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Flashcards

Hydraulics Verbal

Amariah Barnes English 40 cards

Hydraulics Verbal

Cards in this deck (40)

  1. 1What is a basic hydraulic system consist of?-Fluid to transmit force
    -A reservoir to hold the fluid
    -A pump to move the fluid
    -An actuator to convert fluid into mechanical work
    -Lines to carry the fluid
    -Valves to control pressure and direction
  2. 2What is an open center systemA system that has fluid flow but no pressure in the system when the actuating mechanisms are not moving. Pump circulates fluid from the reservoir through the selector valves , and back to the reservoir. The selector valves are always connected in series with each unlike a closed center system. The valves are in a neutral position.What is an open center system
  3. 3What is a closed center systemFluid is under pressure when the power pump is operating. The reservoir is closed. Valves are parallel with each other and has
    a regulator/relief valve as a safety device.
    Widely used because pressure is readily available    What is a closed center system
  4. 4How are hydraulic fluids identified?Specification and color.
  5. 5What are the different types of hydraulic fluids?MINERAL BASED: MIL-H-5606 is red. Base composition is petroleum and used in systems especially where the fire hazard is low.
    SYNTHETIC: MIL-H- 8446 is purple. Base composition is ester. This fluid is used in most commercial transport category aircraft and extremely fire resistant. But are not fireproof and burn under certain conditions. Susceptible to contamination from water in the atmosphere.
    VEGETABLE BASE: MIL-H- 7664 is blue. Base composition is alcohol and castor oil.
    MIL-H-83282 is a fire resistant POLYALPHAOLEFIN: hydrogenated polyalphaolefin based fluid made to overcome the flammability characteristics of MIL-H-5606. MIL-H-83282 is more flame resistant than MIL-H-5606. A disadvantage is the high viscosity during low temperatures.
  6. 6List three safety precautions that must be observed when working on the aircraft hydraulics system.Keep the system filled with the proper fluid. Clean and replace filters as scheduled, flush with proper solvent, secure lines and fitting to avoid leaks, and replace gaskets and packings after cross-contamination.
  7. 7What is a power pack and how does it work?WHAT IS IT: A hydraulic power pack is a small unit that consists of an electric pump, filters, reservoir, and valves, and pressure relief valve.
    HOW IT WORKS: The power pack does not need a centralized hydraulic power supply system and long stretches of the hydraulic lines, which reduce weight. They are driven by either an engine gearbox or electric motor. Essential valves, filters, sensors, and transducers reduce the system weight and eliminates external leaks and simplifies troubleshooting.
  8. 8Differentiate between the valves used in a hydraulic system. (part 1)Flow control valves: This valve controls the speed and direction of fluid flow in the hydraulic system.
    Selector valves: Controls the direction of movement of a hydraulic actuating cylinder or similar device. Provides simultaneous flow of hydraulic fluid both into and out of the unit. There are two main types of selector valves: open-center and closed-center. An open center valve allows a continuous flow of system hydraulic fluid through the valve even when the selector is not in a position to actuate a unit. A closed-center selector valve blocks the flow of fluid through the valve when it is in the NEUTRAL or OFF position.
    Check Valve: It allows fluid to flow unimpeded in one direction.
    Orifice type check valve: Allows full fluid flow in one direction and restricted flow in the opposite direction.
    Sequence valves: Controls the sequence of operation between two branches in a circuit; they enable one unit to automatically set another unit into motion.
  9. 9continued... (part 2)Priority valve: This valve gives priority to the critical hydraulic subsystems over non critical systems when system pressure is low.
    Quick disconnect valve: These valves are installed in hydraulic lines to prevent loss of fluid when units are removed.
    Pressure control valves: The safe and efficient operation of fluid power systems, system components, and related equipment requires a means of controlling pressure.
    Relief valve: A pressure relief valve is used to limit the amount of pressure being exerted on a confined liquid. This is necessary to prevent failure of components or rupture of hydraulic lines under excessive pressures.
    Pressure regulators: Manages the output of the pump to maintain system operating pressure within a predetermined range and permit the pump to turn without resistance at times when the pressure in the system is within normal operating range.
