PDF | The modeling of aircraft hydraulic system has generated many approaches over the years, ranging in applicability from easy to extremely complicated. The Average modern aircraft utilizes hydraulic systems to operate several systems. The fluid used in aircraft hydraulic systems is one of the system's most . accomplished with hydraulic power systems. Hydraulic system complexity varies from small aircraft that require fluid only for manual operation of the wheel.

Aircraft Hydraulic System Pdf

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Seminar Report on Aircraft Hydraulic System - Download as PDF File .pdf), Text File .txt) or read online. considerations which must be observed in the design of aircraft hydraulic systems Aircraft Hydraulic System, AFWAL-TR, Boeing Military Airplane. Intro Saab Company. • Design Philosophy - Aircraft Hydraulic Supply System. • Monitoring Hydraulic Systems. ‒ Leakage Monitoring. ‒ Pump Monitor for Early.

The motive power for these pumps can be generated by a wide variety of options inclusive of: Manual. In many light aircraft, a manual hydraulic pump provides pressure for wheel brakes or flap extension and retraction.

Engine Driven. Pumps are frequently mounted on the engine accessory gear box. Bleed air powered motors are utilized on some aircraft to drive hydraulic pumps. A Power Transfer Unit PTU allows the hydraulic pressure of one hydraulic system to drive a pump to pressurize a second hydraulic system without any transfer of hydraulic fluid.

Aircraft Hydraulic System

Depending upon the installation, a PTU can be single or bi-directional. Ram Air Turbine. Hydraulic Motors and Cylinders Hydraulic motors and cylinders utilize pressurized fluid to do mechanical work. Hydraulic Motors. A hydraulic motor is a mechanical device that converts hydraulic pressure and flow into torque and angular displacement or rotation.

Various types of hydraulic motors such as gear, vane and radial piston motors are available. On aircraft, hydraulic motors are most often used to drive jackscrews which can in turn be utilized to power flaps, stabilizer trim and some vertically extending landing gear applications such as found on the LOCKHEED AC Spectre Hercules aircraft. Hydraulic Cylinders.

A hydraulic cylinder, sometimes referred to as a linear hydraulic motor or a hydraulic actuator, is a mechanical actuator that is used to provide a reversible force in a single direction.

The hydraulic cylinder consists of a cylinder barrel within which a piston connected to a piston rod ues hydraulic pressure to move back and forth. Aircraft applications include landing gear extension and retraction, cargo door operation and movement of flight control surfaces. System "Plumbing" Components Aviation hydraulic systems, in general, are of the "open loop" variety drawing fluid from a reservoir, pressurizing it and making it available to the various user components before returning the fluid to the reservoir.

The primary components of the "plumbing" portion of the hydraulic system include the following: Reservoir. Hydraulic fluid reservoirs are required by most aircraft systems to provide a ready source of fluid for the hydraulic pump s and to contain a varying volume of fluid.

This variance results from differential actuator volume dependent upon whether the actuator is extended or retracted and for fluid thermal contraction or expansion. The reservoir size is optimized so that only the amount of fluid needed for proper function is carried.

Large Aircraft Hydraulic Systems – Boeing 777 Hydraulic System

In many installations, bleed air is used to pressurize or "bootstrap" the reservoir to help prevent hydraulic pump cavitation.

Hydraulic fluid cleanliness is essential to proper system function. In-line filters are incorporated into the hydraulic system to remove any contaminants from the fluid. Shut Off Valves.

Air Craft Hydraulic System Seminar Report pdf

Hydraulic shut off valves are usually installed at the engine firewall. In the event of an engine fire, the shutoff valve is closed to prevent possible ignition of the hydraulic fluid. Control Valves. Hydraulic motors and actuators have an associated control valve which is positioned in response to a manual or automated system selection such as moving the flap lever. The control valve responds to that selection by positioning to allow pressurised hydraulic fluid to flow into the motor or actuator in the appropriate direction.

Pressure Relief Valve. In some systems, especially those utilising a fixed displacement pump, pressure relief valves are incorporated to ensure that nominal system pressure is not exceeded. If system pressure becomes too high, the relief valve opens and fluid is returned to the reservoir.

Hydraulic Fuses. Hydraulic fuses are in-line safety devices designed to automatically seal off a hydraulic line if pressure becomes too low. A hydraulic accumulator is a pressure storage reservoir in which hydraulic fluid is held under pressure by an external source of energy.

The external source can be a spring or a compressed gas. An accumulator enables a hydraulic system to cope with extremes of demand using a less powerful pump and to respond more quickly to a temporary demand. It also acts as a system shock absorber by smoothing out pulsations.

