To protect rings or seals from damage when it is necessary to install them over or inside threaded sections, the.
Threaded section should be covered with a suitable sleeve.
Threaded section should be coated with a heavy grease.
to prevent external and internal leakage in aircraft hydraulic units, the most commonly used type of seal is the.
o ring seal gasket seal chevron seal.
which allows free fluid flow in one direction and no fluid flow in the other direction. check valve metering piston shutoff valve.
select the valve used in a hydraulic system that directs pressurized fluid to one end of an actuating cylinder and simultaneously directs return fluid to the reservoir from the other end . selector sequence.
one of the distinguishing characteristics of and open center selector valves used in a hydraulic system is that.
fluid flows through the valve in the OFF position. fluid flows in three directions in the on position.
what type of packings should be used in hydraulic components to be installed in a system containing skydrol.
Packings made of natural rubber. AN packings made of neoprene packing materials made for ester base fluids.
7.the removal of aior from an aircraft hydraulic system is generally accomplished.
by operating the various hydraulic components through. by allowing the system remain inoperative for several hours.
8.what is the purpose of using backup rings with o rings in hydraulic systems above 1.500 psi. Prevent high pressure from extruding the seal between the moving and stationary part provide a seal between two parts of a unitwich move in relation to each other.
9.the purpose of the pressure regulator in a hydraulic system is to
maintain system operating pressure within a predetermined range and to unload the pump prevent failure of components or rupture of hydraulic lines under excesive pressure.
10. a flexible sealing element subject to motion is a packing compound gasket.
11 if a rigid tube is too short for the flare to reach its seat before tightening pulling it into place by tightening
may distort the flare is aceptable mat distort the cone.
12 what is one advantage of pistontype hydraulic motors over electric motors
there is no fire Hazard if the motor is stalled they are considerably quieter in operation.
generally the first step in removing an accumulator from an aircraft is to relieve system pressure drain the reservoir discharge the preload.
.Refer to figure 11 which fitting is an AN flared tube fitting
1 2 3.
If a hydraulic brake system uses neoprene rubber packing materials the correct hydraulic fluid to service the system is
Mineral base oil
synthetic base oil phosphate ester base oil.
The internal resistance of a fluid which tends to prevent it from flowing is called
Viscosity volatility acidity.
What is the viscosity of hydraulic fluid ?
The internal resistance of a fluid which tends to prevent it from flowing the increase in volume of a fluid due to temperature change.
Which is a characteristic of petroleum base hydraulic fluid
Flammable under normal conditions nonflamable under all conditions.
1 when servicing aircraft hydraulic systems use the type fluid specified in the aircraft manufacturers maintenance manual or on the instruction plate affixed to the reservoir or unit
2 hydraulic fluids for aircraft are dyed a specific color for each type of fluid
Both no 1 and no 2 are true only 1 is true only two is true.
Petroleum base hydraulic fluid is which color
Red blue purple.
which of the following is adversely affected by atmospheric humidity if left unprotected?
1 MIL-H-5606 hydraulic fluid 2 skydrol hydraulic fluid none of the above.
Which is a characteristic of synthetic base hydraulic fluid
High flash point low flash point .
Which statement about fluids is correct
All fluids readily transmit pressure
all fluids are considered to be highly compressible.
Two types of hydraulic fluids currently being used in civil aircraft are
Mineral base and phosphate ester base petroleum base and mixed mineral base.
Which of the following lists only desirable properties of a good hydraulic fluid that has chemical stability
high viscosity low flash point high fire point Low viscosity high flash point high fire point
.
Characteristics of MIL-H-8446 hydaulic fluid are
Light purple color phosphate ester base fire resistant butyl rubber seals light green colorphosphate ester base fire resistant butyl rubber seals.
Where can information be obtained about the compatibility of fire resistant hydraulic fluid with aircraft materials fluid manufacturers technical bulletins aircraft manofacturer´s specifications.
Characteristics of MIL-H-5606 hydraulic fluid are
Red color petroleum base will burn uses synthetic rubber seals blue color, will burn uses natural rubber seals.
Characteristics of MIL-H-7644 hydraulic fluid are
Blue color vegetable base will burn natural rubber seals red color petroleum base will burn syntetic rubber seals.
If an aircraft hydraulic system requires mineral base hydraulic fluid but phosphate ester base hydraulic fluid is used what will be the affect on the system
no effect System will be contaminated fluids will not blend and the seals will fail
.
What is used to flush a system normally serviced with MIL-H-5606 hydraulic fluid
methyl ethyl ketone or kerosene Naphtha or varsol.
Components containing phosphate ester-base hydraulic fluid my be cleaned with
naphtha Stoddard solvent .
How can the proper hydraulic fluid to be used n an airplane be determined
Consult the aircraft manufacturers service manual consult the aircraft type certificate date sheet.