  10. 10continued... (part 3?)Pressure reducers: are used where it is necessary to lower the normal system operating pressure by a specified amount. Pressure reducing valves provide a steady pressure into a system that operates at a lower pressure than the supply system.
    Shuttle valves: The main purpose of the shuttle valve is to isolate the normal system from an alternate or emergency system.
    Shutoff valve: Shutoff valves are used to shut off the flow of fluid to a particular system or component and used to create a priority in a hydraulic system and are controlled by pressure switches.
    Flap overload valve: They are installed to prevent the flaps from being lowered at high speed.
    Flow equalizer valve: Used to allow actuation to occur simultaneously.
    Landing gear crossflow valve: allows fluid to flow directly from the up-side of the landing gear actuator to the down side when the heavy gear is released to prevent damage and disturbance. This continues to take place until the system fluid can catch up with the demand of the actuator.
  11. 11What is a reservoir?A tank where an adequate supply of fluid for the system is stored.Fluid flows from the reservoir to the pump, to the system , and back to the reservoir The reservoir also replenishes fluid lost through leakages. The reservoir serves as an overflow basin for excess fluid forced out of the system by thermal expansion (the increase of fluid volume caused by temperature changes), the accumulators, and by piston and rod displacement. Allows for expansion and supplies fluid to system - removes air from system - prevents foaming.
  12. 12Explain the difference between the two types of reservoirNon-pressurized reservoirs are used in aircraft that are not designed for violent maneuvers, do not fly at high altitudes, or in which the reservoir is located in the pressurized area of the aircraft.Non Pressurized reservoirs are slightly pressurized due to thermal expansion of fluid and the return of fluid to the reservoir from the main system. This pressure ensures that there is a positive flow of fluids to the inlet ports of the hydraulic pumps.
    Pressurized Reservoirs on aircraft designed for high-altitude flight are usually pressurized. Pressurizing assures a positive flow of fluid to the pump at high altitudes when low atmospheric pressures are encountered.On some aircraft, the reservoir is pressurized by bleed air taken from the compressor section of the engine. On others, the reservoir may be pressurized by hydraulic system pressure.
  13. 13what is an accumulatorAn accumulator is a steel sphere divided into two chambers by a synthetic rubber diaphragm. The upper chamber has fluid at system pressure and the bottom chamber is charged with nitrogen or air. Used to store hydraulic fluid under pressure to be used in emergency or to supplement the main hydraulic system.
  14. 14Explain the four functions of an accumulator- operation and maintenanceMaintenance consists of inspections, minor repairs, replacement of components parts, and testing. Before disassembling any accumulator, ensure that all preload air (or nitrogen) pressure has been discharged. Before making a check, be certain you know the type of high-pressure air valve used. Be sure to follow the manufacturer's instructions for the specific unit you have.
    THE FUNCTIONS: Dampen pressure surges in the hydraulic system caused by actuation of a unit and the effort of the pump to maintain pressure to a preset level. Aid or supplement the power pump when several units are operating at once by supplying extra power from its accumulated, or stored power. Store power for the limited operation of a hydraulic unit when the pump is not operating. Supply fluid under pressure to compensate for small internal or external leaks that would cause the system to cycle continuously by action of the pressure switched continually kicking in.
  15. 15What are the types of contamination?Abrasives, including such as particles as core sand, weld spatter, machining chips, and rust. Non Abrasives including those resulting from oil oxidation and soft particles worn or shredded from seals and other organic components.
  16. 16Explain the procedures for removing hydraulic system contamination. Check, control, and flush. (part 1)CHECK: A check of the system should be made when it is suspected that a hydraulic system has become contaminated or the system has been operated at temperatures in excess of the specified maximum.To determine which component is defective, liquid samples should be taken from the reservoir and various other locations in the system in accordance with the applicable manufacturer’s instructions for a particular hydraulic system.