Presentation Description

In the event of a hydraulic pump failure, the energy stored in an accumulator can provide a limited number of brake applications after landing. Hydraulic System Redundancy Hydraulic system redundancy is achieved by two primary means - multiple systems and multiple pressure sources within the same system. Multiple Pressure Sources. Hydraulic systems often have more than one pump available to pressurise the system.

It is quite common for a system to have one or more engine driven pumps plus one or more electric pumps. In some cases, a manual pump is also incorporated. Some systems only use the electric or manual pumps while on the ground when the engines are not operating.

Others use the electric pump s to provide an additional pressure source during high demand situations such as gear retraction or as the primary pressure source in the event of the loss of the engine driven pump s. When an electric pump is used as the primary pressure source, a second electric pump or a Ram Air Turbine might be incorporated into the system as a backup source of hydraulic pressure.

Provision of multiple pressure sources helps to ensure that the entire hydraulic system is not lost in the event of a single component failure.

Multiple Hydraulic Systems. In many aircraft, flight control surfaces are hydraulically actuated. In these cases, multiple actuators on each surface, powered from multiple hydraulic systems, are essential to ensure that the failure a hydraulic system will not result in loss of control. In modern commercial aircraft, it is common to power the flight control surfaces from three independant hydraulic systems.

The control surface architecture allows for failure of two of those systems without compromising control. Threats Hydraulic systems are subject to several significant threats. These include: System Overheat. The system exceeds its maximum allowable operating temperature and must be de-energized.

Loss of System Pressure. Loss of system pressure can occur in two different ways; loss of fluid or failure of a hydraulic pump.

When you increase the pressure on the inlet side of the pump, leakage will increase around the gears. To reduce the leakage, you must push the bearings and gears closer, causing an increase in friction.

Principle of the Shear Shaft Gear pumps are built using a shear shaft principle. That is, if the pump fails, the shear shaft breaks and this allows each of the gears to rotate in its own part of the system Dept. This phenomenon is similar to a fuse in an electrical system. When the electrical system overloads, the fuse breaks, causing the circuit to break without damaging the rest of the electrical circuit. As the cylinder block rotates, space between the block and the pistons increase, letting in more oil.

As the block rotates from bottom dead center, the reverse occurs and the pistons push oil out through the outlet.

When the pistons move down, the suction caused by the vacuum from the space, created by the movement of the piston, pulls in oil. Changing the angle between the swash plate and the cylinder block gives a longer pumping action and causes more fluid to be pulled in. As the cylinder block rotates, the piston cylinder openings over the inlet and the outlet vary.

When cylinders take in hydraulic fluid and act as the inlet to the pump, then cylinders push the hydraulic fluid out and act as outlet to the pump.

Pumps can be made to move more or less oil volume. Hydraulic System Check Valves Check Valves are hydraulic devices which permit flow of fluid in one direction only. Check Valve Used In Aircrafts Poppet type valve is the preferred type that is used in hydraulics now. The front of the poppet left side of the picture above sits snugly on the hard seat darker shaded areas on the left side.

The poppet works on the following principle. When high pressure fluid with pressure P1 comes in on the left, it forces the poppet open. Thus the fluid is allowed to flow through in one direction only. Check valves are designed so as not to tolerate leakage.

The purpose of the light spring is only to keep the poppet on the seat. Parallel seats are very good except that they are too prone to trapping contaminants between the seat and the poppet.

Pressure Control Pressure limiting device-relief valves Function To limit the pressure of some section of the hydraulic system when the pressure has reached a predetermined level. That pressure level may be considered dangerous and, therefore, must be limited. Principle of Operation The adjustment screw at the top of the pressure relief valve is set for a certain pressure value, let us call it P2.

In general, even with a pressure of P1, the poppet would lift up, except that the spring is strong and has downward force forcing the poppet closed. Poppet will not move until a pressure greater than that required is felt by the system i.

When the pressure increases, the poppet will move up, forcing the excess liquid to move through opening at high velocity. On other side of seat, pressure is zero because the back side of the relief valve is connected to the return line. When the Dept.Now customize the name of a clipboard to store your clips. Both valves also reset when the center system quantity is more than 0.

Since T increases, the pressure P increases. The Captain contacted Company maintenance to discuss options. However, given the operating pressure to psi that most aircraft hydraulic systems generate in combination with the environmental conditions and strict safety criteria under which the system must operate, the hydraulic fluid that is used should have the following properties: High Flash Point. Blog Hydraulic System Advantages and Disadvantages Hydraulic systems will be a familiar topic for you.

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