AFS Topic 1 Module 1 MED
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Questions and Answers

What is the primary function of a relief valve in a hydraulic system?

  • To prevent pressure buildup (correct)
  • To regulate flow rate
  • To increase pressure
  • To filter contaminants

    • What happens when fluid attempts to flow in the opposite direction in a ball check valve?

  • The pressure developed helps to hold the ball on its seat (correct)
  • The ball is lifted off its seat
  • The spring is compressed
  • The valve fails to operate

    • What is the purpose of a thermal relief valve?

  • To relieve excessive pressure due to thermal expansion (correct)
  • To regulate system pressure
  • To filter contaminants
  • To relieve pressure buildup due to pump failure

    • Which type of valve is used to bypass pump delivery pressure to the reservoir?

    <p>Relief valve</p> Signup and view all the answers

    What is the purpose of a system relief valve?

    <p>To prevent pressure buildup</p> Signup and view all the answers

    What happens when the valve poppet is forced off its seat in a thermal relief valve?

    <p>Excessive pressurized fluid flows to the reservoir return line</p> Signup and view all the answers

    What is the main difference between a system relief valve and a thermal relief valve?

    <p>Size</p> Signup and view all the answers

    Why are relief valves commonly used in hydraulic systems?

    <p>To prevent pressure buildup</p> Signup and view all the answers

    What is the purpose of a pressure regulator valve in a closed-centre hydraulic system?

    <p>To maintain the pressure within a specified range</p> Signup and view all the answers

    What is the function of the check valve in the simple regulator system?

    <p>To prevent fluid from flowing back into the pump</p> Signup and view all the answers

    What is special about the MS 28889 valve compared to the AN 6287-1 valve?

    <p>It has no valve core</p> Signup and view all the answers

    What is the purpose of the roll pin on the MS 28889 valve?

    <p>To prevent the housing from being screwed too far into the body</p> Signup and view all the answers

    What happens when the accumulator is full and pressure builds up in the system?

    <p>The piston and ball are in balance</p> Signup and view all the answers

    What is the other name for the MS 28889 valve?

    <p>NATO Valve</p> Signup and view all the answers

    What is one of the functions of the reservoir in a hydraulic system?

    <p>To provide a means of cooling the fluid when the pump is not under demand</p> Signup and view all the answers

    What happens to the fluid in the reservoir when accumulators, actuating cylinders, and other units are not containing their maximum quantities of fluid?

    <p>The fluid is stored in the reservoir</p> Signup and view all the answers

    What is the purpose of standpipes in hydraulic reservoirs?

    <p>To provide a reserve of fluid for emergency operation</p> Signup and view all the answers

    Where is the emergency fluid drawn from when system fluid is lost in hydraulic systems?

    <p>From the bottom of the tank</p> Signup and view all the answers

    What is one of the functions of the reservoir in terms of air in the system?

    <p>To allow a space for trapped air to settle out</p> Signup and view all the answers

    What is the purpose of the power pump in the hydraulic system?

    <p>To force fluid through the system and eventually return to the reservoir</p> Signup and view all the answers

    What is one of the functions of the reservoir in terms of system leakage?

    <p>To provide a reserve of fluid to allow for small leakage</p> Signup and view all the answers

    What is a common feature of sophisticated hydraulic reservoir designs?

    <p>Filters, quantity indicators, and pressure relief systems</p> Signup and view all the answers

    What is a major problem caused by foreign particles in the internal passageways?

    <p>System fluid or gas loss</p> Signup and view all the answers

    What is a major advantage of quick disconnect couplings?

    <p>Ease and speed of connecting and disconnecting plumbing systems</p> Signup and view all the answers

    What is the main feature of screw type fittings?

    <p>A set of teeth protruding from the rim of one half of the coupling</p> Signup and view all the answers

    What is the purpose of the indicating pins on quick threading couplings?

    <p>To indicate when the coupling halves are properly connected</p> Signup and view all the answers

    How do Inst-O-Matic hydraulic couplings operate?