    CONTROL: Filters provide adequate control of the contamination problem during all normal hydraulic system operations. Maintain all tools and the work area in a clean, dirt-free condition. All seals and gaskets should be replaced during the reassembly procedure.Use only those seals and gaskets recommended by the manufacturer. A suitable container should always be provided to receive the hydraulic liquid that is spilled during component removal or disassembly procedures. Before assembly of any hydraulic components, wash all parts in an approved dry-cleaning solvent, i.e Stoddard solvent.
  17. 17part 2?CONTROL: Filters provide adequate control of the contamination problem during all normal hydraulic system operations. Maintain all tools and the work area in a clean, dirt-free condition. All seals and gaskets should be replaced during the reassembly procedure.Use only those seals and gaskets recommended by the manufacturer. A suitable container should always be provided to receive the hydraulic liquid that is spilled during component removal or disassembly procedures. Before assembly of any hydraulic components, wash all parts in an approved dry-cleaning solvent, i.e Stoddard solvent.
    FLUSHING- When inspection of hydraulic filters or hydraulic fluid evaluation indicates that the fluid is contaminated, flushing the system may be necessary according to the manufacturer's instructions. It is very important to check if the fluid in the hydraulic test stand, or mule, is clean before the flushing operation starts.
  18. 18Differentiation between a single and dual acting actuator.-An actuating cylinder transforms energy in the form of fluid pressure into mechanical force, or action, to perform work.
    -Single acting actuator has one fluid port that pushes the piston in one direction. A selector valve is used to control flow on one side of the piston. A spring within the actuator returns the piston when the selector valve is placed in the opposite direction.
    -Double acting actuator has two fluid ports that push the piston in either direction. A selector valve is used to control flow on either side of the piston. Fluid that is not working is returned to the reservoir.
  19. 19Differentiate between the two types of hand pumps and four types of power driven pumps. (part 1- Hand pumps)HAND PUMPS: The hydraulic pump is used in some older aircraft for the operation of hydraulic subsystems and in a few newer aircraft systems as a backup unit. They are installed usually for testing purposes, emergencies, and to service reservoirs from a single refilling station reducing fluid contamination.
    1. Single action hand pump draws fluid into the pump draws fluid into the pump on one stroke and pumps that fluid out on the next stroke. It is rarely used in aircraft due to this inefficiency.
    2.Double action hand pump produces fluid flow and pressure on each stroke of the handle. It has a housing with a cylinder bore and two ports, a piston, two spring loaded check valves, and an operating handle. There is an O-ring on the piston seals against leakage between the two chambers of the piston cylinder bore. An O-ring in a groove in the end of the pump housing seals against leakage between the piston rod and housing.
    3. A rotary hand pump produces a continuous output while the handle is in motion.
  20. 20(part 2- power driven pumps??)POWER DRIVEN PUMP: Many of the power driven hydraulic pumps are engine driven, electric motor driven, or air driven (RAT).
    1. A constant-displacement pump, regardless of pump rotations per minute, forces a fixed or unvarying quantity of fluid through the outlet port during each revolution of the pump making the quantity of fluid delivered per minute depend upon pump rotations per minute. A pressure regulator is required because the pressure must be kept at a constant value.
    2. A variable-displacement pump has a fluid output that is varied to meet the pressure demands of the system. The pump output is changed automatically by a pump compensator within the pump. A gear-type power pump is a constant-displacement pump. It consists of two meshed gears that revolve in a housing.The driving gear is driven by the aircraft engine or some other power unit.
  21. 21(part 3 - MORE power driven pumps?)3. The vane-type power pump is also a constant-displacement pump. It consists of a housing containing four vanes (blades), a hollow steel rotor with slots for the vanes, and a coupling to turn the rotor.
    4. Piston pumps can be constant-displacement or variable- displacement pumps. The common features of design and operation that are applicable to all piston-type hydraulic pumps are described in the following paragraphs.
    5. A gerotor-type power pump consists essentially of a housing containing an eccentric-shaped stationary liner, an internal gear rotor having seven wide teeth of short height, a spur driving gear having six narrow teeth, and a pump cover that contains two crescent-shaped openings.
