Hydraulics

Question 1

How many hyd pumps are on the airplane?
A
6 total:
2 Eng driven pumps
4 AC motor pumps
(PTU makes 7 pumps)
5

2
Q
How many hydraulic systems are on the airplane?
A
3 independent systems
5

3
Q
What are the 6 systems that use hydraulic power?
A
SNLWTF
2. Spoilers
4. Nose wheel steering
3. Landing Gear
5. Wheel Brakes
6. Thrust Reversers
1. Flight Controls
5

4
Q
Can hydraulic fluid be transferred between each system?
A
No
5

5
Q
What are the 3 basic components of the hydraulic systems?
A
1. Reservoir
2. Pumps
3. Accumulators
5

6
Q
What is the purpose of the accumulators?
A
1. Helps to maintain constant pressure by covering transient
demands
2. Helps to avoid cavitation in reservoir
5

7
Q
When will Hyd ACMP 1 or 2 activate on ground and in flight?
Ground:
A
Ground:
1. Flaps > 0
2. TL set to T/O, or
3. GS > 50 kts

Takeoff:
in TOGA, activated for 60 seconds to avoid abrupt hydraulic
pressure variations in an event of engine failure

In-flight:
1. Eng or EDP failure
2. Flaps > 0
5

8
Q
Hydraulic System 1
A
Rudder (Upper Actuator)
Elevator (L Outboard)
Thrust Reverser (Engine 1)
Multi-Function Spoilers (L & R panels 3 & 4)
Ground Spoilers (L & R panel 2)
Outboard Brakes
Emergency Parking Brake
5

9
Q
Hydraulic System 2
A
Elevator (L & R Inboard)
Ailerons (L & R Inboard)
Thrust Reverser (Engine 2)
Multi-Function Spoilers (L & R panels 5)
Ground Spoilers (L & R panel 1)
Brakes (Inboard)
Landing Gear
Nose Wheel Steering
Emergency Parking Brake
5

10
Q
Hydraulic System 3
A
Elevator (R Outboard)
Rudder (Lower Actuator)
Ailerons (L & R Outboard)
5

11
Q
What are some of the important systems run on HYD 2?
A
1. Landing gear
2. Inboard brakes
3. Nose-wheel steering
5

12
Q
What is the PTU?
A
What is the PTU?
The power transfer unit (PTU) is a mechanical pump that uses
HYD 1 POWER to provide HYD 2 PRESSURE
5

13
Q
What is the primary purpose of the PTU?
A
What is the primary purpose of the PTU?

Allows for landing gear retraction and extension in the event that
ENG 2 or EDP 2 fails
5

14
Q
When will the PTU automatically activate?
If system meets requirements
A
When will the PTU automatically activate?
If system meets requirements
During takeoff and landing with flaps > 0, if

1. Flaps > 0
2. Eng 1 not fail
3. Hyd 2 Reservoir Fluid Level above 12%
   then PTU comes on automatically
4. ENG 2 or EDP Fail
   5

15
Q
How is single engine taxi possible if nose wheel steering is
on HYD 2?
A
How is single engine taxi possible if nose wheel steering is
on HYD 2?

Releasing the parking brake commands ACMP 2 to turn on
5

16
Q
What is the primary purpose of HYD 3?
A
What is the primary purpose of HYD 3?

To back up the flight controls
5

17
Q
Why does HYD ACMP 3A pump have an ON switch and HYD
3B have an AUTO position?
A
Why does HYD ACMP 3A pump have an ON switch and HYD
3B have an AUTO position?

1. HYD 3A is primary and has no automation
2. 3B is a backup in the event 3A fails
   5

18
Q
Which hydraulic pump will function if the RAT is the only
source of AC power?
A
Which hydraulic pump will function if the RAT is the only
source of AC power?

Only ACMP 3A (AC ESS Bus)
5

19
Q
In an electrical emergency, what provides hydraulic pressure
to flight controls until the RAT comes online?
A
In an electrical emergency, what provides hydraulic pressure
to flight controls until the RAT comes online?