Phosphate ester base hydraulic fluid is very susceptible to contamination from
Water in the atmosphere teflon seal material.
1 materials which are skydrol compatible or resistant include most common aircraft metals and potyurethane and epoxy paints
2 skydrol hydraulic fluid is compatible with nylon and natural fibers
Both no 1 and no 2 are true neither 1 y 2.
The hydraulic component that automatically directs fluid from either the normal source or an emergency source to an actuating cylinder is called a
Shuttle valve bypass valve.
The primary purpose of a hydraulic actuating unit is to transform
Fluid pressure into useful work energy for one form to another.
The primary function of the flap overload valve is to
Prevent the flaps from being lowered at airspeeds which would impose excessive structural loads boost normal system pressure.
A unit which transforms hydraulic pressure into linear motion is called
An actuating cylinder an acummulator a hydraulic pump.
If it is necessary to adjust several pressure regulating valves in a hydraulic system what particular sequence if any should be followed
Units with the highest pressure settings are adjusted first units are independent from each other and therefore no particular secuence is necesary.
If an aircrafts constant pressure hydraulic system cycles more frequently than usual and no fluid leakage can be detected the most probable cause is
Low accumulator air preload
a too high relief valve setting.
Unloading valves are used with many engine driven hydraulic pumps to relieve the pump pressure relieve system pressure.
What safety device is usually located between the driving unit and hydraulic pump drive shaft
Pump drive coupling shear section pump motor safety switch.
Which valve installed in a hydraulic system will have the highest pressure setting
main relief valve Thermal relief valve .
Excluding lines which components are required to make up a simple hydraulic system
Pump reservoir relief valve and shuttle valve Pump reservoir selector valve and actuator.
Most variable displacement aircraft hydraulic pumps in use
Contain a built-in means of system pressure regulation are no practical for use with a close center hydraulic system.
In an gear type hydraulic pump a mechanical safety device incorporated to protect the pump from overload is the
Shear pin
check valve.
Pressure is a term used to indicate the force per unit area pressure is usually expressed in
Pounds per square inch
pounds per inch.
If two actuating cylinders which have the same cross- sectional area but different lengths of stroke are connected to the same source of hydraulic pressure they will exert
Equal amounts of force and will move at the same rate of speed different amound of forcebuy will move at the same rate of speed.
Using a hand pump pressure of 100 psi has been built up in a hydraulic system the hand pump piston is 1 inch in diameter a ½ inch line connects the hand pump to an actuating cylinder 2 inches in diameter what is the pressure in the line between the hand pump and the actuator
100 psi 200PSI.
Heat exchanger cooling units are required in some aircraft hydraulic systems because of
High pressures and high rates of fluid flow
the hight heat generated from braking.
Which is true regarding the ground check of a flap operating mechanism which has just been installed
If the time required to operate the mechanism decreases with successive operations it indicates the air is being worked out of the system
all hydraulic lines and componentsshould be cheked for leaks by appliying soapy water for all connectors.
A hydraulic system operational check during ground runup of an aircraft indicates that the wing flaps cannot be lowered using the main hydraulic system but can be lowered by using the emergency hand pump which is the most likely cause
The fluid level in the reservoir is low the flap selector valve has severalinternal leak.
Many hydraulic reservoirs contain a small quantity of fluid which is not available to the main system pump this fluis is retained to
Supply fluid to the auxiliary pump
prime the main system.
The unit which causes one hydraulic operation to follow another in a definite order is called a
Sequence valve selector valve.
Severe kickback of the emergency hydraulic hand pump handle during the normal intake stroke will indicate which of the following
The hand pump outlet check valve is sticking open
the main system relief valve is set too high.
What type of valve in an aircraft hydraulic system permits fluid to flow freely in one direction but restricts the rate at which fluid is allowed to flow in the other direction
Orifice check valve
orifice restrictor.
The main system pressure relief valve in a simple hydraulic system equipped with a power control valve should be adjusted
With the power control valve held in the closed position while one or more actuating units are in operation.
A hydraulic accumulator is charged with an air preload of 1000psi when a hydraulic system pressure of 3000 psi is developed the pressure on the air side of the accumulator will be
3000 psi 4000 psi.
How is the air in a hydraulic accumulator prevented from entering the fluid system
By physically separating the air chamber from the oil chamber with a flexible or movable separator by including a valve that automaticaly.
After a hydraulic accumulator has been installed and air chamber charged the main system hydraulic pressure gauge will not show a hydraulic pressure reading until
The fluid side of the accumulator has been charged the air pressure has become equal to the fluid pressure.
Which must be done before adjusting the relief valve of a main hydraulic system incorporating a pressure regulator
adjust the other system relief valves which have a lower pressure setting The fluid side of the accumulator has been charged.
Which seals are used with petroleum base hydraulic fluids
Buna-N
butyl rubber polyester.
