Jeppesen Oral- Chapter 8 (Hydraulic, Pneumatic Power Systems) Flashcards
What materials form the bases of the three types of hydraulic fluids?”
Vegetable, mineral, phosphate esters
What colors denote mineral based and phosphate ester based hydraulic fluids?
Mineral based are red, phosphate esters are purple
What are the results of exposing lacquers, oil-based paint, plastic resins, and vinyl compounds to phosphate ester based hydraulic fluid?
Materials will be damaged and softened and the paint will peel
Name several sources used to develop hydraulic pressure?
Hand pumps, engine driven pumps, and electrically driven pumps
What would cause the bypass valve in a hydraulic filter to open and allow unfiltered fluid to circulate in the system?
A clogged filter element
Describe several methods of pressurizing a hydraulic reservoir?
Engine bleed air, variable displacement hydraulic pumps
What feature prevents engine damage if an engine driven hydraulic pump seizes or is overloaded?
A shear section in the pump driveshaft will break
Describe the purpose of a pressure relief valve
Limits maximum pressure produced by the pump
Engine driven pumps deliver the output fluid flow in what two forms?
As a constant volume or a variable volume
Describe the operation of a gear pump
Two meshed gears , rotate in a housing. Inlet fluid carried around the outside of the gears and delivered to the outlet side
Describe the purpose of a pressure regulator.
Manage output of the pump to maintain system pressure. They allow the pump to be unloaded so it turns without significant resistance
What is the device that is used in some systems, to supplement the pump output during periods of high demand?
An accumulator
What are the three different types of accumulators?
Piston, diaphragm, and bladder
What safety precautions must be taken prior to disassembling an accumulator?
Release all the air pr preload
When a hydraulic unit is replaced, what precautions should be taken to avoid contamination of the system?
All lines should be capped after they are disconnected
What types of components or systems are pneumatically operated in some aircraft?
Landing gear, brakes, flaps
Name several sources of pneumatic power
Storage bottles, engine bleed air, engine driven compressors or vane type pumps
What happens to excessive pressure in a pneumatic system?
A relief valve vents it overboard
What is the function of a restrictor in a pneumatic system?
To control the rate of flow of the JSAT
What are the reasons for periodically purging a pneumatic system?
To remove moisture and contaminants
What kind of filter is a micronic filter?
A filter with a special paper element
Does the main hydraulic pump take its fluid from the bottom of the reservoir or from the standpipe?
The main pump normally takes its fluid from the standpipe, while the emergency pump takes its fluid from the bottom of the reservoir. If a break in the system should allow the main mump to pump all its fluid overboard, there will still be enough fluid in the reservoir to allow the emergency system to extend the landing gear and actuate the brakes
Why are some hydraulic reservoirs pressurized?
Pressurization assures that fluid will be supplied to the inlet of the pumps at high altitude when there is not enough atmospheric pressure to do this.
What is a double-action pump?
A pump that delivers fluid with the movement of the pump handle in both directions.
What does an unloading valve do in a hydraulic system?
The unloading valve, or pressure regulator, controls system pressure by shifting the pump outlet fluid from the pressurized system back into the reservoir when the system pressure is high enough. The fluid circulates with very little load on the pump until the system pressure drops to the regulator kick-in value. The pump then forces fluid into the system until the pressure builds back up to the regulator kick-out value
What kind of device is used to control the speed of movement of the piston in a pneumatic actuator?
variable orifice
Why do most high-pressure pneumatic systems include a moisture separator?
When the pressure of the stored air is reduced to the value that is needed in the system, the temperature drops enough to freeze any water that is in the air. The moisture separators remove this water before it can freeze and block the system.
What is used to flush a hydraulic system that uses Skydrol hydraulic fluid?
Trichlorethylene
What is used to flush a hydraulic system that uses mineral base hydraulic fluid?
Naphtha, varsol, or Stoddard solvent
What is used to remove phosphate-ester-base hydraulic fluid from aircraft tires?
Soap and water
Why do some hydraulic pressure gages have a snubber installed between them and they hydraulic pump?
The snubber keeps the gage from fluctuating.
