Aircraft Hydraulic Reservoir Fluid Low Level Switch

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Aircraft Hydraulic Reservoir Fluid Low Level Switch 

 

Aircraft hydraulic reservoir store hydraulic fluid.The hydraulic fluid level of reservoir measured by fluid quantity transmitter and transmitted signal to system computer to display fluid level in the cockpit.Low level switch on the reservoir generate alert signal when fluid level in the reservoir critically low.

                                       

                                                      Fig 01 Hydraulic Reservoir                        

Aircraft hydraulic system supplies pressurized hydraulic fluid to aircraft flight control,landing gear and engine thrust reverser system actuator through metal pipelines.During an aircraft operation there is a possibility of pipelines or actuator may damage cause fluid leakage through pipelines or actuator.If hydraulic pump continue to run in absence of hydraulic fluid ,pump will heat up.This will create  hazardous situation for flight.Thus, alerting reservoir low level signal important for flight crew to take appropriate action and ensure safe flight.

 

Reservoir fluid  quantity transmitter also act as a low level switch if low level switch inoperative. Although, the threshold value for generating low level alert by quantity transmitter is lower than the threshold value of  low level switch .The availability of these two sensor on reservoir enhance system reliability and make aircraft operation more safe.

 

Working Principle of Low Level magnet reed switch

Here we will discuss magnet reed type low level switch.Low level switch consists of body assembly, magnet,cylinder float and magnet reed switch.The other end of assembly has electric connector which transmit signal.

Body assembly: Provide Support to assembly

Cylinder float:This move with change in reservoir fluid level.

Magnet:This moves with float and actuate magnet reed switch with help of magnetic field.

Magnet reed switch: Transmit Signal when contact close.

 

Low Level Switch in Normal mode


Fig 02 Low Level Switch in Normal Mode

When reservoir fluid level normal, Cylinder float away from magnet reed switch.Due to absence of magnetic field magnet reed switch contact away from each other  and circuit will remain open.There will be no transmission of signal to connector.



Fig 03 Low Level Switch in Alerting Mode

When fluid level in the reservoir decrease to minimum level,cylinder float will move down toward magnet reed switch. The magnetic field of magnet will move the  magnet reed switch contacts together and close the circuit.This close of circuit transmit signal to connector and generate alert signal in the cockpit. 

 

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