Hydraulic

Question 1

How many hydraulic systems are on the aircraft?

Answer 1

Three: Green, Blue, and Yellow

Question 2

Which systems power the flight controls?

Answer 2

All three

Question 3

How is the green system normally pressurized?

Answer 3

By engine 1-driven pump

Question 4

How is the yellow system normally pressurized?

Answer 4

By engine 2-driven pump

Question 5

How is the blue system normally pressurized?

Answer 5

By an electric pump

Question 6

Can the yellow system be pressurized without engine 2?

Answer 6

Yes — via electric pump or hand pump (cargo door)

Question 7

Can the blue system be activated on the ground with no engines running?

Answer 7

Yes — by selecting BLUE PUMP to AUTO with external power or APU on and pressing the BLUE PUMP OVRD pb in the avionics bay

Question 8

What happens when PTU is operating?

Answer 8

Power Transfer Unit uses pressure from one system to drive a pump to pressurize the other — no fluid is transferred

Question 9

When does the PTU automatically operate?

Answer 9

After both engines are running and pressure differential >500 psi between green and yellow systems

Question 10

What would inhibit PTU from running?

Answer 10

Parking brake on, first engine only, cargo door operation

Question 11

What does a PTU fault light indicate?

Answer 11

Automatic operation inhibited or pump overheated

Question 12

What does a reservoir fault light indicate?

Answer 12

Low air pressure, low fluid quantity, or high temperature

Question 13

What does a pump fault light indicate?

Answer 13

Low pressure (and electric/eng pump selector is ON)

Question 14

If electrical power is lost, which hydraulic system is available?

Answer 14

Blue — via RAT deployment

Question 15

What does the RAT supply?

Answer 15

Blue hydraulic pressure and emergency electrical power

Question 16

What powers the nose wheel steering?

Answer 16

Yellow system (green alternate on some aircraft)

Question 17

How can nose wheel steering be regained after complete hydraulic loss?

Answer 17

Only if yellow pressure is restored (via engine or hand pump + accumulator)

Question 18

What is the only hydraulic system that can be pressurized manually on the ground?

Answer 18

Yellow — via hand pump for cargo door operation

Question 19

What happens if yellow and green systems both fail?

Answer 19

Loss of landing gear, brakes, steering (brake accumulator may retain pressure briefly)