Hydraulics Flashcards
How many hydraulic systems are on the aircraft?
- 3
What systems use hydraulic power?
- Flight controls
- Spoilers
- Landing gear
- Nose wheel steering
- Wheel brakes
- Thrust reversers
Can hydraulic fluid be transferred between systems?
No
How many HYD pumps are there?
6, two engine-driven pumps (EDP) and four AC motor pumps (ACMP)
What are the basic components of the HYD systems?
- reservoir
- pumps
- accumulators
What is normal HYD pressure?
3000 PSI
How would you be alerted to a HYD low quantity or overtemp?
The HYD synoptic and EICAS
Where would I find a visual representation of the HYD system operation and parameters?
On the HYD synoptic page
Why wait after power-up prior to turning on any hydraulic pumps
To allow the flight controls to complete their built-in tests
How long after power-up before any HYD pumps should be turned on and why?
3 mins, to allow flight controls to complete built-in checks
What is the normal and alternate pump for each system?
- Systems 1 and 2: Engine driven pump, electric is backup
- System 3: 2 AC pumps, A is primary B is secondary. System operates completely automatically when the switches are in AUTO
What is the primary power source for HYD systems 1 and 2?
The respective engine driven pump (EDP)
What is used as a backup for the EDP?
The AC electric HYD pump
When is the electric HYD pump activated?
With the electric HYD pump selector knob in AUTO, whenever an EDP fails or for takeoff when the flaps are not set to the 0 position and the thrust lever are set to takeoff thrust or ground speed > 50 knots and for landing when flaps > 0
Why does electric HYD pump 2 automatically come on after engine 1 is started and the parking brake is released?
To provide nosewheel steering and inboard brakes during a single-engine taxi
What is the purpose of the accumulator?
- Helps maintain constant pressure by covering transient demands
- Helps to avoid pump cavitation
How would you be alerted to a HYD low quantity or overtemp?
On the EICAS and confirmed on the HYD synoptic
Can we disable the engine driven hydraulic pump?
No, but you can close the HYD SOV using the ENG PUMP SHUTOFF button which will isolate the pump.
What happens when you push the SYS 1 and SYS 2 ENGINE PUMP SHUTOFF guarded buttons?
Closes the HYD SOV, isolating the respective engine driven pump (EDP) from the associated system
Where in the flow is the HYD SOV, before or after the engine? Could the engine get hot if you close it? How else could you close it besides the HYD ENG PUMP SHUTOFF?
- Before the engine
- Yes the engine could get hot
- Pulling the associated fire handle
What is the PTU, how does it work and why?
- Power transfer unit
- Mechanical pump that uses SYS 1 HYD press and SYS 2 HYD fluid to assist in gear retraction and extension in the event of an engine 2 or EDP 2 failure
- No fluid transfer occurs
How can you turn on the PTU?
Rotate the PTU control knob from AUTO to ON
When will the PTU automatically activate if the PTU control knob is in the AUTO position?
Flaps >0, if:
- Engine 2 fails, or
- EDP 2 fails (HYD pump)
Why do we need a PTU when the #2 electric pump is backup to the #2 engine pump?
The flow rate on the #2 electric pump is insufficient to operate the landing gear
What would you expect the FADEC to do with the HYD system 1 or 2 in the event of an engine flameout?
It depressurized the respective engine driven pump so as to facilitate engine windmill rpm (reduces torque for a restart)
How is single engine taxi possible if nose wheel steering is on HYD 2?
Releasing the parking brake activates ACMP 2 if the # 2 EDP is not operating
What causes SYS 2 ELEC PUMP to operate during single engine taxi?
On the ground, after starting engine 1, releasing the parking brake will automatically activate electric pump 2 to allow single engine taxi
What is the primary purpose of HYD 3 system?
Backup for the flight controls
Why are HYD ACMP 3A and 3B pump switch positions ON and AUTO respectively?
- HYD ACMP 3A is primary and has no automation
- HYD ACMP 3B is a backup and automatically activates if 3A fails when the
Why are the #3 electric pump B OFF-AUTO-ON and #3A is only ON-OFF?
Because #3B is a backup to #3A electric pump when the pump is in AUTO
What is the purpose of ELEC PUMP 1 and 2?
Used as a backup to their respective engine driven pump (EDP)
What does the ON position do on HYD systems 1 and 2 ELEC PUMP knob?
Override the system logic and turns the respective electric pump on
What happens when the SYS 1 (2) ELEC PUMP selector knob is in AUTO?
Activates the electric pump whenever the EDP fails or when flaps are selected to any position other than zero. For takeoff and landing the pumps are automatically activated when:
- Thrust levers set to takeoff thrust
- Weight on wheels switch indicates in flight
- Groundspeed > 50 knots
What HYD ACMP will function if the RAT is the only power source?
HYD ACMP 3A only
In an emergency and before the RAT comes online, what provides HYD pressure to flight controls?
- HYD 3 accumulator
- After 8 secs the RAT will power up ACMP 3A via the AC ESS BUS
What provides HYD pressure from system 3 during an electrical emergency?
Initially, an accumulator provides the pressure until the RAT is deployed and AC ESS BUS is powered. System then returns to HYD system electric pump A (B is a backup)
In an electrical emergency can HYD 3 system power requirements overload the RAT?
No. A flow limiter valve is used to reduce flow and limit pump electrical power draw to prevent a RAT stall
Explain how the two dedicated valves in HYD system 3 work during an electrical emergency?
The pump unloader and flow limiter valves will reduce the amount of electricity used by HYD sys electric pump A so as not to stall the RAT
What systems use HYD system 1?
G - ground spoilers panel 2 both sides E - elevator L outboard T - thrust reverser engine 1 M - multifunction spoiler panels 3 and 4 O - outboard brakes R - rudder upper actuator E - emergency parking brake
What is the flow rate of HYD system 1 and 3 EDP?
11.5 GPM
What is the flow rate of HYD system 3 electric HYD pumps>
3.0 GPM
What systems use HYD system 2?
G - ground spoiler panels 1 I - inboard brakes M - multifunction spoiler panels 5 E - elevator L and R inboard T - thrust reverser engine 2 A - ailerons L and R inboard L - landing gear N - nosewheel steering E - emergency parking brake
What are some important items controlled by HYD 2?
- Landing gear
- Nosewheel steering
- Inboard brakes
The HYD PBIT will not run if the reservoir temp is below what?
10C
What systems use HYD 3?
E - elevator R outboard
A - ailerons outboard
R - rudder lower actuator
Using RAT power if HYD pump 3A fails will 3B operate?
No. HYD pump 3B is powered by AC BUS 2 which will be unpowered using RAT power
