Hydraulics

Question 1

How many hydraulic systems are on the airplane?

Answer 1

3 independent systems

HYD 1, 2 and 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

Six:

• 2 EDPs (engine driven pumps)
• 4 ACMP ( AC motor pumps)

Question 5

What are the basic components of the hydraulic systems?

Answer 5

• reservoir
• pumps
• accumulator

Question 6

What do accumulators do?

Answer 6

Maintain constant pressure and prevent pump cavitation

Question 7

When will ACMP 1 or 2 activate automatically on the ground?

Answer 7

When flaps are > 0 and:

• TL set for takeoff, or
• GS > 50 kts

Question 8

When will ACMP 1 or 2 automatically activate when in the air?

Answer 8

• engine failure or EDP failure

- flaps > 0

Question 9

Name some important systems controlled by HYD 2

Answer 9

• Landing gear
• nose wheel steering
• inboard brakes

Question 10

What is the PTU?

Answer 10

• power transfer unit

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

Question 11

What is the primary purpose of the PTU?

Answer 11

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

Question 12

When will the PTU automatically activate?

Answer 12

When engine 2 or EDP 2 fails and:

• Flaps > 0 or landing gear not up and locked
• EDP 1 not failed
• HYD 2 reservoir quantity > 12%

Question 13

With ACMP 1 and 2 in AUTO how is single engine taxi on engine 1 possible if nosewheel steering is on HYD 2?

Answer 13

• releasing parking brake activates ACMP 2

Question 14

What is the purpose of HYD 3?

Answer 14

Backup for the primary flight controls

Question 15

What are HYD ACMP 3A and B pump switches ON and AUTO respectively?

Answer 15

• HYD ACMP 3A is primary and has no automation

- HYD ACMP is the backup and automatically activates if ACMP 3A fails

Question 16

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

Answer 16

HYD ACMP 3A

Question 17

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

Answer 17

HYD 3 accumulator

- after 8 seconds the RAT will power ACMP 3A

Question 18

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

Answer 18

No. HYD 3 system pressure is unloaded automatically to prevent a RAT stall