AIRCRAFT HYDRAULIC SYSTEM

What is Hydraulics?

• Hydraulics is derived from the Greek word

- Hydor meaning Water

- Aulos meaning Pipe

Hydraulic System• Hydraulic system has much advantage as

power sources for operating various a/c used. It have many advantage –

•  • 1. Light weight • 2. Easy installation • 3. Simplification of inspection• 4. Minimum maintenance requirement • 5. Ease of detecting leaks

Hydraulic Fluid• PROPERTIES OF HYDRAULIC FLUIDS-

• 1. Low viscosity• 2. High chemical stability • 3. High flash point • 4 High fire point

 

Hydraulic FluidTypes of oil •1. Vegetable base (MIL-H-7644)•2. Mineral base (MIL-H-5606)•3. Phosphate ester base (SKYDROL)• 

Functions of Hydraulic OilFunctions of Hydraulic Oil• It transmits power.It transmits power.

• It lubricates moving partsIt lubricates moving parts

• It seals clearances between It seals clearances between moving partsmoving parts

• It dissipates heat i.e. cooling It dissipates heat i.e. cooling purposespurposes

Simple Hydraulic system

Hydraulic System PartsHydraulic System Parts• Reservoir/TankReservoir/Tank

• AccumulatorAccumulator

• FilterFilter

• Hydraulic PumpHydraulic Pump

• Directional Control ValveDirectional Control Valve

• Pressure Control ValvePressure Control Valve

• Actuator (Cylinder/Motor)Actuator (Cylinder/Motor)

ReservoirStoring oil

It dissipates heat

It allows foreign particles to settle down

Baffle separates inlet line with the return line and allows the air bubbles to escape

Reservoir

FILTERSFILTERS• There are basically three There are basically three

types of Filterstypes of Filters

- Suction line filters- Suction line filters

- Pressure line filters- Pressure line filters

- Return line filters- Return line filters

FILTERSFILTERS

PUMPSPUMPS•Function of the Hydraulic Pump is to convert Mechanical Energy to Hydraulic Energy

Engine driven pump

Tank

Pump

Electrically Driven PumpElectrically Driven Pump

AccumulatorAccumulator• Absorbs the shocks due to rapid Absorbs the shocks due to rapid

pressure variations in a hydraulic pressure variations in a hydraulic systemsystem

• Helps maintain constant pressure Helps maintain constant pressure within hydraulic systemwithin hydraulic system

• Can be used as an emergency Can be used as an emergency source of powersource of power

Tank

Pump

AccumulatorsAccumulators

Tank

Pump

AccumulatorsAccumulators

ROTARY & RECIPROCATING ROTARY & RECIPROCATING TYPESTYPES• Common Pumps in Rotary type are:Common Pumps in Rotary type are:

- Gear Pumps- Gear Pumps- Vane Pumps- Vane Pumps

• Reciprocating type is given by:Reciprocating type is given by:

ACTUATORSACTUATORS• An actuator is a mechanical device for An actuator is a mechanical device for

moving or controlling a mechanism or moving or controlling a mechanism or system. An actuator typically is a system. An actuator typically is a mechanical device that takes energy mechanical device that takes energy & converts it to a desirable form for & converts it to a desirable form for usage or application.usage or application.

Actuator

Pump

Tank

ACTUATORS Contd…ACTUATORS Contd…

Types of ValvesTypes of Valves• There are three main types of There are three main types of

Valves:Valves:

- Pressure Control Valves (relief - Pressure Control Valves (relief valves, pressure regulating valves, pressure regulating valve, pressure reducing valve)valve, pressure reducing valve)

- Directional Control Valves - Directional Control Valves (check valve)(check valve)

- Flow Control Valves (needle - Flow Control Valves (needle valve, throttle check valve etc.)valve, throttle check valve etc.)

Relief valveRelief valve

• This is simply a pressure relief valve. This is simply a pressure relief valve. If a malfunction in the system causes If a malfunction in the system causes the pressure to rise too high, the the pressure to rise too high, the relief valve opens and the fluid relief valve opens and the fluid simply passes back to the reservoir. simply passes back to the reservoir. In virtually all automotive power In virtually all automotive power steering pumps, the relief valve is steering pumps, the relief valve is built into the pump built into the pump

Some Hydraulic SymbolsSome Hydraulic Symbols