Hydraulic and Pneumatic Power Systems FAA questions (A8)
(Refer to figure 11 on page 8-6.) Which fitting is an AN flared tube fitting?
A- 1
Hydraulic system accumulators serve which of the following functions? 1.Dampen pressure surges 2. supplement the system pump when demand is beyond the pump's capacity. 3. Store power for limited operation of components if the pump is not operating. 4. Ensure a continuous supply of fluid to the pump
A- 1, 2, and 3
Which of the following is adversely affected by atmospheric humidity if left unprotected? 1. MIL-H-5606 2. Skydrol Hydraulic fluid 3. Non of the above
A- 2
Which seals are used with petroleum base hydraulic fluids?
A- Buna-N
Which allows free fluid flow in one direction and no fluid flow in the other direction?
A- Check valve.
Where can information be obtained about the compatibility of fire resistant hydraulic fluid with aircraft materials?
A- Fluid manufacturer's technical bulletins.
What condition would most likely cause excessive fluctuation of the pressure gauge when the hydraulic pump is operating?
A- Inadequate supply of fluid
What is used to flush a system normally serviced with MIL-H-5606 hydraulic fluid?
A- Naphtha or varsol
To prevent external and internal leakage in aircraft hydraulic system units, the most commonly used type of seal is the
A- O-ring seal
How would the air pressure charge in the accumulator be determined if the engine is inoperative, but the system still has hydraulic pressure?
A- Operate a hydraulic unit slowly and note the pressure at which a rapid pressure drop begins as it goes towards zero
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?
A- Orifice check valve
What device in a hydraulic system with a constant delivery pump allows circulation of the fluid when no demands are on the system?
A- Pressure regulator
What is the purpose of using backup rings with O-rings in hydraulic systems above 1500 PSI?
A- Prevent high pressure from extruding the seal between the moving and stationary part.
If an aircraft hydraulic system requires mineral base hydraulic fluid, but phosphate ester base hydraulic fluid is used, what will be the effect on the system?
A- System will be contaminated, fluids will not blend, and the seals will fail.
How many of the seals are used with petroleum base hydraulic fluids? 1. Synthetic rubber 2. Natural rubber 3. Neoprene rubber
A- Two
When a hydraulic system pressure control and relief units fail to function properly, how are most systems protected against overpressure?
A- a shear section on the main hydraulic pump drive shaft
Releif valves are used in pneumatic systems
A- as damage prevention units.
Characteristics of MIL-H-7644 hydraulic fluid are
A- blue color, vegetable base, will burn, natural rubber seals
(1) Materials which are Skydrol compatible or resistant include most common aircraft metals and polyurethane and epoxy paints. (2) Skydrol hydraulic fluid is compatible with nylon and natural fibers. Regarding the above statements,
A- both No. 1 and No. 2 are true
How can the proper hydraulic fluid be used in an airplane be determined?
A- consult the aircraft manufacturer's service manual.
Most variable displacement hydraulic pumps of current design
A- contain a built in means of system pressure regulation
Hydraulic fluid is filtering elements constricted of porous paper are normally
A- discarded at regular intervals and replaced with new filtering elements
One of the distinguishing characteristics of an open center selector valve used in a hydraulic system is that
A- fluid flows through the valve in the OFF position
The primary purpose of hydraulic actuating unit it to transform
A- fluid pressure into useful work
After installation of a rebuild hydraulic hand pump, it is found that the handle cannot be moved in the pumping direction (pressure stroke). The most likely cause is an incorrectly installed
A- hand pump outport check valve.
A worn hydraulic pup shaft seal can normally be detected by
A- hydraulic fluid flowing from the pump drain line
Some Hydraulic system incorporate a device which is designed to remain open to allow a normal fluid low in the line, but closed if the fluid flow increases above an established rate. This device is generally referred to as a
A- hydraulic fuse.
If an aircraft's constant pressure hydraulic system cycles more frequently than usual and no fluid leakage can be detected, the most probable cause is
A- low accumulator air preload
if a rigid tube is too short for the flare o reach its seat before tightening, pulling it into place by tightening
A- may distort the flare
Two types of hydraulic fluids currently being used in civil aircraft are
A- mineral base and phosphate ester base
If a hydraulic brake system uses neoprene rubber packing materials, the correct hydraulic fluid to service the system is
A- mineral base oil.
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 indicates
A- no air pressure in the accumulator.
Teflon hose that has developed a permanent set from being exposed to high pressure or temperature should
A- not be straightened or bent further
What is the main purpose of a pressurized reservoir in a hydraulic system?
A- prevent hydraulic pump cavitation
The purpose of an orifice check valve is to
A- resist flow in one direction and allow free flow in the other
If an engine driven pump of the correct capacity fails to maintain normal system pressure during the operation of a cowl flap actuating unit, the probable cause is
A- restriction in the pump outlet.
