1.
AIRCRAFTS HYDRAULICSYSTEM

2.
INTRODUCTION Hydraulics is based on the fact that liquids are incompressible Hydraulic system is a system where liquid under pressure is used to transmit energy In it a hydraulic pump converts mechanical power to hydraulic power An actuating cylinder converts hydraulic power to mechanical power.

3.
A SIMPLE HYDRAULIC SYSTEM

4.
DEVICES USING HYDRAULIC SYSTEMS IN AIRCRAFTS Gun turrets Auto pilot Shock absorption systems Dive, landing, speed and flap brakes Bomb bay doors Doors and hatchways Landing gears, wing flaps, etc…

5.
PRINCIPLES OF OPERATION Governed by Pascal’s law The oil is in contact with both sides of the piston head but at different pressures. High pressure oil may be pumped into either side of the piston head. The selector valve determines to which side of the actuating cylinder the high pressure oil (red colored side) is sent.

6.
PARTS OF THE POWERSYSTEM RESERVOIR ACCUMULATOR FILTER POWER PUMP SYSTEM RELIEF VALVE PRESSURE REGULATOR

7.
POWER SYSTEM

8.
RESERVOIRFUNCTIONS Holds reserve supply oil to account for normal leakage, emergency supply of oil, volume changes, thermal contraction of oil, Provides pressure head on the pump, a place to remove air or foam from liquid, air space for expansion of the oil due to temperature changes etc

9.
RESERVOIRCONSTRUCTION Material: 5052 aluminium Size: takes into account all oil volumes in operational requirements, thermal expansion, leakage, etc. Shape: domed cylindrical shape, due to ease of construction & mounting

10.
ACCUMULATORSPRINCIPLE Gas valve lets in compressed gas at ½ system pressure Diaphragm pops up & oil is sent through system When system pressure>accumulator pressure, diaphragm deploys

11.
ACCUMULATORSUSES Absorbs the shocks due to rapid pressure variations in a hydraulic system Helps maintain a constant pressure within the hydraulic system Helps the hydraulic pump under peak pressure loads It is an emergency source of power Spherical shape is preferred for accumulators

12.
POWER PUMPSFUNCTION Is to change mechanical horsepower to hydraulic horsepowerTYPES Gear pumps: move fluid based upon the number of gear teeth and the volume spacing between gear teeth. Piston pumps: move fluid by pushing it through the motion of the pistons within the pump

13.
POWER PUMPSPRINCIPLES OF GEAR PUMPS The liquid from the reservoir is pushed between the gear teeth. The oil is moved around to the other side by the action of the drive gear itself and sent through the pressure line.

14.
POWER PUMPSPRINCIPLES OF RECIPROCATING PISTON PUMP 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

15.
SYSTEM RELIEF VALVEPRINCIPLE The adjustment screw is set for a certain pressure value P2. When the pressure increases, the poppet will move up, forcing the excess liquid in

16.
Douglass Pressure Regulator high pressure oil from the power pump opens valve C and also act on piston A piston A pushes Ball B off seat D, the oil goes through passage D into the center chamber back to the reservoir.

17.
HAND PUMPS

18.
Selector Valves Position (1) is the position of the selector valve, for example, upon the extension of the landing gear or the lowering of flaps. Position (2) is the position of the selector valve upon retraction of the landing gear or the raising of the flaps

19.
FLOW EQUALISER If wing air loads on one wing are greater than on other, during wing sweep back or sweep forward, motion occurs unevenly. To synchronize wing sweep back or sweep forward flow equaliser used flow equalizer is made up of two power pumps placed side by side in which the drive gears of both pumps are connected

20.
ACTUATION CYLINDER The function is to take the pressure & hydraulic fluid flow & change them into linear or rotary motion. Single piston double rod is an equal displacement cylinder used in aileron system or automatic guidance system Double piston-double rod actuating cylinder used in bomb bay doors

21.
ADVANTAGES It is lighter in weight than alternate existing systems. It is dead beat, that is, there is an absence of sloppiness in its response to demands placed on the system. It is reliable; either it works or doesnt. It can be easily maintained. It is not a shock hazard; it is not much of a fire hazard. It can develop practically unlimited force or torque.

22.
CONCLUSION Hydraulic systems determine flight worthiness, usability and reliabity.