  22. 22what are seals?Seals are used to prevent fluid from passing a certain point and to keep air and dirt oiut of the system in which they are used. The reasons for different types of seals are the pressure at which the system oprates, the type of fluid used in the system, the metal finish and clearance between adjacent parts, and the type of motion for example rotary or reciprocating.Seals are divided into three main classes: packings, gaskets, and wipers.
  23. 23Explain the construction, installation, code and maintenance of the following seals and packings: V, O, U, backup, gaskets, and wipers. (multiple parts again ?)-V-ring Packings: The code for V-ring packings, AN6225 are one way seals and are always installed with the open end of the V facing the pressure.V-ring packings must have a male and female adapter to hold them in the proper position after installation. It is also necessary to torque the seal retainer to the value specified by the manufacturer of the component being serviced, or the seal may not give satisfactory service.
    - U ring: U-ring packings (AN6226) and U-cup packings are used in brake assemblies and brake master cylinders. The U-ring and U-cup seals pressure in only one direction; therefore, the lip of the packings must face toward the pressure. U-ring packings are primarily low-pressure packings to be used with pressures of less than 1,000 psi.
  24. 24(part 2)- O ring- Most packings and gaskets used in aircraft are manufactured in the form of O-rings. An O-ring is circular in shape, and its cross-section is small in relation to its diameter. The O-ring packing seals effectively in both directions. This sealing is done by distortion of its elastic compound. The color coding system does not identify sizes, but only system fluid or vapor compatibility and, in some cases, the manufacturer. When selecting an O-ring for installation, the basic part number on the sealed envelope provides the most reliable compound identification. When removing or installing O-rings, avoid using pointed or sharp-edged tools that might cause scratching or marring of hydraulic component surfaces or cause damage to the O-rings. Special tooling for the installation of O-rings is available.
  25. 25(part 3)-Backup rings (MS28782) made of TeflonTM do not deteriorate with age, are unaffected by any system fluid or vapor, and can tolerate temperature extremes in excess of those encountered in high pressure hydraulic systems. Their dash numbers indicate not only their size but also relate directly to the dash number of the O-ring for which they are dimensionally suited. Backup rings are not color coded or otherwise marked and must be identified from package labels. The inspection of backup rings should include a check to ensure that surfaces are free from irregularities, that the edges are clean cut and sharp, and that scarf cuts are parallel.
  26. 26(part 4- almost there?)Gaskets are used as static (stationary) seals between two flat surfaces. Some of the more common gasket materials are asbestos, copper, cork, and rubber. Asbestos sheeting is used wherever a heat resistant gasket is needed. It is used extensively for exhaust system gaskets. A solid copper washer is used for spark plug gaskets where it is essential to have a noncompressible, yet semi soft gasket. Cork gaskets can be used as an oil seal between the engine crankcase and accessories, and where a gasket is required that is capable of occupying an uneven or varying space caused by a rough surface or expansion and contraction. Rubber sheeting can be used where there is a need for a compressible gasket. It should not be used in any place where it may come in contact with gasoline or oil because the rubber deteriorates very rapidly when exposed to these substances. Gaskets are used in fluid systems around the end caps of actuating cylinders, valves, and other units. The gasket generally used for this purpose is in the shape of an O-ring, similar to O-ring packings.
  27. 27(part 5- LAST PART ?) tbh just simplify the answersWipers are used to clean and lubricate the exposed portions of piston shafts. They prevent dirt from entering the system and help protect the piston shaft against scoring. Wipers may be either metallic or felt. They are sometimes used together, a felt wiper installed behind a metallic wiper.
  28. 28Explain the components and operation of large aircraft hydraulic systems.COMPONENTS:
    Has a reservoir, pumps, filters,
    Power Transfer Unit ( PTU)- Supply additional volume of hydraulic fluid needed to operate the auto slats and leading edge flaps and slats at a normal rate when the B EDP malfunctions. Only transfers powers and not fluid.
    OPERATION: Hydraulic Systems are used to power the flight controls, leading edge flaps and slats, trailing edge flaps, landing gear, wheel brakes. Nose wheel steering, and thrust reverser, as well as autopilot
    Large A/C’s have three hydraulic systems, system A and system B, as well as standby — the standby is used when either of the two systems loses pressure
    Large A/C’s also have three reservoirs, A, B and standby which is pressurized by the bleed air.
