Hydraulics Questions

Question 1

How many hydraulic systems are 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 each system?

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 systems?

Answer 5

• Reservoir
• Pumps
• Accumulator

Question 6

What is the purpose of the accumulator?

Answer 6

• Helps to maintain constant pressure by covering transient demands
• Helps to avoid pump cavitation

Question 7

When will ACMP 1 or 2 automatically activate?

Answer 7

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

Question 8

What are some important items controlled by HYD 2 system?

Answer 8

• Landing gear
• Nose wheel 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 landing gear retraction and extension 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 does HYD ACMP 3A pump switch have an ON position and HYD ACMP 3B have an AUTO position?

Answer 14

• 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 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 comes 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 limits pump electrical power draw to prevent a RAT stall