    <p>By utilising a pullback sleeve which releases a set of retaining ball bearings</p> Signup and view all the answers

    What is the function of the self-sealing valve located inside the quick disconnect fitting?

    <p>To eliminate system fluid or gas loss</p> Signup and view all the answers

    How many types of quick disconnect fittings are mentioned in the text?

    <p>Three</p> Signup and view all the answers

    What is the purpose of the indicator pin on an Inst-O-Matic coupling?

    <p>To indicate that the coupling is fully engaged</p> Signup and view all the answers

    Where is the dial indicator mounted to provide reservoir fluid quantity indication?

    <p>On the end of the small diameter chamber</p> Signup and view all the answers

    What is the purpose of the micro switch in the low fluid level detection system?

    <p>To cut pressure supplies to the secondary flight controls and general services</p> Signup and view all the answers

    What type of pump is used in the engine driven pump (EDP)?

    <p>Self-idling swashplate type pump</p> Signup and view all the answers

    What is the purpose of the non-return valve in the engine driven pump (EDP)?

    <p>To route the pressure output from the pump into the system</p> Signup and view all the answers

    What are the three flexible hoses connected to the engine driven pump (EDP) for?

    <p>Suction, pressure, and case drain</p> Signup and view all the answers

    Where is the accumulator located?

    <p>Centre fuselage</p> Signup and view all the answers

    What is the purpose of the accumulator in the hydraulic system?

    <p>To regulate system pressure</p> Signup and view all the answers

    How is the engine driven pump (EDP) secured to the gearbox?

    <p>With a V-band clamp</p> Signup and view all the answers

    What is the main difference between hydraulic and pneumatic systems?

    <p>The type of fluid used</p> Signup and view all the answers

    What is the branch of physics that hydraulic systems belong to?

    <p>Fluid power systems</p> Signup and view all the answers

    What is the earliest known application of fluid power?

    <p>Moving objects using rafts or barges</p> Signup and view all the answers

    What is the purpose of hydraulic systems in aircraft?

    <p>To generate power for landing gear and flight control systems</p> Signup and view all the answers

    What is the principle that hydraulic systems operate on?

    <p>Pascal's Law</p> Signup and view all the answers

    What is the main advantage of hydraulic systems?

    <p>High power-to-weight ratio</p> Signup and view all the answers

    What is the term for the use of pressurised liquid to generate, control and transmit power?

    <p>Hydraulics</p> Signup and view all the answers

    What is one of the ways accumulators act as a cushion or shock absorber in hydraulic systems?

    <p>By absorbing pressure fluctuations in the system</p> Signup and view all the answers

    What is a characteristic of piston type accumulators?

    <p>They are commonly used in aircraft hydraulic systems</p> Signup and view all the answers

    What is a component of a diaphragm accumulator?

    <p>A synthetic rubber diaphragm</p> Signup and view all the answers

    What is a function of accumulators in hydraulic systems?

    <p>To store fluid under pressure for emergency operation</p> Signup and view all the answers

    What are the two main types of accumulators used on aircraft?

    <p>Piston and diaphragm</p> Signup and view all the answers

    What is a component of a piston accumulator?

    <p>A floating piston</p> Signup and view all the answers

    What is a characteristic of diaphragm accumulators?

    <p>They are constructed with a metal sphere</p> Signup and view all the answers

    What do accumulators supplement in hydraulic systems under peak load conditions?

    <p>The hydraulic pump output</p> Signup and view all the answers

    What is the primary characteristic of a fixed delivery pump?

    <p>Delivering a fixed amount of fluid at a given number of revolutions per minute</p> Signup and view all the answers

    What is the function of the universal link in a fixed delivery pump?

    <p>To connect the drive shaft to the cylinder block</p> Signup and view all the answers

    What is the purpose of the slots in the valve plate?

    <p>To provide fluid feed to the pistons on the inlet side</p> Signup and view all the answers

    How do the pistons move in a fixed delivery pump?

