Hydraulics

Question 0

What systems use hydraulic power?

Answer 0

Flight controls
Spoilers
Landing gear
Nosewheel steering
Wheel brakes
Thrust reversers

Question 1

How many hydraulic systems are on the airplane?

Answer 1

3 independent systems

HYD 1, HYD 2, and HYD 3

Question 2

Can hydraulic fluid be transferred between systems?

Answer 2

No

Question 3

How many hydraulic pumps are on the airplane?

Answer 3

• 6 total:
2 EDPs (engine driven pumps)
4 ACMPs (AC motor pumps)

Question 4

What are the basic components of the hydraulic systems?

Answer 4

Reservoir
Pumps
Accumulator

Question 5

What is the purpose of the accumulator?

Answer 5

Helps to maintain constant pressure during periods of transient flow demands
Helps to avoid pump cavitation by keeping residual pressure in the hydraulic reservoir.

Question 6

When will ACMP 1 or 2 automatically activate?

Answer 6

• Ground
Flaps >0
Thrust levers set to T/O
Groundspeed >50 kts

• Flight
Engine failure or EDP failure
Flaps > 0

Question 7

What are some important items controlled by HYD 2 system?

Answer 7

Landing gear
Nosewheel steering
Inboard brakes

Question 8

What is the PTU?

Answer 8

Power Transfer Unit

Mechanical pump that uses HYD 1 power to provide HYD 2 pressure

Question 9

What is the primary purpose of the PTU?

Answer 9

To allow landing gear retraction in the event of an engine 2 or EDP 2 failure

Question 10

When will the PTU automatically activate?

Answer 10

During takeoff and landing with flaps >0, if
Engine 2 fails, or
EDP 2 fails

Question 11

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

Answer 11

Releasing the parking brake activates ACMP 2

Question 12

What is the primary purpose of HYD 3 system?

Answer 12

Backup for the Flight controls

Question 13

Why are HYD ACMP 3A and B pump switch positions ON & AUTO respectively?

Answer 13

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

Question 14

What, if any, HYD ACMP will function if the RAT is the only power source?

Answer 14

HYD ACMP 3A only

Question 15

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

Answer 15

HYD 3 accumulator

After 8 seconds the RAT will power ACMP 3A

Question 16

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

Answer 16

No. A flow limiter valve is used to reduce flow and limits pump electrical power draw to prevent a RAT stall

Question 17

Which systems are powered by Hydraulic System 1?

Answer 17

Left outboard elevator PCU, 
Upper rudder PCU,  
multifunction spoiler pairs 3 and 4, 
ground spoiler pair 2, 
left thrust reverser,
outboard brakes and the 
emergency parking brake.

Question 18

Which systems are powered by Hydraulic System 2?

Answer 18

Left and right inboard elevator PCUs,  
multifunction spoiler pair 5, 
ground spoiler pair 1, 
right thrust reverser,
nosewheel stering, 
inboard brakes,
emergency/parking brake and the 
landing gear

Question 19

What systems are powered by Hydraulic System 3?

Answer 19

Left and Right Aileron PCUs
Right Outboard Elevator PCU,
Lower Rudder PCU,