737 Systems: Hydraulics

Question 1

What are the three hydraulic systems?

Answer 1

A, B, and Standby

Question 2

Which components powered by System A are unique to this system?

Answer 2

-Landing Gear
-Normal Nose Wheel Steering
- Thrust Reverser 1
-PTU
-Alternate Brakes
-Ground Spoilers
-Autopilot A

Question 3

Which components powered by System B are unique to this system?

Answer 3

-Leading Edge Flaps and Slats
-Normal Brakes
-Thrust Reverser 2
-Autopilot B
-Alt Nose Wheel Steering
-Landing Gear Transfer Unit
-Autoslats
-Yaw Damper
-Trailing Edge Flaps

Question 4

How are the hydraulic reservoirs pressurized?

Answer 4

System A and B are pressurized by Bleed Air, the Standby system recovers its Bleed Air Pressure from System B.

Question 5

What condition is indicated by RF(white) on the Lower Display Hydraulic Indicator and when is it valid?

Answer 5

That hydraulic quantity is below 76%

Valid when the aircraft is on the ground with BOTH engines shut-down, OR after landing with flaps UP during taxi-in

Question 6

What is the normal pressurization range of System A and B?

Answer 6

3000psi, +/-200psi

Question 7

What precautions, if any, should be taken when turning on the ELEC HYD pumps?

Answer 7

For extended ground operations, there must be 1675lbs of fuel in the associated main tank

Question 8

In the event of a System A Engine Driven Pump leak, what prevents a total system fluid loss?

Answer 8

The standpipe, which keep at least 20% full for the electric pump

Question 9

How much fluid is available if the fluid is at the top of the standpipe?

Answer 9

20%

Question 10

With zero indicated on the System B reservoir, can the PTU still operate?

Answer 10

Yes, due to the standpipe i n the System B reservoir

Question 11

What is the purpose of the PTU?

Answer 11

To ensure System B fluid at a flow rate and pressure sufficient to provide normal rates of operation for the Autoslats and Leading Edge Devices in the event the SYS B ENG PUMP output pressure drops below a specific value

Question 12

What could cause variations in the Hydraulic Quantity Indications?

Answer 12

-Pressurization after engine start
-Landing Gear or Leading Edge devices (20% in the respective fluid quantity)
-Cold Soaking

Question 13

What happens when placing a FLT CONTROL switch to STBY RUD?

Answer 13

-Activates the Standby Electric motor-driven pump
-Closes the Flight Control SOV (Loss of Ailerons, Elevators, and Rudder)
-Open the Standby Rudder SOV
-Deactivates the FLT CONTROL LOW PRESSURE light when the Standby Rudder SOV opens
-Allows the Standby System to power the rudder and thrust reversers
-Illuminates the STBY RUD ON, FLT CONT annunciator, and MASTER CAUTION lights

Question 14

What would cause the automatic operation of the Standby Hydraulic System?

Answer 14

(Think critical phase of flight)

-Flaps extended
-Airborne, or wheel speed > 60kts
-Loss of System A OR B, WITH the respective FLT CONTROL switch ON

OR

-Main PCU Force Flight Monitor trips

Question 15

When does the STANDBY HYD LOW QUANTITY light illuminate?

Answer 15

When the Standby Reservoir is approx half empty

Question 16

Does a leak in the Standby Hydraulic System affect the other hydraulic systems?

Answer 16

System A will be unaffected, but System B quantity will fall to at least 70%