    <p>In and out of the cylinders alternately</p> Signup and view all the answers

    What is the angle of rotation between the drive shaft and the cylinder block?

    <p>At an angle</p> Signup and view all the answers

    What is the component that connects the pistons to the drive shaft?

    <p>Ball sockets</p> Signup and view all the answers

    What is the purpose of the cylinder block?

    <p>To house the pistons</p> Signup and view all the answers

    What is the result of the pistons moving outward from the cylinder block?

    <p>The volume of the cylinder spaces increases</p> Signup and view all the answers

    What happens when the axis of the cylinder block is parallel to the axis of the drive shaft in a variable delivery pump?

    <p>No fluid is delivered</p> Signup and view all the answers

    How does the swash plate type variable delivery piston pump operate?

    <p>By altering the piston stroke using a rotating swash plate</p> Signup and view all the answers

    What is the purpose of a variable delivery pump?

    <p>To vary the volume of fluid being delivered at a given number of revolutions per minute</p> Signup and view all the answers

    What is the correct procedure to deflate an accumulator using an AN 6287-1 valve?

    <p>Loosen the swivel nut one turn and depress the valve stem</p> Signup and view all the answers

    What is the effect of changing the alignment of the rotational axis of the cylinder block in a variable delivery pump?

    <p>The piston stroke is altered</p> Signup and view all the answers

    What is the main difference between the AN 6287-1 valve and the MS 28889 valve?

    <p>The MS 28889 valve has no valve core and a larger swivel nut</p> Signup and view all the answers

    What is the purpose of the roll pin on the MS 28889 valve?

    <p>To prevent the housing from being screwed too far into the body</p> Signup and view all the answers

    What is the function of the pistons in a multiple-piston variable delivery pump?

    <p>To draw fluid through the valving surface slot and force it through the outlet slot</p> Signup and view all the answers

    What happens when the accumulator is full and pressure builds up in the system?

    <p>The pressure pushes up on the piston and down on the ball</p> Signup and view all the answers

    What is the difference between a multiple-piston variable delivery pump and a swash plate type variable delivery pump?

    <p>The method of altering the piston stroke</p> Signup and view all the answers

    What is another name for the MS 28889 valve?

    <p>NATO Valve</p> Signup and view all the answers

    What is the result of the pistons moving within their respective cylinders in a variable delivery pump?

    <p>Fluid is delivered through the outlet slot</p> Signup and view all the answers

    What is the purpose of the rotating swash plate in a swash plate type variable delivery pump?

    <p>To alter the piston stroke</p> Signup and view all the answers

    What is the purpose of the pressure regulator valve in a closed-centre hydraulic system?

    <p>To unload the pump when no unit is being actuated</p> Signup and view all the answers

    What is the function of the check valve in the simple regulator system?

    <p>To allow fluid to flow in one direction only</p> Signup and view all the answers

    What is the purpose of tightening the swivel nut on the AN 6287-1 valve?

    <p>To provide a metal-to-metal seal</p> Signup and view all the answers

    Study Notes

    Hydraulic System Components

    • Fluid flows from the reservoir to the power pump, where it is forced through the system and eventually returns to the reservoir.
    • The reservoir ensures a good supply of fluid to the pump, caters for ram displacement, allows for thermal expansion, provides a reserve of fluid for small leakage, and provides a means of filling and checking the system.

    Reservoir Functions

    • Stores unused fluid when accumulators, actuating cylinders, and other units are not containing their maximum quantities of fluid.
    • Provides a reserve of fluid to meet all requirements when the maximum amount of fluid is being used in the system.
    • Equipped with standpipes in systems that require a reserve of fluid for emergency operation of landing gear, flaps, etc.

    Ball Check Valve

    • Installed with a spring to hold the ball or cone on its seat whenever there is no flow.
    • When fluid attempts to flow in the opposite direction, the pressure developed helps to hold the ball or cone on its seat and creates a tighter seal.

