36 Questions
What is a primary advantage of using hydraulic systems in aircraft?
Precise control of load rate, position and magnitude
Which of the following is NOT a typical user of hydraulic systems in aircraft?
Avionics systems
What is the primary function of valves in a hydraulic system?
To control the direction of pump flow, power level, and fluid supply
What drives the selection of hydraulic system architecture in aircraft design?
Aircraft maximum take-off weight (MTOW)
What is the principle behind Pascal's Law, as applied to hydraulic systems?
Pressure is transmitted equally to all parts of a container
What is the role of the pump in a hydraulic system?
To convert mechanical energy into hydraulic energy
Which of the following is a benefit of hydraulic systems in terms of power transmission?
Smooth, vibration-free power output
What is the primary reason for the extensive use of hydraulic systems in the A380?
To support the high maximum take-off weight (MTOW)
What is the primary function of a diaphragm in an accumulator?
To separate the accumulator into two sections
What is the approximate percentage of air required to initiate the diaphragm movement?
50%
What is the difference between a diaphragm and a bladder in an accumulator?
The diaphragm is one-piece metal sphere, while the bladder is synthetic rubber
What is the purpose of the screw plug in a bladder accumulator?
To retain the bladder and seal the unit
What is the shape of the metal sections that make up the diaphragm?
Hemispherical
What is the similarity between the diaphragm and the bladder in terms of accumulator operation?
Both operate on the same principle
What is the primary function of an accumulator?
To maintain constant pressure in the hydraulic system
What is the main purpose of an accumulator in case of an emergency?
To serve as an emergency power supply
What is the primary advantage of an accumulator in a hydraulic system?
It maintains a constant pressure in the system
What is the function of the piston in a cylinder-type accumulator?
To separate the fluid and air chambers
What is the purpose of an accumulator in case of sudden stops or changes in direction?
To absorb the impact pressure
What is the characteristic of a cylinder-type accumulator?
It has two end caps
What is the primary function of the pump in a hydraulic system?
To supply pressurized hydraulic fluid for the flight control system and utility systems
What is the purpose of the swash plate in the pump?
To change the flow rate of the pump by varying the piston stroke
What type of reservoir is used in aircraft that fly at high altitude?
Pressurized reservoir
What is the purpose of the baffles/fins in the reservoir?
To keep the fluid from random movement such as vortexing or surging
What is the function of the filter in the hydraulic system?
To filter the hydraulic fluid before it leaves the reservoir
What is the primary function of a pressure relief valve in a hydraulic system?
To prevent failure of components or rupture of hydraulic lines under excessive pressure
Where must the vented reservoir be positioned?
At a higher location than the pump
What is the purpose of the heat exchanger in a pressurized reservoir?
To avoid issues related to fluid viscosity
What type of filter element is commonly used in hydraulic systems?
Composed of organic and inorganic fibers
What is the main difference between the engine-driven pump (EDP) and the AC motor-driven pump (ACMP)?
The power source driving the pump
What is the main function of an accumulator in a hydraulic system?
To provide transient flow in a short time
What is the purpose of a bypass valve in a hydraulic filter?
To route the hydraulic fluid from the inlet to outlet port in case of filter blockage
What type of valve is used to control the flow of fluid in one direction?
Check valve
What is the purpose of a check valve in a hydraulic system?
To control the flow of fluid in one direction
What type of element is used to filter out particles from the hydraulic fluid?
All of the above
How are pressure relief valves adjusted in a hydraulic system?
By increasing or decreasing the spring’s tension
Study Notes
Introduction to Hydraulic Systems in Aircraft
- Hydraulic systems are used in aircraft due to their ability to provide efficient power amplification, precise control, and smooth power output
- The largest aircraft, such as the A380, require extensive use of hydraulics, while smaller aircraft, like the Cessna 172, have limited hydraulic applications
Hydraulic Architecture
- Hydraulic systems are effective and efficient due to their ability to:
- Amplify power
- Control load rate, position, and magnitude
- Handle multiple loads simultaneously
- Provide smooth, vibration-free power output
Typical Users of Hydraulic Systems
- Landing gear: extension, retraction, locking, steering, and braking
- Primary flight controls: rudder, elevator, aileron, and active (multi-function) spoiler
- Secondary flight controls: high lift (flap/slat), horizontal stabilizer, spoiler, and thrust reverser
- Utility systems: cargo handling, doors, ramps, and emergency electrical power generation
Concept and Function
- Based on Pascal's Law: pressure exerted on a fluid in an enclosed container is transmitted equally and undiminished to all parts of the container
- Function: to control movable parts by transforming hydraulic energy (pressure and volume) into mechanical energy (force and stroke)
Basic Hydraulic System and Operation
- The pump converts mechanical power from the prime mover (electric or diesel motor) to hydraulic power at the actuator
- Valves control the direction of pump flow, power level, and fluid pressure supplied to the actuator
- Different fluid flow rates are required for different flight profiles
Main Components of Hydraulic Systems
- Pump: supplies pressurized hydraulic fluid for flight control systems and utility systems
- Reservoir: supplies fluid for operating needs, replenishes lost fluid, and serves as an overflow basin for excess fluid
- Filter: filters hydraulic fluid before it leaves the reservoir
- Pressure Relief Valve: limits pressure exerted on a confined liquid to prevent failure of components or rupture of hydraulic lines
- Check Valve: controls fluid flow in one direction
- Accumulator: an energy storage device that provides transient flow, maintains constant pressure, and serves as an emergency power supply
Accumulator Types
- Diaphragm: consists of two hollow, hemispherical metal sections with a synthetic rubber diaphragm dividing the accumulator into two sections
- Bladder: operates on the same principle as a diaphragm but varies in construction
- Cylinder: consists of a cylinder and piston assembly with an internal piston separating the fluid and air/nitrogen chambers
This quiz covers the fundamentals of hydraulic systems in aircraft, including their role in controlling surface size and loading, and their application in different types of aircraft.
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