29A Hydraulic Power-Monitoring and Indication

 

TTP	B1-L3	ATA 29A
Beech 90 Series	B2-L3	Hydraulic Power – Monitoring and indicating

Hydraulic Fluid Low-Level Sensor

A hydraulic fluid low-level sensor is on the motor end of the powerpack. A HYD FLUID LO annun- ciator illuminates when a low fluid exists. Engine bleed air, regulated to 18 to 20 psi, is plumbed into the fill reservoir to prevent cavitation of the pump.

 

       A yellow HYD FLUID LO annunciator on the glare shield illuminates when the hydraulic fluid in the secondary reservoir becomes low. An  optical  sensing  unit  on  the  motor end of the power pack contains the light source, sensor,  and  switching  circuitry  to  trigger  the fluid  low  annunciator.  The  unit  also  contains an integral self-test circuit that can be activated by a pushbutton on the pilot inboard subpanel. To prevent intermittent or spurious annunciator illumination,  the sensing and test circuitry has incorporated into the circuitry a time delay of up to 5 seconds to illuminate and 15 seconds to extinguish the annunciator light. If a HYD FLUID LOW light is illuminated, the landing gear prob- ably will  not extend with the  powerpack. The King Air C90A/B/GT/GTi has no backup timer mechanism to protect the pump from running dry. Once the up or down cycle has been initiated with a lack of fluid in the system, the only way to stop the powerpack pump from running is to pull the 2-amp circuit breaker adjacent to the landing gear handle.

PTP  Beech 90 Series	B1	LOC	FOT		R/I	MEL	TS
	B2	LOC	FOT		R/I	MEL	TS