    Relief Valves

    • Pressure-operated valves that bypass pump delivery pressure to the reservoir.
    • Used to prevent pressure from building to a point where it might blow seals, burst or damage components within the hydraulic system.
    • Types of relief valves include system relief valves, thermal relief valves, and simple ball type relief valves.

    Pressure Regulator Valves

    • Required in closed-centre hydraulic systems to maintain pressure within a specified range and to keep the pump unloaded when no unit is being actuated.
    • The most simple pressure regulator is the balanced type, which operates by maintaining a balance of forces between the pump pressure and the accumulator pressure.

    Quick Disconnect Couplings

    • Development is directly related to the advent of compact high-performance aircraft and aerospace ground equipment.
    • Advantages include ease and speed of connecting and disconnecting plumbing systems, and elimination of system fluid or gas loss.
    • Types of quick disconnect fittings include screw type, quick threading, and Inst-O-Matic.

    Engine Driven Pump (EDP)

    • Located in the rear fuselage and driven by the No.1 engine gearbox.
    • Connected to the hydraulic system by three flexible hoses fitted with self-sealing quick release couplings.
    • The three hoses are: suction (supply from the reservoir), pressure (to the user services), and return / case drain (to the return line back to the reservoir).

    Accumulator

    • Located in the centre fuselage and consists of a cylinder and a freely floating separator piston.
    • Stores energy and provides a reserve of fluid for the system.

    Hydraulic Systems Introduction

    • Hydraulic systems use pressurized liquid to generate, control, and transmit power.
    • They are used in various applications in aircraft, including landing gear and flight control systems.
    • Hydraulic systems belong to the branch of physics known as fluid power systems, which work by moving fluid.
    • The fluid used in hydraulic systems is incompressible.

    Hydraulic Principles Terminology

    • Pascal's Law: not defined in this text, but it is a fundamental principle in hydraulics.

    Mechanical Advantage

    • Not defined in this text, but it refers to the ability of a system to multiply force or speed.

    Hydraulic System Components

    • Fixed delivery pumps:
      • Deliver a fixed amount of fluid at a given number of revolutions per minute.
      • Consist of a drive shaft, cylinder block, pistons, and a valving surface.
      • Operate by rotating the cylinder block, causing pistons to move in and out of the cylinders.
    • Variable delivery pumps:
      • Designed to vary the volume of fluid being delivered at a given number of revolutions per minute.
      • Can be multiple-piston or swash plate type.
      • Multiple-piston type: alters the stroke of the pistons by changing the angle of the rotational axis of the cylinder block.
      • Swash plate type: alters the stroke of the pistons by using a fixed and rotating swash plate.

    Hydraulic Systems

    • Layout: not described in this text.
    • Operation: hydraulic systems use pressurized fluid to transmit power.
    • Characteristics: not described in this text.
    • Electrical system interface: not described in this text.

    Accumulators

    • Act as a cushion or shock absorber by absorbing pressure fluctuations in the system.
    • Store enough fluid under pressure for emergency operation of certain actuating units.
    • Supplement the hydraulic pump output under peak load conditions.
    • Types: piston and diaphragm.
    • Piston accumulator:
      • Constructed of a metal cylinder, floating piston, air or nitrogen charging valve, and hydraulic fluid port.
      • Requires less space than an equivalent diaphragm accumulator.
    • Diaphragm accumulator:
      • Constructed of a metal sphere, synthetic rubber diaphragm, air or nitrogen charging valve, and hydraulic fluid port.

    Pressure Regulator Valves

    • Required in closed-centre hydraulic systems to maintain pressure within a specified range and keep the pump unloaded when no unit is being actuated.
    • Simple pressure regulator: balanced type, which operates by maintaining a balance of forces between the pressure in the system and the force on the piston.

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    Description

    Learn about the flow of fluid in aviation systems, including reservoirs, power pumps, and filters. Understand how foreign matter is separated from the fluid.

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