servicing hydraulics

hydraulic fluid purpose

transmit and distribute forces to various units to be actuated

manufacturers specify

• Type of liquid 

• Service required

• Temperatures expected inside and outside

• Pressures the liquid must withstand

• Possibilities of corrosion

viscosity

internal resistance to flow

what is the most important property of hydraulic fluid

viscosity

low viscosity

flows easily

high viscosity

flows slowly

hydraulic fluid viscosity

low

types of hydraulic fluid

• Mineral based MIL-H-5606

• Phosphate esters - Skydrol or HyJet

do different types of hydraulic fluid mix

no

what happens if you service with the wrong type of fluid

flush the system and replace the seals

mineral based used in

systems where fire hazard is low

mineral based colour

red

mineral based is produced from

petroleum

phosphate ester based used in

commercial transport category

phosphate ester based advantage

fire-resistant

phosphate ester based disadvantage

not fireproof and can burn

susceptible to contamination from water in the atmosphere

examples of phosphate ester based

skydrol and hyjet

servicing precautions

• use correct fluid

• depressurize before servicing

• perform leak check after servicing

CRJ how many systems

3

system 1 and 2

2 EDPS and 2 ACMP

system 1 and 2 - EDP

primary source of pressure

system 1 and 2 - ACMP

backup and supplementary pressure source during high demand

system 3

2 ACMP

3A ACMP

primary pump

3B ACMP

backup and supplementary pressure source during high demand

ACMP

alternating current motor pumps

synoptic page displays

• Quantity in each reservoir

• Pressure in each system

• Temperature of fluid 

• Pressure source

cessna citation has how many hydraulic systems

2 (main and brake)

oleo strut servicing steps

increase pressure and inflate strut until it starts to move > stop increasing pressure > exposed chrome extends until it matches the chart