Some hydraulic systems incorporate a device which is designed to remain open to allow a normal fluid flow in the line but closed if the fluid flow increases above an established rate
Hydraulic fuse flow regulator.
When hydraulic system pressure control and relief units fail to function properly how are most systems protected against overpressure
one or more hydraulic fuses instaled in the pressure and return lines A shear section on the main hydraulic pump drive shaft .
Awhen hydraulic pump shaft seal can normally be detected by
Hydraulic fluid flowing from the pump drain line evidence of hydraulic fluid combined in the engine oil.
If an engine driven hydraulic pump of the correct capacity fails to maintain normal system pressure during the operation of a cowl flap actuating unit the probable cause is
Restriction in the pump outlet a partial restriction in the inport of the selector valve.
Before removing the filler cap of a pressurized hydraulic reservoir in order to service the system you must
Relieve the air pressure
pressurise all hydraulic components in the system.
Hydraulic system accumulators serve which of the following functions
1. dampen pressure surges
2. supplement the system pump when demand is beyond the pumps capacity
3. store power for limited operation of components if the pump is not operating
1,2,3 1,2,3,4,.
chattering of the hydraulic pump during operation is an indication
that air is entering the pump of low accumulator preload.
quick-disconnect couplings in hydraulic systems provide a means of
quickly connecting and disconnecting hydraulic lines without losss of fluid or entrance of air into the system easily replacing hydraulic lines.
which seal material is used with phosphate ester base hydraulic fluids
butyl rubber silicone rubber.
a hydraulic pump is a constant displacement type if it
delivers a uniform rate of fluid flow produces a contonuous positive pressure.
a hydraulic motor converts fluid pressure to
linear motion rotary motion angular motion.
a crossflow valve which is designed to bypass fluid from one side of an actuating cylinder to the other side under certain conditions may be found in some aircraft installed in the
landing gear system engine cowl flap system.
hydraulic fluid filtering elements constructed of porous paper are normally
discarted at regular intervals and replaced with new filtering elements not approved for use in certificate aircraft.
a pilot reports that when the hydraulic pump is running the pressure is normal however when the pump is stopped no hydraulic pressure is available this is an indication of a
leaking accumulator air valve
leaking selector valve.
if fluid is added to a reservoir in a constant pressure hydraulic system while the system is pressurized what will result
the fluid level will increase when system pressure is reduced air will be drawn in to the system when the fillr neck cap is removed.
in a hydraulic system that has a reservoir pressurized with turbine engi ne compressor bleed air which unit reduces the air pressure between then engine and reservoir
air pressure regulator
air bleed relief valve.
what is the main purpose of a pressurized reservoir in a hydraulic system
prevent hydraulic pump cavitation prevent hydraulic fluid from foaming.
one of the main advantages of skydrol is its
wide operating temperature
high ioperating pressure.
hydraulic fluid reservoirs are sometimes designed with a standpipe in one of the outlet ports in order to assure emergency supply of fluid the outlet port with the standpipe in it furnishes fluid to the
normal system power pump emergency pump at any time is required.
an emergency supply of fluid is often retained in the main hydraulic system reservoir by the use of a standpipe the supply line is connected to the
inlet of the main hydraulic system inlet of the emergency pump.
to check the air charge in a hydraulic acumulator
reduce all hydraulic pressure then observe reading on the accumulator air gauge read direcly from the auxuliar accumulator gauge.
how would the air pressure charge in te accumulator be determined if the engine is inoperative but the system still has hydraulic pressure? operate a hydraulic unit slowly and note the pressure at wich a rapid pressure drop begins as it goes toward zero read directly from the main system pressure gauge with all actuators inoperative.
how many of these seals are used with petroleum base hydraulic fluids? neoprene buna-N natural rubber - butyl rubber.
hydraulic system thermal relief valvesare set to open at a higher pressure than the system relief valve lower pressure than the system relief valve.
chatter in hydraulic system is caused by air in the system excesive air pressure.
If hydraulic fluid is released when the air valve core of the accumulator is depressed it is evidence of
A ruptured diaphragm or leaking seals a leaking check valve.
although dents in the heel of a bend are not permissible they are acceptable in the remainder of a hydraulic tube providing they are less tha what percent of the tube diameter
20 10 5.
if the hydraulic system pressure is normal while the engine driven pump is running but there is no pressure after the engine has been shut off it indicated
no air pressure in the accumulator the pressure regulator is set too high.
The purpose of restrictors in hydraulic systems is to
Control the rate of movement of hydraulically operated mechanisms allow the flow of fluid in one direction only.
A common cause of slow actuation of hydraulic components is
Internal leakage in the actuating unit restricted orifices.
A loud hammering noise in a hydraulic system having an accumulator usually indicates
Too low or no preload in the accumulator too much preload in the accumulator.
Teflon hose that has developed a permanent set from being exposed to high pressure or temperature should
Not be straightened or bent further
be inmediately replaced.
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