Hydraulics Flashcards
What parts use hydraulic system 1?
Elevator (left, outboard), Rudder (upper actuator), Thrust Reverser (Engine 1), Multi-function Spoilers (Left and right panels 3 and 4), Ground spoilers (Left and right panel 2), Outboard brakes, Emergency Parking Brake
What parts use hydraulic system 2?
Elevator (left and right inboard), Ailerons (left and right inboard), Thrust Reverser (Engine 2), Multi-function Spoilers (Left and right panels 5), Ground spoilers (Left and right panel 1), Inboard brakes, Emergency Parking Brake, nose wheel steering, landing gear
What parts use hydraulics system 3?
Elevator (Right outboard), Rudder (Lower actuator), Ailerons (Left and right outboard)
What is hydraulic system 1 composed of?
A reservoir, an Engine Driven Pump, an AC Motor Pump ACMP used as a back-up for the EDP, and 2 accumulators
What is hydraulic system 2 composed of? How is it different from hydraulic system 1?
The same except: the hydraulic system allows for single-engine taxi. With the selector knob in the AUTO position and only engine 1 operating, releasing the parking brake will automatically activate the ACMP 2 to provide hydraulic power for nose wheel steering and the inboard brakes. The PTU Power Transfer Unit uses hydraulic power from system 1 to provide hydraulic pressure to system 2. With the knob in the auto position the system logic activates the PTU if engine 2 fails or EDP 2 fails to aid in landing gear operation.
What is hydraulic system 3 composed of?
A reservoir, 2 ACMP pumps A and B (pump A is primary (either ON or OFF) pump B is backup (AUTO, ON, OFF where in AUTO the ACMP B will automatically turn on with a failure of ACMP A), 1 accumulator
How does hydraulic system 3 function during an electrical emergency?
The system 3 accumulator will provide hydraulic power to the associated flight controls from beginning of RAT deployment until AC ESS BUS powers the ACMP 3A
When does hydraulic system 1 and 2 ACMPs automatically activate in flight?
System logic activates the ACMP in case of: EDP failure or flaps selected to any position greater than 0 degrees
When does hydraulic system 1 and 2 activate on the ground?
System logic activates the ACMP in case of: flaps selected to any position greater than 0 degrees AND thrust levers set to takeoff thrust OR ground speed greater than 50kts
What the the systems 1 and 2 accumulators used for?
Each system has an accumulator used for shock absorption (transient demands) and another for emergency parking brake use
What is the system 3 accumulator used for?
During an electrical emergency to provide hydraulics to the flight controls
How many hydraulic systems are on the airplane?
3 Independent Systems
What systems use hydraulic power?
flt controls: Flight controls, spoilers
stopping: landing gear, nose wheel steering, wheel brakes, thrust reversers
Can hydraulic fluid be transferred between each system?
No
How many hydraulic pumps are on the airplane?
6 total, 2 EDPs and 4 ACMPs
What are the basic components of the hydraulic systems?
Reservoir, pumps, accumulators
What is the purpose of the accumulator?
Helps maintain a constant pressure by covering transient demands, Helps to avoid cavitation (which can lead to failure) (high vacuum conditions create vapor bubbles within the oil which are carried to the pressure side, collapse, thus cavitation)
When will ACMP 1 or 2 automatically activate on the ground?
Flaps greater than 0, TL set to T/O, or Groundspeed greater than 50kts
When will ACMP 1 or 2 automatically activate in flight?
Engine failure or EDP failure, Flaps greater than zero
What are some important items controlled by HYD 2 system?
Landing gear, nose wheel steering, inboard brakes
What is the PTU?
Power transfer unit, a mechanical pump that uses HYD 1 POWER to provide HYD 2 PRESSURE (No exchange of fluid)
What is the primary purpose of the PTU?
To allow landing gear retraction and extension in the event of an engine 2 or EDP 2 failure
When will the PTU automatically activate?
During takeoff and landing with flaps greater than 0 IF engine 2 fails or EDP 2 fails
How is single engine taxi possible if nose wheel steering is on HYD 2?
Releasing the parking brake activates ACMP 2
What is the primary purpose of the HYD 3 system?
Back-up for the flight controls
Why does HYD ACMP 3A pump switch have an ON position and HYD ACMP 3B have an AUTO position?
HYD ACMP 3A pump is primary and has no automation, HYD ACMP 3B pump is a back-up and automatically activates if ACMP 3A fails
What, if any, HYD ACMP will function if the RAT is the only power source?
HYD ACMP 3A only
In an electrical emergency, what provides hydraulic pressure to flight controls until the RAT comes online?
HYD 3 Accumulator, after 8 seconds the RAT will power the ACMP 3A
In an electrical emergency can HYD 3 system power requirements overload the RAT?
No. A flow limiter valve is used to reduce flow and limits pump electrical power draw to prevent a RAT stall
What nominal pressure does the hydraulic system operate at?
3,000 PSI
Which electric hydraulic pumps are automatically switches on for takeoff and landing?
System 1 and 2 electric pumps
The PTU Power Transfer Unit transfers hydraulic power from system 1 to system 2 to guarantee normal operation of which systems?
The landing gear
How many electric hydraulic pumps are used for each system?
system 1 and 2 have 1 one electric hydraulic pump each, system 3 has two electric hydraulic pumps
Hydraulic system 3 powers which flight controls?
