Hydraulics Flashcards
What are the three hydraulic systems?
A and B:
-Autopilot
-flight controls
-landing gear
-thrust reversers
Standby:
automatic or manual activation to power
-thrust reversers
-rudder
-leading edge slats/flaps (extend only)
- Stby yaw damper
System A. System B
Ailerons. Ailerons
Rudder. Rudder
Elevator and E feel. Elevator and E feel
Flight spoilers 2/wing. Flight spoilers 2/wing
Ground spoilers. LED flaps and slats
Alternate brakes. Normal brakes
No 1 thrust rev No 2 thrust rev
Autopilot A. Autopilot B
Nosewheel steering. Alternate NWS
Landing gear. LG transfer unit
PTU. Autoslats
Tail skid (9ER/9MAX). Yaw damper
Main cargo door (F). Trailing edge flaps
Which components powered by system A are unique to the system?
Ground spoilers
Alternate brakes
No. 1 thrust reverser
Autopilot A
Normal nose wheel steering
Landing gear
Power transfer unit (PTU)
Also, two flight spoilers on each wing
Which components powered by system B are unique to this system?
Leading edge flaps and slats
Normal brakes
No. 2 thrust reverser
Autopilot B
Alternate nose wheel steering
Landing gear transfer unit
Autoslats
Yaw damper
Trailing edge flaps
Also, two flight spoilers on each wing
How are the hydraulic reservoirs pressurized?
System A and B are pressurized by regulated bleed air (45-50 psi pressure relief at 60 psi)
System B reservoir pressurizes the standby reservoir
Pressure indicator in wheel well
What is indicated by RF (white) in the lower display hydraulic indicator and when is it valid?
When hydraulic quantity is below 76% (needs fluid added by maintenance)
Valid only when:
-on the ground with both engines shutdown, or
-after landing with flaps up during taxi in
What is the normal pressurization range of system A and B?
3000 psi +- 200
Max system pressure 3500
What precautions, if any, should be taken when turning ON the ELEC HYD pumps?
Placing both ELEC pumps on at same time may create amperage surge, tripping the hydraulic pump motor circuit breakers in the E/E compartment. (Wait for LOW PRESSURE LIGHT to go out before Turing on other pump)
*limitation: ground operation of electric hydraulic pumps requires minimum 1675 lbs fuel in respective fuel tank
*turn ON system B before A to prevent fluid migration (secure checklist, turn OFF A first)
In the event of a system A engine driven pump leak, what prevents a total system fluid loss?
Standpipe in the reservoir prevents all fluid loss from engine driven pump. 20% left
*if leak develops in electric pump or related lines, or components common to both engine and electric pumps, all fluid/pressure can be lost
*in system B, if leak develops in either pump/related lines/component all fluid/pressure lost
How much system A fluid is available if the fluid is at the top of the standpipe?
Approx 20%
With zero indicated on the system B reservoir, can the PTU still operate?
Yes.
Standpipe supplies fluid to both engine and electric pumps. Fluid to top of standpipe sufficient to power PTU
What’s the purpose of the PTU?
If system B engine pump drops below specific value, it provides system B fluid at a flow rate and pressure sufficient to provide normal rates of operation for the
-autoslats
-leading edge devices.
Operates when (PTU control valve opened)
-airborn
-flaps extended, and
-B pressure drops below 2350 psi
*PTU operation terminated with ALTERNATE FLAPS switch moved to ARM and alt flap switch moved to down
What would cause variations in the Hydraulic Quantity Indications?
During normal operations when:
-system pressurized after engine start
-gear or LEDs
—system A, retract gear, up to 20% drop
—system B, extend LEDs, up to 20% drop
-cold soaking
—long cruise may drop 5-10%
—also prolonged cruise low temp up to 20%
What happens when placing FLT CONTROL switch to STBY RUD?
LOW PRESSURE (Amber) (Sys A or B)
Light extinguishes.
Standby Hyd LOW PRESSURE (Amber) light armed
STBY RUD ON (Amber) illuminated cuz Stby elec Hyd pump on.
—————————————————————
Or, in other words
Activates standby electric pump
Shuts off related hydraulic system pressure to ailerons, elevators, and rudder by closing Flight Control Shutoff Valve
Opens Standby Rudder Shutoff Valve
Deactivates related FLT CONTROL LOW PRESSURE light
Allows standby system to power
-rudder
-thrust reversers
Illuminates STBY RUD ON, FLT CONT annunciator and MASTER CAUTION
What would cause the automatic operation of the Standby Hydraulic System?
-Flaps extended, and
-Airborne, or wheel speed >60 kits, and
-Loss of A or B with the respective FLT CONTROL switch positioned ON
OR
-main PCU Force Fight Monitor (FFM) trips
Automatic operation:
-activated standby motor pump
-opens standby rudder SOV
-allows standby system to power rudder and thrust reversers
-illuminates STBY RUD ON, FLT CONT annunciator, and MASTER CAUTION
When does the STANDBY HYD LOW QUANTITY light illuminate?
When standby reservoir is half empty
