selector valves.
What is a supply line?
A connection from the reservoir to the pump.
What is the formula for finding area?
A=F/P
Name the two types of check valves.
Automatic and manual.
Name the four characteristics of hydraulics.
Efficiency, weight, uniform action, simple maintenance.
What safety precaution should be practiced prior to working on a hydraulic system?
Ensure all pressure has been relieved.
What is the formula for finding force?
F=AxP
In what direction is contained fluid under pressure forced?
In all directions.
Where is the location of an automatic check valve?
It is placed in any hydraulic line.
Name two functions of a reservoir.
It provides space for thermal expansion and helps bleed air from the system.
Name six units operated by hydraulics.
Landing gears, wing flaps, control surfaces, wing-folding mechanisms, bomb-bay doors, and brakes.
Name two disadvantages of hydraulics.
Leakage and contamination.
Name the five components of a hydraulic jack.
Manual bypass valve, actuating cylinder, reservoir, check valves, and hand pump.
What is Pascal's Law?
Pressure exerted on an enclosed liquid is transmitted equally and undiminished in all directions and acts with equal force on equal areas.
Name the five components that make up a hydraulic system.
Selector valve, hydraulic lines, actuating units, reservoir, and pump.
Define pressure.
The amount of force on a unit of area acted upon expressed in psi.
Where are manual check valves installed?
The hand pump accumulator line.
What is mechanical advantage?
The output force is greater than the input force.
What is the primary source of hydraulic power?
The pump.
Define force.
The push, pull, or total weight exerted against the total area of a particular surface expressed in pounds.
What is output force?
The total amount of upward force produced by pressure against the working area of the actuating cylinder piston.
Define working area.
The total square inches of the exposed cross-sectional area that the force of pressure is applied to.
What is the function of an accumulator?
To absorb surges and thermal expansion.
What is the purpose check valves?
To allow fluid to flow in one direction only.
What is the purpose of a vent line?
To carry excess fluid over board.
What is the purpose of a pressure gage?
To indicate the amount of pressure in the system.
What is the purpose of a two-way restrictor?
To limit or meter the flow of fluid in both directions by delaying buildup.
What is the purpose of a manual check valve?
To permit a free flow of fluid in both directions.
What is the purpose of an automatic check valve?
To permit the flow of fluid in one direction only.
What is the purpose of a snubber?
To protect the internal parts of the pressure gage from damages due to shocks, oscillations, and surges.
What is the purpose of a one-way restrictor?
To provide restricted hydraulic fluid flow in one direction only by limiting the actuating speed.
What is the purpose of pressure-reducing valves?
To reduce main system pressure to a predetermined lower subsystem pressure.
What is the purpose of relief valves?
To relieve excessive hydraulic pressure.
What is the purpose of a filter?
To remove foreign particles from hydraulic fluid.
What is the purpose of an accumulator?
To store a supply of fluid under pressure for normal and emergency operation.
What is the purpose of fluid in a hydraulic system?
To transmit force.
What is the primary concern in aircraft and hydraulics?
Weight.
What is thermal expansion?
When heat causes a liquid to expand which results in an exertion of pressure against the walls of the container.