Rudder, right elevator, and both ailerons
What systems do the hydraulics power?
Primary and secondary flight controls, landing gear, brakes, nosewheel steering, thrust reversers
Are the hydraulic systems independent?
Yes
What type of hydraulic fluid is used?
Skydrol Hydraulic Fluid
What are the main components of the hydraulic system?
2 EDPs, 4 electric hydraulic pumps, 1 PTU, and 3 reservoirs
When are the hydraulic ACMPs used?
For takeoff, landing, engine failure, EDP failure
What is the purpose of the PTU?
To provide a means for landing gear extension and retraction if hydraulic system 2 is not operational
When will the PTU not be activated?
If the airplane is on the ground and the airspeed is below 50kts
Where is hydraulic system 1 located?
Left, center fuselage bay
What systems are on hydraulic system 1?
Left Outboard Elevator PCU
Upper Rudder PCU
Left Thrust Reverser
Multifunction Spoilers Pairs 3 & 4
Ground Spoiler (Closer to root than multifunction spoilers) Pair 2
Outboard Brakes
Emergency/Parking Brake
What systems are on hydraulic system 2?
Both Inboard Elevator PCUs
Both Inboard Aileron PCUs
Right Thrust Reverser
Multifunction Spoilers Pair 5
Ground Spoiler Pair 1
Inboard Brakes
Emergency/Parking Brake
Nosewheel Steering
Landing Gear
What systems are on hydraulic system 3?
Right Outboard Elevator PCU
Lower Rudder PCU
Both Outboard Aileron PCUs
Where is hydraulic system 3 located?
Aft fuselage
Where is hydraulic system 2 located?
Right center fuselage
What do all electric pumps, except for Pump 3A and the PTU, do in auto mode?
In AUTO:
- ACMP 1,2 turn on for TO/L (WHEN FLAPS GREATER THAN 0 and TLA TO or GS > 50kts) or when EDP fail or Engine fail
(When TLA TO, the pumps will turn on for 60sec to avoid hydraulic pressure variations in an engine failure)
- ACMP 3B turns on if 3A fails
What does the PTU do in Auto Mode?
Activates the PTU when:
Engine 2 or EDP 2 fails on TO/L and flaps are not set to zero
Why would you need to turn the hydraulic pump to the ON position instead of AUTO?
If the SPDA, which controls the AUTO system logic, fails, the ON positions will go directly to the ICC Integrated Control Circuits of each hydraulic pump.
What could cause a hydraulic fluid overheat condition?
Failure of a pump compensator, resulting in a rapid rise (~1min after failure) of hydraulic fluid temperature.
What protects against a hydraulic overheat condition?
Systems 1 and 2 have temperature switches that will automatically close the firewall SOV (EDP) and ACMP OFF if the temperature is over 125deg C. You cannot turn the EDP back on.
System 3 temperature switches will automatically turn both switches OFF at 125deg C.
What mechanically happens when the RAT is deployed? Discuss the PUV and FLV
SPDA 2 commands the PUV Pump Unloader Valve to Open which reduces the fluid flow through ACMP 3A during pump start up and energizes the FLV Flow Limiter Valve which reduces the fluid flow to the flight controls at ~2gal/min which ALLOWS THE RAT TO SPIN UP FASTER TO ITS OPERATIONAL SPEED. When the RAT is spooled up and is powviding power to the AC ESS BUS, ACMP 3A will start and the PUV will be commanded to close and system pressure will increase to normal. The FLV will remain on as long as the RAT is deployed and is producing power.
Why is there a hydraulic pressure accumulator for system 3?
When both engines lose power, ACMP 3A will momentarily become offline. The accumulator will provide hydraulic pressure to the flight controls until ACMP 3A is restarted by the RAT providing electricity to the AC ESS BUS.
When are hydraulic systems 1 and 2 pressurized?
Engine start
The hydraulic system allows for single engine taxi. When engine 1 is started and the parking brake is released, what happens?
ACMP 2 turns on to provide NWS and inboard brakes (along with the other systems on hyd sys 2)
If engine 2 is started before engine 1, why must ACMP 1 be turned ON?
It will provide hydraulic pressure to the brakes
What is the purpose of the cold weather operations hydraulic system start sequence?
It raises the hydraulic fluid to the minimum operational temperature.
When will ACMP 1 and 2 come on for Takeoff and Landing? When will they switch back off?
When Slat Flap not zero, TLA TO or GS > 50kts
They will turn off again once flaps are zero
Why is system 3 3A ACMP not turned on for TO/L?
There are no high flow demands on system 3
When do hydraulic pumps 1 and 2 turn on for landing? When do they turn back off?
ON when flaps are extended
OFF 1min after airspeed is below 50kts
What are the 2 green circles on the hydraulic system synoptic page?
The firewall SOV positions
ACMP
Alternating Current Motor Driven Pump
PSID
Pound per Square Inch Differential
Why is single engine taxi on engine 2 performed with HYD SYS 1 Electric Pump ON?
If single engine taxi will be performed with Engine 2 operating, Hydraulic Sys 1 ELEC PUMP Knob must be set to ON to ensure that the Hydraulic System 1 is pressurized.
In order to maintain hydraulic pressure on both brake systems the Hydraulic Pump 1 must be kept ON throughout the taxi.
