Study Guide Hydraulics

Question 1

How many hydraulic systems on the airplane?

Answer 1

• 3 independent systems

- HYD 1, HYD 2, and HYD 3

Question 2

What systems use hydraulic power?

Answer 2

• Flight controls
• Spoilers
• Landing gear
• Nose wheel steering
• Wheel brakes
• Thrust reversers

Question 3

Can hydraulic fluid be transferred between systems?

Answer 3

No

Question 4

How many hydraulic pumps are on the airplane?

Answer 4

6 total:

• 2 EDPs (Engine driven pumps)
• 4 ACMPs (AC motor pumps)

Question 5

What are the basic components of the hydraulic system?

Answer 5

• Reservoir
• Pumps
• Accumulator

Question 6

What is the purpose of the accumulator?

Answer 6

• Helps maintain constant pressure by covering transient loads
• Helps avoid pump cavitations

Question 7

When will ACMP 1 or 2 automatically activate?

Answer 7

Ground:
  -Flaps >0, and
    -TL set to T/O, or
    -Groundspeed > 50kts
Flight
  -Engine failure or EDP failure
  -Flaps > 0

Question 8

What are some important items controlled by HYD 2 system?

Answer 8

• Landing gear
• Nosewheel steering
• Inboard brakes

Question 9

What is the PTU?

Answer 9

• Power transfer unit

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

Question 10

What is the primary purpose of the PTU?

Answer 10

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

Question 11

When will the PTU automatically activate?

Answer 11

During takeoff and landing with flaps >0, if

• Engine 2 fails, or
• EDP 2 fails

Question 12

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

Answer 12

Releasing the parking brake activates ACMP 2

Question 13

What is the primary purpose of HYD 3 system?

Answer 13

Back up for the flight controls.

Question 14

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

Answer 14

• HYD ACMP 3A pump is primary and has no automation

- HYD ACMP 3B pump is a backup and automatically activates if ACMP 3A fails

Question 15

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

Answer 15

HYD ACMP 3A only

Question 16

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

Answer 16

• HYD 3 accumulator

- After 8 seconds the RAT will power ACMP 3A

Question 17

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

Answer 17

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