  29. 29Explain the components and operation of the three types of aircraft pneumatic systems. ( part 1- the systems)The three types of aircraft pneumatic systems are high pressure systems, medium pressure systems, and low pressure systems.
    High pressure systems- air is usually stored in metal bottles at pressures 1,000 to 3,000 PSI to lower the gears and provides for braking when the normal hydraulic systems.
    Medium pressure- A medium-pressure pneumatic system (50–150 psi) usually does not include an air bottle. Instead, it generally draws air from the compressor section of a turbine engine. This process is often called bleed air and is used to provide pneumatic power for engine starts, engine deicing, wing deicing, and in some cases, it provides hydraulic power to the aircraft systems (if the hydraulic system is equipped with an air-driven hydraulic pump). ]
    Low pressure systems- Many aircraft equipped with reciprocating engines obtain a supply of low-pressure air from vane-type pumps.These pumps are driven by electric motors or by the aircraft engine.
  30. 30part 2 - the componentsRelief valve- These prevent damage and act as pressure limiting units. They prevent excessive pressures from bursting lines and blowing out seals.
    Control valves- Controls emergency air brakes.The control valve consists of a three-port housing, two poppet valves, and a control lever with two lobes. To release brakes the control valve is turned off.
    Check valves- Used in both hydraulic and pneumatic systems. It allows air in one direction.
    Restrictors- A type of control valve used in pneumatic systems. The small outlet port reduces the rate of airflow and speed of operation of an actuating unit.
    Variable Restrictor- Speed regulating unit that has an adjustable needle valve. Depending on the direction turned, the needle valve moves the sharp point either into or out of a small
    Filters- Protect the system from dirt a micronic filter consists of a housing with two ports, a replaceable cartridge, and a relief valve.A screen-type filter is similar to the micron filter but contains a permanent wire screen instead of a replaceable cartridge.
  31. 31part 3- more components.Desiccant/ moisture separator- The moisture separator in a pneumatic system is always located downstream of the compressor. Its purpose is to remove any moisture caused by the compressor.
    Chemical Drier- Their purpose is to absorb any moisture that may collect in the lines and other parts of the system. Each drier contains a cartridge that should be blue in color. If otherwise noted, the cartridge is to be considered contaminated with moisture and should be replaced.
  32. 32The next few flashcards are extra things you should need to know ??LETS GOOOO
  33. 33Pascals LawPressure in an enclosed container is transmitted equally and undiminished to all parts of the container
  34. 34What are hydraulic fuses?A safety device used to detect a sudden increase in flow automatically closing the line, preventing fluid from leaking
  35. 35Why is it important that wing flaps are not lowered during high speed?It can cause structural damage and unwanted pitching forces.
  36. 36On the airspeed indicator how do you know that your flaps are extended?The top of the white arc indicates the highest speed at which flaps can be extended. The green arc shows the normal operating range of the airplane.
  37. 37What are the types of filters?Micronic filters are made from specifically treated paper and discarded after use.
    Magnetic filters are made out of magnets. Picks up ferrous contaminants and can be cleaned.
    Mesh filters are for larger contaminants
    and can be cleaned. Made from woven wire.
  38. 38Ways to determine contamination?-Test patch
    Test kit that analyzes whether the fluid is contaminated (from the manufacturer)
    Suspect for contamination
    -Fluid Sampling
    Routine
    Unscheduled non-routine
    Suspicion of contamination
    -Filter Differential Pressure Indicator (DPI) - tells us if there is a difference in pressure - or drop in pressure
    Clogged = Abrasive
  39. 39How to control contamination?Use of filters
    Use of the same fluid causes deterioration
  40. 40What is a servo?Electro Hydraulic actuator designed to aid the pilot in moving the flight controls. ( a motor)

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Flashcards on Hydraulics Verbal, created by Amariah Barnes on 01/08/2022.
Created by
Amariah Barnes · Aug 2022
Updated
Aug 1, 2022
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