In most modern hydraulically actuated landing gear system, the order of gear and fairing for operations is controlled by
A- sequence valves
Many hydraulic reservoirs contain a small quantity of fluid which is not available to the main system pump. This fluid is retained to
A- supply fluid to the auxiliary pump.
Chattering of the hydraulic pump during operation is indication
A- that air is entering the pump
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
A- the fluid side of the accumulator has been charged
What is the viscosity of hydraulic fluid?
A- the internal resistance of a fluid which tends to prevent it from flowing
Which valve installed in a hydraulic system will have the highest pressure setting?
A- thermal relief valve
A loud hammering noise in the hydraulic system having an accumulator usually indicates
A- too low or no preload in the accumulator.
One of the main advantages of skydrol is its
A- wide operating tempurate
(Refer to figure 12 on page 8-7.) Which illustration(s) show(s) the correct spiral for Teflon backup rings?
B- 1 and 3
Which characteristics apply to aircraft hydraulic systems? 1. Minimum maintenance requirements 2. lightweight 3. About 80 percent operating efficiency (20 percent loss due to fluid friction) 4. simple to inspect
B- 1, 2 and 4
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 1/2-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?
B- 100 PSI
Although dents in the heel of a bend are not permissible the they are acceptable in the remainder of a hydraulic tube providing they are less than what percent of the tube diameter?
B- 20
A hydraulic accumulator is charged with an air preload of 1,000 PSI. When a hydraulic system pressure of 3,000 PSI is developed, the pressure on the air side of the accumulator will be
B- 3,000 PSI
Which is a characteristic of petroleum base hydraulic fluid?
B- Flammable under normal conditions
Which of the following lists only desirable properties of a good hydraulic fluid?
B- Low viscosity, chemical stability, high flash point, high fire point.
What type of packing should be used in hydraulic components to be installed in a system containing SKydrol?
B- Packing materials made for ester base fluids
Petroleum base hydraulic fluid is which color?
B- Red
What function foes the absolute pressure regulator perform in the pneumatic power system?
B- Regulates the compressor inlet air to provide a stabilized source of air for the compressor
An )-ring intended for use in a hydraulic system using MIL-H-5606 (mineral base) fluid will be marked with
B- a blue stripe or dot
If hydraulic fluid is released when the air valve core of the accumulator is depressed, it is evidence of
B- a ruptured diaphragm or leaking seals.
A fully charged hydraulic accumulator provides
B- a source for additional hydraulic power when heavy demands are placed on the system
Chatter in a hydraulic system is caused by
B- air in the system
A unit which transforms hydraulic pressure into linear motion is called
B- an actuating cylinder
How is the air in a hydraulic accumulator prevented from entering the fluid system?
B- by physically separating the air chamber from the oil chamber with a flexible or movable separator
The purpose of restrictors in hydraulic system is to
B- control the rate of movement of hydraulically operated mechanisms.
The installation f a new metal hydraulic line should be made with
B- enough bends to allow the tube to expand and contract with temperature changes and to absorb vibration
If two actuating cylinders which have the same cross sectional area but different lengths of stoke are connected to the same source of hydraulic pressure, they will exert
B- equal amounts of force and will not move at the same rate of speed
The air that is expended and no longer needed when an actuating unit is operating in pneumatic system is
B- exhausted or dumped, usually overboard.
A hydraulic system referred to as a "power pack" system will
B- have all hydraulic power components located in one unit.
which is true regarding the ground check of a flap operating mechanism which has just been installed?
B- if the time required to operate the mechanism decreases with successive operations, it indicates the air is being worked out of the system.
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
B- inlet of the main system pump.
A common cause of slow actuating of hydraulic components is
B- internal leakage in the actuating unit
A crossflow calve 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
B- landing gear system
Characteristics of MIL-H-8446 (Skydrol 500 A & B) hydraulic fluid are
B- light purple color, phosphate ester base, fire resistant, butyl rubber seals
In a typical high pressure pneumatic system, it the moisture separator does not vent accumulated water when the compressor shuts down, a likely cause is
B- malfunctioning solenoid dump valve.
Pressure is a term used to indicate the force per unit area. Pressure is usually expressed in
B- pounds per square inch
The primary function of the flap overload valve is to
B- prevent the flap from being lowed at airspeeds which would impose excessive structural loads.
to check the air charge in a hydraulic accumulator,
B- reduce all hydraulic pressure, then observe the reading on the accumulator air gauge
Pneumatic systems utilize
B- relief valves
Generally, the first step in removing an accumulator from an aircraft is to
B- relieve system pressure
What is one advantage of piston type hydraulic motors over electric motors?
B- relieve system pressure
Before removing the filler cap of a pressurized hydraulic reservoir,
B- relieve the air pressure
The purpose of a hydraulic pressure regulator is to
B- relieve the pump of its load when no actuating units are being operated.
A hydraulic motor converts fluid pressure to
B- rotary motion
IN a gear type hydraulic pump, a mechanical safety device incorporated to protect the pump from overload is the
B- shear pin.
