Aircraft Hydraulic Systems

|
All materials on our website are shared by users. If you have any questions about copyright issues, please report us to resolve them. We are always happy to assist you.
 5 views
of 37

Please download to get full document.

View again

Description
Air craft hydraulic system INTRODUCTION Hydraulics is based on a very simple fact of nature - you cannot compress a liquid. You can compress a gas (think about putting more and more air into a tire, the more you put in, the higher the pressure). If you're really strong you can compress a solid mass as well. But no matter how much pressure you apply onto a liquid, it isn't possible to compress it. Now if you put that liquid into a sealed system and push on it at one end, that pressure is transmi
Share
Tags
Transcript
   Air craft hydraulic system INTRODUCTION Hydraulics is based on a very simple fact of nature - you cannot compress a liquid. Youcan compress a gas (think about putting more and more air into a tire, the more you putin, the higher the pressure). If you're really strong you can compress a solid mass aswell. But no matter how much pressure you apply onto a liquid, it isn't possible tocompress it. Now if you put that liquid into a sealed system and push on it at one end,that pressure is transmitted through the liquid to the other end of the system. The pressure is not diminished. Aircraft Hydraulics Definition It is a system where liquid under pressure is used to transmit this energy. Hydraulicsystems take engine power and convert it to hydraulic power by means of ahydraulic pump. This power can be distributed throughout the airplane by meansof tubing that runs through the aircraft. Hydraulic power may be reconverted tomechanical power by means of an actuating   cylinder, or turbine.(1) - A hydraulic pump converts mechanical power to hydraulic power (2) - An actuating cylinder converts hydraulic power to mechanical power (3) - Landing Gear (4) - Engine power (mechanical HP)If an electrical system were used instead of a hydraulic system, a generator would takethe place of the pump and a motor would take the place of the actuating cylinder    1   Air craft hydraulic system Some Hydraulic Systems in Aircrafts 1.Primary control boosters2.Retraction and extension of landing gear 3.Sweep back and forth of wings4.Opening and closing doors and hatchways5.Automatic pilot and gun turrets6.Shock absorption systems and valve lifter systems7.Dive, landing, speed and flap brakes8.Pitch changing mechanism, spoilers on flaps9.Bomb bay doors and bomb displacement gears 2.Principles of Operation Part of the hydraulic system is the actuating cylinder whose main function is to changehydraulic (fluid) power to mechanical (shaft) power. Inside the actuating cylinder is a piston whose motion is regulated by oil under pressure. The oil is in contact with bothsides of the piston head but at different pressures. High pressure oil may be pumpedinto either side of the piston head.The selector valve determines to which side of the actuating cylinder the high pressureoil is sent. The piston rod of the actuating cylinder is connected to the control surface.As the piston moves out, the elevator moves down. As the piston moves in, the elevator moves up. The selector valve directs the high pressure oil to the appropriate side of the piston head causing movement of the piston in the actuating cylinder. As the pistonmoves, the oil on the low pressure side returns to the reservoir since return lines haveno pressure!The differential in oil pressure causes movement of the piston. The force generated bythis pressure difference can be sufficient to move the necessary loads. Each cylinder in   2   Air craft hydraulic system the plane, boat, etc., is designed for what it must do. It can deliver the potential it wasmade for; no more, no less. Air loads generally determine the force needed in aircraftapplications. Hydraulic System A hydraulic system transmits power by means of fluid flow under pressure. The rate of flow of the oil through the system into the actuating cylinder will determine the speedwith which the piston rod in the actuating cylinder extends or retracts. When thecylinder is installed on the aircraft, it is already filled with oil. This insures that no air  bubbles are introduced into the hydraulic system, which can adversely affect theoperation of the system. Pascal’s Theory In a confined stationary liquid, neglecting the effect of gravity, pressure is distributedequally and undiminished in all directions; it acts perpendicular to the surface ittouches. Because the actuating cylinder is not vented, the force delivered through the piston to the surface of the fluid is translated into a pressure on the surface of the fluid.The pressure (p) acting on the incompressible oil does work [(pressure) x (Area of  piston) x (piston's stroke) = Work]. 3.Hydraulic Pressure Regulated Power System The system in drawing below represents a pressure regulated power system comprisedof two parts:1) the power system, and2) the actuating system part of the overall hydraulic system.   3   Air craft hydraulic system Parts of the Power System 1.  Reservoir  -- holds an extra supply of fluid for system from which oil was drawnwhen needed, or oil was returned to it when not needed.2.  Accumulator  -- absorbs pulsation within the hydraulic system and helps reduce linehammer effects (pulses that feel and sound like a hammer has hit thehydraulic tubes). It is an emergency source of power and it acts as another reservoir.3.  Filter  -- removes impurities in the hydraulic system and in the reservoir. Thereservoir has one big filter inside the tank.4.  Power Pump -- it changes mechanical horsepower (HP) to hydraulic HP.5. System Relief Valve -- relieves pressure on system as a safety.measure and takesover as a pressure regulator when pressure regulator fails.   4
Related Search
We Need Your Support
Thank you for visiting our website and your interest in our free products and services. We are nonprofit website to share and download documents. To the running of this website, we need your help to support us.

Thanks to everyone for your continued support.

No, Thanks