1. System 3 Accumulator during the 8 seconds it takes to deploy
   RAT
2. RAT powers ACMP 3A once RAT is online
   5

20
Q
What is the purpose of the Hydraulic system 3 accumulator?
A
What is the purpose of the Hyd system 3 accumulator?

Temporarily provides hydraulics to the flight controls during an electrical emergency. (from the beginning of RAT deployment until AC ESS Bus powers the AC pump 3A)
5

21
Q
In an electrical emergency, can HYD 3 system power
requirements overload the RAT?
A
In an electrical emergency, can HYD 3 system power
requirements overload the RAT?

No, there’s a flow limiter valve and pump unloader valve that is used to
reduce the flow and limits pump electrical draw to prevent a RAT
stall
5

22
Q
What kind of hydraulic fluid does the 175 use?
A
What kind of hydraulic fluid does the 175 use?

Skydrol Hydraulic Fluid
5

23
Q
What is the nominal hydraulic pressure?
A
What is the nominal hydraulic pressure?

3000 PSIG
5

24
Q
Hyd ACMP1B and Hyd ACMP2B is located on what bus?
A
Hyd ACMP1B and Hyd ACMP2B is located on what bus?

AC Bus 2 for ACMP1B and AC Bus 1 for ACMP2B
Opposite buses
5

25
Q
When an engine flameout occurs, what happens to the
hydraulic EDP of that respective engine?
A
When an engine flameout occurs, what happens to the
hydraulic EDP of that respective engine?

Depressurizes EDP to facilitate WML start
5

26
Q
Electric Hyd pumps auto turn on when?
A
Electric Hyd pumps auto turn on when?

Ground:
1. Flaps > 0
2. TL set to T/O, or
3. GS > 50 kts

Takeoff:
in TOGA, activated for 60 seconds to avoid abrupt hydraulic pressure variations in an event of engine failure

In-flight:
1. Eng or EDP failure
2. Flaps > 0

Parking Brake:
ACMP2 when on ground and Eng 1 is running and PB is
released
ACMP 2 when on ground during Eng 1 start and PB has been applied in last 6 mins
5

27
Q
Which bus is hydraulic Pump 3A on?
A
Which bus is hydraulic Pump 3A on?

Its on AC ESS Bus
5

28
Q
What color is hydraulic fluid?
A
What color is hydraulic fluid?
* Transparent Skydrol, red5606 in struts
5

29
Q
What’s shutting down the mechanical hyd pump do? How to shut it off?
A
What’s shutting down the mechanical hyd pump do? How to shut it off?
Separates the pump from the hyd system. *
Eng. has to be turned off
5

30
Q
Can you shutoff hydraulics if it’s over heating? Will it keeps the hydraulics from overheating?
A
Can you shutoff hydraulics if it’s over heating? Will it keeps the hydraulics from overheating?
You can shut down Eng .pump following the QRH. Hydraulics fluid should be
cooling the system if no pumps is overheating the system.
–

31
Q
Where is hydraulics 2 located? What’s in that bay?
A
Where is hydraulics 2 located? What’s in that bay?
Behind right wing .FO side
Has the PTU
–

32
Q
Can the backup elec pump for Sys 2 retract the gear? ACMP
A
Can the backup elec pump for Sys 2 retract the gear? ACMP
Yes but very slow
–

33
Q
The landing gear is? Ailerons? Cargo doors?
A
The landing gear is? Ailerons? Cargo doors?
Landing gear is electrically Controlled and hydraulically operated * Ailerons is mechanically controlled and hydraulically operated
Doors are all mechanical controlled and operated
–

34
Q
When is the Hyd Eicas messages?
A
When is the Hyd Eicas messages?
100C ̊high temp caution
125 shut off
145C ̊warning
–

35
Q
What’s bootstrap?
A
What’s bootstrap?
What keeps the reservoir fluid pressured and no air inside
To keep pressure in the system.
Mostly used for parking break
–

36
Q
RAT is prevented to stall?
A
YES
A flow limiter valve and pump unloader valve keeps hyd 3 from stalling the Rat (2
gal/min) till it gets fully powered