Hydraulics

Question 1

How many hydraulic systems are on the airplane?

Answer 1

3 independent systems

Question 2

What are the 6 systems that use hydraulic power?

Answer 2

1. Flight Controls
2. Spoilers
3. Landing Gear
4. Nose wheel steering
5. Wheel Brakes
6. Thrust Reversers

Question 3

Can hydraulic fluid be transferred between each system?

Answer 3

No

Question 4

What are the 3 basic components of the hydraulic systems?

Answer 4

1. Bootstrap Reservoir
2. Pumps
3. Accumulators

Question 5

What is the purpose of the accumulators?

Answer 5

1. Helps to maintain constant pressure by covering transient demands
2. Helps to avoid pump cavitation in reservoir

Question 6

When will Hyd ACMP 1 or 2 activate on ground and in flight?

Answer 6

Ground:
1. Flaps > 0
2. TL set to T/O (stay on for 60 secs)
3. GS > 50 kts (stay on for 60 secs)
In-flight:
1. Eng or EDP failure
2. Flaps > 0

Question 7

What are some of the important systems run on HYD 2?

Answer 7

1. Landing gear
2. Inboard brakes
3. Nose-wheel steering
4. Inboard Ailerons

Question 8

What is the PTU?

Answer 8

The power transfer unit (PTU) is a mechanical pump that uses HYD 1 POWER to provide HYD 2 PRESSURE

Question 9

What is the primary purpose of the PTU?

Answer 9

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

Question 10

When will the PTU automatically activate?

Answer 10

If system meets requirements
1. Flaps > 0
2. EDP 1 not failed
3. Hyd 2 Reservoir Fluid Level above 12%

then PTU comes on automatically
1. ENG 2 Fail or
2. EDP 2 Fail

Question 11

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

Answer 11

Releasing the parking brake commands ACMP 2 to turn on within 6 mins of starting engine 1

Question 12

What is the primary purpose of HYD 3?

Answer 12

To back up the flight controls

Question 13

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

Answer 13

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

Question 14

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

Answer 14

Only ACMP 3A (AC ESS Bus)

Question 15

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

Answer 15

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

Question 16

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

Answer 16

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

Question 17

What kind of hydraulic fluid does the 175 use?

Answer 17

Skydrol Hydraulic Fluid

Question 18

What is the nominal hydraulic pressure?

Answer 18

3000 PSIG

Question 19

Hyd ACMP1B and Hyd ACMP2B is located on what bus?

Answer 19

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

Question 20

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

Answer 20

Depressurizes EDP to facilitate WML start

Question 21

Which bus is Pump 3A on?

Answer 21

Its on AC ESS Bus