A hydraulic system operational check during ground run-up of an aircraft indicates that the wing flaps cannot be lowered using the main hydraulic system, but can be lowered using the the emergency hand pump. Which is the most likely cause?
B- the fluid level in the reservoir is low.
If a fluid is added to a reservoir in a constant pressure hydraulic system while the system is pressurized. what will result?
B- the fluid level will increase when system pressure is reduced?
What happens to the output of a constant displacement hydraulic pump when the hydraulic system pressure regulator diverts the fluid from the system to the reservoir?
B- the output pressure reduces, but the volume remains the same
To protect packing rings or seals from damage when it is necessary to install them over or inside threaded sections, the
B- threaded section should be covered with a suitable sleeve.
The internal resistance of a fluid which tends to prevent it from flowing is called
B- viscosity
The main system pressure relief valve in a simple hydraulic system equipped with a power control valve should be adjusted
B- with the power control valve held in the CLOSED position
In a hydraulic system that has a reservoir pressurized with turbine engine compressor bleed air, which unit reduces the air pressure between the engine and reservoir?
C- Air pressure regulator
Which statement about fluids is correct?
C- All fluids readily transmit pressure
(1) When servicing aircraft hydraulic systems, use the type fluid specified in the aircraft manufacturer's maintenance manual or on the instructions plate affixed o the reservoir or unit. (2) Hydraulic fluids for aircraft are dyed a specific color for each type of fluid Regarding the above statements,
C- Both No. 1 and No. 2 are true
(1) Relief valves are used in pneumatic systems as damage preventing units (2) Check valves are used in both hydraulic and pneumatic systems Regarding the above statements
C- Both No.1 and No. 2 are true
Which seal/material is used with phosphate ester base hydraulic fluids?
C- Butyl rubber
Which must be done before adjusting the relief valve of a main hydraulic system incorporating a pressure regulator?
C- Eliminate the action of the unloading valve.
What safety device is usually located between the driving unit and hydraulic pump drive shaft?
C- Pump drive coupling shear section
Excluding lines, which components are required to make up a simple hydraulic system?
C- Pump, reservoir, selector valve, and actuator
Select the valve used in a hydraulic system that directs pressurized fluid to one end of an actuating cylinder and simultaneously directs return fluid tot he reservoir form the other end.
C- Selector
Components containing phosphate ester-base hydraulic fluid may be cleaned with
C- Stoddard solvent
If it is necessary to adjust several pressure regulating valves in a hydraulic system, what is particular sequence, if any, should be followed?
C- Units with the highest pressure setting are adjusted first.
An aircraft pneumatic system, which incorporates an engine driven multistage reciprocating compressor, also required
C- a moisture seperator
Extrusion of an O-ring seal is prevented in a high pressure system by the use of a
C- backup ring on the side of the O-ring away from the pressure
The removal of air from an aircraft hydraulic system is generally accomplished
C- by operating the various components through several cycles
A hydraulic pump is a constant-displacement type if it
C- delivers a uniform rate of fluid flow
Which is a characteristic of synthetic base hydraulic fluid?
C- high flash point
heat exchanger cooling unites are required in some aircraft hydraulic systems because of
C- high pressures and high rates of fluid flow.
Hydraulic system thermal relief valves are set to open at
C- higher pressure than the system relief valve
A hydraulic hose identified as MIL-H-8794 will have a yellow stripe running the length of the hose. This stripe
C- is used to ensure that the hose is installed without excessive twisting
A pilot reports that when the hydraulic pump is running, the pressure is normal. However, when the pump is stopped, no hydraulic pressure available. this is an indication o
C- leaking accumulator airvalve
the purpose of the pressure regulator in a hydraulic system is to
C- maintain system operating pressure within a predetermined range and to unload the pump
A filter incorporating specially treated cellulose paper is identified as a
C- micronic filter
Hydraulic fluid reservoirs are sometimes designed with a standpipe in one of the outlet ports in order o assure emergency supply of fluid. The outlet port with the standpipe in it furnishes fluid to the
C- normal system power pump
A flexible sealing element subject to motion is a
C- packing
Quick disconnect couplings in hydraulic systems provide a means of
C- quickly connecting and disconnecting hydraulic lines without loss of fluid or entrance of air into the system
Characteristics of MIL-H-5606 hydraulic fluid are
C- red color, petroleum base, will burn, uses synthetic rubber seals
Unloading valves are used with many engine driven hydraulic pumps to
C- relieve the pump pressure.
The component in the hydraulic system that is sued to direct the flow of fluid is the
C- selector valve.
The unit which causes one hydraulic operation to follow another in a definite order is called
C- sequence valve
The hydraulic component that automatically directs fluid from either the normal source or an emergency source to an actuating cylinder is called
C- shuttle valve.
Severe kickback of the emergency hydraulic hand pump handle during the normal intake stroke will indicate which of the following?
C- the hand pump outport check valve sticking open.
Phosphate ester base hydraulic fluid is very susceptible to contamination from
C- water in the atmosphere
