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Virtually all modern airplanes use a simple hydraulic system to operate the _____
Brakes
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A hydaulic system must contain 4 basic types of units.
- Fluid supply
- Pump
- Actuator
- Selector valve
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A single unit containing an electrically driven hydraulic pump, reservoir, control valve and many of the auxiliary valves is known as a hydraulic _______ system.
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The two types of hydraulic reservoirs are:
- Integral (in another component, like a transmission)
- In-line (inside its own housing , connected by hoses)
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Aircraft that operate in the lower altitudes normally use _______ reservoirs
unpressurized
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3 ways to pressurize hydraulic reservoirs:
- aspirator (by jet action draws more air into reservoir)
- bleed air
- hydraulic piston
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One micron is equal to ___ inch.
.000039 inch or 1 millionth of a meter
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Pleated paper micronic filters are usually installed in the hydraulic system pressure or return line?
Return
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Cuno filters can or cannot be used on the pressure side of the system?
Used on pressure side
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Hand pumps are usually single or double acting?
piston rod displacement double acting
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Which type of pump moves a specific volume of fluid each time its shaft turns
Constant displacement
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What type of valve is needed when a constant displacement pump is used?
regulator or relief valve
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A gear type hydraulic pump is a ________ pump.
constant displacement
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A hydraulic system using a variable displacement pump does or does not require an unloading valve.
nope
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A selector valve is one of the most common type of ____ (flow or pressure) control valve.
Flow
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The (open or closed) center valve directs fluid through the center of the valve back to the reservoir when a unit is not being actuated.
open center
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A valve that allows fliud to flow in one direction but no flow in the opposite direction is called ?
Check Valve
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AA valve that allows fliud to flow in one direction but a restricted flow in the other direction is called ?
Orifice check valve
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A valve that required one component to fully actuate before another can actuate is called ?
Sequence valves
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Sequence valves are opened mechanically or hydraulically?
Mechanically
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Priority valves are opened mechanically or hydraulicly?
Hydraulicly
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Similar to a sequence valve but opened by hydraulic pressure instead of mechanical contact?
Priority
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What can be installed to block a line in case of a serious leak?
Hydraulic fuse
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Two principles upon which a hydraulic fuse operates?
- Pressure drop
- Volume limiting
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The simplest type of pressure control valve is ?
Relief valve
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What may be installed when it is necessary to operate some portion of a hydraulic system at a pressure lower that normal system pressure?
Pressure reducer
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What device is used to store hydraulic pressure?
Accumulator
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One compartment of an accumulator is connected to the hydraulic system while the other side is filled with?
Nitrogen or Dry air
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What are the 3 types of accumulators?
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AN812 valve cores are identified by what letter embossed on their stem?
"H"
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Which air valve has these features?
-No core
- Metal to metal seal
-Swivel nut to open and close , same size as valve body
AN812, AN6287-1, or MS28889-1
MS28889-1
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How many different types of air valves are used in aircraft?
3
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Which air valve has these features?
-"H" stamped on stem
-Similar to automotive
-Core is used to seal
AN812, AN6287-1, or MS 28889-1
AN812
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What air valves have these features?
-Metal to metal seal
-opened and closed by swivel nut smaller than body of valve
-Has a core
AN6287-1
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Hydraulic actuators which produce a straight line movement are known as?
Linear actuators
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If a continuous rotational force is needed , a hydraulic ____ is used.
Motor
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A chevron seal is a one or two way seal?
One way
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An o-ring is a one or two way seal?
two way
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An o-ring should have a width approx. 10% ____ than the width of its groove.
Larger
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What is used with an o-ring when the operating pressure exceeds 1500 psi?
Back-up rings
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O-ring back-up rings are made of?
Leather or Teflon
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The ______ date is the date of O-ring manufacture.
cure date
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An o-ring marked with a blue dot is compatible with?
Air or 5606
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When installing or removing o-rings , extreme care must be taken to prevent rings from being _____ by sharp edges.
nick or cut
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O rings with red dots are used for?
Fuel
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O-rings with a green dot are used with?
Skydrol
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O-rings with yellow dots are used with?
synthetic engine oil
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O-rings with a white dot are used with?
petroleum engine oil
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Name 4 one way seals.
- D-ring
- U-ring
- V-ring
- Chevron
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What is used to prevent loss of fluid when hydraulic units are replaced?
Quick disconnect valves
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What is an example of a variable displacement pump?
Piston pump
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What are 2 types of check valves?
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What are the 4 types of linear actuators
- Single acting
- double acting balanced
- double acting unbalanced
- cushioned
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What is meant by a tandem actuator.
2 actuators built into one unit
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Actuators that contain a control valve are generally called.
hydraulic servos
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